User guide

Functionality 15
About SCOPIA Gateway Functionality
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
O
VERHEAD
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.
RESOURCE
A
LLOCATION ACROSS
E1/T1 LINES
The Gateway can allocate bandwidth resources to calls across separate E1 or T1
connections to maximize bandwidth capacity in cases where there is not enough
capacity for a call on a single E1 or T1 connection, but where sufficient capacity
does exist when remaining capacity on both E1/T1 lines is combined.
For example, a Gateway using two T1 lines can support three 6B calls on each
T1 line, with 320 Kbps spare capacity per line:
 Each T1 line provides 23 B channels.
 Each B channel supports 64 Kbps
 Each T1 line supports 23 x 64 = 1472 Kbps
 Each 6B call requires 6 x 64 = 384 Kbps
 Each T1 line supports 1472/384 = 3 6B calls + 320 Kbps spare
12B video (768
Kbps)
2153
Table 1-3 PRI Gateway Call Handling Capacity (continued)
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