rfc1953.txt

<VC++网络游戏建摸与实现>源代码

Network Working Group                                 P. Newman, Ipsilon
Request for Comments: 1953                         W. L. Edwards, Sprint
Category: Informational                               R. Hinden, Ipsilon
                                                     E. Hoffman, Ipsilon
                                                  F. Ching Liaw, Ipsilon
                                                        T. Lyon, Ipsilon
                                                    G. Minshall, Ipsilon
                                                                May 1996


        Ipsilon Flow Management Protocol Specification for IPv4
                              Version 1.0

Status of this Memo

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

IESG Note:

   This memo documents a private protocol for IPv4-based flows.  This
   protocol is NOT the product of an IETF working group nor is it a
   standards track document.  It has not necessarily benefited from the
   widespread and in depth community review that standards track
   documents receive.

Abstract

   The Ipsilon Flow Management Protocol (IFMP), is a protocol for
   allowing a node to instruct an adjacent node to attach a layer 2
   label to a specified IP flow.  The label allows more efficient access
   to cached routing information for that flow.  The label can also
   enable a node to switch further packets belonging to the specified
   flow at layer 2 rather than forwarding them at layer 3.

Table of Contents

   1. Introduction....................................................2
   2. Flow Types......................................................2
   3. IFMP Adjacency Protocol.........................................4
       3.1  Packet Format.............................................4
       3.2  Procedure.................................................7
   4. IFMP Redirection Protocol......................................10
       4.1  Redirect Message.........................................12
       4.2  Reclaim Message..........................................13
       4.3  Reclaim Ack Message......................................15
       4.4  Label Range Message......................................16



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       4.5  Error Message............................................17
   References........................................................19
   Security Considerations...........................................19
   Authors' Addresses................................................19

1. Introduction

   The Ipsilon Flow Management Protocol (IFMP), is a protocol for
   instructing an adjacent node to attach a layer 2 label to a specified
   IP flow. The label allows more efficient access to cached routing
   information for that flow and it allows the flow to be switched
   rather than routed in certain cases.

   If a network node's upstream and downstream links both redirect a
   flow at the node, then the node can switch the flow at the data link
   layer rather than forwarding it at the network layer.  The label
   space is managed at the downstream end of each link and redirection
   messages are sent upstream to associate a particular flow with a
   given label.  Each direction of transmission on a link is treated
   separately.

   If the flow is not refreshed by the time the lifetime field in the
   redirect message expires, then the association between the flow and
   the label is discarded.  A flow is refreshed by sending a redirect
   message, identical to the original, before the lifetime expires.

   Several flow types may be specified.  Each flow type specifies the
   set of fields from the packet header that are used to identify a
   flow.  There must be an ordering amongst the different flow types
   such that a most specific match operation may be performed.

   A particular flow is specified by a flow identifier.  The flow
   identifier for that flow gives the contents of the set of fields from
   the packet header as defined for the flow type to which it belongs.

   This document specifies the IFMP protocol for IPv4 on a point-to-
   point link.  The definition of labels, and the encapsulation of
   flows, are specified in a separate document for each specific data
   link technology.  The specification for ATM data links is given in
   [ENCAP].

2. Flow Types

   A flow is a sequence of packets that are sent from a particular
   source to a particular (unicast or multicast) destination and that
   are related in terms of their routing and any logical handling policy
   they may require.




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   A flow is identified by its flow identifier.

   Several different flow types can be defined.  The particular set of
   fields from the packet header used to identify a flow constitutes the
   flow type.  The values of these fields, for a particular flow,
   constitutes the flow identifier for that flow.  The values of these
   fields must be invariant in all packets belonging to the same flow at
   any point in the network.

   Flow types are sub- or super-sets of each other such that there is a
   clear hierarchy of flow types.  This permits a most specific match
   operation to be performed.  (If additional flow types are defined in
   the future that are not fully ordered then the required behavior will
   be defined.) Each flow type also specifies an encapsulation that is
   to be used after a flow of this type is redirected.  The
   encapsulations for each flow type are specified in a separate
   document for each specific data link technology.  The encapsulations
   for flows over ATM data links are given in [ENCAP].

   Three flow types are defined in this version of the protocol:

   Flow Type 0

      Flow Type 0 is used to change the encapsulation of IPv4 packets
      from the default encapsulation.

      For Flow Type 0: Flow Type = 0 and Flow ID Length = 0.

      The Flow Identifier for Flow Type 0 is null (zero length).

   Flow Type 1

      Flow Type 1 is designed for protocols such as UDP and TCP in which
      the first four octets after the IPv4 header specify a Source Port
      number and a Destination Port number.

      For Flow Type 1, Flow Type = 1 and Flow ID Length = 4 (32 bit
      words).

      The format of the Flow Identifier for Flow Type 1 is:











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       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |Version|  IHL  |Type of Service| Time to Live  |   Protocol    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Source Address                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Destination Address                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          Source Port          |       Destination Port        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Flow Type 2

      For Flow Type 2, Flow Type = 2 and Flow ID Length = 3 (32 bit
      words).

      The format of the Flow Identifier for Flow Type 2 is:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |Version|  IHL  |   Reserved    | Time to Live  |   Reserved    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Source Address                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Destination Address                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      The Reserved fields are unused and should be set to zero by the
      sender and ignored by the receiver.

3. IFMP Adjacency Protocol

   The IFMP Adjacency Protocol allows a host or router to discover the
   identity of a peer at the other end of a link.  It is also used to
   synchronize state across the link, to detect when the peer at the
   other end of the link changes, and to exchange a list of IP addresses
   assigned to the link.

3.1 Packet Format

   All IFMP messages belonging to the Adjacency Protocol must be
   encapsulated within an IPv4 packet and must be sent to the IP limited
   broadcast address (255.255.255.255).  The Protocol field in the IP
   header must contain the value 101 (decimal) indicating that the IP
   packet contains an IFMP message.  The Time to Live (TTL) field in the
   IP header must be set to 1.



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   All IFMP messages belonging to the adjacency protocol have the
   following structure:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Version    |    Op Code    |           Checksum            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Sender Instance                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Peer Instance                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Peer Identity                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Peer Next Sequence Number                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Reserved              |    Reserved   | Max Ack Intvl |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                          Address List                         ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Version
             The IFMP protocol version number.  The current Version = 1.

   Op Code
             Specifies the function of the message.  Four Op Codes are
             defined for the IFMP Adjacency Protocol:

                SYN:    Op Code = 0
                SYNACK: Op Code = 1
                RSTACK: Op Code = 2
                ACK:    Op Code = 3

   Checksum
             The 16-bit one's complement of the one's complement sum of
             a pseudo header of information from the IP header and the
             IFMP message itself.  The pseudo header, conceptually
             prefixed to the IFMP message, contains the Source Address,
             the Destination Address, and the Protocol fields from the
             IPv4 header, and the total length of the IFMP message
             starting with the Version field (this is equivalent to the
             value of the Total Length field from the IPv4 header minus
             the length of the IPv4 header itself).






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   Sender Instance
             For the SYN, SYNACK, and ACK messages, is the sender's
             instance number for the link.  The receiver uses this to
             detect when the link comes back up after going down or when
             the identity of the peer at the other end of the link
             changes.  The instance number is a 32 bit number that is
             guaranteed to be unique within the recent past and to
             change when the link or node comes back up after going
             down.  It is used in a similar manner to the initial
             sequence number (ISN) in TCP [RFC 793].  Zero is not a
             valid instance number.  For the RSTACK message the Sender
             Instance field is set to the value of the Peer Instance
             field from the incoming message that caused an RSTACK
             message to be generated.

   Peer Instance
             For the SYN, SYNACK, and ACK messages, is what the sender
             believes is the peer's current instance number for the
             link.  If the sender of the message does not know the
             peer's current instance number for the link, the sender
             must set this field to zero.  For the RSTACK message the
             Peer Instance field is set to the value of the Sender
             Instance field from the incoming message that caused an
             RSTACK message to be generated.

   Peer Identity
             For the SYN, SYNACK, and ACK messages, is the IP address of
             the peer that the sender of the message believes is at the
             other end of the link.  The Peer Identity is taken from the
             Source IP Address of the IP header of a SYN or a SYNACK
             message.  If the sender of the message does not know the IP
             address of the peer at the other end of the link, the
             sender must set set this field to zero.  For the RSTACK
             message, the Peer Identity field is set to the value of the
             Source Address field from the IP header of the incoming
             message that caused an RSTACK message to be generated.

   Peer Next Sequence Number
             Gives the value of the peer's Sequence Number that the
             sender of the IFMP Adjacency Protocol message expects to
             arrive in the next IFMP Redirection Protocol message.  If a
             node is in the ESTAB state, and the value of the Peer Next
             Sequence Number in an incoming ACK message is greater than
             the value of the Sequence Number plus one, from the last
             IFMP Redirection Protocol message transmitted out of the
             port on which the incoming ACK message was received, the
             link should be reset.  The procedure to reset the link is
             defined in section 3.2.



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   Max Ack Intvl
             Maximum Acknowledgement Interval is the maximum amount of
             time the sender of the message will wait until transmitting
             an ACK message.

   Address List
             A list of one or more IP addresses that are assigned to the
             link by the sender of the message.  The list must have at
             least one entry that is identical to the Source Address in
             the IP header.  The contents of this list are not used by
             the IFMP protocol but can be made available to the routing
             protocol.

3.2 Procedure

   The IFMP Adjacency Protocol is described by the rules and state
   tables given in this section.

   The rules and state tables use the following operations:

    o The "Update Peer Verifier" operation is defined as storing the
      Sender Instance and the Source IP Address from a SYN or SYNACK
      message received from the peer on a particular port.

    o The procedure "Reset the link" is defined as:

          1. Generate a new instance number for the link
          2. Delete the peer verifier (set the stored values of Sender
             Instance and Source IP Address of the peer to zero)
          3. Set Sequence Number and Peer Next Sequence Number to zero
          4. Send a SYN message
          5. Enter the SYNSENT state