Installation guide

68 Planning and Installation Guide ShoreTel 14.2

Network Requirements and Preparation WAN Bandwidth per Call (Full Duplex) with cRTP

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 18 on page 68 lists the bandwidth used

between sites when cRTP is 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 the 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.

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 18: 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

Table 17: Bandwidth Without cRTP (Continued)

Bandwidth in

Kbps per Number

of Calls

Linear G.711 ADPCM G.729a