VLL Services
7705 SAR OS Services Guide Page 149
Structured DS1/E1 CES without CAS
Structured CES without CAS is configured by choosing cesopsn as the vc-type when
creating a Cpipe service. For n × 64 kb/s structured circuit emulation operation, the framing
parameter of the port must be set to a framed setting (such as ESF for DS1). Each channel
group contains n DS0s (timeslots), where n is between 1 and 24 timeslots for DS1 and
between 1 and 31 timeslots for E1.
The packet payload size is configurable (in octets) and must be an integer multiple of the
number of timeslots in the channel group. The minimum payload packet size is 2 octets
(based on two frames per packet and one timeslot per frame). See Table 19 for default and
minimum payload size values. The maximum payload packet size is 1514 octets.
Each DS1 or E1 frame contributes a number of octets to the packet payload. That number is
equal to the number of timeslots configured in the channel group. Thus, a channel group
with four timeslots contributes 4 octets to the payload. The timeslots do not need to be
contiguous.
Note that a smaller packet size results in a lower packetization delay; however, it increases
the packet overhead (when expressed as a percentage of the traffic).
Calculation of Payload Size
The payload size (S), in octets, can be calculated using the following formula:
S = N x F
where:
N = the number of octets (timeslots) collected per received frame (DS1 or E1)
F = the number of received frames (DS1 or E1) that are accumulated in each CESoPSN
packet
For example, assume the packet collects 16 frames (F) and the channel group contains
4 octets (timeslots) (N). Then the packet payload size (S) is:
S = 4 octets/frame x 16 frames
= 64 octets
Table 18: Unstructured Payload Defaults
Circuit Payload Size
(Octets)
Packetization Delay (ms)
DS1 192 1.00
E1 256 1.00
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