66 Planning and Installation Guide ShoreTel 14
Network Requirements and Preparation Computing Admission Control Bandwidth
Computing Admission Control Bandwidth
This section discusses how to compute the admission control bandwidth for the site you are
configuring on the Site edit page—that is, the appropriate value for the Admission Control
Bandwidth parameter. If you want to determine the admission control bandwidth for your site and the
information is not available in this section, use one of the following formulas:
To determine the admission control bandwidth:
Bandwidth – (# of calls) x (bandwidth/call)
To determine the number of calls supported with a specific admission control bandwidth value:
# of calls – (admission control bandwidth) / (bandwidth/call)
ShoreTel automatically negotiates the proper voice encoder at call setup. For calls between sites, the
call control software requests the voice encoder based on what is selected for inter-site voice encoding
as defined on the Call Control Options edit page. The call control software will then make sure both
endpoints on the call can support the requested voice encoder.
For instance, for G.729a voice encoding to be used between two sites, the inter-site voice encoding
must be set to G.729a and the ShoreTel voice switches at each end of the call must be G.729a-
WAN Bandwidth per Call (Full Duplex) without cRTP
Table 21 lists the bandwidth, including IP overhead, that is used for each voice call between sites when
RTP Header Compression (cRTP) is not used. The bandwidth depends on the voice encoding used.
For example:
If you want to support 10 calls between this site and all other sites, and G.729a voice encoding
is used, set the admission control bandwidth to 260 Kbps. Before you enter this value, make
sure the bandwidth is available at this site.
If you set your admission control bandwidth to 768 Kbps and G.729a voice encoding is used,
you can support up to 29 calls between this site and all other sites.
ShoreTel recommends that you configure the admission control bandwidth to be less than the
bandwidth of the actual WAN link. This provides sufficient bandwidth for call control signaling and other
data traffic.
Table 21: Bandwidth Without cRTP
Bandwidth in
Kbps per Number
of Calls
Linear G. 7 11 ADPCM G.729a
1 146 82 52 26
2 292 170 104 52
3 438 255 156 78
4 584 340 208 104
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