rfc2067.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

                       A possible HIPPI configuration











Renwick                     Standards Track                     [Page 6]

RFC 2067                     IP over HIPPI                  January 1997


   A single HIPPI-SC switch has a "non-blocking" characteristic, which
   means there is always a path available from any Source to any
   Destination.  If the network consists of more than one switch, the
   path from a Source to a Destination may include a HIPPI link between
   switches.  If this link is used by more than one Source/Destination
   pair, a "blocking" network is created: one Source may be blocked from
   access to a Destination because another Source is using the link it
   shares.  Strategies for establishing connections may be more
   complicated on blocking networks than on non-blocking ones.

   This memo does not take blocking issues into account, assuming that
   the HIPPI LAN consists of one HIPPI-SC switch or, if the network is
   more complex than that, it presents no additional problems that a
   node must be aware of.

5  Protocol

5.1  Packet Format

   The HIPPI packet format for Internet datagrams SHALL conform to the
   HIPPI-FP and HIPPI-LE draft standards, with further restrictions as
   imposed by this memo.  Because this memo is more restrictive than the
   ANSI standards, it is possible to send encapsulated IP datagrams that
   conform to the ANSI standards, but are illegal according to this
   memo.  Destinations may either accept or ignore such datagrams.

   To summarize the additional restrictions on ANSI standards found
   here:

           Any short burst must be the last burst of the packet.
           Leading short bursts are not permitted.

           Nonzero values for the HIPPI-FP D2_Offset field are not
           permitted.

           The D1_AreaSize SHALL be 3 (64-bit words).  No D1 Fill is
           permitted.

   Note: Although this document is for IP over HIPPI, the encapsulation
   described below accommodates ARP as well.

   The HIPPI-FP D1_Area SHALL contain the HIPPI-LE header.  The HIPPI-FP
   D2_Area, when present, SHALL contain one IEEE 802.2 Type 1 LLC
   Unnumbered Information (UI) PDU.  Support of IEEE 802.2 XID, TEST and
   Type 2 PDUs is not required on HIPPI, and Destinations that receive
   these PDUs may either ignore them or respond correctly according to
   IEEE 802.2 requirements.




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RFC 2067                     IP over HIPPI                  January 1997


   The length of a HIPPI packet, including trailing fill, SHALL be a
   multiple of eight bytes as required by HIPPI-LE.

   +----------+-----------+---------------------+-----------   ------+
   |          |           |                     |              0 - 7 |
   | HIPPI-FP | HIPPI-LE  | IEEE 802.2 LLC/SNAP | IP . . .     bytes |
   |(8 bytes) |(24 bytes) |      (8 bytes)      |               fill |
   +----------+-----------+---------------------+-----------   ------+

                          HIPPI Packet Structure

        ULP-id (8 bits) SHALL contain 4.

        D1_Data_Set_Present (1 bit) SHALL be set.

        Start_D2_on_Burst_Boundary (1 bit) SHALL be zero.

        Reserved (11 bits) SHALL contain zero.

        D1_Area_Size (8 bits) SHALL be sent as 3.

        D2_Offset (3 bits) SHALL be zero.

        D2_Size (32 bits) Shall contain the number of bytes in the
        IEEE 802.2 LLC Type 1 PDU, or zero if no PDU is present.  It
        SHALL NOT exceed 65,288.  This value includes the IEEE 802.2
        LLC/SNAP header and the IP datagram.  It does not include
        trailing fill bytes.  (See "MTU", below.)

HIPPI-LE Header

   FC (3 bits) SHALL contain zero unless otherwise defined by local
   administration.

   Double_Wide (1 bit) SHALL contain one if the Destination associated
   with the sending Source supports 64 bit HIPPI operation.  Otherwise
   it SHALL contain zero.

   Message_Type (4 bits) contains a code identifying the type of HIPPI-
   LE PDU.  Defined values are:

              0  Data PDU
              1  Address Resolution Request PDU (AR_Request)
              2  Address Resolution Response PDU (AR_Response)
              3  Self Address Resolution Request PDU (AR_S_Request)
              4  Self Address Resolution Response PDU (AR_S_Response)





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RFC 2067                     IP over HIPPI                  January 1997


   Destination_Switch_Address is a 24-bit field containing the
   Switch Address of the Destination if known, otherwise zero.
   If the address comprises less than 24 bits, it SHALL be right
   justified (occupying the least significant bits) in the
   field.

   Destination_Address_Type (4 bits) and Source_Address_Type (4
   bits) contain codes identifying the type of addresses in the
   Destination_Switch_Address and Source_Switch_Address fields
   respectively.  Defined values (binary) are:

                 0  Unspecified
                 1  HIPPI-SC Source Route (24 bits)
                 2  HIPPI-SC Address (12 bits)

   Source_Switch_Address is a 24-bit field containing the Switch
   Address of the Source.  If the address comprises less than 24
   bits, it SHALL be right justified (occupying the least
   significant bits) in the field.

   Reserved (16 bits) SHALL contain zero.

   Destination_IEEE_Address (48 bits) SHALL contain the 48 bit
   Universal LAN MAC Address of the Destination if known,
   otherwise zero.

   LE_Locally_Administered (16 bits) SHALL contain zero UNLESS
   otherwise defined by local administration.

   Source_IEEE_Address (48 bits) SHALL contain the 48 bit
   Universal LAN MAC Address of the Source if known, otherwise
   zero.

IEEE 802.2 LLC

   The IEEE 802.2 LLC Header SHALL begin in the first byte of the
   HIPPI-FP D2_Area.

   SSAP (8 bits) SHALL contain 170 ('AA'h).

   DSAP (8 bits) SHALL contain 170 ('AA'h).

   CTL (8 bits) SHALL contain 3 (Unnumbered Information).

SNAP

   Organization Code (24 bits) SHALL be zero.




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RFC 2067                     IP over HIPPI                  January 1997


   EtherType (16 bits) SHALL be set as defined in Assigned Numbers [8]:
   IP = 2048 ('0800'h), ARP = 2054 ('0806'h), RARP = 32,821 ('8035'h).

      31    28        23  21          15        10     7         2   0
      +-----+---------+-+-+-----------+---------+-----+---------+-----+
    0 |      04       |1|0|       Reserved      |      03       |  0  |
      +---------------+-+-+---------------------+---------------+-----+
    1 |                             (n+8)                             |
      +-----+-+-------+-----------------------------------------------+
    2 |[LA] |W|M_Type |          Destination_Switch_Address           |
      +-----+-+-------+-----------------------------------------------+
    3 | D_A_T | S_A_T |             Source_Switch_Address             |
      +-------+-------+---------------+-------------------------------+
    4 |            Reserved           |  [Destination_IEEE_Address]   |
      +-------------------------------+                               |
    5 |                                                               |
      +-------------------------------+-------------------------------+
    6 |             [LA]              |     [Source_IEEE_Address]     |
      +-------------------------------+                               |
    7 |                                                               |
      +---------------+---------------+---------------+---------------+
    8 |       AA      |      AA       |       03      |       00      |
      +---------------+---------------+---------------+---------------+
    9 |       00      |      00       |         [EtherType]           |
      +---------------+---------------+---------------+---------------+
   10 |Message byte 0 |Message byte 1 |Message byte 2 | . . .         |
      +---------------+---------------+---------------+---            |
      |                            .  .  .
                                                                      |
      |        -------+---------------+---------------+---------------+
      |         . . . |  byte (n-2)   |  byte (n-1)   |     FILL      |
      +---------------+---------------+---------------+---------------+
   N-1|      FILL     |     FILL      |     FILL      |     FILL      |
      +---------------+---------------+---------------+---------------+

















Renwick                     Standards Track                    [Page 10]

RFC 2067                     IP over HIPPI                  January 1997


                            HIPPI Packet Format

              Words 0-1:  HIPPI-FP Header
              Words 2-7:  D1 Area (HIPPI-LE Header)
              Words 8-9:  D2 Area (IEEE 802.2 LLC/SNAP)
              Words 10-(N-1):  D2 Area (IP message)
              (n) is the number of bytes in the IP message.
              [LA] fields are zero unless used otherwise locally.
              Abbreviations:  "W"      = Double_Wide field;
                              "M_Type" = Message_Type field;
                              "D_A_T"  = Destination_Address_Type;
                              "S_A_T"  = Source_Address_Type;
              [FILL] bytes complete the HIPPI packet to an even
              number of 32 bit words.  The number of fill bytes
              is not counted in the data length.

IEEE 802.2 Data

   The IEEE 802.2 Data SHALL begin in the byte following the EtherType
   field.  Fill bytes SHALL be used following the Data as necessary to
   make the number of bytes in the packet a multiple of 8.  In
   accordance with HIPPI-FP, the amount of this fill is not included in
   the D2_Size value in the HIPPI- FP Header.

   The order of the bytes in the data stream is from higher numbered to
   lower numbered data signal (left to right) within the HIPPI word, as
   specified in HIPPI-FP Clause 7, "Word and byte formats."  With the
   1600 megabit/second data rate option (64 bit) bits 32 through 63 are
   on Cable B, so that the four bytes on Cable B come logically before
   those on Cable A.  Within each byte, the most significant bit is the
   highest numbered signal.

5.2  48 bit Universal LAN MAC Addresses

   IEEE Standard 802.1A specifies the Universal LAN MAC Address.  The
   globally unique part of the 48 bit space is administered by the IEEE.
   Each node on a HIPPI-SC LAN should be assigned a ULA.  Multiple ULAs
   may be used if a node contains more than one IEEE 802.2 LLC protocol
   entity.












Renwick                     Standards Track                    [Page 11]

RFC 2067                     IP over HIPPI                  January 1997


   The format of the address within its 48 bit HIPPI-LE fields follows
   IEEE 802.1A canonical bit order and HIPPI-FP bit and byte order:

     31              23              15               7              0
     +-------------------------------+---------------+---------------+
     |      (not used for ULA)       |ULA byte 0 |L|G|  ULA byte  1  |
     +---------------+---------------+---------------+---------------+
     |  ULA byte  2  |  ULA byte  3  |  ULA byte  4  |  ULA byte  5  |
     +---------------+---------------+---------------+---------------+

                     Universal LAN MAC Address Format

        L (U/L bit) = 1 for Locally administered addresses, 0 for
        Universal.
        G (I/G bit) = 1 for Group addresses, 0 for Individual.

   The use of ULAs is optional, but encouraged.  Although ULAs are not
   used by HIPPI-SC switches, they may be helpful for HIPPI Switch
   Address resolution, and for distinguishing between multiple logical
   entities that may exist within one node.  They may also be used by
   gateway devices that replace HIPPI hardware headers with the MAC
   headers of other LANs.  Carrying the ULAs in the HIPPI header may
   simplify these devices, and it may also help if HIPPI is used as an
   interface to some future HIPPI based LAN that uses ULAs for
   addressing.