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Administrator’s Guide for Cisco IPVC 3521 BRI Gateway, Cisco IPVC 3526 PRI Gateway, and Cisco IPVC 3540 PRI Gateway
OL-7995-01
Chapter 1 Overview of the Cisco IPVC 3500 Series Gateway
About Cisco IPVC 3500 Series Gateway Functionality
Note
Enabling ISDN-to-IP DTMF detection in the Cisco IPVC 3526 PRI Gateway for video calls reduces the
number of supported calls by half.
About Cisco IPVC 3500 Series 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
About Peer-to-Peer Connectivity
The Cisco IPVC 3500 Series Gateway supports the following types of connectivity to the IP network
•
Through a gatekeeper
•
Directly to a peer device such as Cisco CallManager without the need for a gatekeeper.
Table 1-10
Cisco IPVC 3526 PRI Gateway and Cisco IPVC 3540 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
Maximum Number
of Calls Using 2 x E1
PRI Lines
Maximum Number
of Calls Using 2 x T1
PRI Lines
voice (64 Kbps)
30
23
60
46
2B video (128
Kbps)
15
11
30
23
6B video (384
Kbps)
5
3
10
7
12B video (768
Kbps)
2
1
5
3
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