INTERNET-DRAFT
Network Working Group K. Dobbins
Expire in six months T. Grant
Category: Informational D. Ruffen
E. Ziegler
Cabletron Systems Incorporated
April 1997
Address Resolution and Location Discovery (ARLD) Protocol
<draft-rfced-info-dobbins-00.txt>
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering task Force (IETF), its areas,
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Abstract
The Address Resolution and Location Discovery (ARLD) protocol
is part of the InterSwitch Message Protocol (ISMP). ISMP was
designed to facilitate interswitch communication within
distributed connection-oriented switching networks. The ARLD
protocol is used to resolve a packet destination address when
the source and destination pair of a packet does not match a
known connection. It is also used to provide end-station
address mobility between switches.
Table of Contents
Status of this Memo.....................................1
Abstract................................................1
1. Introduction........................................2
1.1 Data Conventions...............................2
2. ISMP Overview.......................................2
3. General ISMP Packet Format..........................3
3.1 Frame Header...................................3
3.2 ISMP Packet Header.............................4
3.3 ISMP Message Body..............................5
4. ARLD Protocol Operational Overview..................5
4.1 Definitions....................................5
4.1.1 Address.................................6
4.1.2 Undirected Messages.....................6
4.1.3 Switch Flood Path.......................6
4.1.4 Upstream Neighbor.......................6
4.1.5 Downstream Neighbor.....................6
4.2 Address Resolution.............................6
4.3 End-Station Address Mobility...................7
5. Tag/Length/Value (TLV) Format.......................9
6. Interswitch Resolve Message........................11
7. Interswitch New User Message.......................14
References.............................................17
Security Considerations................................17
Author's Addresses.....................................17
K. Dobbins, et. al. [Page 1]
DRAFT ARLD Protocol Specification April 1997
1. Introduction
This draft is being distributed to members of the Internet
community in order to solicit reactions to the proposals
contained herein. While the specification discussed here may
not be directly relevant to the research problems of the
Internet, it may be of interest to researchers and implementers.
1.1 Data Conventions
The methods used in this memo to describe and picture data
adhere to the standards of Internet Protocol documentation
[RFC1700], in particular:
The convention in the documentation of Internet Protocols
is to express numbers in decimal and to picture data in
"big-endian" order. That is, fields are described left to
right, with the most significant octet on the left and the
least significant octet on the right.
The order of transmission of the header and data described
in this document is resolved to the octet level. Whenever
a diagram shows a group of octets, the order of transmission
of those octets is the normal order in which they are read
in English.
Whenever an octet represents a numeric quantity the left
most bit in the diagram is the high order or most
significant bit. That is, the bit labeled 0 is the most
significant bit.
Similarly, whenever a multi-octet field represents a
numeric quantity the left most bit of the whole field is
the most significant bit. When a multi-octet quantity is
transmitted the most significant octet is transmitted
first.
2. ISMP Overview
The InterSwitch Message Protocol (ISMP) is used for interswitch
communication within distributed connection-oriented switching
networks. ISMP provides the following services:
- Topology services. Each switch maintains a distributed
topology of the switch fabric by exchanging the following
interswitch messages with other switches:
- Interswitch Keepalive messages (SNDM protocol) are sent by
each switch to announce its existence to its neighboring
switches and to establish the topology of the switch
fabric.
K. Dobbins, et. al. [Page 2]
DRAFT ARLD Protocol Specification April 1997
- Interswitch Spanning Tree BPDU messages and Interswitch
Remote Blocking messages (LSMP protocol) are used to
determine and maintain a loop-free flood path between all
network switches in the fabric. This flood path is used
for all undirected interswitch messages -- that is,
messages of the ARLD, SBCD and SFCT protocols.
- Interswitch Link State messages (VLS protocol) are used
to determine and maintain a fully connected mesh topology
graph of the switch fabric. Call-originating switches use
the topology graph to determine the path over which to
route a call connection.
- Address resolution services. Interswitch Resolve messages
(ARLD protocol) are used to resolve a packet destination
address when the packet source and destination pair does not
match a known connection. Interswitch New User messages
(also part of the ARLD protocol) are used to provide end-
station address mobility between switches.
- Tag-based flooding. A tag-based broadcast method (SBCD
protocol) is used to restrict the broadcast of unresolved
packets to only those ports within the fabric that belong to
the same VLAN as the source.
- Call tapping services. Interswitch Tap messages (SFCT
protocol) are used to monitor traffic moving between two end
stations. Traffic can be monitored in one or both
directions along the connection path.
NOTE
This document describes the ARLD protocol.
Other ISMP protocols are described in other
RFCs. See the References section for a
list of these related RFCs.
3. General ISMP Packet Format
ISMP packets are of variable length and have the following
general structure:
- Frame header
- ISMP packet header
- ISMP message body
3.1 Frame Header
ISMP packets are encapsulated within an IEEE 802-compliant
frame using a standard header as shown below:
K. Dobbins, et. al. [Page 3]
DRAFT ARLD Protocol Specification April 1997
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
00 | |
+ Destination address +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
04 | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Source address +
08 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
12 | Type | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
16 | |
+ +
: :
Destination address
This 6-octet field contains the Media Access Control (MAC)
address of the multicast channel over which all switches in
the fabric receive ISMP packets. The destination address of
all ISMP packets contain a value of 01-00-1D-00-00-00.
Source address
This 6-octet field contains the physical (MAC) address of
the switch originating the ISMP packet.
Type
This 2-octet field identifies the type of data carried
within the frame. The type field of ISMP packets contains
the value 0x81FD.
3.2 ISMP Packet Header
The ISMP packet header consists of 6 octets, as shown below:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
00 |///////////////////////////////////////////////////////////////|
://////// Frame header /////////////////////////////////////////:
+//////// (14 octets) /////////+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
12 |///////////////////////////////| Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
16 | ISMP message type | Sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
20 | |
+ +
: :
K. Dobbins, et. al. [Page 4]
DRAFT ARLD Protocol Specification April 1997
Frame header
This 14-octet field contains the frame header.
Version
This 2-octet field contains the version number of the
InterSwitch Message Protocol to which this ISMP packet
adheres. This document describes ISMP Version 2.0.
ISMP message type
This 2-octet field contains a value indicating which type of
ISMP message is contained within the message body. Valid
values are as follows:
1 (reserved)
2 Interswitch Keepalive messages (SNDM protocol)
3 Interswitch Link State messages (VLS protocol)
4 Interswitch Spanning Tree BPDU messages and Remote
Blocking messages (LSMP protocol)
5 Interswitch Resolve and New User messages (ARLD
protocol)
6 (reserved)
7 Tag-Based Flood messages (SBCD protocol)
8 Interswitch Tap messages (SFCT protocol)
ARLD protocol messages have a message type of 5.
Sequence number
This 2-octet field contains an internally generated sequence
number used by the various protocol handlers for internal
synchronization of messages.
3.3 ISMP Message Body
The ISMP message body is a variable-length field containing the
actual data of the ISMP message. The length and content of
this field are determined by the value found in the message
type field.
4. ARLD Protocol Operational Overview
The ARLD protocol provides two services:
- Resolution of packet destination addresses
- End-station address mobility between switches
4.1 Definitions
The following terms are used in this description of the ARLD
protocol.
K. Dobbins, et. al. [Page 5]
DRAFT ARLD Protocol Specification April 1997
4.1.1 Address
Within most computer networks, the concept of "address" is
somewhat elusive because different protocols can (and do) use
different addressing schemes and formats. To distinguish
between the various protocol-specific forms of addressing,
ARLD messages specify addresses in a format known as
Tag/Length/Value (TLV), unless otherwise noted in the text.
(See Tag/Length/Value (TLV) Format for a description of this
format.).
4.1.2 Undirected Messages
Undirected messages are those messages that are (potentially)
sent to all switches in the switch fabric -- that is, they are
not directed to any particular switch. ISMP messages of the
SBCD, ARLD, and SFCT protocols are undirected messages.
4.1.3 Switch Flood Path
The switch flood path is used to send undirected ISMP messages
throughout the switch fabric. The flood path is formed using a
spanning tree algorithm that provides a single path through the
switch fabric and guarantees loop-free delivery to every other
switch in the fabric.
4.1.4 Upstream Neighbor
A switch's upstream neighbor is that switch connected to the
incoming link of the switch flood path -- that is, the switch
from which the undirected message was received. Note that each
switch receiving an undirected message has, at most, one
upstream neighbor, and the originator of any undirected ISMP
message has no upstream neighbors.
4.1.5 Downstream Neighbor
A switch's downstream neighbors are those switches connected to
all outgoing links of the flood path except the link over which
the undirected message was received. Note that for each
undirected message some number of switches have no downstream
neighbors.
4.2 Address Resolution
When a switch receives a packet on one of its local access
ports, it examines the destination address of the packet to try
to determine where the packet should be sent -- that is, it
tries to "resolve" the destination address.
There are a variety of circumstances under which a switch may
not be able to resolve an address. For example, the address
may be a physical MAC address that the switch has not
K. Dobbins, et. al. [Page 6]
DRAFT ARLD Protocol Specification April 1997
previously encountered, or the address may be a high-level
network address (such as an IP address) for which the switch
has no MAC address mapping.
If the switch cannot resolve the address from within its own
local database, it formats and sends an Interswitch Resolve
request message to other switches in the switch fabric. The
Interswitch Resolve request message contains the destination
address as it was received within the packet, along with a list
of requested addressing information.
When a switch receives an Interswitch Resolve request message
from one of its upstream neighbors, it checks to see if the
destination end station is connected to one of its local access
ports. If so, it formulates an Interswitch Resolve response
message by filling in the requested address information, along
with its own MAC address. It then sets the message status
field to ResolveAck, and returns the message to its upstream
(requesting) neighbor.
If the switch cannot resolve the address, it forwards the
Interswitch Resolve request message to its downstream
neighbors. If the switch has no downstream neighbors, it sets
the message status field to Unknown, and returns the message to
its upstream (requesting) neighbor.
When a switch forwards an Interswitch Resolve request message
to its downstream neighbors, it keeps track of the number of
requests it has sent out and received back. It will only
respond back to its upstream (requesting) neighbor when one of
the following conditions occurs:
- It receives any response with a status of ResolveAck
- All downstream neighbors have responded with a status of
Unknown
Note that any Interswitch Resolve request message that is not
responded to within a certain predetermined time (currently 5
seconds) is assumed to have a response status of Unknown.
If the destination end station address cannot be resolved by
the above method, the originating switch will flood the packet
to the source VLAN using the Tag Based Flood message (SBCD
protocol).
4.3 End-Station Address Mobility
When a switch detects a new end-station address on one of its
local ports, it sends an Interswitch New User request message
over the switch flood path to all other switches in the fabric.
The purpose of the Interswitch New User request is two-fold:
K. Dobbins, et. al. [Page 7]
DRAFT ARLD Protocol Specification April 1997
- It informs the other switches that the end-station address
has changed and any entries for that end station in local
databases should be dealt with appropriately.
- It requests information about the static VLAN(s) to which
the end station has been assigned.
When a switch receives an Interswitch New User request message
from one of its upstream neighbors, it first forwards the
message to all its downstream neighbors. No actual processing
or VLAN resolution is attempted until the message reaches the
end of the flood path and begins its trip back along the return
path. This ensures that all switches in the fabric receive
notification of the new user and have synchronized their
databases.
If a switch receives an Interswitch New User request message
but has no downstream neighbors, it does the following:
- If the end station was previously connected to one of the
switch's local ports, the switch formulates an Interswitch
New User Response message by loading the VLAN identifier(s)
of the static VLAN(s) to which the end station was assigned,
along with its own MAC address. (VLAN identifiers are
stored in Tag/Length/Value (TLV) format.) The switch then
sets the message status field to NewUserAck, and returns the
message to its upstream (requesting) neighbor.
Otherwise, the switch sets the status field to
NewUserUnknown and returns the message to its upstream
neighbor.
- The switch then deletes the end station from its local
database, as well as any entries associated with the end
station in its connection table.
When a switch forwards an Interswitch New User request message
to its downstream neighbors, it keeps track of the number of
requests it has sent out and does not respond back to its
upstream neighbor until all requests have been responded to.
- As each response is received, the switch checks the status
field of the message. If the status is NewUserAck, the
switch retains the information in that response. When all
requests have been responded to, the switch returns the
NewUserAck response to its upstream neighbor.
- If all the Interswitch New User Request messages have been
responded to with a status of NewUserUnknown, the switch
checks to see if the end station was previously connected to
one of its local ports. If so, the switch formulates an
Interswitch New User Response message by loading the VLAN
identifier(s) of the static VLAN(s) to which the end station
K. Dobbins, et. al. [Page 8]
DRAFT ARLD Protocol Specification April 1997
was assigned, along with its own MAC address. (VLAN
identifiers are stored in Tag/Length/Value (TLV) format.)
The switch then sets the message status field to NewUserAck,
and returns the message to its upstream (requesting)
neighbor.
Otherwise, the switch sets the status field to
NewUserUnknown and returns the message to its upstream
neighbor.
- The switch then deletes the end station from its local
database, as well as any entries associated with the end
station in its connection table.
When the originating switch has received responses to all the
Interswitch New User Request messages it has sent, it does the
following:
- If it has received a response message with a status of
NewUserAck, it loads the new VLAN information into its local
database.
- If all responses have been received with a status of
NewUserUnknown, the originating switch assumes that the end
station was not previously connected anywhere in the network
and assigns it to a VLAN according to the VLAN membership
rules and order of precedence.
If any Interswitch New User Request message has not been
responded to within a certain predetermined time (currently 5
seconds), the originating switch recalculates the flood path
and resends the Interswitch New User Request message.
5. Tag/Length/Value (TLV) Format
Within most computer networks, the concept of "address" is
somewhat elusive because different protocols can (and do) use
different addressing schemes and formats. For example,
Ethernet (physical layer) addresses are six octets long, while
IP (network layer) addresses are only four octets long.
To distinguish between the various protocol-specific forms of
addressing, ARLD messages specify addresses in a format known
as Tag/Length/Value (TLV). This format uses a variable-length
construct as shown below:
K. Dobbins, et. al. [Page 9]
DRAFT ARLD Protocol Specification April 1997
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Tag :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value length | |
+-+-+-+-+-+-+-+-+ +
| Address value |
: :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Tag
This variable-length field specifies the type of address
contained in the structure. Note that the tag itself is a
complex structure consisting of a single octet containing
the length of the ASCII tag identifier string and a variable
number of octets containing the value of the identifier, as
shown below:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag ID length | |
+-+-+-+-+-+-+-+-+ +
| Tag identifier |
: :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The following address tag identifiers are currently defined:
ID string ID length
address.ethernet 16
address.ip 10
address.ip.udp 14
address.ipx 11
address.netbios 15
address.vlan 12
address.hostname 16
Value length
This 1-octet field contains the length of the value of the
address. The valid lengths associated with the currently
defined address types are shown below:
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DRAFT ARLD Protocol Specification April 1997
Identifier Value length
address.ethernet 6
address.ip 4
address.ip.udp 2
address.ipx 10
address.netbios 16
address.vlan <16
address.hostname <256
Address value
This variable-length field contains the value of the
address. The length of this field is stored in the Value
length field.
6. Interswitch Resolve Message
The ARLD Interswitch Resolve message consists of a variable
number of octets, as shown below:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
00 | |
+ Frame header / +
: ISMP packet header :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
20 | ARLD version | Opcode |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
24 | Status | Call Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
28 | |
+ Source MAC of packet +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
32 | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Originating switch MAC +
36 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
40 | |
+ Owner switch MAC +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
44 | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
48 | |
: Known destination address :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
n | Count | |
+-+-+-+-+-+-+-+-+ +
n1 | Resolve list |
: :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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DRAFT ARLD Protocol Specification April 1997
n = 46 + length of known address TLV
n1 = n + 4
In the following description of the message fields, the term
"originating" switch refers to the switch that issued the
original Interswitch Resolve request. The term "owner" switch
refers to that switch to which the destination end station is
attached. And the term "responding" switch refers to either
the "owner" switch or to a switch at the end of the control
path that does not own the end station but issues an
Interswitch Resolve response because it has no downstream
neighbors.
With the exception of the resolve list (which has a different
size and format in a Resolve response message), all fields of
an Interswitch Resolve message are allocated by the originating
switch, and unless otherwise noted below, are written by the
originating switch.
Frame header/ISMP packet header
This 20-octet field contains the frame header and the ISMP
packet header.
ARLD version
This 2-octet field contains the version number of the ARLD
protocol to which this message adheres. This document
describes ARLD Version 1.
Opcode
This 2-octet field contains the operation code of the
message. Valid values are as follows:
1 The message is a Resolve request.
2 The message is a Resolve response.
3 (unused in Resolve messages)
4 (unused in Resolve messages)
The originating switch writes a value of 1 to this field,
while the responding switch writes a value of 2.
Status
This 2-octet field contains the status of a Resolve response
message. Valid values are as follows:
0 The Resolve request succeeded (ResolveAck).
1 (unused)
2 The Resolve request failed (Unknown).
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This field is written by the responding switch.
Call tag
This 2-octet field contains the call tag of the end station
packet for which this Resolve request is issued. The call
tag is a 16-bit value (generated by the originating switch)
that uniquely identifies the packet.
Source MAC of packet
This 6-octet field contains the physical (MAC) address of
the end station that originated the packet identified by the
call tag.
Originating switch MAC
This 6-octet field contains the physical (MAC) address of
the switch that issued the original Resolve request.
Owner switch MAC
This 6-octet field contains the physical (MAC) address of
the switch to which the destination end station is attached
-- that is, the switch that was able to resolve the
requested addressing information. This field is written by
the owner switch.
If the status of the response is Unknown, this field is
irrelevant.
Known destination address
This variable-length field contains the known attribute of
the destination end-station address. This address is stored
in Tag/Length/Value format.
Count
This 1-octet field contains the number of address attributes
requested or returned. This is the number of items in the
resolve list.
Resolve list
This variable-length field contains a list of the address
attributes either requested by the originating switch or
returned by the owner switch. Note that in a Resolve
request message, this list contains only the tags of the
requested address attributes. On the other hand, a Resolve
response message with a status of ResolveAck contains the
full TLV of each resolved address attribute. The number of
entries in the list is specified in the count field.
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In an Interswitch Resolve response message, this field is
irrelevant if the status of the response is Unknown.
7. Interswitch New User Message
The ARLD Interswitch New User message consists of a variable
number of octets, as shown below:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
00 | |
+ Frame header / +
: ISMP packet header :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
20 | ARLD version | Opcode |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
24 | Status | Call Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
28 | |
+ Source MAC of packet +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
32 | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Originating switch MAC +
36 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
40 | |
+ Previous owner switch MAC +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
44 | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
48 | :
: MAC address of new user +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
70 | Count | |
+-+-+-+-+-+-+-+-+ +
74 | Resolve list |
: :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In the following description of the message fields, the term
"originating" switch refers to the switch that issued the
original Interswitch New User request. The term "previous
owner" switch refers to that switch to which the end station
was previously attached. And the term "responding" switch
refers to either the "previous owner" switch or to a switch at
the end of the control path that did not own the end station
but issues an Interswitch New User response because it has no
downstream neighbors.
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With the exception of the resolve list, all fields of an
Interswitch New User message are allocated by the originating
switch, and unless otherwise noted below, are written by the
originating switch.
Frame header/ISMP packet header
This 20-octet field contains the frame header and the ISMP
packet header.
ARLD version
This 2-octet field contains the version number of the ARLD
protocol to which this message adheres. This document
describes ARLD Version 1.
Opcode
This 2-octet field contains the operation code of the
message. Valid values are as follows:
1 (unused in a New User message)
2 (unused in a New User message)
3 The message is a New User request.
4 The message is a New User response.
The originating switch writes a value of 3 to this field,
while the responding switch writes a value of 4.
Status
This 2-octet field contains the status of a New User
response message. Valid values are as follows:
0 The end station VLAN(s) was successfully resolved
(NewUserAck).
1 (unused)
2 The end station VLAN(s) was not resolved
(NewUserUnknown).
This field is written by the responding switch.
Call tag
This 2-octet field contains the call tag of the end station
packet for which this New User request is issued. The call
tag is a 16-bit value (generated by the originating switch)
that uniquely identifies the packet that caused the switch
to identify the end station as a new user.
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Source MAC of packet
This 6-octet field contains the physical (MAC) address of
the end station that originated the packet identified by the
call tag.
Originating switch MAC
This 6-octet field contains the physical (MAC) address of
the switch that issued the original New User request.
Previous owner switch MAC
This 6-octet field contains the physical (MAC) address of
the switch to which the end station was previously attached
-- that is, the switch that was able to resolve the VLAN
information. This field is written by the previous owner
switch.
If the status of the response is Unknown, this field is
irrelevant.
MAC address of new user
This 24-octet field contains the physical (MAC) address of
the new user end-station, stored in Tag/Length/Value format.
Count
This 1-octet field contains the number of VLAN identifiers
returned. This is the number of items in the resolve list.
This field is written by the previous owner switch.
If the status of the response is Unknown, this field and the
resolve list are irrelevant.
Resolve list
This variable-length field contains a list of the VLAN
identifiers of all static VLANs to which the end station
belongs, stored in Tag/Length/Value format. The number of
entries in the list is specified in the count field. This
list is written by the previous owner switch.
If the status of the response is Unknown, this field is
irrelevant.
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DRAFT ARLD Protocol Specification April 1997
References
[RFC1700] Reynolds, S.J., Postel, J. Assigned Numbers.
October 1994.
Dobbins, K., et. al. ARLD Protocol Specification
Work in Progress.
Dobbins, K., et. al. ISM Protocol Specification
Work in Progress.
Dobbins, K., et. al. LSMP Protocol Specification
Work in Progress.
Dobbins, K., et. al. SBCD Protocol Specification
Work in Progress.
Dobbins, K., et. al. SNDM Protocol Specification
Work in Progress.
Dobbins, K., et. al. VLS Protocol Specification
Work in Progress.
Security Considerations
Security issues are not discussed in this document.
Authors' Addresses
Cabletron Systems, Inc., is located at:
Post Office Box 5005
Rochester, NH 03866-5005
(603) 332-9400
Kurt Dobbins Email: dobbins@ctron.com
Tom Grant Email: tgrant@ctron.com
Dave Ruffen Email: ruffen@ctron.com
Eric Ziegler Email: ziegler@ctron.com
INTERNET-DRAFT EXPIRES: OCTOBER 1997 INTERNET-DRAFT