HP 600 Series, Services And Applications

Page: 82 / 316

Track 2. The Specifically Routed Frame Back to Node 1
This section tracks specifically routed frames (SRFs) sent back from H2 to
H1. See figure 20.
If there is only a single bridge ID (for an HP router) in the RIF, then the
bridge simply transmits the frame to the outgoing circuit group without
making any modification. This is only true when the frame only has to
traverse a single bridge between the source and destination end nodes.
Because of the simplicity of this case, it is not described in any further detail
here.
On the other hand, if there are multiple bridge IDs (for an HP router) in the
RIF, the RIF is manipulated differently by the bridges in the first, middle, and
last positions—which are C, B, and A, in that order, in the direction taken by
this frame.
Internal LAN ID = 100 Internal LAN ID = 101 Internal LAN ID = 102
Group LAN ID = FFF Group LAN ID = FFF Group LAN ID = FFF
Bridge ID = A Bridge ID = A Bridge ID = A
Figure 20. Tracking a Specifically Routed Frame Back to Node 1
First of several bridges receiving the SRF: The frame received by
bridge C from ring 4 has not traversed any other bridges yet. (But there
are multiple bridge IDs in the RIF, so it will.) This bridge does the follow-
ing to the RIF before transmitting the frame toward ring 3. (Figure 21
illustrates the RIF in the frame.)
Changes the destination node’s station address at the beginning of
the frame to an HP group address. This address appears as
C000A2FFFFF
x , where x is the bridge ID of the next bridge specified
by the RIF.
Removes its own internal LAN ID.
Inserts the group LAN ID before the last incoming LAN ID/bridge ID
listed in the RIF. (See figure 21.) Eventually, the group LAN ID will
be replaced with the internal LAN ID of the last bridge along the
frame’s path.
Copies the destination node’s station address into the data portion of
the frame.
router A router B router C
H1
H2
1
2
4
3
Bridging Service
Source-Routing Bridging
2-30