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Appendix E - Defining Service Profiles for Generic VoIP Gateways
E.5
1 POTS Advanced VoIP G.711 Service
Pr
ofile
E.5.1
Se
rvice Characteristics
G.729 codec, 20msec sample interval
1 POTS
T.38 Fax
DSCP priority marking behind the SU is used, with the follow
63: RTP traffic
26: RTCP and VoIP traffic
0: Data traffic
Single media stre
E.5.
2
Voice RTP BW Calculation
The r
equired bandwidt
160
bytes of voice payload is:
Tot
al packet size (bytes) = (Ethernet of 18 bytes) + (IP/UDP/RTP hea
byt
es) + (voice payload of 160 bytes) = 218 bytes
Tot
al packet size (bits) = (218 bytes) * 8 bits per byte = 1744 bits
PPS = (64 Kbps codec bit rate) / (1280 bits) = 50 pps
Not
e: 1280 bits = 160 bytes (voice payload) * 8 bits per byte
Ban
dwidth per call = total packet size (1744 bits) * 50 pps = 87.2 Kbp
E.5.
3
Vo
ice RTCP BW Calculation
RTC
P BW is 10% of RTP: 10 % of 87.2 Kbps is 8.72 Kbps.
E.5.4
T.38 14,400 Kbps Fax RTP BW Calculation
The
required bandwidth with a 20 msec sample interval is as follows:
Tota
l packet size (bytes) = (Ethernet of 18
bytes) + (voice payload of 36 bytes) = 94 bytes
Total packet size (bits) = (94 bytes) * 8 bits per byte = 752 bits
276
am to support Call-Waiting
h for a G.711 call (64 Kbps codec bit rate) with RTP and
bytes) + (IP/UDP/RTP header of 40
ing values:
der of 40
s
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