rfc2067.txt

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Network Working Group                                         J. Renwick
Request for Comments: 2067                                 NetStar, Inc.
Category: Standards Track                                   January 1997
Obsoletes: 1374


                             IP over HIPPI

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   ANSI Standard X3.218-1993 (HIPPI-LE[3]) defines the encapsulation of
   IEEE 802.2 LLC PDUs and, by implication, IP on HIPPI.  ANSI X3.222-
   1993 (HIPPI-SC[4]) describes the operation of HIPPI physical
   switches.  The ANSI committee responsible for these standards chose
   to leave HIPPI networking issues largely outside the scope of their
   standards; this document describes the use of HIPPI switches as IP
   local area networks.

   This memo is a revision of RFC 1374, "IP and ARP on HIPPI", and is
   intended to replace it in the Standards Track.  RFC 1374 has been a
   Proposed Standard since November, 1992, with at least 10
   implementations of IP encapsulation and HIPPI switch discipline.  No
   major changes to it are required.  However, the ARP part of RFC 1374
   has not had sufficient implementation experience to be advanced to
   Draft Standard.  The present document contains all of RFC 1374 except
   for the description ARP, which has been moved into a separate
   document.

TABLE OF CONTENTS

   1  Introduction.............................................  2
   2  Scope....................................................  3
      2.1   Changes from RFC 1374..............................  3
      2.2   Terminology........................................  4
   3  Definitions..............................................  4
   4  Equipment................................................  5
   5  Protocol ................................................  7
      5.1   Packet Format......................................  7
      5.2   48 bit Universal LAN MAC addresses................. 11
      5.3   I-Field Format..................................... 12



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RFC 2067                     IP over HIPPI                  January 1997


      5.4   Rules For Connections.............................. 13
      5.5   MTU................................................ 15
   6  Camp-on ................................................. 16
   7  Path MTU Discovery....................................... 17
   8  Channel Data Rate Discovery.............................. 17
   9  Performance.............................................. 18
   10 Sharing the Switch....................................... 20
   11 References............................................... 21
   12 Security Considerations.................................. 21
   13 Author's Address......................................... 21
   14 Appendix A -- HIPPI Basics............................... 22
   15 Appendix B -- How to Build a Practical HIPPI LAN......... 27

1  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 bytes (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 "ftp.network.com"
   in the directory "hippi", and may be obtained via anonymous FTP.

   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.














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2  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
   may be interoperable on more complex networks as well, 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.

   Within the scope of this memo are:

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

      2.  I-Field contents

      3.  Rules for the use of connections.

   Outside of the scope are

      1.  Address Resolution (ARP)

      2.  Network configuration and management

      3.  Host internal optimizations

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

2.1  Changes from RFC 1374

   RFC 1374 described the use of ARP on HIPPI, but because of
   insufficient implementation experience, the description of ARP has
   been separated from IP encapsulation and moved to an Informational
   memo.  It may be returned to the standards track in the future if
   interest and implementations warrant it.










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   RFC 1374's specification of IP over HIPPI has been changed in this
   document.  Certain packet format options, permitted in RFC 1374, are
   no longer allowed:

           1.  Optional short burst first;

           2.  D1 fill bytes;

           3.  Nonzero D2 offset.

   That is, the header format is no longer variable and is required to
   be that which is recommended by RFC 1374.

   With these changes, it is possible to send packets which conform to
   the ANSI standards but not to this memo.  Because there are no RFC
   1374 implementations in use that used these options, we believe that
   all existing RFC 1374 implementations are compliant with the
   requirements of this memo, and there should be no interoperability
   problems associated with these changes.

2.2  Terminology

   In this document the use of the word SHALL in capital letters
   indicates mandatory points of compliance.

3  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 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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RFC 2067                     IP over HIPPI                  January 1997


   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.

4  Equipment

   A HIPPI network can be composed of nodes with HIPPI interfaces, HIPPI
   cables or serial links, HIPPI-SC switches, gateways to other
   networks.

   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.













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RFC 2067                     IP over HIPPI                  January 1997


   The following figure shows a sample HIPPI switch configuration.

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