GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc2835

Network Working Group J.-M. Pittet Request for Comments: 2835 Silicon Graphics Inc. Category: Standards Track May 2000

                  IP and ARP over HIPPI-6400 (GSN)

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.

Copyright Notice

 Copyright (C) The Internet Society (2000).  All Rights Reserved.

Abstract

 The ANSI T11.1 task force has standardized HIPPI-6400 also known as
 Gigabyte System Network (GSN), a physical-level, point-to-point,
 full-duplex, link interface for reliable, flow-controlled,
 transmission of user data at 6400 Mbit/s, per direction. A parallel
 copper cable interface for distances of up to 40 m is specified in
 HIPPI-6400-PH [1].  Connections to a longer-distance optical
 interface are standardized in HIPPI-6400-OPT [3].
 HIPPI-6400-PH [1] defines the encapsulation of IEEE 802.2 LLC PDUs
 [10] and by implication, IP on GSN. Another T11.1 standard describes
 the operation of HIPPI-6400 physical switches HIPPI-6400-SC [2].
 T11.1 chose to leave HIPPI-6400 networking issues largely outside the
 scope of their standards; this document specifies the use of HIPPI-
 6400 switches as IP local area networks. This document further
 specifies a method for resolving IP addresses to HIPPI-6400 hardware
 addresses (HARP) and for emulating IP broadcast in a logical IP
 subnet (LIS) as a direct extension of HARP. Furthermore it is the
 goal of this memo to define a IP and HARP that will allow
 interoperability for HIPPI-800 and HIPPI-6400 equipment both
 broadcast and non-broadcast capable networks.

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . .   3
 2.  Definitions . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1 Global concepts used  . . . . . . . . . . . . . . . .   3
     2.2 Glossary  . . . . . . . . . . . . . . . . . . . . . .   4

Pittet Standards Track [Page 1] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

 3.  IP Subnetwork Configuration . . . . . . . . . . . . . . .   5
     3.1 Background  . . . . . . . . . . . . . . . . . . . . .   5
     3.2 HIPPI LIS Requirements  . . . . . . . . . . . . . . .   6
 4.  Internet Protocol . . . . . . . . . . . . . . . . . . . .   7
     4.1  Packet Format  . . . . . . . . . . . . . . . . . . .   7
          4.1.1 IEEE 802.2 LLC . . . . . . . . . . . . . . . .   7
          4.1.2 SNAP . . . . . . . . . . . . . . . . . . . . .   7
          4.1.3 Packet diagrams  . . . . . . . . . . . . . . .   8
     4.2  HIPPI-6400 Hardware address: Universal LAN MAC addr.   9
     4.3  Maximum Transmission Unit - MTU  . . . . . . . . . .  10
 5.  HIPPI Address Resolution Protocol - HARP  . . . . . . . .  11
     5.1  HARP Algorithm . . . . . . . . . . . . . . . . . . .  12
          5.1.1 Selecting the authoritative HARP service . . .  12
          5.1.2 HARP registration phase  . . . . . . . . . . .  13
          5.1.3 HARP operational phase . . . . . . . . . . . .  14
     5.2  HARP Client Operational Requirements . . . . . . . .  15
     5.3  Receiving Unknown HARP Messages  . . . . . . . . . .  16
     5.4  HARP Server Operational Requirements . . . . . . . .  16
     5.5  HARP and Permanent ARP Table Entries . . . . . . . .  18
     5.6  HARP Table Aging . . . . . . . . . . . . . . . . . .  18
 6.  HARP Message Encoding . . . . . . . . . . . . . . . . . .  19
     6.1 Generic IEEE 802 ARP Message Format . . . . . . . . .  19
     6.2 HIPARP Message Formats  . . . . . . . . . . . . . . .  21
         6.2.1 Example Message encodings:  . . . . . . . . . .  23
         6.2.2 HARP_NAK message format . . . . . . . . . . . .  24
 7.  Broadcast and Multicast   . . . . . . . . . . . . . . . .  24
     7.1 Protocol for an IP Broadcast Emulation Server - PIBES  25
     7.2 IP Broadcast Address  . . . . . . . . . . . . . . . .  25
     7.3 IP Multicast Address  . . . . . . . . . . . . . . . .  25
     7.4 A Note on Broadcast Emulation Performance . . . . . .  26
 8.  HARP for Scheduled Transfer . . . . . . . . . . . . . . .  26
 9.  Security Consierations  . . . . . . . . . . . . . . . . .  26
 10. Open Issues . . . . . . . . . . . . . . . . . . . . . . .  27
 11.  HARP Examples  . . . . . . . . . . . . . . . . . . . . .  27
      11.1 Registr. Phase of Client Y on Non-broadcast Hardware 27
      11.2 Registr. Phase of Client Y on Broadcast-capable . .  28
      11.3 Operational Phase (phase II)  . . . . . . . . . . .  29
           11.3.1 Successful HARP_Resolve example  . . . . . .  29
           11.3.2 Non-successful HARP_Resolve example  . . . .  30
 12.  References . . . . . . . . . . . . . . . . . . . . . . .  31
 13.  Acknowledgments  . . . . . . . . . . . . . . . . . . . .  32
 14.  Author's Address . . . . . . . . . . . . . . . . . . . .  32
 15.  Full Copyright Statement . . . . . . . . . . . . . . . .  33

Pittet Standards Track [Page 2] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

1. Introduction

 HIPPI-6400 is a duplex data channel that can transmit and receive
 data simultaneously at nearly 6400 megabits per second. HIPPI-6400
 data transfers are segmented into micropackets, each composed of 32
 data bytes and 8 control bytes. HIPPI-6400 uses four multiplexed
 virtual channels. These virtual channels are allocated to control
 traffic, low latency traffic, and bulk traffic (see [1] for more
 details).
 Using small packets and four virtual channels, large file transfers
 cannot lock out a host or switch port for interactive traffic.
 HIPPI-6400 guarantees in order delivery of data. It also supports
 link-level and end-to-end checksumming and credit-based flow control.
 HIPPI-6400-PH defines a 20-bit interface for copper cables operating
 at 500 MBaud. This provides a user payload bandwidth of 6400 Mb/s
 (800,000,000 Bytes/sec) in each direction. [8]
 HIPPI-6400-SC [2] defines two types of switches: bridging and non-
 bridging. The bridging switches are required to support hardware
 broadcast.  Non-bridging switches are not required to support
 broadcast.  This memo allows for a coherent implementation of IP and
 HARP with both types of switches.
 Gigabyte System Network(TM) (GSN) is a marketing name for HIPPI-6400.
 It is a trademark of the High Performance Networking Forum (HNF;
 http://www.hnf.org) for use by its member companies that supply
 products complying to ANSI HIPPI-6400 standards.

2 Definitions

 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 RFC-2119 [19].

2.1 Global concepts used

 In the following discussion, the terms "requester" and "target" are
 used to identify the port initiating the address resolution request
 and the port whose address it wishes to discover, respectively. This
 document will use HIPPI-800 and HIPPI-6400 when referring to concepts
 that apply to one or the other technology. The term HIPPI will be
 used when referring to both technologies.
 Values are decimal unless otherwise noted. Formatting follows IEEE
 802.1A canonical bit order and HIPPI-6400-PH bit and byte ordering.

Pittet Standards Track [Page 3] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

2.2 Glossary

 Broadcast
 A distribution mode which transmits a message to all ports. The
 sending port is part of "all" and will therefore also receive a copy
 of the sent message.
 Classical/Conventional
 Both terms are used with respect to networks, including Ethernet,
 FDDI, and other 802 LAN types, as distinct from HIPPI-SC LANs.
 Destination
 The HIPPI port that receives data from a HIPPI Source.
 HARP
 HARP (HIPPI Address Resolution Protocol describes the whole set of
 HIPPI-6400 address resolution encodings and algorithms defined in
 this memo. HARP is a combination and adaptation of the Internet
 Address Resolution Protocol (ARP) RFC-826 [14] and Inverse ARP
 (InARP) [5] (see section 5). HARP also describes the HIPPI (800 and
 6400) specific version of ARP (i.e. the protocol and the HIPPI
 specific encoding).
 HARP table
 Each host has a HARP table which contains the IP to hardware address
 mapping of IP members.
 HRAL
 The HARP Request Address List.  A list of ULAs to which HARP messages
 are sent when resolving names to addresses (see section 3.2).
 Hardware (HW) address
 The hardware address of a port; it consists of an ULA (see section
 4.2). Note: the term port as used in this document refers to a HIPPI
 port and is roughly equivalent to the term "interface" as commonly
 used in other IP documents.
 Host
 An entity, usually a computer system, that may have one or more HIPPI
 ports and which may serve as a client or a HARP server.

Pittet Standards Track [Page 4] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

 Port
 An entity consisting of one HIPPI Source/Destination dual simplex
 pair that is connected by parallel or serial HIPPI to a HIPPI-SC
 switch and that transmits and receives IP datagrams.  A port may be
 an Internet host, bridge, router, or gateway.
 PIBES
 The Protocol for Internet Broadcast Emulation Server (see section 7).
 Source
 The HIPPI port that generates data to send to a HIPPI Destination.
 Universal LAN MAC Address (ULA)
 A 48-bit globally unique address, administered by the IEEE, assigned
 to each port on an Ethernet, FDDI, 802 network, or HIPPI-SC LAN.

3. IP Subnetwork Configuration

3.1 Background

 ARP (address resolution protocol) as defined in [14] was meant to
 work on the 'local' cable. This definition gives the ARP protocol a
 local logical IP subnet (LIS) scope. In the LIS scenario, each
 separate administrative entity configures its hosts and routers
 within the LIS. Each LIS operates and communicates independently of
 other LIS's on the same HIPPI-6400 network.
 HARP has LIS scope only and serves all ports in the LIS.
 Communication to ports located outside of the local LIS is usually
 provided via an IP router. This router is a HIPPI-6400 port attached
 to the HIPPI-6400 network that is configured as a member of one or
 more LIS's. This configuration MAY result in a number of disjoint
 LIS's operating over the same HIPPI-6400 network. Using this model,
 ports of different IP subnets SHOULD communicate via an intermediate
 IP router even though it may be possible to open a direct HIPPI-6400
 connection between the two IP members over the HIPPI-6400 network.
 This is an consequence of using IP and choosing to have multiple
 LIS's on the same HIPPI-6400 fabric.
 By default, the HARP method detailed in section 5 and the classical
 LIS routing model MUST be available to any IP member client in the
 LIS.

Pittet Standards Track [Page 5] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

3.2 HIPPI LIS Requirements

 The requirement for IP members (hosts, routers) operating in a
 HIPPI-6400 LIS configuration is:
 o  All members of the LIS SHALL have the same IP network/subnet
    address and address mask [4].
 The following list identifies the set of HIPPI-6400-specific
 parameters that MUST be implemented in each IP station connected to
 the HIPPI-6400 network:
 o  HIPPI-6400 Hardware Address:
    The HIPPI-6400 hardware address (a ULA) of an individual IP
    endpoint (i.e. a network adapter within a host) MUST be unique in
    the LIS.
 o  HARP Request Address List (HRAL):
 The HRAL is an ordered list of two or more addresses identifying the
 address resolution service(s).  All HARP clients MUST be configured
 identically, i.e. all ports MUST have the same addresses(es) in the
 HRAL.
 The HRAL MUST contain at least two HIPPI HW addresses identifying the
 individual HARP service(s) that have authoritative responsibility for
 resolving HARP requests of all IP members located within the LIS.  By
 default the first address MUST be the reserved address for broadcast,
 i.e. FF:FF:FF:FF:FF:FF.
 The second address MUST be the standard HW address for the HARP
 server 00:10:3B:FF:FF:E0.
 Therefore, the HRAL entries are sorted in the following order:
 1st     : broadcast address            (FF:FF:FF:FF:FF:FF) REQUIRED
 2nd     : official HARP server address (00:10:3B:FF:FF:E0) REQUIRED
 3rd & on: any additional HARP server addresses will be     OPTIONAL
           sorted in decreasing order.
 Manual configuration of the addresses and address lists presented in
 this section is implementation dependent and beyond the scope of this
 memo.  However, prior to use by any service or operation detailed in
 this memo, clients MUST have HRAL address(es) configured as
 appropriate for their LIS.

Pittet Standards Track [Page 6] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

4. Internet Protocol

4.1 Packet format

 The HIPPI-6400 packet format for Internet datagrams [15] shall
 conform to the HIPPI-6400-PH standard [1].  The length of a HIPPI-
 6400-PH packet, including headers and trailing fill, shall be a
 multiple of 32 bytes as required by HIPPI-6400-PH.
 All IP Datagrams shall be carried on HIPPI-6400-PH Virtual Channel 1
 (VC1). Since HIPPI-6400-PH has a 32-byte granularity, IP Datagrams
 MUST be padded to a 32-byte granularity prior to sending. Added
 padding is transparent to IP and is not reflected in the length field
 of the IP header.
 D_ULA   Destination ULA SHALL be the ULA of the destination port.
 S_ULA   Source ULA SHALL be the ULA of the requesting port.
 M_len   Set to the IEEE 802 packet (e.g. IP or HARP message)
         length + 8 Bytes to account for the LLC/SNAP header length.
         The HIPPI-6400-PH [1] length parameter shall not include
         the pad.

4.1.1 IEEE 802.2 LLC

 The IEEE 802.2 LLC Header SHALL begin in the first byte after M_len.
 The LLC values (in hexadecimal and decimal) SHALL be
 SSAP           0xAA     170  (8  bits)
 DSAP           0xAA     170  (8  bits)
 CTL            0x03       3  (8  bits)
 for a total length of 3 bytes. The 0x03 CTL value indicates the
 presence of a SNAP header.

4.1.2 SNAP

 The OUI value for Organization Code SHALL be 0x00-00-00 (3 bytes)
 indicating that the following two-bytes is an Ethertype.
 The Ethertype value SHALL be set as defined in Assigned Numbers [18]:
 IP           0x0800  2048  (16 bits)
 HARP = ARP = 0x0806  2054  (16 bits)
 The total size of the LLC/SNAP header is fixed at 8 bytes.

Pittet Standards Track [Page 7] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

4.1.3 HIPPI-6400 802 Packet diagrams

 The following diagram shows a HIPPI-6400 message carrying IEEE 802
 data.
 |31          |23          |15          |7          0|
 +------------+------------+------------+------------+ -------------

0 | |

 |         D_ULA           +-------------------------+   HIPPI-6400

1 | | |

 +-------------------------+        S_ULA            |      MAC

2 | |

 +---------------------------------------------------+     header

3 | M_len |

 +------------+------------+------------+------------+ -------------

4 | DSAP | SSAP | Ctl | Org | IEEE 802

 +------------+------------+------------+------------+    LLC/SNAP

5 | Org | Org | Ethertype | header

 +============+============+============+============+ =============

6 | Msg byte 0 | Msg byte 1 | Msg byte 2 | . . . | IEEE 802

 +---------------------------------------------------+      Data
                 Generic 802.1 data packet diagram
 The following diagram shows an IP datagram of length n with the FILL
 bytes ( value: 0x0 ). "<><>" indicates the micropacket separation. A
 HIPPI-6400-PH [1] micropacket is 32 bytes long.
 All IP (v4) [15] packets will always span two or more micropackets.
 The first micropacket has a TYPE = header. The second and any further
 micropackets have a TYPE = Data (see [1]).

Pittet Standards Track [Page 8] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

  |31          |23          |15          |7          0|
  +------------+------------+------------+------------+ -------------
0 |                                                   |
  |         D_ULA           +-------------------------+   HIPPI-6400
1 |                         |                         |
  +-------------------------+        S_ULA            |      MAC
2 |                                                   |
  +---------------------------------------------------+     header
3 |                      M_len                        |
  +------------+------------+------------+------------+ -------------
4 |     AA     |     AA     |     03     |    00      |    IEEE 802
  +------------+------------+------------+------------+    LLC/SNAP
5 |     00     |     00     | Ethertype = 0x0800=2048 |     header
  +============+============+============+============+ =============
6 | VER | HLEN |    TOS     |      Total Length       |
  +-----+------+------------+-----+-------------------+
7 |           ID            | FLG |   Frag Offset     |
  +<><><><><><>+<><><><><><>+<><><><><><>+<><><><><><>+  IPv4 Header
8 |    TTL     |   PROTO    |    Header Checksum      |
  +------------+------------+-------------------------+
9 |                 Source IP Address                 |
  +---------------------------------------------------+

10 | Destination IP Address |

  +---------------------------------------------------+

11 | . . . |

  +---------------------------------------------------+
  |   . . .    | byte (n-2) | byte (n-1) |    FILL    |
  +------------+------------+------------+------------+
  |    FILL    |   FILL     |   FILL     |    FILL    |
  +------------+------------+------------+------------+

M-1| FILL | FILL | FILL | FILL |

  +<><><><><><>+<><><><><><>+<><><><><><>+<><><><><><>+
                     IP v4 data packet diagram
 As shown in above figure the first eight bytes of the IP Datagram
 occupy the last eight bytes of the HIPPI-6400-PH [1] Header
 micropacket.

4.2 HIPPI-6400 Hardware address: Universal LAN MAC address (ULA)

 HIPPI-6400 uses Universal LAN MAC Addresses specified in IEEE
 Standard 802.1A [10] or a subset as defined in HIPPI-6400-SC [2].
 The globally unique part of the 48 bit space is administered by the
 IEEE. Each port on a HIPPI-6400-SC LAN MUST be assigned a ULA.
 Multiple ULAs may be used if a node contains more than one IEEE 802.2
 LLC protocol entity.

Pittet Standards Track [Page 9] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

 This memo assumes the use of "Logical Addressing" as described in
 Annex A.2 of HIPPI-6400-SC[2].
 The format of the address within its 48 bit HIPPI-6400-PH fields
 follows IEEE 802.1A canonical bit order and HIPPI-6400-PH bit and
 byte order:
  31              23              15               7              0
 +---------------+---------------+---------------+---------------+
 |ULA byte 0 |L|G|   ULA byte 1  |   ULA byte 2  |   ULA byte 3  |
 +---------------+---------------+---------------+---------------+
 |   ULA byte 4  |   ULA byte 5  |      (not used for ULA)       |
 +---------------+---------------+---------------+---------------+
                   Universal LAN MAC Address Format
 L (U/L bit) = 1 for Locally administered addresses, 0 for Universal.
 G (I/G bit) = 1 for Group addresses, 0 for Individual.

4.3 Maximum Transmission Unit - MTU

 Maximum Transmission Unit (MTU) is defined as the maximum length of
 the IP packet, including IP header, but not including any overhead
 below IP, i.e., HIPPI-6400 MAC header and IEEE 802 LLC/SNAP header.
 Conventional LANs have MTU sizes determined by physical layer
 specification.  MTUs may be required simply because the chosen medium
 won't work with larger packets, or they may serve to limit the amount
 of time a node must wait for an opportunity to send a packet.
 HIPPI-6400-PH [1] limits packets to about 4 gigabytes (on VC 3) which
 imposes no practical limit for networking purposes. HIPPI-6400-PH VC
 1, which was chosen for IP and ARP traffic, limits messages to about
 128 Kbytes which is still larger than the HIPPI-800 MTU [17].
 The MTU for HIPPI-6400 LANs SHALL be 65280 (decimal) bytes.
 This value is backwards compatible with HIPPI-800. It allows the IP
 packet to fit in one 64K byte buffer with up to 256 bytes of
 overhead.  The IP v4 overhead is 24 bytes for HIPPI-6400 and 40 bytes
 for HIPPI-800.

Pittet Standards Track [Page 10] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

 For HIPPI-6400 the byte accounting is:
    HIPPI-6400-PH Header            16 bytes
    IEEE 802.2 LLC/SNAP Headers      8 bytes
    Maximum IP packet size (MTU) 65280 bytes
    Unused expansion room          232 bytes
                                 ------------
                      Total      65536 bytes (64K)
 In contrast, the HIPPI-800 accounting is:
    HIPPI-800-FP Header              8 bytes
    HIPPI-800-LE Header             24 bytes
    IEEE 802.2 LLC/SNAP Headers      8 bytes
    Unused expansion room          216 bytes
    Maximum IP packet size (MTU) 65280 bytes
                                 ------------
                      Total      65536 bytes (64K)

5. HIPPI Address Resolution Protocol - HARP

 Address resolution within the HIPPI-6400 LIS SHALL make use of the
 HIPPI Address Resolution Protocol (HARP) and the Inverse HIPPI
 Address Resolution Protocol (InHARP). HARP provides the same
 functionality as the Internet Address Resolution Protocol (ARP).
 HARP is based on ARP which is defined in RFC-826 [14] except the
 HIPPI-6400 specific packet format. Knowing the Internet address,
 conventional networks use ARP to discover another node's hardware
 address.  HARP presented in this section further specifies the
 combination of the original protocol definitions to form a coherent
 address resolution service that is independent of the hardware's
 broadcast capability.  InHARP is the same protocol as the original
 Inverse ARP (InARP) protocol presented in [5] except the HIPPI-6400
 specific packet format.  Knowing its hardware address, InARP is used
 to discover the other party's Internet address.
 This memo further REQUIRES the PIBES (see section 7) extension to the
 HARP protocol, guaranteeing broadcast service to upper layer
 protocols like IP.
 Internet addresses are assigned independent of ULAs.  Before using
 HARP, each node MUST know its IP and its HW addresses. The ULA is
 optional but is RECOMMENDED if interoperability with conventional
 networks is desired.

Pittet Standards Track [Page 11] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

 If all switches in the LIS support broadcast, then the source address
 in the reply will be the target's source address.  If all switches in
 the LIS do not support broadcast, then a HARP server MUST be used to
 provide the address resolution service, and the source address in the
 reply will be the HARP server's source address.

5.1 HARP Algorithm

 This section defines the behavior and requirements for HARP
 implementations on both broadcast and non-broadcast capable HIPPI-
 6400-SC networks. HARP creates a table in each port which maps remote
 ports' IP addresses to ULAs, so that when an application requests a
 connection to a remote port by its IP address, the remote ULA can be
 determined, a correct HIPPI-6400-PH header can be built, and a
 connection to the port can be established using the ULA.
 HARP is a two phase protocol. The first phase is the registration
 phase and the second phase is the operational phase. In the
 registration phase the port detects if it is connected to broadcast
 hardware or not. The InHARP protocol is used in the registration
 phase.  In case of non-broadcast capable hardware, the InHARP
 Protocol will register and establish a table entry with the server.
 The operational phase works much like conventional ARP with the
 exception of the message format.

5.1.1 Selecting the authoritative HARP service

 Within the HIPPI LIS, there SHALL be an authoritative HARP service.
 To select the authoritative HARP service, each port needs to
 determine if it is connected to a broadcast network. At each point in
 time there is only one authoritative HARP service.
 The port SHALL send an InHARP_REQUEST to the first address in the
 HRAL (FF:FF:FF:FF:FF:FF). If the port sees its own InHARP_REQUEST,
 then it is connected to a broadcast capable network. In this case,
 the rest of the HRAL is ignored and the authoritative HARP service is
 the broadcast entry.
 If the port is connected to a non-broadcast capable network, then the
 port SHALL send the InHARP_REQUEST to all of the remaining entries in
 the HRAL. Every address which sends an InHARP_REPLY is considered to
 be a responsive HARP server. The authoritative HARP service SHALL be
 the HARP server which appears first in the HRAL.
 The order of addresses in the HRAL is only important for deciding
 which address will be the authoritative one. On a non-broadcast
 network, the port is REQUIRED to keep "registered" with all HARP
 server addresses in the HRAL (NOTE: not the broadcast address since

Pittet Standards Track [Page 12] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

 it is not a HARP server address). If for instance the authoritative
 HARP service is non-responsive,  then the port will consider the next
 address in the HRAL as a candidate for the authoritative address and
 send an InHARP_REQUEST.
 The authoritative HARP server SHOULD be considered non-responsive
 when it has failed to reply to: (1) one or more registration requests
 by the client (see section 5.1.2 and 5.2), (2) any two HARP_REQUESTs
 in the last 120 seconds or (3) if an external agent has detected
 failure of the authoritative HARP server. The details of such an
 external agent and its interaction with the HARP client are beyond
 the scope of this document. Should an authoritative HARP server
 become non-responsive, then the registration process SHOULD be
 restarted. Alternative methods for choosing an authoritative HARP
 service are not prohibited.

5.1.2 HARP registration phase

 HARP clients SHALL initiate the registration phase by sending an
 InHARP_REQUEST message using the HRAL addresses in order. The client
 SHALL terminate the registration phase and transition into the
 operational phase, when either: (1) it receives its own
 InHARP_REQUEST, or (2) when it receives an InHARP_REPLY from at least
 one of the HARP servers and it has determined the authoritative HARP
 service as described in 5.1.1.
 When ports are initiated they send an InHARP_REQUEST to the
 authoritative HRAL address. The first address to be tried will be the
 broadcast address "FF:FF:FF:FF:FF:FF". There are two outcomes:
 1. The port sees its own InHARP_REQUEST: then the port is connected
    to a broadcast capable network. The first address becomes, and
    remains, the authoritative address for the HARP service.
 2. The port does not receive its InHARP_REQUEST: then the port is
    connected to a non-broadcast capable network.
    The port SHALL choose the next address in the HRAL as a candidate
    for a HARP server and send an InHARP_REQUEST to that address:
    (00:10:3B:FF:FF:E0).
    The port SHALL continue to retry each non-broadcast HARP server
    address in the HRAL at least once every 5 seconds until one of the
    following termination criteria are met for each address.
    a. If the port receives its own message, then the port itself is
       the HARP server and the port is REQUIRED to provide broadcast
       services using the PIBES (see section 7).

Pittet Standards Track [Page 13] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

    b. If the port receives an InHARP_REPLY, then it is a HARP client
       and not a HARP server. In both cases, the current candidate
       address becomes the authoritative HARP service address.
 InHARP is an application of the InARP protocol for a purpose not
 originally intended.  The purpose is to accomplish registration of
 port IP address mappings with a HARP server if one exists or detect
 hardware broadcast capability.
 If the HIPPI-6400-SC LAN supports broadcast, then the client will see
 its own InHARP_REQUEST message and SHALL complete the registration
 phase. The client SHOULD further note that it is connected to a
 broadcast capable network and use this information for aging the HARP
 server entry and for IP broadcast emulation as specified in sections
 5.4 and 5.6 respectively.
 If the client doesn't see its own InHARP_REQUEST it SHALL await an
 InHARP_REPLY before completing the registration phase. This will also
 provide the client with the protocol address by which the HARP server
 is addressable.  This will be the case when the client happens to be
 connected to a non-broadcast capable HIPPI-6400-SC network.

5.1.3 HARP operational phase

 Once a HARP client has completed its registration phase it enters the
 operational phase. In this phase of the protocol, the HARP client
 SHALL gain and refresh its own HARP table information about other IP
 members by sending of HARP_REQUESTs to the authoritative address in
 the HRAL and by receiving of HARP_REPLYs. The client is fully
 operational during the operational phase.
 In the operational phase, the client's behavior for requesting HARP
 resolution is the same for broadcast or non-broadcast HIPPI-6400-SC
 switched networks.
 The target of an address resolution request updates its address
 mapping tables with any new information it can find in the request.
 If it is the target port it SHALL formulate and send a reply message.
 A port is the target of an address resolution request if at least ONE
 of the following statements is true of the request:
 1. The port's IP address is in the target protocol address field
    (ar$tpa) of the HARP message.
 2. The port's ULA, is in the ULA part of the Target Hardware Address
    field (ar$tha) of the message.
 3. The port is a HARP server.

Pittet Standards Track [Page 14] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

 NOTE: It is REQUIRED to have a HARP server run on a port that has a
 non-zero ULA.

5.2 HARP Client Operational Requirements

 The HARP client is responsible for contacting the HARP server(s) to
 have its own HARP information registered and to gain and refresh its
 own HARP entry/information about other IP members. This means, as
 noted above, that HARP clients MUST be configured with the hardware
 address  of the HARP server(s) in the HRAL.
 HARP clients MUST:
 1. When an interface is enabled (e.g. "ifconfig <interface> up" with
    an IP address) or assigned the first or an additional IP address
    (i.e. an IP alias), the client SHALL initiate the registration
    phase.
 2. In the operational phase the client MUST respond to HARP_REQUEST
    and InHARP_REQUEST messages if it is the target port.  If an
    interface has multiple IP addresses (e.g., IP aliases) then the
    client MUST cycle through all the IP addresses and generate an
    InHARP_REPLY for each such address. In that case an InHARP_REQUEST
    will have multiple replies. (Refer to Section 7, "Protocol
    Operation" in RFC-1293 [5].)
 3. React to address resolution reply messages appropriately to build
    or refresh its own client HARP table entries. All solicited and
    unsolicited HARP_REPLYs from the authoritative HARP server SHALL
    be used to update and refresh its own client HARP table entries.
    Explanation: This allows the HARP server to update the clients
    when one of server's mappings change, similar to what is
    accomplished on Ethernet with gratuitous ARP.
 4. Generate and transmit InHARP_REQUEST messages as needed and
    process InHARP_REPLY messages appropriately (see section 5.1.3 and
    5.6). All InHARP_REPLY messages SHALL be used to build/refresh its
    client HARP table entries.  (Refer to Section 7, "Protocol
    Operation" in [5].)
 If the registration phase showed that the hardware does not support
 broadcast, then the client MUST refresh its own entry for the HARP
 server, created during the registration phase, at least once every 15
 minutes. This can be accomplished either through the exchange of a
 HARP request/reply with the HARP server or by repeating step 1. To
 decrease the redundant network traffic, this timeout SHOULD be reset
 after each HARP_REQUEST/HARP_REPLY exchange.

Pittet Standards Track [Page 15] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

 Explanation: The HARP_REQUEST shows the HARP server that the client
 is still alive. Receiving a HARP_REPLY indicates to the client that
 the server must have seen the HARP_REQUEST.
 If the registration phase showed that the underlying network supports
 broadcast, then the refresh sequence is NOT REQUIRED.

5.3 Receiving Unknown HARP Messages

 If a HARP client receives a HARP message with an operation code
 (ar$op) that it does not support, it MUST gracefully discard the
 message and continue normal operation.  A HARP client is NOT REQUIRED
 to return any message to the sender of the undefined message.

5.4 HARP Server Operational Requirements

 A HARP server MUST accept HIPPI-6400 connections from other HIPPI-
 6400 ports. The HARP server expects an InHARP_REQUEST as the first
 message from the client. A server examines the IP address, the
 hardware address of the InHARP_REQUEST and adds or updates its HARP
 table entry <IP address(es), ULA> as well as the time stamp.
 A HARP server replies to HARP_REQUESTs and InHARP_REQUESTs based on
 the information which it has in its table. The HARP server replies
 SHALL contain the hardware type and corresponding format of the
 request (see also sec. 6).
 The following table shows all possible source address combinations on
 an incoming message and the actions to be taken. "linked" indicates
 that an existing "IP entry" is linked to a "hardware entry". It is
 possible to have an existing "IP entry" and to have an existing
 "hardware entry" but neither is linked to the other.
    +---+----------+----------+------------+---------------------+
    | # | IP entry | HW entry |  misc      |       Action        |
    +---+----------+----------+------------+---------------------+
    | 1 |  exists  |  exists  |     linked | *                   |
    | 2 |  exists  |  exists  | not linked | *, a, b,       e, f |
    | 3 |  exists  |    new   | not linked | *, a, b, d,    e, f |
    | 4 |   new    |  exists  | not linked | *,       c,    e, f |
    | 5 |   new    |    new   | not linked | *,       c, d, e, f |
    +---+----------+----------+------------+---------------------+
    Actions:
    *: update timeout value
    a: break the existing IP -> hardware (HW) -old link
    b: delete HW(old) -> IP link and decrement HW(old) refcount,
       if refcount = 0, delete HW(old)
    c: create new IP entry

Pittet Standards Track [Page 16] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

    d: create new HW entry
    e: add new IP -> HW link to IP entry
    f: add new HW -> IP link to HW entry
 Examples of when this could happen (Numbers match lines in above
 table):
 1: supplemental message
    Just update timer.
 2: move an IP alias to an existing interface
    If the IP source address of the InHARP_REQUEST duplicates a table
    entry IP address (e.g. IPa <-> HWa) and the InHARP_REQUEST
    hardware source address matches a hardware address entry (e. g.
    HWb <-> IPb), but they are not linked together, then:
  1. HWa entry needs to have its reference to the current IPa

address removed.

  1. HWb needs to have a new reference to IPa added
  2. IPa needs to be linked to HWb
    The result will be a table with: IPb <-> HWa <-> IPb  If IPb was
    the only IP address referred to by the HWb entry, then delete the
    HWb entry.
 3: move IP address to a new interface
    If the InHARP_REQUEST requester's IP source address duplicates a
    table entry IP address and the InHARP_REQUEST hardware source
    address does not match the table entry hardware address, then a
    new HW entry SHALL be created. The requestor's IP address SHALL be
    moved from the original HW entry to the new one (see above).
 4: add IP alias to table
    If the InHARP_REQUEST requester's hardware source address
    duplicates a hardware source address entry, but there is no IP
    entry matching the received IP address, then the IP address SHALL
    be added to the hardware entries previous IP address(es). (E.g.
    adding an IP alias).
 5: fresh entry, add it
    Standard case, create both entries and link them.

Pittet Standards Track [Page 17] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

 A server MUST update the HARP table entry's timeout for each
 HARP_REQUEST. Explanation: if the client is sending HARP requests to
 the server, then the server should note that the client is still
 "alive" by updating the timeout on the client's HARP table entry.
 A HARP server SHOULD use the PIBES (see sect. 7) to send out
 HARP_REPLYs to all hardware addresses in its table when the HARP
 server table changes mappings. This feature decreases the time of
 stale entries in the clients.
 If there are multiple addresses in the HRAL, then a server needs to
 act as a client to the other servers.

5.5 HARP and Permanent ARP Table Entries

 An IP station MUST have a mechanism (e.g. manual configuration) for
 determining what permanent entries it has. The details of the
 mechanism are beyond the scope of this memo.  The permanent entries
 allow interoperability with legacy HIPPI adapters which do not yet
 implement dynamic HARP and use a table based static ARP. Permanent
 entries are not aged.
 The HARP server SHOULD use the static entries to resolve incoming
 HARP_REQUESTs from the clients. This feature eliminates the need for
 maintaining a static HARP table on the client ports.

5.6 HARP Table Aging

 HARP table aging MUST be supported since IP addresses, especially IP
 aliases and also interfaces (with their ULA), are likely to move.
 When so doing the mapping in the clients own HARP table/cache becomes
 invalid and stale.
 o  When a client's HARP table entry ages beyond 15 minutes, a HARP
    client MUST invalidate the table entry.
 o  When a server's HARP table entry ages beyond 20 minutes, the HARP
    server MUST delete the table entry.
 NOTE: the client SHOULD revalidate a HARP table entry before it ages,
 thus restarting the aging time when the table entry is successfully
 revalidated.  The client MAY continue sending traffic to the port
 referred to by this entry while revalidation is in progress, as long
 as the table entry has not aged. The client MUST revalidate the
 invalidated entry prior to transmitting any non-address resolution
 traffic to the port referred to by this entry.

Pittet Standards Track [Page 18] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

 The client revalidates the entry by querying the HARP server.  If a
 valid reply is received (e.g. HARP_REPLY), the entry is updated.  If
 the address resolution service cannot resolve the entry (e.g.
 HARP_NAK, "host not found"), the associated table entry is removed.
 If the address resolution service is not available (i.e. "server
 failure") the client MUST attempt to revalidate the entry by
 transmitting an InHARP_REQUEST to the hardware address of the entry
 in question and updating the entry on receipt of an InHARP_REPLY. If
 the InHARP_REQUEST attempt fails to return an InHARP_REPLY, the
 associated table entry is removed.

6. HARP Message Encoding

 The HARP message is another type of IEEE 802 payload as described in
 section 4.1.3 above. The HIPPI-6400 HARP SHALL support two packet
 formats, both the generic Ethernet ARP packet and the HIPPI-800 HARP
 packet format defined in [13]. HARP messages SHALL be transmitted
 with a hardware type code of 28 on non-broadcast capable hardware or
 1 in either case.
 The ar$hrd field SHALL be used to differentiate between the two
 packet formats. The reply SHALL be in the format of the request.

6.1 Generic IEEE 802 ARP Message Format

 This is the ARP packet format used by conventional IEEE 802 networks
 (i.e. Ethernet, etc). The packet format is described in RFC-826 [14]
 and is given here only for completeness purpose.
   ar$hrd  16 bits  Hardware type
   ar$pro  16 bits  Protocol type of the protocol fields below
   ar$hln   8 bits  byte length of each hardware address
   ar$pln   8 bits  byte length of each protocol address
   ar$op   16 bits  opcode (ares_op$REQUEST | ares_op$REPLY)
   ar$sha  48 bits  Hardware address of sender of this packet
   ar$spa  32 bits  Protocol address of sender of this packet
   ar$tha  48 bits  Hardware address of target of this
   ar$tpa  32 bits  Protocol address of target.
 Where:
   ar$hrd  - SHALL contain 1. (Ethernet)
   ar$pro  - SHALL contain the IP protocol code 2048 (decimal).
   ar$hln  - SHALL contain 6.
   ar$pln  - SHALL contain 4.

Pittet Standards Track [Page 19] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

   ar$op   - SHALL contain the operational value (decimal):
             1  for   HARP_REQUESTs
             2  for   HARP_REPLYs
             8  for InHARP_REQUESTs
             9  for InHARP_REPLYs
             10 for   HARP_NAK
   ar$rpa  - in requests and NAKs it SHALL contain the requester's IP
             address if known, otherwise zero.
             In other replies it SHALL contain the target
             port's IP address.
   ar$sha  - in requests and NAKs it SHALL contain the requester's ULA
             In replies it SHALL contain the target port's ULA.
   ar$spa  - in requests and NAKs it SHALL contain the requester's IP
             address if known, otherwise zero.
             In other replies it SHALL contain the target
             port's IP address.
   ar$tha  - in requests and NAKs it SHALL contain the target's ULA
             if known, otherwise zero.
             In other replies it SHALL contain the requester's ULA.
   ar$tpa  - in requests and NAKs it SHALL contain the
             target's IP address if known, otherwise zero.
             In other replies it SHALL contain the requester's
             IP address.

Pittet Standards Track [Page 20] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

 |31             |23             |15             |7             0|
 +---------------+---------------+---------------+---------------+-----

0 | |

 |         D_ULA                 +-------------------------------+HIPPI

1 | | |6400

 +-------------------------------+            S_ULA              |MAC

2 | |hdr

 +---------------------------------------------------------------+

3 | M_len |

 +---------------+---------------+---------------+---------------+-----

4 | AA | AA | 03 | 00 |IEEE

 +---------------+---------------+---------------+---------------+802

5 | 00 | 00 | Ethertype = 0x0800 = 2048 |LLC/

 +------------+------------------+-------------------------------+SNAP

6 | hrd (1) | pro (2048) |

 +---------------+---------------+---------------+---------------+

7 | hln (6) | phl (4) | op (ar$op) |

 +<><><><><><><><+><><><><><><><>+<><><><><><><><+><><><><><><><>+

8 | Source Hardware Address 0 - 3 |

 +-------------------------------+-------------------------------+

9 | Source ULA bytes 4 - 5 | Source IP Address bytes 0 - 1 |

 +-------------------------------+-------------------------------+

10 | Source IP Address bytes 2 - 3 | Target ULA bytes 0 - 1 |

 +-------------------------------+-------------------------------+

11 | Target Hardware Address (ULA) bytes 2 - 5 |

 +---------------------------------------------------------------+

12 | Target IP Address |

 +---------------+---------------+---------------+---------------+

13 | FILL | FILL | FILL | FILL |

 +---------------+---------------+---------------+---------------+

14 | FILL | FILL | FILL | FILL |

 +><><><><><><><>+<><><><><><><><+><><><><><><><>+<><><><><><><><+

6.2 HIPARP Message Formats

 The HARP protocols further SHALL support the HIPARP hardware type
 (ar$hrd) = 28 (dec) [18], protocol type (ar$pro), and operation code
 (ar$op) data formats as the ARP, and InARP protocols [14,7]. In
 addition, HARP makes use of an additional operation code for ARP_NAK
 introduced with [11]. The remainder of the HIPARP message format
 (defined in [13]) is different than the ARP/InARP message format
 defined in [14,7,10] and it is also different from the format defined
 in the first "IP and ARP on HIPPI" RFC-1374 [16].
 The HARP message has several fields that have the following format
 and values:

Pittet Standards Track [Page 21] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

 Data sizes and field meaning:
   ar$hrd  16 bits  Hardware type
   ar$pro  16 bits  Protocol type of the protocol fields below
   ar$op   16 bits  Operation code (request, reply, or NAK)
   ar$pln   8 bits  byte length of each protocol address
   ar$rhl   8 bits  requester's HIPPI hardware address length (q)
   ar$thl   8 bits  target's HIPPI hardware address length (x)
   ar$rpa  32 bits  requester's protocol address
   ar$tpa  32 bits  target's protocol address
   ar$rha  qbytes   requester's HIPPI Hardware address
   ar$tha  xbytes   target's HIPPI Hardware address
 Where :
   ar$hrd  - SHALL contain 28. (HIPARP)
   ar$pro  - SHALL contain the IP protocol code 2048 (decimal).
   ar$op   - SHALL contain the operational value (decimal):
             1  for   HARP_REQUESTs
             2  for   HARP_REPLYs
             8  for InHARP_REQUESTs
             9  for InHARP_REPLYs
             10 for   HARP_NAK
   ar$pln  - SHALL contain 4.
   ar$rln  - SHALL contain 10 IF this is a HIPPI-800 HW address
             ELSE, for HIPPI-6400, it SHALL contain 6.
   ar$thl  - SHALL contain 10 IF this is a HIPPI-800 HW address
             ELSE, for HIPPI-6400, it SHALL contain 6.
   ar$rha  - in requests and NAKs it SHALL contain the requester's
             HW address.
             In replies it SHALL contain the target port's HW address.
   ar$rpa  - in requests and NAKs it SHALL contain the requester's IP
             address if known, otherwise zero.
             In other replies it SHALL contain the target
             port's IP address.
   ar$tha  - in requests and NAKs it SHALL contain the target's
             HW address if known, otherwise zero.
             In other replies it SHALL contain the requester's
             HW address.

Pittet Standards Track [Page 22] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

   ar$tpa  - in requests and NAKs it SHALL contain the
             target's IP address if known, otherwise zero.
             In other replies it SHALL contain the requester's
             IP address.
                Payload Format for HARP/InHARP PDUs:
 |31             |23             |15             |7             0|
 +---------------+---------------+---------------+---------------+-----

0 | |

 |         D_ULA                 +-------------------------------+HIPPI

1 | | |6400

 +-------------------------------+            S_ULA              |MAC

2 | |hdr

 +---------------------------------------------------------------+

3 | M_len |

 +---------------+---------------+---------------+---------------+-----

4 | AA | AA | 03 | 00 |IEEE

 +---------------+---------------+---------------+---------------+802

5 | 00 | 00 | Ethertype = 0x0800 = 2048 |LLC/

 +------------+------------------+-------------------------------+SNAP

6 | hrd (28) | pro (2048) |

 +---------------+---------------+---------------+---------------+

7 | op (ar$op) | pln (6) | shl (q) |

 +<><><><><><><><+><><><><><><><>+<><><><><><><><+><><><><><><><>+

8 | thl (x) | Source IP Address upper (24 bits) |

 +---------------------------------------------------------------+

9 | Src. IP lower | Target IP Address upper (24 bits) |

 +---------------+-----------------------------------------------+

10 | Tgt. IP lower | Source HW Address bytes 0 - 2 |

 +---------------+-------------------------------+---------------+

11 | Source HW Address bytes 3 - q | Tgt HW byte 0 |

 +-----------------------------------------------+---------------+

12 | Target Hardware Address bytes 1 - 4 |

 +---------------+-----------------------------------------------+

13 |Tgt HW byte 5-x|

 +---------------+
                        HARP - InHARP Message

6.2.1 Example Message encodings:

 Assume for the following example that the HARP server is in the
 HIPPI-6400 side and the clients, X and Y are on the HIPPI-800 side of
 the non-broadcast capable network.

Pittet Standards Track [Page 23] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

 HARP_REQUEST message
       HARP ar$op   = 1 (HARP_REQUEST)
       HARP ar$rpa  = IPy                HARP ar$tpa  = IPx
       HARP ar$rha  = SWy ULAy           HARP ar$tha  = **
       ** is what we would like to find out
 HARP_REPLY message format
       HARP ar$op   = 2 (HARP_REPLY)
       HARP ar$rpa  = IPx                HARP ar$tpa  = IPy
       HARP ar$rha  = SWx ULAx *         HARP ar$tha  = SWy ULAy
       * answer we were looking for
 InHARP_REQUEST message format
       HARP ar$op    = 8 (InHARP_REQUEST)
       HARP ar$rpa   = IPy               HARP ar$tpa   = 0 **
       HARP ar$rha   = SWy ULAy          HARP ar$tha   = SWx ULAx
       ** is what we would like to find out
 InHARP_REPLY message format
       HARP ar$op    = 9 (InHARP_REPLY)
       HARP ar$rpa   = IPx *             HARP ar$tpa   = IPy
       HARP ar$rha   = SWx ULAx          HARP ar$tha   = SWy ULAy
       * answer we were looking for

6.2.2 HARP_NAK message format

 The HARP_NAK message format is the same as the received HARP_REQUEST
 message format with the operation code set to HARP_NAK; i.e. the
 HARP_REQUEST message data is copied for transmission with the
 HARP_REQUEST operation code changed to the HARP_NAK value.  HARP
 makes use of an additional operation code for HARP_NAK and MUST be
 implemented.

7 Broadcast and Multicast

 HIPPI-6400-SC requires compliant systems to support broadcast.
 Initial HIPPI-6400-SC systems MAY defer broadcast capability to a
 broadcast server rather than support it directly in the switching
 mechanism.  A centralized HARP server architecture meets two of the
 three major duties of a broadcast server.
 A central entity serving the whole LIS solves the coordination
 problem of a distributed approach. The registration requirement
 solves the second problem of determining which addresses make up the
 set loosely called "everyone". The last duty of a broadcast server is
 to replicate an incoming packet and send it to "everyone".

Pittet Standards Track [Page 24] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

 During its registration phase, every port , including HARP server(s),
 discover if the underlying medium is capable of broadcast (see
 section 5.1.1). Should this not be the case, then the HARP server(s)
 MUST emulate broadcast through an IP broadcast emulation server.
 A HIPPI IP broadcast server (PIBES) is an extension to the HARP
 server and only makes sense when the LIS does not inherently support
 broadcast. The PIBES allows common upper layer networking protocols
 (RIP, TCP, UDP, etc.)to access IP LIS broadcast.

7.1 Protocol for an IP Broadcast Emulation Server - PIBES

 To emulate broadcast within an LIS, a PIBES SHALL use the currently
 valid HARP table of the HARP server as a list of addresses called the
 target list. The broadcast server SHALL validate that all incoming
 messages have a source address which corresponds to an address in the
 target list. Only messages addressed to the IP LIS broadcast
 addresses, multicast address or 255.255.255.255 are considered valid
 messages for broadcasting. Invalid messages MUST be dropped.  All
 valid incoming messages shall be forwarded to all addresses in the
 target list.
 It is RECOMMENDED that the broadcast server run on the same port as
 the HARP server since this memo does not define the protocol for
 exchanging the valid HARP table. The default address to use for the
 broadcast address is the operational HARP server address.

7.2 IP Broadcast Address

 This memo only defines IP broadcast. It is independent of the
 underlying hardware addressing and broadcast capabilities. Any port
 can differentiate between IP traffic directed to itself and a
 broadcast message sent to it by looking at the IP address. All IP
 broadcast messages SHALL use the IP LIS broadcast address.
 It is RECOMMENDED that the PIBES run on the same port as the HARP
 server. In that case, the PIBES SHALL use the same address as the
 HARP server.

7.3 IP Multicast Address

 HIPPI-6400 does not directly support multicast address, therefore
 there are no mappings available from IP multicast addresses to HIPPI
 multicast services.  Current IP multicast implementations (i.e. MBONE
 and IP tunneling, see [7]) will continue to operate over HIPPI-based
 logical IP subnets if all IP multicast packets are sent using the
 same algorithm as if the packet were being sent to 255.255.255.255.

Pittet Standards Track [Page 25] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

7.4 A Note on Broadcast Emulation Performance

 It is obvious that a broadcast emulation service (as defined in
 section 7.1) has an inherent performance limit. In an LIS with n
 ports, the upper bound on the bandwidth that such a service can
 broadcast is:
                        (total bandwidth)/(n+1)
 since each message must first enter the broadcast server, accounting
 for the additional 1, and then be sent to all n ports. The broadcast
 server could forward the message destined to the port on which it
 runs internally, thus reducing (n+1) to (n) in a first optimization.
 This service is adequate for the standard networking protocols such
 as RIP, OSPF, NIS, etc. since they usually use a small fraction of
 the network bandwidth for broadcast. For these purposes, the
 broadcast emulation server as defined in this memo allows the HIPPI-
 6400 network to look similar to an Ethernet network to the higher
 layers.
 It is further obvious that such an emulation cannot be used to
 broadcast high bandwidth traffic. For such a solution, hardware
 support for true broadcast is required.

8 HARP for Scheduled Transfer

 This RFC also applies for resolving addresses used with Scheduled
 Transfer (ST) over HIPPI-6400 instead of IP. This RFC's message types
 and algorithms can be used for ST (since ST uses Internet Addresses)
 as long as there is also an IP over HIPPI-6400 implementation on all
 the ports.

9 Security Consierations

 There are known security issues relating to port impersonation via
 the address resolution protocols used in the Internet [6].  No
 special security mechanisms have been added to the address resolution
 mechanism defined here for use with networks using HARP.
 Not all of the security issues relating to ARP over HIPPI-6400 are
 clearly understood at this time, due to the fluid state of HIPPI-6400
 specifications, newness of the technology, and other factors.
 However, given the security hole ARP allows, other concerns are
 probably minor.

Pittet Standards Track [Page 26] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

10 Open Issues

 Synchronization and coordination of multiple HARP servers and
 multiple broadcast servers are left for further study.

11 HARP Examples

 Assume a HIPPI-6400-SC switch is installed with three connected
 ports:  x, y, and a. Each port has a unique hardware address that
 consists unique ULA (ULAx, ULAy and UlAa, respectively). There is a
 HARP server connected to a switch port that is mapped to the address
 HWa, this address is the authoritative HIPPI hardware address in the
 HRAL (HARP Request Address List).
 The HARP server's table is empty. Ports X and Y each know their own
 hardware address.  Eventually they want to talk to each other; each
 knows the other's IP address (from the port database) but neither
 knows the other's ULA. Both ports X and Y have their interfaces
 configured DOWN.
 NOTE: The LLC, SNAP, Ethertype, ar$hrd, ar$pro, ar$pln fields are
 left out from the examples below since they are constant. As well as
 ar$rhl = ar$thl = 6 since these are all HIPPI-6400 examples.

11.1 Registration Phase of Client Y on Non-broadcast Hardware

 Port Y starts: its HARP table entry state for the server: PENDING
 1. Port Y initiates its interface and sends an InHARP_REQUEST to the
    HWa after starting a table entry for the HWa.
    HIPPI-6400-PH D_ULA                 = ULAa
    HIPPI-6400-PH S_ULA                 = ULAy
    HARP ar$op                          = 8 (InHARP_REQUEST)
    HARP ar$rpa                         = IPy
    HARP ar$tpa                         = 0 **
    HARP ar$rha                         = ULAy
    HARP ar$tha                         = ULAa
    ** is what we would like to find out
 2. HARP server receives Y's InHARP_REQUEST, it examines the source
    addresses and scans its tables for a match. Since this is the
    first time Y connects to this server there is no entry and one
    will be created and time stamped with the information from the
    InHARP_REQUEST. The HARP server will then send a InHARP_REPLY
    including its IP address.

Pittet Standards Track [Page 27] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

    HIPPI-6400-PH D_ULA                 = ULAy
    HIPPI-6400-PH S_ULA                 = ULAa
    HARP ar$op                          = 9 (InHARP_REPLY)
    HARP ar$rpa                         = IPs *
    HARP ar$tpa                         = IPy
    HARP ar$rha                         = ULAa
    HARP ar$tha                         = ULAy
    * answer we were looking for
 3. Port Y examines the incoming InHARP_REPLY and completes its table
    entry for the HARP server. The client's HARP table entry for the
    server now passes into the VALID state and is usable for regular
    HARP traffic. Receiving this reply ensures that the HARP server
    has properly registered the client.

11.2 Registration Phase of Client Y on Broadcast Capable Hardware

 If port Y is connected to a broadcast-capable network then the
 authoritative address is the broadcast address, HWb = SWb, ULAb
 (FF:FF:FF:FF:FF:FF).
 Port Y starts: its HARP table entry state for HWa: PENDING
 1. Port Y initiates its interface and sends an InHARP_REQUEST to HWa,
    in this example the broadcast address, after starting a table
    entry.
    HIPPI-6400-PH D_ULA                 = ULAb
    HIPPI-6400-PH S_ULA                 = ULAy
    HARP ar$op                          = 8 (InHARP_REQUEST)
    HARP ar$rpa                         = IPy
    HARP ar$tpa                         = 0 **
    HARP ar$rha                         = ULAy
    HARP ar$tha                         = ULAb
    ** is what we would like to find out
 2. Since the network is a broadcast network, client Y will receive a
    copy of its InHARP_REQUEST. Client Y examines the source
    addresses.  Since they are the same as what Y filled in the
    InHARP_REQUEST, Y can deduce that it is connected to a broadcast
    medium.  Port Y completes its table entry for HWa. This entry will
    not timeout since it is considered unlikely for a particular
    underlying hardware type to change between broadcast and non-
    broadcast; therefore this mapping will never change.

Pittet Standards Track [Page 28] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

11.3 Operational Phase (phase II)

 The Operational Phase of the HARP protocol as specified in this memo
 is the same for both broadcast and non-broadcast capable HIPPI-6400
 hardware. The authoritative address in the HRAL for this example will
 be HWa: <SWa, ULAa> and IPs for simplicity reasons.

11.3.1 Successful HARP_Resolve example

 Assume the same process (steps 1-3 of section 11.1) happened for port
 X. Then the state of X and Y's tables is: the HARP server table entry
 is in the VALID state. So lets look at the message traffic when X
 tries to send a message to Y. Since X doesn't have an entry for Y,
 1. Port X connects to the authoritative address of the HRAL and sends
    a HARP_REQUEST for Y's hardware address:
    HIPPI-6400-PH D_ULA                 = ULAa
    HIPPI-6400-PH S_ULA                 = ULAx
    HARP ar$op                          = 1  (HARP_REQUEST)
    HARP ar$rpa                         = IPx
    HARP ar$tpa                         = IPy
    HARP ar$rha                         = ULAx
    HARP ar$tha                         = 0 **
    ** is what we would like to find out
 2. The HARP server receives the HARP request and updates its entry
    for X if necessary. It then generates a HARP_REPLY with Y's
    hardware address information.
    HIPPI-6400-PH D_ULA                 = ULAx
    HIPPI-6400-PH S_ULA                 = ULAa
    HARP ar$op                          = 2  (HARP_Reply)
    HARP ar$rpa                         = IPy
    HARP ar$tpa                         = IPx
    HARP ar$rha                         = ULAy *
    HARP ar$tha                         = ULAx
    * answer we were looking for
 3. Port X connects to port Y and transmits an IP message with the
    following information in the HIPPI-LE header:
    HIPPI-6400-PH D_ULA                 = ULAy
    HIPPI-6400-PH S_ULA                 = ULAx
    <data>

Pittet Standards Track [Page 29] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

 If the network had been broadcast-capable, the target ports would
 themselves have received the HARP_REQUEST of step 2 above and
 responded to them in the same way the HARP server did.

11.3.2 Non-successful HARP_Resolve example

 As in 11.3.1, assume that X and Y are fully registered with the HARP
 server. Then the state of X and Y's HARP server table entry is:
 VALID. So lets look at the message traffic when X tries to send a
 message to Q. Further assume that interface Q is NOT configured UP,
 i.e. it is DOWN.  Since X doesn't have an entry for Q,
 1. Port X connects to the HARP server switch address and sends a
    HARP_REQUEST for Q's hardware address:
    HIPPI-6400-PH D_ULA                 = ULAa
    HIPPI-6400-PH S_ULA                 = ULAx
    HARP ar$op                          = 1  (HARP_REQUEST)
    HARP ar$rpa                         = IPx
    HARP ar$tpa                         = IPq
    HARP ar$rha                         = ULAx
    HARP ar$tha                         = 0 **
    ** is what we would like to find out
 2. The HARP server receives the HARP request and updates its entry
    for X if necessary. It then looks up IPq in its tables and doesn't
    find it. The HARP server then generates a HARP_NAK reply message.
    HIPPI-6400-PH D_ULA                 = ULAx
    HIPPI-6400-PH S_ULA                 = ULAa
    HARP ar$op                          = 10  (HARP_NAK)
    HARP ar$rpa                         = IPx
    HARP ar$tpa                         = IPq
    HARP ar$rha                         = ULAx
    HARP ar$tha                         = 0 ***
    *** No Answer, and notice that the fields do not get swapped,
        i.e. the HARP message is the same as the HARP_REQUEST
        except for the operation code.
 If the network had been broadcast-capable, then there would not have
 been a reply.

Pittet Standards Track [Page 30] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

12 References

 [1]  ANSI NCITS 323-1998, Information Technology - High-Performance
      Parallel Interface - 6400 Mbit/s Physical Layer (HIPPI-6400-PH).
 [2]  ANSI NCITS 324-199x, Information Technology - High-Performance
      Parallel Interface - 6400 Mbit/s Physical Switch Control
      (HIPPI-6400-SC).
 [3]  ANSI NCITS Project Number 1249-D, Information Technology -
      High-Performance Parallel Interface - 6400 Mbit/s Optical
      Specification (HIPPI-6400-OPT).
 [4]  Braden, R., "Requirements for Internet Hosts -- Communication
      Layers", STD 3, RFC 1122, October 1989.
 [5]  Bradely, T. and C. Brown, "Inverse Address Resolution Protocol",
      RFC 2390, September 1998.
 [6]  Bellovin, Steven M., "Security Problems in the TCP/IP Protocol
      Suite", ACM Computer Communications Review, Vol. 19, Issue 2,
      pp.  32-48, 1989.
 [7]  Deering, S, "Host Extensions for IP Multicasting", STD 5, RFC
      1112, August 1989.
 [8]  Chesson, Greg, "HIPPI-6400 Overview", IEEE Hot Interconnects
      1996, Stanford University.
 [10] ANSI/IEEE Std. 802.2-1989, Information Processing Systems -
      Local Area Networks - Logical Link Control IEEE, IEEE, New York,
      New York, 1989.
 [11] Laubach, M., "Classical IP and ARP over ATM", RFC 2225, April
      1998.
 [12] Mogul, J. and S. Deering, "Path MTU Discovery", RFC 1191,
      November, 1990.
 [13] Pittet, J.-M., "ARP and IP Broadcast over HIPPI-800", RFC 2834,
      May 2000.
 [14] Plummer, D., "An Ethernet Address Resolution Protocol - or -
      Converting Network Addresses to 48-bit Ethernet Address for
      Transmission on Ethernet Hardware", RFC-826, MIT, November 1982.

Pittet Standards Track [Page 31] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

 [15] Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981.
 [16] Renwick, J. and A. Nicholson, "IP and ARP on HIPPI", RFC 1374,
      October 1992.
 [17] Renwick, J., "IP over HIPPI", RFC 2067, January 1997.
 [18] Reynolds, J. and J. Postel, "Assigned Numbers", STD 2, RFC 1700,
      October 1994.
 [19] Bradner, S., "Key words for use in RFCs to Indicate Requirement
      Levels", BCP 14, RFC 2119, March 1997.

13 Acknowledgments

 This memo could not have come into being without the critical review
 from Greg Chesson, Carlin Otto, the High performance interconnect
 group of Silicon Graphics (specifically Jim Pinkerton, Brad Strand
 and Jeff Young) and the expertise of the ANSI T11.1 Task Group
 responsible for the HIPPI standards work.
 This memo is based on the second part of [17], written by John
 Renwick. ARP [14] written by Dave Plummer and Inverse ARP [7] written
 by Terry Bradley and Caralyn Brown provide the fundamental algorithms
 of HARP as presented in this memo. Further, the HARP server is based
 on concepts and models presented in [13], written by Mark Laubach who
 laid the structural groundwork for the HARP server.

14 Author's Address

 Jean-Michel Pittet
 Silicon Graphics Inc
 1600 Amphitheatre Parkway
 Mountain View, CA 94040
 Phone: 650-933-6149
 Fax:   650-933-3542
 EMail: jmp@sgi.com, jmp@acm.org

Pittet Standards Track [Page 32] RFC 2835 IP and ARP over HIPPI-6400 (GSN) May 2000

15 Full Copyright Statement

 Copyright (C) The Internet Society (2000).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Pittet Standards Track [Page 33]

/data/webs/external/dokuwiki/data/pages/rfc/rfc2835.txt · Last modified: 2000/05/18 17:46 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki