User manual

4200 User Manual Edgewater Networks, Inc.
Version 2.2 32
Determining the maximum number of concurrent calls
The maximum number of concurrent calls that can be supported by the WAN access
link is calculated using the following formula:
Max calls = (Maximum WAN upstream bandwidth * .85)/VoIP codec rate
where,
Maximum WAN upstream bandwidth = value entered in step D above (in Kbps)
VoIP codec rate = 85.6Kbps for G.711 voice devices or 29.6Kbps for G.729 voice
devices.
The maximum WAN upstream bandwidth is multiplied by .85 in the formula above to
reduce the total bandwidth available for voice calls by 15%. This reduction is
necessary because the 4200 automatically reserves 15% of the total WAN bandwidth
for low priority data traffic so that it is not starved completely. Starving data traffic
completely would increase the number of retry attempts and exacerbate congestion
on the link during periods of peak usage.
Examples
The maximum number of G.711 voice calls supported by a T1 (1.544 Kbps) WAN is
calculated as follows:
(1544*.85)/85.6 = 15.3 or 15 total voice calls.
The maximum number of G.711 voice calls supported by a 768Kbps SDSL WAN is
calculated as follows:
(768*.85)/85.6 = 7.6 or 7 total voice calls
The maximum number of G.711 voice calls supported by an ADSL WAN with 768Kbps
downstream WAN bandwidth and 256Kbps upstream WAN bandwidth is calculated as
follows:
(256*.85)/85.6 = 2.5 or 2 total voice calls
The maximum number of G.729 voice calls supported by an ADSL WAN with 768Kbps
downstream WAN bandwidth and 256Kbps upstream WAN bandwidth is calculated as
follows:
(256*.85)/29.6 = 7.4 or 7 total voice calls
After determining the maximum number of voice calls CAC is enabled as follows:
F. Select the Enable Call Admission Control checkbox.
G. Enter Maximum number of calls allowed as calculated above.
H. Press Submit.