Chapter 25: Multicast
STANDARD Revision 1.0
C4® CMTS Release 8.3 User Guide
© 2016 ARRIS Enterprises LLC. All Rights Reserved.
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IP Multicast
This section describes the C4/c CMTS implementation of multicasting as it relates to the handling and forwarding of IP
multicast traffic.
What is IP Multicast?
IP Multicast is an Internet technology that permits a sender to send data (either clear or encrypted) simultaneously to
many hosts. Unlike unicasting, multicasting does not send the same data as many times as there are recipients.
Furthermore, unlike broadcasting, it does not flood a network by sending packets to all the hosts when they are meant
only for some. Multicasting sends the data only to those interfaces on which there are hosts that have requested it.
In order to receive a multicast service, hosts must join a multicast group. This multicast group has an associated group
address. The source of this multicast traffic sends data to this group address. Any host belonging to the group processes
the multicast data. Hosts that do not belong to the group do not process this data. The sender is not required to belong to
the group: a multicast server can transmit to the group without belonging to it.
Multicast Traffic
Multicast traffic is often used for network equipment communication protocols. Network protocols such as Internet Group
Management Protocol (IGMP), Routing Information Protocol (RIP), and Open Shortest Path First (OSPF) all communicate
via multicast.
MDF
Multicast DSID-based Forwarding (MDF) is a key component of DOCSIS 3.0 multicast functionality.
Note: Since MDF supports various applications, caution must be exerted when the MDF-disabled mode is used so that it
does not affect other applications in your system.
More details are described in the DOCSIS 3.0 MULPI specification. For more information, see the following command:
configure interface cable-mac <mac> cable mcast-fwd-by-dsid [no]