Cisco 545 Serial - Manual (Page 19)

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Installation and Upgrade Guide for Cisco Unified Videoconferencing 3545 PRI Gateway and 3545 Serial Gateway Release 5.5
OL-14912-01
Chapter 1 Functionality
About Cisco Unified Videoconferencing 3545 Gateway Functionality
About Cisco Unified Videoconferencing 3545 Gateway
Functionality
This section discusses the following topics:
• About PRI Gateway Call Handling Capacity, page 1-13
• About Gateway Call Bandwidth Overhead, page 1-13
• About Peer-to-Peer Connectivity, page 1-14
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 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 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