Multicast Offload Scalability; Multicast Offload Use Case Scenario - Cisco ASR 9000 Series System Configuration Manual

Configuring Multicast Offload on the Satellite nV System
device stays with a host as a designated multicast forwarder until it goes down and does not switch back if
the previous host that triggered a switchover comes up.
For more information, see Configuring Interchassis Communication Protocol section in the Cisco ASR 9000
Series Aggregation Services Router Interface and Hardware Component Configuration Guide

Multicast Offload Scalability

These are the maximum scale capabilities of Multicast Offload Solution:
• The maximum number of rings over which the same offloaded route can be downloaded is 32.
• The maximum number of offloaded routes for each satellite or ring is 2000.
• The maximum number of offloaded OLEs for each satellite is 7800.
• The maximum number of OLEs for each route in each satellite is 44.
• The maximum number of offloaded routes for each system is equal to the maximum number of rings
• The maximum bandwidth of ICL to ICL traffic with offload enabled for each satellite is 6Gbps in each

Multicast Offload Use Case Scenario

The Satellite nV multicast offload feature has been designed and optimized specifically for an IPTV scenario
where the Cisco ASR 9000 Series Satellite nV System replaces the traditional edge or aggregate router and
switch solution. The Satellites feed multicast traffic from the Layer 2 or Layer 3 (through BVI) core to the
Layer 2 access trunk links connecting DSLAMs which in turn terminate residential gateways and take care
of subscriber aware processing, if any, as shown below.
Residential Gateway ---- DSLAM ---- Cisco ASR 9000 Satellite nV System---- Core ---- IPTV source
Therefore, the Satellite nV multicast offload solution does not need to support VLAN rewrite operations on
individual offloaded replications as they all go over the same trunk video VLAN. This reduces the offload
processing overhead on the satellite devices to achieve line rate replication. Similarly, the solution is optimized
to an use case that requires minimal egress feature processing. QoS, ACL and other egress features act on the
pre-replicated multicast stream and the configuration needs to be replicated to all participating OLEs in the
offload, if at all feature processing is specifically required.
Network design needs to ensure that there is no congestion on the satellites post replication. This is critical
and different from a non-offload solution as the Host takes care of correct priority aware traffic shaping
through Auto QoS or a user specified MQC policy for the non-offload case. For offloaded traffic, as the
replication happens locally on the satellite devices, the Host QoS is unaware of the total traffic volume post
replication, and therefore cannot include it in its bandwidth computations without statically reserving bandwidth
on all offload participating OLEs.
Such a permanent reservation might be sub-optimal in most cases and a rigid reservation may not cater to
user needs. However, a solution based on intelligent network design is generally straightforward for the IPTV
roll outs, as they have well defined bandwidth planning, given the load generally remains constant over time.
For residential triple and quadruple play cases, with possibility of other priority and internet traffic causing
oversubscriptions, a simple QoS port-shaper policy on the egress video traffic DSCP/CoS markers or VLAN
multiplied by 2000 up to the Host limit (128k).
direction.
Cisco ASR 9000 Series Aggregation Services Router nV System Configuration Guide, Release 5.3.x
Multicast Offload Scalability
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