User manual

001-5099-000 HiPR-900 User Manual
58
6.7.3.4.1.2 Multicast
IP multicast addresses are in the range of 224.0.0.0 to 239.255.255.255. These addresses are used to
represent logical groups of units that may or may not reside on the same networks.
Multicast is used when “one-to-many” communication is required. For instance, a radio station might of-
fer a music channel on the Internet in real time. To receive the music a user (host) must know the multi-
cast group (multicast address) used by the radio station and add itself as a member of this group. In the IP
realm, a host uses the IGMP protocol to do this. The routers inside the Internet are using IGMP and other
multicast routing protocol to build the proper path from the sender to the receivers (a tree like path is
formed from the sender to the receivers).
Figure 58 - Registration to multicast group (First Step)
Figure 59 - Registration to multicast group (Second Step)
Sender
(owner of multicast group 226.1.2.3)
Receiver 1
(Add membership 226.1.2.3)
Receiver 2
(Add membership 226.1.2.3)
Receiver 3
(Add membership 226.1.2.3)
Interne
t
Sender
(owner of multicast group 226.1.2.3)
Receiver 1
(member of 226.1.2.3)
Receiver 2
(member of 226.1.2.3)
Receiver 3
(member of 226.1.2.3)
Internet
IP Router
IP Router
IP Router
IP Router
Paths from Sender to Members
(Receivers 1, 2, and 3) flow in the Internet
from IP Router to IP Router to reach
Destinations 226.1.2.3.
Paths are not forwarded over interfaces
that do not lead to a multicast group
member
5
1
2
2
3
3
4
Receiver
(not a member of 226.1.2.3)
Receiver
(not a member of 226.1.2.3)