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Resource sizing
Issue 6 January 2008 223
In Table 45, the number of simultaneous media streams for “P001” represents the 99.9th
percentile for the number of simultaneous streams, as determined by applying the standard
infinite-server queueing model.
To this point, all the discussion regarding bandwidth relates only to bearer traffic (media
streams). Network packet traffic that is related to signaling is very different from the bearer
traffic because it tends to occur in bursts. For example, while the bearer traffic that is associated
with a particular call tends to involve a constant, steady stream of packets throughout the
duration of that call, the signaling traffic for that same call tends to occur in bursts during call
setup and teardown.
The bandwidth that is required for signaling is generally negligible in comparison to the
bandwidth that is required for bearer traffic. However, since Avaya products use Separation of
Bearer and Signaling (SBS), the bearer traffic and signaling traffic use distinct paths. Therefore,
signaling bandwidth must be given its due consideration, despite the fact that it is negligible in
comparison to bearer bandwidth.
Signaling traffic is more prone to bursts than bearer traffic because the former consists of
messages that are associated with call set-ups and tear-downs, as opposed to traffic that is
uniformly distributed throughout entire call durations. However, the “burst” effect is somewhat
assuaged for larger call volumes. Although the precise bandwidth requirement for a given
configuration depends on the nature of the endpoints involved, a reasonable approach is to
allocate an overhead of 50 bits per second (bps) for each IP endpoint in the network, as well as
the following (as applicable) for every 1000 calls:
● 11 kbps for messaging between the S8700-series Server and an IPSI circuit pack on a
G650 Media Gateway
● 8 kbps for the H.248 link between a C-LAN circuit pack and a G700 or G350 Media
Gateway
Note:
Note: The 11 kbps and 8 kbps associated with 1000 calls should not be amortized to
produce estimates for systems with very light traffic. For example, 11 bits per
second and 8 bits per second will not support an individual call.
Table 45: IP WAN bandwidth requirements in each direction, for Example 8: WAN
bandwidth
Requirement Between
sites 1 and 2
Between
sites 1 and 3
Between
sites 2 and 3
Simultaneous media streams for “P001” 39 20 10
LAN bandwidth (kbps) 484 248 124