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rfc:rfc2834

Network Working Group J.-M. Pittet Request for Comments: 2834 Silicon Graphics Inc. Obsoletes: 1374 May 2000 Category: Standards Track

                ARP and IP Broadcast over HIPPI-800

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.

Copyright Notice

 Copyright (C) The Internet Society (2000).  All Rights Reserved.

Abstract

 This document specifies a method for resolving IP addresses to ANSI
 High-Performance Parallel Interface (HIPPI) hardware addresses and
 for emulating IP broadcast in a logical IP subnet (LIS) as a direct
 extension of HARP. This memo defines a HARP that will interoperate
 between HIPPI-800 and HIPPI-6400 (also known as Gigabyte System
 Network, GSN). This document (when combined with RFC-2067 "IP over
 HIPPI") obsoletes RFC-1374.

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . .   2
 2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
 3.  Definitions . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1 Global Concepts . . . . . . . . . . . . . . . . . . .   3
     3.2 Glossary  . . . . . . . . . . . . . . . . . . . . . .   3
 4.  IP Subnetwork Configuration . . . . . . . . . . . . . . .   5
     4.1 Background  . . . . . . . . . . . . . . . . . . . . .   5
     4.2 HIPPI LIS Requirements  . . . . . . . . . . . . . . .   6
 5.  HIPPI Address Resolution Protocol - HARP  . . . . . . . .   7
     5.1 HARP Algorithm  . . . . . . . . . . . . . . . . . . .   8
         5.1.1 Selecting the authoritative HARP service  . . .   8
         5.1.2 HARP registration phase . . . . . . . . . . . .   9
         5.1.3 HARP operational phase  . . . . . . . . . . . .  10
 5.2 HARP Client Operational Requirements  . . . . . . . . . .  11
     5.3 Receiving Unknown HARP Messages . . . . . . . . . . .  12
     5.4 HARP Server Operational Requirements  . . . . . . . .  12

Pittet Standards Track [Page 1] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

     5.5 HARP and Permanent ARP Table Entries  . . . . . . . .  14
     5.6 HARP Table Aging  . . . . . . . . . . . . . . . . . .  14
 6.  HARP Message Encoding . . . . . . . . . . . . . . . . . .  15
     6.1 HIPPI-LE Header of HARP Messages  . . . . . . . . . .  15
         6.1.1 IEEE 802.2 LLC  . . . . . . . . . . . . . . . .  16
         6.1.2 SNAP  . . . . . . . . . . . . . . . . . . . . .  16
         6.1.3 Diagram . . . . . . . . . . . . . . . . . . . .  17
     6.2 HIPPI Hardware Address Formats and Requirements . . .  18
         6.2.1 48-bit Universal LAN MAC Addresses  . . . . . .  18
     6.3 HARP and InHARP Message Formats . . . . . . . . . . .  19
         6.3.1 Example Message encodings . . . . . . . . . . .  22
         6.3.2 HARP_NAK message format . . . . . . . . . . . .  22
         6.3.3 Combined HIPPI-LE and HARP message addresses  .  22
 7.  Broadcast and Multicast . . . . . . . . . . . . . . . . .  23
     7.1 Protocol for an IP Broadcast Emulation Server - PIBES  23
     7.2 IP Broadcast Address  . . . . . . . . . . . . . . . .  24
     7.3 IP Multicast Address  . . . . . . . . . . . . . . . .  24
     7.4 A Note on Broadcast Emulation Performance . . . . . .  24
 8.  HARP for Scheduled Transfer Protocol  . . . . . . . . . .  25
 9.  Discovery of One's Own Switch Address . . . . . . . . . .  25
 10. Security Considerations . . . . . . . . . . . . . . . . .  26
 11. Open Issues . . . . . . . . . . . . . . . . . . . . . . .  26
 12. HARP Examples . . . . . . . . . . . . . . . . . . . . . .  26
     12.1 Registration Phase of Client Y on Non-broadcast HW .  27
     12.2 Registration Phase of Client Y on Broadcast Hardware  28
     12.3 Operational Phase (phase II) . . . . . . . . . . . .  28
          12.3.1 Standard successful HARP_Resolve example  . .  29
          12.3.2 Standard non-successful HARP_Resolve example   30
 13. References  . . . . . . . . . . . . . . . . . . . . . . .  31
 14. Acknowledgments . . . . . . . . . . . . . . . . . . . . .  32
 15. Changes from RFC-1374 . . . . . . . . . . . . . . . . . .  32
 16. Author's Address  . . . . . . . . . . . . . . . . . . . .  33
 17. Full Copyright Statement  . . . . . . . . . . . . . . . .  34

1. Introduction

 The ANSI High-Performance Parallel Interface (HIPPI) is a dual
 simplex data channel.   HIPPI can send and receive data
 simultaneously at 800 or 1600 megabits per second. Between 1987 and
 1997, the ANSI X3T11.1 HIPPI working group (now known as NCITS T11.1)
 Standardized five 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]), the
 behavior of a physical layer switch (HIPPI-SC [4]) and the physical-
 level and optical specification (HIPPI-Serial [5]).  HIPPI-LE also
 implies the encapsulation of Internet Protocol[5].  The reader should
 be familiar with the ANSI HIPPI documents. Approved ANSI NCITS

Pittet Standards Track [Page 2] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

 standards are available from ANSI (http://www.ansi.org). The working
 documents of the T11.1 working group may be obtained from the T11 web
 page (http://www.t11.org/).
 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.  RFC-2067 [15]
 describes the encapsulation of IP over HIPPI-800. This memo takes up
 where the working group and RFC-2067 [15] left off and defines
 address resolution and LIS IP broadcast emulation for HIPPI-800
 networks.
 While investigating possible solutions for HARP it became evident
 that IP broadcast could easily be emulated for both HIPPI-800 and
 HIPPI-6400 hardware types. This is useful since HIPPI switches are
 not required to implement broadcast but many standard networking
 protocols rely on broadcast.  This memo therefore further addresses
 the emulation of LIS IP broadcast as an extension of HARP.

2 Terminology

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in RFC-2119 [18].

3. Definitions

3.1 Global concepts used

 In the following discussion, the terms "requester" and "target" are
 used to identify the port initiating the address resolution request
 and the port whose address it wishes to discover, respectively.  If
 not all switches in the LIS support broadcast then there will be a
 HARP server providing the address resolution service and it will be
 the source of the reply. If on the other hand all switches support
 broadcast then the source address of a reply will be the target's
 target address.
 Values are decimal unless otherwise noted. Formatting follows IEEE
 802.1A canonical bit order and and HIPPI-FP bit and byte order.

3.2 Glossary

 Broadcast
 A distribution mode which transmits a message to all ports.
 Particularly also the port sending the message.

Pittet Standards Track [Page 3] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

 Classical/Conventional
 Both terms are used to refer to networks such as Ethernet, FDDI, and
 other 802 LAN types, as distinct from HIPPI-SC LANs.
 Destination
 The HIPPI port that receives data from a HIPPI Source.
 HARP
 HARP describes the whole set of HIPPI address resolution encodings
 and algorithms defined in this memo. HARP is a combination and
 adaptation of the Internet Address Resolution Protocol (ARP) RFC-826
 [13] and Inverse ARP (InARP) [7] (see section 5). HARP also describes
 the HIPPI specific version of ARP [10] (i.e. the protocol and the
 HIPPI specific encoding).
 HARP table
 Each host has a HARP table which contains the IP to hardware address
 mapping of IP members.
 HIPPI-Serial
 An implementation of HIPPI in serial fashion on coaxial cable or
 optical fiber. (see [5])
 HRAL
 The HARP Request Address List.  A list of ULAs to which HARP messages
 are sent when resolving names to addresses (see section 4.2).
 Hardware (HW) address
 The hardware address of a port consisting of an I-Field and an
 optional ULA (see section 6.2). Note: the term port as used in this
 document refers to a HIPPI port and is roughly equivalent to the term
 "interface" as commonly used in other IP documents.
 Host
 An entity, usually a computer system, that may have one or more HIPPI
 ports and which may serve as a client or a HARP server.

Pittet Standards Track [Page 4] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

 Port
 An entity consisting of one HIPPI Source/Destination dual simplex
 pair that is connected by parallel or serial HIPPI to a HIPPI-SC
 switch and that transmits and receives IP datagrams.
 PIBES
 The Protocol for Internet Broadcast Emulation Server (see section 7).
 Switch Address
 A value used as the address of a port on a HIPPI-SC network.  It is
 transmitted in the I-field.  HIPPI-SC switches map Switch Addresses
 to physical switch port numbers. The switch address is extended with
 a mode byte to form an I-Field (see [4] and 6.2.2)
 Source
 The HIPPI port that generates data to send to a HIPPI Destination.
 Universal LAN MAC Address (ULA)
 A 48-bit globally unique address, administered by the IEEE, assigned
 to each port on an Ethernet, FDDI, 802 network, or HIPPI-SC LAN.

4. IP Subnetwork Configuration

4.1 Background

 ARP (address resolution protocol) as defined in [12] was meant to
 work on the 'local' cable. This definition gives the ARP protocol a
 local logical IP subnet (LIS) scope. In the LIS scenario, each
 separate administrative entity configures its hosts and routers
 within the LIS. Each LIS operates and communicates independently of
 other LIS's on the same HIPPI network.
 HARP has LIS scope only and serves all ports in the LIS.
 Communication to ports located outside of the local LIS is usually
 provided via an IP router. This router is a HIPPI port attached to
 the HIPPI network that is configured as a member of one or more
 LIS's. This configuration MAY result in a number of disjoint LIS's
 operating over the same HIPPI network. Using this model, ports of
 different IP subnets SHOULD communicate via an intermediate IP router
 even though it may be possible to open a direct HIPPI connection
 between the two IP members over the HIPPI network. This is a
 consequence of using IP and choosing to have multiple LIS's on the
 same HIPPI fabric.

Pittet Standards Track [Page 5] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

 By default, the HARP method detailed in section 5 and the classical
 LIS routing model MUST be available to any IP member client in the
 LIS.

4.2 HIPPI LIS Requirements

 The requirement for IP members (hosts, routers) operating in a HIPPI
 LIS configuration is:
 o  All members of the LIS SHALL have the same IP network/subnet
    address and address mask [6].
 The following list identifies the set of HIPPI-specific parameters
 that MUST be implemented in each IP station connected to the HIPPI
 network:
 o  HIPPI Hardware Address:
    The HIPPI hardware address of an individual IP port MUST contain
    the port's Switch Address (see section 9). The address SHOULD also
    contain a non-zero ULA address. If there is no ULA then that field
    MUST be zero.
 o  HARP Request Address List (HRAL):
    The HRAL is an ordered list of two or more addresses identifying
    the address resolution service(s). All HARP clients MUST be
    configured identically, i.e. all ports MUST have the same
    addresses(es) in the HRAL.
    The HRAL MUST contain at least two HIPPI HW addresses identifying
    the individual HARP service(s) that have authoritative
    responsibility for resolving HARP requests of all IP members
    located within the LIS.
    By default the first address MUST be the reserved address for
    broadcast, i.e. the address for "IP traffic conventionally
    directed to the IEEE 802.1 broadcast address: 0xFE1" [4]. The ULA
    for this HARP service entry SHALL be FF:FF:FF:FF:FF:FF.
    It is REQUIRED that the second address be the address for
    "Messages pertaining to (the) ... address  resolution requests:
    0xFE0" [4]. The ULA for this HARP server entry is
    00:00:00:00:00:00.

Pittet Standards Track [Page 6] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

Therefore, the HRAL entries are sorted in the following order:

1st **  : broadcast address            (0x07000FE1 FF:FF:FF:FF:FF:FF),
2nd **  : official HARP server address (0x07000FE0 00:00:00:00:00:00),
3rd & on: any additional HARP server addresses will be sorted in
          decreasing order of the 12bit destination switch
          address portion of their I-Field (see section 6.2).
** REQUIRED
 Within the restrictions mentioned above and in Section 6.2.2, local
 administration choose address(es) for the additional HARP services
 which they will put into the HRAL.
 An example of such a list:
    1st entry: 0x07000FE1 FF:FF:FF:FF:FF:FF
    2nd entry: 0x07000FE0 00:00:00:00:00:00
    3rd entry: 0x07000001 <Alternate-HARP-server-ula>
    ...
 Manual configuration of the addresses and address lists presented in
 this section is implementation dependent and beyond the scope of this
 memo.

5. HIPPI Address Resolution Protocol - HARP

 Address resolution within the HIPPI 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 [13]. Knowing the Internet address,
 conventional networks use ARP to discover another port'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 based on the original Inverse ARP (InARP) protocol
 presented in [7].  Knowing its hardware address, InARP is used to
 discover the other party's Internet address.
 This memo further REQUIRES the PIBES (see section 7 below) extension
 to the HARP protocol, guaranteeing broadcast service to upper layer
 protocols like IP.
 Internet addresses are assigned independent of ULAs and switch
 addresses.  Before using HARP, each port MUST know its IP and its
 hardware addresses. The ULA is optional but is RECOMMENDED if
 bridging to conventional networks is desired.

Pittet Standards Track [Page 7] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

5.1 HARP Algorithm

 This section defines the behavior and requirements for HARP
 implementations on both broadcast and non-broadcast capable HIPPI-SC
 networks. HARP creates a table in each port which maps the IP address
 of each port to a hardware address, so that when an application
 requests a connection to a remote port by its IP address, the
 hardware address can be determined, a correct HIPPI-LE header can be
 built, and a connection to the port can be established using the
 correct Switch Address in the I-field.
 HARP is a two phase protocol. The first phase is the registration
 phase and the second phase is the operational phase. In the
 registration phase the port detects if it is connected to broadcast
 hardware or not.  The InHARP protocol is used in the registration
 phase.  In case of non-broadcast capable hardware, the InHARP
 Protocol will register and establish a table entry with the server.
 The operational phase works much like conventional ARP with the
 exception of the message format.

5.1.1 Selecting the authoritative HARP service

 Within the HIPPI LIS, there SHALL be an authoritative HARP service.
 At each point in time there is only one authoritative HARP service.
 To select the authoritative HARP service, each port needs to
 determine if it is connected to a broadcast network.
 The port SHALL send an InHARP_REQUEST to the first address in its
 HRAL (0x07000FE1 FF:FF:FF:FF:FF:FF). If the port sees its own
 InHARP_REQUEST, then it is connected to a broadcast capable network.
 In this case, the rest of the HRAL is ignored and the authoritative
 HARP service is the broadcast entry.
 If the port is connected to a non-broadcast capable network, then the
 port SHALL send the InHARP_REQUEST to all of the remaining entries in
 the HRAL. Every address which sends an InHARP_REPLY is considered to
 be a responsive HARP server. The authoritative HARP service SHALL be
 the HARP server which appears first in the HRAL.
 The sequence of the HRAL is only important for deciding which address
 will be the authoritative one. On a non-broadcast network, the port
 is REQUIRED to keep "registered" with all HARP server addresses in
 the HRAL (NOTE: not the broadcast address since it is not a HARP
 server address). If for instance the authoritative HARP service is
 non-responsive,  then the port will consider the next address in the
 HRAL as a candidate for the authoritative address and send an
 InHARP_REQUEST.

Pittet Standards Track [Page 8] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

 The authoritative HARP server SHOULD be considered non-responsive
 when it has failed to reply to: (1) one or more registration requests
 by the client (see section 5.1.2 and 5.2), (2) any two HARP_REQUESTs
 in the last 120 seconds or (3) if an external agent has detected
 failure of the authoritative HARP server. The details of such an
 external agent and its interaction with the HARP client are beyond
 the scope of this document. Should an authoritative HARP server
 become non-responsive, then the registration process SHOULD be
 restarted. Alternative methods for choosing an authoritative HARP
 service are not prohibited.

5.1.2 HARP registration phase

 HARP clients SHALL initiate the registration phase by sending an
 InHARP_REQUEST message using the addresses in the HRAL in order. The
 client SHALL terminate the registration phase and transition into the
 operational phase, either when it receives its own InHARP_REQUEST or
 when it receives an InHARP_REPLY from at least one of the HARP
 servers and when it has determined the authoritative HARP service as
 described in section 5.1.1.
 When ports are initiated they send an InHARP_REQUEST to the
 authoritative address as described in section 5.1.2. The first
 address to be tried will be the broadcast address "0x07000FE1
 FF:FF:FF:FF:FF:FF". There are two outcomes:
 1. The port sees its own InHARP_REQUEST: then the port is connected
    to a broadcast capable network. The first address becomes and
    remains the authoritative address for the HARP service.
 2. The port does not receive its InHARP_REQUEST: then the port is
    connected to a non-broadcast capable network.
 In the second case, the port SHALL choose the next address in the
 HRAL as a candidate for a authoritative address and send an
 InHARP_REQUEST to that address: (0x07000FE0 00:00:00:00:00:00).
 o  If the port receives its own message, then the port itself is the
    HARP server and the port is REQUIRED to provide broadcast services
    using the PIBES (see section 7).
 o  If the port receives an InHARP_REPLY, then it is a HARP client and
    not a HARP server.
 In both cases, the current candidate address becomes the
 authoritative HARP service address.

Pittet Standards Track [Page 9] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

 If the client determines it is connected to a non-broadcast capable
 network then the client SHALL continue to retry each non-broadcast
 HARP server address in the HRAL at least once every 5 seconds until
 one of these two termination criteria are met for each address.
 InHARP is an application of the InARP protocol for a purpose not
 originally intended.  The purpose is to accomplish registration of
 port IP address mappings with a HARP server if one exists or detect
 hardware broadcast capability.
 If the HIPPI-SC LAN supports broadcast, then the client will see its
 own InHARP_REQUEST message and SHALL complete the registration phase.
 The client SHOULD further note that it is connected to a broadcast
 capable network and use this information for aging the HARP server
 entry and for IP broadcast emulation as specified in sections 5.4 and
 5.6 respectively.
 If the client doesn't see its own InHARP_REQUEST, then it SHALL await
 an InHARP_REPLY before completing the registration phase. This will
 also provide the client with the protocol address by which the HARP
 server is addressable.  This will be the case when the client happens
 to be  connected to a non-broadcast capable HIPPI-SC network.

5.1.3 HARP operational phase

 Once a HARP client has completed its registration phase it enters the
 operational phase. In this phase of the protocol, the HARP client
 SHALL gain and refresh its own HARP table which contains the IP to HW
 address mapping of IP members by sending HARP_REQUESTS to the
 authoritative address in the HRAL and receiving HARP_REPLYs. The
 client is fully operational during the operational phase.
 In the operational phase, the client's behavior for requesting HARP
 resolution is the same for broadcast or non-broadcast networks.
 The target of an address resolution request updates its address
 mapping tables with any new information it can find in the request.
 If it is the target port it SHALL formulate and send a reply message.
 A port is the target of an address resolution request if at least ONE
 of the following statements is true of the request:
 1. The port's IP address is in the target protocol address field
    (ar$tpa) of the HARP message.
 2. The port's ULA (if non-zero), is in the ULA part of the Target
    Hardware Address field (ar$tha) of the message.

Pittet Standards Track [Page 10] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

 3. The port's switch address is in the Target Switch Address field of
    Target Hardware Address field (ar$tha) of the message (see section
    6.2.2).
 4. The port is a HARP server.
 NOTE: It is RECOMMENDED that all HARP servers run on a ports which
 each have a non-zero ULA.

5.2 HARP Client Operational Requirements

 The HARP client is responsible for contacting the HARP server(s) to
 have its own HARP information registered and to gain and refresh its
 own HARP entry/information about other IP members. This means, as
 noted above, that HARP clients MUST be configured with the hardware
 address of the HARP server(s) in the HRAL.
 HARP clients MUST:
 1. When an interface is enabled (e.g. "ifconfig <interface> up" with
    an IP address) or assigned the first or an additional IP address
    (i.e. an IP alias), the client SHALL initiate the registration
    phase.
 2. In the operational phase the client MUST respond to HARP_REQUEST
    and InHARP_REQUEST messages if it is the target port.  If an
    interface has multiple IP addresses (e.g., IP aliases) then the
    client MUST cycle through all the IP addresses and generate an
    InHARP_REPLY for each such address. In that case an InHARP_REQUEST
    will have multiple replies. (Refer to Section 7, "Protocol
    Operation" in RFC-1293  [7].)
 3. React to address resolution reply messages appropriately to build
    or refresh its own client HARP table entries. All solicited and
    unsolicited HARP_REPLYs from the authoritative HARP server SHALL
    be used to update and refresh its own client HARP table entries.
    Explanation: This allows the HARP server to update the clients
    when one of server's mappings change, similar to what is
    accomplished on Ethernet with gratuitous ARP.
 4. Generate and transmit InHARP_REQUEST messages as needed  and
    process InHARP_REPLY messages appropriately (see section 5.1.2 and
    5.6). All InHARP_REPLY messages SHALL be used by the client to
    build or refresh its HARP table entries.  (Refer to Section 7,
    "Protocol Operation" in [7].)

Pittet Standards Track [Page 11] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

 If the registration phase showed that the hardware does not support
 broadcast, then the client MUST refresh its own entry for the HARP
 server, created during the registration phase, at least once every 15
 minutes. This can be accomplished either through the exchange of a
 HARP request/reply with the HARP server or by repeating step 1. To
 decrease the redundant network traffic, this timeout SHOULD be reset
 after each HARP_REQUEST/HARP_REPLY exchange.
 Explanation: The HARP_REQUEST shows the HARP server that the client
 is still alive. Receiving a HARP_REPLY indicates to the client that
 the server must have seen the HARP_REQUEST.
 If the registration phase shows that the underlying network supports
 broadcast, then periodic InHARP_REQUEST/InHARP_REPLY operations of
 step 4 are NOT REQUIRED.

5.3 Receiving Unknown HARP Messages

 If a HARP client receives a HARP message with an operation code
 (ar$op) that it does not support, it MUST gracefully discard the
 message and continue normal operation.  A HARP client is NOT REQUIRED
 to return any message to the sender of the undefined message.

5.4 HARP Server Operational Requirements

 A HARP server MUST accept HIPPI connections from other HIPPI ports.
 The HARP server expects an InHARP_REQUEST as the first message from
 the client. A server examines the IP source address, the hardware
 source address of the InHARP_REQUEST and adds or updates its HARP
 table entry <IP address(es), switch address, ULA>  as well as the
 time stamp.
 A HARP server SHALL reply to HARP_REQUESTs and InHARP_REQUESTs based
 on the information which it has in its HARP table.  The HARP server
 SHALL reply with a HARP_REPLY or a InHARP_REPLY, if it has the
 requested information in its tables; otherwise it SHALL reply with a
 HARP_NAK. The HARP server replies SHALL contain the hardware type and
 corresponding format of the request (see also section 6).
 The following table shows all possible source address combinations on
 an incoming message and the actions to be taken. "linked" indicates
 that an existing "IP entry" is linked to a "hardware entry". It is
 possible to have an existing "IP entry" and to have an existing
 "hardware entry" but neither is linked to the other.

Pittet Standards Track [Page 12] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

    +---+----------+----------+------------+---------------------+
    | # | IP entry | HW entry |  misc      |      Action         |
    +---+----------+----------+------------+---------------------+
    | 1 |  exists  |  exists  |     linked | *                   |
    | 2 |  exists  |  exists  | not linked | *, a, b,       e, f |
    | 3 |  exists  |    new   | not linked | *, a, b,    d, e, f |
    | 4 |   new    |  exists  | not linked | *,       c,    e, f |
    | 5 |   new    |    new   | not linked | *,       c, d, e, f |
    +---+----------+----------+------------+---------------------+
    Actions:
    *: update timeout value
    a: break the existing IP -> hardware (HW) - old link
    b: delete HW(old) -> IP link and decrement HW(old) refcount, if
       refcount = 0, delete HW(old)
    c: create new IP entry
    d: create new HW entry
    e: add new IP -> HW link to IP entry
    f: add new HW -> IP link to HW entry
 Examples of when this could happen (Numbers match lines in above
 table):
 1: supplemental message
    Just update timer.
 2: move an IP alias to an existing interface
    If the IP source address of the InHARP_REQUEST duplicates a table
    entry IP address (e.g. IPa <-> HWa) and the InHARP_REQUEST
    hardware source address matches a hardware address entry (e.g. HWb
    <-> IPb), but they are not linked together, then:
    -  HWa entry needs to have its reference to the current IPa
       address removed.
    -  HWb needs to have a new reference to IPa added
    -  IPa needs to be linked to HWb
 3: move IP address to a new interface
    If the InHARP_REQUEST requester's IP source address duplicates a
    table entry IP address and the InHARP_REQUEST hardware source
    address does not match the table entry hardware address, then a
    new HW entry SHALL be created. The requestor's IP address SHALL be
    moved from the original HW entry to the new one (see above).

Pittet Standards Track [Page 13] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

 4: add  IP alias to table
    If the InHARP_REQUEST requester's hardware source address
    duplicates a hardware source address entry, but there is no IP
    entry matching the received IP address, then the IP address SHALL
    be added to the hardware entries previous IP address(es). (E.g.
    adding an IP alias).
 5: fresh entry, add it
    Standard case, create both entries and link them.
 A server MUST update the HARP table entry's timeout for each
 HARP_REQUEST. Explanation: if the client is sending HARP requests to
 the server, then the server SHOULD note that the client is still
 "alive" by updating the timeout on the client's HARP table entry.
 A HARP server SHOULD use the PIBES (see section 7) to send out
 HARP_REPLYs to all hardware addresses in its table when the HARP
 server table changes mappings. This feature decreases the time of
 stale entries in the clients.
 If there are multiple addresses in the HRAL, then a server needs to
 act as a client to the other servers.

5.5 HARP and Permanent ARP Table Entries

 An IP station MUST have a mechanism (e.g. manual configuration) for
 determining what permanent entries it has. The details of the
 mechanism are beyond the scope of this memo.  The permanent entries
 allow interoperability with legacy HIPPI adapters which do not yet
 implement dynamic HARP and use a table-based static ARP. Permanent
 entries are not aged.
 The HARP server SHOULD use the static entries to resolve incoming
 HARP_REQUESTs from the clients. This feature eliminates the need for
 maintaining a static HARP table on the client ports.

5.6 HARP Table Aging

 HARP table aging MUST be supported since IP addresses, especially IP
 aliases and also interfaces (with their ULA), are likely to move.
 When so doing the mapping in the clients own HARP table/cache becomes
 invalid and stale.
 o  When a client's HARP table entry ages beyond 15 minutes, a HARP
    client MUST invalidate the table entry.

Pittet Standards Track [Page 14] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

 o  When a server's HARP table entry ages beyond 20 minutes, the HARP
    server MUST delete the table entry.
 NOTE: the client SHOULD revalidate a HARP table entry before it ages,
 thus restarting the aging time when the table entry is successfully
 revalidated.  The client MAY continue sending traffic to the port
 referred to by this entry while revalidation is in progress, as long
 as the table entry has not aged. The client MUST revalidate an aged
 entry prior to transmitting any non-address-resolution traffic to the
 port referred to by this entry.
 The client revalidates the entry by querying the HARP server with a
 HARP_REQUEST.  If a valid reply is received (e.g. HARP_REPLY), the
 entry is updated.  If the address resolution service cannot resolve
 the entry (e.g. HARP_NAK, "host not found"), the associated table
 entry is removed.  If the address resolution service is not available
 (i.e. "server failure") the client MUST attempt to revalidate the
 entry by transmitting an InHARP_REQUEST to the hardware address of
 the entry in question and updating the  entry on receipt of an
 InHARP_REPLY. If the InHARP_REQUEST attempt fails to return an
 InHARP_REPLY, the associated table entry is removed.

6. HARP Message Encoding

 The HARP Message is encapsulated over HIPPI-FP and HIPPI-LE headers.
 The HARP FP header values are to be set as defined in RFC-2067 "IP
 over HIPPI" [15]. The following sections detail the HIPPI-LE field
 contents and HARP message structure and contents. In a broadcast
 capable network the client MAY also support Type 1 and 6, Ethernet
 and IEEE 802 ARP packet formats.

6.1 HIPPI-LE Header of HARP Messages

 The HIPPI message format for Internet datagrams shall conform to the
 HIPPI-FP [2] and HIPPI-LE [3] standards.  The length of a HIPPI
 message, including trailing fill, shall be a multiple of eight bytes
 as required by HIPPI-LE.  The HIPPI-LE header fields of HARP and
 InHARP requests and replies SHALL be:
 FC (3 bits) SHALL contain zero.
 Double-wide SHOULD be set according to HIPPI-LE [3]. This memo does
 NOT address the implications on HARP when this bit is set to 1
 indicating the possibility of a port being able to accept 64-bit
 HIPPI connections.

Pittet Standards Track [Page 15] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

 Message_Type SHALL contain 0 to indicate a data message. HARP
 messages are identified using the Ethertype and the message type in
 the ar$op field of the HARP message.
 Destination_Switch_Address, SHALL be the Switch Address of the
 destination port.
 Destination_IEEE_Address SHALL be the ULA of the destination port, if
 known, otherwise zero.
 Destination_Address_Type SHALL be 2, a 12-bit logical address.  The
 behavior with type = 1, source routing, is NOT defined in this
 specification.
 Source_Switch_Address in requests SHALL be the sender's Switch
 Address.
 Source_IEEE_Address SHALL be the sender's ULA if known, otherwise
 zero.
 Source_Address_Type SHALL be 2, a 12-bit logical address. The
 behavior with type = 1, source routing, is NOT defined in this
 specification.

6.1.1 IEEE 802.2 LLC

 The IEEE 802.2 LLC Header SHALL begin in the first byte of the
 HIPPI-FP D2_Area.
 The LLC value for SSAP-DSAP-CTL SHALL be 0xAA-AA-03 (3 bytes)
 indicating the presence of a SNAP header.

6.1.2 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 [16]:
 InHARP = InARP = HARP = ARP = 2054 = 0x0806.
 The total size of the LLC/SNAP header is fixed at 8-bytes.

Pittet Standards Track [Page 16] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

6.1.3 HIPPI-LE header Diagram

                 HIPPI-LE header for HARP/InHARP PDUs:
    31    28        23  21          15        10     7         2   0
    +-----+---------+-+-+-----------+---------+-----+---------+-----+
  0 | 04 = IP ULP   |1|0|         000         |      03       |  0  |
    +---------------+-+-+---------------------+---------------+-----+
  1 |                            n + 8                              |
    +-----+-+-------+-----------------------+-----------------------+
  2 |[LA] |W|M_Type |          000          |  Dest. Switch Addr    |
    +-----+-+-------+-----------------------+-----------------------+
  3 | D_A_T | S_A_T |          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 |Message byte 0 |Message byte 1 |Message byte 2 | . . .         |
    +---------------+---------------+---------------+---            |
    |                            .  .  .                            |
    +   ------------+---------------+---------------+---------------+
    |         . . . |   byte (n-2)  |   byte (n-1)  |     FILL      |
    +---------------+---------------+---------------+---------------+
 N-1|      FILL     |     FILL      |     FILL      |     FILL      |
    +---------------+---------------+---------------+---------------+
                          HIPPI Message 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           (HARP message)
    (n+8) is the nb of bytes in the  HARP message, incl. LLC/SNAP.
    +====+ denotes the boundary between D1_Area and D2_Area.
    [LA] fields are zero unless used otherwise locally.
    Abbreviations:
     "W"      = Double_Wide field        SHALL be 0
     "M_Type" = Message_Type field       SHALL be set according to
                                                  HIPPI-LE
     "D_A_T"  = Destination_Address_Type SHALL be 2

Pittet Standards Track [Page 17] 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:

Pittet Standards Track [Page 18] 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

Pittet Standards Track [Page 19] 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.

Pittet Standards Track [Page 20] 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

Pittet Standards Track [Page 21] 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)

Pittet Standards Track [Page 22] 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)
 MUST emulate broadcast through an IP broadcast emulation server.
 A HIPPI IP broadcast server (PIBES) is an extension to the HARP
 server and only makes sense when the LIS does not inherently support
 broadcast. The PIBES allows common upper layer networking protocols
 (RIP, TCP, UDP, etc.) to access IP LIS broadcast.

7.1 Protocol for an IP Broadcast Emulation Server - PIBES

 To emulate broadcast within an LIS, a PIBES SHALL use the currently
 valid HARP table of the HARP server as a list of addresses called the
 target list. The broadcast server SHALL validate that all incoming
 messages have a source address which corresponds to an address in the
 target list. Only messages addressed to the IP LIS broadcast
 addresses, multicast address or 255.255.255.255 are considered valid
 messages for broadcasting. Invalid messages MUST be dropped.  All
 valid incoming messages shall be forwarded to all addresses in the
 target list.

Pittet Standards Track [Page 23] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

 It is RECOMMENDED that the broadcast server run on the same port as
 the HARP server since this memo does not define the protocol for
 exchanging the valid HARP table. The default address to use for the
 broadcast address is the operational HARP server address.

7.2 IP Broadcast Address

 This memo only defines IP broadcast. It is independent of the
 underlying hardware addressing and broadcast capabilities. Any port
 can differentiate between IP traffic directed to itself and a
 broadcast message sent to it by looking at the IP address. All IP
 broadcast messages SHALL use the IP LIS broadcast address or.
 It is RECOMMENDED that the PIBES run on the same port as the HARP
 server. In that case, the PIBES SHALL use the same address as the
 HARP server.

7.3 IP Multicast Address

 HIPPI does not directly support multicast address, therefore there
 are no mappings available from IP multicast addresses to HIPPI
 multicast services.  Current IP multicast implementations (i.e. MBONE
 and IP tunneling, see [9]) will continue to operate over HIPPI-based
 logical IP subnets if all IP multicast packets are sent using the
 same algorithm as if the packet were being sent to 255.255.255.255.

7.4 A Note on Broadcast Emulation Performance

 It is obvious that a broadcast emulation service (as defined in
 section 7.1) has an inherent performance limit. In an LIS with n
 ports, the upper bound on the bandwidth that such a service can
 broadcast is:
                        (total bandwidth)/(n+1)
 since each message must first enter the broadcast server, accounting
 for the additional 1, and then be sent to all n ports. The broadcast
 server could forward the message destined to the port on which it
 runs internally, thus reducing (n+1) to (n) in a first optimization.
 This service is adequate for the standard networking protocols such
 as RIP, OSPF, NIS, etc. since they usually use a small fraction of
 the network bandwidth for broadcast. For these purposes, the
 broadcast emulation server as defined in this memo allows the HIPPI
 network to look similar to an Ethernet network to the higher layers.
 It is further obvious that such an emulation cannot be used to
 broadcast high bandwidth traffic. For such a solution, hardware
 support for true broadcast is required.

Pittet Standards Track [Page 24] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

8 HARP for Scheduled Transfer Protocol[17]

 This RFC also applies for resolving addresses used with Scheduled
 Transfer (STP) over  HIPPI-800 instead of IP. This RFC's message
 types and algorithms can  be used for STP (since STP uses Internet
 Addresses) as long as there is also an IP over HIPPI implementation
 on all of the ports.

9 Discovery of One's Own Switch Address

 This HARP specification assumes that each port has prior knowledge of
 its own hardware address.  This address may be manually configured,
 by means outside the scope of this memo or a port may discover its
 own logical address through the algorithm described below.
 Ports are NOT REQUIRED to implement this switch address discovery
 protocol but are encouraged to do so since it reduces the
 administrative overhead.  The algorithm presented in this section is
 based on John Renwick's work as detailed in RFC-1374 [14]. The
 concept of the discovery process is to scan all possible switch
 addresses. The messages that are received will be the ones containing
 one of our switch addresses.
 If a port implements this algorithm it SHALL form a HIPPI-LE message
 as defined in HIPPI-LE: containing an Self_Address_Resolution_Request
 (see [3]) PDU Type, a Source_IEEE_Address and
 Destination_IEEE_Address (set to the correct ULA for the sender), and
 the Source_Switch_Address and Destination_Switch_Address.
 This self address resolution message uses the same HIPPI-LE message
 format as described in HIPPI-SC and HIPPI-LE: the Self Address
 Resolution Request PDU and Self Address Resolution Response PDU type
 codes and no piggybacked ULP data.  The HIPPI-LE header contents for
 the request are:
    HIPPI-LE Message_Type is            = 3, Self Addr. Resolution Request
    HIPPI-LE Destination_Address_Type   = 0 (undefined)
    HIPPI-LE Destination_Switch_Address = X (X element scan range)
    HIPPI-LE Source_Address_Type        = 0 (undefined)
    HIPPI-LE Source_Switch_Address      = 0 (unknown)
    HIPPI-LE Destination_IEEE_Address   = 0
    HIPPI-LE Source_IEEE_Address        = my ULA
 There is no D2 data; the message contains only the HIPPI-FP header
 and D1_Area with the HIPPI-LE header.

Pittet Standards Track [Page 25] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

 Ports SHALL start the scan with a configurable logical address
 (default 0x000) and increment the value for by one for each
 subsequent try. The port SHALL continue until it sees its own self
 address resolution request or it has reached the end, which may be
 another configurable value (default 0xFFF). It is RECOMMENDED that
 the range of addresses to scan be configurable since some networks
 have equipment that does not gracefully handle HIPPI-LE messages.
 After a port sends the[se] request[s], two positive outcomes are
 possible:
 o  the port receives its own request(s), and obtains one of its own
    Switch Address, or
 o  the port receives an AR_S_Response with the
    Destination_Switch_Address filled in.

10 Security Considerations

 HARP messages are not authenticated which is a potentially flaw that
 could allow corrupt information to be introduced into the server
 system.
 There are other known security issues relating to port impersonation
 via the address resolution protocols used in the Internet [8].  No
 special security mechanisms have been added to the address resolution
 mechanism defined here for use with networks using HARP.
 Not all of the security issues relating to ARP over HIPPI are clearly
 understood at this time. However, given the security hole ARP allows,
 other concerns are probably minor.

11 Open Issues

 Synchronization and coordination of multiple HARP servers and
 multiple broadcast servers are left for further study.

12 HARP Examples

 Assume a HIPPI-SC switch is installed with three connected ports: x,
 y, and a.  Each port has a unique hardware address that consists of
 Switch Address (e.g. SWx, SWy, SWa) and unique ULA (ULAx, ULAy and
 ULAa, respectively). There is a HARP server connected to a switch
 port that is mapped to the address HWa (SWa, ULAa), this address is
 the authoritative HIPPI hardware address in the HRAL (HARP Request
 Address List).

Pittet Standards Track [Page 26] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

 The HARP server's table is empty. Ports X and Y each know their own
 hardware address.  Eventually they want to talk to each other; each
 knows the other's IP address (from the port database) but neither
 knows the other's ULA or Switch Address. Both ports X and Y have
 their interfaces configured DOWN.
 NOTE: The LLC, SNAP, Ethertype, HIPPI-LE Message Type, ar$hrd,
 ar$pro, ar$pln fields are left out from the examples below since they
 are constant. Likewise, ar$rhl = ar$thl = 9 are omitted since these
 are all HIPPI-800 examples.

12.1 Registration Phase of Client Y on Non-broadcast Hardware

 Port Y starts: its HARP table entry state for the server: PENDING
 1. Port Y initiates its interface and sends an InHARP_REQUEST to HWa
    after starting a table entry for HWa.
    HIPPI-LE Destination_Switch_Address = SWa
    HIPPI-LE Source_Switch_Address      = SWy
    HIPPI-LE Destination_IEEE_Address   = ULAa
    HIPPI-LE Source_IEEE_Address        = ULAy
    HARP ar$op                          = 8 (InHARP_REQUEST)
    HARP ar$rpa                         = IPy
    HARP ar$tpa                         = 0 **
    HARP ar$rha                         = SWy ULAy
    HARP ar$tha                         = SWa ULAa
    ** is what we would like to find out
 2. HARP server receives Y's InHARP_REQUEST, it examines the source
    addresses and scans its tables for a match. Since this is the
    first time Y connects to this server there is no entry and one
    will be created and time stamped with the information from the
    InHARP_REQUEST. The HARP server will then send a InHARP_REPLY
    including its IP address.
    HIPPI-LE Destination_Switch_Address = SWy
    HIPPI-LE Source_Switch_Address      = SWa
    HIPPI-LE Destination_IEEE_Address   = ULAy
    HIPPI-LE Source_IEEE_Address        = ULAa
    HARP ar$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

Pittet Standards Track [Page 27] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

 3. Port Y examines the incoming InHARP_REPLY, completes its table
    entry for the HARP server. The client's HARP table entry for the
    server now passes into the VALID state and is usable for regular
    HARP traffic. Receiving this reply ensures that the HARP server
    has properly registered the client.

12.2 Registration Phase of Client Y on Broadcast Capable Hardware

 If there is a broadcast capable network then the authoritative
 address in the HRAL would be mapped to the broadcast address, HWb =
 SWb, ULAb (likely 0xFE1 and FF:FF:FF:FF:FF:FF).
 Port Y starts: its HARP table entry state for HWa: PENDING
 1. Port Y initiates its interface and sends an InHARP_REQUEST to HWa,
    in this example the broadcast address, after starting a table
    entry.
    HIPPI-LE Destination_Switch_Address = SWb
    HIPPI-LE Source_Switch_Address      = SWy
    HIPPI-LE Destination_IEEE_Address   = ULAb
    HIPPI-LE Source_IEEE_Address        = ULAy
    HARP ar$op                          = 8 (InHARP_REQUEST)
    HARP ar$rpa                         = IPy
    HARP ar$tpa                         = 0 **
    HARP ar$rha                         = SWy ULAy
    HARP ar$tha                         = SWb ULAb
    ** is what we would like to find out
 2. Since the network is a broadcast network, client Y will receive a
    copy of its InHARP_REQUEST. Client Y examines the source
    addresses.  Since they are the same as what Y filled in the
    InHARP_REQUEST, Y can deduce that it is connected to a broadcast
    medium.  Port Y completes its table entry for HWa. This entry will
    not timeout since it is considered unlikely for a particular
    underlying hardware type to change between broadcast and non-
    broadcast; therefore this mapping will never change.

12.3 Operational Phase (phase II)

 The Operational Phase of the HARP protocol as specified in this memo
 is the same for both broadcast and non-broadcast capable HIPPI
 hardware. The authoritative address in the HRAL for this example will
 be HWa: <SWa, ULAa> and IPs for simplicity reasons.

Pittet Standards Track [Page 28] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

12.3.1 Standard successful HARP_Resolve example

 Assume the same process (steps 1-3 of section 10.1) happened for port
 X. Then the state of X and Y's tables is: the HARP server table entry
 is in the VALID state. So lets look at the message traffic when X
 tries to send a message to Y. Since X doesn't have an entry for Y,
 1. Port X connects to the authoritative address of the HRAL and sends
    a HARP_REQUEST for Y's hardware address:
    HIPPI-LE Destination_Switch_Address = SWa
    HIPPI-LE Source_Switch_Address      = SWx
    HIPPI-LE Destination_IEEE_Address   = ULAa
    HIPPI-LE Source_IEEE_Address        = ULAx
    HARP ar$op                          = 1  (HARP_REQUEST)
    HARP ar$rpa                         = IPx
    HARP ar$tpa                         = IPy
    HARP ar$rha                         = SWx ULAx
    HARP ar$tha                         = 0 **
    ** is what we would like to find out
 2. The HARP server receives the HARP request and updates its entry
    for X if necessary. It then generates a HARP_REPLY with Y's
    hardware address information.
    HIPPI-LE Destination_Switch_Address = SWx
    HIPPI-LE Source_Switch_Address      = SWa
    HIPPI-LE Destination_IEEE_Address   = ULAx
    HIPPI-LE Source_IEEE_Address        = ULAa
    HARP ar$op                          = 2  (HARP_Reply)
    HARP ar$rpa                         = IPy
    HARP ar$tpa                         = IPx
    HARP ar$rha                         = SWy ULAy *
    HARP ar$tha                         = SWx ULAx
    * answer we were looking for
 3. Port X connects to port Y and transmits an IP message with the
    following information in the HIPPI-LE header:
    HIPPI-LE Destination_Switch_Address = SWy
    HIPPI-LE Source_Switch_Address      = SWx
    HIPPI-LE Destination_IEEE_Address   = ULAy
    HIPPI-LE Source_IEEE_Address        = ULAx
 If there had been a broadcast capable HIPPI network, the target ports
 would themselves have received the HARP_REQUEST of step 2 above and
 responded to them in the same way the HARP server did.

Pittet Standards Track [Page 29] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

12.3.2 Standard non-successful HARP_Resolve example

 Like in 12.3.1, assume that X and Y are fully registered with the
 HARP server. Then the state of X and Y's HARP server table entry is:
 VALID. So lets look at the message traffic when X tries to send a
 message to Q. Further assume that interface Q is NOT configured UP,
 i.e. it is DOWN.  Since X doesn't have an entry for Q,
 1. Port X connects to the HARP server switch address and sends a
    HARP_REQUEST for Q's hardware address:
    HIPPI-LE Destination_Switch_Address = SWa
    HIPPI-LE Source_Switch_Address      = SWx
    HIPPI-LE Destination_IEEE_Address   = ULAa
    HIPPI-LE Source_IEEE_Address        = ULAx
    HARP ar$op                          = 1  (HARP_REQUEST)
    HARP ar$rpa                         = IPx
    HARP ar$tpa                         = IPq
    HARP ar$rha                         = SWx ULAx
    HARP ar$tha                         = 0 **
    ** is what we would like to find out
 2. The HARP server receives the HARP request and updates its entry
    for X if necessary. It then looks up IPq in its tables and doesn't
    find it. The HARP server then generates a HARP_NAK reply message.
    HIPPI-LE Destination_Switch_Address = SWx
    HIPPI-LE Source_Switch_Address      = SWa
    HIPPI-LE Destination_IEEE_Address   = ULAx
    HIPPI-LE Source_IEEE_Address        = ULAa
    HARP ar$op                          = 10  (HARP_NAK)
    HARP ar$rpa                         = IPx
    HARP ar$tpa                         = IPq
    HARP ar$rha                         = SWx ULAx
    HARP ar$tha                         = 0 ***
    *** No Answer, and notice that the fields do not get swapped,
        i.e. the HARP message is the same as the HARP_REQUEST
        except for the operation code.
 If there had been a broadcast capable HIPPI network, then there would
 not have been a reply.

Pittet Standards Track [Page 30] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

13 References

 [1]  ANSI X3.183-1991(R1996), Information Technology - High-
      Performance Parallel Interface - Mechanical, Electrical and
      Signaling Protocol Specification; (HIPPI-PH).
 [2]  ANSI X3.210-1998, Information Technology - High-Performance
      Parallel Interface - Framing Protocol; (HIPPI-FP).
 [3]  ANSI X3.218-1993, Information Technology - High-Performance
      Parallel Interface - Encapsulation of ISO 8802-2  (IEEE Std
      802.2) Logical Link Control Protocol Data Units; (HIPPI-LE).
 [4]  ANSI X3.222-1997, Information Technology - High-Performance
      Parallel Interface - Physical Switch Control; (HIPPI-SC).
 [5]  ANSI X3.300-1997, Information Technology - High-Performance
      Parallel Interface -  Serial Specification;  (HIPPI-Serial).
 [6]  Braden, R., "Requirements for Internet Hosts -- Communication
      Layers", STD 3, RFC 1122, October 1989.
 [7]  Bradely, T. and C. Brown, "Inverse Address Resolution Protocol",
      RFC 2390, September 1998.
 [8]  Bellovin, Steven M., "Security Problems in the TCP/IP Protocol
      Suite", ACM Computer Communications Review, Vol. 19, Issue 2,
      pp. 32-48, 1989.
 [9]  Deering, S, "Host Extensions for IP Multicasting", STD 5, RFC
      1112, August 1989.
 [10] Finlayson, R., Mann, T., Mogul, J. and M. Theimer, "A Reverse
      Address Resolution Protocol", RFC 903, June 1984.
 [11] ANSI/IEEE Std. 802.2-1989, Information Processing Systems -
      Local Area Networks - Logical Link Control, "IEEE Standards for
      Local Area Networks: Logical Link  Control", IEEE, New York, New
      York, 1985.
 [12] Laubach, Mark., "Classical IP and ARP over ATM", RFC 2225, April
      1998.
 [13] Plummer, D., "An Ethernet Address Resolution Protocol - or -
      Converting Network Addresses to 48-bit Ethernet Address for
      Transmission on Ethernet Hardware", RFC 826, November 1982.

Pittet Standards Track [Page 31] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

 [14] Renwick, J. and A. Nicholson, "IP and ARP on HIPPI", RFC 1374,
      October 1992.
 [15] Renwick, J., "IP over HIPPI", RFC 2067, January 1997.
 [16] Reynolds, J. and J. Postel, "Assigned Numbers", STD 2, RFC 1700,
      October 1994.
 [17] ANSI NCITS xxx.199x, Project 1245-D, Scheduled Transfer Protocol
      ANSI NCITS, Scheduled Transfer Protocol draft standard.
 [18] Bradner, S., "Key words for use in RFCs to Indicate Requirement
      Levels", BCP 14, RFC 2119, March 1997.

14 Acknowledgments

 This memo could not have come into being without the critical review
 from Greg Chesson, Carlin Otto, the high performance interconnect
 group of Silicon Graphics (specifically Jim Pinkerton, Brad Strand
 and Jeff Young) and the expertise of the ANSI T11.1 Task Group
 responsible for the HIPPI standards work.
 This memo is based on the second part of [14], written by John
 Renwick. ARP [13] written by Dave Plummer and Inverse ARP [7] written
 by T. Bradley and C. Brown provide the fundamental algorithms of HARP
 as presented in this memo. Further, the HARP server is based on
 concepts and models presented in [12], written by Mark Laubach who
 laid the structural groundwork for the HARP server.

15 Changes from RFC-1374 [14]

 RFC-2067 obsoletes RFC-1374 but left ARP outside of its scope because
 there was not enough implementation experience. This memo is an
 effort to clarify and expand the definition of ARP over HIPPI as
 found in RFC-1374 such that implementations will be more readily
 possible, especially considering forward interoperability with
 HIPPI-6400.
 The changes from RFC-1374 [14] are:
 o  A new message format to acknowledge the HIPPI hardware address
    format and to eliminate the requirement of HIPPI-LE ARP for HARP
    to function.
 o  Explicit registration phase.

Pittet Standards Track [Page 32] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

 o  Additional message formats: InHARP requests and replies as well as
    HARP_NAKs.
 o  Details about the IP subnetwork configuration.
 o  Details about table aging.
 o  IP broadcast emulation.

16 Author's Address

 Jean-Michel Pittet
 Silicon Graphics Inc
 1600 Amphitheatre Parkway
 Mountain View, CA 94043
 Phone: 650-933-6149
 Fax:   650-933-3542
 EMail: jmp@sgi.com, jmp@acm.org

Pittet Standards Track [Page 33] RFC 2834 ARP and IP Broadcast over HIPPI-800 May 2000

17 Full Copyright Statement

 Copyright (C) The Internet Society (2000).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Pittet Standards Track [Page 34]

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