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JunosE 11.3.x Multicast Routing Configuration Guide
12
bandwidth over a relatively short sampling period (T1; 5 seconds), the measurement
approximates the peak bandwidth of the multicast stream.
As an example, assume that a new mroute (S1, G1) is added to the interface controller
(IC) at time t0.
Figure 1: Example of Adaptive IPv4 Multicast Bandwidth Detection
To calculate the measured bandwidth of a stream, the router uses the following equation:
R = (N
– N
) / 5
t+5
t
Where
R = Calculated bandwidth of the stream during each sampling interval
N
= Bytes measured at the start of each sampling period (t seconds)
t
N
= Bytes measured at the end of each sampling period (t+5 seconds)
t+5
NOTE: When the mroute is first installed in the FC (at t = 0), R
undetermined. For multicast admission control no joins are admitted until
the first bandwidth measurement is computed (that is, for admission control,
R0 is considered to be infinite). Similarly, no QoS adjustment occurs until the
first bandwidth measurement is computed (that is, for QoS adjustment, R0
is considered to be zero [0]).
Using the previous graph as a reference, the first bandwidth rate (R1
and the bytes received values are subtracted and divided by the sampling period T
yield the average rate. This process is repeated every sampling interval, T
R1, R2, R3, and so on.
The first two sampling interval calculations are as follows:
R
= (N
- N
)/5
1
5
0
R
= (N
- N
)/5
2
#+5
#
is
0
) and at time t
0
, to yield rates
2
Copyright © 2010, Juniper Networks, Inc.
(N
)
5
5
to
1
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