Specifications

Engineering Guidelines
188
Trunking gateway working example
In terms of considering network bandwidth, it should be based on the 120 channels and where
they are being connected. Also consider the maximum number of compression channels
(G.729a); they are limited to 64 within a single unit. Further IP trunks use standard
non-compressed G.711 channels. Thus, in the example of toll-bypass, it is likely that trunks will
go via the IP WAN. In this case, the connection bandwidth requirements will be 11.0 Mbps. For
a fully G.711 connection (no compression), then 16.0 Mbps is needed. Note that Ethernet and
WAN links should not be fully utilized, in order to allow maintenance traffic to flow. Typically, a
link is loaded to 70% on a WAN link and 80% on a full duplex LAN.
IP networking routes and compression
Compression can be enabled in IP networking routes between 3300 ICP units if the end devices
are capable of this operation. For more details see “Compression zones” on page 188.
Compression zones
This section briefly describes compression zones, IP trunk routes, and network issues to
consider when planning the location of different devices.
Table 59: Trunk Gateway Bandwidth Calculation with 64 Channels Compression
Addition (mixed compressed and non-compressed) Bandwidth
64 channels of compression (40.8k each) 2.611 Mbps
56 channels of non-compression (120-64 = 56, 96.8k each) 5.402 Mbps
Signalling overhead 10% (on total of voice) 0.801 Mbps (10% of 5.402+2.611)
TOTAL (payload) 8.835 Mbps
TOTAL (connections with LAN loading 80%) 11.0 Mbps
Table 60: Trunk Gateway Bandwidth Calculation with 120 Channels Non-compression
Addition (non-compressed) Bandwidth
120 channels of non-compression (100k each) 11.62 Mbps
Signalling overhead 10% 1.16 Mbps (10% of 11.62)
TOTAL (payload) 12.78 Mbps
TOTAL (connections with LAN loading) 16.0 Mbps