Algorithm for Multiport Source Routing to Transparent Bridging LAN Bridge
Original Publication Date: 1995-Sep-01
Included in the Prior Art Database: 2005-Mar-30
Bowen, RK: AUTHOR [+2]
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.
Algorithm for Multiport Source Routing to Transparent
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
Source Routing to Transparent Bridging (SR-TB)
spanning tree protocol implementation is based on the following
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*
- 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
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
the forwarding algorithm for frames received on
source-routing ports is as follows:
If the frame is addressed to t...