HP 200 Series Services And Applications page 74

Bridging Service
Source-Routing Bridging
5 – Identifies the incoming LAN segment
1 – Identifies the source-routing bridge
Figure 12. Sample Routing Designators
When a source-routed frame reaches its destination, its MAC header
contains the route (identified by a sequence of routing designators) that the
frame traversed to get there.
For example, figure 13 depicts a multi-ring network with three SRT bridging
routers (A, B, and C), and one transparent bridge (T). Node H1 wants to use
source routing to exchange frames with node H2. In order to initiate route
discovery, H1 transmits an ARE frame addressed to H2. As the ARE frame
crosses the network, every source-routing bridge that it passes through
inserts routing designators in the frame's MAC header. If the frame crosses a
transparent bridge, the bridge simply forwards the frame on the basis of its
destination station address.
2-22
5-1
Incoming Path
Internal Path
A– Identifies the internal virtual LAN
1 – Identifies the source-routing bridge
8 – Identifies the outgoing LAN segment
0 – The bridge always sets the final bridge
ID in the routing designator to 0; this
bridge ID is updated by the next source-
routing bridge to receive the frame
8-0
A-1
Outgoing Path