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How Adaptive Mode Works
Copyright © 2010, Juniper Networks, Inc.
the actual bandwidth avoids the need to configure arbitrary bandwidth limits and enables
a channel to be reassigned to a different (S, G) without requiring a bandwidth map to
be changed.
As mentioned above, you configure the auto-sense mechanism in the multicast bandwidth
using the set admission-bandwidth adaptive command, set qos-bandwidth adaptive
command, or both. For example:
host1(config)#route-map mcast-bandwidths permit 10
host1(config-route-map)#match ip address sdtv
host1(config-route-map)#set admission-bandwidth adaptive
host1(config-route-map)#set qos-bandwidth adaptive
host1(config-route-map)#end
In this example, any stream with an (S,G) that matches the sdtv access list performs
adaptive bandwidth detection for admission control and QoS adjustment.
A rate measurement mechanism runs on the ingress line card that polls the forwarding
controller (FC) to obtain statistics for each mroute. This mechanism then reports the
rate measurement to the SRP to update the bandwidth map. By computing the average
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 14: Example of Adaptive IPv6 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
Chapter 5: Configuring IPv6 Multicast
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