Information Technology Reference
In-Depth Information
Session rule, which results in a peer-RPF failure. The AS_PATH to the originating RP is 2,
and the AS_PATH to the MSDP peer is "". This results in a failure on the peer-RPF check,
per Rule 3.
Case Study: Service Provider Multicast Deployment
This case study looks at the three aspects of deploying IP multicast.
The first aspect is the internal architecture. A deployment with a single RP is not redundant,
because the RP is a single point of failure. The concept of RP Anycast is introduced to
provide redundancy, using mesh groups to optimize SA flooding.
The second aspect is customer connectivity. There are multiple options for providing mul-
ticast service, depending on the level and type of redundancy. There is also the consider-
ation of whether the customer has his or her own RP or will be using upstream ISPs RP.
The third aspect is interdomain connectivity. This section covers extending the local
multicast service to allow customers to receive nonlocal multicast traffic streams and to
allow remote access to customer-generated multicast data streams.
Anycast RP
So far, we have assumed a static configuration of RPs in all the routers. The need for RP
redundancy is addressed by Cisco's Auto-RP, Bootstrap Router (BSR), and the develop-
ment of MSDP, Anycast RP. The recommended method is Anycast RP, which is covered
here.
The concept of Anycast RP is to configure multiple routers with the same IP address,
making this address the network's RP. This results in a network with all routers agreeing on
the RP's identity, but multiple routers acting as that RP. Sources register to the nearest RP,
and the receiver's upstream routers build the shared tree to the nearest RP.
The problem is that the RPs used are not always the same. A receiver attempting to join a
group might end up with a shared tree to an RP that does not know about the active source,
which registered with a different RP.
The solution to this problem is to use MSDP between all the RPs to ensure that every RP
contains all the active source information for the domain. Figure 11-27 shows a small core
network with four RPs and the MSDP peering needed to provide a working deployment.
