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rfc:rfc4678

Network Working Group A. Bivens Request for Comments: 4678 IBM Research Category: Informational September 2006

                Server/Application State Protocol v1

Status of This Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2006).

IESG Note

 This RFC is not a candidate for any level of Internet Standard.  The
 IETF disclaims any knowledge of the fitness of this RFC for any
 purpose and in particular notes that the decision to publish is not
 based on IETF review for such things as security, congestion control,
 or inappropriate interaction with deployed protocols.  The RFC Editor
 has chosen to publish this document at its discretion.  Readers of
 this document should exercise caution in evaluating its value for
 implementation and deployment.  See RFC 3932 for more information.

Abstract

 Entities responsible for distributing work across a group of systems
 traditionally do not know a great deal about the ability of the
 applications on those systems to complete the work in a satisfactory
 fashion.  Workload management systems traditionally know a great deal
 about the health of applications, but have little control over the
 rate in which these applications receive work.  The
 Server/Application State Protocol (SASP) provides a mechanism for
 load balancers and workload management systems to communicate better
 ways of distributing the existing workload to the group members.

Bivens Informational [Page 1] RFC 4678 SASPv1 September 2006

Table of Contents

 1. Introduction ....................................................3
    1.1. Overview ...................................................3
    1.2. Identities .................................................4
 2. Requirements Notation ...........................................4
 3. Conventions Used in This Document ...............................4
 4. General Message Structure .......................................4
    4.1. TLV Structure ..............................................6
    4.2. Component Types ............................................6
    4.3. SASP Protocol Header .......................................7
    4.4. Version Negotiation ........................................8
 5. Singular Protocol Components ....................................9
    5.1. Member Data Component ......................................9
    5.2. Group Data Component ......................................11
    5.3. Weight Entry Data Component ...............................12
    5.4. Member State Instance Component ...........................14
 6. Group Protocol Components ......................................15
    6.1. Group of Member Data Component ............................15
    6.2. Group of Weight Data Component ............................16
    6.3. Group of Member State Data Components .....................17
 7. Protocol Messages ..............................................17
    7.1. Registration Request and Reply ............................18
         7.1.1. Registration Request ...............................18
         7.1.2. Registration Reply .................................19
    7.2. DeRegistration Request and Reply ..........................20
         7.2.1. DeRegistration Request .............................21
         7.2.2. DeRegistration Reply ...............................22
    7.3. Get Weights Request and Reply .............................23
         7.3.1. Get Weights Request ................................24
         7.3.2. Get Weights Reply ..................................25
    7.4. Send Weights ..............................................26
    7.5. Set Member State Request and Reply ........................27
         7.5.1. Set Member State Request ...........................28
         7.5.2. Set Member State Reply .............................29
    7.6. Set Load Balancer State Request and Reply .................30
         7.6.1. Set LB State Request ...............................30
         7.6.2. Set LB State Reply .................................32
 8. Example of SASP Message Encoding ...............................32
 9. Protocol Flow ..................................................37
    9.1. Normal Protocol Flow ......................................37
    9.2. Behavior in Error Cases ...................................39
    9.3. Example Flow 1: Load Balancer Registration,
         Getting Weights, and Application-Side Quiescing ...........41
    9.4. Example Flow 2:  Set Load Balancer State, Application
         Registration, and Load Balancer Group DeRegistration ......43
    9.5. Avoiding Single Points of Failure .........................44

Bivens Informational [Page 2] RFC 4678 SASPv1 September 2006

 10. Security Considerations .......................................45
 11. Normative References ..........................................46
 Appendix A. Acknowledgements ......................................47

1. Introduction

1.1. Overview

 The Server/Application State Protocol is designed to enable load
 balancers or schedulers (1) to receive traffic weight recommendations
 from Workload Managers, (2) to register with Workload Managers
 members of load balancing/scheduling groups, and (3) to enable
 Workload Managers to suggest new load balancing group members to load
 balancers and schedulers
 The figure below shows where the SASP entities are in typical load
 balancing topology.
  1. ———

| Group |

  1. ——→|Member 1|←-|

| ———- |

                                 |                     |
   ---------        ----------   |        ----------   |
   |Request|<------>|  Load  |---|        | Group  |   |
   |Origins|<------>|Balancer|----------->|Member 2|<--|
   ---------        |        |---|        ----------   |
                    ----------   |                     |
                        ^        |        ----------   |
                        |        -------->| Group  |   |
                   SASP |                 |Member 3|<--|
                  -------                 ----------   |
                  |                                    |
                  |      --------------------          |
                  |      |     Group        |     SASP |
                  ------>| Workload Manager |<----------
                         --------------------
                               Figure 1
 SASP is a binary protocol that facilitates communication from load
 balancers/schedulers to Workload Managers.  The connection between
 the Group Workload Manager (GWM) and the load balancer/scheduler is
 expected to be a long-running TCP connection.  In SASP interactions,
 the GWM acts as a SASP server waiting to receive connections from the
 other SASP components.  Server port 3860 has been registered with the
 IANA for SASP communications.  It is expected that all SASP
 components are configured with the DNS name of the GWM to develop

Bivens Informational [Page 3] RFC 4678 SASPv1 September 2006

 this connection.  Security in SASP is handled by transporting binary
 messages over Secure Socket Layer/Transport Layer Security (SSL/TLS).
 This document only describes the message format and protocol behavior
 above the connection and security layers.  Connection and security
 aspects including SSL's authentication and encryption will be
 implementation specific.

1.2. Identities

 SASP identifies a load balancer by a UTF-8 string called a "LB UID".
 A group of "equivalent" servers providing a service is identified by
 a UTF-8 string called a "Group Name", which is interpreted in the
 context of the LB UID.  A server is identified by its IP address and
 (optional) port and protocol numbers.  A GWM is only identified
 implicitly as the entity on the other end of the TCP connection from
 a load balancer or group member.  All of these identifiers are local;
 there are no globally unique identifiers.  The LB UID and GroupName
 fields are unstructured so that components could assign values to
 these fields that are meaningful to an administrator.  For example,
 in many cases, a load balancer would use the name an administrator
 provided for the serverfarm group as the groupname in a SASP-
 specified group.  Since the naming options in industry load balancers
 do not carry explicit naming restrictions, SASP naming options also
 carry no naming restrictions.

2. Requirements Notation

 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. Conventions Used in This Document

 o  Load Balancer - Entity responsible for distributing requests
    amongst the available members.
 o  Member - Machine, process, or application used to service
    requests.
 o  Group Workload Manager (GWM) - Entity responsible for reporting or
    managing a group of members on multiple machines.

4. General Message Structure

 Any string interpreted by the group workload manager is assumed to
 use UTF8.  Components implementing SASP MUST support the printable
 ASCII subrepertoire of UTF8 (0x20-0x7E).  Components MAY also choose
 to provide support for additional UTF8 character encodings.  It is

Bivens Informational [Page 4] RFC 4678 SASPv1 September 2006

 recommended that customers using SASP-enabled products configure the
 string-generating components (load balancers and group members) to
 use the same character repertoire.
 Many of the SASP structures involve the transfer of multi-byte
 integer values.  In all cases where multi-byte integer values are
 used, they are considered to be in network-byte order (big-endian).
 SASP is organized into several message components.  For extendibility
 and ease of processing, each message component is described in a TLV
 (Type, Length, Value) format.  An illustration of the SASP structure
 can be found in the example below.  The first section is the header
 followed by the message component type.  As mentioned, the header,
 message component, and all other components have a TLV format.  Each
 component value contains a variable number of fields, some of which
 refer to upcoming components (explained component descriptions are in
 upcoming sections).  After the first message component, any number of
 additional components may be included (as stipulated in the fields of
 the message type).
  1. ————————————————

| |T| Type (SASP Header Type) |

 |    SASP    |----------------------------------|
 |   Header   |L| Length of SASP header TLV      |
 |            |----------------------------------|
 |            |V| Header fields                  |
 |-----------------------------------------------|
 |            |T| Type (Message Type)            |
 |  Message   |----------------------------------|
 |    Type    |L| Length of this Message Type TLV|
 | Component  |----------------------------------|
 |            |V| Component fields               |
 |-----------------------------------------------|
 |            |T| Type (Component Type)          |
 |            |----------------------------------|
 |Component-1 |L| Length of this TLV             |
 |            |----------------------------------|
 |            |V| Component fields               |
 |-----------------------------------------------|
 | ...                                           |
 |-----------------------------------------------|
 |            |T| Type (Component Type)          |
 |            |----------------------------------|
 |Component-n |L| Length of this TLV             |
 |            |----------------------------------|
 |            |V| Component fields               |
 -------------------------------------------------

Bivens Informational [Page 5] RFC 4678 SASPv1 September 2006

                               Figure 2

4.1. TLV Structure

 An illustration of the TLV format is shown below.  The Type is a
 two-byte field containing a binary value for the component type.  The
 Length is a two-byte field containing the size of the TLV in bytes
 (including the Type and Length fields).  The Value field is a
 variable-length field that actually contains the data of the
 component.
 < xxxx xxxx xxxx xxxx, xxxx xxxx xxxx xxxx, xxxx...........xxxx >
   |-----------------|  |-----------------|  |-----------------|
      Type(2 bytes)       Length(2 bytes)      Value(variable)
                               Figure 3

4.2. Component Types

 The TLV structure requires a type value for each protocol component.
 All SASP types are listed in this section.
    Reserved 0x0000-0x1000
    Message Types
       Registration Request 0x1010
       Registration Reply 0x1015
       DeRegistration Request 0x1020
       DeRegistration Reply 0x1025
       Get Weights Request 0x1030
       Get Weights Reply 0x1035
       Send Weights 0x1040
       Set Load Balancer State Request 0x1050
       Set Load Balancer State Reply 0x1055
       Set Member State Request 0x1060
       Set Member State Reply 0x1065

Bivens Informational [Page 6] RFC 4678 SASPv1 September 2006

    Utility Component Types
       SASP Header 0x2010
    Singular Component Types
       Member Data 0x3010
       Group Data 0x3011
       Weight Entry Data 0x3012
       Member State Instance 0x3013
    Group Component Types
       Group of Member Data 0x4010
       Group of Weight Entry Data 0x4011
       Group of Member State Data 0x4012
    Reserved 0xF000-0xFFFF

4.3. SASP Protocol Header

 An illustration of the SASP Header is found in the table below.  It
 is expected that every message will start with the SASP Protocol
 Header component.
    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   SASP header type (0x2010)   |       Size of this TLV        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    Version    |                     Message Length
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                    |                       Message ID
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                    |
    +-+-+-+-+-+-+-+-+
                               Figure 4
 o  Version: The version of the protocol used in this message.

Bivens Informational [Page 7] RFC 4678 SASPv1 September 2006

 o  Message Length: A 4-byte signed integer value representing the
    total length of the SASP message.  It is said to be a signed
    4-byte value to make any Java implementations easier (or any other
    implementations without unsigned values); however, no negative
    lengths are valid.
 o  Message ID: Each request message is given a 4-byte Message ID by
    the message originator, which is simply returned in the Message ID
    field of the reply.  This field is meant to assist the requester
    in correlating replies to the appropriate request when many
    requests have been sent.  In the Send Weights message (the only
    message transaction that has no reply), this field serves no
    purpose.

4.4. Version Negotiation

 To negotiate the version of the protocol used by the entities
 involved in the connection, the GWM views the version included in the
 load balancer request as the load balancer's proposed version.
 If the GWM supports the version proposed by the load balancer, it
 will respond to the connection with the appropriate response code and
 the load balancer's proposed version in the response header.  This
 proposed version should be the version used for all messages in this
 connection.
 If the GWM does not support the version proposed by the load
 balancer, the GWM will respond with a "message not understood"
 response code and the GWM's highest supported SASP version in the
 version field of the response header.  This is an indication for the
 load balancer to come down to GWM's SASP version level.

Bivens Informational [Page 8] RFC 4678 SASPv1 September 2006

5. Singular Protocol Components

 The most basic of SASP components are singular components because
 they describe a single instance of a member, member resource, member
 weight, or group.  Some of the SASP components reuse other SASP
 components.  When this is the case, any component being reused by a
 base component will simply be given immediately following the base
 component.  Some examples of this technique are seen and explained in
 the Weight Entry and Member State Instance components.

5.1. Member Data Component

 The member data component describes a particular member and is
 referred to by other components.
    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Member Data Type (0x3010)   |       Size of this TLV        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Protocol    |             Port              |               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               +
    |                                                               |
    +                                                               +
    |                                                               |
    +                   IP Address of Member                        +
    |                                                               |
    +                                               +-+-+-+-+-+-+-+-+
    |                                               |  Label Length |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    .                                                               .
    .                          Label                                .
    .                                                               .
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                               Figure 5
 o  Protocol: The assigned number of the IP transport layer used in
    the Protocol Field of the IP header.  These are defined in
    [RFC1700]; however, a current list is maintained at
    http://www.iana.org.
    for example: TCP = 0x06, UDP = 0x11, etc.

Bivens Informational [Page 9] RFC 4678 SASPv1 September 2006

 o  Port: The port number used for communication to the member.
    *** A value of 0 can be given for the Protocol and Port to signify
    a system level member.  However, 0 shouldn't be perceived as a
    wildcard for either Port or Protocol fields (i.e., a
    deregistration request that includes a MemberData component with a
    0 for the port doesn't mean deregister all applications listening
    on any port of that IP and protocol).
 o  IP Address: The current format is described by the following 16
    bytes, where IPv4 addresses are represented as "IPv4-compatible
    IPv6 addresses" [RFC4291].  In the following example, the x's and
    zeros represent 4-bit hex values.  The x's describe arbitrary hex
    values.
       IPv4 Address: 00 00 00 00 00 00 00 00 00 00 00 00 xx xx xx xx
       IPv6 Address: xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx
 o  Label length: The length, in bytes, of the label string to follow.
 o  Label: A UTF8 string that may be set while registering a member.
    This string is opaque to the GWM and is simply included with any
    correspondence containing the member data component.  Note that
    the size of this label is <= 255 bytes.  Because UTF8 character
    encodings may be up to 6 bytes, care must be exercised by the load
    balancer or member to make sure the UTF8 string it sends the GWM
    is in fact <= 255 bytes.

Bivens Informational [Page 10] RFC 4678 SASPv1 September 2006

5.2. Group Data Component

 The group data component simply describes a group with which to
 associate other singular components.
    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    Group Data Type (0x3011)   |       Size of this TLV        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | LB UID Length |                                               |
    +-+-+-+-+-+-+-+-+                                               +
    .                                                               .
    .                             LB UID                            .
    .                                                               .
    +                                               +-+-+-+-+-+-+-+-+
    |                                               |Group Name Len |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                          Group Name                           .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                               Figure 6
 o  LB UID Length: Length of the LB UID to follow (in bytes).
 o  LB UID: A UTF8 string used as a unique identifier and a context
    for the Group Name (e.g., a UTF8 representation of the MAC address
    of the load balancer or some type of Universally Unique Identifier
    (UUID)).  This string is used by the Group Workload Manager to
    associate application registration and deregistration, and to set
    state messages with the correct load balancer.  This unique
    identifier should not be any longer than 64 bytes.
 o  Group Name Len: Length of the Group Name field to follow (in
    bytes).
 o  Group Name: A UTF8 string the load balancer has chosen to tell the
    Group Workload Manager that members being registered with this
    Group Name are equivalent in function.  In Get Weight and
    DeRegistration messages, the Group Name may be omitted (Group Name
    Length = 0) to indicate all groups from the associated load
    balancer.

Bivens Informational [Page 11] RFC 4678 SASPv1 September 2006

5.3. Weight Entry Data Component

 The Weight Entry Component is used by the get and send weight
 messages to associate a weight with a particular member (or Member
 Data).  It also uses an opaque member state field and a general
 member flags field to denote extra information about a member
 (described below).  When the Weight Entry component is used, the
 Member Data TLV it refers to is listed first, immediately followed by
 the Weight Entry TLV.
    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Member Data Type (0x3010)   | Size of this Member Data TLV  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                      Member Data Fields                       .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Weight Entry Type (0x3012)  | Size of this Weight Entry TLV |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  State Field  |  Flags Field  |             Weight            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                               Figure 7
 o  State Field: This field is used by the member to communicate state
    information to the scheduler.  The information placed in this
    field is opaque to the GWM and will simply be forwarded to the
    scheduler with the member weights.  There are no defined values
    for this field.
 o  Flags Field: This field has several flag values that describe
    several attributes of the member.
    A.  Contact Success Flag (set by the GWM): describes whether the
        member is currently running.  If the contact success flag is
        off, this member should be avoided by the load balancer.
        +  xxxx xxx1 The GWM has located this running system or
           application.
        +  xxxx xxx0 The GWM has not located this running system or
           application.
    B.  Quiesce Flag (set by the load balancer or Member): used when
        an administrator would like to temporarily remove a member
        from the weight calculation, but not deregister it from the

Bivens Informational [Page 12] RFC 4678 SASPv1 September 2006

        group.  When quiesced, the member will still show up in the
        weights, but the quiesce flag will be set, and its weight will
        be zero.  When the administrator returns this member to
        active, the quiesce flag will be 0, and a weight will be
        provided.  If the quiesce flag is on, this member should be
        avoided by the load balancer.
        +  xxxx xx1x The member is quiesced.
        +  xxxx xx0x The member is active (not quiesced).
    C.  Registration Flag (set by the GWM): stores how the member was
        registered.
        +  xxxx x1xx This member has been registered by the load
           balancer/scheduler.
        +  xxxx x0xx This member has registered itself.
    D.  Confident Flag (set by the GWM): describes whether the GWM has
        knowledge of this member's state.  If this flag is off for
        only some of the members in the group while the remaining
        members have valid weights, the load balancer should avoid
        sending work to those members with the confident flag off.  If
        the confident flag is off for all valid group members, the
        load balancer should disregard any recommendation from the GWM
        until the confident flag comes back on for at least one
        member.  In this case where all confident flags are off, the
        load balancer should determine the correct distribution of
        work by other means (perhaps a different advisor, previously
        configured static weights, etc.).
        The goal of the confident flag is to convey to the load
        balancer that it should look to other methods of distribution
        recommendations if the GWM cannot give recommendations for any
        of the valid group members.  If some members of the group have
        the confident flag on but the contact flag off or the quiesced
        flag on (meaning these members should always be avoided) while
        the remaining members of the group have their confident flag
        off, the load balancer should determine the appropriate
        distribution of work for those members with the confident flag
        off by other means.
        +  xxxx 1xxx GWM has determined it has knowledge of the state
           of this member.
        +  xxxx 0xxx GWM has no knowledge of the state of this member.

Bivens Informational [Page 13] RFC 4678 SASPv1 September 2006

    E.  Leftmost four bits are reserved (0000 xxxx - 1111 xxxx).
 o  Weight: This field represents the GWM's recommendation for the
    relative amount of work that should be sent to this member.  This
    is a 16-bit field with a possible range of 0 to 65536.  Load
    balancers should be prepared to receive a wide range of weight
    values.  Load balancers with limited maximum weight values may
    restrict the granularity of management by the GWM and in turn
    cause less than optimal performance.  Many existing
    implementations have supported a minimum raw weight range from 0
    to 100.

5.4. Member State Instance Component

 The Member State Instance Component is used by the set member state
 message to indicate the sender's perceived state of the member
 mentioned.  This component is used to set values that will ultimately
 end up in the WeightEntry component.  When the Member State Instance
 component is used, the Member Data TLV it refers to is listed first,
 immediately followed by the Member State Instance TLV.
    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Member Data Type (0x3010)   | Size of this Member Data TLV  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                      Member Data Fields                       .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Member State Instance(0x3013) | Size of Member State Inst TLV |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  State Field  |  Flags Field  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                               Figure 8
 o  State Field: This field is used by the member to communicate state
    information to the load balancer or scheduler.  There are no
    defined values for this field.
 o  Flags Field: This field describes attributes of the member.
    Currently the only flag value defined is that of the quiesce flag.
    The quiesce flag is used when an administrator would like to
    temporarily remove a member from the weight calculation, but not
    deregister it from the group.  When quiesced, the member will
    still show up in the weights, but the quiesce flag will be set,

Bivens Informational [Page 14] RFC 4678 SASPv1 September 2006

    and its weight will be zero.  When the administrator returns this
    member to active, the quiesce flag will be 0, and a weight will be
    provided.
    A.  Quiesce Flag
        +  xxxx xxx1 The member or load balancer setting this state is
           quiescing this member.
        +  xxxx xxx0 The member or load balancer setting this state is
           placing the member in a non-quiesced state.
    B.  Leftmost seven bits are reserved (0000 000x - 1111 111x).

6. Group Protocol Components

 Group protocol components each contain a collection of related
 singular components.  In particular, they associate Member Data,
 Weight Entry, or Member State Instance components to a particular
 Group Data component.  In these cases, the particular "Group of x"
 component will be immediately followed by the Group Data component.
 The Group Data component will be immediately followed by any number
 of singular components the group contains.  In figures listed in this
 document, a component type with an asterisk denotes a component that
 is repeated a number of times.

6.1. Group of Member Data Component

 The "group of member data" component describes a particular group of
 members and is used in the registration message components.
    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Group of Member Data (0x4010) | Size of GroupOfMemberData TLV |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |        Member Count           |                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
    .                                                               .
    .                        Group Data TLV                         .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .               *Array of Member Data Components              .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                               Figure 9

Bivens Informational [Page 15] RFC 4678 SASPv1 September 2006

 o  Member Count: The number of Member Data Components immediately
    following the Group Data structure.
 o  Array of Member Data Components: There will be as many Member Data
    TLVs as Member Count has specified.  A load balancer/scheduler
    would use these components to pass information that would enable
    the Group Workload Manager to identify the members to associate
    with this Group Name.  The Member Data Component was described in
    Section 5.1.  In DeRegistration messages, the Member Count may be
    set to 0 to indicate all members of a particular group.

6.2. Group of Weight Data Component

 The "Group of Weight Data" Component is used by the get and send
 weight messages to create a list of Weight Entry Components for a
 particular group.
    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |Group Weight Entry Type(0x4011)| Size of GroupOfWeightEntry TLV|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |     Weight Entry Count        |                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
    .                                                               .
    .                        Group Data TLV                         .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .              *Array of Weight Entry Data Components           .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                               Figure 10
 o  Weight Entry Count: The number of Member Data / Weight Entry
    combinations to follow the Group Data TLV.
 o  Array of Weight Entry Data TLVs: There will be as many [Member
    Data / Weight Entry] TLVs as Weight Entry Count has specified.
    Each Weight Entry component is preceded by its corresponding
    Member Data component as explained in Section 5.3.  This Member
    Data / Weight Entry data combination will repeat to form as many
    Weight Entry items as the Weight Entry Count specifies.

Bivens Informational [Page 16] RFC 4678 SASPv1 September 2006

6.3. Group of Member State Data Components

 The "group of member state data" component describes a particular set
 of members and their corresponding state fields used in the Set
 Member State messages.
    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |Group Weight Entry Type(0x4011)| Size of GroupOfWeightEntry TLV|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Member State Instance Count  |                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
    .                                                               .
    .                        Group Data TLV                         .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .            *Array of Member State Data Components             .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                               Figure 11
 o  Member State Instance Count: The number of Member Data / Member
    State Instance combinations following the Group Data component.
 o  Array of Member State Data Components: Each Member State Instance
    component is immediately preceded by its corresponding Member Data
    component as explained in Section 5.4.  This Member Data / Member
    State Instance combination will repeat to form as many Member
    State items as the Member State Instance Count specifies.

7. Protocol Messages

 SASP messages are a collection of TLVs (Type, Length, and Value
 components).  The header has no information as to what type of
 message it is part of; the purpose-specific information is in the
 message component.  This format could facilitate placing more than
 one message component in a single message; however, this use of
 multiple message components is not supported in every GWM and could
 produce indeterminate behavior.  Similar to the other protocol
 components, when a message component needs to involve other
 components, the additional components immediately follow the message
 component.

Bivens Informational [Page 17] RFC 4678 SASPv1 September 2006

 All SASP requests sent to the GWM will be acknowledged with a reply.
 The reply contains information requested as well as a single-byte
 response code describing the success of the request.  SASP defines
 some general response codes in the range of 0x00 - 0x3F that may be
 used regardless of the response message type.  However, some request
 types may cause specific error conditions not covered by the general
 response codes.  The response code range of 0x40 - 0xFF is used for
 these message-specific response codes.  Any given SASP response will
 only contain one response code (depending on the error type).  This
 section explains the format and purpose of specific SASP messages.

7.1. Registration Request and Reply

 This exchange happens between the load balancer/scheduler and the
 Group Workload Manager as well as between the Group Workload Manager
 and the member to register the members in a group specified by Group
 Name.  Applications are identified with an IP address, Protocol, and
 Port.  Systems are identified only with an IP Address (Port = 0x0000
 and Protocol = 0x00).  All members in a group have equivalent
 functionality, so the Group Workload Manager can direct routers, load
 balancers, and schedulers to any member in the group.  Even though
 registrations can come from either the load balancer/scheduler or the
 actual member, member-initiated registrations will only be considered
 if the Trust flag is set while the state of the load
 balancer/scheduler is set.

7.1.1. Registration Request

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                      SASP Header TLV                          .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Registration Req. Type(0x1010)| Size of Registration Req. TLV |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Flag Field  |   Group of Member Data Count  |               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               +
    .                                                               .
    .           *Array of Group of Member Data Components           .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  • There will be as many Group of Member Data Components as "Group of

Member Data Count" has specified.

                               Figure 12

Bivens Informational [Page 18] RFC 4678 SASPv1 September 2006

 o  Flag Field
    A.  Load Balancer Flag
        +  xxxx xxx1 The entity sending this message is the load
           balancer.
        +  xxxx xxx0 The entity sending this message is an
           Application.
    B.  Leftmost seven bits are reserved (0000 000x - 1111 111x).
 o  Group of Member Data Count: The number of "Group of Member Data"
    components immediately following the Registration Request
    component.
 o  Array of Group of Member Data Components: Each "Group of Member
    Data" component is immediately followed by Group Data Components
    and its Member Data components (as described in Section 6.1).  In
    the case where several of these "Group of Member Data" components
    may be present, the second "Group of Member Data" component only
    appears after all of the internal components that are referred to
    by the first "Group of Member Data" component are listed.  The
    format is the same for all subsequent "Group of Member Data"
    components in the message.

7.1.2. Registration Reply

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                      SASP Header TLV                          .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |Registration Reply Type(0x1015)| Size of Registration Reply TLV|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Return Code  |
    +-+-+-+-+-+-+-+-+
                               Figure 13
 o  General SASP return codes (0x00 - 0x3F)
  • 0x00 Successful
  • 0x10 Message not understood

Bivens Informational [Page 19] RFC 4678 SASPv1 September 2006

  • 0x11 GWM will not accept this message from the sender. Reasons

for this include the following:

       a. The message was not sent by a LB and trust flag is off
       b. LB attempted to address members of a different LB in the
          message
       c. Vendor specific criteria for this message type were not met.
 o  Message-Specific return codes (0x40 - 0xFF)
  • 0x40 Member already registered
  • 0x44 Duplicate Member in Request
  • 0x45 Invalid Group (determined by the GWM)
  • 0x50 Invalid Group Name Size (size == 0)
  • 0x51 Invalid LB UID Size (size == 0 or > max)
  • 0x61 Member is registering itself, but LB hasn't yet contacted

the GWM. This registration will not be processed.

  • *The Invalid Group error return code refers to the LB or member

attempting to form a group that the GWM considers invalid. For

 example, some GWM vendors may not support the registration of both
 System and Application members in the same group.  To determine what
 can cause a GWM to return this error code, the vendor's documentation
 must be consulted.

7.2. DeRegistration Request and Reply

 This exchange happens between the load balancer/scheduler and the
 Group Workload Manager as well as between the Group Workload Manager
 and the Member to deregister members from a group specified by Group
 Name with the Group Workload Manager.  Even though deregistrations
 can come from either the load balancer/scheduler or the actual
 member, member-initiated deregistrations will only be considered if
 the Trust flag is set with a Set LB State message.

Bivens Informational [Page 20] RFC 4678 SASPv1 September 2006

7.2.1. DeRegistration Request

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                      SASP Header TLV                          .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |DeRegistration Req.Type(0x1020)|Size of DeRegistration Req. TLV|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Flag Field  |     Reason    |   Group of Member Data Count  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .           *Array of Group of Member Data Components           .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  • There will be as many Group of Member Data Components as "Group of

Member Data Count" has specified.

                               Figure 14
 o  Flag Field
    A.  Load Balancer Flag
        +  xxxx xxx1 The entity sending this message is the load
           balancer.
        +  xxxx xxx0 The entity sending this message is an
           Application.
    B.  Leftmost seven bits are reserved (0000 000x - 1111 111x).
 o  Reason: Byte describing the reason for deregistering the group or
    instance.
    A.  SASP-defined Reason Codes (0x00-0x7F)
        +  0x00 No reason given.
        +  0x01 Learned and Purposeful, i.e., a human has deconfigured
           this member from the load balancer configuration.
        +  0x80-0xFF Open for vendor specific deregistration reason
           codes.

Bivens Informational [Page 21] RFC 4678 SASPv1 September 2006

 o  Group of Member Data Count: The number of "Group of Member Data"
    components immediately following the DeRegistration Request
    component.
 o  Array of Group of Member Data Components: Each "Group of Member
    Data" component is immediately followed by Group Data Components
    and its Member Data components (as described in Section 6.1).  In
    this case, where several of these "Group of Member Data"
    components may be present, the second "Group of Member Data"
    component only appears after all of the internal components that
    are referred to by the first "Group of Member Data" component are
    listed.  The format is the same for all subsequent "Group of
    Member Data" components in the message.
  • * If Member Count equals zero in the Group of Member Data component,

the Group Workload Manager will deregister the entire group.

  • * Recall that the Group Data Component contains both a Unique LB

Identifier field and a Group Name field. If the Group Data component

 has no Group Name (GroupData's Group Name Length==0), the Group
 Workload Manager will deregister all groups associated with this load
 balancer.

7.2.2. DeRegistration Reply

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                      SASP Header TLV                          .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   DeReg. Reply Type(0x1025)   |    Size of DeReg. Reply TLV   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Return Code  |
    +-+-+-+-+-+-+-+-+
                               Figure 15
 o  Return Code: A byte return code indicating the status of action
    taken.
    A.  General SASP return codes (0x00 - 0x3F)
        +  0x00 Successful
        +  0x10 Message not understood

Bivens Informational [Page 22] RFC 4678 SASPv1 September 2006

        +  0x11 GWM will not accept this message from the sender.
           Reasons for this include the following:
           a. The message was not sent by a LB and trust flag is off
           b. LB attempted to address members of a different LB in the
              message
           c. Vendor specific criteria for this message type were not
              met.
    B.  Message-Specific return codes (0x40 - 0xFF)
        +  0x41 Application or System not registered
        +  0x42 Unknown Group Name
        +  0x43 Unknown LB UID
        +  0x44 Duplicate Member in Request
        +  0x46 Duplicate Group in Request (for remove all
           members/groups requests)
        +  0x51 Invalid LB UID Size (size == 0 or > max)
        +  0x61 Member is deregistering itself, but LB hasn't yet
           contacted the GWM.  This deregistration will not be
           processed.

7.3. Get Weights Request and Reply

 This exchange happens between the load balancer/scheduler and the
 Group Workload Manager to get weights for the groups specified in the
 list of GroupData objects.  In the case of application load balancing
 (balancing workloads between applications with the same
 functionality), the load balancer would call the Group Workload
 Manager every Interval (parameter returned by the Group Workload
 Manager below) to get an array of weights and associated members
 (e.g., Application1 20, SecondCopyOfApplication 30,
 ThirdCopyOfApplication 5).  The load balancer then uses these weights
 to determine the fashion in which work will be sent to each of the
 members.  For example, in the case of weighted round robin, the load
 balancer/scheduler would then send a request to Application1, the
 next to SecondCopyOfApplication, and the next to
 ThirdCopyOfApplication.  After 15 requests, the load
 balancer/scheduler would only send work to Application1 and
 SecondCopyOfApplication.  After an additional 30 requests, the load
 balancer/scheduler would only send requests to
 SecondCopyofApplication.  After another 10 requests, the load
 balancer/scheduler product would start over using the weights of 20,

Bivens Informational [Page 23] RFC 4678 SASPv1 September 2006

 30, and 5 again; or if the Interval number of seconds have passed,
 the load balancer/scheduler would get a new set of weights.

7.3.1. Get Weights Request

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                      SASP Header TLV                          .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Get Weights Req. Type(0x1030) |  Size of Get Weights Req. TLV |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |        Group Data Count       |                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
    .                                                               .
    .                   *Array of Group Data Components             .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  • There will be as many Group Data Components as "Group Data Count"

has specified.

                               Figure 16
 o  Group Data Count: The number of "Group Data" components
    immediately following the Get Weights Request TLV.
 o  Array of Group Data Components: This array of Group Data
    Components lists the groups for which the load balancer wants to
    get weights.
  • * If there is no group name in the Group Data structure of the Get

Weights Request, the load balancer is requesting weights for all

 groups registered for the load balancer.

Bivens Informational [Page 24] RFC 4678 SASPv1 September 2006

7.3.2. Get Weights Reply

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                      SASP Header TLV                          .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Get Weights Reply Type(0x1035)| Size of Get Weights Reply TLV |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Return Code  |            Interval           | Group of Weight
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    Entry Data Count|                                               |
    +-+-+-+-+-+-+-+-+                                               +
    .                                                               .
    .             *Group of Weight Entry Data Components            .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  • There will be as many Group of Weight Entry Data Components as

"Group of Weight Entry Data Count" has specified.

                               Figure 17
 o  Return Code: A byte return code indicating the status of action
    taken.
    A.  General SASP return codes (0x00 - 0x3F)
        +  0x00 Successful
        +  0x10 Message not understood
        +  0x11 GWM will not accept this message from the sender.
           Reasons for this include the following:
           a. LB attempted to address members of a different LB in the
              message
           b. Vendor specific criteria for this message type were not
              met.
    B.  Message-Specific return codes (0x40 - 0xFF)
        +  0x42 Unknown Group Name
        +  0x43 Unknown LB UID
        +  0x46 Duplicate Group in Request

Bivens Informational [Page 25] RFC 4678 SASPv1 September 2006

        +  0x51 Invalid LB uid Size (size == 0 or > max)
 o  Interval: These two bytes indicate a recommended polling interval
    for the load balancer to use.  The Group Workload Manager is
    stating that any polling interval smaller than the suggested
    interval would probably retrieve values before they have had a
    chance to change.
 o  Group of Weight Entry Data Components: Each "Group of Weight Data"
    component is immediately followed by Group Data Components and its
    Weight Entry Data components (as described in Section 6.2).  In
    this case, where several "Group of Weight Data" components may be
    present, the second "Group of Weight Data" component only appears
    after all of the internal components that are referred to by the
    first "Group of Weight Data" component are listed.  The format is
    the same for all subsequent "Group of Weight Data" components in
    the message.

7.4. Send Weights

 This exchange happens between the Group Workload Manager and the load
 balancer/scheduler to send the new weights for the group specified in
 Group Name.  This message is unique in that it is the only message
 exchange initiated by the Group Workload Manager and the only message
 that has no reply.  In the case of application load balancing
 (balancing workloads between applications with the same
 functionality), the Group Workload Manager would message the load
 balancer at a possibly dynamic interval (chosen by the Group Workload
 Manager) to send an array of weights and associated members (e.g.,
 Application1 20, SecondCopyOfApplication 30, ThirdCopyOfApplication
 5).  The load balancer then uses these weights to determine the
 fashion in which work will be sent to each of the members.  For
 example, in the case of weighted round robin, the load
 balancer/scheduler would then send a request to Application1, the
 next to SecondCopyOfApplication, and the next to
 ThirdCopyOfApplication.  After 15 requests, the load
 balancer/scheduler would only send work to Application1 and
 SecondCopyOfApplication.  After another 30 requests, the load
 balancer/scheduler would only send requests to
 SecondCopyofApplication.  After an additional 10 requests, the load
 balancer/scheduler product would start over using the weights of 20,
 30, and 5 again, if it has not yet received a new set of weights.
 The Group Workload Manager only sends this message if the Push flag
 has been enabled using a Set Load Balancer State message.

Bivens Informational [Page 26] RFC 4678 SASPv1 September 2006

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                      SASP Header TLV                          .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    Send Weights Type(0x1040)  |    Size of Send Weights TLV   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Group of Weight Data Count   |                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
    .                                                               .
    .             *Group of Weight Entry Data Components            .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  • There will be as many Group of Weight Entry Data Components as

"Group of Weight Data Count" has specified.

                               Figure 18
 o  Group of Weight Entry Data Components: Each "Group of Weight Data"
    component is immediately followed by Group Data Components and its
    Weight Entry Data components (as described in Section 6.2).  In
    this case, where several "Group of Weight Data" components may be
    present, the second "Group of Weight Data" component only appears
    after all of the internal components that are referred to by the
    first "Group of Weight Data" component are listed.  The format is
    the same for all subsequent "Group of Weight Data" components in
    the message.

7.5. Set Member State Request and Reply

 This is a special exchange that can take place between the load
 balancer and the Group Workload Manager or between the Member and the
 Group Workload Manager to pass information about the state of the
 member including placing the member in quiesced or non-quiesced
 states.  In particular, the load balancer/scheduler can use this
 message to quiesce a set of members.  Members can also use this
 message to quiesce themselves as well as to pass certain state
 information to the load balancer/scheduler that is opaque to the
 Group Workload Manager.  This opaque state information is passed to
 the load balancer/scheduler with the weights during get and send
 weight messages.

Bivens Informational [Page 27] RFC 4678 SASPv1 September 2006

7.5.1. Set Member State Request

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                      SASP Header TLV                          .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |SetMemberState Req.Type(0x1060)|Size of SetMemberState Req. TLV|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Flag Field  | Group of MemberStateData Count|               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               +
    .                                                               .
    .        *Array of Group of Member State Data Components        .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  • There will be as many Group of Member State Data Components as

"Group of Member State Data Count" has specified.

                               Figure 19
 o  Flag Field
    A.  Load Balancer Flag
        +  xxxx xxx1 The entity sending this message is the load
           balancer.
        +  xxxx xxx0 The entity sending this message is an
           Application.
    B.  Leftmost seven bits are reserved (0000 000x - 1111 111x).
 o  Group of Member State Data Count: The number of "Group of Member
    State Data" components immediately following the Set Member State
    Request TLV.
 o  Array of Group of Member Data Components: Each "Group of Member
    State Data" component is immediately followed by Group Data
    Components and its Member State Instance components (as described
    in Section 6.3).  In the case where several "Group of Member State
    Data" components may be present, the second "Group of Member State
    Data" component only appears after all of the internal components
    that are referred to by the first "Group of Member State Data"
    component are listed.  The format is the same for all subsequent
    "Group of Member State Data" components in the message.

Bivens Informational [Page 28] RFC 4678 SASPv1 September 2006

7.5.2. Set Member State Reply

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                      SASP Header TLV                          .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Set Member State Reply(0x1025)|Size of SetMemberStateReply TLV|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Return Code  |
    +-+-+-+-+-+-+-+-+
                               Figure 20
 o  Return Code: A byte return code indicating the status of action
    taken.
    A.  General SASP return codes (0x00 - 0x3F)
        +  0x00 Successful
        +  0x10 Message not understood
        +  0x11 GWM will not accept this message from the sender.
           Reasons for this include the following:
           a. The message was not sent by a LB and trust flag is off
           b. LB attempted to address members of a different LB in the
              message
           c. Vendor specific criteria for this message type were not
              met.
    B.  Message-Specific return codes (0x40 - 0xFF)
        +  0x41 Application or System not registered
        +  0x42 Unknown Group Name
        +  0x43 Unknown LB UID
        +  0x44 Duplicate Member in Request
        +  0x46 Duplicate Group in Request
        +  0x50 Invalid Group Name Size (size == 0)
        +  0x51 Invalid LB UID Size (size == 0 or > than max)

Bivens Informational [Page 29] RFC 4678 SASPv1 September 2006

        +  0x61 Member is setting state for itself, but LB hasn't yet
           contacted the GWM.  This request will not be processed.

7.6. Set Load Balancer State Request and Reply

 This is an exchange that can take place between the load balancer and
 the Group Workload Manager to pass information about the state (and
 partial configuration) of the load balancer.

7.6.1. Set LB State Request

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                      SASP Header TLV                          .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |Set LB State Req. Type (0x1050)| Size of Set LB State Req. TLV |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | LB UID Length |                                               |
    +-+-+-+-+-+-+-+-+                                               +
    .                                                               .
    .                             LB UID                            .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    LB Health  |    LB Flags   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                               Figure 21
 o  LB UID Length: one-byte length field describing the size of the
    following LB UID.
 o  LB UID: This should be the same unique identifier given when
    registering group members for this particular load balancer.
 o  LB Health: This field gives the load balancer a chance to pass in
    a metric describing its own health or state.
       0x00 - 0x7F Least Healthy - Most Healthy
       0x80 - 0xFF Reserved
 o  LB Flags:
    A.  Push Flag

Bivens Informational [Page 30] RFC 4678 SASPv1 September 2006

        +  xxxx xxx1 The load balancer should receive weights through
           the Send Weights message (GWM pushes weights to load
           balancer).  Even if this flag is set, the GWM must still
           respond accordingly to any Get Weights messages from the
           load balancer.
        +  xxxx xxx0 The load balancer will send a Get Weights message
           to get the new weights.  This is the default behavior.
           (load balancer pulls weights from GWM).
    B.  Trust Flag
        +  xxxx xx1x Trust any member-initiated registration,
           deregistration, or set state message.  Immediately reflect
           the registration, deregistration, or new state in the
           weights sent.
        +  xxxx xx0x Do not trust any member-initiated registration,
           deregistration, or set state message.  Registration,
           Deregistration, and State Setting of members can only occur
           from the load balancer.  Discard any member-initiated
           registration, deregistration, or set state message.  This
           is the default behavior.
    C.  No Change / No Send Flag
        +  xxxx x1xx The GWM must not include members whose weights
           and state (i.e., contact and quiesce flags) have not
           changed since they were last sent.
        +  xxxx x0xx The GWM must include the weights of all group
           members when sending the weights to this load balancer
           (including members whose weights and state have not
           changed).  This is the default behavior.
    D.  Leftmost five bits are reserved (0000 0xxx - 1111 1xxx).

Bivens Informational [Page 31] RFC 4678 SASPv1 September 2006

7.6.2. Set LB State Reply

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                      SASP Header TLV                          .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Set LB State Reply (0x1025) | Size of Set LB State Reply TLV|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Return Code  |
    +-+-+-+-+-+-+-+-+
                               Figure 22
 o  Return Code: A byte return code indicating the status of action
    taken.
    A.  General SASP return codes (0x00 - 0x3F)
        +  0x00 Successful
        +  0x10 Message not understood
        +  0x11 GWM will not accept this message from the sender.
           Reasons for this include the following:
           a. LB attempted to address the state of a different LB
           b. Vendor specific criteria for this message type were not
              met.
    B.  Message-Specific return codes (0x40 - 0xFF)
        +  0x51 Invalid LB UID Size (size == 0 or > max)

8. Example of SASP Message Encoding

 This section provides an example of the actual SASP message encoding.
 For this example, we will look at a sample GetWeights Reply in which
 two webservers are registered to a serverfarm called FARM1.  The IP
 addresses of the two webservers are 10.10.10.1 and 10.10.10.2.
 Currently the GWM has a weight of 40 for 10.10.10.1 and 20 for
 10.10.10.2.  The load balancer has a unique Identifier of "LB1" and
 the message example was sent by the GWM in response to a request
 (MessageID: 0x32000000) for FARM1's weights.

Bivens Informational [Page 32] RFC 4678 SASPv1 September 2006

 The TLVs necessary for this message are shown in the following list.
 1.  SASP Header TLV
  1. ———————————–

| | Field | Size | Value |

 |-----------|---------|------------|
 |T| Type    | 2 bytes | 0x2010     |
 |-----------|---------|------------|
 |L| Length  | 2 bytes | 0x000D     |
 |-----------|---------|------------|
 | | Version | 1 byte  | 0x01       |
 | |---------|---------|------------|
 |V| Mesg Len| 4 bytes | 0x0000 006A|
 | |---------|---------|------------|
 | | Mesg ID | 4 bytes | 0x3200 0000|
 ------------------------------------
                                 Figure 23
 2.  Get Weights Reply TLV
  1. ———————————–

| | Field | Size | Value |

 |-----------|---------|------------|
 |T| Type    | 2 bytes | 0x1035     |
 |-----------|---------|------------|
 |L| Length  | 2 bytes | 0x0009     |
 |-----------|---------|------------|
 | | RetCode | 1 byte  | 0x00       |
 | |---------|---------|------------|
 |V| Interval| 2 bytes | 0x0040     |
 | |---------|---------|------------|
 | |GWD Count| 2 bytes | 0x0001     |
 ------------------------------------
 *GWD Count = Group of Weight Data Count
                                 Figure 24

Bivens Informational [Page 33] RFC 4678 SASPv1 September 2006

 3.  Group of Weight Data TLV
  1. ———————————–

| | Field | Size | Value |

 |-----------|---------|------------|
 |T| Type    | 2 bytes | 0x4011     |
 |-----------|---------|------------|
 |L| Length  | 2 bytes | 0x0006     |
 |-----------|---------|------------|
 |V| WE Count| 2 bytes | 0x0002     |
 ------------------------------------
 *WE Count = Weight Entry Count
                                 Figure 25
 4.  Group Data TLV
  1. ———————————–

| | Field | Size | Value |

 |-----------|---------|------------|
 |T| Type    | 2 bytes | 0x3011     |
 |-----------|---------|------------|
 |L| Length  | 2 bytes | 0x000E     |
 |-----------|---------|------------|
 | |LBUID len| 1 byte  | 0x03       |
 | |---------|---------|------------|
 | |  LBUID  | 3 bytes | "LB1" or   |
 | |         |         | 0x4C 42 31 |
 |V|---------|---------|------------|
 | |GroupName| 1 byte  | 0x05       |
 | | Length  |         |            |
 | |---------|---------|------------|
 | |  Group  |         | "FARM1" or |
 | |  Name   | 5 bytes | 0x46 41 52 |
 | |         |         |   4D 31    |
 ------------------------------------
                                 Figure 26

Bivens Informational [Page 34] RFC 4678 SASPv1 September 2006

 5.  Member Data TLV
  1. ———————————–

| | Field | Size | Value |

 |-----------|---------|------------|
 |T| Type    | 2 bytes | 0x3010     |
 |-----------|---------|------------|
 |L| Length  | 2 bytes | 0x0018     |
 |-----------|---------|------------|
 | | Protocol| 1 byte  | 0x06       |
 | |---------|---------|------------|
 | |  Port   | 2 bytes | 0x0050     |
 | |---------|---------|------------|
 |V|   IP    |16 bytes | 0x0000 0000|
 | | Address |         |   0000 0000|
 | |         |         |   0000 0000|
 | |         |         |   0A0A 0A01|
 | |---------|---------|------------|
 | |Label Len| 1 byte  | 0x00       |
 | |---------|---------|------------|
 | |  Label  | 0 bytes |            |
 ------------------------------------
                                 Figure 27
 6.  Weight Entry Data TLV
  1. ———————————–

| | Field | Size | Value |

 |-----------|---------|------------|
 |T| Type    | 2 bytes | 0x3012     |
 |-----------|---------|------------|
 |L| Length  | 2 bytes | 0x0008     |
 |-----------|---------|------------|
 | | State   | 1 byte  | 0x00       |
 | |---------|---------|------------|
 |V| Flags   | 1 byte  | 0x0D       |
 | |---------|---------|------------|
 | | Weight  | 2 bytes | 0x0028     |
 ------------------------------------
                                 Figure 28

Bivens Informational [Page 35] RFC 4678 SASPv1 September 2006

 7.  Member Data TLV
  1. ———————————–

| | Field | Size | Value |

 |-----------|---------|------------|
 |T| Type    | 2 bytes | 0x3010     |
 |-----------|---------|------------|
 |L| Length  | 2 bytes | 0x0018     |
 |-----------|---------|------------|
 | | Protocol| 1 byte  | 0x06       |
 | |---------|---------|------------|
 | |  Port   | 2 bytes | 0x0050     |
 | |---------|---------|------------|
 |V|   IP    |16 bytes | 0x0000 0000|
 | | Address |         |   0000 0000|
 | |         |         |   0000 0000|
 | |         |         |   0A0A 0A02|
 | |---------|---------|------------|
 | |Label Len| 1 byte  | 0x00       |
 | |---------|---------|------------|
 | |  Label  | 0 bytes |            |
 ------------------------------------
                                 Figure 29
 8.  Weight Entry Data TLV
  1. ———————————–

| | Field | Size | Value |

 |-----------|---------|------------|
 |T| Type    | 2 bytes | 0x3012     |
 |-----------|---------|------------|
 |L| Length  | 2 bytes | 0x0008     |
 |-----------|---------|------------|
 | | State   | 1 byte  | 0x00       |
 | |---------|---------|------------|
 |V| Flags   | 1 byte  | 0x0D       |
 | |---------|---------|------------|
 | | Weight  | 2 bytes | 0x0014     |
 ------------------------------------
                                 Figure 30
 A hex stream representing this same message is below:
    20 10 00 0D 01 00 00 00 6A 32 00 00 00 10 35 00 09 00 00 40
    00 01 40 11 00 06 00 02 30 11 00 0E 03 4C 42 31 05 46 41 52

Bivens Informational [Page 36] RFC 4678 SASPv1 September 2006

    4D 31 30 10 00 18 06 00 50 00 00 00 00 00 00 00 00 00 00 00
    00 0A 0A 0A 01 00 30 12 00 08 00 0D 00 28 30 10 00 18 06 00
    50 00 00 00 00 00 00 00 00 00 00 00 00 0A 0A 0A 02 00 30 12
    00 08 00 0D 00 14
 (106 bytes)

9. Protocol Flow

 This section describes the expected general flow of the SASP
 messages.

9.1. Normal Protocol Flow

 SASP first starts with a connection from an LB to the GWM.  This is
 expected to be a long-running connection and will be used for many
 messages.  After establishing the connection, the LB either registers
 a group of members or sets a Trust flag to allow the members to
 register themselves.  The Trust flag is set using a Set LB State
 Request (both message flows are shown below).
 Registration from load balancer
  1. ———– Registration Request ——————

| |———————–>| |

 |   Load   |                        | Group Workload |
 | Balancer |  Registration Reply    |     Manager    |
 |          |<-----------------------|                |
 ------------                        ------------------
 Set LB State from load balancer
  1. ———– Set LB State Request ——————

| |———————–>| |

 |   Load   |                        | Group Workload |
 | Balancer |  Set LB State Reply    |     Manager    |
 |          |<-----------------------|                |
 ------------                        ------------------
                               Figure 31

Bivens Informational [Page 37] RFC 4678 SASPv1 September 2006

 The connection can start with other requests, but any other request
 would likely result in an error (unless this connection is a
 reconnection that has happened a short period of time after the
 original connection).  For example, if the load balancer issues a
 deregistration request as its first message, it will receive an error
 because it has not registered any groups.
 The load balancer always drops all state information after a loss of
 connection and can recover it using a GetWeights message.  The
 establishment of a new connection causes the GWM to assume that the
 old one is broken.  In this case, the GWM will keep all state for the
 load balancer for a limited time after a detected break.  After the
 limited time has expired, all state for the broken connection will be
 discarded by the GWM.
 Registration of group members may be done at any time.  A load
 balancer can register anywhere from one group with one member to many
 groups of many members.  The member may also register itself if the
 Trust flag has been set and it knows the appropriate load balancer
 information.  Registrations will add to groups that already exist,
 but return errors if any of the registered members already exist.
 In the case of system load balancing, the representation of a member
 is only the member's IP address with a 0 used as the value for the
 port and protocol.  In the case of application load balancing, the
 representation of a member is the member's IP address and the
 Application's port and protocol.
 Deregistration of group members may be done at any time.  A load
 balancer can deregister anywhere from one group with one member to
 many groups of many members.  The LB may also deregister entire
 groups or deregister all of its groups at once.  The member may also
 deregister itself if the Trust flag has been set and it knows the
 appropriate load balancer information.
 Once members are registered, the GWM will start the monitoring and
 weight computation processes to determine weights to be sent back to
 the load balancer.  At any time the load balancer may issue a
 GetWeights message and ask for the weights for members in a
 particular group.  The LB may also set a flag telling the GWM to send
 the weights without waiting for the GetWeights message.  If this flag
 is set, the GWM will send the weights at an interval it feels is
 appropriate (the interval could change depending on the algorithm
 used and variance of the weights generated).
 At any time the LB or a particular member may quiesce the member
 through the use of a SetMemberState message.  In this case, the
 member's weight will always be zero, and the quiesce flag will be

Bivens Informational [Page 38] RFC 4678 SASPv1 September 2006

 turned on when sending its weight.  Members may also use this message
 to send an opaque state value that will also be presented when
 sending weights.
 At any time, the load balancer may choose to send the GWM a
 SetLBState request to configure its interaction.  The message allows
 the load balancer to set the Push, Trust, and NoChange_NoSend flags.
 It also allows the load balancer to pass a health value to the GWM to
 be displayed.

9.2. Behavior in Error Cases

 While behaviors in many error conditions will be product specific,
 the following error cases should have the following expected
 behavior.
 Case:  The protocol is violated in an unrecoverable manner by either
    end of the connection.
 Behavior:  Either end of the connection may choose to disconnect to
    avoid future message synchronization problems.  The state kept
    when disconnected is vendor specific.
 Case:  LB or application attempts to connect to the GWM before the
    GWM is fully up and running.
 Behavior:  The LB or application should wait at least 20 seconds to
    retry the connection.
 Case:  Members attempt to register or deregister themselves before
    the LB develops the connection with the GWM.
 Behavior:  In this case, the members would receive a reply with an
    error code signifying that there is no LB registered with that LB
    UID.
 Case:  Member registers or deregisters for an LB who has not set the
    Trust flag.
 Behavior:  GWM will send Member a reply containing an error code.

Bivens Informational [Page 39] RFC 4678 SASPv1 September 2006

 Case:  LB asks for weights for a group that doesn't exist.
 Behavior:  GWM will send LB a reply containing an error code.
 Case:  LB or Member attempts to register a member that is already
    registered in that group.
 Behavior:  GWM will send sender a reply containing an error code.
 Case:  LB or Member attempts to deregister a member or group that
    doesn't exist.
 Behavior:  GWM will send sender a reply containing an error code.
 Case:  LB or Member tries to set state for a non-registered server.
 Behavior:  GWM will send sender a reply containing an error code.
 Case:  LB tries to Get Weights for an unregistered group.
 Behavior:  GWM will send LB a reply containing an error code.

Bivens Informational [Page 40] RFC 4678 SASPv1 September 2006

9.3. Example Flow 1: Load Balancer Registration, Getting Weights, and

    Application-Side Quiescing
    Load                 Group Workload
  Balancer                   Manager
     |                         |
     | 1) Registration Request |
     |------------------------>|
     |<------------------------|
     |    Registration Reply   |
     |                         |
     | 2) Set LB State Request |
     |------------------------>|
     |<------------------------|
     |    Set LB State Reply   |
     |                         |
     | 3) Get Weights Request  |
     |------------------------>|
     |<------------------------|
     |    Get Weights Reply    |
     |                         | 4) Set Member State Req. --------
     |                         |<-------------------------|Member|
     |                         |------------------------->|  A   |
     |                         |  Set Member State Reply  --------
     |                         |
     |                         | 5) Set Member State Req. --------
     |                         |<-------------------------|Member|
     |                         |------------------------->|  C   |
     |                         |  Set Member State Reply  --------
     |                         |
     | 6) Get Weights Request  |
     |------------------------>|
     |<------------------------|
     |    Get Weights Reply    |
     |                         |
     |                         | 7) Set Member State Req. --------
     |                         |<-------------------------|Member|
     |                         |------------------------->|  C   |
     |                         |  Set Member State Reply  --------
     |                         |
     | 8) Get Weights Request  |
     |------------------------>|
     |<------------------------|
     |    Get Weights Reply    |
     |                         |
                               Figure 32

Bivens Informational [Page 41] RFC 4678 SASPv1 September 2006

 1.  The LB registers Members A, B, and C in a group named GRP1.  The
     GWM replies with no error.
 2.  The LB turns its trust flag on by issuing a Set LB State message:
        LB Health: 0x00 Flags: 0000 0010
 3.  The LB sends a Get Weights message for GRP1 and gets the reply:
        Members      Opaque State     Flags          Weight
        --------     ------------     ---------      ------
        Member A     0x00             0000 1101      20
        Member B     0x00             0000 1101      40
        Member C     0x00             0000 1101       5
 4.  Member A sends a Set Member State message with flags:
        Members       Opaque State     Flags
        --------      ------------     ---------
        Member A      0x32             0000 0000
 5.  Member C sends a Set Member State message to quiesce itself with
     the following flags:
        Members       Opaque State     Flags
        --------      ------------     ---------
        Member C      0x0A             0000 0001
 6.  The LB sends the Get Weights message for GRP1 and receives the
     following:
        Members       Opaque State     Flags          Weight
        --------      ------------     ---------      ------
        Member A      0x32             0000 1101      20
        Member B      0x00             0000 1101      40
        Member C      0x0A             0000 1111       5
 7.  Member C sends a Set Member State message to resume (un-quiesce
     itself) with the following flags:
        Members       Opaque State     Flags
        --------      ------------     ---------
        Member C      0x0A             0000 0000

Bivens Informational [Page 42] RFC 4678 SASPv1 September 2006

 8.  The LB sends a Get Weights message for GRP1 and gets the reply:
        Members       Opaque State     Flags          Weight
        --------      ------------     ---------      ------
        Member A      0x32             0000 1101      20
        Member B      0x00             0000 1101      40
        Member C      0x0A             0000 1101       5

9.4. Example Flow 2: Set Load Balancer State, Application

    Registration, and Load Balancer Group DeRegistration
    Load                 Group Workload
  Balancer                   Manager
     |                         |
     | 1) Set LB State Request |
     |------------------------>|
     |<------------------------|
     |    Set LB State Reply   |
     |                         |
     |                         | 2) Registration Request  --------
     |                         |<-------------------------|Member|
     |                         |------------------------->|  A   |
     |                         |    Registration Reply    --------
     |                         |
     |                         | 3) Registration Request  --------
     |                         |<-------------------------|Member|
     |                         |------------------------->|  B   |
     |                         |    Registration Reply    --------
     |                         |
     | 4) Send Weights Mesg    |
     |<------------------------|
     |                         |
     |                         | 5) Registration Request  --------
     |                         |<-------------------------|Member|
     |                         |------------------------->|  C   |
     |                         |    Registration Reply    --------
     |                         |
     | 6) Send Weights Mesg    |
     |<------------------------|
     |                         |
     |7) Deregistration Request|
     |------------------------>|
     |<------------------------|
     |   Deregistration Reply  |
     |                         |
                               Figure 39

Bivens Informational [Page 43] RFC 4678 SASPv1 September 2006

 1.  The LB sets its state with the Set LB State message and the
     following parameters.
        Health: 0x7F Flags: 0000 0011
 2.  Member A registers itself for work in GRP1 using the Register
     message.
 3.  Member B registers itself for work in GRP1 using the Register
     message.
 4.  The GWM issues a Send Weights message to the LB.
        Members       Opaque State     Flags          Weight
        --------      ------------     ---------      ------
        Member A      0x00             0000 1001      20
        Member B      0x00             0000 1001      40
 5.  Member C registers itself for work in GRP1 using the Register
     message.
 6.  The GWM issues a Send Weights message to the LB.
        Members       Opaque State     Flags          Weight
        --------      ------------     ---------      ------
        Member A      0x00             0000 1001      20
        Member B      0x00             0000 1001      40
        Member C      0x00             0000 1001       5
 7.  LB deregisters GRP1 by using the DeRegister message with the
     Member Data Count = 0

9.5. Avoiding Single Points of Failure

 o  To avoid having a single point of failure at the load balancer, an
    administrator may choose to have multiple load balancers in his or
    her environment.  SASP provides for the GWM to keep track of
    multiple load balancers through the use of load balancer unique
    identifiers (LB UIDs).
 o  To avoid having a single point of failure at the GWM or enhance
    the load balancing strategy by utilizing the strengths of several
    different GWMs, an administrator may choose to have multiple GWMs
    in his or her environment.  In this case, the load balancer would

Bivens Informational [Page 44] RFC 4678 SASPv1 September 2006

    connect to multiple GWMs and register the same groups with
    corresponding members.  The load balancer may choose to coordinate
    the recommendations of each GWM by any method it chooses (e.g.,
    statistical combination such as averaging).  The coordination of
    weights from multiple GWMs is product specific and not addressed
    in this protocol.

10. Security Considerations

 SASP is a binary stream expected to be transported over a TCP
 connection.  To secure this protocol, it is expected that
 implementers of the protocol use a secure mode of transport such as
 SSL/TLS.  Discussions around security concerns have been listed
 below:
 Security Issue:  In insecure environments, if the LB UID becomes
    known by another system, the other system could initiate a
    connection and send messages to the GWM causing the GWM to replace
    the previous (possibly valid) connection for the new (potentially
    bad) connection.
 Solution:  This may not be a concern if the load balancer and GWM are
    in protected parts of the network.  If the administrator is
    concerned about this vulnerability, she should use SSL or TLS to
    provide authentication for the connection.  When using SSL or TLS
    to secure the connection, the administrator SHOULD use both server
    and client authentication through client and server certificates.
    The GWM will trust any certificate that is signed by an authority
    it's been configured to trust.
 Security Issue:  In insecure environments, if the load balancer turns
    the Trust Flag on, any member or other system can send a
    Registration Message and be included in the serverfarm to receive
    work.  A person with bad intentions and the correct information
    could exploit this feature and register his own application to
    receive work.  His counterfeit application could capture valuable
    data from unsuspecting clients as their transactions are sent to
    his system.
 Solution:  This may not be a concern if the GWM and its members are
    in protected parts of the network.  If the administrator is
    concerned about this vulnerability, she should use SSL or TLS to
    provide authentication for the member connections.  When using SSL
    or TLS to authenticate the connection, the administrator would
    need to explicitly install valid certificates on each component

Bivens Informational [Page 45] RFC 4678 SASPv1 September 2006

    while at the same time establishing the trusted certificates of
    each component.  This would make certain that only those trusted
    components would be permitted to connect to the GWM.

11. Normative References

 [RFC1700]  Reynolds, J. and J. Postel, "Assigned Numbers", STD 2,
            RFC 1700, October 1994.
 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
            Architecture", RFC 4291, February 2006.

Bivens Informational [Page 46] RFC 4678 SASPv1 September 2006

Appendix A. Acknowledgements

 The author gratefully acknowledges contributions by Mark Albert,
 David McCowan, John Fenton, Derek Huckaby, Dyan Collins, and Stefano
 Testa.  Mark Albert, David McCowan, John Fenton, Derek Huckaby, Dyan
 Collins, and Stefano Testa were supported for this work by Cisco
 Systems Inc.
 The author would also like to thank John Arwe, Dave Bostjancic, Brian
 Carpenter, Donna Dillenberger, Gus Kassimis, and Thomas Narten for
 their efforts in the creation and refining of this work.

Author's Address

 Alan Bivens
 IBM T.J. Watson Research Center
 19 Skyline Drive
 Hawthorne, NY  10532
 US
 EMail: jbivens@us.ibm.com

Bivens Informational [Page 47] RFC 4678 SASPv1 September 2006

Full Copyright Statement

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 This document is subject to the rights, licenses and restrictions
 contained in BCP 78 and at www.rfc-editor.org/copyright.html, and
 except as set forth therein, the authors retain all their rights.
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Bivens Informational [Page 48]

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