1-11
Installation and Upgrade Guide for CiscoUnified Videoconferencing 3522BRI Gateway and 3527 PRI Gateway Release5.5
OL-14910-01
Chapter1 Functionality About CiscoUnified Videoconferencing 3500 Gateway Functionality
About PRI Gateway Call Handling Capacity
Tabl e 1-3 lists the maximum call handling capacity of the PRI gateway for different types of calls.
Note Enabling ISDN-to-IP DTMF detection in the PR I gat eway for v ide o ca lls reduc es the num be r of
supported calls by half.
About BRI Gateway Call handling Capacity
Tabl e 1-4 lists the maximum call ha ndli ng cap acit y of t he BRI gat eway for four BR I lines, ei ght
voice-only calls, or eight video calls, or any combination of the two.
About Gateway Call Bandwidth Overhead
According to the H.320 standard, the available bandwidth allocated to a call at any given bit rate will
always be slightly less than the stated maximum for the following reasons:
•All stated maximum call bandwidths include p rovisio n f or cont ro l, au dio, vide o, a nd da ta tra ffic.
•Video traffic on the ISDN side contains additional bits for error correction purposes which also
consume bandwidth. Video traffic on the IP side does not include this addi tiona l l o ad.
•Opening an audio channel further reduces the bandwidth available to the video traffic.
For example, a call at 384 Kbps actually has only 363 Kbps available to it. Contro l and error correction
account for the remaining 21 Kbps.
Table1-3 PRI Gateway Call Handling Capacity
Call Type Maximum Number of
Calls Using 1 x E1 PRI
Line
Maximum Number of
Calls Using 1 X T1 PRI
Line
voice (64 Kbps) 30 23
2B video (128 Kbps) 15 11
6B video (384 Kbps) 5 3
12B video (768 Kbps) 2 1
Table1-4 BRI Gateway Call Handling Capacity
Number of Calls Capacity
1 384 Kbps+ or 412 Kbps
2 256 Kbps
4 128 Kbps
864 Kbps