ZyXEL Communications GS1920-24 User Manual page 167

Chapter 23 Multicast
one query from a router (X) or MLD Done or Report message from any upstream port, it will be
broadcast to all connected upstream ports.
X
Query
1
2
9
8
3
7
4
Report
6
5
Done
MLD Messages
A multicast router or switch periodically sends general queries to MLD hosts to update the multicast
forwarding table. When an MLD host wants to join a multicast group, it sends an MLD Report
message for that address.
An MLD Done message is similar to an IGMP Leave message. When an MLD host wants to leave a
multicast group, it can send a Done message to the router or switch. If the leave mode is not set to
Immediate, the router or switch sends a group-specific query to the port on which the Done
message is received to determine if other devices connected to this port should remain in the
group.
MVR Overview
Multicast VLAN Registration (MVR) is designed for applications (such as Media-on-Demand (MoD))
that use multicast traffic across an Ethernet ring-based service provider network.
MVR allows one single multicast VLAN to be shared among different subscriber VLANs on the
network. While isolated in different subscriber VLANs, connected devices can subscribe to and
unsubscribe from the multicast stream in the multicast VLAN. This improves bandwidth utilization
with reduced multicast traffic in the subscriber VLANs and simplifies multicast group management.
MVR only responds to IGMP join and leave control messages from multicast groups that are
configured under MVR. Join and leave reports from other multicast groups are managed by IGMP
snooping.
The following figure shows a network example. The subscriber VLAN (1, 2 and 3) information is
hidden from the streaming media server, S. In addition, the multicast VLAN information is only
visible to the Switch and S.
GS1920 Series User's Guide
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