Information Technology Reference
In-Depth Information
C
H
A
P
T
E
R
11
Multiprotocol BGP and
Interdomain Multicast
This chapter begins with an overview of the fundamentals of IP multicast that are the foun-
dation of the coverage of Multicast Source Discovery Protocol (MSDP) and its counterpart,
Multicast Extensions for Multiprotocol BGP. The chapter concludes with a case study
detailing the deployment of interdomain multicast in a service provider network. The case
study covers the internal architecture of the multicast deployment, the customer connectiv-
ity options for multicast services, and interdomain multicast connectivity.
Multicast Fundamentals
The traditional data delivery model for computer networks is unicast-based traffic streams.
This model has a single receiver for the data stream. This data delivery method works very
well for many types of communication, such as web pages and e-mail. However, with
another class of communication, this data delivery model faces serious scaling issues. An
example of this class of communication is real-time or live multimedia streaming. The
inefficient traffic pattern shown in Figure 11-1 results in a linear increase in traffic on the
network for each additional receiver that joins the stream. This inefficiency can be resolved
through implementing Multicast Distribution Trees.
Multicast Distribution Trees
The concept of IP multicast is that sending source(s) and listeners form a group. A spanning
tree connecting all the listeners or receivers that use the source as the root employs a
different distribution model than unicast-based traffic streams. At each branch of the tree,
the data is replicated and forwarded down each branch. This model of data delivery is
shown in Figure 11-2.
