Specifications

Network Requirements and Preparation
9 – 30 ShoreTel, Inc.
WAN Bandwidth per Call (Full Duplex) with cRTP
Some routers support a feature called RTP Header Compression (cRTP) that
significantly reduces the amount of IP overhead associated with voice over IP. Table 9-
15 defines the bandwidth used between sites when cRTP is being 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 120 Kbps. Before
you enter this value, make sure the bandwidth is available at this site.
• If you set your admission control bandwidth to 256 Kbps and G.729a voice
encoding is used, you can support up to 21 calls between this site and all other
sites.
NOTE 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.
21 3066 1785 1092 546
22 3212 1870 1144 572
23 3358 1955 1196 598
24 3504 2040 1248 624
25 3650 2125 1300 650
26 3796 2210 1352 676
27 3942 2295 1404 702
28 4088 2380 1456 728
29 4234 2465 1508 754
30 4380 2550 1560 780
Table 9-15 Bandwidth with cRTP
Bandwidth in
Kbps per
Number of Calls
Linear G.711 ADPCM G.729a
1 132 68 38 12
22641367624
3 396 204 114 36
4 528 272 152 48
5 660 340 190 60
6 792 408 228 72
7 924 476 266 84
8 1056 544 304 96
9 1188 612 342 108
10 1320 680 380 120
11 1452 748 418 132
12 1584 816 456 144
13 1716 884 494 156
Table 9-14 Bandwidth Without cRTP
Bandwidth in
Kbps per
Number of Calls
Linear G.711 ADPCM G.729a