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IP Telephony and QSIG Over IP
Private Networking Over Internet Protocol
Strata CTX I&M 06/04 9-41
IP Telephony and QSIG
Over IP
Strata Net QSIG Over IP and IPT Bandwidth Requirements
The bandwidth requirements for Strata Net QSIG over IP is the same as those for IP telephones.
Refer to Table 9-1 on page 9-5 to estimate the quality of service (Excellent, Good, Fair, and Poor)
provided by CTX IP QSIG channels depending heavily on the LAN parameters.
When sharing voice and data on the same network segment, the data will cause some jitter in voice
communications, especially on slower segments. Table 9-11 shows calculations of the amount of
jitter assuming a worst case data packet size of 1500 bytes (Maximum Transmission Unit (MTU) =
1500) based on a segment’s bandwidth. This also requires that the routers connecting the segment
through the WAN support Diffserv.
Note A router that doesn’t support Diffserv may stack multiple data packets together increasing
the jitter perhaps indefinately. And the voice quality will be indeterminate.
Class definition categories are shown in Table 9-12.
Table 9-13 shows the amount of bandwidth required for setting up and tearing down calls
independent of the amount of voice traffic.
Table 9-11 QSIG over IP Jitter on Mixed Voice and Data WAN
No. of
B-Channels
of WAN
Bandwidth
(kbps)
Time to
transmit max.
MTU (ms)
Expected
Jitter (ms)
Class
2 128 93.75 100 Poor
4 256 46.88 50 Fair
6 384 23.44 30 Fair
8 512 15.63 20 Good
24 1536 1.00 1 Excellent
Table 9-12 QSIG over IPClass Definitions
Class Delay (ms) Jitter (ms)
Excellent < 20 < 10
Good < 50 < 20
Fair < 100 < 50
Poor < 200 < 100
Table 9-13 QSIG over IP Bandwidth
Required for Call Setup
Traffic Rate
(BHCA
1
)
1. BHC = Busy Hour Call Attempts
Required
Bandwidth
1000 6
2000 12
4000 23
6000 36