Understanding Source Port Check; Understanding Fast-Leave; Understanding Igmp Snooping Suppression; Typical Application - D-Link xStack DGS-3610 Series Configuration Manual

Chapter 15 IGMP Snooping Configuration
The IVGL mode and SVGL mode of IGMP Snooping provided by DGS-3610 strengthens the
network application flexibility, enabling it to adapt to different network environment.
15.1.5

Understanding Source Port Check

DGS-3610 series support IGMP SNOOPING source port check function and improve the
security of the network.
IGMP source port check refers to the entry port of strictly restricting the IGMP multicast flow.
When IGMP source port check is disabled, the video flow entering through any port is legal.
The switch will forward them to the registered port. When the IGMP source port check is
enabled, only the video flows entering through the router interface are legal, the switch
forwards them to the registered port; while the video flows entering through non- router
interface are deemed as illegal and will be discarded.
15.1.6

Understanding fast-leave

According to the IGMP protocol, the Leave packets must meet the following requirement:
―Ports should not be allowed to leave a group immediately. Instead, the multicast router
should first send IGMP Query packets, and ports are allowed to leave the group only when
the host does not respond‖. However, in specific environments (for example, one port is
connected to only one multicast group user), the IGMP snooping can immediately leave after
receiving LEAVE packets, a mechanism known as Fast Leave.
15.1.7 Understanding IGMP Snooping
Suppression
For the devices enabled with IGMP Snooping, every group address may have multiple IGMP
users. When every user joins the group and receives the Query message, it will send a
Report packet. For every Report packet, DGS-3610 series will forward it to the multicast
router. In this way, when the multicast router sends a Query to the port enabled with the
Snooping device, it will receive multiple Report packets. To lighten the pressure of the server
in processing Report packets, the switch only forwards the first report packet received to the
routing port when multiple hosts request to join a multicast group, suppressing other report
packets. This function is called IGMP Snooping Suppression.
Due to the special form of the IGMP v3 Report packets, IGMP Snooping Suppression only
supports suppression of v1 and v2 Report packets.
15.1.8

Typical Application

The multicast is applied more and more widely. It is primarily applied in campus network and
residential community network. The multicast technology can be applied in services such as
weather forecast, news broadcasting, and VoD, and currently the most common is the VOD.
The following figure shows the common network topology.
15-8
DGS-3610 Series Configuration Guide