Nortel VoIP Gateway, Configuration Manual

Page: 161 / 220

Additional feature configuration 161
Norstar VoIP Gateway Configuration Guide
Each site supports four VoIP ports. Assume the codex is G.729 Annex B, 20 ms payload.
Assuming full-duplex links, peak bandwidths per call are between 24.8 kbit/s and 27.6 kbit/s peak
transmission or approximately 28 kbit/s. This is shown in the following figure, taken from the
table under
“Bandwidth requirements on full duplex links” on page 157 .
Figure 47 Network loading bandwidth
Route R1-R2 needs to support four VoIP Calls. R4-R5 needs to support eight VoIP calls. The
incremental peak bandwidth for VoIP traffic is therefore:
R1-R2 peak VoIP Load = 4(28 kbit/s) = 112kbit/s
R4-R5 peak VoIP Load = 8(28kbit/s) = 224kbit/s
With VoIP Gateway bandwidth requirements and
Traceroute
measurements, the R4-R5 link is
expected to support the Santa Clara/Richardson, Santa Clara/Tokyo and the Ottawa/Tokyo traffic
flows. The other IP telephony traffic flows do not route over R4-R5. A peak of eight calls can be
made over R4-R5 for the four IP telephony ports per site. R4-R5 needs to support the incremental
bandwidth of 8 x 12 = 96 kbit/s.
To complete this exercise, the traffic flow from every site pair needs to be summed to calculate the
load on each route and loaded to the link.
Codec
Type
Payload
Size
PPP B/W FR B/W
No SP
Silence
Suppression
No SP
Silence
Suppression
ms peak
(kbit/s)
peak
(kbit/s)
Avg
(kbit/s)
peak
(kbit/s)
peak
(kbit/s)
Avg
(kbit/s)
G.729
(8 kb/s)
10 41.6 20.8 47.2 23.6
20 24.8 12.4 27.6 13.8
30 19.2 9.6 21.1 10.6