The following example shows how to configure per interface mroute state limiters to provide multicast CAC in a network environment where all the multicast flows roughly utilize the same amount of bandwidth.
This example uses the topology illustrated in the figure.
Figure 1. Per Interface Mroute State Limit Example Topology
In this example, a service provider is offering 300 SD TV channels. The SD channels are being offered to customers in three service bundles (Basic, Premium, and Gold), which are available to customers on a subscription basis. Each bundle offers 100 channels to subscribers, and each channel utilizes approximately 4 Mbps of bandwidth.
The service provider must provision the Gigabit Ethernet interfaces on the PE device connected to DSLAMs as follows: 50% of the link’s bandwidth (500 Mbps) must be available to subscribers of their Internet, voice, and VoD service offerings while the remaining 50% (500 Mbps) of the link’s bandwidth must be available to subscribers of their SD channel bundle service offerings.
For the 500 Mbps of the link’s bandwidth that must always be available to (but must never be exceeded by) the subscribers of the SD channel bundles, the interface must be further provisioned as follows:
60% of the bandwidth must be available to subscribers of the basic service (300 Mbps).
20% of the bandwidth must be available to subscribers of the premium service (100 Mbps).
20% of the bandwidth must be available to subscribers of the gold service (100 Mbps).
Because each SD channel utilizes the same amount of bandwidth (4 Mbps), per interface mroute state limiters can be used to provide the necessary CAC to provision the services being offered by the service provider. To determine the required CAC needed per interface, the number of channels for each bundle is divided by 4 (because each channel utilizes 4 Mbps of bandwidth). The required CAC needed per interface, therefore, is as follows:
Basic Services: 300 / 4 = 75
Premium Services: 100 / 4 = 25
Gold Services: 100 / 4 = 25
Once the required CAC required per SD channel bundle is determined, the service provider uses the results to configure the mroute state limiters required to provision the Gigabit Ethernet interfaces on the PE device for the services being offered to subscribers behind the DSLAMs:
For the Basic Services bundle, the service provider must limit the number of Basic Service SD channels that can be transmitted out a Gigabit Ethernet interface (at any given time) to 75. Configuring an mroute state limit of 75 for the SD channels offered in the Basic Service bundle provisions the interface for 300 Mbps of bandwidth (the 60% of the link’s bandwidth that must always be available to [but never exceeded by] the subscribers of the Basic Services bundle).
For the Premium Services bundle, the service provider must limit the number of Premium Service SD channels that can be transmitted out a Gigabit Ethernet interface (at any given time) to 25. Configuring an mroute state limit of 25 for the SD channels offered in the Premium Service bundle provisions the interface for 100 Mbps of bandwidth (the 20% of the link’s bandwidth that must always be available to [but never exceeded by] the subscribers of the Premium Service bundle).
For the Gold Services bundle, the service provider must limit the number of Gold Service SD channels that can be transmitted out a Gigabit Ethernet interface (at any given time) to 25. Configuring an mroute state limit of 25 for the SD channels offered in the Gold Service bundle provisions the interface for 100 Mbps of bandwidth (the 20% of the link’s bandwidth that must always be available to [but never exceeded by] the subscribers of the Gold Service bundle).
The service provider then configures three ACLs to be applied to per interface mroute state limiters. Each ACL defines the SD channels for each SD channel bundle to be limited on an interface:
acl-basic--The ACL that defines the SD channels offered in the basic service.
acl-premium--The ACL that defines the SD channels offered in the premium service.
acl-gold--The ACL that defines the SD channels offered in the gold service.
These ACLs are then applied to per interface mroute state limiters configured on the PE device’s Gigabit Ethernet interfaces.
For this example, three per interface mroute state limiters are configured on Gigabit Ethernet interface 0/0 to provide the multicast CAC needed to provision the interface for the SD channel bundles being offered to subscribers:
An mroute state limit of 75 for the SD channels that match acl-basic.
An mroute state limit of 25 for the SD channels that match acl-premium.
An mroute state limit of 25 for the SD channels that match acl-gold.
The following configuration shows how the service provider uses per interface mroute state limiters to provision Gigabit Ethernet interface 0/0 for the SD channel bundles and Internet, Voice, and VoD services being offered to subscribers:
interface GigabitEthernet0/0
description --- Interface towards the DSLAM ---
.
.
.
ip multicast limit out acl-basic 75
ip multicast limit out acl-premium 25
ip multicast limit out acl-gold 25