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rfc:rfc5046

Network Working Group M. Ko Request for Comments: 5046 IBM Corporation Category: Standards Track M. Chadalapaka

                                               Hewlett-Packard Company
                                                            J. Hufferd
                                                         Brocade, Inc.
                                                              U. Elzur
                                                               H. Shah
                                                             P. Thaler
                                                  Broadcom Corporation
                                                          October 2007
    Internet Small Computer System Interface (iSCSI) Extensions
               for Remote Direct Memory Access (RDMA)

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Abstract

 Internet Small Computer System Interface (iSCSI) Extensions for
 Remote Direct Memory Access (RDMA) provides the RDMA data transfer
 capability to iSCSI by layering iSCSI on top of an RDMA-Capable
 Protocol, such as the iWARP protocol suite.  An RDMA-Capable Protocol
 provides RDMA Read and Write services, which enable data to be
 transferred directly into SCSI I/O Buffers without intermediate data
 copies.  This document describes the extensions to the iSCSI protocol
 to support RDMA services as provided by an RDMA-Capable Protocol,
 such as the iWARP protocol suite.

Ko, et al. Standards Track [Page 1] RFC 5046 iSER Specification October 2007

Table of Contents

 1. Introduction ....................................................5
    1.1. Motivation .................................................5
    1.2. Architectural Goals ........................................6
    1.3. Protocol Overview ..........................................7
    1.4. RDMA Services and iSER .....................................8
         1.4.1. STag ................................................8
         1.4.2. Send ................................................9
         1.4.3. RDMA Write ..........................................9
         1.4.4. RDMA Read ...........................................9
    1.5. SCSI Read Overview ........................................10
    1.6. SCSI Write Overview .......................................10
    1.7. iSCSI/iSER Layering .......................................10
 2. Definitions and Acronyms .......................................11
    2.1. Definitions ...............................................11
    2.2. Acronyms ..................................................17
    2.3. Conventions ...............................................19
 3. Upper Layer Interface Requirements .............................19
    3.1. Operational Primitives Offered by iSER ....................20
         3.1.1. Send_Control .......................................20
         3.1.2. Put_Data ...........................................20
         3.1.3. Get_Data ...........................................21
         3.1.4. Allocate_Connection_Resources ......................21
         3.1.5. Deallocate_Connection_Resources ....................22
         3.1.6. Enable_Datamover ...................................22
         3.1.7. Connection_Terminate ...............................22
         3.1.8. Notice_Key_Values ..................................23
         3.1.9. Deallocate_Task_Resources ..........................23
    3.2. Operational Primitives Used by iSER .......................23
         3.2.1. Control_Notify .....................................24
         3.2.2. Data_Completion_Notify .............................24
         3.2.3. Data_ACK_Notify ....................................24
         3.2.4. Connection_Terminate_Notify ........................25
    3.3. iSCSI Protocol Usage Requirements .........................25
 4. Lower Layer Interface Requirements .............................26
    4.1. Interactions with the RCaP Layer ..........................26
    4.2. Interactions with the Transport Layer .....................27
 5. Connection Setup and Termination ...............................27
    5.1. iSCSI/iSER Connection Setup ...............................27
         5.1.1. Initiator Behavior .................................29
         5.1.2. Target Behavior ....................................30
         5.1.3. iSER Hello Exchange ................................32
    5.2. iSCSI/iSER Connection Termination .........................33
         5.2.1. Normal Connection Termination at the Initiator .....33
         5.2.2. Normal Connection Termination at the Target ........34
         5.2.3. Termination without Logout Request/Response PDUs ...34

Ko, et al. Standards Track [Page 2] RFC 5046 iSER Specification October 2007

 6. Login/Text Operational Keys ....................................35
    6.1. HeaderDigest and DataDigest ...............................35
    6.2. MaxRecvDataSegmentLength ..................................36
    6.3. RDMAExtensions ............................................36
    6.4. TargetRecvDataSegmentLength ...............................37
    6.5. InitiatorRecvDataSegmentLength ............................38
    6.6. OFMarker and IFMarker .....................................38
    6.7. MaxOutstandingUnexpectedPDUs ..............................38
 7. iSCSI PDU Considerations .......................................39
    7.1. iSCSI Data-Type PDU .......................................39
    7.2. iSCSI Control-Type PDU ....................................40
    7.3. iSCSI PDUs ................................................40
         7.3.1. SCSI Command .......................................40
         7.3.2. SCSI Response ......................................42
         7.3.3. Task Management Function Request/Response ..........44
         7.3.4. SCSI Data-Out ......................................45
         7.3.5. SCSI Data-In .......................................46
         7.3.6. Ready to Transfer (R2T) ............................48
         7.3.7. Asynchronous Message ...............................50
         7.3.8. Text Request and Text Response .....................50
         7.3.9. Login Request and Login Response ...................50
         7.3.10. Logout Request and Logout Response ................51
         7.3.11. SNACK Request .....................................51
         7.3.12. Reject ............................................51
         7.3.13. NOP-Out and NOP-In ................................51
 8. Flow Control and STag Management ...............................52
    8.1. Flow Control for RDMA Send Message Types ..................52
         8.1.1. Flow Control for Control-Type PDUs from the
                Initiator ..........................................52
         8.1.2. Flow Control for Control-Type PDUs from the
                Target .............................................55
    8.2. Flow Control for RDMA Read Resources ......................56
    8.3. STag Management ...........................................56
         8.3.1. Allocation of STags ................................57
         8.3.2. Invalidation of STags ..............................57
 9. iSER Control and Data Transfer .................................58
    9.1. iSER Header Format ........................................58
    9.2. iSER Header Format for the iSCSI Control-Type PDU .........59
    9.3. iSER Header Format for the iSER Hello Message .............60
    9.4. iSER Header Format for the iSER HelloReply Message ........61
    9.5. SCSI Data Transfer Operations .............................62
         9.5.1. SCSI Write Operation ...............................62
         9.5.2. SCSI Read Operation ................................63
         9.5.3. Bidirectional Operation ............................64
 10. iSER Error Handling and Recovery ..............................64
    10.1. Error Handling ...........................................64
         10.1.1. Errors in the Transport Layer .....................64
         10.1.2. Errors in the RCaP Layer ..........................65

Ko, et al. Standards Track [Page 3] RFC 5046 iSER Specification October 2007

         10.1.3. Errors in the iSER Layer ..........................66
         10.1.4. Errors in the iSCSI Layer .........................67
    10.2. Error Recovery ...........................................69
         10.2.1. PDU Recovery ......................................69
         10.2.2. Connection Recovery ...............................70
 11. Security Considerations .......................................71
 12. References ....................................................71
    12.1. Normative References .....................................71
    12.2. Informative References ...................................72
 Appendix A. iWARP Message Format for iSER .........................73
    A.1. iWARP Message Format for iSER Hello Message ...............73
    A.2. iWARP Message Format for iSER HelloReply Message ..........74
    A.3. iWARP Message Format for SCSI Read Command PDU ............75
    A.4. iWARP Message Format for SCSI Read Data ...................76
    A.5. iWARP Message Format for SCSI Write Command PDU ...........77
    A.6. iWARP Message Format for RDMA Read Request ................78
    A.7. iWARP Message Format for Solicited SCSI Write Data ........79
    A.8. iWARP Message Format for SCSI Response PDU ................80
 Appendix B. Architectural Discussion of iSER over InfiniBand ......81
    B.1. The Host Side of the iSCSI and iSER Connections
         in InfiniBand .............................................81
    B.2. The Storage Side of the iSCSI and iSER Mixed
         Network Environment .......................................82
    B.3. Discovery Processes for an InfiniBand Host ................82
    B.4. IBTA Connection Specifications ............................83
 Acknowledgments ...................................................83

Table of Figures

 Figure 1. Example of iSCSI/iSER Layering in Full Feature Phase ....11
 Figure 2. iSER Header Format ......................................58
 Figure 3. iSER Header Format for iSCSI Control-Type PDU ...........59
 Figure 4. iSER Header Format for iSER Hello Message ...............60
 Figure 5. iSER Header Format for iSER HelloReply Message ..........61
 Figure 6. SendSE Message containing an iSER Hello Message .........72
 Figure 7. SendSE Message containing an iSER HelloReply Message ....74
 Figure 8. SendSE Message containing a SCSI Read Command PDU .......75
 Figure 9. RDMA Write Message containing SCSI Read Data ............76
 Figure 10. SendSE Message containing a SCSI Write Command PDU .....77
 Figure 11. RDMA Read Request Message ..............................78
 Figure 12. RDMA Read Response Message containing SCSI Write Data ..79
 Figure 13. SendInvSE Message containing SCSI Response PDU .........80
 Figure 14. iSCSI and iSER on IB ...................................81
 Figure 15. Storage Controller with TCP, iWARP, and IB Connections .82

Ko, et al. Standards Track [Page 4] RFC 5046 iSER Specification October 2007

1. Introduction

1.1. Motivation

 The iSCSI protocol [RFC3720] is a mapping of the SCSI Architecture
 Model (see [SAM2]) over the TCP protocol.  SCSI commands are carried
 by iSCSI requests, and SCSI responses and status are carried by iSCSI
 responses.  Other iSCSI protocol exchanges and SCSI data are also
 transported in iSCSI Protocol Data Units (PDUs).
 Out-of-order TCP segments in the Traditional iSCSI model have to be
 stored and reassembled before the iSCSI protocol layer within an end
 node can place the data in the iSCSI buffers.  This reassembly is
 required because not every TCP segment is likely to contain an iSCSI
 header to enable its placement, and TCP itself does not have a
 built-in mechanism for signaling Upper Level Protocol (ULP) message
 boundaries to aid placement of out-of-order segments.  This TCP
 reassembly at high network speeds is quite counter-productive for the
 following reasons: wasted memory bandwidth in data copying, the need
 for reassembly memory, wasted CPU cycles in data copying, and the
 general store-and-forward latency from an application perspective.
 TCP reassembly was recognized as a serious issue in [RFC3720], and
 the notion of a "sync and steering layer" was introduced that is
 optional to implement and use.  One specific sync and steering
 mechanism, called "markers", was defined in [RFC3720], which provides
 an application-level way of framing iSCSI Protocol Data Units (PDUs)
 within the TCP data stream even when the TCP segments are not yet
 reassembled to be in-order.
 With these defined techniques in [RFC3720], a Network Interface
 Controller customized for iSCSI (SNIC) could offload the TCP/IP
 processing and support direct data placement, but most iSCSI
 implementations do not support iSCSI "markers", making SNIC marker-
 based direct data placement unusable in practice.
 The iWARP protocol stack provides direct data placement functionality
 that is usable in practice.  In addition, there is interest in using
 iSCSI with other Remote Direct Memory Access (RDMA) protocol stacks
 that support direct data placement, such as the one provided by
 InfiniBand.  The generic term RDMA-Capable Protocol (RCaP) is used to
 refer to the RDMA functionality provided by such protocol stacks.
 With the availability of RDMA-Capable Controllers within a host
 system, which does not have SNICs, it is appropriate for iSCSI to be
 able to exploit the direct data placement function of the RDMA-
 Capable Controller like other applications.

Ko, et al. Standards Track [Page 5] RFC 5046 iSER Specification October 2007

 iSCSI Extensions for RDMA (iSER) is designed precisely to take
 advantage of generic RDMA technologies -- iSER's goal is to permit
 iSCSI to employ direct data placement and RDMA capabilities using a
 generic RDMA-Capable Controller.  In summary, the iSCSI/iSER protocol
 stack is designed to enable scaling to high speeds by relying on a
 generic data placement process and RDMA technologies and products,
 which enable direct data placement of both in-order and out-of-order
 data.
 This document describes iSER as a protocol extension to iSCSI, both
 for convenience of description and because it is true in a very
 strict protocol sense.  However, note that iSER is in reality
 extending the connectivity of the iSCSI protocol defined in
 [RFC3720], and the name iSER reflects this reality.
 When the iSCSI protocol as defined in [RFC3720] (i.e., without the
 iSER enhancements) is intended in the rest of the document, the term
 "Traditional iSCSI" is used to make the intention clear.

1.2. Architectural Goals

 This section summarizes the architectural goals that guided the
 design of iSER.
 1. Provide an RDMA data transfer model for iSCSI that enables direct
    in-order or out-of-order data placement of SCSI data into pre-
    allocated SCSI buffers while maintaining in-order data delivery.
 2. Not require any major changes to the SCSI Architecture Model
    [SAM2] and SCSI command set standards.
 3. Utilize existing iSCSI infrastructure (sometimes referred to as
    "iSCSI ecosystem") including but not limited to MIB,
    bootstrapping, negotiation, naming and discovery, and security.
 4. Require a session to operate in the Traditional iSCSI data
    transfer mode if iSER is not supported by either the initiator or
    the target (i.e., not require iSCSI Full Feature Phase
    interoperability between an end node operating in Traditional
    iSCSI mode, and an end node operating in iSER-assisted mode).
 5. Allow initiator and target implementations to utilize generic
    RDMA-Capable Controllers such as RDMA-enabled Network Interface
    Controllers (RNICs), or to implement iSCSI and iSER in software
    (not require iSCSI- or iSER-specific assists in the RCaP
    implementation or RDMA-Capable Controller).

Ko, et al. Standards Track [Page 6] RFC 5046 iSER Specification October 2007

 6. Require full and only generic RCaP functionality at both the
    initiator and the target.
 7. Implement a lightweight Datamover protocol for iSCSI with minimal
    state maintenance.

1.3. Protocol Overview

 Consistent with the architectural goals stated in Section 2.2, the
 iSER protocol does not require changes in the iSCSI ecosystem or any
 related SCSI specifications.  The iSER protocol defines the mapping
 of iSCSI PDUs to RCaP Messages in such a way that it is entirely
 feasible to realize iSCSI/iSER implementations that are based on
 generic RDMA-Capable Controllers.  The iSER protocol layer requires
 minimal state maintenance to assist an iSCSI Full Feature Phase
 connection, besides being oblivious to the notion of an iSCSI
 session.  The crucial protocol aspects of iSER may be summarized
 thus:
 1. iSER-assisted mode is negotiated during the iSCSI login for each
    session, and an entire iSCSI session can only operate in one mode
    (i.e., a connection in a session cannot operate in iSER-assisted
    mode if a different connection of the same session is already in
    Full Feature Phase in the Traditional iSCSI mode).
 2. Once in iSER-assisted mode, all iSCSI interactions on that
    connection use RCaP Messages.
 3. A Send Message Type is used for carrying an iSCSI control-type PDU
    preceded by an iSER header.  See Section 7.2 for more details on
    iSCSI control-type PDUs.
 4. RDMA Write, RDMA Read Request, and RDMA Read Response Messages are
    used for carrying control and all data information associated with
    the iSCSI data-type PDUs.  See Section 7.1 for more details on
    iSCSI data-type PDUs.
 5. Target drives all data transfer (with the exception of iSCSI
    unsolicited data) for SCSI writes and SCSI reads, by issuing RDMA
    Read Requests and RDMA Writes, respectively.
 6. RCaP is responsible for ensuring data integrity.  (For example,
    iWARP includes a CRC-enhanced framing layer called Marker PDU
    Aligned Framing for TCP (MPA) on top of TCP; and for InfiniBand,
    the CRCs are included in the Reliable Connection mode).  For this
    reason, iSCSI header and data digests are negotiated to "None" for
    iSCSI/iSER sessions.

Ko, et al. Standards Track [Page 7] RFC 5046 iSER Specification October 2007

 7. The iSCSI error recovery hierarchy defined in [RFC3720] is fully
    supported by iSER.  (However, see Section 7.3.11 on the handling
    of SNACK Request PDUs.)
 8. iSER requires no changes to iSCSI authentication, security, and
    text mode negotiation mechanisms.
 Note that Traditional iSCSI implementations may have to be adapted to
 employ iSER.  It is expected that the adaptation when required is
 likely to be centered around the upper layer interface requirements
 of iSER (Section 3).

1.4. RDMA Services and iSER

 iSER is designed to work with software and/or hardware protocol
 stacks providing the protocol services defined in RCaP documents such
 as [RDMAP], [IB], etc.  The following subsections describe the key
 protocol elements of RCaP services that iSER relies on.

1.4.1. STag

 A Steering Tag (STag) is the identifier of an I/O Buffer unique to an
 RDMA-Capable Controller that the iSER layer Advertises to the remote
 iSCSI/iSER node in order to complete a SCSI I/O.
 In iSER, Advertisement is the act of informing the target by the
 initiator that an I/O Buffer is available at the initiator for RDMA
 Read or RDMA Write access by the target.  The initiator Advertises
 the I/O Buffer by including the STag in the header of an iSER Message
 containing the SCSI Command PDU to the target.  The base Tagged
 Offset is not explicitly specified, but the target must always assume
 it as zero.  The buffer length is as specified in the SCSI Command
 PDU.
 The iSER layer at the initiator Advertises the STag for the I/O
 Buffer of each SCSI I/O to the iSER layer at the target in the iSER
 header of the Send with Solicited Event (SendSE) Message containing
 the SCSI Command PDU, unless the I/O can be completely satisfied by
 unsolicited data alone.
 The iSER layer at the target provides the STag for the I/O Buffer
 that is the Data Sink of an RDMA Read Operation (Section 2.4.4) to
 the RCaP layer on the initiator node -- i.e., this is completely
 transparent to the iSER layer at the initiator.
 The iSER protocol is defined so that the Advertised STag is
 automatically invalidated upon a normal completion of the associated
 task.  This automatic invalidation is realized via the Send with

Ko, et al. Standards Track [Page 8] RFC 5046 iSER Specification October 2007

 Solicited Event and Invalidate (SendInvSE) Message carrying the SCSI
 Response PDU.  There are two exceptions to this automatic
 invalidation -- bidirectional commands, and abnormal completion of a
 command.  The iSER layer at the initiator is required to explicitly
 invalidate the STag in these cases, in addition to sanity checking
 the automatic invalidation even when that does happen.

1.4.2. Send

 Send is the RDMA Operation that is not addressed to an Advertised
 buffer by the sending side, and thus uses Untagged buffers on the
 receiving side.
 The iSER layer at the initiator uses the Send Operation to transmit
 any iSCSI control-type PDU to the target.  As an example, the
 initiator uses Send Operations to transfer iSER Messages containing
 SCSI Command PDUs to the iSER layer at the target.
 An iSER layer at the target uses the Send Operation to transmit any
 iSCSI control-type PDU to the initiator.  As an example, the target
 uses Send Operations to transfer iSER Messages containing SCSI
 Response PDUs to the iSER layer at the initiator.

1.4.3. RDMA Write

 RDMA Write is the RDMA Operation that is used to place data into an
 Advertised buffer on the receiving side.  The sending side addresses
 the Message using an STag and a Tagged Offset that are valid on the
 Data Sink.
 The iSER layer at the target uses the RDMA Write Operation to
 transfer the contents of a local I/O Buffer to an Advertised I/O
 Buffer at the initiator.  The iSER layer at the target uses the RDMA
 Write to transfer whole or part of the data required to complete a
 SCSI read command.
 The iSER layer at the initiator does not employ RDMA Writes.

1.4.4. RDMA Read

 RDMA Read is the RDMA Operation that is used to retrieve data from an
 Advertised buffer on a remote node.  The sending side of the RDMA
 Read Request addresses the Message using an STag and a Tagged Offset
 that are valid on the Data Source in addition to providing a valid
 local STag and Tagged Offset that identify the Data Sink.
 The iSER layer at the target uses the RDMA Read Operation to transfer
 the contents of an Advertised I/O Buffer at the initiator to a local

Ko, et al. Standards Track [Page 9] RFC 5046 iSER Specification October 2007

 I/O Buffer at the target.  The iSER layer at the target uses the RDMA
 Read to fetch whole or part of the data required to complete a SCSI
 write command.
 The iSER layer at the initiator does not employ RDMA Reads.

1.5. SCSI Read Overview

 The iSER layer at the initiator receives the SCSI Command PDU from
 the iSCSI layer.  The iSER layer at the initiator generates an STag
 for the I/O Buffer of the SCSI Read and Advertises the buffer by
 including the STag as part of the iSER header for the PDU.  The iSER
 Message is transferred to the target using a SendSE Message.
 The iSER layer at the target uses one or more RDMA Writes to transfer
 the data required to complete the SCSI Read.
 The iSER layer at the target uses a SendInvSE Message to transfer the
 SCSI Response PDU back to the iSER layer at the initiator.  The iSER
 layer at the initiator notifies the iSCSI layer of the availability
 of the SCSI Response PDU.

1.6. SCSI Write Overview

 The iSER layer at the initiator receives the SCSI Command PDU from
 the iSCSI layer.  If solicited data transfer is involved, the iSER
 layer at the initiator generates an STag for the I/O Buffer of the
 SCSI Write and Advertises the buffer by including the STag as part of
 the iSER header for the PDU.  The iSER Message is transferred to the
 target using a SendSE Message.
 The iSER layer at the initiator may optionally send one or more non-
 immediate unsolicited data PDUs to the target using Send Message
 Types.
 If solicited data transfer is involved, the iSER layer at the target
 uses one or more RDMA Reads to transfer the data required to complete
 the SCSI Write.
 The iSER layer at the target uses a SendInvSE Message to transfer the
 SCSI Response PDU back to the iSER layer at the initiator.  The iSER
 layer at the initiator notifies the iSCSI layer of the availability
 of the SCSI Response PDU.

1.7. iSCSI/iSER Layering

 iSCSI Extensions for RDMA (iSER) is layered between the iSCSI layer
 and the RCaP layer.  Note that the RCaP layer may be composed of one

Ko, et al. Standards Track [Page 10] RFC 5046 iSER Specification October 2007

 or more distinct protocol layers depending on the specifics of the
 RCaP.  Figure 1 shows an example of the relationship between SCSI,
 iSCSI, iSER, and the different RCaP layers.  For TCP, the RCaP is
 iWARP.  For InfiniBand, the RCaP is the Reliable Connected Transport
 Service.  Note that the iSCSI layer as described here supports the
 RDMA Extensions as used in iSER.
               +-------------------------------------+
               |              SCSI                   |
               +-------------------------------------+
               |              iSCSI                  |
    DI ------> +-------------------------------------+
               |              iSER                   |
               +---------+--------------+------------+
               |  RDMAP  |              |            |
               +---------+  InfiniBand  |            |
               |   DDP   |   Reliable   |   Other    |
               +---------+  Connected   |   RDMA-    |
               |   MPA   |  Transport   |  Capable   |
               +---------+   Service    |  Protocol  |
               |   TCP   |              |            |
               +---------+--------------+------------+
               |         |  InfiniBand  |   Other    |
               |    IP   |   Network    |  Network   |
               |         |    Layer     |   Layer    |
               +---------+--------------+------------+
 Figure 1.  Example of iSCSI/iSER Layering in Full Feature Phase

2. Definitions and Acronyms

2.1. Definitions

 Advertisement (Advertised, Advertise, Advertisements, Advertises) -
    The act of informing a remote iSER layer that a local node's
    buffer is available to it.  A Node makes a buffer available for
    incoming RDMA Read Request Message or incoming RDMA Write Message
    access by informing the remote iSER layer of the Tagged Buffer
    identifiers (STag, TO, and buffer length).  Note that this
    Advertisement of Tagged Buffer information is the responsibility
    of the iSER layer on either end and is not defined by the RDMA-
    Capable Protocol.  A typical method would be for the iSER layer to
    embed the Tagged Buffer's STag, TO, and buffer length in a Send
    Message destined for the remote iSER layer.
 Completion (Completed, Complete, Completes) - Completion is defined
    as the process by the RDMA-Capable Protocol layer to inform the

Ko, et al. Standards Track [Page 11] RFC 5046 iSER Specification October 2007

    iSER layer, that a particular RDMA Operation has performed all
    functions specified for the RDMA Operation.
 Connection - A connection is a logical circuit between the initiator
    and the target, e.g., a TCP connection.  Communication between the
    initiator and the target occurs over one or more connections.  The
    connections carry control messages, SCSI commands, parameters, and
    data within iSCSI Protocol Data Units (iSCSI PDUs).
 Connection Handle - An information element that identifies the
    particular iSCSI connection and is unique for a given iSCSI-iSER
    pair.  Every invocation of an Operational Primitive is qualified
    with the Connection Handle.
 Data Sink - The peer receiving a data payload.  Note that the Data
    Sink can be required to both send and receive RCaP Messages to
    transfer a data payload.
 Data Source - The peer sending a data payload.  Note that the Data
    Source can be required to both send and receive RCaP Messages to
    transfer a data payload.
 Datamover Interface (DI) - The interface between the iSCSI layer and
    the Datamover layer as described in [DA].
 Datamover Layer - A layer that is directly below the iSCSI layer and
    above the underlying transport layers.  This layer exposes and
    uses a set of transport independent Operational Primitives for the
    communication between the iSCSI layer and itself.  The Datamover
    layer, operating in conjunction with the transport layers, moves
    the control and data information on the iSCSI connection.  In this
    specification, the iSER layer is the Datamover layer.
 Datamover Protocol - A Datamover protocol is the wire-protocol that
    is defined to realize the Datamover layer functionality.  In this
    specification, the iSER protocol is the Datamover protocol.
 Event - An indication provided by the RDMA-Capable Protocol layer to
    the iSER layer to indicate a Completion or other condition
    requiring immediate attention.
 Inbound RDMA Read Queue Depth (IRD) - The maximum number of incoming
    outstanding RDMA Read Requests that the RDMA-Capable Controller
    can handle on a particular RCaP Stream at the Data Source.  For
    some RDMA-Capable Protocol layers, the term "IRD" may be known by
    a different name.  For example, for InfiniBand, the equivalent for
    IRD is the Responder Resources.

Ko, et al. Standards Track [Page 12] RFC 5046 iSER Specification October 2007

 Invalidate STag - A mechanism used to prevent the Remote Peer from
    reusing a previous explicitly Advertised STag, until the iSER
    layer at the local node makes it available through a subsequent
    explicit Advertisement.
 I/O Buffer - A buffer that is used in a SCSI Read or Write operation
    so SCSI data may be sent from or received into that buffer.
 iSCSI - The iSCSI protocol as defined in [RFC3720] is a mapping of
    the SCSI Architecture Model of SAM-2 over TCP.
 iSCSI control-type PDU - Any iSCSI PDU that is not an iSCSI data-
    type PDU and also not a SCSI Data-out PDU carrying solicited data
    is defined as an iSCSI control-type PDU.  Specifically, it is to
    be noted that SCSI Data-out PDUs for unsolicited data are defined
    as iSCSI control-type PDUs.
 iSCSI data-type PDU - An iSCSI data-type PDU is defined as an iSCSI
    PDU that causes data transfer, transparent to the remote iSCSI
    layer, to take place between the peer iSCSI nodes on a Full
    Feature Phase iSCSI connection.  An iSCSI data-type PDU, when
    requested for transmission by the sender iSCSI layer, results in
    the associated data transfer without the participation of the
    remote iSCSI layer, i.e. the PDU itself is not delivered as-is to
    the remote iSCSI layer.  The following iSCSI PDUs constitute the
    set of iSCSI data-type PDUs - SCSI Data-In PDU and R2T PDU.
 iSCSI Layer - A layer in the protocol stack implementation within an
    end node that implements the iSCSI protocol and interfaces with
    the iSER layer via the Datamover Interface.
 iSCSI PDU (iSCSI Protocol Data Unit) - The iSCSI layer at the
    initiator and the iSCSI layer at the target divide their
    communications into messages.  The term "iSCSI protocol data unit"
    (iSCSI PDU) is used for these messages.
 iSCSI/iSER Connection - An iSER-assisted iSCSI connection.
 iSCSI/iSER Session - An iSER-assisted iSCSI session.
 iSCSI-iSER Pair - The iSCSI layer and the underlying iSER layer.
 iSER - iSCSI Extensions for RDMA, the protocol defined in this
    document.
 iSER-assisted - A term generally used to describe the operation of
    iSCSI when the iSER functionality is also enabled below the iSCSI
    layer for the specific iSCSI/iSER connection in question.

Ko, et al. Standards Track [Page 13] RFC 5046 iSER Specification October 2007

 iSER-IRD - This variable represents the maximum number of incoming
    outstanding RDMA Read Requests that the iSER layer at the
    initiator declares on a particular RCaP Stream.
 iSER-ORD - This variable represents the maximum number of outstanding
    RDMA Read Requests that the iSER layer can initiate on a
    particular RCaP Stream.  This variable is maintained only by the
    iSER layer at the target.
 iSER Layer - The layer that implements the iSCSI Extensions for RDMA
    (iSER) protocol.
 iWARP - A suite of wire protocols comprising of [RDMAP], [DDP], and
    [MPA] when layered above [TCP].  [RDMAP] and [DDP] may be layered
    above SCTP or other transport protocols.
 Local Mapping - A task state record maintained by the iSER layer that
    associates the Initiator Task Tag to the local STag(s).  The
    specifics of the record structure are implementation dependent.
 Local Peer - The implementation of the RDMA-Capable Protocol on the
    local end of the connection.  Used to refer to the local entity
    when describing protocol exchanges or other interactions between
    two Nodes.
 Node - A computing device attached to one or more links of a network.
    A Node in this context does not refer to a specific application or
    protocol instantiation running on the computer.  A Node may
    consist of one or more RDMA-Capable Controllers installed in a
    host computer.
 Operational Primitive - An Operational Primitive is an abstract
    functional interface procedure that requests that another layer
    perform a specific action on the requestor's behalf or notifies
    the other layer of some event.  The Datamover Interface between an
    iSCSI layer and a Datamover layer within an iSCSI end node uses a
    set of Operational Primitives to define the functional interface
    between the two layers.  Note that not every invocation of an
    Operational Primitive may elicit a response from the requested
    layer.  A full discussion of the Operational Primitive types and
    request-response semantics available to iSCSI and iSER can be
    found in [DA].
 Outbound RDMA Read Queue Depth (ORD) - The maximum number of
    outstanding RDMA Read Requests that the RDMA-Capable Controller
    can initiate on a particular RCaP Stream at the Data Sink.  For

Ko, et al. Standards Track [Page 14] RFC 5046 iSER Specification October 2007

    some RDMA-Capable Protocol layer, the term "ORD" may be known by a
    different name.  For example, for InfiniBand, the equivalent for
    ORD is the Initiator Depth.
 Phase-Collapse - Refers to the optimization in iSCSI where the SCSI
    status is transferred along with the final SCSI Data-in PDU from a
    target.  See Section 3.2 in [RFC3720].
 RCaP Message - One or more packets of the network layer comprising a
    single RDMA Operation or a part of an RDMA Read Operation of the
    RDMA-Capable Protocol.  For iWARP, an RCaP Message is known as an
    RDMAP Message.
 RCaP Stream - A single bidirectional association between the peer
    RDMA-Capable Protocol layers on two Nodes over a single
    transport-level stream.  For iWARP, an RCaP Stream is known as an
    RDMAP Stream, and the association is created when the connection
    transitions to iSER-assisted mode following a successful Login
    Phase during which iSER support is negotiated.
 RDMA-Capable Protocol (RCaP) - The protocol or protocol suite that
    provides a reliable RDMA transport functionality, e.g., iWARP,
    InfiniBand, etc.
 RDMA-Capable Controller - A network I/O adapter or embedded
    controller with RDMA functionality.  For example, for iWARP, this
    could be an RNIC, and for InfiniBand, this could be a HCA (Host
    Channel Adapter) or TCA (Target Channel Adapter).
 RDMA-enabled Network Interface Controller (RNIC) - A network I/O
    adapter or embedded controller with iWARP functionality.
 RDMA Operation - A sequence of RCaP Messages, including control
    Messages, to transfer data from a Data Source to a Data Sink.  The
    following RDMA Operations are defined - RDMA Write Operation, RDMA
    Read Operation, Send Operation, Send with Invalidate Operation,
    Send with Solicited Event Operation, Send with Solicited Event and
    Invalidate Operation, and Terminate Operation.
 RDMA Protocol (RDMAP) - A wire protocol that supports RDMA Operations
    to transfer ULP data between a Local Peer and the Remote Peer as
    described in [RDMAP].
 RDMA Read Operation - An RDMA Operation used by the Data Sink to
    transfer the contents of a Data Source buffer from the Remote Peer
    to a Data Sink buffer at the Local Peer.  An RDMA Read operation
    consists of a single RDMA Read Request Message and a single RDMA
    Read Response Message.

Ko, et al. Standards Track [Page 15] RFC 5046 iSER Specification October 2007

 RDMA Read Request - An RCaP Message used by the Data Sink to request
    that the Data Source transfer the contents of a buffer.  The RDMA
    Read Request Message describes both the Data Source and the Data
    Sink buffers.
 RDMA Read Response - An RCaP Message used by the Data Source to
    transfer the contents of a buffer to the Data Sink, in response to
    an RDMA Read Request.  The RDMA Read Response Message only
    describes the Data Sink buffer.
 RDMA Write Operation - An RDMA Operation used by the Data Source to
    transfer the contents of a Data Source buffer from the Local Peer
    to a Data Sink buffer at the Remote Peer.  The RDMA Write Message
    only describes the Data Sink buffer.
 Remote Direct Memory Access (RDMA) - A method of accessing memory on
    a remote system in which the local system specifies the remote
    location of the data to be transferred.  Employing an RDMA-
    Capable Controller in the remote system allows the access to take
    place without interrupting the processing of the CPU(s) on the
    system.
 Remote Mapping - A task state record maintained by the iSER layer
    that associates the Initiator Task Tag to the Advertised STag(s).
    The specifics of the record structure are implementation
    dependent.
 Remote Peer - The implementation of the RDMA-Capable Protocol on the
    opposite end of the connection.  Used to refer to the remote
    entity when describing protocol exchanges or other interactions
    between two Nodes.
 SCSI Layer - This layer builds/receives SCSI CDBs (Command Descriptor
    Blocks) and sends/receives them with the remaining command execute
    [SAM2] parameters to/from the iSCSI layer.
 Send - An RDMA Operation that transfers the contents of a Buffer from
    the Local Peer to a Buffer at the Remote Peer.
 Send Message Type - A Send Message, Send with Invalidate Message,
    Send with Solicited Event Message, or Send with Solicited Event
    and Invalidate Message.
 SendInvSE Message - A Send with Solicited Event and Invalidate
    Message.
 SendSE Message - A Send with Solicited Event Message.

Ko, et al. Standards Track [Page 16] RFC 5046 iSER Specification October 2007

 Sequence Number (SN) - DataSN for a SCSI Data-in PDU and R2TSN for an
    R2T PDU.  The semantics for both types of sequence numbers are as
    defined in [RFC3720].
 Session, iSCSI Session - The group of connections that link an
    initiator SCSI port with a target SCSI port form an iSCSI session
    (equivalent to a SCSI I-T nexus).  Connections can be added to and
    removed from a session even while the I-T nexus is intact.  Across
    all connections within a session, an initiator sees one and the
    same target.
 Solicited Event (SE) - A facility by which an RDMA Operation sender
    may cause an Event to be generated at the recipient, if the
    recipient is configured to generate such an Event, when a Send
    with Solicited Event or Send with Solicited Event and Invalidate
    Message is received.
 Steering Tag (STag) - An identifier of a Tagged Buffer on a Node
    (Local or Remote) as defined in [RDMAP] and [DDP].  For other
    RDMA-Capable Protocols, the Steering Tag may be known by different
    names but will be herein referred to as STags.  For example, for
    InfiniBand, a Remote STag is known as an R-Key, and a local STag
    is known as an L-Key, and both will be considered STags.
 Tagged Buffer - A buffer that is explicitly Advertised to the iSER
    layer at the remote node through the exchange of an STag, Tagged
    Offset, and length.
 Tagged Offset (TO) - The offset within a Tagged Buffer.
 Traditional iSCSI - Refers to the iSCSI protocol as defined in
    [RFC3720] (i.e. without the iSER enhancements).
 Untagged Buffer - A buffer that is not explicitly Advertised to the
    iSER layer at the remode node.

2.2. Acronyms

    Acronym        Definition
    --------------------------------------------------------------
    AHS            Additional Header Segment
    BHS            Basic Header Segment
    CO             Connection Only
    CRC            Cyclic Redundancy Check

Ko, et al. Standards Track [Page 17] RFC 5046 iSER Specification October 2007

    DDP            Direct Data Placement Protocol
    DI             Datamover Interface
    HCA            Host Channel Adapter
    IANA           Internet Assigned Numbers Authority
    IB             InfiniBand
    IETF           Internet Engineering Task Force
    I/O            Input - Output
    IO             Initialize Only
    IP             Internet Protocol
    IPoIB          IP over InfiniBand
    IPsec          Internet Protocol Security
    iSER           iSCSI Extensions for RDMA
    ITT            Initiator Task Tag
    LO             Leading Only
    MPA            Marker PDU Aligned Framing for TCP
    NOP            No Operation
    NSG            Next Stage (during the iSCSI Login Phase)
    OS             Operating System
    PDU            Protocol Data Unit
    R2T            Ready To Transfer
    R2TSN          Ready To Transfer Sequence Number
    RDMA           Remote Direct Memory Access
    RDMAP          Remote Direct Memory Access Protocol
    RFC            Request For Comments

Ko, et al. Standards Track [Page 18] RFC 5046 iSER Specification October 2007

    RNIC           RDMA-enabled Network Interface Controller
    SAM2           SCSI Architecture Model - 2
    SCSI           Small Computer Systems Interface
    SNACK          Selective Negative Acknowledgment - also
                   Sequence Number Acknowledgement for data
    STag           Steering Tag
    SW             Session Wide
    TCA            Target Channel Adapter
    TCP            Transmission Control Protocol
    TMF            Task Management Function
    TTT            Target Transfer Tag
    TO             Tagged Offset
    ULP            Upper Level Protocol

2.3. Conventions

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in [RFC2119].

3. Upper Layer Interface Requirements

 This section discusses the upper layer interface requirements in the
 form of an abstract model of the required interactions between the
 iSCSI layer and the iSER layer.  The abstract model used here is
 derived from the architectural model described in [DA].  [DA] also
 provides a functional overview of the interactions between the iSCSI
 layer and the Datamover layer as intended by the Datamover
 Architecture.
 The interface requirements are specified by Operational Primitives.
 An Operational Primitive is an abstract functional interface
 procedure between the iSCSI layer and the iSER layer that requests
 one layer to perform a specific action on behalf of the other layer
 or notifies the other layer of some event.  Whenever an Operational
 Primitive in invoked, the Connection_Handle qualifier is used to
 identify a particular iSCSI connection.  For some Operational

Ko, et al. Standards Track [Page 19] RFC 5046 iSER Specification October 2007

 Primitives, a Data_Descriptor is used to identify the iSCSI/SCSI data
 buffer associated with the requested or completed operation.
 The abstract model and the Operational Primitives defined in this
 section facilitate the description of the iSER protocol.  In the rest
 of the iSER specification, the compliance statements related to the
 use of these Operational Primitives are only for the purpose of the
 required interactions between the iSCSI layer and the iSER layer.
 Note that the compliance statements related to the Operational
 Primitives in the rest of this specification only mandate functional
 equivalence on implementations, but do not put any requirements on
 the implementation specifics of the interface between the iSCSI layer
 and the iSER layer.
 Each Operational Primitive is invoked with a set of qualifiers that
 specify the information context for performing the specific action
 being requested of the Operational Primitive.  While the qualifiers
 are required, the method of realizing the qualifiers (e.g., by
 passing synchronously with invocation, or by retrieving from task
 context, or by retrieving from shared memory, etc.) is implementation
 dependent.

3.1. Operational Primitives Offered by iSER

 The iSER protocol layer MUST support the following Operational
 Primitives to be used by the iSCSI protocol layer.

3.1.1. Send_Control

    Input qualifiers:  Connection_Handle, BHS and AHS (if any) of the
    iSCSI PDU, PDU-specific qualifiers
    Return results:  Not specified
 This is used by the iSCSI layers at the initiator and the target to
 request the outbound transfer of an iSCSI control-type PDU (see
 Section 7.2).  Qualifiers that only apply for a particular control-
 type PDU are known as PDU-specific qualifiers, e.g.,
 ImmediateDataSize for a SCSI write command.  For details on PDU-
 specific qualifiers, see Section 7.3.  The iSCSI layer can only
 invoke the Send_Control Operational Primitive when the connection is
 in iSER-assisted mode.

3.1.2. Put_Data

    Input qualifiers:  Connection_Handle, content of a SCSI Data-in
    PDU header, Data_Descriptor, Notify_Enable

Ko, et al. Standards Track [Page 20] RFC 5046 iSER Specification October 2007

    Return results:  Not specified
 This is used by the iSCSI layer at the target to request the outbound
 transfer of data for a SCSI Data-in PDU from the buffer identified by
 the Data_Descriptor qualifier.  The iSCSI layer can only invoke the
 Put_Data Operational Primitive when the connection is in iSER-
 assisted mode.
 The Notify_Enable qualifier is used to indicate to the iSER layer
 whether or not it should generate an eventual local completion
 notification to the iSCSI layer.  See Section 3.2.2 on
 Data_Completion_Notify for details.

3.1.3. Get_Data

    Input qualifiers:  Connection_Handle, content of an R2T PDU,
    Data_Descriptor, Notify_Enable
    Return results:  Not specified
 This is used by the iSCSI layer at the target to request the inbound
 transfer of solicited data requested by an R2T PDU into the buffer
 identified by the Data_Descriptor qualifier.  The iSCSI layer can
 only invoke the Get_Data Operational Primitive when the connection is
 in iSER-assisted mode.
 The Notify_Enable qualifier is used to indicate to the iSER layer
 whether or not it should generate the eventual local completion
 notification to the iSCSI layer.  See Section 3.2.2 on
 Data_Completion_Notify for details.

3.1.4. Allocate_Connection_Resources

    Input qualifiers:  Connection_Handle, Resource_Descriptor
    (optional)
    Return results:  Status
 This is used by the iSCSI layers at the initiator and the target to
 request the allocation of all connection resources necessary to
 support RCaP for an operational iSCSI/iSER connection.  The iSCSI
 layer may optionally specify the implementation-specific resource
 requirements for the iSCSI connection using the Resource_Descriptor
 qualifier.
 A return result of Status=success means that the invocation
 succeeded, and a return result of Status=failure means that the
 invocation failed.  If the invocation is for a Connection_Handle for

Ko, et al. Standards Track [Page 21] RFC 5046 iSER Specification October 2007

 which an earlier invocation succeeded, the request will be ignored by
 the iSER layer and the result of Status=success will be returned.
 Only one Allocate_Connection_Resources Operational Primitive
 invocation can be outstanding for a given Connection_Handle at any
 time.

3.1.5. Deallocate_Connection_Resources

    Input qualifiers:  Connection_Handle
    Return results:  Not specified
 This is used by the iSCSI layers at the initiator and the target to
 request the deallocation of all connection resources that were
 allocated earlier as a result of a successful invocation of the
 Allocate_Connection_Resources Operational Primitive.

3.1.6. Enable_Datamover

    Input qualifiers:  Connection_Handle,
    Transport_Connection_Descriptor, Final Login_Response_PDU
    (optional)
    Return results:  Not specified
 This is used by the iSCSI layers at the initiator and the target to
 request that a specified iSCSI connection be transitioned to iSER-
 assisted mode.  The Transport_Connection_Descriptor qualifier is used
 to identify the specific connection associated with the
 Connection_Handle.  The iSCSI layer can only invoke the
 Enable_Datamover Operational Primitive when there is a corresponding
 prior resource allocation.
 The Final_Login_Response_PDU input qualifier is applicable only for a
 target, and contains the final Login Response PDU that concludes the
 iSCSI Login Phase.  If the underlying transport is TCP, the final
 Login Response PDU must be sent as a byte stream as expected by the
 iSCSI layer at the initiator.  When this qualifier is used, the iSER
 layer at the target MUST transmit this final Login Response PDU
 before transitioning to iSER-assisted mode.

3.1.7. Connection_Terminate

    Input qualifiers:  Connection_Handle
    Return results:  Not specified

Ko, et al. Standards Track [Page 22] RFC 5046 iSER Specification October 2007

 This is used by the iSCSI layers at the initiator and the target to
 request that a specified iSCSI/iSER connection be terminated and all
 associated connection and task resources be freed.  When this
 Operational Primitive invocation returns to the iSCSI layer, the
 iSCSI layer may assume full ownership of all iSCSI-level resources,
 e.g., I/O Buffers, associated with the connection.

3.1.8. Notice_Key_Values

    Input qualifiers:  Connection_Handle, number of keys, list of
    Key-Value pairs
    Return results:  Not specified
 This is used by the iSCSI layers at the initiator and the target to
 request that the iSER layer take note of the specified Key-Value
 pairs that were negotiated by the iSCSI peers for the connection.

3.1.9. Deallocate_Task_Resources

    Input qualifiers:  Connection_Handle, ITT
    Return results:  Not specified
 This is used by the iSCSI layers at the initiator and the target to
 request the deallocation of all RCaP-specific resources allocated by
 the iSER layer for the task identified by the ITT qualifier.  The
 iSER layer may require a certain number of RCaP-specific resources
 associated with the ITT for each new iSCSI task.  In the normal
 course of execution, these task-level resources in the iSER layer are
 assumed to be transparently allocated on each task initiation and
 deallocated on the conclusion of each task as appropriate.  In
 exception scenarios where the task does not conclude with a SCSI
 Response PDU, the iSER layer needs to be notified of the individual
 task terminations to aid its task-level resource management.  This
 Operational Primitive is used for this purpose, and is not needed
 when a SCSI Response PDU normally concludes a task.  Note that RCaP-
 specific task resources are deallocated by the iSER layer when a SCSI
 Response PDU normally concludes a task, even if the SCSI status was
 not success.

3.2. Operational Primitives Used by iSER

 The iSER layer MUST use the following Operational Primitives offered
 by the iSCSI protocol layer when the connection is in iSER-assisted
 mode.

Ko, et al. Standards Track [Page 23] RFC 5046 iSER Specification October 2007

3.2.1. Control_Notify

    Input qualifiers:  Connection_Handle, an iSCSI control-type PDU
    Return results:  Not specified
 This is used by the iSER layers at the initiator and the target to
 notify the iSCSI layer of the availability of an inbound iSCSI
 control-type PDU.  A PDU is described as "available" to the iSCSI
 layer when the iSER layer notifies the iSCSI layer of the reception
 of that inbound PDU, along with an implementation-specific indication
 as to where the received PDU is.

3.2.2. Data_Completion_Notify

    Input qualifiers:  Connection_Handle, ITT, SN
    Return results:  Not specified
 This is used by the iSER layer to notify the iSCSI layer of the
 completion of outbound data transfer that was requested by the iSCSI
 layer only if the invocation of the Put_Data Operational Primitive
 (see Section 3.1.2) was qualified with Notify_Enable set.  SN refers
 to the DataSN associated with the SCSI Data-in PDU.
 This is used by the iSER layer to notify the iSCSI layer of the
 completion of inbound data transfer that was requested by the iSCSI
 layer only if the invocation of the Get_Data Operational Primitive
 (see Section 3.1.3) was qualified with Notify_Enable set.  SN refers
 to the R2TSN associated with the R2T PDU.

3.2.3. Data_ACK_Notify

    Input qualifier:  Connection_Handle, ITT, DataSN
    Return results:  Not specified
 This is used by the iSER layer at the target to notify the iSCSI
 layer of the arrival of the data acknowledgement (as defined in
 [RFC3720]) requested earlier by the iSCSI layer for the outbound data
 transfer via an invocation of the Put_Data Operational Primitive
 where the A-bit in the SCSI Data-in PDU is set to 1.  See Section
 7.3.5.  DataSN refers to the expected DataSN of the next SCSI Data-in
 PDU, which immediately follows the SCSI Data-in PDU with the A-bit
 set to which this notification corresponds, with semantics as defined
 in [RFC3720].

Ko, et al. Standards Track [Page 24] RFC 5046 iSER Specification October 2007

3.2.4. Connection_Terminate_Notify

    Input qualifiers:  Connection_Handle
    Return results:  Not specified
 This is used by the iSER layers at the initiator and the target to
 notify the iSCSI layer of the unsolicited termination or failure of
 an iSCSI/iSER connection.  The iSER layer MUST deallocate the
 connection and task resources associated with the terminated
 connection before the invocation of this Operational Primitive.  Note
 that the Connection_Terminate_Notify Operational Primitive is not
 invoked when the termination of the connection is earlier requested
 by the local iSCSI layer.

3.3. iSCSI Protocol Usage Requirements

 To operate in an iSER-assisted mode, the iSCSI layers at both the
 initiator and the target MUST negotiate the RDMAExtensions key (see
 Section 6.3) to "Yes" on the leading connection.  If the
 RDMAExtensions key is not negotiated to "Yes", then iSER-assisted
 mode MUST NOT be used.  If the RDMAExtensions key is negotiated to
 "Yes" but the invocation of the Allocate_Connection_Resources
 Operational Primitive to the iSER layer fails, the iSCSI layer MUST
 fail the iSCSI Login process or terminate the connection as
 appropriate.  See Section 10.1.3.1 for details.
 If the RDMAExtensions key is negotiated to "Yes", the iSCSI layer
 MUST satisfy the following protocol usage requirements from the iSER
 protocol:
 1.  The iSCSI layer at the initiator MUST set ExpDataSN to 0 in Task
     Management Function Requests for Task Allegiance Reassignment for
     read/bidirectional commands, so as to cause the target to send
     all unacknowledged read data.
 2.  The iSCSI layer at the target MUST always return the SCSI status
     in a separate SCSI Response PDU for read commands, i.e., there
     MUST NOT be a "phase collapse" in concluding a SCSI read command.
 3.  The iSCSI layers at both the initiator and the target MUST
     support the keys as defined in Section 6 on Login/Text
     Operational Keys.  If used as specified, these keys MUST NOT be
     answered with NotUnderstood, and the semantics as defined MUST be
     followed for each iSER-assisted connection.
 4.  The iSCSI layer at the initiator MUST NOT issue SNACKs for PDUs.

Ko, et al. Standards Track [Page 25] RFC 5046 iSER Specification October 2007

4. Lower Layer Interface Requirements

4.1. Interactions with the RCaP Layer

 The iSER protocol layer is layered on top of an RCaP layer (see
 Figure 1) and the following are the key features that are assumed to
 be supported by any RCaP layer:
  • The RCaP layer supports all basic RDMA operations, including RDMA

Write Operation, RDMA Read Operation, Send Operation, Send with

    Invalidate Operation, Send with Solicited Event Operation, Send
    with Solicited Event and Invalidate Operation, and Terminate
    Operation.
  • The RCaP layer provides reliable, in-order message delivery and

direct data placement.

  • When the iSER layer initiates an RDMA Read Operation following an

RDMA Write Operation on one RCaP Stream, the RDMA Read Response

    Message processing on the remote node will be started only after
    the preceding RDMA Write Message payload is placed in the memory
    of the remote node.
  • The RCaP layer encapsulates a single iSER Message into a single

RCaP Message on the Data Source side. The RCaP layer decapsulates

    the iSER Message before delivering it to the iSER layer on the
    Data Sink side.
  • When the iSER layer provides the STag to be remotely invalidated

to the RCaP layer for a SendInvSE Message, the RCaP layer uses

    this STag as the STag to be invalidated in the SendInvSE Message.
  • The RCaP layer uses the STag and Tagged Offset provided by the

iSER layer for the RDMA Write and RDMA Read Request Messages.

  • When the RCaP layer delivers the content of an RDMA Send Message

Type to the iSER layer, the RCaP layer provides the length of the

    RDMA Send message.  This ensures that the iSER layer does not have
    to carry a length field in the iSER header.
  • When the RCaP layer delivers the SendSE or SendInvSE Message to

the iSER layer, it notifies the iSER layer with the mechanism

    provided on that interface.
  • When the RCaP layer delivers a SendInvSE Message to the iSER

layer, it passes the value of the STag that was invalidated.

Ko, et al. Standards Track [Page 26] RFC 5046 iSER Specification October 2007

  • The RCaP layer propagates all status and error indications to the

iSER layer.

  • For a transport layer that operates in byte stream mode such as

TCP, the RCaP implementation supports the enabling of the RDMA

    mode after connection establishment and the exchange of Login
    parameters in byte stream mode.  For a transport layer that
    provides message delivery capability such as [IB], the RCaP
    implementation supports the use of the messaging capability by the
    iSCSI layer directly for the Login Phase after connection
    establishment before enabling iSER-assisted mode.
  • Whenever the iSER layer terminates the RCaP Stream, the RCaP layer

terminates the associated connection.

4.2. Interactions with the Transport Layer

 The iSER layer does not directly setup the transport layer connection
 (e.g., TCP, or [IB]).  During connection setup, the iSCSI layer is
 responsible for setting up the connection.  If the login is
 successful, the iSCSI layer invokes the Enable_Datamover Operational
 Primitive to request the iSER layer to transition to the iSER-
 assisted mode for that iSCSI connection.  See Section 5.1 on
 iSCSI/iSER connection setup.  After transitioning to iSER-assisted
 mode, the RCaP layer and the underlying transport layer are
 responsible for maintaining the connection and reporting to the iSER
 layer any connection failures.

5. Connection Setup and Termination

5.1. iSCSI/iSER Connection Setup

 During connection setup, the iSCSI layer at the initiator is
 responsible for establishing a connection with the target.  After the
 connection is established, the iSCSI layers at the initiator and the
 target enter the Login Phase using the same rules as outlined in
 [RFC3720].  Transition to iSER-assisted mode occurs when the
 connection transitions into the iSCSI Full Feature Phase following a
 successful login negotiation between the initiator and the target in
 which iSER-assisted mode is negotiated and the connection resources
 necessary to support RCaP have been allocated at both the initiator
 and the target.  The same connection MUST be used for both the iSCSI
 Login Phase and the subsequent iSER-assisted Full Feature Phase.
 iSER-assisted mode MUST be enabled only if it is negotiated on the
 leading connection during the LoginOperationalNegotiation stage of
 the iSCSI Login Phase.  iSER-assisted mode is negotiated using the
 RDMAExtensions=<boolean-value> key.  Both the initiator and the

Ko, et al. Standards Track [Page 27] RFC 5046 iSER Specification October 2007

 target MUST exchange the RDMAExtensions key with the value set to
 "Yes" to enable iSER-assisted mode.  If both the initiator and the
 target fail to negotiate the RDMAExtensions key set to "Yes", then
 the connection MUST continue with the login semantics as defined in
 [RFC3720].  If the RDMAExtensions key is not negotiated to Yes, then
 for some RCaP implementation (such as [IB]), the connection may need
 to be re-established in TCP capable mode.  (For InfiniBand this will
 require an [IPoIB] type connection.)
 iSER-assisted mode is defined for a Normal session only and the
 RDMAExtensions key MUST NOT be negotiated for a Discovery session.
 Discovery sessions are always conducted using the transport layer as
 described in [RFC3720].
 An iSER enabled node is not required to initiate the RDMAExtensions
 key exchange if its preference is for the Traditional iSCSI mode.
 The RDMAExtensions key, if offered, MUST be sent in the first
 available Login Response or Login Request PDU in the
 LoginOperationalNegotiation stage.  This is due to the fact that the
 value of some login parameters might depend on whether iSER-assisted
 mode is enabled.
 iSER-assisted mode is a session-wide attribute.  If both the
 initiator and the target negotiate RDMAExtensions="Yes" on the
 leading connection of a session, then all subsequent connections of
 the same session MUST enable iSER-assisted mode without having to
 exchange an RDMAExtensions key during the iSCSI Login Phase.
 Conversely, if both the initiator and the target fail to negotiate
 RDMAExtensions to "Yes" on the leading connection of a session, then
 the RDMAExtensions key MUST NOT be negotiated further on any
 additional subsequent connection of the session.
 When the RDMAExtensions key is negotiated to "Yes", the HeaderDigest
 and the DataDigest keys MUST be negotiated to "None" on all
 iSCSI/iSER connections participating in that iSCSI session.  This is
 because, for an iSCSI/iSER connection, RCaP is responsible for
 providing error detection that is at least as good as a 32-bit CRC
 for all iSER Messages.  Furthermore, all SCSI Read data are sent
 using RDMA Write Messages instead of the SCSI Data-in PDUs, and all
 solicited SCSI write data are sent using RDMA Read Response Messages
 instead of the SCSI Data-out PDUs.  HeaderDigest and DataDigest that
 apply to iSCSI PDUs, would not be appropriate for RDMA Read and RDMA
 Write operations used with iSER.

Ko, et al. Standards Track [Page 28] RFC 5046 iSER Specification October 2007

5.1.1. Initiator Behavior

 If the outcome of the iSCSI negotiation is to enable iSER-assisted
 mode, then on the initiator side, prior to sending the Login Request
 with the T (Transit) bit set to 1 and the NSG (Next Stage) field set
 to FullFeaturePhase, the iSCSI layer MUST request that the iSER layer
 allocate the connection resources necessary to support RCaP by
 invoking the Allocate_Connection_Resources Operational Primitive.
 The connection resources required are defined by implementation and
 are outside the scope of this specification.  The iSCSI layer may
 invoke the Notice_Key_Values Operational Primitive before invoking
 the Allocate_Connection_Resources Operational Primitive to request
 that the iSER layer take note of the negotiated values of the iSCSI
 keys for the connection.  The specific keys to be passed as input
 qualifiers are implementation dependent.  These may include, but are
 not limited to, MaxOutstandingR2T, ErrorRecoveryLevel, etc.
 To minimize the potential for a denial-of service attack, the iSCSI
 layer MUST NOT request that the iSER layer allocate the connection
 resources necessary to support RCaP until the iSCSI layer is
 sufficiently far along in the iSCSI Login Phase that it is reasonably
 certain that the peer side is not an attacker.  In particular, if the
 Login Phase includes a SecurityNegotiation stage, the iSCSI layer
 MUST defer the connection resource allocation (i.e., invoking the
 Allocate_Connection_Resources Operational Primitive) to the
 LoginOperationalNegotiation stage [RFC3720] so that the resource
 allocation occurs after the authentication phase is completed.
 Among the connection resources allocated at the initiator is the
 Inbound RDMA Read Queue Depth (IRD).  As described in Section 9.5.1,
 R2Ts are transformed by the target into RDMA Read operations.  IRD
 limits the maximum number of simultaneously incoming outstanding RDMA
 Read Requests per an RCaP Stream from the target to the initiator.
 The required value of IRD is outside the scope of the iSER
 specification.  The iSER layer at the initiator MUST set IRD to 1 or
 higher if R2Ts are to be used in the connection.  However, the iSER
 layer at the initiator MAY set IRD to 0 based on implementation
 configuration, which indicates that no R2Ts will be used on that
 connection.  Initially, the iSER-IRD value at the initiator SHOULD be
 set to the IRD value at the initiator and MUST NOT be more than the
 IRD value.
 On the other hand, the Outbound RDMA Read Queue Depth (ORD) MAY be
 set to 0, since the iSER layer at the initiator does not issue RDMA
 Read Requests to the target.

Ko, et al. Standards Track [Page 29] RFC 5046 iSER Specification October 2007

 Failure to allocate the requested connection resources locally
 results in a login failure and its handling is described in Section
 10.1.3.1.
 If the iSER layer at the initiator is successful in allocating the
 connection resources necessary to support RCaP, the following events
 MUST occur in the specified sequence:
 1.  The iSER layer MUST return a success status to the iSCSI layer in
     response to the Allocate_Connection_Resources Operational
     Primitive.
 2.  After the target returns the Login Response with the T bit set to
     1 and the NSG field set to FullFeaturePhase, and a status class
     of 0 (Success), the iSCSI layer MUST request that the iSER layer
     transition to iSER-assisted mode by invoking the Enable_Datamover
     Operational Primitive with the following qualifiers.  (See
     Section 10.1.4.6 for the case when the status class is not
     Success.):
     a.  Connection_Handle that identifies the iSCSI connection.
     b.  Transport_Connection_Descriptor that identifies the specific
         transport connection associated with the Connection_Handle.
 3.  If necessary, the iSER layer should enable RCaP and transition
     the connection to iSER-assisted mode.  When the RCaP is iWARP,
     then this step MUST be done.  Not all RCaPs may need it depending
     on the RCaP Stream start-up state.
 4.  The iSER layer MUST send the iSER Hello Message as the first iSER
     Message.  See Section 5.1.3 on iSER Hello Exchange.

5.1.2. Target Behavior

 If the outcome of the iSCSI negotiation is to enable iSER-assisted
 mode, then on the target side, prior to sending the Login Response
 with the T (Transit) bit set to 1 and the NSG (Next Stage) field set
 to FullFeaturePhase, the iSCSI layer MUST request that the iSER layer
 allocate the resources necessary to support RCaP by invoking the
 Allocate_Connection_Resources Operational Primitive.  The connection
 resources required are defined by implementation and are outside the
 scope of this specification.  Optionally, the iSCSI layer may invoke
 the Notice_Key_Values Operational Primitive before invoking the
 Allocate_Connection_Resources Operational Primitive to request that
 the iSER layer take note of the negotiated values of the iSCSI keys
 for the connection.  The specific keys to be passed as input

Ko, et al. Standards Track [Page 30] RFC 5046 iSER Specification October 2007

 qualifiers are implementation dependent.  These may include, but are
 not limited to, MaxOutstandingR2T, ErrorRecoveryLevel, etc.
 To minimize the potential for a denial-of-service attack, the iSCSI
 layer MUST NOT request that the iSER layer allocate the connection
 resources necessary to support RCaP until the iSCSI layer is
 sufficiently far along in the iSCSI Login Phase that it is reasonably
 certain that the peer side is not an attacker.  In particular, if the
 Login Phase includes a SecurityNegotiation stage, the iSCSI layer
 MUST defer the connection resource allocation (i.e., invoking the
 Allocate_Connection_Resources Operational Primitive) to the
 LoginOperationalNegotiation stage [RFC3720] so that the resource
 allocation occurs after the authentication phase is completed.
 Among the connection resources allocated at the target is the
 Outbound RDMA Read Queue Depth (ORD).  As described in Section 9.5.1,
 R2Ts are transformed by the target into RDMA Read operations.  The
 ORD limits the maximum number of simultaneously outstanding RDMA Read
 Requests per RCaP Stream from the target to the initiator.
 Initially, the iSER-ORD value at the target SHOULD be set to the ORD
 value at the target.
 On the other hand, the IRD at the target MAY be set to 0 since the
 iSER layer at the target does not expect RDMA Read Requests to be
 issued by the initiator.
 Failure to allocate the requested connection resources locally
 results in a login failure and its handling is described in Section
 10.1.3.1.
 If the iSER layer at the target is successful in allocating the
 connection resources necessary to support RCaP, the following events
 MUST occur in the specified sequence:
 1.  The iSER layer MUST return a success status to the iSCSI layer in
     response to the Allocate_Connection_Resources Operational
     Primitive.
 2.  The iSCSI layer MUST request that the iSER layer transition to
     iSER-assisted mode by invoking the Enable_Datamover Operational
     Primitive with the following qualifiers:
     a.  Connection_Handle that identifies the iSCSI connection.
     b.  Transport_Connection_Descriptor that identifies the specific
         transport connection associated with the Connection_Handle.

Ko, et al. Standards Track [Page 31] RFC 5046 iSER Specification October 2007

     c.  The final transport layer (e.g., TCP) message containing the
         Login Response with the T bit set to 1 and the NSG field set
         to FullFeaturePhase.
 3.  The iSER layer MUST send the final Login Response PDU in the
     native transport mode to conclude the iSCSI Login Phase.  If the
     underlying transport is TCP, then the iSER layer MUST send the
     final Login Response PDU in byte stream mode.
 4.  After sending the final Login Response PDU, the iSER layer should
     enable RCaP if necessary and transition the connection to iSER-
     assisted mode.  When the RCaP is iWARP, then this step MUST be
     done.  Not all RCaPs may need it depending on the RCaP Stream
     start-up state.
 5.  After receiving the iSER Hello Message from the initiator, the
     iSER layer MUST respond with the iSER HelloReply Message to be
     sent as the first iSER Message.  See Section 5.1.3 on iSER Hello
     Exchange for more details.
 Note: In the above sequence, the operations as described in bullets 3
 and 4 MUST be performed atomically for iWARP connections.  Failure to
 do this may result in race conditions.

5.1.3. iSER Hello Exchange

 After the connection transitions into iSER-assisted mode, the first
 iSER Message sent by the iSER layer at the initiator to the target
 MUST be the iSER Hello Message.  The iSER Hello Message is used by
 the iSER layer at the initiator to declare iSER parameters to the
 target.  See Section 9.3 on iSER Header Format for the iSER Hello
 Message.
 In response to the iSER Hello Message, the iSER layer at the target
 MUST return the iSER HelloReply Message as the first iSER Message
 sent by the target.  The iSER HelloReply Message is used by the iSER
 layer at the target to declare iSER parameters to the initiator.  See
 Section 9.4 on iSER Header Format for the iSER HelloReply Message.
 In the iSER Hello Message, the iSER layer at the initiator declares
 the iSER-IRD value to the target.
 Upon receiving the iSER Hello Message, the iSER layer at the target
 MUST set the iSER-ORD value to the minimum of the iSER-ORD value at
 the target and the iSER-IRD value declared by the initiator.  The
 iSER layer at the target MAY adjust (lower) its ORD value to match
 the iSER-ORD value if the iSER-ORD value is smaller than the ORD
 value at the target in order to free up the unused resources.

Ko, et al. Standards Track [Page 32] RFC 5046 iSER Specification October 2007

 In the iSER HelloReply Message, the iSER layer at the target declares
 the iSER-ORD value to the initiator.
 Upon receiving the iSER HelloReply Message, the iSER layer at the
 initiator MAY adjust (lower) its IRD value to match the iSER-ORD
 value in order to free up the unused resources, if the iSER-ORD value
 declared by the target is smaller than the iSER-IRD value declared by
 the initiator.
 It is an iSER level negotiation failure if the iSER parameters
 declared in the iSER Hello Message by the initiator are unacceptable
 to the target.  This includes the following:
  • The initiator-declared iSER-IRD value is greater than 0 and the

target-declared iSER-ORD value is 0.

  • The initiator-supported and the target-supported iSER protocol

versions do not overlap.

 See Section 10.1.3.2 for the handling of the error situation.

5.2. iSCSI/iSER Connection Termination

5.2.1. Normal Connection Termination at the Initiator

 The iSCSI layer at the initiator terminates an iSCSI/iSER connection
 normally by invoking the Send_Control Operational Primitive qualified
 with the Logout Request PDU.  The iSER layer at the initiator MUST
 use a SendSE Message to send the Logout Request PDU to the target.
 After the iSER layer at the initiator receives the SendSE Message
 containing the Logout Response PDU from the target, it MUST notify
 the iSCSI layer by invoking the Control_Notify Operational Primitive
 qualified with the Logout Response PDU.
 After the iSCSI logout process is complete, the iSCSI layer at the
 target is responsible for closing the iSCSI/iSER connection as
 described in Section 5.2.2.  After the RCaP layer at the initiator
 reports that the connection has been closed, the iSER layer at the
 initiator MUST deallocate all connection and task resources (if any)
 associated with the connection, and invalidate the Local Mapping(s)
 (if any) that associate the ITT(s) used on that connection to the
 local STag(s) before notifying the iSCSI layer by invoking the
 Connection_Terminate_Notify Operational Primitive.

Ko, et al. Standards Track [Page 33] RFC 5046 iSER Specification October 2007

5.2.2. Normal Connection Termination at the Target

 Upon receiving the SendSE Message containing the Logout Request PDU,
 the iSER layer at the target MUST notify the iSCSI layer at the
 target by invoking the Control_Notify Operational Primitive qualified
 with the Logout Request PDU.  The iSCSI layer completes the logout
 process by invoking the Send_Control Operational Primitive qualified
 with the Logout Response PDU.  The iSER layer at the target MUST use
 a SendSE Message to send the Logout Response PDU to the initiator.
 After the iSCSI logout process is complete, the iSCSI layer at the
 target MUST request that the iSER layer at the target terminate the
 RCaP Stream by invoking the Connection_Terminate Operational
 Primitive.
 As part of the termination process, the RCaP layer MUST close the
 connection.  When the RCaP layer notifies the iSER layer after the
 RCaP Stream and the associated connection are terminated, the iSER
 layer MUST deallocate all connection and task resources (if any)
 associated with the connection, and invalidate the Local and Remote
 Mapping(s) (if any) that associate the ITT(s) used on that connection
 to the local STag(s) and the Advertised STag(s) respectively.

5.2.3. Termination without Logout Request/Response PDUs

5.2.3.1. Connection Termination Initiated by the iSCSI Layer

 The Connection_Terminate Operational Primitive MAY be invoked by the
 iSCSI layer to request that the iSER layer terminate the RCaP Stream
 without having previously exchanged the Logout Request and Logout
 Response PDUs between the two iSCSI/iSER nodes.  As part of the
 termination process, the RCaP layer will close the connection.  When
 the RCaP layer notifies the iSER layer after the RCaP Stream and the
 associated connection are terminated, the iSER layer MUST perform the
 following actions.
 If the Connection_Terminate Operational Primitive is invoked by the
 iSCSI layer at the target, then the iSER layer at the target MUST
 deallocate all connection and task resources (if any) associated with
 the connection, and invalidate the Local and Remote Mappings (if any)
 that associate the ITT(s) used on the connection to the local STag(s)
 and the Advertised STag(s), respectively.
 If the Connection_Terminate Operational Primitive is invoked by the
 iSCSI layer at the initiator, then the iSER layer at the initiator
 MUST deallocate all connection and task resources (if any) associated
 with the connection, and invalidate the Local Mapping(s) (if any)
 that associate the ITT(s) used on the connection to the local
 STag(s).

Ko, et al. Standards Track [Page 34] RFC 5046 iSER Specification October 2007

5.2.3.2. Connection Termination Notification to the iSCSI Layer

 If the iSCSI/iSER connection is terminated without the invocation of
 Connection_Terminate from the iSCSI layer, the iSER layer MUST notify
 the iSCSI layer that the iSCSI/iSER connection has been terminated by
 invoking the Connection_Terminate_Notify Operational Primitive.
 Prior to invoking Connection_Terminate_Notify, the iSER layer at the
 target MUST deallocate all connection and task resources (if any)
 associated with the connection, and invalidate the Local and Remote
 Mappings (if any) that associate the ITT(s) used on the connection to
 the local STag(s) and the Advertised STag(s), respectively.
 Prior to invoking Connection_Terminate_Notify, the iSER layer at the
 initiator MUST deallocate all connection and task resources (if any)
 associated with the connection, and invalidate the Local Mappings (if
 any) that associate the ITT(s) used on the connection to the local
 STag(s).
 If the remote iSCSI/iSER node initiated the closing of the connection
 (e.g., by sending a TCP FIN or TCP RST), the iSER layer MUST notify
 the iSCSI layer after the RCaP layer reports that the connection is
 closed by invoking the Connection_Terminate_Notify Operational
 Primitive.
 Another example of a connection termination without a preceding
 logout is when the iSCSI layer at the initiator does an implicit
 logout (connection reinstatement).

6. Login/Text Operational Keys

 Certain iSCSI login/text operational keys have restricted usage in
 iSER, and additional keys are used to support the iSER protocol
 functionality.  All other keys defined in [RFC3720] and not discussed
 in this section may be used on iSCSI/iSER connections with the same
 semantics.

6.1. HeaderDigest and DataDigest

 Irrelevant when: RDMAExtensions=Yes
 Negotiations resulting in RDMAExtensions=Yes for a session implies
 HeaderDigest=None and DataDigest=None for all connections in that
 session and overrides both the default and an explicit setting.

Ko, et al. Standards Track [Page 35] RFC 5046 iSER Specification October 2007

6.2. MaxRecvDataSegmentLength

 For an iSCSI connection belonging to a session in which
 RDMAExtensions=Yes was negotiated on the leading connection of the
 session, MaxRecvDataSegmentLength need not be declared in the Login
 Phase.  Instead, InitiatorRecvDataSegmentLength (as described in
 Section 6.5) and TargetRecvDataSegmentLength (as described in Section
 6.4) keys are negotiated.  The values of the local and remote
 MaxRecvDataSegmentLength are derived from the
 InitiatorRecvDataSegmentLength and TargetRecvDataSegmentLength keys
 even if the MaxRecvDataSegmentLength is declared during the Login
 Phase.
 In the Full Feature Phase, the initiator MUST consider the value of
 its local MaxRecvDataSegmentLength (that it would have declared to
 the target) as having the value of InitiatorRecvDataSegmentLength,
 and the value of the remote MaxRecvDataSegmentLength (that would have
 been declared by the target) as having the value of
 TargetRecvDataSegmentLength.  Similarly, the target MUST consider the
 value of its local MaxRecvDataSegmentLength (that it would have
 declared to the initiator) as having the value of
 TargetRecvDataSegmentLength, and the value of the remote
 MaxRecvDataSegmentLength (that would have been declared by the
 initiator) as having the value of InitiatorRecvDataSegmentLength.
 The MaxRecvDataSegmentLength key is applicable only for iSCSI
 control-type PDUs.

6.3. RDMAExtensions

 Use: LO (leading only)
 Senders: Initiator and Target
 Scope: SW (session-wide)
 RDMAExtensions=<boolean-value>
 Irrelevant when: SessionType=Discovery
 Default is No
 Result function is AND
 This key is used by the initiator and the target to negotiate support
 for iSER-assisted mode.  To enable the use of iSER-assisted mode,
 both the initiator and the target MUST exchange RDMAExtensions=Yes.

Ko, et al. Standards Track [Page 36] RFC 5046 iSER Specification October 2007

 iSER-assisted mode MUST NOT be used if either the initiator or the
 target offers RDMAExtensions=No.
 An iSER-enabled node is not required to initiate the RDMAExtensions
 key exchange if it prefers to operate in the Traditional iSCSI mode.
 However, if the RDMAExtensions key is to be negotiated, an initiator
 MUST offer the key in the first Login Request PDU in the
 LoginOperationalNegotiation stage of the leading connection, and a
 target MUST offer the key in the first Login Response PDU with which
 it is allowed to do so (i.e., the first Login Response PDU issued
 after the first Login Request PDU with the C bit set to 0) in the
 LoginOperationalNegotiation stage of the leading connection.  In
 response to the offered key=value pair of RDMAExtensions=yes, an
 initiator MUST respond in the next Login Request PDU with which it is
 allowed to do so, and a target MUST respond in the next Login
 Response PDU with which it is allowed to do so.
 Negotiating the RDMAExtensions key first enables a node to negotiate
 the optimal value for other keys.  Certain iSCSI keys such as
 MaxBurstLength, MaxOutstandingR2T, ErrorRecoveryLevel, InitialR2T,
 ImmediateData, etc., may be negotiated differently depending on
 whether the connection is in Traditional iSCSI mode or iSER-assisted
 mode.

6.4. TargetRecvDataSegmentLength

 Use: IO (Initialize only)
 Senders: Initiator and Target
 Scope: CO (connection-only)
 Irrelevant when: RDMAExtensions=No
 TargetRecvDataSegmentLength=<numerical-value-512-to-(2**24-1)>
 Default is 8192 bytes
 Result function is minimum
 This key is relevant only for the iSCSI connection of an iSCSI
 session if RDMAExtensions=Yes is negotiated on the leading connection
 of the session.  It is used by the initiator and target to negotiate
 the maximum size of the data segment that an initiator may send to
 the target in an iSCSI control-type PDU in the Full Feature Phase.
 For SCSI Command PDUs and SCSI Data-out PDUs containing non-immediate
 unsolicited data to be sent by the initiator, the initiator MUST send
 all non-Final PDUs with a data segment size of exactly

Ko, et al. Standards Track [Page 37] RFC 5046 iSER Specification October 2007

 TargetRecvDataSegmentLength whenever the PDUs constitute a data
 sequence whose size is larger than TargetRecvDataSegmentLength.

6.5. InitiatorRecvDataSegmentLength

 Use: IO (Initialize only)
 Senders: Initiator and Target
 Scope: CO (connection-only)
 Irrelevant when: RDMAExtensions=No
 InitiatorRecvDataSegmentLength=<numerical-value-512-to-(2**24-1)>
 Default is 8192 bytes
 Result function is minimum
 This key is relevant only for the iSCSI connection of an iSCSI
 session if RDMAExtensions=Yes is negotiated on the leading connection
 of the session.  It is used by the initiator and target to negotiate
 the maximum size of the data segment that a target may send to the
 initiator in an iSCSI control-type PDU in the Full Feature Phase.

6.6. OFMarker and IFMarker

 Irrelevant when: RDMAExtensions=Yes
 Negotiations resulting in RDMAExtensions=Yes for a session implies
 OFMarker=No and IFMarker=No for all connections in that session and
 overrides both the default and an explicit setting.

6.7. MaxOutstandingUnexpectedPDUs

 Use: LO (leading only), Declarative
 Senders: Initiator and Target
 Scope: SW (session-wide)
 Irrelevant when: RDMAExtensions=No
 MaxOutstandingUnexpectedPDUs=<numerical-value-from-2-to-(2**32-1) |
 0>
 Default is 0

Ko, et al. Standards Track [Page 38] RFC 5046 iSER Specification October 2007

 This key is used by the initiator and the target to declare the
 maximum number of outstanding "unexpected" iSCSI control-type PDUs
 that it can receive in the Full Feature Phase.  It is intended to
 allow the receiving side to determine the amount of buffer resources
 needed beyond the normal flow control mechanism available in iSCSI.
 An initiator or target should select a value such that it would not
 impose an unnecessary constraint on the iSCSI layer under normal
 circumstances.  The value of 0 is defined to indicate that the
 declarer has no limit on the maximum number of outstanding
 "unexpected" iSCSI control-type PDUs that it can receive.  See
 Sections 8.1.1 and 8.1.2 for the usage of this key.  Note that iSER
 Hello and HelloReply Messages are not iSCSI control-type PDUs and are
 not affected by this key.

7. iSCSI PDU Considerations

 When a connection is in the iSER-assisted mode, two types of message
 transfers are allowed between the iSCSI layer at the initiator and
 the iSCSI layer at the target.  These are known as the iSCSI data-
 type PDUs and the iSCSI control-type PDUs, and these terms are
 described in the following sections.

7.1. iSCSI Data-Type PDU

 An iSCSI data-type PDU is defined as an iSCSI PDU that causes data
 transfer, transparent to the remote iSCSI layer, to take place
 between the peer iSCSI nodes in the full feature phase of an
 iSCSI/iSER connection.  An iSCSI data-type PDU, when requested for
 transmission by the iSCSI layer in the sending node, results in the
 data being transferred without the participation of the iSCSI layers
 at the sending and the receiving nodes.  This is due to the fact that
 the PDU itself is not delivered as-is to the iSCSI layer in the
 receiving node.  Instead, the data transfer operations are
 transformed into the appropriate RDMA operations that are handled by
 the RDMA-Capable Controller.  The set of iSCSI data-type PDUs
 consists of SCSI Data-in PDUs and R2T PDUs.
 If the invocation of the Operational Primitive by the iSCSI layer to
 request that the iSER layer process an iSCSI data-type PDU is
 qualified with Notify_Enable set, then upon completing the RDMA
 operation, the iSER layer at the target MUST notify the iSCSI layer
 at the target by invoking the Data_Completion_Notify Operational
 Primitive qualified with ITT and SN.  There is no data completion
 notification at the initiator since the RDMA operations are
 completely handled by the RDMA-Capable Controller at the initiator
 and the iSER layer at the initiator is not involved with the data
 transfer associated with iSCSI data-type PDUs.

Ko, et al. Standards Track [Page 39] RFC 5046 iSER Specification October 2007

 If the invocation of the Operational Primitive by the iSCSI layer to
 request that the iSER layer process an iSCSI data-type PDU is
 qualified with Notify_Enable cleared, then upon completing the RDMA
 operation, the iSER layer at the target MUST NOT notify the iSCSI
 layer at the target and MUST NOT invoke the Data_Completion_Notify
 Operational Primitive.
 If an operation associated with an iSCSI data-type PDU fails for any
 reason, the contents of the Data Sink buffers associated with the
 operation are considered indeterminate.

7.2. iSCSI Control-Type PDU

 Any iSCSI PDU that is not an iSCSI data-type PDU and also not a SCSI
 Data-out PDU carrying solicited data is defined as an iSCSI control-
 type PDU.  The iSCSI layer invokes the Send_Control Operational
 Primitive to request that the iSER layer process an iSCSI control-
 type PDU.  iSCSI control-type PDUs are transferred using Send Message
 Types of RCaP.  Specifically, note that SCSI Data-out PDUs carrying
 unsolicited data are defined as iSCSI control-type PDUs.  See Section
 7.3.4 on the treatment of SCSI Data-out PDUs.
 When the iSER layer receives an iSCSI control-type PDU, it MUST
 notify the iSCSI layer by invoking the Control_Notify Operational
 Primitive qualified with the iSCSI control-type PDU.

7.3. iSCSI PDUs

 This section describes the handling of each of the iSCSI PDU types by
 the iSER layer.  The iSCSI layer requests that the iSER layer process
 the iSCSI PDU by invoking the appropriate Operational Primitive.  A
 Connection_Handle MUST qualify each of these invocations.  In
 addition, BHS and the optional AHS of the iSCSI PDU as defined in
 [RFC3720] MUST qualify each of the invocations.  The qualifying
 Connection_Handle, the BHS, and the AHS are not explicitly listed in
 the subsequent sections.

7.3.1. SCSI Command

    Type:  control-type PDU
    PDU-specific qualifiers (for SCSI Write or bidirectional command):
    ImmediateDataSize, UnsolicitedDataSize, DataDescriptorOut
    PDU-specific qualifiers (for SCSI read or bidirectional command):
    DataDescriptorIn

Ko, et al. Standards Track [Page 40] RFC 5046 iSER Specification October 2007

 The iSER layer at the initiator MUST send the SCSI command in a
 SendSE Message to the target.
 For a SCSI Write or bidirectional command, the iSCSI layer at the
 initiator MUST invoke the Send_Control Operational Primitive as
 follows:
  • If there is immediate data to be transferred for the SCSI Write or

bidirectional command, the qualifier ImmediateDataSize MUST be

    used to define the number of bytes of immediate unsolicited data
    to be sent with the Write or bidirectional command, and the
    qualifier DataDescriptorOut MUST be used to define the initiator's
    I/O Buffer containing the SCSI Write data.
  • If there is unsolicited data to be transferred for the SCSI Write

or bidirectional command, the qualifier UnsolicitedDataSize MUST

    be used to define the number of bytes of immediate and non-
    immediate unsolicited data for the command.  The iSCSI layer will
    issue one or more SCSI Data-out PDUs for the non-immediate
    unsolicited data.  See Section 7.3.4 on SCSI Data-out.
  • If there is solicited data to be transferred for the SCSI write or

bidirectional command, as indicated by the Expected Data Transfer

    Length in the SCSI Command PDU exceeding the value of
    UnsolicitedDataSize, the iSER layer at the initiator MUST do the
    following:
       a.  It MUST allocate a Write STag for the I/O Buffer defined by
           the qualifier DataDescriptorOut.  The DataDescriptorOut
           describes the I/O buffer starting with the immediate
           unsolicited data (if any), followed by the non-immediate
           unsolicited data (if any) and solicited data.  This means
           that the BufferOffset for the SCSI Data-out for this
           command is equal to the TO.  This implies that a zero TO
           for this STag points to the beginning of this I/O Buffer.
       b.  It MUST establish a Local Mapping that associates the
           Initiator Task Tag (ITT) to the Write STag.
       c.  It MUST Advertise the Write STag to the target by sending
           it as the Write STag in the iSER header of the iSER Message
           (the payload of the SendSE Message of RCaP) containing the
           SCSI write or bidirectional command PDU.  See Section 9.2
           on iSER Header Format for the iSCSI Control-Type PDU.
 For a SCSI read or bidirectional command, the iSCSI layer at the
 initiator MUST invoke the Send_Control Operational Primitive
 qualified with DataDescriptorIn, which defines the initiator's I/O

Ko, et al. Standards Track [Page 41] RFC 5046 iSER Specification October 2007

 Buffer for receiving the SCSI Read data.  The iSER layer at the
 initiator MUST do the following:
       a.  It MUST allocate a Read STag for the I/O Buffer.
       b.  It MUST establish a Local Mapping that associates the
           Initiator Task Tag (ITT) to the Read STag.
       c.  It MUST Advertise the Read STag to the target by sending it
           as the Read STag in the iSER header of the iSER Message
           (the payload of the SendSE Message of RCaP) containing the
           SCSI read or bidirectional command PDU.  See Section 9.2 on
           iSER Header Format for the iSCSI Control-Type PDU.
 If the amount of unsolicited data to be transferred in a SCSI command
 exceeds TargetRecvDataSegmentLength, then the iSCSI layer at the
 initiator MUST segment the data into multiple iSCSI control-type
 PDUs, with the data segment length in all PDUs generated except the
 last one having exactly the size TargetRecvDataSegmentLength.  The
 data segment length of the last iSCSI control-type PDU carrying the
 unsolicited data can be up to TargetRecvDataSegmentLength.
 When the iSER layer at the target receives the SCSI command, it MUST
 establish a Remote Mapping that associates the ITT to the Advertised
 Write STag and the Read STag if present in the iSER header.  The
 Write STag is used by the iSER layer at the target in handling the
 data transfer associated with the R2T PDU(s) as described in Section
 7.3.6.  The Read STag is used in handling the SCSI Data-in PDU(s)
 from the iSCSI layer at the target as described in Section 7.3.5.

7.3.2. SCSI Response

    Type:  control-type PDU
    PDU-specific qualifiers:  DataDescriptorStatus
 The iSCSI layer at the target MUST invoke the Send_Control
 Operational Primitive qualified with DataDescriptorStatus, which
 defines the buffer containing the sense and response information.
 The iSCSI layer at the target MUST always return the SCSI status for
 a SCSI command in a separate SCSI Response PDU.  "Phase collapse" for
 transferring SCSI status in a SCSI Data-in PDU MUST NOT be used.  The
 iSER layer at the target sends the SCSI Response PDU according to the
 following rules:
  • If no STags are Advertised by the initiator in the iSER Message

containing the SCSI command PDU, then the iSER layer at the target

    MUST send a SendSE Message containing the SCSI Response PDU.

Ko, et al. Standards Track [Page 42] RFC 5046 iSER Specification October 2007

  • If the initiator Advertised a Read STag in the iSER Message

containing the SCSI Command PDU, then the iSER layer at the target

    MUST send a SendInvSE Message containing the SCSI Response PDU.
    The header of the SendInvSE Message MUST carry the Read STag to be
    invalidated at the initiator.
  • If the initiator Advertised only the Write STag in the iSER

Message containing the SCSI Command PDU, then the iSER layer at

    the target MUST send a SendInvSE Message containing the SCSI
    Response PDU.  The header of the SendInvSE Message MUST carry the
    Write STag to be invalidated at the initiator.
 When the iSCSI layer at the target invokes the Send_Control
 Operational Primitive to send the SCSI Response PDU, the iSER layer
 at the target MUST invalidate the Remote Mapping that associates the
 ITT to the Advertised STag(s) before transferring the SCSI Response
 PDU to the initiator.
 Upon receiving the SendInvSE Message containing the SCSI Response PDU
 from the target, the RCaP layer at the initiator will invalidate the
 STag specified in the header.  The iSER layer at the initiator MUST
 ensure that the correct STag is invalidated.  If both the Read and
 the Write STags are Advertised earlier by the initiator, then the
 iSER layer at the initiator MUST explicitly invalidate the Write STag
 upon receiving the SendInvSE Message because the header of the
 SendInvSE Message can only carry one STag (in this case, the Read
 STag) to be invalidated.
 The iSER layer at the initiator MUST ensure the invalidation of the
 STag(s) used in a command before notifying the iSCSI layer at the
 initiator by invoking the Control_Notify Operational Primitive
 qualified with the SCSI Response.  This precludes the possibility of
 using the STag(s) after the completion of the command, thereby
 causing data corruption.
 When the iSER layer at the initiator receives the SendSE or the
 SendInvSE Message containing the SCSI Response PDU, it SHOULD
 invalidate the Local Mapping that associates the ITT to the local
 STag(s).  The iSER layer MUST ensure that all local STag(s)
 associated with the ITT are invalidated before notifying the iSCSI
 layer of the SCSI Response PDU by invoking the Control_Notify
 Operational Primitive qualified with the SCSI Response PDU.

Ko, et al. Standards Track [Page 43] RFC 5046 iSER Specification October 2007

7.3.3. Task Management Function Request/Response

    Type:  control-type PDU
    PDU-specific qualifiers (for TMF Request):  DataDescriptorOut,
    DataDescriptorIn
 The iSER layer MUST use a SendSE Message to send the Task Management
 Function Request/Response PDU.
 For the Task Management Function Request with the TASK REASSIGN
 function, the iSER layer at the initiator MUST do the following:
  • It MUST use the ITT as specified in the Referenced Task Tag from

the Task Management Function Request PDU to locate the existing

    STag(s), if any, in the Local Mapping(s) that associates the ITT
    to the local STag(s).
  • It MUST invalidate the existing STag(s), if any, and the Local

Mapping(s) that associates the ITT to the local STag(s).

  • It MUST allocate a Read STag for the I/O Buffer as defined by the

qualifier DataDescriptorIn if the Send_Control Operational

    Primitive invocation is qualified with DataDescriptorIn.
  • It MUST allocate a Write STag for the I/O Buffer as defined by the

qualifier DataDescriptorOut if the Send_Control Operational

    Primitive invocation is qualified with DataDescriptorOut.
  • If STags are allocated, it MUST establish a new Local Mapping(s)

that associate the ITT to the allocated STag(s).

  • It MUST Advertise the STags, if allocated, to the target in the

iSER header of the SendSE Message carrying the iSCSI PDU, as

    described in Section 9.2.
 For the Task Management Function Request with the TASK REASSIGN
 function for a SCSI read or bidirectional command, the iSCSI layer at
 the initiator MUST set ExpDataSN to 0 since the data transfer and
 acknowledgements happen transparently to the iSCSI layer at the
 initiator.  This provides the flexibility to the iSCSI layer at the
 target to request transmission of only the unacknowledged data as
 specified in [RFC3720].
 When the iSER layer at the target receives the Task Management
 Function Request with the TASK REASSIGN function, it MUST do the
 following:

Ko, et al. Standards Track [Page 44] RFC 5046 iSER Specification October 2007

  • It MUST use the ITT as specified in the Referenced Task Tag from

the Task Management Function Request PDU to locate the mappings

    that associate the ITT to the Advertised STag(s) and the local
    STag(s), if any.
  • It MUST invalidate the local STag(s), if any, associated with the

ITT.

  • It MUST replace the Advertised STag(s) in the Remote Mapping that

associates the ITT to the Advertised STag(s) with the Write STag

    and the Read STag if present in the iSER header.  The Write STag
    is used in the handling of the R2T PDU(s) from the iSCSI layer at
    the target as described in Section 7.3.6.  The Read STag is used
    in the handling of the SCSI Data-in PDU(s) from the iSCSI layer at
    the target as described in Section 7.3.5.

7.3.4. SCSI Data-Out

    Type:  control-type PDU
    PDU-specific qualifiers:  DataDescriptorOut
 The iSCSI layer at the initiator MUST invoke the Send_Control
 Operational Primitive qualified with DataDescriptorOut, which defines
 the initiator's I/O Buffer containing unsolicited SCSI Write data.
 If the amount of unsolicited data to be transferred as SCSI Data-out
 exceeds TargetRecvDataSegmentLength, then the iSCSI layer at the
 initiator MUST segment the data into multiple iSCSI control-type
 PDUs, with the DataSegmentLength having the value of
 TargetRecvDataSegmentLength in all PDUs generated except the last
 one.  The DataSegmentLength of the last iSCSI control-type PDU
 carrying the unsolicited data can be up to
 TargetRecvDataSegmentLength.  The iSCSI layer at the target MUST
 perform the reassembly function for the unsolicited data.
 For unsolicited data, if the F bit is set to 0 in a SCSI Data-out
 PDU, the iSER layer at the initiator MUST use a Send Message to send
 the SCSI Data-out PDU.  If the F bit is set to 1, the iSER layer at
 the initiator MUST use a SendSE Message to send the SCSI Data-out
 PDU.
 Note that for solicited data, the SCSI Data-out PDUs are not used
 since R2T PDUs are not delivered to the iSCSI layer at the initiator;
 instead, R2T PDUs are transformed by the iSER layer at the target
 into RDMA Read operations.  (See Section 7.3.6.)

Ko, et al. Standards Track [Page 45] RFC 5046 iSER Specification October 2007

7.3.5. SCSI Data-In

    Type:  data-type PDU
    PDU-specific qualifiers:  DataDescriptorIn
 When the iSCSI layer at the target is ready to return the SCSI Read
 data to the initiator, it MUST invoke the Put_Data Operational
 Primitive qualified with DataDescriptorIn, which defines the SCSI
 Data-in buffer.  See Section 7.1 on the general requirement on the
 handling of iSCSI data-type PDUs.  SCSI Data-in PDU(s) are used in
 SCSI Read data transfer as described in Section 9.5.2.
 The iSER layer at the target MUST do the following for each
 invocation of the Put_Data Operational Primitive:
 1.  It MUST use the ITT in the SCSI Data-in PDU to locate the remote
     Read STag in the Remote Mapping that associates the ITT to
     Advertised STag(s).  The Remote Mapping was established earlier
     by the iSER layer at the target when the SCSI read command was
     received from the initiator.
 2.  It MUST generate and send an RDMA Write Message containing the
     read data to the initiator.
     a.  It MUST use the remote Read STag as the Data Sink STag of the
         RDMA Write Message.
     b.  It MUST use the Buffer Offset from the SCSI Data-in PDU as
         the Data Sink Tagged Offset of the RDMA Write Message.
     c.  It MUST use DataSegmentLength from the SCSI Data-in PDU to
         determine the amount of data to be sent in the RDMA Write
         Message.
 3.  It MUST associate DataSN and ITT from the SCSI Data-in PDU with
     the RDMA Write operation.  If the Put_Data Operational Primitive
     invocation was qualified with Notify_Enable set, then when the
     iSER layer at the target receives a completion from the RCaP
     layer for the RDMA Write Message, the iSER layer at the target
     MUST notify the iSCSI layer by invoking the
     Data_Completion_Notify Operational Primitive qualified with
     DataSN and ITT.  Conversely, if the Put_Data Operational
     Primitive invocation was qualified with Notify_Enable cleared,
     then the iSER layer at the target MUST NOT notify the iSCSI layer
     on completion and MUST NOT invoke the Data_Completion_Notify
     Operational Primitive.

Ko, et al. Standards Track [Page 46] RFC 5046 iSER Specification October 2007

 When the A-bit is set to 1 in the SCSI Data-in PDU, the iSER layer at
 the target MUST notify the iSCSI layer at the target when the data
 transfer is complete at the initiator.  To perform this additional
 function, the iSER layer at the target can take advantage of the
 operational ErrorRecoveryLevel if previously disclosed by the iSCSI
 layer via an earlier invocation of the Notice_Key_Values Operational
 Primitive.  There are two approaches that can be taken:
 1.  If the iSER layer at the target knows that the operational
     ErrorRecoveryLevel is 2, or if the iSER layer at the target does
     not know the operational ErrorRecoveryLevel, then the iSER layer
     at the target MUST issue a zero-length RDMA Read Request Message
     following the RDMA Write Message.  When the iSER layer at the
     target receives a completion for the RDMA Read Request Message
     from the RCaP layer, implying that the RDMA-Capable Controller at
     the initiator has completed processing the RDMA Write Message due
     to the completion ordering semantics of RCaP, the iSER layer at
     the target MUST notify the iSCSI layer at the target by invoking
     the Data_Ack_Notify Operational Primitive qualified with ITT and
     DataSN (see Section 3.2.3).
 2.  If the iSER layer at the target knows that the operational
     ErrorRecoveryLevel is 1, then the iSER layer at the target MUST
     do one of the following:
     a.  It MUST notify the iSCSI layer at the target by invoking the
         Data_Ack_Notify Operational Primitive qualified with ITT and
         DataSN (see Section 3.2.3) when it receives the local
         completion from the RCaP layer for the RDMA Write Message.
         This is allowed since digest errors do not occur in iSER (see
         Section 10.1.4.2) and a CRC error will cause the connection
         to be terminated and the task to be terminated anyway.  The
         local RDMA Write completion from the RCaP layer guarantees
         that the RCaP layer will not access the I/O Buffer again to
         transfer the data associated with that RDMA Write operation.
     b.  Alternatively, it MUST use the same procedure for handling
         the data transfer completion at the initiator as for
         ErrorRecoveryLevel 2.
 Note that the iSCSI layer at the target cannot set the A-bit to 1 if
 the ErrorRecoveryLevel=0.
 The SCSI status MUST always be returned in a separate SCSI Response
 PDU.  The S bit in the SCSI Data-in PDU MUST always be set to 0.
 There MUST NOT be a "phase collapse" in the SCSI Data-in PDU.

Ko, et al. Standards Track [Page 47] RFC 5046 iSER Specification October 2007

 Since the RDMA Write Message only transfers the data portion of the
 SCSI Data-in PDU but not the control information in the header, such
 as ExpCmdSN, if timely updates of such information are crucial, the
 iSCSI layer at the initiator MAY issue NOP-Out PDUs to request that
 the iSCSI layer at the target respond with the information using NOP-
 In PDUs.

7.3.6. Ready to Transfer (R2T)

    Type:  data-type PDU
    PDU-specific qualifiers:  DataDescriptorOut
 In order to send an R2T PDU, the iSCSI layer at the target MUST
 invoke the Get_Data Operational Primitive qualified with
 DataDescriptorOut, which defines the I/O Buffer for receiving the
 SCSI Write data from the initiator.  See Section 7.1 on the general
 requirements on the handling of iSCSI data-type PDUs.
 The iSER layer at the target MUST do the following for each
 invocation of the Get_Data Operational Primitive:
 1.  It MUST ensure a valid local STag for the I/O Buffer and a valid
     Local Mapping that associates the Initiator Task Tag (ITT) to the
     local STag.  This may involve allocating a valid local STag and
     establishing a Local Mapping.
 2.  It MUST use the ITT in the R2T to locate the remote Write STag in
     the Remote Mapping that associates the ITT to Advertised STag(s).
     The Remote Mapping is established earlier by the iSER layer at
     the target when the iSER Message containing the Advertised Write
     STag and the SCSI Command PDU for a SCSI write or bidirectional
     command is received from the initiator.
 3.  If the iSER-ORD value at the target is set to 0, the iSER layer
     at the target MUST terminate the connection and free up the
     resources associated with the connection (as described in Section
     5.2.3) if it receives the R2T PDU from the iSCSI layer at the
     target.  Upon termination of the connection, the iSER layer at
     the target MUST notify the iSCSI layer at the target by invoking
     the Connection_Terminate_Notify Operational Primitive.
 4.  If the iSER-ORD value at the target is set to greater than 0, the
     iSER layer at the target MUST transform the R2T PDU into an RDMA
     Read Request Message.  While transforming the R2T PDU, the iSER
     layer at the target MUST ensure that the number of outstanding
     RDMA Read Request Messages does not exceed the iSER-ORD value.
     To transform the R2T PDU, the iSER layer at the target:

Ko, et al. Standards Track [Page 48] RFC 5046 iSER Specification October 2007

     a.  MUST derive the local STag and local Tagged Offset from the
         DataDescriptorOut that qualified the Get_Data invocation.
     b.  MUST use the local STag as the Data Sink STag of the RDMA
         Read Request Message.
     c.  MUST use the local Tagged Offset as the Data Sink Tagged
         Offset of the RDMA Read Request Message.
     d.  MUST use the Desired Data Transfer Length from the R2T PDU as
         the RDMA Read Message Size of the RDMA Read Request Message.
     e.  MUST use the remote Write STag as the Data Source STag of the
         RDMA Read Request Message.
     f.  MUST use the Buffer Offset from the R2T PDU as the Data
         Source Tagged Offset of the RDMA Read Request Message.
 5.  It MUST associate R2TSN and ITT from the R2T PDU with the RDMA
     Read operation.  If the Get_Data Operational Primitive invocation
     is qualified with Notify_Enable set, then when the iSER layer at
     the target receives a completion from the RCaP layer for the RDMA
     Read operation, the iSER layer at the target MUST notify the
     iSCSI layer by invoking the Data_Completion_Notify Operational
     Primitive qualified with R2TSN and ITT.  Conversely, if the
     Get_Data Operational Primitive invocation is qualified with
     Notify_Enable cleared, then the iSER layer at the target MUST NOT
     notify the iSCSI layer on completion and MUST NOT invoke the
     Data_Completion_Notify Operational Primitive.
 When the RCaP layer at the initiator receives a valid RDMA Read
 Request Message, it will return an RDMA Read Response Message
 containing the solicited write data to the target.  When the RCaP
 layer at target receives the RDMA Read Response Message from the
 initiator, it will place the solicited data in the I/O Buffer
 referenced by the Data Sink STag in the RDMA Read Response Message.
 Since the RDMA Read Request Message from the target does not transfer
 the control information in the R2T PDU, such as ExpCmdSN, if timely
 updates of such information are crucial, the iSCSI layer at the
 initiator MAY issue NOP-Out PDUs to request that the iSCSI layer at
 the target respond with the information using NOP-In PDUs.
 Similarly, since the RDMA Read Response Message from the initiator
 only transfers the data but not the control information normally
 found in the SCSI Data-out PDU, such as ExpStatSN, if timely updates
 of such information are crucial, the iSCSI layer at the target MAY

Ko, et al. Standards Track [Page 49] RFC 5046 iSER Specification October 2007

 issue NOP-In PDUs to request that the iSCSI layer at the initiator
 respond with the information using NOP-Out PDUs.

7.3.7. Asynchronous Message

    Type:  control-type PDU
    PDU-specific qualifiers:  DataDescriptorSense
 The iSCSI layer MUST invoke the Send_Control Operational Primitive
 qualified with DataDescriptorSense, which defines the buffer
 containing the sense and iSCSI Event information.  The iSER layer
 MUST use a SendSE Message to send the Asynchronous Message PDU.

7.3.8. Text Request and Text Response

    Type:  control-type PDU
    PDU-specific qualifiers:  DataDescriptorTextOut (for Text
    Request), DataDescriptorIn (for Text Response)
 The iSCSI layer MUST invoke the Send_Control Operational Primitive
 qualified with DataDescriptorTextOut (or DataDescriptorIn), which
 defines the Text Request (or Text Response) buffer.  The iSER layer
 MUST use SendSE Messages to send the Text Request (or Text Response
 PDUs).

7.3.9. Login Request and Login Response

 During the login negotiation, the iSCSI layer interacts with the
 transport layer directly and the iSER layer is not involved.  See
 Section 5.1 on iSCSI/iSER connection setup.  If the underlying
 transport is TCP, the Login Request PDUs and the Login Response PDUs
 are exchanged when the connection between the initiator and the
 target is still in the byte stream mode.
 The iSCSI layer MUST not send a Login Request (or a Login Response)
 PDU during the Full Feature Phase.  A Login Request (or a Login
 Response) PDU, if used, MUST be treated as an iSCSI protocol error.
 The iSER layer MAY reject such a PDU from the iSCSI layer with an
 appropriate error code.  If a Login Request PDU is received by the
 iSCSI layer at the target, it MUST respond with a Reject PDU with a
 reason code of "protocol error".

Ko, et al. Standards Track [Page 50] RFC 5046 iSER Specification October 2007

7.3.10. Logout Request and Logout Response

    Type:  control-type PDU
    PDU-specific qualifiers:  None
 The iSER layer MUST use a SendSE Message to send the Logout Request
 or Logout Response PDU.  Sections 5.2.1 and 5.2.2 describe the
 handling of the Logout Request and the Logout Response at the
 initiator and the target and the interactions between the initiator
 and the target to terminate a connection.

7.3.11. SNACK Request

 Since HeaderDigest and DataDigest must be negotiated to "None", there
 are no digest errors when the connection is in iSER-assisted mode.
 Also, since RCaP delivers all messages in the order they were sent,
 there are no sequence errors when the connection is in iSER-assisted
 mode.  Therefore, the iSCSI layer MUST NOT send SNACK Request PDUs.
 A SNCAK Request PDU, if used, MUST be treated as an iSCSI protocol
 error.  The iSER layer MAY reject such a PDU from the iSCSI layer
 with an appropriate error code.  If a SNACK Request PDU is received
 by the iSCSI layer at the target, it MUST respond with a Reject PDU
 with a reason code of "protocol error".

7.3.12. Reject

    Type:  control-type PDU
    PDU-specific qualifiers:  DataDescriptorReject
 The iSCSI layer MUST invoke the Send_Control Operational Primitive
 qualified with DataDescriptorReject, which defines the Reject buffer.
 The iSER layer MUST use a SendSE Message to send the Reject PDU.

7.3.13. NOP-Out and NOP-In

    Type:  control-type PDU
    PDU-specific qualifiers:  DataDescriptorNOPOut (for NOP-Out),
    DataDescriptorNOPIn (for NOP-In)
 The iSCSI layer MUST invoke the Send_Control Operational Primitive
 qualified with DataDescriptorNOPOut (or DataDescriptorNOPIn), which
 defines the Ping (or Return Ping) data buffer.  The iSER layer MUST
 use SendSE Messages to send the NOP-Out (or NOP-In) PDU.

Ko, et al. Standards Track [Page 51] RFC 5046 iSER Specification October 2007

8. Flow Control and STag Management

8.1. Flow Control for RDMA Send Message Types

 Send Message Types in RCaP are used by the iSER layer to transfer
 iSCSI control-type PDUs.  Each Send Message Type in RCaP consumes an
 Untagged Buffer at the Data Sink.  However, neither the RCaP layer
 nor the iSER layer provides an explicit flow control mechanism for
 the Send Message Types.  Therefore, the iSER layer SHOULD provision
 enough Untagged buffers for handling incoming Send Message Types to
 prevent buffer exhaustion at the RCaP layer.  If buffer exhaustion
 occurs, it may result in the termination of the connection.
 An implementation may choose to satisfy the buffer requirement by
 using a common buffer pool shared across multiple connections, with
 usage limits on a per-connection basis and usage limits on the buffer
 pool itself.  In such an implementation, exceeding the buffer usage
 limit for a connection or the buffer pool itself may trigger
 interventions from the iSER layer to replenish the buffer pool and/or
 to isolate the connection causing the problem.
 iSER also provides the MaxOutstandingUnexpectedPDUs key to be used by
 the initiator and the target to declare the maximum number of
 outstanding "unexpected" control-type PDUs that it can receive.  It
 is intended to allow the receiving side to determine the amount of
 buffer resources needed beyond the normal flow control mechanism
 available in iSCSI.
 The buffer resources required at both the initiator and the target as
 a result of control-type PDUs sent by the initiator is described in
 Section 8.1.1.  The buffer resources required at both the initiator
 and target as a result of control-type PDUs sent by the target is
 described in Section 8.1.2.

8.1.1. Flow Control for Control-Type PDUs from the Initiator

 The control-type PDUs that can be sent by an initiator to a target
 can be grouped into the following categories:
 1.  Regulated:  Control-type PDUs in this category are regulated by
     the iSCSI CmdSN window mechanism and the immediate flag is not
     set.
 2.  Unregulated but Expected:  Control-type PDUs in this category are
     not regulated by the iSCSI CmdSN window mechanism but are
     expected by the target.

Ko, et al. Standards Track [Page 52] RFC 5046 iSER Specification October 2007

 3.  Unregulated and Unexpected:  Control-type PDUs in this category
     are not regulated by the iSCSI CmdSN window mechanism and are
     "unexpected" by the target.

8.1.1.1. Control-Type PDUs from the Initiator in the Regulated Category

 Control-type PDUs that can be sent by the initiator in this category
 are regulated by the iSCSI CmdSN window mechanism and the immediate
 flag is not set.
 The queuing capacity required of the iSCSI layer at the target is
 described in Section 3.2.2.1 of [RFC3720].  For each of the control-
 type PDUs that can be sent by the initiator in this category, the
 initiator MUST provision for the buffer resources required for the
 corresponding control-type PDU sent as a response from the target.
 The following is a list of the PDUs that can be sent by the initiator
 and the PDUs that are sent by the target in response:
     a.  When an initiator sends a SCSI Command PDU, it expects a SCSI
         Response PDU from the target.
     b.  When the initiator sends a Task Management Function Request
         PDU, it expects a Task Management Function Response PDU from
         the target.
     c.  When the initiator sends a Text Request PDU, it expects a
         Text Response PDU from the target.
     d.  When the initiator sends a Logout Request PDU, it expects a
         Logout Response PDU from the target.
     e.  When the initiator sends a NOP-Out PDU as a ping request with
         ITT != 0xffffffff and TTT = 0xffffffff, it expects a NOP-In
         PDU from the target with the same ITT and TTT as in the ping
         request.
 The response from the target for any of the PDUs enumerated here may
 alternatively be in the form of a Reject PDU sent instead before the
 task is active, as described in Section 6.3 of [RFC3720].

8.1.1.2. Control-Type PDUs from the Initiator in the Unregulated but

        Expected Category
 For the control-type PDUs in the Unregulated but Expected category,
 the amount of buffering resources required at the target can be
 predetermined.  The following is a list of the PDUs in this category:

Ko, et al. Standards Track [Page 53] RFC 5046 iSER Specification October 2007

     a.  SCSI Data-out PDUs are used by the initiator to send
         unsolicited data.  The amount of buffer resources required by
         the target can be determined using FirstBurstLength.  Note
         that SCSI Data-out PDUs are not used for solicited data since
         the R2T PDU that is used for solicitation is transformed into
         RDMA Read operations by the iSER layer at the target.  See
         Section 7.3.4.
     b.  A NOP-Out PDU with TTT != 0xffffffff is sent as a ping
         response by the initiator to the NOP-In PDU sent as a ping
         request by the target.

8.1.1.3. Control-Type PDUs from the Initiator in the Unregulated and

        Unexpected Category
 PDUs in the Unregulated and Unexpected category are PDUs with the
 immediate flag set.  The number of PDUs in this category that can be
 sent by an initiator is controlled by the value of
 MaxOutstandingUnexpectedPDUs declared by the target (see Section
 6.7).  After a PDU in this category is sent by the initiator, it is
 outstanding until it is retired.  At any time, the number of
 outstanding unexpected PDUs MUST not exceed the value of
 MaxOutstandingUnexpectedPDUs declared by the target.
 The target uses the value of MaxOutstandingUnexpectedPDUs that it
 declared to determine the amount of buffer resources required for
 control-type PDUs in this category that can be sent by an initiator.
 For the initiator, for each of the control-type PDUs that can be sent
 in this category, the initiator MUST provision for the buffer
 resources if required for the corresponding control-type PDU that can
 be sent as a response from the target.
 An outstanding PDU in this category is retired as follows.  If the
 CmdSN of the PDU sent by the initiator in this category is x, the PDU
 is outstanding until the initiator sends a non-immediate control-type
 PDU on the same connection with CmdSN = y (where y is at least x) and
 the target responds with a control-type PDU on any connection where
 ExpCmdSN is at least y+1.
 When the number of outstanding unexpected control-type PDUs equals
 MaxOutstandingUnexpectedPDUs, the iSCSI layer at the initiator MUST
 NOT generate any unexpected PDUs that otherwise it would have
 generated, even if it is intended for immediate delivery.

Ko, et al. Standards Track [Page 54] RFC 5046 iSER Specification October 2007

8.1.2. Flow Control for Control-Type PDUs from the Target

 Control-type PDUs that can be sent by a target and are expected by
 the initiator are listed in the Regulated category (see Section
 8.1.1.1).
 For the control-type PDUs that can be sent by a target and are
 unexpected by the initiator, the number is controlled by
 MaxOutstandingUnexpectedPDUs declared by the initiator (see Section
 6.7).  After a PDU in this category is sent by a target, it is
 outstanding until it is retired.  At any time, the number of
 outstanding unexpected PDUs MUST not exceed the value of
 MaxOutstandingUnexpectedPDUs declared by the initiator.  The
 initiator uses the value of MaxOutstandingUnexpectedPDUs that it
 declared to determine the amount of buffer resources required for
 control-type PDUs in this category that can be sent by a target.  The
 following is a list of the PDUs in this category and the conditions
 for retiring the outstanding PDU:
     a.  For an Asynchronous Message PDU with StatSN = x, the PDU is
         outstanding until the initiator sends a control-type PDU with
         ExpStatSN set to at least x+1.
     b.  For a Reject PDU with StatSN = x that is sent after a task is
         active, the PDU is outstanding until the initiator sends a
         control-type PDU with ExpStatSN set to at least x+1.
     c.  For a NOP-In PDU with ITT = 0xffffffff and StatSN = x, the
         PDU is outstanding until the initiator responds with a
         control-type PDU on the same connection where ExpStatSN is at
         least x+1.  But if the NOP-In PDU is sent as a ping request
         with TTT != 0xffffffff, the PDU can also be retired when the
         initiator sends a NOP-Out PDU with the same ITT and TTT as in
         the ping request.  Note that when a target sends a NOP-In PDU
         as a ping request, it must provision a buffer for the NOP-Out
         PDU sent as a ping response from the initiator.
 When the number of outstanding unexpected control-type PDUs equals
 MaxOutstandingUnexpectedPDUs, the iSCSI layer at the target MUST NOT
 generate any unexpected PDUs that otherwise it would have generated,
 even if its intent is to indicate an iSCSI error condition (e.g.,
 Asynchronous Message, Reject).  Task timeouts, as in the initiator
 waiting for a command completion or other connection and session
 level exceptions, will ensure that correct operational behavior will
 result in these cases despite not generating the PDU.  This rule
 overrides any other requirements elsewhere that require that a Reject
 PDU MUST be sent.

Ko, et al. Standards Track [Page 55] RFC 5046 iSER Specification October 2007

 (Implementation note:  A SCSI task timeout and recovery can be a
 lengthy process and hence SHOULD be avoided by proper provisioning of
 resources.)
 (Implementation note:  To ensure that the initiator has a means to
 inform the target that outstanding PDUs have been retired, the target
 should reserve the last unexpected control-type PDU allowable by the
 value of MaxOutstandingUnexpectedPDUs declared by the initiator for
 sending a NOP-In ping request with TTT != 0xffffffff to allow the
 initiator to return the NOP-Out ping response with the current
 ExpStatSN.)

8.2. Flow Control for RDMA Read Resources

 The total number of RDMA Read operations that can be active
 simultaneously on an iSCSI/iSER connection depends on the amount of
 resources allocated as declared in the iSER Hello exchange described
 in Section 5.1.3.  Exceeding the number of RDMA Read operations
 allowed on a connection will result in the connection being
 terminated by the RCaP layer.  The iSER layer at the target maintains
 the iSER-ORD to keep track of the maximum number of RDMA Read
 Requests that can be issued by the iSER layer on a particular RCaP
 Stream.
 During connection setup (see Section 5.1), iSER-IRD is known at the
 initiator and iSER-ORD is known at the target after the iSER layers
 at the initiator and the target have respectively allocated the
 connection resources necessary to support RCaP, as directed by the
 Allocate_Connection_Resources Operational Primitive from the iSCSI
 layer before the end of the iSCSI Login Phase.  In the Full Feature
 Phase, the first message sent by the initiator is the iSER Hello
 Message (see Section 9.3), which contains the value of iSER-IRD.  In
 response to the iSER Hello Message, the target sends the iSER
 HelloReply Message (see Section 9.4), which contains the value of
 iSER-ORD.  The iSER layer at both the initiator and the target MAY
 adjust (lower) the resources associated with iSER-IRD and iSER-ORD
 respectively to match the iSER-ORD value declared in the HelloReply
 Message.  The iSER layer at the target MUST flow control the RDMA
 Read Request Messages to not exceed the iSER-ORD value at the target.

8.3. STag Management

 An STag, as defined in [RDMAP], is an identifier of a Tagged Buffer
 used in an RDMA operation.  The allocation and the subsequent
 invalidation of the STags are specified in this document if the STags
 are exposed on the wire by being Advertised in the iSER header or
 declared in the header of an RCaP Message.

Ko, et al. Standards Track [Page 56] RFC 5046 iSER Specification October 2007

8.3.1. Allocation of STags

 When the iSCSI layer at the initiator invokes the Send_Control
 Operational Primitive to request that the iSER layer at the initiator
 process a SCSI command, zero, one, or two STags may be allocated by
 the iSER layer.  See Section 7.3.1 for details.  The number of STags
 allocated depends on whether the command is unidirectional or
 bidirectional and whether or not solicited write data transfer is
 involved.
 When the iSCSI layer at the initiator invokes the Send_Control
 Operational Primitive to request that the iSER layer at the initiator
 process a Task Management Function Request with the TASK REASSIGN
 function, besides allocating zero, one, or two STags, the iSER layer
 MUST invalidate the existing STags, if any, associated with the ITT.
 See Section 7.3.3 for details.
 The iSER layer at the target allocates a local Data Sink STag when
 the iSCSI layer at the target invokes the Get_Data Operational
 Primitive to request that the iSER layer process an R2T PDU.  See
 Section 7.3.6 for details.

8.3.2. Invalidation of STags

 The invalidation of the STags at the initiator at the completion of a
 unidirectional or bidirectional command when the associated SCSI
 Response PDU is sent by the target is described in Section 7.3.2.
 When a unidirectional or bidirectional command concludes without the
 associated SCSI Response PDU being sent by the target, the iSCSI
 layer at the initiator MUST request that the iSER layer at the
 initiator invalidate the STags by invoking the
 Deallocate_Task_Resources Operational Primitive qualified with ITT.
 In response, the iSER layer at the initiator MUST locate the STag(s)
 (if any) in the Local Mapping that associates the ITT to the local
 STag(s).  The iSER layer at the initiator MUST invalidate the STag(s)
 (if any) and the Local Mapping.
 For an RDMA Read operation used to realize a SCSI Write data
 transfer, the iSER layer at the target SHOULD invalidate the Data
 Sink STag at the conclusion of the RDMA Read operation referencing
 the Data Sink STag (to permit the immediate reuse of buffer
 resources).
 For an RDMA Write operation used to realize a SCSI Read data
 transfer, the Data Source STag at the target is not declared to the
 initiator and is not exposed on the wire.  Invalidation of the STag
 is thus not specified.

Ko, et al. Standards Track [Page 57] RFC 5046 iSER Specification October 2007

 When a unidirectional or bidirectional command concludes without the
 associated SCSI Response PDU being sent by the target, the iSCSI
 layer at the target MUST request that the iSER layer at the target
 invalidate the STags by invoking the Deallocate_Task_Resources
 Operational Primitive qualified with ITT.  In response, the iSER
 layer at the target MUST locate the local STag(s) (if any) in the
 Local Mapping that associates the ITT to the local STag(s).  The iSER
 layer at the target MUST invalidate the local STag(s) (if any) and
 the mapping.

9. iSER Control and Data Transfer

 For iSCSI data-type PDUs (see Section 7.1), the iSER layer uses RDMA
 Read and RDMA Write operations to transfer the solicited data.  For
 iSCSI control-type PDUs (see Section 7.2), the iSER layer uses Send
 Message Types of RCaP.

9.1. iSER Header Format

 An iSER header MUST be present in every Send Message Type of RCaP.
 The iSER header is located in the first 12 bytes of the message
 payload of the Send Message Type of RCaP, as shown in Figure 2.
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Opcode|                  Opcode Specific Fields               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                    Opcode Specific Fields                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                    Opcode Specific Fields                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                     Figure 2.  iSER Header Format
 Opcode - Operation Code: 4 bits
      The Opcode field identifies the type of iSER Messages:
         0001b = iSCSI control-type PDU
         0010b = iSER Hello Message
         0011b = iSER HelloReply Message
         All other opcodes are reserved.

Ko, et al. Standards Track [Page 58] RFC 5046 iSER Specification October 2007

9.2. iSER Header Format for the iSCSI Control-Type PDU

 The iSER layer uses Send Message Types of RCaP to transfer iSCSI
 control-type PDUs (see Section 7.2).  The message payload of each of
 the Send Message Types of RCaP used for transferring an iSER Message
 contains an iSER Header followed by an iSCSI control-type PDU.
 The iSER header in a Send Message Type of RCaP carrying an iSCSI
 control-type PDU MUST have the format as described in Figure 3.
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |       |W|R|                                                   |
    | 0001b |S|S|                  Reserved                         |
    |       |V|V|                                                   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Write STag (or N/A)                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         Read STag (or N/A)                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        Figure 3.  iSER Header Format for iSCSI Control-Type PDU
 WSV - Write STag Valid flag: 1 bit
     This flag indicates the validity of the Write STag field of the
     iSER Header.  If set to one, the Write STag field in this iSER
     Header is valid.  If set to zero, the Write STag field in this
     iSER Header MUST be ignored at the receiver.  The Write STag
     Valid flag is set to one when there is solicited data to be
     transferred for a SCSI write or bidirectional command, or when
     there are non-immediate unsolicited and solicited data to be
     transferred for the referenced task specified in a Task
     Management Function Request with the TASK REASSIGN function.
 RSV - Read STag Valid flag: 1 bit
     This flag indicates the validity of the Read STag field of the
     iSER Header.  If set to one, the Read STag field in this iSER
     Header is valid.  If set to zero, the Read STag field in this
     iSER Header MUST be ignored at the receiver.  The Read STag Valid
     flag is set to one for a SCSI read or bidirectional command, or
     for a Task Management Function Request with the TASK REASSIGN
     function.

Ko, et al. Standards Track [Page 59] RFC 5046 iSER Specification October 2007

 Write STag - Write Steering Tag: 32 bits
     This field contains the Write STag when the Write STag Valid flag
     is set to one.  For a SCSI write or bidirectional command, the
     Write STag is used to Advertise the initiator's I/O Buffer
     containing the solicited data.  For a Task Management Function
     Request with the TASK REASSIGN function, the Write STag is used
     to Advertise the initiator's I/O Buffer containing the non-
     immediate unsolicited data and solicited data.  This Write STag
     is used as the Data Source STag in the resultant RDMA Read
     operation(s).  When the Write STag Valid flag is set to zero,
     this field MUST be set to zero.
 Read STag - Read Steering Tag: 32 bits
     This field contains the Read STag when the Read STag Valid flag
     is set to one.  The Read STag is used to Advertise the
     initiator's Read I/O Buffer of a SCSI read or bidirectional
     command, or of a Task Management Function Request with the TASK
     REASSIGN function.  This Read STag is used as the Data Sink STag
     in the resultant RDMA Write operation(s).  When the Read STag
     Valid flag is zero, this field MUST be set to zero.
 Reserved:
     Reserved fields MUST be set to zero on transmit and MUST be
     ignored on reception.

9.3. iSER Header Format for the iSER Hello Message

 An iSER Hello Message MUST only contain the iSER header, which MUST
 have the format as described in Figure 4.  The iSER Hello Message is
 the first iSER Message sent on the RCaP Stream from the iSER layer at
 the initiator to the iSER layer at the target.
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |       |       |       |       |                               |
    | 0010b | Rsvd  | MaxVer| MinVer|           iSER-IRD            |
    |       |       |       |       |                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           Reserved                            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           Reserved                            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          Figure 4.  iSER Header Format for iSER Hello Message

Ko, et al. Standards Track [Page 60] RFC 5046 iSER Specification October 2007

 MaxVer - Maximum Version: 4 bits
     This field specifies the maximum version of the iSER protocol
     supported.  It MUST be set to one to indicate the version of the
     specification described in this document.
 MinVer - Minimum Version: 4 bits
     This field specifies the minimum version of the iSER protocol
     supported.  It MUST be set to one to indicate the version of the
     specification described in this document.
 iSER-IRD: 16 bits
     This field contains the value of the iSER-IRD at the initiator.
 Reserved (Rsvd):
     Reserved fields MUST be set to zero on transmit, and MUST be
     ignored on reception.

9.4. iSER Header Format for the iSER HelloReply Message

 An iSER HelloReply Message MUST only contain the iSER header which
 MUST have the format as described in Figure 5.  The iSER HelloReply
 Message is the first iSER Message sent on the RCaP Stream from the
 iSER layer at the target to the iSER layer at the initiator.
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |       |     |R|       |       |                               |
    | 0011b |Rsvd |E| MaxVer| CurVer|           iSER-ORD            |
    |       |     |J|       |       |                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           Reserved                            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           Reserved                            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       Figure 5.  iSER Header Format for iSER HelloReply Message
 REJ - Reject flag: 1 bit
     This flag indicates whether the target is rejecting this
     connection.  If set to one, the target is rejecting the
     connection.

Ko, et al. Standards Track [Page 61] RFC 5046 iSER Specification October 2007

 MaxVer - Maximum Version: 4 bits
     This field specifies the maximum version of the iSER protocol
     supported.  It MUST be set to one to indicate the version of the
     specification described in this document.
 CurVer - Current Version: 4 bits
     This field specifies the current version of the iSER protocol
     supported.  It MUST be set to one to indicate the version of the
     specification described in this document.
 iSER-ORD: 16 bits
     This field contains the value of the iSER-ORD at the target.
 Reserved (Rsvd):
     Reserved fields MUST be set to zero on transmit, and MUST be
     ignored on reception.

9.5. SCSI Data Transfer Operations

 The iSER layer at the initiator and the iSER layer at the target
 handle each SCSI Write, SCSI Read, and bidirectional operation as
 described below.

9.5.1. SCSI Write Operation

 The iSCSI layer at the initiator MUST invoke the Send_Control
 Operational Primitive to request that the iSER layer at the initiator
 send the SCSI write command.  The iSER layer at the initiator MUST
 request that the RCaP layer transmit a SendSE Message with the
 message payload consisting of the iSER header followed by the SCSI
 Command PDU and immediate data (if any).  If there is solicited data,
 the iSER layer MUST Advertise the Write STag in the iSER header of
 the SendSE Message, as described in Section 9.2.  Upon receiving the
 SendSE Message, the iSER layer at the target MUST notify the iSCSI
 layer at the target by invoking the Control_Notify Operational
 Primitive qualified with the SCSI Command PDU.  See Section 7.3.1 for
 details on the handling of the SCSI write command.
 For the non-immediate unsolicited data, the iSCSI layer at the
 initiator MUST invoke a Send_Control Operational Primitive qualified
 with the SCSI Data-out PDU.  Upon receiving each Send or SendSE
 Message containing the non-immediate unsolicited data, the iSER layer
 at the target MUST notify the iSCSI layer at the target by invoking
 the Control_Notify Operational Primitive qualified with the SCSI

Ko, et al. Standards Track [Page 62] RFC 5046 iSER Specification October 2007

 Data-out PDU.  See Section 7.3.4 for details on the handling of the
 SCSI Data-out PDU.
 For the solicited data, when the iSCSI layer at the target has an I/O
 Buffer available, it MUST invoke the Get_Data Operational Primitive
 qualified with the R2T PDU.  See Section 7.3.6 for details on the
 handling of the R2T PDU.
 When the data transfer associated with this SCSI Write operation is
 complete, the iSCSI layer at the target MUST invoke the Send_Control
 Operational Primitive when it is ready to send the SCSI Response PDU.
 Upon receiving a SendSE or SendInvSE Message containing the SCSI
 Response PDU, the iSER layer at the initiator MUST notify the iSCSI
 layer at the initiator by invoking the Control_Notify Operational
 Primitive qualified with the SCSI Response PDU.  See Section 7.3.2
 for details on the handling of the SCSI Response PDU.

9.5.2. SCSI Read Operation

 The iSCSI layer at the initiator MUST invoke the Send_Control
 Operational Primitive to request that the iSER layer at the initiator
 to send the SCSI read command.  The iSER layer at the initiator MUST
 request that the RCaP layer transmit a SendSE Message with the
 message payload consisting of the iSER header followed by the SCSI
 Command PDU.  The iSER layer at the initiator MUST Advertise the Read
 STag in the iSER header of the SendSE Message, as described in
 Section 9.2.  Upon receiving the SendSE Message, the iSER layer at
 the target MUST notify the iSCSI layer at the target by invoking the
 Control_Notify Operational Primitive qualified with the SCSI Command
 PDU.  See Section 7.3.1 for details on the handling of the SCSI read
 command.
 When the requested SCSI data is available in the I/O Buffer, the
 iSCSI layer at the target MUST invoke the Put_Data Operational
 Primitive qualified with the SCSI Data-in PDU.  See Section 7.3.5 for
 details on the handling of the SCSI Data-in PDU.
 When the data transfer associated with this SCSI Read operation is
 complete, the iSCSI layer at the target MUST invoke the Send_Control
 Operational Primitive when it is ready to send the SCSI Response PDU.
 Upon receiving the SendInvSE Message containing the SCSI Response
 PDU, the iSER layer at the initiator MUST notify the iSCSI layer at
 the initiator by invoking the Control_Notify Operational Primitive
 qualified with the SCSI Response PDU.  See Section 7.3.2 for details
 on the handling of the SCSI Response PDU.

Ko, et al. Standards Track [Page 63] RFC 5046 iSER Specification October 2007

9.5.3. Bidirectional Operation

 The initiator and the target handle the SCSI Write and the SCSI Read
 portions of this bidirectional operation the same as described in
 Sections 9.5.1 and 9.5.2, respectively.

10. iSER Error Handling and Recovery

 RCaP provides the iSER layer with reliable in-order delivery.
 Therefore, the error management needs of an iSER-assisted connection
 are somewhat different than those of a Traditional iSCSI connection.

10.1. Error Handling

 iSER error handling is described in the following sections,
 classified loosely based on the sources of errors:
 1.  Those originating at the transport layer (e.g., TCP).
 2.  Those originating at the RCaP layer.
 3.  Those originating at the iSER layer.
 4.  Those originating at the iSCSI layer.

10.1.1. Errors in the Transport Layer

 If the transport layer is TCP, then TCP packets with detected errors
 are silently dropped by the TCP layer and result in retransmission at
 the TCP layer.  This has no impact on the iSER layer.  However,
 connection loss (e.g., link failure) and unexpected termination
 (e.g., TCP graceful or abnormal close without the iSCSI Logout
 exchanges) at the transport layer will cause the iSCSI/iSER
 connection to be terminated as well.

10.1.1.1. Failure in the Transport Layer before RCaP Mode Is Enabled

 If the connection is lost or terminated before the iSCSI layer
 invokes the Allocate_Connection_Resources Operational Primitive, the
 login process is terminated and no further action is required.
 If the connection is lost or terminated after the iSCSI layer has
 invoked the Allocate_Connection_Resources Operational Primitive, then
 the iSCSI layer MUST request that the iSER layer deallocate all
 connection resources by invoking the Deallocate_Connection_Resources
 Operational Primitive.

Ko, et al. Standards Track [Page 64] RFC 5046 iSER Specification October 2007

10.1.1.2. Failure in the Transport Layer after RCaP Mode Is Enabled

 If the connection is lost or terminated after the iSCSI layer has
 invoked the Enable_Datamover Operational Primitive, the iSER layer
 MUST notify the iSCSI layer of the connection loss by invoking the
 Connection_Terminate_Notify Operational Primitive.  Prior to invoking
 the Connection_Terminate_Notify Operational Primitive, the iSER layer
 MUST perform the actions described in Section 5.2.3.2.

10.1.2. Errors in the RCaP Layer

 The RCaP layer does not have error recovery operations built in.  If
 errors are detected at the RCaP layer, the RCaP layer will terminate
 the RCaP Stream and the associated connection.

10.1.2.1. Errors Detected in the Local RCaP Layer

 If an error is encountered at the local RCaP layer, the RCaP layer
 MAY send a Terminate Message to the Remote Peer to report the error
 if possible.  (For iWARP, see [RDMAP] for the list of errors where a
 Terminate Message is sent.)  The RCaP layer is responsible for
 terminating the connection.  After the RCaP layer notifies the iSER
 layer that the connection is terminated, the iSER layer MUST notify
 the iSCSI layer by invoking the Connection_Terminate_Notify
 Operational Primitive.  Prior to invoking the
 Connection_Terminate_Notify Operational Primitive, the iSER layer
 MUST perform the actions described in Section 5.2.3.2.

10.1.2.2. Errors Detected in the RCaP Layer at the Remote Peer

 If an error is encountered at the RCaP layer at the Remote Peer, the
 RCaP layer at the Remote Peer may send a Terminate Message to report
 the error if possible.  If it is unable to send the Terminate
 Message, the connection is terminated.  This is treated the same as a
 failure in the transport layer after RDMA is enabled as described in
 Section 10.1.1.2.
 If an error is encountered at the RCaP layer at the Remote Peer and
 it is able to send a Terminate Message, the RCaP layer at the Remote
 Peer is responsible for terminating the connection.  After the local
 RCaP layer notifies the iSER layer that the connection is terminated,
 the iSER layer MUST notify the iSCSI layer by invoking the
 Connection_Terminate_Notify Operational Primitive.  Prior to invoking
 the Connection_Terminate_Notify Operational Primitive, the iSER layer
 MUST perform the actions described in Section 5.2.3.2.

Ko, et al. Standards Track [Page 65] RFC 5046 iSER Specification October 2007

10.1.3. Errors in the iSER Layer

 The error handling due to errors at the iSER layer is described in
 the following sections.

10.1.3.1. Insufficient Connection Resources to Support RCaP at

         Connection Setup
 After the iSCSI layer at the initiator invokes the
 Allocate_Connection_Resources Operational Primitive during the iSCSI
 Login Negotiation Phase, if the iSER layer at the initiator fails to
 allocate the connection resources necessary to support RCaP, it MUST
 return a status of failure to the iSCSI layer at the initiator.  The
 iSCSI layer at the initiator MUST terminate the connection as
 described in Section 5.2.3.1.
 After the iSCSI layer at the target invokes the
 Allocate_Connection_Resources Operational Primitive during the iSCSI
 Login Negotiation Phase, if the iSER layer at the target fails to
 allocate the connection resources necessary to support RCaP, it MUST
 return a status of failure to the iSCSI layer at the target.  The
 iSCSI layer at the target MUST send a Login Response with a status
 class of 3 (Target Error), and a status code of "0302" (Out of
 Resources).  The iSCSI layers at the initiator and the target MUST
 terminate the connection as described in Section 5.2.3.1.

10.1.3.2. iSER Negotiation Failures

 If the RCaP or iSER related parameters declared by the initiator in
 the iSER Hello Message are unacceptable to the iSER layer at the
 target, the iSER layer at the target MUST set the Reject (REJ) flag,
 as described in Section 9.4, in the iSER HelloReply Message.  The
 following are the cases when the iSER layer MUST set the REJ flag to
 one in the HelloReply Message:
  • The initiator-declared iSER-IRD value is greater than 0 and the

target-declared iSER-ORD value is 0.

  • The initiator-supported and the target-supported iSER protocol

versions do not overlap.

 After requesting that the RCaP layer send the iSER HelloReply
 Message, the handling of the error situation is the same as that for
 iSER format errors as described in Section 10.1.3.3.

Ko, et al. Standards Track [Page 66] RFC 5046 iSER Specification October 2007

10.1.3.3. iSER Format Errors

 The following types of errors in an iSER header are considered format
 errors:
  • Illegal contents of any iSER header field
  • Inconsistent field contents in an iSER header
  • Length error for an iSER Hello or HelloReply Message (see Section

9.3 and 9.4)

 When a format error is detected, the following events MUST occur in
 the specified sequence:
 1.  The iSER layer MUST request that the RCaP layer terminate the
     RCaP Stream.  The RCaP layer MUST terminate the associated
     connection.
 2.  The iSER layer MUST notify the iSCSI layer of the connection
     termination by invoking the Connection_Terminate_Notify
     Operational Primitive.  Prior to invoking the
     Connection_Terminate_Notify Operational Primitive, the iSER layer
     MUST perform the actions described in Section 5.2.3.2.

10.1.3.4. iSER Protocol Errors

 The first iSER Message sent by the iSER layer at the initiator after
 transitioning into iSER-assisted mode MUST be the iSER Hello Message
 (see Section 9.3).  Likewise, the first iSER Message sent by the iSER
 layer at the target after transitioning into iSER-assisted mode MUST
 be the iSER HelloReply Message (see Section 9.4).  Failure to send
 the iSER Hello or HelloReply Message, as indicated by the wrong
 Opcode in the iSER header, is a protocol error.  The handling of this
 error situation is the same as that for iSER format errors as
 described in Section 10.1.3.3.
 If the sending side of an iSER-enabled connection acts in a manner
 not permitted by the negotiated or declared login/text operational
 key values as described in Section 6, this is a protocol error, and
 the receiving side MAY handle this the same as for iSER format errors
 as described in Section 10.1.3.3.

10.1.4. Errors in the iSCSI Layer

 The error handling due to errors at the iSCSI layer is described in
 the following sections.  For error recovery, see Section 10.2.

Ko, et al. Standards Track [Page 67] RFC 5046 iSER Specification October 2007

10.1.4.1. iSCSI Format Errors

 When an iSCSI format error is detected, the iSCSI layer MUST request
 that the iSER layer terminate the RCaP Stream by invoking the
 Connection_Terminate Operational Primitive.  For more details on the
 connection termination, see Section 5.2.3.1.

10.1.4.2. iSCSI Digest Errors

 In the iSER-assisted mode, the iSCSI layer will not see any digest
 error because both the HeaderDigest and the DataDigest keys are
 negotiated to "None".

10.1.4.3. iSCSI Sequence Errors

 For Traditional iSCSI, sequence errors are caused by dropped PDUs due
 to header or data digest errors.  Since digests are not used in
 iSER-assisted mode and the RCaP layer will deliver all messages in
 the order they were sent, sequence errors will not occur in iSER-
 assisted mode.

10.1.4.4. iSCSI Protocol Error

 When the iSCSI layer handles certain protocol errors by dropping the
 connection, the error handling is the same as that for iSCSI format
 errors as described in Section 10.1.4.1.
 When the iSCSI layer uses the iSCSI Reject PDU and response codes to
 handle certain other protocol errors, no special handling at the iSER
 layer is required.

10.1.4.5. SCSI Timeouts and Session Errors

 SCSI Timeouts and Session Errors are handled at the iSCSI layer and
 no special handling at the iSER layer is required.

10.1.4.6. iSCSI Negotiation Failures

 For negotiation failures that happen during the Login Phase at the
 initiator after the iSCSI layer has invoked the
 Allocate_Connection_Resources Operational Primitive and before the
 Enable_Datamover Operational Primitive has been invoked, the iSCSI
 layer MUST request that the iSER layer deallocate all connection
 resources by invoking the Deallocate_Connection_Resources Operational
 Primitive.  The iSCSI layer at the initiator MUST terminate the
 connection.

Ko, et al. Standards Track [Page 68] RFC 5046 iSER Specification October 2007

 For negotiation failures during the Login Phase at the target, the
 iSCSI layer can use a Login Response with a status class other than 0
 (success) to terminate the Login Phase.  If the iSCSI layer has
 invoked the Allocate_Connection_Resources Operational Primitive
 before the Enable_Datamover Operational Primitive has been invoked,
 the iSCSI layer at the target MUST request that the iSER layer at the
 target deallocate all connection resources by invoking the
 Deallocate_Connection_Resources Operational Primitive.  The iSCSI
 layer at both the initiator and the target MUST terminate the
 connection.
 During the iSCSI Login Phase, if the iSCSI layer at the initiator
 receives a Login Response from the target with a status class other
 than 0 (Success) after the iSCSI layer at the initiator has invoked
 the Allocate_Connection_Resources Operational Primitive, the iSCSI
 layer MUST request the iSER layer to deallocate all connection
 resources by invoking the Deallocate_Connection_Resources Operational
 Primitive.  The iSCSI layer MUST terminate the connection in this
 case.
 For negotiation failures during the Full Feature Phase, the error
 handling is left to the iSCSI layer and no special handling at the
 iSER layer is required.

10.2. Error Recovery

 Error recovery requirements of iSCSI/iSER are the same as that of
 Traditional iSCSI.  All three ErrorRecoveryLevels as defined in
 [RFC3720] are supported in iSCSI/iSER.
  • For ErrorRecoveryLevel 0, session recovery is handled by iSCSI and

no special handling by the iSER layer is required.

  • For ErrorRecoveryLevel 1, see Section 10.2.1 on PDU Recovery.
  • For ErrorRecoveryLevel 2, see Section 10.2.2 on Connection

Recovery.

 The iSCSI layer may invoke the Notice_Key_Values Operational
 Primitive during connection setup to request that the iSER layer take
 note of the value of the operational ErrorRecoveryLevel, as described
 in Sections 5.1.1 and 5.1.2.

10.2.1. PDU Recovery

 As described in Sections 10.1.4.2 and 10.1.4.3, digest and sequence
 errors will not occur in the iSER-assisted mode.  If the RCaP layer
 detects an error, it will close the iSCSI/iSER connection, as

Ko, et al. Standards Track [Page 69] RFC 5046 iSER Specification October 2007

 described in Section 10.1.2.  Therefore, PDU recovery is not useful
 in the iSER-assisted mode.
 The iSCSI layer at the initiator SHOULD disable iSCSI timeout-driven
 PDU retransmissions.

10.2.2. Connection Recovery

 The iSCSI layer at the initiator MAY reassign connection allegiance
 for non-immediate commands that are still in progress and are
 associated with the failed connection by using a Task Management
 Function Request with the TASK REASSIGN function.  See Section 7.3.3
 for more details.
 When the iSCSI layer at the initiator does a task reassignment for a
 SCSI write command, it MUST qualify the Send_Control Operational
 Primitive invocation with DataDescriptorOut, which defines the I/O
 Buffer for both the non-immediate unsolicited data and the solicited
 data.  This allows the iSCSI layer at the target to use recovery R2Ts
 to request data originally sent as unsolicited and solicited from the
 initiator.
 When the iSCSI layer at the target accepts a reassignment request for
 a SCSI read command, it MUST request that the iSER layer process SCSI
 Data-in for all unacknowledged data by invoking the Put_Data
 Operational Primitive.  See Section 7.3.5 on the handling of SCSI
 Data-in.
 When the iSCSI layer at the target accepts a reassignment request for
 a SCSI write command, it MUST request that the iSER layer process a
 recovery R2T for any non-immediate unsolicited data and any solicited
 data sequences that have not been received by invoking the Get_Data
 Operational Primitive.  See Section 7.3.6 on the handling of Ready To
 Transfer (R2T).
 The iSCSI layer at the target MUST NOT issue recovery R2Ts on an
 iSCSI/iSER connection for a task for which the connection allegiance
 was never reassigned.  The iSER layer at the target MAY reject such a
 recovery R2T received via the Get_Data Operational Primitive
 invocation from the iSCSI layer at the target, with an appropriate
 error code.
 The iSER layer at the target will process the requests invoked by the
 Put_Data and Get_Data Operational Primitives for a reassigned task in
 the same way as for the original commands.

Ko, et al. Standards Track [Page 70] RFC 5046 iSER Specification October 2007

11. Security Considerations

 When iSER is layered on top of an RCaP layer and provides the RDMA
 extensions to the iSCSI protocol, the security considerations of iSER
 are the same as that of the underlying RCaP layer.  For iWARP, this
 is described in [RDMAP] and [RDDPSEC].
 Since the iSER-assisted iSCSI protocol is still functionally iSCSI
 from a security considerations perspective, all of the iSCSI security
 requirements as described in [RFC3720] and [RFC3723] apply.  If the
 IPsec [IPSEC] mechanism is used, then it MUST be established before
 the connection transitions to the iSER-assisted mode.  If iSER is
 layered on top of a non-IP based RCaP layer, all the security
 protocol mechanisms applicable to that RCaP layer are also applicable
 to an iSCSI/iSER connection.  If iSER is layered on top of a non-IP
 protocol, the IPsec mechanism as specified in [RFC3720] MUST be
 implemented at any point where the iSER protocol enters the IP
 network (e.g., via gateways), and the non-IP protocol SHOULD
 implement (optional to use) a packet-by packet security protocol
 equal in strength to the IPsec mechanism specified by [RFC3720].
 To minimize the potential for a denial-of-service attack, the iSCSI
 layer MUST NOT request that the iSER layer allocate the connection
 resources necessary to support RCaP until the iSCSI layer is
 sufficiently far along in the iSCSI Login Phase that it is reasonably
 certain that the peer side is not an attacker, as described in
 Sections 5.1.1 and 5.1.2.
 Note that the IPsec requirements for this document are based on the
 version of IPsec specified in RFC 2401 [IPSEC] and related RFCs, as
 profiled by RFC 3723 [RFC3723], despite the existence of a newer
 version of IPsec specified in RFC 4301 [RFC4301] and related RFCs.

12. References

12.1. Normative References

 [RFC3720] Satran, J., Meth, K., Sapuntzakis, C., Chadalapaka, M., and
           E. Zeidner, "Internet Small Computer Systems Interface
           (iSCSI)", RFC 3720, April 2004.
 [RFC3723] Aboba, B., Tseng, J., Walker, J., Rangan, V., and F.
           Travostino, "Securing Block Storage Protocols over IP", RFC
           3723, April 2004.
 [RDMAP]   Recio, R., Culley, P., Garcia, D., Hilland, J., and B.
           Metzler, "A Remote Direct Memory Access Protocol
           Specification", RFC 5040, October 2007.

Ko, et al. Standards Track [Page 71] RFC 5046 iSER Specification October 2007

 [DDP]     Shah, H., Pinkerton, J., Recio, R., and P. Culley, "Direct
           Data Placement over Reliable Transports", RFC 5041, October
           2007.
 [IPSEC]   Kent, S. and R. Atkinson, "Security Architecture for the
           Internet Protocol", RFC 2401, November 1998.
 [MPA]     Culley, P., Elzur, U., Recio, R., Bailey, S., and J.
           Carrier, "Marker PDU Aligned Framing for TCP
           Specification", RFC 5044, October 2007.
 [RDDPSEC] Pinkerton, J. and E. Deleganes, "Direct Data Placement
           Protocol (DDP) / Remote Direct Memory Access Protocol
           (RDMAP) Security", RFC 5042, October 2007.
 [TCP]     Postel, J., "Transmission Control Protocol", STD 7, RFC
           793, September 1981.
 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
           Requirement Levels", BCP 14, RFC 2119, March 1997.

12.2. Informative References

 [SAM2]    T10/1157D, SCSI Architecture Model - 2 (SAM-2)
 [DA]      Chadalapaka, M., Hufferd, J., Satran, J., and H. Shah, "DA:
           Datamover Architecture for the Internet Small Computer
           System Interface (iSCSI)", RFC 5047, October 2007.
 [IB]      InfiniBand Architecture Specification Volume 1 Release 1.2,
           October 2004
 [IPoIB]   Chu, J. and V. Kashyap, "Transmission of IP over InfiniBand
           (IPoIB)", RFC 4391, April 2006.
 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the
           Internet Protocol", RFC 4301, December 2005.

Ko, et al. Standards Track [Page 72] RFC 5046 iSER Specification October 2007

Appendix A. iWARP Message Format for iSER

 This section is for information only and is NOT part of the standard.
 It simply depicts the iWARP Message format for the various iSER
 Messages when the transport layer is TCP.

A.1. iWARP Message Format for iSER Hello Message

 The following figure depicts an iSER Hello Message encapsulated in an
 iWARP SendSE Message.
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         MPA Header            |  DDP Control  | RDMA Control  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Reserved                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       (Send) Queue Number                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                 (Send) Message Sequence Number                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      (Send) Message Offset                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | 0010b | Zeros | 0001b | 0001b |           iSER-IRD            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           All Zeros                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           All Zeros                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           MPA CRC                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       Figure 6.  SendSE Message Containing an iSER Hello Message

Ko, et al. Standards Track [Page 73] RFC 5046 iSER Specification October 2007

A.2. iWARP Message Format for iSER HelloReply Message

 The following figure depicts an iSER HelloReply Message encapsulated
 in an iWARP SendSE Message.  The Reject (REJ) flag is set to 0.
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         MPA Header            |  DDP Control  | RDMA Control  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Reserved                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       (Send) Queue Number                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                 (Send) Message Sequence Number                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      (Send) Message Offset                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | 0011b |Zeros|0| 0001b | 0001b |           iSER-ORD            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           All Zeros                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           All Zeros                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           MPA CRC                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     Figure 7.  SendSE Message Containing an iSER HelloReply Message

Ko, et al. Standards Track [Page 74] RFC 5046 iSER Specification October 2007

A.3. iWARP Message Format for SCSI Read Command PDU

 The following figure depicts a SCSI Read Command PDU embedded in an
 iSER Message encapsulated in an iWARP SendSE Message.  For this
 particular example, in the iSER header, the Write STag Valid flag is
 set to zero, the Read STag Valid flag is set to one, the Write STag
 field is set to all zeros, and the Read STag field contains a valid
 Read STag.
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         MPA Header            |  DDP Control  | RDMA Control  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Reserved                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       (Send) Queue Number                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                 (Send) Message Sequence Number                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      (Send) Message Offset                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | 0001b |0|1|                  All zeros                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         All Zeros                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         Read STag                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       SCSI Read Command PDU                   |
    //                                                             //
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           MPA CRC                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      Figure 8.  SendSE Message Containing a SCSI Read Command PDU

Ko, et al. Standards Track [Page 75] RFC 5046 iSER Specification October 2007

A.4. iWARP Message Format for SCSI Read Data

 The following figure depicts an iWARP RDMA Write Message carrying
 SCSI Read data in the payload:
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         MPA Header            |   DDP Control | RDMA Control  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       Data Sink STag                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                   Data Sink Tagged Offset                     |
    +                                                               +
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      SCSI Read data                           |
    //                                                             //
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           MPA CRC                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         Figure 9.  RDMA Write Message Containing SCSI Read Data

Ko, et al. Standards Track [Page 76] RFC 5046 iSER Specification October 2007

A.5. iWARP Message Format for SCSI Write Command PDU

 The following figure depicts a SCSI Write Command PDU embedded in an
 iSER Message encapsulated in an iWARP SendSE Message.  For this
 particular example, in the iSER header, the Write STag Valid flag is
 set to one, the Read STag Valid flag is set to zero, the Write STag
 field contains a valid Write STag, and the Read STag field is set to
 all zeros since it is not used.
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         MPA Header            |  DDP Control  | RDMA Control  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Reserved                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       (Send) Queue Number                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                 (Send) Message Sequence Number                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      (Send) Message Offset                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | 0001b |1|0|                  All zeros                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Write STag                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         All Zeros                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       SCSI Write Command PDU                  |
    //                                                             //
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           MPA CRC                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     Figure 10.  SendSE Message Containing a SCSI Write Command PDU

Ko, et al. Standards Track [Page 77] RFC 5046 iSER Specification October 2007

A.6. iWARP Message Format for RDMA Read Request

 An iSCSI R2T is transformed into an iWARP RDMA Read Request Message.
 The following figure depicts an iWARP RDMA Read Request Message:
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         MPA Header            |  DDP Control  | RDMA Control  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      Reserved (Not Used)                      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |              DDP (RDMA Read Request) Queue Number             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |        DDP (RDMA Read Request) Message Sequence Number        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |             DDP (RDMA Read Request) Message Offset            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     Data Sink STag (SinkSTag)                 |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    +                  Data Sink Tagged Offset (SinkTO)             +
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                  RDMA Read Message Size (RDMARDSZ)            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     Data Source STag (SrcSTag)                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    +                 Data Source Tagged Offset (SrcTO)             +
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           MPA CRC                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                 Figure 11.  RDMA Read Request Message

Ko, et al. Standards Track [Page 78] RFC 5046 iSER Specification October 2007

A.7. iWARP Message Format for Solicited SCSI Write Data

 The following figure depicts an iWARP RDMA Read Response Message
 carrying the solicited SCSI Write data in the payload:
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         MPA Header            |  DDP Control  | RDMA Control  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       Data Sink STag                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                   Data Sink Tagged Offset                     |
    +                                                               +
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       SCSI Write Data                         |
    //                                                             //
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           MPA CRC                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    Figure 12.  RDMA Read Response Message Containing SCSI Write Data

Ko, et al. Standards Track [Page 79] RFC 5046 iSER Specification October 2007

A.8. iWARP Message Format for SCSI Response PDU

 The following figure depicts a SCSI Response PDU embedded in an iSER
 Message encapsulated in an iWARP SendInvSE Message:
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         MPA Header            |  DDP Control  | RDMA Control  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      Invalidate STag                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       (Send) Queue Number                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                 (Send) Message Sequence Number                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      (Send) Message Offset                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | 0001b |0|0|                  All Zeros                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           All Zeros                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           All Zeros                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       SCSI Response PDU                       |
    //                                                             //
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           MPA CRC                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       Figure 13.  SendInvSE Message Containing SCSI Response PDU

Ko, et al. Standards Track [Page 80] RFC 5046 iSER Specification October 2007

Appendix B. Architectural Discussion of iSER over InfiniBand

 This section explains how an InfiniBand network (with Gateways) would
 be structured.  It is informational only and is intended to provide
 insight on how iSER is used in an InfiniBand environment.

B.1. The Host Side of the iSCSI and iSER Connections in InfiniBand

 Figure 14 defines the topologies in which iSCSI and iSER will be able
 to operate on an InfiniBand Network.
 +---------+ +---------+ +---------+ +---------+ +--- -----+
 |  Host   | |  Host   | |   Host  | |   Host  | |   Host  |
 |         | |         | |         | |         | |         |
 +---+-+---+ +---+-+---+ +---+-+---+ +---+-+---+ +---+-+---+
 |HCA| |HCA| |HCA| |HCA| |HCA| |HCA| |HCA| |HCA| |HCA| |HCA|
 +-v-+ +-v-+ +-v-+ +-v-+ +-v-+ +-v-+ +-v-+ +-v-+ +-v-+ +-v-+
   |----+------|-----+-----|-----+-----|-----+-----|-----+---> To IB
 IB|        IB |        IB |        IB |        IB |    SubNet2 SWTCH
 +-v-----------v-----------v-----------v-----------v---------+
 |                  InfiniBand Switch for Subnet1            |
 +---+-----+--------+-----+--------+-----+------------v------+
     | TCA |        | TCA |        | TCA |            |
     +-----+        +-----+        +-----+            | IB
    /  IB   \      /  IB   \      /       \     +--+--v--+--+
   |  iSER   |    |  iSER   |    |  IPoIB  |    |  | TCA |  |
   | Gateway |    | Gateway |    | Gateway |    |  +-----+  |
   |   to    |    |   to    |    |   to    |    | Storage   |
   |  iSCSI  |    |  iSER   |    |   IP    |    | Controller|
   |   TCP   |    |  iWARP  |    |Ethernet |    +-----+-----+
   +---v-----|    +---v-----|    +----v----+
       | EN           | EN            | EN
       +--------------+---------------+----> to IP based storage
         Ethernet links that carry iSCSI or iWARP
                 Figure 14.  iSCSI and iSER on IB
 In Figure 14, the Host systems are connected via the InfiniBand Host
 Channel Adapters (HCAs) to the InfiniBand links.  With the use of IB
 switch(es), the InfiniBand links connect the HCA to InfiniBand Target
 Channel Adapters (TCAs) located in gateways or Storage Controllers.
 An iSER-capable IB-IP Gateway converts the iSER Messages encapsulated
 in IB protocols to either standard iSCSI, or iSER Messages for iWARP.
 An [IPoIB] Gateway converts the InfiniBand [IPoIB] protocol to IP
 protocol, and in the iSCSI case, permits iSCSI to be operated on an
 IB Network between the Hosts and the [IPoIB] Gateway.

Ko, et al. Standards Track [Page 81] RFC 5046 iSER Specification October 2007

B.2. The Storage Side of the iSCSI and iSER Mixed Network Environment

 Figure 15 shows a storage controller that has three different portal
 groups: one supporting only iSCSI (TPG-4), one supporting iSER/iWARP
 or iSCSI (TPG-2), and one supporting iSER/IB (TPG-1).
                |                |                |
                |                |                |
          +--+--v--+----------+--v--+----------+--v--+--+
          |  | IB  |          |iWARP|          | EN  |  |
          |  |     |          | TCP |          | NIC |  |
          |  |(TCA)|          | RNIC|          |     |  |
          |  +-----|          +-----+          +-----+  |
          |   TPG-1            TPG-2            TPG-4   |
          |  9.1.3.3          9.1.2.4          9.1.2.6  |
          |                                             |
          |                  Storage Controller         |
          |                                             |
          +---------------------------------------------+
 Figure 15.  Storage Controller with TCP, iWARP, and IB Connections
 The normal iSCSI portal group advertising processes (via the Service
 Location Protocol (SLP), the Internet Storage Name Service (iSNS), or
 SendTargets) are available to a Storage Controller.

B.3. Discovery Processes for an InfiniBand Host

 An InfiniBand Host system can gather portal group IP addresses from
 SLP, iSNS, or the SendTargets discovery processes by using TCP/IP via
 [IPoIB].  After obtaining one or more remote portal IP addresses, the
 Initiator uses the standard IP mechanisms to resolve the IP address
 to a local outgoing interface and the destination hardware address
 (Ethernet MAC or IB GID of the target or a gateway leading to the
 target).  If the resolved interface is an [IPoIB] network interface,
 then the target portal can be reached through an InfiniBand fabric.
 In this case, the Initiator can establish an iSCSI/TCP or iSCSI/iSER
 session with the Target over that InfiniBand interface, using the
 Hardware Address (InfiniBand GID) obtained through the standard
 Address Resolution (ARP) processes.
 If more than one IP address is obtained through the discovery
 process, the Initiator should select a Target IP address that is on
 the same IP subnet as the Initiator, if one exists.  This will avoid
 a potential overhead of going through a gateway when a direct path
 exists.

Ko, et al. Standards Track [Page 82] RFC 5046 iSER Specification October 2007

 In addition, a user can configure manual static IP route entries if a
 particular path to the target is preferred.

B.4. IBTA Connection Specifications

 The InfiniBand Trade Association (IBTA) connection specifications are
 outside the scope of this document, but it is expected that the IBTA
 has or will define:
  • The iSER ServiceID.
  • A Means for permitting a Host to establish a connection with a

peer InfiniBand end-node, and to fall back to iSCSI/TCP over

    [IPoIB] if that peer indicates iSER is not supported.
  • A Means for permitting the Host to establish connections with IB

iSER connections on storage controllers or IB iSER connected

    Gateways in preference to [IPoIB] connected Gateways/Bridges or
    connections to Target Storage Controllers that also accept iSCSI
    via [IPoIB].
  • A Means for combining the IB ServiceID for iSER and the IP port

number such that the IB Host can use normal IB connection

    processes, yet ensure that the iSER target peer can actually
    connect to the required IP port number.

Acknowledgments

 This protocol was developed by a design team that, in addition to the
 authors, included Dwight Barron (HP), John Carrier (formerly from
 Adaptec), Ted Compton (EMC), Paul R. Culley (HP), Yaron Haviv
 (Voltaire), Jeff Hilland (HP), Mike Krause (HP), Alex Nezhinsky
 (Voltaire), Jim Pinkerton (Microsoft), Renato J. Recio (IBM), Julian
 Satran (IBM), Tom Talpey (Network Appliance), and Jim Wendt (HP).
 Special thanks to David Black (EMC) for his extensive review
 comments.

Ko, et al. Standards Track [Page 83] RFC 5046 iSER Specification October 2007

Author's Address

 Mallikarjun Chadalapaka
 Hewlett-Packard Company
 8000 Foothills Blvd.
 Roseville, CA 95747-5668, USA
 Phone: +1-916-785-5621
 EMail: cbm@rose.hp.com
 Uri Elzur
 Broadcom Corporation
 5300 California Avenue
 Irvine, CA 92617, USA
 Phone: +1-949-926-6432
 EMail: Uri@Broadcom.com
 John Hufferd
 Brocade Communications Systems, Inc.
 1745 Technology Drive
 San Jose, CA 95110, USA
 Phone: +1-408-333-5244
 EMail: jhufferd@brocade.com
 Mike Ko
 IBM Corp.
 650 Harry Rd.
 San Jose, CA 95120, USA
 Phone: +1-408-927-2085
 EMail: mako@us.ibm.com
 Hemal Shah
 Broadcom Corporation
 5300 California Avenue
 Irvine, CA 92617, USA
 Phone: +1-949-926-6941
 EMail: hemal@broadcom.com
 Patricia Thaler
 Broadcom Corporation
 5300 California Avenue
 Irvine, CA 92617, USA
 Phone: +1-916-570-2707
 EMail: pthaler@broadcom.com

Ko, et al. Standards Track [Page 84] RFC 5046 iSER Specification October 2007

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 contained in BCP 78, and except as set forth therein, the authors
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Ko, et al. Standards Track [Page 85]

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