rfc2643.txt
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Network Working Group D. Ruffen
Request for Comments: 2643 T. Len
Category: Informational J. Yanacek
Cabletron Systems Incorporated
August 1999
Cabletron's SecureFast VLAN Operational Model
Version 1.8
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
Abstract
Cabletron's SecureFast VLAN (SFVLAN) product implements a distributed
connection-oriented switching protocol that provides fast forwarding
of data packets at the MAC layer. The product uses the concept of
virtual LANs (VLANs) to determine the validity of call connection
requests and to scope the broadcast of certain flooded messages.
Table of Contents
1. Introduction............................................. 3
1.1 Data Conventions..................................... 3
1.2 Definitions of Commonly Used Terms................... 4
2. SFVLAN Overview.......................................... 6
2.1 Features............................................. 7
2.2 VLAN Principles...................................... 8
2.2.1 Default, Base and Inherited VLANs.............. 8
2.2.2 VLAN Configuration Modes....................... 8
2.2.2.1 Endstations............................ 8
2.2.2.2 Ports.................................. 9
2.2.2.3 Order of Precedence.................... 9
2.2.3 Ports with Multiple VLAN Membership............ 10
2.3 Tag/Length/Value Method of Addressing................ 10
2.4 Architectural Overview............................... 11
3. Base Services............................................ 13
4. Call Processing.......................................... 14
4.1 Directory Service Center............................. 14
4.1.1 Local Add Server............................... 15
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RFC 2643 Cabletron's SecureFast VLAN Operational Model August 1999
4.1.2 Inverse Resolve Server......................... 15
4.1.3 Local Delete Server............................ 18
4.2 Topology Service Center.............................. 18
4.2.1 Neighbor Discovery Server...................... 18
4.2.2 Spanning Tree Server........................... 18
4.2.2.1 Creating and Maintaining
the Spanning Tree........... 19
4.2.2.2 Remote Blocking........................ 19
4.2.3 Link State Server.............................. 20
4.3 Resolve Service Center............................... 21
4.3.1 Table Server................................... 22
4.3.2 Local Server................................... 22
4.3.3 Subnet Server.................................. 22
4.3.4 Interswitch Resolve Server..................... 22
4.3.5 Unresolvable Server............................ 23
4.3.6 Block Server................................... 23
4.4 Policy Service Center................................ 24
4.4.1 Unicast Rules Server........................... 24
4.5 Connect Service Center............................... 25
4.5.1 Local Server................................... 25
4.5.2 Link State Server.............................. 25
4.5.3 Directory Server............................... 26
4.6 Filter Service Center................................ 26
4.7 Path Service Center.................................. 26
4.7.1 Link State Server.............................. 26
4.7.2 Spanning Tree Server........................... 27
4.8 Flood Service Center................................. 27
4.8.1 Tag-Based Flood Server......................... 27
5. Monitoring Call Connections.............................. 27
5.1 Definitions.......................................... 27
5.2 Tapping a Connection................................. 28
5.2.1 Types of Tap Connections....................... 28
5.2.2 Locating the Probe and Establishing
the Tap Connection.......... 29
5.2.3 Status Field................................... 30
5.3 Untapping a Connection............................... 31
6. Interswitch Message Protocol (ISMP)...................... 32
6.1 General Packet Structure............................. 32
6.1.1 Frame Header................................... 32
6.1.2 ISMP Packet Header............................. 33
6.1.2.1 Version 2.............................. 33
6.1.2.2 Version 3.............................. 34
6.1.3 ISMP Message Body.............................. 35
6.2 Interswitch BPDU Message............................. 35
6.3 Interswitch Remote Blocking Message.................. 36
6.4 Interswitch Resolve Message.......................... 37
6.4.1 Prior to Version 1.8........................... 37
6.4.2 Version 1.8.................................... 41
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RFC 2643 Cabletron's SecureFast VLAN Operational Model August 1999
6.5 Interswitch New User Message......................... 46
6.6 Interswitch Tag-Based Flood Message.................. 49
6.6.1 Prior to Version 1.8........................... 49
6.6.2 Version 1.8.................................... 52
6.7 Interswitch Tap/Untap Message........................ 55
7. Security Considerations.................................. 58
8. References............................................... 58
9. Authors' Addresses....................................... 59
10. Full Copyright Statement................................ 60
1. Introduction
This memo 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.
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RFC 2643 Cabletron's SecureFast VLAN Operational Model August 1999
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.
1.2 Definitions of Commonly Used Terms
This section contains a collection of definitions for terms that have
a specific meaning for the SFVLAN product and that are used
throughout the text.
Switch ID
A 10-octet value that uniquely identifies an SFVLAN switch within
the switch fabric. The value consists of the 6-octet base MAC
address of the switch, followed by 4 octets of zeroes.
Network link
The physical connection between two switches. A network link is
associated with a network interface (or port) of a switch.
Network port
An interface on a switch that attaches to another switch.
Access port
An interface on a switch that attaches to a user endstation.
Port ID
A 10-octet value that uniquely identifies an interface of a
switch. The value consists of the 6-octet base MAC address of the
switch, followed by the 4-octet local port number of the
interface.
Neighboring switches
Two switches attached to a common (network) link.
Call connection
A mapping of user traffic through a switch that correlates the
source and destination address pair specified within the packet to
an inport and outport pair on the switch.
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RFC 2643 Cabletron's SecureFast VLAN Operational Model August 1999
Call connection path
A set of 0 to 7 network links over which user traffic travels
between the source and destination endstations. Call connection
paths are selected from a list of alternate equal cost paths
calculated by the VLS protocol [IDvlsp], and are chosen to load
balance traffic across the fabric.
Ingress switch
The owner switch of the source endstation of a call connection.
That is, the source endstation is attached to one of the local
access ports of the switch.
Egress switch
The owner switch of the destination endstation of a call
connection. That is, the destination endstation is attached to
one of the local access ports of the switch.
Intermediate switches
Any switch along the call connection path on which user traffic
enters and leaves over network links. Note that the following
types of connections have no intermediate switches:
- Call connections between source and destination endstations
that are attached to the same switch -- that is, the ingress
switch is the same as the egress switch. Note also that the
path for this type of connection consists of 0 network links.
- Call connections where the ingress and egress switches are
physical neighbors connected by a single network link. The
path for this type of connection consists of a single network
link.
InterSwitch Message protocol (ISMP)
The protocol used for interswitch communication between SFVLAN
switches.
Undirected messages
Messages that are (potentially) sent to all SFVLAN switches in the
switch fabric -- that is, they are not directed to any particular
switch. ISMP messages with a message type of 5, 7 or 8 are
undirected messages.
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RFC 2643 Cabletron's SecureFast VLAN Operational Model August 1999
Switch flood path
The path used to send undirected messages throughout the switch
fabric. The switch flood path is formed using a spanning tree
algorithm that provides a single path through the switch fabric
that guarantees loop-free delivery to every other SFVLAN switch in
the fabric.
Upstream Neighbor
That switch attached to the inport of the switch flood path --
that is, the switch from which undirected messages are 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.
Downstream Neighbors
Those switches attached to all outports of the switch flood path
except the port on which the undirected message was received.
Note that for each undirected message some number of switches have
no downstream neighbors.
Virtual LAN (VLAN) identifier
A VLAN is a logical grouping of ports and endstations such that
all ports and endstations in the VLAN appear to be on the same
physical (or extended) LAN segment even though they may be
geographically separated.
A VLAN identifier consists of a variable-length string of octets.
The first octet in the string contains the number of octets in the
remainder of the string -- the actual VLAN identifier value. A
VLAN identifier can be from 1 to 16 octets long.
VLAN policy
Each VLAN has an assigned policy value used to determine whether a
particular call connection can be established. SFVLAN recognizes
two policy values: Open and Secure.
2. SFVLAN Overview
Cabletron's SecureFast VLAN (SFVLAN) product implements a distributed
connection-oriented switching protocol that provides fast forwarding
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