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Installation and Upgrade Guide for Cisco Unified Videoconferencing 3522 BRI Gateway and 3527 PRI Gateway Release 5.5
OL-14910-01
Chapter 1 Functionality
About Cisco Unified Videoconferencing 3500 Gateway Functionality
About PRI Gateway Call Handling Capacity
Table 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 PRI gateway for video calls reduces the number of
supported calls by half.
About BRI Gateway Call handling Capacity
Table 1-4 lists the maximum call handling capacity of the BRI gateway for four BRI lines, eight
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 provision for control, audio, video, and data traffic.
• 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 additional load.
• 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. Control and error correction
account for the remaining 21 Kbps.
Table 1-3 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
Table 1-4 BRI Gateway Call Handling Capacity
Number of Calls Capacity
1 384 Kbps+ or 412 Kbps
2 256 Kbps
4 128 Kbps
864 Kbps