Configuring PNNI Path Selection
IBM's PNNI supports three types of path selection, for the following classes of traffic:
Constant Bit Rate (CBR), real time Variable Bit Rate (rt VBR), and non-real time Available Bit Rate (nrt
VBR)
Available Bit Rate (ABR)
Unspecified Bit Rate (UBR)
Constant Bit Rate and Variable Bit Rate (CBR, rt VBR, and nrt VBR)
Routing is done on demand, corresponding to the demand appearing when processing a call from the
network (this is automatic and requires no configuration action from the ATM console):
Calls not satisfying the Generic Call Admission Control (GCAC) are pruned.
A shortest path is computed. This is the path with the smallest sum of adminisitrative weights. If more
than one path is found with the same sum of administrative weights, the path with the highest
available bandwidth is chosen.
Available Bit Rate
IBM's PNNI Path Selection supports Available Bit Rate (ABR) calls in two ways, precomputed and
on-demand:
Paths are precomputed and specific route is obtained via table look-ups, resulting in fast connection
setup. The path is computed according to the "widest path" criterion.
Paths are computed on-demand, resulting in slower connection setups, but with more optimization for
the individual routes. The path is computed according to the "shortest path" criterion, based on
administrative weights.
The default configured setting is for paths to be precomputed, and can be changed to on-demand by
entering the following command:
à
ð
8265ATM
>
set pnni path_selection abr: on_demand_path
á
ñ
The setting can be changed back to precomputed by entering the following command:
à
ð
8265ATM
>
set pnni path_selection abr: precomputed_path
á
ñ
66
IBM 8265: User's Guide
Summary of Contents for 8265 Nways ATM Switch
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Page 17: ...Part 1 Configuring Your ATM Network Copyright IBM Corp 1994 1998 1...
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