rfc2643.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

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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          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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      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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      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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   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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   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
   of data packets at the MAC layer.





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