rfc1953.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

    o The state tables use the following Boolean terms and operators:

        A    The Sender Instance in the incoming message matches the
             value stored from a previous message by the "Update Peer
             Verifier" operation for the port on which the incoming
             message is received.

        B    The Sender Instance and the Source IP Address in the
             incoming message matches the value stored from a previous
             message by the "Update Peer Verifier" operation for the
             port on which the incoming message is received.







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RFC 1953                   IFMP Specification                   May 1996


        C    The Peer Instance and Peer Identity in the incoming message
             matches the value of the Sender Instance and the Source IP
             Address currently in use for all SYN, SYNACK, and ACK
             messages transmitted out of the port on which the incoming
             message was received.

        "&&" Represents the logical AND operation

        "||" Represents the logical OR operation

        "!" Represents the logical negation (NOT) operation.

    o A timer is required for the periodic generation of SYN, SYNACK,
      and ACK messages.  The period of the timer is unspecified but a
      value of one second is suggested.

      There are two independent events: the timer expires, and a packet
      arrives.  The processing rules for these events are:

         Timer Expires:   Reset Timer
                          If state = SYNSENT Send SYN
                          If state = SYNRCVD Send SYNACK
                          If state = ESTAB   Send ACK

         Packet Arrives:  If incoming message is an RSTACK
                             If A && C && !SYNSENT
                                Reset the link
                             Else Discard the message
                          Else the following State Tables.


    o State synchronization across a link is considered to be achieved
      when a node reaches the ESTAB state.


















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RFC 1953                   IFMP Specification                   May 1996


State Tables

   State: SYNSENT

+======================================================================+
|     Condition      |                Action               | New State |
+====================+=====================================+===========+
|    SYNACK && C     |  Update Peer Verifier; Send ACK     |   ESTAB   |
+--------------------+-------------------------------------+-----------+
|    SYNACK && !C    |            Send RSTACK              |  SYNSENT  |
+--------------------+-------------------------------------+-----------+
|        SYN         |  Update Peer Verifier; Send SYNACK  |  SYNRCVD  |
+--------------------+-------------------------------------+-----------+
|        ACK         |            Send RSTACK              |  SYNSENT  |
+======================================================================+

   State: SYNRCVD

+======================================================================+
|     Condition      |                Action               | New State |
+====================+=====================================+===========+
|    SYNACK && C     |  Update Peer Verifier; Send ACK     |   ESTAB   |
+--------------------+-------------------------------------+-----------+
|    SYNACK && !C    |            Send RSTACK              |  SYNRCVD  |
+--------------------+-------------------------------------+-----------+
|        SYN         |  Update Peer Verifier; Send SYNACK  |  SYNRCVD  |
+--------------------+-------------------------------------+-----------+
|    ACK && B && C   |              Send ACK               |   ESTAB   |
+--------------------+-------------------------------------+-----------+
|  ACK && !(B && C)  |            Send RSTACK              |  SYNRCVD  |
+======================================================================+

   State: ESTAB

+=======================================================================+
|     Condition       |                Action               | New State |
+=====================+=====================================+===========+
|   SYN || SYNACK     |            Send ACK (note 1)        |   ESTAB   |
+---------------------+-------------------------------------+-----------+
|   ACK && B && C     |            Send ACK (note 1)        |   ESTAB   |
+---------------------+-------------------------------------+-----------+
|  ACK && !(B && C)   |              Send RSTACK            |   ESTAB   |
+=======================================================================+


 Note 1: No more than one ACK should be sent within any time period of
        length defined by the timer.




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RFC 1953                   IFMP Specification                   May 1996


4. IFMP Redirection Protocol

   A sender encapsulates within an IPv4 packet all IFMP messages
   belonging to the Redirection Protocol.  The sender sends these
   messages to the unicast IP address of the peer at the other end of
   the link. The IP address of the peer is obtained from the adjacency
   protocol.  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.

   All IFMP Redirection Protocol messages 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                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Sequence Number                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                          Message Body                         ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Version
             The IFMP protocol version number, currently Version = 1.

   Op Code
             This field gives the message type.  Five message types are
             currently defined for the IFMP Redirection Protocol:

                 REDIRECT:     Op Code = 4
                 RECLAIM:      Op Code = 5
                 RECLAIM ACK:  Op Code = 6
                 LABEL RANGE:  Op Code = 7
                 ERROR:        Op Code = 8

   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



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RFC 1953                   IFMP Specification                   May 1996


             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).

   Sender Instance
             The sender's instance number for the link from the IFMP
             Adjacency Protocol.

   Peer Instance
             What the sender believes is the peer's current instance
             number for the link from the IFMP Adjacency protocol.

   Sequence Number
             The sender must increment by one, modulo 2**32, for every
             IFMP Redirection Protocol message sent across a link.  It
             allows the receiver to process IFMP Redirection Protocol
             messages in order.  The Sequence Number is set to zero when
             a node resets the link.

   Message Body
             Contains a list of one or more IFMP Redirection Protocol
             message elements.  All of the message elements in the list
             have the same message type because the Op Code field
             applies to the entire IFMP message.  The number of message
             elements included in a single packet must not cause the
             total size of the IFMP message to exceed the MTU size of
             the underlying data link.  Only a single message element is
             permitted in a Label Range message or in an Error message.

   No IFMP Redirection Protocol messages can be sent across a link until
   the IFMP Adjacency Protocol has achieved state synchronization across
   that link.  All IFMP Redirection Protocol messages received on a link
   that does not currently have state synchronization must be discarded.
   For every received IFMP Redirection Protocol message the receiver
   must check the Source IP Address from the IP header, the Sender
   Instance, and the Peer Instance.  The incoming message must be
   discarded if the Sender Instance and the Source IP Address fields do
   not match the values stored by the "Update Peer Verifier" operation
   of the IFMP Adjacency Protocol for the port on which the message is
   received.  The incoming message must also be discarded if the Peer
   Instance field does not match the current value for the Sender
   Instance of the IFMP Adjacency Protocol.








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RFC 1953                   IFMP Specification                   May 1996


4.1 Redirect Message

   The Redirect Message element is used to instruct an adjacent node to
   attach one or more given labels to packets belonging to one or more
   specified flows each for a specified period of time.  The Redirect
   message is not acknowledged.

   Each Redirect message element has 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Flow Type   | Flow ID Length|           Lifetime            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Label                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                         Flow Identifier                       ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Flow Type
             Specifies the Flow Type of the flow identifier contained in
             the Flow Identifier field.

   Flow ID Length
             Specifies the length of the Flow Identifier field in
             integer multiples of 32 bit words.

   Lifetime field
             Specifies the length of time, in seconds, for which this
             redirection is valid.  The association of flow identifier
             and label should be discarded at a time no greater than
             that specified by the Lifetime field.  A value of zero is
             not valid.

   Label field
             Contains a 32 bit label.  The format of the label is
             dependent upon the type of physical link across which the
             Redirect message is sent.  (The format of the label for ATM
             data links is specified in [ENCAP].)

   Flow Identifier
             Identifies the flow with which the specified label should
             be associated.  The length of the Flow Identifier field
             must be an integer multiple of 32 bit words to preserve 32
             bit alignment.



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RFC 1953                   IFMP Specification                   May 1996


   A node can send an IFMP message containing one or more Redirect
   message elements across a link to its upstream neighbor.  Each
   Redirect message element requests that the upstream neighbor
   associate a given link-level label to packets belonging to a
   specified flow for up to a specified period of time.  A node
   receiving an IFMP message that contains one or more Redirect message
   elements from an adjacent downstream neighbor can choose to ignore
   any or all of the Redirect message elements.  Neither the IFMP
   message nor any of the Redirect message elements are acknowledged.
   If the node chooses to accept a particular Redirect message element
   and to redirect the specified flow, it should attach the label
   specified in the Redirect message element to all further packets sent
   on that flow until it chooses to do so no longer, or until the
   specified lifetime expires.  While the flow remains redirected, the
   encapsulation specified by the definition of the Flow Type given in
   the Redirect message element must be used for all packets belonging
   to that flow.  If the label in a Redirect message element is outside
   the range that can be handled across the relevant link, a Label Range
   message can be returned to the sender.  The Label Range message
   informs the sender of the Redirect message of the range of labels
   that can be sent across the link.

   If a Redirect message element is received specifying a flow that is
   already redirected, the Label field in the received Redirect message
   element must be checked against the label stored for the redirected
   flow.  If they agree, the lifetime of the redirected flow is reset to
   that contained in the Redirect message element.  If they disagree,
   the Redirect message element is ignored, and the flow returned to the
   default state.  There is a minimum time between Redirect message
   elements specifying the same flow.  The default value is one second.

   If a receiving node detects an error in any of the fields of a
   Redirect message element, the node must discard that message element
   without affecting any other Redirect message elements in the same
   IFMP message.  The receiver should return an error message to the
   sender only in the case that the receiver does not understand the
   version of the IFMP protocol in the received IFMP message or does not
   understand a Flow Type in any of the Redirect message elements.  An
   Error Message should be returned for each Flow Type that is not
   understood.

4.2 Reclaim Message

   The Reclaim message element is used by a node to instruct an adjacent
   upstream node to unbind one or more flows from the labels to which
   they are currently bound, and to release the labels.





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   Each Reclaim message element has 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Flow Type   | Flow ID Length|           Reserved            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Label                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                         Flow Identifier                       ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Flow Type