Browse Prior Art Database

Algorithm for Multiport Source Routing to Transparent Bridging LAN Bridge

IP.com Disclosure Number: IPCOM000116513D
Original Publication Date: 1995-Sep-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 81K

Publishing Venue

IBM

Related People

Bowen, RK: AUTHOR [+2]

Abstract

A method for supporting the spanning tree protocol for multiport SR-TB bridges is disclosed. Source routing bridge port forwarding states for All Routes Explorer (ARE) and Spanning Tree Explorer (STE) frames are determined by the IEEE 802.1d spanning tree protocol.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 53% of the total text.

Algorithm for Multiport Source Routing to Transparent Bridging LAN
Bridge

      A method for supporting the spanning tree protocol for
multiport SR-TB bridges is disclosed.  Source routing bridge port
forwarding states for All Routes Explorer (ARE) and Spanning Tree
Explorer (STE) frames are determined by the IEEE 802.1d spanning tree
protocol.

      The multiport Source Routing to Transparent Bridging (SR-TB)
spanning tree protocol implementation is based on the following
principles:
  o  The network is divided into two types of domains:
     -  A source routing bridged domain in which source routing
         bridges transmit Bridge Protocol Data Unit (BPDU) frames
         using the All Bridges Functional MAC Address, and SR-TB
         bridges transmit BPDUs using the method of the IBM*
         8209/8229.
     -  A transparently bridged domain in which bridges participate
         only in the IEEE 802.1d spanning tree algorithm.
  o  On source-routing ports, discard source routing bridge BPDUs;
      receive and transmit encapsulated 802.1d BPDUs as is done on
the
      token-ring port of an 8209 in SR-TB mode.
  o  On transparent bridging ports, receive and process IEEE 802.1d
      BPDUs as is done by the Ethernet port of an IBM 8209.
  o  When a source-routing port is not in Forwarding state, disallow
      the forwarding of both single-route and all-routes explorer
      frames through that port.

      As a result of adhering to these principles, the bridge
participates in the IEEE 802.1d algorithm on all ports, and views
each source routing domain as a single LAN segment.  Duplicate frames
are prevented in the transparent domain by disallowing forwarding of
all-routes explorer frames through ports in Forwarding state.

      In order to facilitate an efficient forwarding algorithm, a
source routing segment number is assigned to each port attached to
the transparent bridging domain.  As a result, frames received from a
Source-Routing (SR) port are forwarded directly to the proper
Transparent Bridging (TB) port.  No lookup of a frame's destination
address is necessary for frames forwarded from the source routing
domain.

      In detail, the forwarding algorithm for frames received on
source-routing ports is as follows:
  If the frame is addressed to t...