Restrictions For Multicast Subsecond Convergence; Information About Multicast Subsecond Convergence; Benefits Of Multicast Subsecond Convergence; Multicast Subsecond Convergence Scalability Enhancements - Cisco Catalyst 3850 series Configuration Manual

Restrictions for Multicast Subsecond Convergence

Restrictions for Multicast Subsecond Convergence

Devices that use the subsecond designated router (DR) failover enhancement must be able to process hello
interval information arriving in milliseconds. Devices that are congested or do not have enough CPU cycles
to process the hello interval can assume that the Protocol Independent Multicast (PIM) neighbor is disconnected,
although this may not be the case.

Information About Multicast Subsecond Convergence

Benefits of Multicast Subsecond Convergence

• The scalability components improve on the efficiency of handling increases (or decreases) in service
• New algorithms and processes (such as aggregated join messages, which deliver up to 1000 individual
• Multicast subsecond convergence improves service availability for large multicast networks.
• Multicast users such as financial services firms and brokerages receive better quality of service (QoS),

Multicast Subsecond Convergence Scalability Enhancements

The Multicast Subsecond Convergence feature provides scalability enhancements that improve on the efficiency
of handling increases (or decreases) in service users (receivers) and service load (sources or content). Scalability
enhancements in this release include the following:
• Improved Internet Group Management Protocol (IGMP) and PIM state maintenance through new timer
• Improved scaling of the Multicast Source Discovery Protocol (MSDP) Source-Active (SA) cache
The scalability enhancements provide the following benefits:
• Increased potential PIM multicast route (mroute), IGMP, and MSDP SA cache state capacity
• Decreased CPU usage

PIM Router Query Messages

Multicast subsecond convergence allows you to send PIM router query messages (PIM hellos) every few
milliseconds. The PIM hello message is used to locate neighboring PIM devices. Before the introduction of
this feature, the device could send the PIM hellos only every few seconds. By enabling a device to send PIM
hello messages more often, this feature allows the device to discover unresponsive neighbors more quickly.
As a result, the device can implement failover or recovery procedures more efficiently.
IP Multicast Routing Configuration Guide, Cisco IOS XE Release 3.6E (Catalyst 3850 Switches)
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users (receivers) and service load (sources or content).
messages in a single packet) reduce the time to reach convergence by a factor of 10.
because multicast functionality is restored in a fraction of the time previously required.
management techniques
IP Multicast Optimization: Multicast Subsecond Convergence
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