Using The Auto-Sense Mechanism; How Adaptive Mode Works; Figure 14: Example Of Adaptive Ipv6 Multicast Bandwidth Detection - Juniper JUNOSE 11.1.X MULTICAST ROUTING Configuration Manual

Using the Auto-Sense Mechanism

Video bandwidth is typically considered to be a constant rate 2 Mbps for standard
definition television (SDTV) and 10 Mbps for high definition television (HDTV).
However, in reality, and depending on achievable video compression, the bit rate
can vary. For example, HDTV streams (using MPEG4 or WM9 encoding) can vary
between 6 Mbps (for low-action programs) to 10 Mbps (for a fast-paced, high-action
programs). The auto-sense mechanism allows the bandwidth value, used for admission
control and QoS adjustment, to be the actual measured rate of the stream. Using this
feature to measure 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.

How Adaptive Mode Works

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:
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

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
Chapter 5: Configuring IPv6 Multicast
Defining a Multicast Bandwidth Map
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