Nortel Networks Remote Gateway 50 User Manual
Page 55
Bandwidth Management
Page 55 of 258
Main Office Configuration for Survivable Remote Gateway 50
Configuration Guide
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For tandem calls, the Master/Slave information is not relevant. The
Master/Slave information is designed for use between two nodes only,
not between three or more nodes. It makes the codec selection for tandem
calls more complex and inefficient.
To solve the issues, another codec selection algorithm, not based on the
unpredictable Master/Slave information, is needed. Since any change to the
Master/Slave algorithm implies a change to the H.323 standard, the new
codec algorithm is used for Virtual Trunk calls between Nortel equipment.
‘Best Bandwidth’ codec selection algorithm
The “Best Bandwidth” codec selection algorithm solves the issues caused by
the H.323 Master/Slave algorithm. The “Best Bandwidth” algorithm selects
one common codec based on two codec lists. Every time the selection is done
with the same two lists, the selected codec is the same.
The “Best Bandwidth” codec decision is based on the codec type only, it does
not take into account the fact that some codecs, while generally using less
bandwidth, can consume more bandwidth than others at certain payload sizes.
Algorithm details
The selected codec is the type considered as the best bandwidth codec type.
To know whether one codec type has better bandwidth than another, see the
rule as summarized in Table 4 on
.