Multicast Architecture - H3C s3100-52P Operation Manual

Operation Manual – Multicast
H3C S3100-52P Ethernet Switch

1.3 Multicast Architecture

The purpose of IP multicast is to transmit information from a multicast source to
receivers in the multicast mode and to satisfy information requirements of receivers.
You should be concerned about:
Host registration: What receivers reside on the network?
Technologies of discovering a multicast source: Which multicast source should
the receivers receive information from?
Multicast addressing mechanism: Where should the multicast source transports
information?
Multicast routing: How is information transported?
IP multicast is a kind of peer-to-peer service. Based on the protocol layer sequence
from bottom to top, the multicast mechanism contains addressing mechanism, host
registration, multicast routing, and multicast application:
Addressing mechanism: Information is sent from a multicast source to a group of
receivers through multicast addresses.
Host registration: A receiving host joins and leaves a multicast group dynamically
using the membership registration mechanism.
Multicast routing: A router or switch transports packets from a multicast source to
receivers by building a multicast distribution tree with multicast routes.
Multicast application: A multicast source must support multicast applications, such
as video conferencing. The TCP/IP protocol suite must support the function of
sending and receiving multicast information.
Multicast Address
As receivers are multiple hosts in a multicast group, you should be concerned about the
following questions:
What destination should the information source send the information to in the
multicast mode?
How to select the destination address?
These questions are about multicast addressing. To enable the communication
between the information source and members of a multicast group (a group of
information receivers), network-layer multicast addresses, namely, IP multicast
addresses must be provided. In addition, a technology must be available to map IP
multicast addresses to link-layer MAC multicast addresses. The following sections
describe these two types of multicast addresses:
I. IP multicast address
Internet Assigned Numbers Authority (IANA) categorizes IP addresses into five classes:
A, B, C, D, and E. Unicast packets use IP addresses of Class A, B, and C based on
network scales. Class D IP addresses are used as destination addresses of multicast
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Chapter 1 Multicast Overview