rfc2834.txt

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                                                    HIPPI-LE
       "D_A_T"  = Destination_Address_Type SHALL be 2



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RFC 2834          ARP and IP Broadcast over HIPPI-800           May 2000


       "S_A_T"  = Source_Address_Type      SHALL be 2
      [FILL] bytes complete the HIPPI message to an even
      number of 32 bit words.  The number of fill bytes
      is not counted in the data length.

6.2 HIPPI Hardware Address Formats and Requirements

   For HIPPI-800, the Hardware Address is a 10-byte unit that SHALL
   contain the Switch Address AND the ULA. The format of a hardware
   address is:

   31              23              15               7              0
   +---------------+---------------+-------+-------+---------------+
   |   Mode Byte   |      00       |   0   |  X    |      XX       |
   +---------------+---------------+-------+-------+---------------+
   |   ULA byte 0  |   ULA byte 1  |   ULA byte 2  |   ULA byte 3  |
   +---------------+---------------+---------------+---------------+
   |   ULA byte 4  |   ULA byte 5  |
   +---------------+---------------+

   Where "XXX" is the 12 bit HIPPI logical address defined in HIPPI-SC
   [4]. Details on ULA see next section.

   Two switch addresses are considered to be the same when they have the
   same 12 bit destination HIPPI logical address.

   NOTE: In the case of HIPPI-6400, the hardware address is ONLY the 6-
   byte ULA. Therefore the length of the hardware address clearly
   defines which version of HIPPI is being used.

6.2.1 48-bit Universal LAN MAC Addresses

   IEEE Standard 802.1A [11] specifies the Universal LAN MAC Address
   format. The globally unique part of the 48-bit space is administered
   by the IEEE.  Each port on a HIPPI-SC LAN SHOULD be assigned a ULA.
   Multiple ULAs may be used if a port contains more than one IEEE 802.2
   LLC protocol entity.

   The format of the HIPPI hardware address within its HARP message
   follows IEEE 802.1A canonical bit order and HIPPI-FP bit and byte
   order. For example the requester's ULA part of the HIPPI hardware
   address would decompose to:









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RFC 2834          ARP and IP Broadcast over HIPPI-800           May 2000


   31              23              15               7              0
   +---------------+---------------+---------------+---------------+
   |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 RECOMMENDED. The use of ULAs is
   REQUIRED if a port wishes to interoperate with a conventional
   network.

   ULAs may also be used by bridging devices that replace HIPPI hardware
   headers with the MAC headers of other LANs.

6.3 HARP and InHARP Message Formats

   The HARP protocols use the HIPARP hardware type (ar$hrd) [16],
   protocol type (ar$pro), and operation code (ar$op) data formats as
   the ARP, and InARP protocols [15,7]. In addition, HARP makes use of
   an additional operation code for ARP_NAK introduced with [12]. The
   remainder of the HARP/InHARP message format is different than the
   ARP/InARP message format defined in [15,7,10] and it is also
   different from the format defined in the first "IP and ARP on HIPPI"
   RFC-1374 [14].

   HARP messages SHALL be transmitted with the HIPARP hardware type code
   of 28 (decimal). Furthermore, HARP messages SHALL  be accepted if
   received with hardware type codes of either 28, 1 or 6 (decimal).

   The HARP message has several fields that have the following format
   and values:

   Data sizes and field meaning:
     ar$hrd  16 bits  Hardware type
     ar$pro  16 bits  Protocol type of the protocol fields below
     ar$op   16 bits  Operation code (request, reply, or NAK)
     ar$pln   8 bits  byte length of each protocol address
     ar$rhl   8 bits  requester's HIPPI hardware address length (q)
     ar$thl   8 bits  target's HIPPI hardware address length (x)
     ar$rpa  32 bits  requester's protocol address
     ar$tpa  32 bits  target's protocol address



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RFC 2834          ARP and IP Broadcast over HIPPI-800           May 2000


     ar$rha  qbytes   requester's HIPPI Hardware address
     ar$tha  xbytes   target's HIPPI Hardware address

   Where :
     ar$hrd  - SHALL contain 28. (HIPARP)

     ar$pro  - SHALL contain the IP protocol code 2048 (decimal).

     ar$op   - SHALL contain the operational value (decimal):
               1  for   HARP_REQUESTs
               2  for   HARP_REPLYs
               8  for InHARP_REQUESTs
               9  for InHARP_REPLYs
               10 for   HARP_NAK

     ar$pln  - SHALL contain 4.

     ar$rln  - SHALL contain 10 IF this is a HIPPI-800 HW address
               ELSE, for HIPPI-6400, it SHALL contain 6.

     ar$thl  - SHALL contain 10 IF this is a HIPPI-800 HW address
               ELSE, for HIPPI-6400, it SHALL contain 6.

     ar$rha  - in requests and NAKs it SHALL contain the requester's
               HW address. In replies it SHALL contain the target
               port's HW address.

     ar$rpa  - in requests and NAKs it SHALL contain the requester's IP
               address if known, otherwise zero.
               In other replies it SHALL contain the target
               port's IP address.

     ar$tha  - in requests and NAKs it SHALL contain the target's
               HW address if known, otherwise zero.
               In other replies it SHALL contain the requester's
               HW addressA.

     ar$tpa  - in requests and NAKs it SHALL contain the
               target's IP address if known, otherwise zero.
               In other replies it SHALL contain the requester's
               IP address.

   The format of the six bytes of the ULA SHALL be the same as required
   in the HIPPI-LE header (see section 6.2), except for the alignment of
   the ULAs with respect to the 32-bit HIPPI word, which is different
   between ARP and HIPPI-LE.  No bit reversal is necessary as is
   required with FDDI.




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RFC 2834          ARP and IP Broadcast over HIPPI-800           May 2000


      31    28        23  21          15        10     7         2   0
      +-----+---------+-+-+-----------+---------+-----+---------+-----+
    0 |      04       |1|0|         000         |      03       |  0  |
      +---------------+-+-+---------------------+---------------+-----+
    1 |                              45                               |
      +-----+-+-------+-----------------------+-----------------------+
    2 |[LA] |W|MsgT= 0|          000          |   Dest. Switch Addr   |
      +-----+-+-------+-----------------------+-----------------------+
    3 |   2   |   2   |          000          |  Source Switch Addr   |
      +---------------+---------------+-------+-----------------------+
    4 |             00 00             |                               |
      +-------------------------------+                               |
    5 |                      Destination ULA                          |
      +-------------------------------+-------------------------------+
    6 |             [LA]              |                               |
      +-------------------------------+                               |
    7 |                         Source ULA                            |
      +===============+===============+===============+===============+
    8 |       AA      |      AA       |       03      |       00      |
      +---------------+---------------+---------------+---------------+
    9 |       00      |      00       |        Ethertype (2054)       |
      +---------------+---------------+-------------------------------+
   10 |              hrd (28)         |           pro (2048)          |
      +---------------+---------------+---------------+---------------+
   11 |             op (ar$op)        |     pln (6)   |   rhl (q)     |
      +---------------+---------------+---------------+---------------+
   12 |    thl = (x)  |   Requester IP Address upper  (24 bits)       |
      +---------------------------------------------------------------+
   13 | Req. IP lower |      Target IP Address upper  (24 bits)       |
      +---------------+-----------------------------------------------+
   14 | Tgt. IP lower | Requester HIPPI Hardware Address bytes 0 - 2  |
      +---------------+-----------------------------------------------+
   15 |         Requester HIPPI Hardware Address bytes 3 - 6          |
      +-----------------------------------------------+---------------+
   16 |         Requester HW Address bytes 7 - q      | Tgt HW byte 0 |
      +---------------+---------------+---------------+---------------+
   17 |          Target  HIPPI Hardware Address bytes 1 - 4           |
      +---------------------------------------------------------------+
   18 |          Target  HIPPI Hardware Address bytes 5 - 8           |
      +---------------+---------------+---------------+---------------+
   19 |Tgt HW byte 9-x|     FILL      |     FILL      |     FILL      |
      +---------------+---------------+---------------+---------------+
                           HARP - InHARP Message








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RFC 2834          ARP and IP Broadcast over HIPPI-800           May 2000


6.3.1 Example Message encodings:

   HARP_REQUEST message
         HARP ar$op   = 1 (HARP_REQUEST)
         HARP ar$rpa  = IPy                HARP ar$tpa  = IPa
         HARP ar$rha  = SWy ULAy           HARP ar$tha  = 0 **
         ** is what we would like to find out

   HARP_REPLY message format
         HARP ar$op   = 2 (HARP_REPLY)
         HARP ar$rpa  = IPa                HARP ar$tpa  = IPy
         HARP ar$rha  = SWa ULAa *         HARP ar$tha  = SWy ULAy
         * answer we were looking for

   InHARP_REQUEST message format
         HARP ar$op    = 8 (InHARP_REQUEST)
         HARP ar$rpa   = IPy               HARP ar$tpa   = 0 **
         HARP ar$rha   = SWy ULAy          HARP ar$tha   = SWa ULAa
         ** is what we would like to find out

   InHARP_REPLY message format
         HARP ar$op    = 9 (InHARP_REPLY)
         HARP ar$rpa   = IPs *             HARP ar$tpa   = IPy
         HARP ar$rha   = SWa ULAa          HARP ar$tha   = SWy ULAy
         * answer we were looking for

6.3.2 HARP_NAK message format

   The HARP_NAK message format is the same as the received HARP_REQUEST
   message format with the operation code set to HARP_NAK; i.e. the
   HARP_REQUEST message data is copied byte for byte for transmission
   with the HARP_REQUEST operation code changed to the HARP_NAK value.
   HARP makes use of an additional operation code for HARP_NAK. Hence,
   HARP_NAK MUST be implemented.

6.3.3 Combined HIPPI-LE and HARP message addresses

   The combined HIPPI-LE/HARP message contains ten addresses, two for
   the destination and two for the source of the message, three for the
   requester and three for the target:

      Destination Switch Address  (HIPPI-LE)
      Destination ULA             (HIPPI_LE)

      Source Switch Address       (HIPPI-LE)
      Source ULA                  (HIPPI-LE)





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RFC 2834          ARP and IP Broadcast over HIPPI-800           May 2000


      Requester IP Address        (HARP)
      Requester ULA               (HARP)
      Requester Switch Address    (HARP)

      Target IP Address           (HARP)
      Target ULA                  (HARP)
      Target Switch Address       (HARP)

   Examples:

   The following relations are true for a HARP_REQUEST and
   InHARP_REQUESTs.

      LIS without broadcast -  Dest SW Addr   = HARP server SW Addr
      (with HARP server)       Dest ULA       = HARP server ULA
                               Source SW Addr = Requester's SW Addr
                               Source ULA     = Requester's ULA

7  Broadcast and Multicast

   HIPPI-SC does not require switches to support broadcast. Broadcast
   support has therefore been absent from many HIPPI networks.

   During its registration phase, every port, including HARP server(s),
   discover if the underlying medium is capable of broadcast (see
   section 5.1.2). Should this not be the case, then the HARP server(s)