rfc1374.txt

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Network Working Group                                         J. Renwick
Request for Comments: 1374                                  A. Nicholson
                                                     Cray Research, Inc.
                                                            October 1992
                          IP and ARP on HIPPI



Status of this Memo

   This RFC specifies an IAB standards track protocol for the Internet
   community, and requests discussion and suggestions for improvements.
   Please refer to the current edition of the "IAB Official Protocol
   Standards" for the standardization state and status of this protocol.
   Distribution of this memo is unlimited.

Abstract

   The ANSI X3T9.3 committee has drafted a proposal for the
   encapsulation of IEEE 802.2 LLC PDUs and, by implication, IP on
   HIPPI.  Another X3T9.3 draft describes the operation of HIPPI
   physical switches.  X3T9.3 chose to leave HIPPI networking issues
   largely outside the scope of their standards; this document discusses
   methods of using of ANSI standard HIPPI hardware and protocols in the
   context of the Internet, including the use of HIPPI switches as LANs
   and interoperation with other networks.  


Table of Contents

      Introduction                                                   2
      Scope                                                          2
      Definitions                                                    3
      Equipment                                                      4
      Protocol                                                       6

         Packet Format                                               6
         48 bit Universal LAN MAC addresses                         10
         I-Field Format                                             11
         Rules For Connections                                      13
         MTU                                                        15

      Camp-on                                                       16
      Address Resolution                                            16

         ARP and RARP Message Format                                17
         ARP Procedure                                              21
         ARP Implementation Methods                                 22



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RFC 1374                  IP and ARP on HIPPI               October 1992


         ARP Example                                                23
         Discovery of One's Own Switch Address                      25

      Path MTU Discovery                                            27
      Channel Data Rate Discovery                                   27
      Performance                                                   29
      Sharing the Switch                                            31
      Appendix A -- HIPPI Basics                                    31
      Appendix B -- How to Build a Practical HIPPI LAN              37
      References                                                    41
      Security Considerations                                       42
      Authors' Addresses                                            42

Introduction

   The ANSI High-Performance Parallel Interface (HIPPI) is a simplex
   data channel.  Configured in pairs, HIPPI can send and receive data
   simultaneously at nearly 800 megabits per second.  (HIPPI has an
   equally applicable 1600 megabit/second option.) Between 1987 and
   1991, the ANSI X3T9.3 HIPPI working group drafted four documents that
   bear on the use of HIPPI as a network interface.  They cover the
   physical and electrical specification (HIPPI-PH [1]), the framing of
   a stream of octets (HIPPI-FP [2]), encapsulation of IEEE 802.2 LLC
   (HIPPI-LE [3]), and the behavior of a standard physical layer switch
   (HIPPI-SC [4]).  HIPPI-LE also implies the encapsulation of Internet
   Protocol[5].  The reader should be familiar with the ANSI HIPPI
   documents, copies of which are archived at the site
   "nsco.network.com" in the directory "hippi," and may be obtained via
   anonymous FTP until they become published standards.

   HIPPI switches can be used to connect a variety of computers and
   peripheral equipment for many purposes, but the working group stopped
   short of describing their use as Local Area Networks.  This memo
   takes up where the working group left off, using the guiding
   principle that except for length and hardware header, Internet
   datagrams sent on HIPPI should be identical to the same datagrams
   sent on a conventional network, and that any datagram sent on a
   conventional 802 network[6] should be valid on HIPPI.

Scope

   This memo describes the HIPPI interface between a host and a
   crosspoint switch that complies with the HIPPI-SC draft standard.
   Issues that have no impact on host implementations are outside the
   scope of this memo.  Host implementations that comply with this memo
   are believed to be interoperable on a network composed of a single
   HIPPI-SC switch.  They are also interoperable on a simple point-to-
   point, two-way HIPPI connection with no switch between them.  They



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RFC 1374                  IP and ARP on HIPPI               October 1992


   may as well be interoperable on more complex networks, depending on
   the internals of the switches and how they are interconnected;
   however, these details are implementation dependent and outside the
   scope of this memo.  To the extent that a gateway acts as a host on a
   HIPPI-SC LAN, its behavior is within the scope of this memo.

   Within the scope of this memo are:

   1.  Packet format and header contents, including HIPPI-FP, HIPPI-LE,
       IEEE 802.2 LLC[7], SNAP and ARP

   2.  I-Field contents

   3.  HIPPI switch address resolution, including self discovery

   4.  Rules for the use of connections.

   Outside of the scope are

   1.  Vendor dependent solutions for multicast or third party ARP

   2.  Network configuration and management

   3.  Host internal optimizations

   4.  The interface between a host and an outboard protocol processor.

Definitions

   Conventional
      Used with respect to networks, this refers to Ethernet, FDDI and
      802 LAN types, as distinct from HIPPI-SC LANs.

   Destination
      The HIPPI implementation that receives data from a HIPPI Source.

   Node
      An entity consisting of one HIPPI Source/Destination pair that is
      connected by parallel or serial HIPPI to a HIPPI-SC switch and
      that transmits and receives ARP and IP datagrams.  A node may be
      an Internet host, bridge, router or gateway.  This memo uses the
      term node in place of the usual "host" to indicate that a host
      might be connected to the HIPPI LAN not directly, but through an
      external adaptor that does some of the protocol processing for the
      host.






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   Serial HIPPI
      An implementation of HIPPI in serial fashion on coaxial cable or
      optical fiber, informally standardized by implementor's agreement
      in the Spring of 1991.

   Switch Address
      A value used as the address of a node on a HIPPI-SC network.  It
      is transmitted in the I-field.  HIPPI-SC switches may map Switch
      Addresses to physical port numbers.

   Source
      The HIPPI implementation that generates data to send to a HIPPI
      Destination.

   Universal LAN Address (ULA)
      A 48 bit globally unique address, administered by the IEEE,
      assigned to each node on an Ethernet, FDDI, 802 network or HIPPI-
      SC LAN.

Equipment

   A HIPPI network can be composed of nodes with HIPPI interfaces, HIPPI
   cables or serial links, HIPPI-SC switches, gateways to other networks
   and, possibly, proprietary equipment that multicasts or responds to
   ARP requests on behalf of the real nodes.

   Each HIPPI interconnection between a node and a switch shall consist
   of a pair of HIPPI links, one in each direction.

   If a link between a node and the switch is capable of the 1600
   Megabit/second data rate option (i.e. Cable B installed for 64 bit
   wide operation) in either direction, the node's HIPPI-PH
   implementation shall also be capable of 32 bit operation (Cable B
   data suppressed) and shall be able to select or deselect the 1600Mb/s
   data rate option at the establishment of each new connection.

   The following figure shows a sample HIPPI switch configuration.














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RFC 1374                  IP and ARP on HIPPI               October 1992


                                                   +-----+
   |                                               | H 4 |
   |                                               +--+--+
   |                   +----+    +----+    +----+     |
   |                   | H1 |    | H2 |    | H3 |   +-++
   |   +--+            +-++-+    +-++-+    +-++-+   |PP|
   +---+H5|              ||        ||        ||     ++++
   |   +--+              ||        ||        ||      ||
   |                 +---++--------++--------++------++----+
   |                 |                                     |    +---+
   |   +----+        |              HIPPI-SC               +----+ARP|
   +---+ G1 +--------+                                     +----+   |
   |   |    +--------+               Switch                |    +---+
   |   +----+        |                                     |
   |                 +---++--------++--------++------++----+
   |   +--+              ||        ||        ||      ||
   +---+H6|              ||                         ++++
   |   +--+            +-++-+                       |PP|
   |                   |    |                       +-++
   |                   | G2 |                         |
   |                   |    |                      +--+--+
   |                   +--+-+                      | H 7 |
   |                      |                        +-----+
                          |
        -----+------------+-------+-----------+-------------+------
             |                    |           |             |
             |                    |           |             |
          +--+--+              +--+--+     +--+--+       +--+--+
          | H 8 |              | H 9 |     | H10 |       | H11 |
          +-----+              +-----+     +-----+       +-----+

   Legend:  ---+---+---+--  =  802 network, Ethernet or FDDI
                        ||  =  Paired HIPPI link
                         H  =  Host computer
                        PP  =  Outboard Protocol Processor
                         G  =  Gateway
                       ARP  =  ARP Agent

                    A possible HIPPI configuration

   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



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RFC 1374                  IP and ARP on HIPPI               October 1992


   complicated on blocking networks than on non-blocking ones.

   This memo ignores blocking issues, 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.

Protocol

   Packet Format