Network Working Group J.-M. Pittet
INTERNET DRAFT Silicon Graphics Inc.
Expires May 1999 November 1998
ARP and IP Broadcast over HIPPI-800
<draft-pittet-hippiarp-01.txt>
Status of this memo
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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 (a.k.a. Gigabyte Systems Network,
GSN).
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TABLE OF CONTENTS
1. Introduction
2. Scope
2.1 Changes from RFC-1374
2.2 Terminology
3. Definitions
3.1 Global Concepts
3.2 Glossary
4. IP Subnetwork Configuration
4.1 Background
4.2 HIPPI LIS Requirements
5. HIPPI Address Resolution Protocol - HARP
5.1 HARP Algorithm
5.1.1 Selecting the authorative HARP service
5.1.2 HARP registration phase
5.1.3 HARP operational phase
5.2 HARP Client Operational Requirements
5.3 Receiving Unknown HARP Messages
5.4 HARP Server Operational Requirements
5.5 HARP and Permanent ARP Table Entries
5.6 HARP Table Aging
6. HARP Message Encoding
6.1 HIPPI-LE Header of HARP Messages
6.1.1 IEEE 802.2 LLC
6.1.2 SNAP
6.1.3 Diagram
6.2 HIPPI Hardware Address Formats and Requirements
6.2.1 48-bit Universal LAN MAC Addresses
6.2.2 I-Field requirements for HARP messages
6.3 HARP and InHARP Message Formats
6.3.1 Example Message encodings
6.3.2 HARP_NAK message format
6.3.3 Combined HIPPI-LE and HARP message addresses
7. Broadcast and Multicast
7.1 Protocol for an IP Broadcast Emulation Server - PIBES
7.2 IP Broadcast Address
7.3 IP Multicast Address
7.4 A Note on Broadcast Emulation Performance
8. HARP for Scheduled Transfer
9. Discovery of One's Own Switch Address
9.1 Switch Address Discovery
10. Security
11. Open Issues
12. HARP Examples
12.1 Registration Phase of Client Y on Non-broadcast Hardware
12.2 Registration Phase of Client Y on Broadcast Hardware
12.3 Operational Phase (phase II)
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12.3.1 Standard successful HARP_Resolve example
12.3.2 Standard non-successful HARP_Resolve example
13. References
14. Acknowledgments
15. Author's Address
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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
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 [18]
describes the encapsulation of IP over HIPPI-800. This memo takes up
where the working group and RFC-2067 [18] 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. Scope
2.1 Changes from RFC-1374 [17]
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 [17] are:
o A new message format to acknowledge the HIPPI hardware address
format and to eliminate the requirement of HIPPI-LE ARP for HARP
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to function.
o Explicit registration phase.
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.
2.2 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.
3. Definitions
3.1 Global concepts used
In the following discussion, the terms "requester" and "target" are
used to identify the node initiating the address resolution request
and the node 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.
3.2 Glossary
Broadcast
A distribution mode which transmits a message to all nodes.
Particularly also the node sending the message.
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.
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Destination
The HIPPI node 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
[15] 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).
HIPPI-Serial
An implementation of HIPPI in serial fashion on coaxial cable or
optical fiber. (see [5])
HRAL
The HARP Request Address List (see section 4.2).
Hardware (HW) address
The hardware address consisting of an I-Field and an optional ULA
(see section 6.2)
Host
An entity, usually a computer system, that may have one or more HIPPI
nodes and which may serve as a client or a HARP server.
Node
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. A node may be
an Internet host, bridge, router, or gateway.
PIBES
The Protocol for Internet Broadcast Emulation Server (see section 7).
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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 map Switch Addresses
to physical 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 node 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 node on an Ethernet, FDDI, 802 network, or HIPPI-SC LAN.
4. IP Subnetwork Configuration
4.1 Background
ARP (address resolution protocol) as defined in [13] 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 nodes in the LIS.
Communication to nodes located outside of the local LIS is usually
provided via an IP router. This router is a HIPPI node 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, nodes 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 an
consequence of using IP and choosing to have multiple LIS's on the
same HIPPI fabric.
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
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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 node MUST contain
the node'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 one or more addresses identifying
the address resolution service(s). All HARP clients MUST be
configured identically to have the same addresses(es) in the HRAL.
The HRAL MUST be the same for all nodes within a LIS. The HRAL
MUST contain at least one, and MAY contain more than one HIPPI HW
address, identifying the individual HARP service(s) that have
authoritative responsibility for resolving HARP requests of all IP
members located within the LIS. An LIS MUST have at least one
HARP service entry configured and available to all members of the
LIS.
The first address SHALL be the reserved address that the switches
use for broadcasting messages (i.e. the address for "IP traffic
conventionally directed to the IEEE 802.1 broadcast address:
0xFE1" [4]).
It is REQUIRED that the second address be the address for
"Messages pertaining to (the) ... address resolution requests:
0xFE0 " [4]. By default the ULA for the HARP server entry is
00:00:00:00:00:00
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).
Within the restrictions mentioned above and in Section 6.2.2, local
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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 further details are
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 [15]. Knowing the Internet address,
conventional networks use ARP to discover another node's hardware
address. HARP presented in this section further specifies the
combination of the original protocol definitions to form a coherent
address resolution service that is independent of the hardware's
broadcast capability.
InHARP is 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 node MUST know its IP and its
hardware addresses. The ULA is optional but is RECOMMENDED if
interoperability with conventional networks is desired.
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 node which maps remote nodes'
IP addresses to a hardware addresses, so that when an application
requests a connection to a remote node by its IP address, the
hardware address can be determined, a correct HIPPI-LE header can be
built, and a connection to the node can be established using the
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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 node 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 authorative HARP service
Within the HIPPI LIS, there SHALL be an authorative HARP service. To
select the authorative HARP service, each node needs to determine if
it is connected to a broadcast network. At each point in time there
is only one authorative HARP service.
The node SHALL send an InHARP_REQUEST to the first address in the HRAL
(0x07000FE1 FF:FF:FF:FF:FF:FF). If the node 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 authorative
HARP service is the broadcast entry.
If the node is connected to a non broadcast capable network, then the
node 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 authorative 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 authorative one. On A non-broadcast network, the node 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 authorative HARP service is non-
responsive, then the node will considerthe next address in the HRAL
as a candidate for the selected address and send an InARP_REQUEST.
The authorative HARP server SHOULD BE considered non-responsive when
it has failed to reply to one or more registration requests by the
client (see section 5.1.2 and 5.2), any two HARP_REQUESTs in the last
120 seconds or if an external agent has detected failure of the
authorative HARP server. The details of such an external agent and
its interaction with the HARP client are beyond the scope of this
document. Should a authorative HARP server become non-responsive,
then the registration process should be restarted. Alternative
methods for choosing a authorative HARP service are not prohibited.
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5.1.2 HARP registration phase
HARP clients SHALL initiate the registration phase by sending an
InHARP_REQUEST message using all addresses in the HRAL. 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 authorative HARP service as
described in section 5.1.1.
When nodes are initiated they send an InHARP_REQUEST to the selected
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 node sees its own InHARP_REQUEST: then the node is connected to
a broadcast capable network. The first address becomes and remains
the selected address for the HARP service.
2. The node does not receive its InHARP_REQUEST: then the node is
connected to a non-broadcast capable network.
In the second case, the node SHALL choose the next address in the
HRAL as a candidate for a selected address and send an InHARP_REQUEST
to that address: (0x07000FE0 00:00:00:00:00:00).
If the node receives its own message, then the node itself is the
HARP server and the node is REQUIRED to provide broadcast services
using the PIBES (see section 7).
If on the other hand, the node receives an InHARP_REPLY, then it is a
HARP client and not a HARP server. In both cases, the current
candidate address becomes the authorative HARP service address.
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
node 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
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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 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 information about other IP
members through the sending of HARP_REQUESTS to the selected address
in the HRAL and the reception of HARP_REPLYs. The client is fully
operational during the operational phase.
In this phase, the client's behavior for requesting HARP resolution
is the same for broadcast or non-broadcast HIPPI-SC switched
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 node it SHALL formulate and send a reply message.
A node is the target of an address resolution request if at least ONE
of the following statements is true of the request:
1. The node's IP address is in the target protocol address field
(ar$tpa) of the HARP message.
2. The node's ULA (if non-zero), is in the ULA part of the Target
Hardware Address field (ar$tha) of the message.
3. The node'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 node is a HARP server.
NOTE: It is RECOMMENDED to have a HARP server run on a node that has
a non-zero ULA.
5.2 HARP Client Operational Requirements
The HARP client is responsible for contacting the HARP server(s) to
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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") or
assigned 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 node. 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 can have multiple replies. (Refer to Section 7,
"Protocol Operation" in RFC-1293 [7].)
3. React to address resolution reply messages appropriately to
build/refresh its own client HARP table entries. All (solicited
and unsolicited) HARP_REPLYs from the authorative 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 to
build/refresh its client HARP table entries. (Refer to Section
7, "Protocol Operation" in [7].)
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 showed that the underlying network supports
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broadcast, then the operation is NOT REQUIRED.
5.3 Receiving Unknown HARP Messages
If a HARP client receives a HARP message with an operation code
(ar$op) that it is not coded to 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 accepts HIPPI connections from other HIPPI nodes. The
HARP server expects an InARP_REQUEST as first message from the
client. A server examines the IP address, the hardware address of the
InARP_REQUEST and adds or updates its HARP table entry <IP
address(es), switch address, ULA> as well as the time stamp.
A HARP server replies to HARP_REQUESTs and InARP_REQUESTs based on
the information which it has in its table. The HARP server replies
SHALL contain the hardware type and corresponding format of the
request (see also sec. 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.
+---+----------+----------+------------+------------------+
| # | 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 decr 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
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f: add new HW -> IP link to HW entry
Examples of when this could happen:
1: supplemental message
Just update timer.
2: move an IP alias to an existing interface
If the InHARP_REQUEST requester's IP address duplicates a table
entry IP address (e.g. IPa <-> HWa) and the InHARP_REQUEST
hardware 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 address duplicates a table
entry IP address and the InHARP_REQUEST hardware address does not
match the table entry hardware address, then a new HW entry SHALL
be created and the IP entry SHALL be updated.
4: add IP alias to table
If the InHARP_REQUEST requester's hardware address duplicates a
hardware address entry, but there is no IP entry matching the
received IP address, then 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 sect. 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.
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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 nodes.
Dynamic information overrides static HARP information, e.g. when a
HARP_REPLY from the HARP server indicates that the client's mapping
needs to be updated, then the client SHALL update the entry and note
that the entry is not permanent any more.
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.
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 node
referred to by this entry while revalidation is in progress, as long
as the table entry is not invalidated. The client MUST revalidate the
invalidated entry prior to transmitting any non address resolution
traffic to the node referred to by this entry.
The client revalidates the entry by querying the HARP server. 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
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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" [18]. 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 node being able to accept 64-bit
HIPPI connections.
Message_Type SHALL contain 0 to indicate data. HARP messages are
identified fist using the Ethertype and the ar$op field in the HARP
message and NOT the HIPPI-LE [3] defined ARP operations.
Destination_Switch_Address, SHALL be the Switch Address of the
destination node.
Destination_IEEE_Address SHALL be the ULA of the destination node, 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.
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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 [21]:
InHARP = InARP = HARP = ARP = 2054 = 0x0806.
The total size of the LLC/SNAP header is fixed at 8-bytes.
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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 | 36 |
+-----+-+-------+-----------------------+-----------------------+
2 |[LA] |W|M_Type | 000 | Replyer's Switch Addr |
+-----+-+-------+-----------------------+-----------------------+
3 | D_A_T | S_A_T | 000 |Requester's Switch Addr|
+-------+-------+---------------+-------+-----------------------+
4 | 00 00 | |
+-------------------------------+ |
5 | Replyer ULA |
+-------------------------------+-------------------------------+
6 | [LA] | |
+-------------------------------+ |
7 | Requester's 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) is the number of bytes in the HARP message.
+====+ denotes the boundary between D1 and D2 areas.
[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
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"D_A_T" = Destination_Address_Type SHALL be 2
"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 1 | ULA byte 1 | ULA byte 2 | ULA byte 3 |
+---------------+---------------+---------------+---------------+
| ULA byte 4 | ULA byte 5 |
+---------------+---------------+
Where "XXX" are 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 specifies the Universal LAN MAC Address format.
The globally unique part of the 48-bit space is administered by the
IEEE. Each node on a HIPPI-SC LAN should be assigned a ULA.
Multiple ULAs may be used if a node contains more than one IEEE 802.2
LLC protocol entity.
The format of the HIPPI hardware address within its HARP message
follows IEEE 802.1A canonical bit order and HIPPI-FP bit and byte
order. For example the requester's ULA part of the HIPPI hardware
address would decompose to:
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31 23 15 7 0
+---------------+---------------+---------------+---------------+
|ULA oct 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 node 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), 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 [13]. 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 [17].
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$rpa 32 bits requester's protocol address
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ar$tpa 32 bits target's protocol address
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$rln - SHALL contain 10 IF this is a HIPPI-800 link
ELSE, for HIPPI-6400, it SHALL contain 6.
ar$thl - SHALL contain 10 IF this is a HIPPI-800 link
ELSE, for HIPPI-6400, it SHALL contain 6.
ar$rha - in requests and NAKs it SHALL contain the requester's ULA
In replies it SHALL contain the target node's ULA.
ar$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
node's IP address.
ar$tha - in requests and NAKs it SHALL contain the target's ULA
if known, otherwise zero.
In other replies it SHALL contain the requester's ULA.
ar$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, "HIPPI Hardware Address
Formats and Requirements" above), except for the alignment of the
ULAs with respect to the 32-bit HIPPI word, which is different
between ARP and HIPPI-LE. No bit reversal is necessary as is
required with FDDI.
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31 28 23 21 15 10 7 2 0
+-----+---------+-+-+-----------+---------+-----+---------+-----+
0 | 04 |1|0| 000 | 03 | 0 |
+---------------+-+-+---------------------+---------------+-----+
1 | 36 |
+-----+-+-------+-----------------------+-----------------------+
2 |[LA] |W|MsgT= 0| 000 | Dest. Switch Addr |
+-----+-+-------+-----------------------+-----------------------+
3 | 2 | 2 | 000 | Source's Switch Addr |
+---------------+---------------+-------+-----------------------+
4 | 00 00 | |
+-------------------------------+ |
5 | Destination ULA |
+-------------------------------+-------------------------------+
6 | [LA] | |
+-------------------------------+ |
7 | Source's ULA |
+===============+===============+===============+===============+
8 | AA | AA | 03 | 00 |
+---------------+---------------+---------------+---------------+
9 | 00 | 00 | Ethertype (2054) |
+---------------+---------------+-------------------------------+
10 | hrd (28) | pro (2048) |
+---------------+---------------+---------------+---------------+
11 | op (ar$op) | pln (6) | rhl (q) |
+---------------+---------------+---------------+---------------+
12 | thl = (x) | Requester's IP Address upper (24 bits) |
+---------------------------------------------------------------+
13 | Req. IP lower | Target's IP Address upper (24 bits) |
+---------------+-----------------------------------------------+
14 | Tgt. IP lower | Requester's HIPPI Hardware Address bytes 0 - 2|
+---------------+-----------------------------------------------+
15 | Requester's HIPPI Hardware Address bytes 3 - 6 |
+-----------------------------------------------+---------------+
16 | Requester's HW Address bytes 7 - 9 |Tgt's HW oct 0|
+---------------+---------------+---------------+---------------+
17 | Target's HIPPI Hardware Address bytes 1 - 4 |
+---------------------------------------------------------------+
18 | Target's HIPPI Hardware Address bytes 5 - 8 |
+---------------+---------------+---------------+---------------+
19 | Tgt HW oct 9 | FILL | FILL | FILL |
+---------------+---------------+---------------+---------------+
HARP - InHARP Message
6.3.1 Example Message encodings:
HARP_REQUEST message
HARP ar$op = 8 (InHARP_REQUEST)
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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
HARP_REPLY message format
HARP ar$op = 9 (InHARP_REPLY)
HARP ar$rpa = IPs * HARP ar$tpa = IPy
HARP ar$rha = SWa ULAa HARP ar$tha = SWy ULAy
* answer we were looking for
InHARP_REQUEST message format
HARP ar$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 and 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)
Requester's IP Address (HARP)
Requester's ULA (HARP)
Requester's Switch Address (HARP)
Target's IP Address (HARP)
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Target's ULA (HARP)
Target's 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 node, 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 standard networking protocols 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 address (FF.FF.FF.FF) 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.
It is RECOMMENDED that the broadcast server run on the same node as
the HARP server since this memo does not define the protocol of
exchanging the valid HARP table.
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7.2 IP Broadcast Address
This memo only defines IP broadcast. It is independent of the
underlying hardware addressing and broadcast capabilities. Any node can
differentiate between IP traffic directed to itself and a broadcast
message sent to it through looking at the IP address. All IP broadcast
messages SHALL use the IP LIS broadcast address (FF.FF.FF.FF).
It is RECOMMENDED that the PIPES run on the same node 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 addresses are mapped to the IP
broadcast address (FF.FF.FF.FF).
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 nodes, 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 nodes. The
broadcast server could forward the message destined to the node 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 all general 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.
8 HARP for Scheduled Transfer [22]
This RFC also applies for resolving addresses used with Scheduled
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Transfer (ST) over HIPPI-800 instead of IP. This RFC's message
types and algorithms can be used for ST (since ST uses Internet
Addresses) as long as there is also an IP over HIPPI implementation
on all the nodes.
9 Discovery of One's Own Switch Address
This HARP specification assumes that each node has prior knowledge
of its own hardware address. This address may be manually configured,
by means that are outside the scope of this memo. If a broadcast
capability exists, the node may discover its own address automatically
when it starts up, using a protocol defined in HIPPI-LE.
If on the other hand, one can not rely on the underlying hardware
to support broadcast, then a node may discover its own logical
address through the algorithm described in section 9.1.
9.1 Switch Address Discovery
Nodes are NOT REQUIRED to implement this protocol but are
encouraged to do so since it reduces the administrative overhead of
systems administration. The algorithm presented in this section is
based on John Renwick's work as detailed in RFC-1374 and on the
algorithm found in HIPPI-LE. 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 node implements this algorithm it SHALL form a HIPPI-LE message
as defined in HIPPI-LE: containing an Self Address Resolution Request
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 (containing zero).
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 = 0 (unknown)
HIPPI-LE Source_Address_Type = 0 (undefined)
HIPPI-LE Source_Switch_Address = 0 (unknown)
HIPPI-LE Destination_IEEE_Address = my ULA
HIPPI-LE Source_IEEE_Address = my ULA
There is no D2 data; the message contains only the HIPPI-FP header
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and D1 Area with the HIPPI-LE header.
Nodes SHALL start with the HIPPI broadcast address 0xFE1 and if no
reply is received, SHALL continue with the logical address of 0x000
(START) and increment the value by one each subsequent try. The node
SHALL try until reaching 0xFFF or at least until it sees its own
address resolution request. It is RECOMMENDED to make the starting
address (START) of this scan a configurable parameter for the network
since some networks have equipment that does not gracefully handle
HIPPI-LE messages.
After a node sends the[se] request[s], two positive outcomes are
possible:
o the node receives its own request(s), and obtains one of its own
Switch Address, or
o the node receives an AR_S_Response with the
Destination_Switch_Address filled in.
10 Security
Not all of the security issues relating to ARP over HIPPI are clearly
understood at this time.
There are known security issues relating to node 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.
11 Open Issues
o Synchronization and coordination of multiple HARP servers and
multiple broadcast servers are left for further study.
o HARP messages are not authenticated. This is a potentially
serious flaw in the overall system by allowing a mechanism by
which corrupt information may be introduced into the server
system.
12 HARP Examples
Assume a HIPPI-SC switch is installed with three connected nodes: X,
Y, and a. Each node 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
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port that is mapped to the address HWa (SWa, ULAa), this address is
the selected HIPPI hardware address in the HRAL (HARP Request Address
List).
The HARP server's table is empty. Nodes 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 node database) but neither
knows the other's ULA or Switch Address. Both nodes 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. As well as ar$rhl = ar$thl = 9 since these are
all
HIPPI-800 examples.
12.1 Registration Phase of Client Y on Non-broadcast Hardware
Node Y starts: its HARP table entry state for the server: PENDING
1. Node Y initiates its interface and sends an InHARP_REQUEST to
the HWa after starting a table entry for the 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$rpa = IPs *
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HARP ar$tpa = IPy
HARP ar$rha = SWa ULAa
HARP ar$tha = SWy ULAy
* answer we were looking for
3. Node 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 selected address in
the HRAL would be mapped to the broadcast address, HWb = SWb, ULAb
(likely 0xFE1 and FF.FF.FF.FF.FF.FF).
Node Y starts: its HARP table entry state for HWa: PENDING
1. Node 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$tha = SWb ULAb
** is what we would like to find out
2. Since the network is a broadcast network, client Y will see an
InHARP_REQUEST, it examines the source addresses. Since they
are the same as what Y filled in the InHARP_REQUEST, Y can
deduce that it is connected to a broadcast medium. Node Y
completes its table entry for HWa. This entry will not timeout
since it is considered less than likely for a particular
underlying hardware type to loose its quality of being able to do
broadcast and therefore this mapping will never change.
12.3 Operational Phase (phase II)
The Operational Phase of the HARP protocol as specified in this memo
is the same for both possibilities of a broadcast and non-broadcast
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capable HIPPI hardware. The selected address in the HRAL for this
example section will be HWa: <SWa, ULAa> and IPs for simplicity
reasons.
12.2.1 Standard successful HARP_Resolve example
Assume the same process (steps 1-3 of section 10.1) happened for node
X. Then the state of X and Y's tables is: the HARP server table entry
is in the VALID state. So lets look at the message traffic when X
tries to send a message to Y. Since X doesn't have an entry for Y,
1. Node X connects to the authorative address of the HRAL and sends
a HARP_REQUEST for Y's hardware address:
HIPPI-LE Destination_Switch_Address = SWa
HIPPI-LE Source_Switch_Address = SWx
HIPPI-LE Destination_IEEE_Address = ULAa
HIPPI-LE Source_IEEE_Address = ULAx
HARP ar$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$tha = SWx ULAx
* answer we were looking for
3. Node X connects to node Y and transmits an IP message with the
following information in the HIPPI-LE header:
HIPPI-LE Destination_Switch_Address = SWy
HIPPI-LE Source_Switch_Address = SWx
HIPPI-LE Destination_IEEE_Address = ULAy
HIPPI-LE Source_IEEE_Address = ULAx
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If there had been a broadcast capable HIPPI network, the target nodes
would themselves have received the HARP_REQUEST of step 2 above
and responded to them in the same way the HARP server did.
12.2.2 Standard non-successful HARP_Resolve example
Like in 12.2.1, assume that X and Y are fully registered with the
HARP server. Then the state of X and Y's HARP server table entry
is: VALID. So lets look at the message traffic when X tries to send a
message to Q. Further assume that interface Q is NOT configured UP,
i.e. it is DOWN. Since X doesn't have an entry for Q,
1. Node X connects to the HARP server switch address and sends
a HARP_REQUEST for Q's hardware address:
HIPPI-LE Destination_Switch_Address = SWa
HIPPI-LE Source_Switch_Address = SWx
HIPPI-LE Destination_IEEE_Address = ULAa
HIPPI-LE Source_IEEE_Address = ULAx
HARP ar$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 any reply.
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13 References
[1] ANSI X3.183-1991, High-Performance Parallel Interface -
Mechanical, Electrical and Signaling Protocol Specification;
ISO/IEC 11518-1:1995, High-Performance Parallel Interface -
Part 1: Mechanical, Electrical, and Signaling Protocol
Specification (HIPPI-PH).
[2] ANSI X3.210-1992, High-Performance Parallel Interface - Framing
Protocol; ISO/IEC 11518-2:1995 High-Performance Parallel Interface
- Part 2: Framing Protocol (HIPPI-FP).
[3] ANSI X3.218-1993, High-Performance Parallel Interface -
Encapsulation of ISO 8802-2 (IEEE Std 802.2) Logical Link
Control Protocol Data Units (802.2 Link Encapsulation);
ISO/IEC 11518-3:1995 High-Performance Parallel Interface -
Part 3: Encapsulation of ISO/IEC 8802-2 Logical link control
protocol data units(HIPPI-LE).
[4] ANSI X3.222-1997, High-Performance Parallel Interface - Physical
Switch Control; ISO/IEC 11518-6:199x High-Performance Parallel
Interface - Part 6: Physical Switch Control (HIPPI-SC).
[5] ANSI X3.300-1997, High-Performance Parallel
Interface - Serial Specification, ISO/IEC 11518-6:199x
High-Performance Parallel Interface -
Part 8: Serial Specification (HIPPI-Serial)
[6] Braden, R., "Requirements for Internet Hosts -- Communication
Layers", RFC-1122, USC/Information Sciences Institute, October
1989.
[7] Bradely, T., and Brown, C., "Inverse Address Resolution
Protocol", RFC-1293, USC/Information Sciences Institute, January
1992.
[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", RFC-1112,
USC/Information Sciences Institute, August 1989.
[10] Finlayson, R., Mann, T., Mogul, J., and Theimer, M., "A Reverse
Address Resolution Protocol", RFC-903, Stanford University, June
1984.
[11] IEEE, "IEEE Standards for Local Area Networks: Logical Link
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Control", IEEE, New York, New York, 1985.
[12] IEEE, "IEEE Standards for Local Area Networks: Logical Link
Control", IEEE, New York, New York, 1985.
[13] Laubach, Mark., "Classical IP and ARP over ATM", RFC-1577,
Hewlett-Packard Laboratories, January 1994
[14] Mogul, J.C., and Deering, S.E., "Path MTU Discovery", RFC-1191,
Stanford University, November, 1990.
[15] Plummer, D., "An Ethernet Address Resolution Protocol - or -
Converting Network Addresses to 48-bit Ethernet Address for
Transmission on Ethernet Hardware", RFC-826, MIT, November 1982.
[16] Postel, J., "Internet Protocol", STD 5, RFC-791, USC/Information
Sciences Institute, September 1981.
[17] Renwick, J., Nicholson, A., "IP and ARP on HIPPI", RFC-1374,
Cray Research, Inc., October 1992.
[18] Renwick, J., "IP over HIPPI", RFC-2067, NetStar, Inc., January
1997.
[20] Reynolds, J.K., and Postel, J., "Assigned Numbers", STD 2, RFC-
1340, USC/Information Sciences Institute, July 1992.
[21] Reynolds, J., and J. Postel, "Assigned Numbers", STD 2,
RFC-1700, USC/Information Sciences Institute, October 1994.
[22] ANSI NCITS, Scheduled Transfer Protocol draft standard.
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 [17], written by John
Renwick. ARP [15] written by Dave Plummer and Inverse ARP [7] written
by Terry Bradley and Caralyn Brown provide the fundamental algorithms
of HARP as presented in this memo. Further, the HARP server is based
on concepts and models presented in [13], written by Mark Laubach who
laid the structural groundwork for the HARP server.
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15 Author's Address
Jean-Michel Pittet
Silicon Graphics Inc
2011 N. Shoreline Ave
Mountain View, CA 94040
Phone: 650-933-6149
Fax: 650-933-3542
EMail: jmp@sgi.com
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