Page 190 7750 SR OS Services Guide
For n*64 kbps circuits, the number of octets or DS1/E1 frames to be included in the TDM payload
needs to be configurable in the range 4 to128 DS1/E1 frames in increments of 1 or the payload size
in octets. The default number of frames is shown in the table below with associated packet sizes.
For the number of 64 kbps channels included (N), the following number of frames defaults apply
for no CAS: N=1, 64 frames; 2<=N<= 4, 32 frames; 5<=N<= 15, 16 frames; N>=16, 8 frames.For
CAS circuits, the number of frames can be 24 for DS1 and 16 for E1 which yields a payload size
of N*24 octets for T1 and N*16 octets for E1. For CAS, the signaling portion is an additional
((N+1)/2) bytes where N is the number of channels. The additional signaling bytes are not
included in the TDM payload size, although they are included in the actual packet size shown in
Table 8.
The full ABCD signaling value can be derived before the packet is sent. This occurs for every 24
frames for DS1 ESF and every 16 frames for E1. Note that for DS1 SF, ABAB signaling is
actually sent as SF framing only supports AB signaling every 12 frames.
Table 7: Unstructured Payload Defaults
TDM Circuit Default Payload Size
DS1 192 octets
E1 256 octets
Table 8: Structured Number of Frames Defaults
Num
Timeslots
no CAS DS1 CAS E1 CAS
num-
frames
default
Default
Payload
Minimum
Payload
Pay-
load (24
frames)
Packet
Size
Pay-
load (16
frames)
Packet
Size
1 64644024251617
2 32646448493233
3 32969672744850
4 32 128 128 96 98 64 66
5 16 80 80 120 123 80 83
6 16 96 96 144 147 96 99
7 16 112 112 168 172 112 116
8 16 128 128 192 196 128 132
9 16 144 144 216 221 144 149
10 16 160 160 240 245 160 165
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