ZyXEL Communications Cable Modem, User Manual

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Chapter 1 VLC Overview
VLC1324G User’s Guide
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IGMP Snooping
The VLC supports IGMP snooping enabling group multicast traffic to be only forwarded to
ports that are members of that group; thus allowing you to significantly reduce multicast
traffic passing through your VLC.
IGMP Filter
The IGMP filter defines multicast groups a port can join. You can create IGMP filter profiles
which allow access to a multicast group, then assign the IGMP filter to a specific VDSL2 port.
Multicast Group Limit
You can limit the number of multicast groups a subscriber on a port can join. You may enable/
disable the multicast group limit on individual ports.
Discarding of IGMP Query Messages
The VLC discards IGMP query messages received from subscriber ports. This prevents
subscribers from hosting IGMP multicast servers.
IGMP Statistics
The VLC records the number of active users in an IGMP multicast channel (multicast group).
The VLC also records IGMP message statistics on a per port basis to ease management and
troubleshooting.
IGMP Message Rate Limiting
The VLC can limit how many IGMP message packets a subscriber can send per second. This
prevents subscribers from flooding the multicast server.
Static Multicast
Use static multicast to allow incoming frames based on multicast MAC address(es) that you
specify. This feature can be used in conjunction with IGMP snooping to allow multicast MAC
address(es) that are not learned by IGMP snooping. You can use static multicast to pass
routing protocols, such as RIP and OSPF.
Multicast VLAN
Multicast VLAN is designed for applications (such as Media-on-Demand (MoD)) using
multicast traffic across an Ethernet ring-based service provider network. Multicast VLAN
allows one single multicast VLAN to be shared among different subscriber VLANs on the
network. This improves bandwidth utilization by reducing multicast traffic in the subscriber
VLANs and simplifies multicast group management.
Multicast Bandwidth Control
The VLC supports static bandwidth control for multicast traffic. Bandwidth limits can be
assigned to multicast channels. During IGMP snooping, the system checks the total bandwidth
usage to see if it exceeds the specified limit. If the specified limits are reached, the system
restricts the joining of multicast groups on a per port basis.