Specifications

Chapter 1 Introduction Installation and Operation Manual
1-24 Functional Description MPW-1 MP-4100 Ver. 2.0
 At 48 TDM bytes per frame: 5.5 msec when signaling is transferred,
and 5.9 msec without signaling
 At 384 TDM bytes per frame: 44 msec when signaling is transferred,
and 47 msec without signaling
Therefore, for pseudowires with a few timeslots, it is recommended to
use the minimum payload size (48 bytes).
In general, the TDMoPSN packetization delay is calculated with the
following formula:
Packetization delay (ms) =
TS
0.125N 47 ××
where N is the selected multiplier, 1 to 30:
N =
48
ebytes/framTDM
and TS is the number of assigned timeslots.
Therefore, before considering any other delays encountered along the
end-to-end transmission path, the round-trip (or echo) delay for the
voice channel example presented above is 92 msec at 384 TDM bytes per
frame (including the additional intrinsic delay of module – see below).
Such long delays may also cause time-out in certain data transmission
protocols.
 Intrinsic jitter: the transmission of packets to the network is performed at
nominally equal intervals (usually, the interval is 1 msec). This means that
every 1 msec the packet processor sends to the network all the frames
ready for transmission. As a result, the actual payload transmission
intervals vary in an apparently random way whose peak value depends on
the pseudowire size, an effect called
delay variance (or jitter).
For example, a pseudowire with 6 timeslots will fill a 48-byte payload field
of an Ethernet frame every 1 msec. If the sending instants are not
perfectly synchronized with the filling instants, the sending time will
sometimes occur just in time and sometimes will be delayed by 1 msec
relative to the ideal, creating a peak delay variance of 1 msec at the
transmitting side.
The intrinsic jitter in other cases is lower, therefore the delay variance
generated by the MPW-1 modules will not exceed 2 msec.
• Round-trip delay. The round-trip delay for the voice path, in milliseconds, is
calculated as follows:
2 × [“Packetization Delay” + “Jitter Buffer Size” + 1] + “PSN Round Trip Delay”
The actual value is within ±2 msec of the calculated value.
Sometimes, it is necessary to evaluate the transmission bandwidth required on
the PSN, which also depends on the number of TDM bytes. Use the following
formula:
Bandwidth (bps) = [(Frame Overhead (bytes) + TDM Bytes/Frame) × 8] × Frames/Second