Introduction To Igmp Snooping - UTStarcom iSpirit 3026 Manual

In WAN (Wide Area Network) or Internet, when sending the same copy of data to multiple
receivers (not all of the receivers in the network, which can then use broadcast), if using unicast,
the sender has to send one by one, it is becoming very inefficient when the number of receivers
increases, by consuming too much network resources and overloading hosts and other devices.
So multicast is becoming one of the main methods for point-to-multipoint transmission when
such applications like tele-conferencing, VOD (Video On Demand), etc... are becoming more
popular.
The iSpirit 3026 switch supports IGMP (Internet Group Management Protocol), IGMP Snooping
and Layer 2 static multicast, all of them are used for providing multicasting services. IGMP is for
group management. IGMP Snooping monitors IGMP packets in the network and can also learn
multicast MAC address dynamically. Layer 2 static multicast functionality can be used to
configure layer 2 multicast addresses by hand.

7.1 Introduction to IGMP SNOOPING

In traditional network multicast packets in a subnet is handled as broadcast, which may increase
the network flow dramatically and thus block the network. With IGMP SNOOPING on the switch,
it can dynamically learn IP multicast addresses and maintain the output ports list, as a result,
multicast data are only sent to output ports list and network flow can be decreased to a large
degree.
For Layer 2 static multicast addresses are configured by hand, while for IGMP SNOOPING, they
are learned dynamically. They are closely related to each other. Please refer to Chapter 6 "Layer
2 static multicast configuration" for more information on static multicast.
Section Index:
The procedure for IGMP SNOOPING;
Layer 2 dynamic multicast and Layer 2 static multicast;
To add a group;
To delete a group.
1. The procedure for IGMP SNOOPING
IGMP SNOOPING is a Layer 2 network protocol, it monitors the IGMP packets passing through
the switch and maintains multicast routing entries based on information such as ingress ports,
VLAN ID and multicast addresses collected from the packets, finally these IGMP packets are
transmitted. Only ports that are added to a multicast group are allowed to receive multicast data
packets. So IGMP SNOOPING can decrease network load and save network bandwidth.