Using The Autosense Mechanism; How Adaptive Mode Works - Juniper JUNOSE 11.0.X MULTICAST ROUTING Configuration Manual

NOTE: Even though you can include any of the preceding commands several times
in a route map entry, only the last admission-bandwidth command or qos-bandwidth
command in the bandwidth map is used. In other words, if you included the set
qos-bandwidth command first and then the set qos-bandwidth adaptive command,
the bandwidth map uses the set qos-bandwidth adaptive command.
Interface-level and port-level admission control is performed when an OIF on the
interface or port is added to the mroute for a given (S,G) multicast data stream and
the multicast bandwidth map contains a set admission-bandwidth or set
admission-bandwidth adaptive action for that (S,G).
QoS adjustment is performed on the joining interface when an OIF is added to the
mroute for a given (S,G) data stream and the multicast bandwidth map contains a
set qos-bandwidth or set qos-bandwidth adaptive action for that (S,G).
You can prioritize the traffic by configuring a priority value for the <S, G> data
stream on a physical port by issuing the set priority command. Dynamic multicast
admission control enables only prioritized groups to join the interface after the
configured priority limit is reached on the physical port. The system records the
priority when a new <S, G> entry is created. For more information, see "Enabling
Port Admission Bandwidth Control" on page 28 .
NOTE: You can create a single route map with the set admission-bandwidth
command, the set qos-bandwidth command, or both. However, creating an entry
with only one of these set commands enables only that specific function for the
matched address (that is, only multicast traffic admission control or only QoS
adjustment). The same is true for the adaptive commands.

Using the Autosense 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 autosense mechanism causes 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

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
Chapter 1: Configuring IPv4 Multicast
Defining a Multicast Bandwidth Map
11