Designing the IP Network for Multicasting
Whether you’re designing a new network for AVVID, or modifying an existing
one, several requirements must be met if the solution is to work correctly.Among
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Figure 10.18 Ensuring Proper Telephony Selections Are Made
372 Chapter 10 • Designing and Implementing Single Site Solutions
these is the configuration of the routers to handle multicast IP traffic. So, what is
multicasting?
Multicasting is the ability of one host to transmit data to many recipients
without having to address each one individually. Let’s say computer A needs to
send information to 25 destinations. If we looked at this as though it were
e-mail, we’d have to place 25 e-mail addresses in the message’s TO: line. Instead,
let’s create a distribution list containing the 25 recipients, each of whom will
receive a proposed e-mail.The distribution list then becomes the registration
point for each member. Granted, users must be manually entered into the distribution
list to become a member, but the list makes life easier when sending
e-mail to large numbers of recipients.
Multicasting on a network is very similar to this concept, except that computers
are the recipients of the information, or more correctly, the application
running on each computer is the recipient of the multicast stream.Your first
impression might be to presume this is the same as standard television, but it is
not.TV is a broadcast medium, meaning that everyone receives the data that the
head end sends out.True, your end might be blocked from seeing channels you
don’t subscribe to, but your end is still receiving all the channels. At this point,
however, the parallel diverges quite drastically. Figure 10.19 shows the network
we’ll build on for the remainder of this chapter.