1-20 Cisco BPX 8600 Series Reference
Switch Software Description
• Alternate Routing—the system software automatically reroutes a failed connection.
The system software uses the following criteria when it establishes an automatic route for a
connection:
• Selects the most direct route between two nodes.
• Selects unloaded lines that can handle the increased traffic of additional connections.
• Takes into consideration user-configured connection restrictions (for example whether or not the
connection is restricted to terrestrial lines or can include satellite hops or routes configured for
route diversity).
When a node reroutes a connection, it uses these criteria and also looks at the priority that has been
assigned and any user-configured routing restrictions. The node analyzes trunk loading to determine
the number of cells or packets the network can successfully deliver. Within these loading limits, the
node can calculate the maximum combination allowed on a network trunk of each type of
connection: synchronous data, ATM traffic, frame relay data, multi-media data, voice, and
compressed voice.
Network-wide T3, E3, OC3, or OC12 connections are supported between BPX switches terminating
ATM user devices on the BPX switch UNI ports. These connections are routed using the virtual path
and/or virtual circuit addressing fields in the ATM cell header.
Narrowband connections can be routed over high-speed ATM backbone networks built on BPX
broadband switches. FastPacket addresses are translated into ATM cell addresses that are then used
to route the connections between BPX switches, and to ATM networks with mixed vendor ATM
switches. Routing algorithms select broadband links only, avoiding narrowband nodes that could
create a choke point.
Connection Routing Groups
The re-routing mechanism is enhanced so that connections are presorted in order of cell loading
when they are added. Re-routing takes place by rerouting the group containing the connections with
the largest cell loadings first on down to the last group which contains the connections with the
smallest cell loadings. These groups are referred to as routing groups. Each routing group contains
connections with loading in a particular range,
There are three configurable parameters for configuring the rerouting groups,
— total number of rerouting groups
— starting load size of first group
— load size range of each group
The three routing group parameters are configured with the cnfcmparm command.
For example, there might be 10 groups, with the starting load size of the first group at 50, and the
incremental load size of each succeeding group being 10 cells. Then group 0 would contain all
connections requiring 0-59 cell load units, group 1 would contain all connections requiring from
60-69 cell load units, on up through group 9 which would contain all connections requiring 140
or more cell load units.
