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Table 1-3
PRI Gateway Call Handling Capacity (continued)
Call Type
Maximum Number
of Calls Using 1 x
E1 PRI Line
12B video (768
2
Kbps)
A
G
BOUT
ATEWAY
C
B
ALL
ANDWIDTH
O
VERHEAD
R
ESOURCE
A
LLOCATION ACROSS
E1/T1 L
INES
Maximum Number
of Calls Using 1 X
T1 PRI Line
1
Enabling ISDN-to-IP DTMF detection in the PRI Gateway for video calls
Note
reduces the number of supported calls by half.
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.
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
About SCOPIA Gateway Functionality
Maximum Number
of Calls Using 2 x
E1 PRI Lines
5
Maximum Number
of Calls Using 2 x
T1 PRI Lines
3
Functionality
15
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