Automatic Retry; Alternate Routes - 3Com CoreBuilder 9000 User Manual

Automatic Retry

Alternate Routes

After receiving the RELEASE message, the source CoreBuilder 9000 ATM
Enterprise Switch again attempts to establish a virtual channel, but this
time via an alternate path. The switch determines the alternate path
automatically with the routing table that was established during the first
connection attempt. The routing table holds all the connection
alternatives. The CoreBuilder 9000 ATM Enterprise Switch remembers
which connection was used in the failed attempt and chooses a different
connection the second time, resulting in a new and different path to the
destination.
The availability of alternate paths for connections depends on the
addressing scheme that was used in setting up the network. Alternate
connections need to have the same match type. (For more information,
see "Alternate Routes" on page 345.)
When you plan your network according to the hierarchical addressing
scheme, you must carefully provide alternate, redundant routes between
nodes. Failure to do so will result in infinite loops. To assist you, follow
the rules presented in "Rules for Creating Alternate Routes".
For example, in the network of Figure 15, there are three ways (paths) to
reach node B1 from node A through the ATM network: Link-1 and link-2
are connected directly to node B1, and link-3 is connected through node
B.
Figure 15 Alternate Routes in an ATM Network
A*
1
2
3
E-IISP Hierarchic Routing Algorithm
ATM NETWORK
B*
345
B1*
1
2
3