Average instantaneous packet delay variation
Comments:
- Without best-effort traffic delay variation increases
rapidly with packet sizes in the range [64, 512] bytes,
then it reaches a steady state
(figure 4).
The PB size does not impact this metric since in
this scenario the premium source is the only one active.
The maximum delay variation is of 1.1 msec for
1024 bytes packets.
- When best-effort traffic is added, then the metric varies
a lot without a regular pattern in the range
[0.92, 2.16] msec
(figure 5) for any PB size with
the exception of PB = 1500 bytes. In such cases
the average istantanous delay is limited (see
figure 6)
for a comparison of the two cases when PB = 1500 bytes).
For PB = 1500 bytes the average delay variation
is well above the other curves, in particular it
reaches peaks of up to 4.50 msec. This must be
connected to the high latency values experienced when
PB = 1500 bytes;
this performance problem is under
study.
- Even in presence of
best-effort traffic for each PB size (apart from 1500
bytes) delay variation is almost constant. This
is a consequence of the weight assigned to the premium
queue which determines the departure rate of premium
packets. We expect that premium buffer size can affect
one-way delay variation when the weight decreases.
In this test the premium weight is 90% (default
value).
Figure 4: average instantaneous one-way delay variation
versus packet size for different
premium buffer sizes, without best-effort traffic.
Figure 5: average instantaneous one-way delay variation
versus packet size for different
premium buffer sizes, with best-effort traffic.
Figure 6: comparison of average instantaneous one-way delay
versus packet size for different
premium buffer sizes, with and without
best-effort traffic.
Last modified: Nov 22, 1999