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Factors that effect the real-time capacity 113
ATTENTION
IMPORTANT
Voice packets must have priority over data packets.
When the WAN route prior itizes voice traffic over data traffic, the route bandwidth
can be engineered to 90% loading level; otherwise, a WAN route with bandwidth
of 1.536 Mbit/s or more can only be loaded up to 80%. A smaller WAN pipe (64
kbit/s) is recommended to a loading of 50%.
In Table 17 "Silence Suppression disabled TLAN Ethernet and WAN IP
bandwidth usage per IP Trunk 3.01 (and later) " (page 113), the first WAN
bandwidth is without Frame Relay or ATM overhead.
The Frame Relay overhead is 8 bytes (over IP packet).
The LLC SNAP (Link Layer Control SubNetwork Attachment Point) and
AAL5 overhead for ATM is 16 bytes (over IP packet).
IP packet size over 53 bytes requires two ATM cells, over 106 bytes requires
three ATM cells, and so on. Within the same number of cells, the bandwidth
requirements are the same for packets with different sizes.
TM 3.1 input for fax is in bytes, ranging from 20 to 48;
30 bytes is the default.This differs from voice applications where payload
size is the input.
Table 17
Silence Suppression disabled TLAN Ethernet and WAN IP bandwidth usage per IP Trunk 3.01
(and later) port
Codec
type
Codec
Multi -
frame
duration
(ms)
See Not
e
8.
Voice
/fax
paylo
ad
size
(byte
s)
IP
head
er
size
(byte
s)
Ether
net
head
er
size
(byte
s)
Full-d
uplex
Ether
net
Band
width
(bps)
PPP
WAN
Band
width
(bps)
See
Note
9.
Frame
Relay
WAN
bandw
idth
(bps)
ATM
WAN
bandw
idth
(bps)
G.711
10 80 40 26 116,8
00
101,6
00
102,4
00
127,200
(64 kbit/s)
voice
20 160 40 26 90,400 82,800 83,200
106,000
30 240 40 26 81,600 76,533 76,800 84,800
Nortel Communication Server 1000
IP Trunk Fundamentals
NN43001-563 01.01 Standard
Release 5.0 30 May 2007
Copyright © 2007, Nortel Networks
.