rfc2625.txt

<VC++网络游戏建摸与实现>源代码

             Destination ID <Word 0, bit 23:0>: D_ID = 0xFF-FF-FF

             Sequence Initiative <Word 2, bit23>: SI=0

             Last Sequence <Word 2, bit 20>: LS=1

             End Sequence <Word 2, bit 19>: ES=1.

      3. A compliant ARP Broadcast Sequence frame SHALL include the
         Network_Header with destination MAC address set to
         0xFF-FF-FF-FF-FF-FF and with NAA = b'0001'

      4. The destination port recognizing its IP address in
         the ARP packet SHALL respond with an ARP Reply.



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RFC 2625             IP and ARP over Fibre Channel             June 1999


5.  FARP

5.1 Scope

   FC Layer Mapping between the WW_PN and the Port_ID is independent of
   the ARP mechanism and is more closely associated with the details of
   the FC protocols. Name Server and FC Address Resolution Protocol
   (FARP) are two formal mechanisms that can be used to create and
   maintain WW_PN to Port_ID tables.

   FARP is a method using Extended Link Service (ELS) commands that
   resolves <WW_PN, Port_ID> mappings. The WW_PN to Port_ID address
   resolution using FARP is especially useful in instances where the
   Login table entries at a node expire and a Name Server is not
   available.  It is outside the scope of this document to describe Name
   Server. (See [14].)

   Additional address matching mechanisms that resolve <WW_NN, Port_ID>
   and <IP addr., Port_ID> mapping have been added to FARP. These
   additional mechanisms are optional and described in Appendix A.
   Direct IP address to Port_ID mapping is useful in applications where
   there is no visibility of the MAC address.

   Other less formal FC Layer Mapping mechanisms are described in
   Appendix C.

   Since Port_IDs are volatile, all mapped Port_IDs  at all times MUST
   be valid before use. There are many events that can invalidate this
   mapping. Appendix D discusses conditions when such a validation is
   required.

5.2 FARP Overview

   The FARP protocol uses two ELS commands - FARP-REQ and FARP-REPLY.

   Note: In the following discussion 'Requester' means the node
      issuing the FARP-REQ ELS message; 'Responder' means the
      node replying to the request by sending the FARP-REPLY
      command.

   The FARP-REQ ELS Broadcast Request command is used to retrieve a
   specific node's current Port_ID given its unique WW_PN. This Port_ID
   is sent in a FARP-REPLY unicast command.

   The FARP-REQ may indicate that the Responder:






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RFC 2625             IP and ARP over Fibre Channel             June 1999


          - Perform only a Login with it (Requester) or,
          - Send only a FARP-REPLY or,
          - Perform a Login and send a FARP-REPLY.

   No sequence initiative is transferred with the FARP-REQ and therefore
   no Reply (ACCEPT or REJECT) follows this command.

   Since a Sequence Initiative is transferred with the FARP-REPLY,
   either a ACCEPT or REJECT follows this command as a response.

   Reception of a FARP-REQ requires a higher level entity at the
   responding node to send a FARP-REPLY or perform a Port Login.

   You do not have to be logged in to issue a FARP Request. Also, you do
   not have to be logged in to the FARP Requester to issue a FARP-REPLY.

   The FARP Protocol Steps:

        FARP-REQ (ELS broadcast) Request Sequence

             (No Reply Sequence)

        FARP-REPLY (ELS command) Sequence

             Accept/Reject Reply Sequence

   The FARP Protocol Format [2] and Size:

          FT_1, 76-bytes fixed size

   The FARP Protocol Addressing:

      - In a FARP-REQ, the S_ID in the FC Header designates the
      Requester's Port ID. The D_ID in the FC Header is the broadcast
      identifier 0xFF-FF-FF.

      - In a FARP-REPLY, the S_ID in the FC Header designates the
      Responder's Port_ID. The D_ID in the FC Header is the Requester's
      Port_ID.












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RFC 2625             IP and ARP over Fibre Channel             June 1999


5.3 FARP Command Format

   FARP-REQ and FARP-REPLY commands have identical formats (76-bytes
   fixed size) and fields but use different command codes. See tables
   below.

 +---------------------------------------------------------------------+
 |                         FARP-REQ Command                            |
 +-------------------------------------+---------+---------------------+
 |               Field                 | Size    |   Remarks           |
 |                                     | (Bytes) |                     |
 +-------------------------------------+---------+---------------------+
 | 0x54-00-00-00                       |   4     | Request Command Code|
 +-------------------------------------+---------+---------------------+
 | Match Address Code Points           |   1     | Indicates Address   |
 |                                     |         | Matching  Mechanism |
 +-------------------------------------+---------+---------------------+
 | Port_ID of Requester                |   3     | Supplied by         |
 |                                     |         | Requester =         |
 |                                     |         | S_ID in FC Header   |
 +-------------------------------------+---------+---------------------+
 | Responder Flags                     |   1     | Response Action to  |
 |                                     |         | be taken            |
 +-------------------------------------+---------+---------------------+
 | Port_ID of Responder                |   3     | Set to 0x00-00-00   |
 +-------------------------------------+---------+---------------------+
 | WW_PN of Requester                  |   8     |Supplied by Requester|
 +-------------------------------------+---------+---------------------+
 + WW_NN of Requester                  |   8     |OPTIONAL;            |
 |                                     |         |See Appendix A       |
 +-------------------------------------+---------+---------------------+
 | WW_PN of Responder                  |   8     |Supplied by Requester|
 +-------------------------------------+---------+---------------------+
 | WW_NN of Responder                  |   8     |OPTIONAL; see App. A |
 +-------------------------------------+---------+---------------------+
 | IP Address of Requester             |   16    |OPTIONAL; see App. A |
 +-------------------------------------+---------+---------------------+
 | IP Address of Responder             |   16    |OPTIONAL; see App. A |
 +-------------------------------------+---------+---------------------+












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RFC 2625             IP and ARP over Fibre Channel             June 1999


 +---------------------------------------------------------------------+
 |                         FARP-REPLY Command                          |
 +-------------------------------------+---------+---------------------+
 |               Field                 | Size    |   Remarks           |
 |                                     | (Bytes) |                     |
 +-------------------------------------+---------+---------------------+
 | 0x55-00-00-00                       |   4     | Reply Command Code  |
 +-------------------------------------+---------+---------------------+
 | Match Address Code Points           |   1     | Not Used and        |
 |                                     |         | Unchanged from the  |
 |                                     |         | FARP-REQ            |
 +-------------------------------------+---------+---------------------+
 | Port_ID of Requester                |   3     | Extracted from      |
 |                                     |         | FARP-REQ            |
 +-------------------------------------+---------+---------------------+
 | Responder Flags                     |   1     | Not Used  and       |
 |                                     |         | Unchanged from the  |
 |                                     |         | FARP-REQ            |
 +-------------------------------------+---------+---------------------+
 | Port_ID of Responder                |   3     | Supplied by         |
 |                                     |         | Responder =         |
 |                                     |         | S_ID in FC Header   |
 +-------------------------------------+---------+---------------------+
 |WW_PN of Requester                   |   8     |Supplied by Requester|
 +-------------------------------------+---------+---------------------+
 |WW_NN of Requester                   |   8     |OPTIONAL; see App. A |
 +-------------------------------------+---------+---------------------+
 |WW_PN of Responder                   |   8     |Supplied by Requester|
 +-------------------------------------+---------+---------------------+
 |WW_NN of Responder                   |   8     |OPTIONAL; see App. A |
 +-------------------------------------+---------+---------------------+
 |IP Add. of Requester                 |   16    |OPTIONAL; see App. A |
 +-------------------------------------+---------+---------------------+
 |IP Address of Responder              |   16    |OPTIONAL; see App. A |
 +-------------------------------------+---------+---------------------+

   Following is a description of the address fields in the FARP
   Commands.

   Port_ID of Requester:

   It is the 24-bit Port_ID used in the S_ID field of the FC Header of a
   FARP-REQ.  It is supplied by the Requester in a FARP-REQ and retained
   in a FARP-REPLY.







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RFC 2625             IP and ARP over Fibre Channel             June 1999


   Port_ID of Responder:

   It is the 24-bit Port_ID used in the S_ID field of the FC Header of a
   FARP-REPLY.  It SHALL be set to 0x00-00-00 in a FARP-REQ. It is
   supplied by the Responder in a FARP-REPLY.

   WW_PN:

   This address field is used with the b'001', b'011', b'101, b'111',
   Match Address Code Points. See Match Address Code Point Table below.
   The Requester supplies the unique 8-byte WW_PN of the Requester and
   the Responder. It is retained in a FARP-REPLY.

   WW_NN:

   The WW_NN address field is used with Match Address Code Points
   b'010', b'011', b'110', and b'111', which are all optional. Its usage
   is fully described in Appendix A. When the WW_NN field is not used it
   SHALL be either set to '0' or a valid non-zero address.

   IPv4:

   The IPv4 address field is used with the Match Address Code Points
   b'100', b'101', b'110', and b'111', which are all optional. Its usage
   is fully described in Appendix A. When the IP Address field is not
   used it SHALL be either set to '0' or a valid IP address. A valid IP
   address consists of the 32-bit IPv4 Address with the upper 96 bits
   set to '0'.

5.4 Match Address Code Points

   For each receipt of the FARP-REQ Broadcast ELS, the recipients match
   one or more addresses based on the encoded bits of the "FARP Match
   Address Code Points" field shown in the table below. FARP operation
   with the Match Address Code Point equal to b'001' is described in
   this section. Other code points are OPTIONAL and are discussed in
   Appendix A. The upper 5 bits of the Match Address Code Point byte are
   unused and their use is not currently defined.













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RFC 2625             IP and ARP over Fibre Channel             June 1999


 +------------------------------------------------------------------+
 |                     Match Address Code Points                    |
 +------------------------------------------------------------------+
 |   LSBits  |     Bit name       |           Action                |
 +-----------+--------------------+---------------------------------+
 |    000    | Reserved           |                                 |
 +-----------+--------------------+---------------------------------+
 |    001    | MATCH_WW_PN        | If 'WW_PN of Responder' =       |
 |           |                    | Node's WW_PN then respond       |
 +-----------+--------------------+---------------------------------+