rfc2835.txt

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   server 00:10:3B:FF:FF:E0.

   Therefore, the HRAL entries are sorted in the following order:
   1st     : broadcast address            (FF:FF:FF:FF:FF:FF) REQUIRED
   2nd     : official HARP server address (00:10:3B:FF:FF:E0) REQUIRED
   3rd & on: any additional HARP server addresses will be     OPTIONAL
             sorted in decreasing order.

   Manual configuration of the addresses and address lists presented in
   this section is implementation dependent and beyond the scope of this
   memo.  However, prior to use by any service or operation detailed in
   this memo, clients MUST have HRAL address(es) configured as
   appropriate for their LIS.






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RFC 2835            IP and ARP over HIPPI-6400 (GSN)            May 2000


4.  Internet Protocol

4.1 Packet format

   The HIPPI-6400 packet format for Internet datagrams [15] shall
   conform to the HIPPI-6400-PH standard [1].  The length of a HIPPI-
   6400-PH packet, including headers and trailing fill, shall be a
   multiple of 32 bytes as required by HIPPI-6400-PH.

   All IP Datagrams shall be carried on HIPPI-6400-PH Virtual Channel 1
   (VC1). Since HIPPI-6400-PH has a 32-byte granularity, IP Datagrams
   MUST be padded to a 32-byte granularity prior to sending. Added
   padding is transparent to IP and is not reflected in the length field
   of the IP header.

   D_ULA   Destination ULA SHALL be the ULA of the destination port.

   S_ULA   Source ULA SHALL be the ULA of the requesting port.

   M_len   Set to the IEEE 802 packet (e.g. IP or HARP message)
           length + 8 Bytes to account for the LLC/SNAP header length.
           The HIPPI-6400-PH [1] length parameter shall not include
           the pad.

4.1.1 IEEE 802.2 LLC

   The IEEE 802.2 LLC Header SHALL begin in the first byte after M_len.

   The LLC values (in hexadecimal and decimal) SHALL be

   SSAP           0xAA     170  (8  bits)
   DSAP           0xAA     170  (8  bits)
   CTL            0x03       3  (8  bits)

   for a total length of 3 bytes. The 0x03 CTL value indicates the
   presence of a SNAP header.

4.1.2 SNAP

   The OUI value for Organization Code SHALL be 0x00-00-00 (3 bytes)
   indicating that the following two-bytes is an Ethertype.

   The Ethertype value SHALL be set as defined in Assigned Numbers [18]:

   IP           0x0800  2048  (16 bits)
   HARP = ARP = 0x0806  2054  (16 bits)

   The total size of the LLC/SNAP header is fixed at 8 bytes.



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RFC 2835            IP and ARP over HIPPI-6400 (GSN)            May 2000


4.1.3 HIPPI-6400 802 Packet diagrams

   The following diagram shows a HIPPI-6400 message carrying IEEE 802
   data.

   |31          |23          |15          |7          0|
   +------------+------------+------------+------------+ -------------
 0 |                                                   |
   |         D_ULA           +-------------------------+   HIPPI-6400
 1 |                         |                         |
   +-------------------------+        S_ULA            |      MAC
 2 |                                                   |
   +---------------------------------------------------+     header
 3 |                      M_len                        |
   +------------+------------+------------+------------+ -------------
 4 |   DSAP     |   SSAP     |    Ctl     |    Org     |    IEEE 802
   +------------+------------+------------+------------+    LLC/SNAP
 5 |   Org      |    Org     |       Ethertype         |     header
   +============+============+============+============+ =============
 6 | Msg byte 0 | Msg byte 1 | Msg byte 2 |    . . .   |    IEEE 802
   +---------------------------------------------------+      Data
                   Generic 802.1 data packet diagram

   The following diagram shows an IP datagram of length n with the FILL
   bytes ( value: 0x0 ). "<><>" indicates the micropacket separation. A
   HIPPI-6400-PH [1] micropacket is 32 bytes long.

   All IP (v4) [15] packets will always span two or more micropackets.
   The first micropacket has a TYPE = header. The second and any further
   micropackets have a TYPE = Data (see [1]).





















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RFC 2835            IP and ARP over HIPPI-6400 (GSN)            May 2000


    |31          |23          |15          |7          0|
    +------------+------------+------------+------------+ -------------
  0 |                                                   |
    |         D_ULA           +-------------------------+   HIPPI-6400
  1 |                         |                         |
    +-------------------------+        S_ULA            |      MAC
  2 |                                                   |
    +---------------------------------------------------+     header
  3 |                      M_len                        |
    +------------+------------+------------+------------+ -------------
  4 |     AA     |     AA     |     03     |    00      |    IEEE 802
    +------------+------------+------------+------------+    LLC/SNAP
  5 |     00     |     00     | Ethertype = 0x0800=2048 |     header
    +============+============+============+============+ =============
  6 | VER | HLEN |    TOS     |      Total Length       |
    +-----+------+------------+-----+-------------------+
  7 |           ID            | FLG |   Frag Offset     |
    +<><><><><><>+<><><><><><>+<><><><><><>+<><><><><><>+  IPv4 Header
  8 |    TTL     |   PROTO    |    Header Checksum      |
    +------------+------------+-------------------------+
  9 |                 Source IP Address                 |
    +---------------------------------------------------+
 10 |               Destination IP Address              |
    +---------------------------------------------------+
 11 |                    .   .   .                      |
    +---------------------------------------------------+
    |   . . .    | byte (n-2) | byte (n-1) |    FILL    |
    +------------+------------+------------+------------+
    |    FILL    |   FILL     |   FILL     |    FILL    |
    +------------+------------+------------+------------+
 M-1|    FILL    |   FILL     |   FILL     |    FILL    |
    +<><><><><><>+<><><><><><>+<><><><><><>+<><><><><><>+
                       IP v4 data packet diagram

   As shown in above figure the first eight bytes of the IP Datagram
   occupy the last eight bytes of the HIPPI-6400-PH [1] Header
   micropacket.

4.2  HIPPI-6400 Hardware address: Universal LAN MAC address (ULA)

   HIPPI-6400 uses Universal LAN MAC Addresses specified in IEEE
   Standard 802.1A [10] or a subset as defined in HIPPI-6400-SC [2].
   The globally unique part of the 48 bit space is administered by the
   IEEE. Each port on a HIPPI-6400-SC LAN MUST be assigned a ULA.
   Multiple ULAs may be used if a node contains more than one IEEE 802.2
   LLC protocol entity.





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RFC 2835            IP and ARP over HIPPI-6400 (GSN)            May 2000


   This memo assumes the use of "Logical Addressing" as described in
   Annex A.2 of HIPPI-6400-SC[2].

   The format of the address within its 48 bit HIPPI-6400-PH fields
   follows IEEE 802.1A canonical bit order and HIPPI-6400-PH bit and
   byte order:

    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  |      (not used for ULA)       |
   +---------------+---------------+---------------+---------------+

                     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.

4.3  Maximum Transmission Unit - MTU

   Maximum Transmission Unit (MTU) is defined as the maximum length of
   the IP packet, including IP header, but not including any overhead
   below IP, i.e., HIPPI-6400 MAC header and IEEE 802 LLC/SNAP header.
   Conventional LANs have MTU sizes determined by physical layer
   specification.  MTUs may be required simply because the chosen medium
   won't work with larger packets, or they may serve to limit the amount
   of time a node must wait for an opportunity to send a packet.

   HIPPI-6400-PH [1] limits packets to about 4 gigabytes (on VC 3) which
   imposes no practical limit for networking purposes. HIPPI-6400-PH VC
   1, which was chosen for IP and ARP traffic, limits messages to about
   128 Kbytes which is still larger than the HIPPI-800 MTU [17].

   The MTU for HIPPI-6400 LANs SHALL be 65280 (decimal) bytes.

   This value is backwards compatible with HIPPI-800. It allows the IP
   packet to fit in one 64K byte buffer with up to 256 bytes of
   overhead.  The IP v4 overhead is 24 bytes for HIPPI-6400 and 40 bytes
   for HIPPI-800.











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RFC 2835            IP and ARP over HIPPI-6400 (GSN)            May 2000


   For HIPPI-6400 the byte accounting is:

      HIPPI-6400-PH Header            16 bytes
      IEEE 802.2 LLC/SNAP Headers      8 bytes
      Maximum IP packet size (MTU) 65280 bytes
      Unused expansion room          232 bytes
                                   ------------
                        Total      65536 bytes (64K)

   In contrast, the HIPPI-800 accounting is:

      HIPPI-800-FP Header              8 bytes
      HIPPI-800-LE Header             24 bytes
      IEEE 802.2 LLC/SNAP Headers      8 bytes
      Unused expansion room          216 bytes
      Maximum IP packet size (MTU) 65280 bytes
                                   ------------
                        Total      65536 bytes (64K)

5. HIPPI Address Resolution Protocol - HARP

   Address resolution within the HIPPI-6400 LIS SHALL make use of the
   HIPPI Address Resolution Protocol (HARP) and the Inverse HIPPI
   Address Resolution Protocol (InHARP). HARP provides the same
   functionality as the Internet Address Resolution Protocol (ARP).

   HARP is based on ARP which is defined in RFC-826 [14] except the
   HIPPI-6400 specific packet format. Knowing the Internet address,
   conventional networks use ARP to discover another node's hardware
   address.  HARP presented in this section further specifies the
   combination of the original protocol definitions to form a coherent
   address resolution service that is independent of the hardware's
   broadcast capability.  InHARP is the same protocol as the original
   Inverse ARP (InARP) protocol presented in [5] except the HIPPI-6400
   specific packet format.  Knowing its hardware address, InARP is used
   to discover the other party's Internet address.

   This memo further REQUIRES the PIBES (see section 7) extension to the
   HARP protocol, guaranteeing broadcast service to upper layer
   protocols like IP.

   Internet addresses are assigned independent of ULAs.  Before using
   HARP, each node MUST know its IP and its HW addresses. The ULA is
   optional but is RECOMMENDED if interoperability with conventional
   networks is desired.






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RFC 2835            IP and ARP over HIPPI-6400 (GSN)            May 2000


   If all switches in the LIS support broadcast, then the source address
   in the reply will be the target's source address.  If all switches in
   the LIS do not support broadcast, then a HARP server MUST be used to
   provide the address resolution service, and the source address in the
   reply will be the HARP server's source address.

5.1 HARP Algorithm

   This section defines the behavior and requirements for HARP
   implementations on both broadcast and non-broadcast capable HIPPI-
   6400-SC networks. HARP creates a table in each port which maps remote
   ports' IP addresses to ULAs, so that when an application requests a
   connection to a remote port by its IP address, the remote ULA can be
   determined, a correct HIPPI-6400-PH header can be built, and a