Digital Networks North America DNswitch 800 manual Igmp Multicast Filtering, Configuring Igmp

IGMP Multicast Filtering

Multicasting is used to support real-time applications such as video conferencing or streaming audio. A multicast server does not have to establish a separate connection with each client. It merely broadcasts its service to the network, and any hosts which want to receive the multicast register with their local multicast switch/router. Although this approach reduces the network overhead required by a multicast server, the broadcast traffic must be carefully pruned at every multicast switch/router it passes through to ensure that traffic is only passed on the hosts which subscribed to this service.

This switch uses IGMP (Internet Group Management Protocol) to query for any attached hosts who want to receive a specific multicast service. The switch looks up the IP Multicast Group used for this service and adds any port which received a similar request to that group. It then propagates the service request on to any neighboring multicast switch/router to ensure that it will continue to receive the multicast service. (For more information, see “IP Multicast Filtering” in the DNswitch 800 Management Guide.)

Configuring IGMP

This protocol allows a host to inform its local switch/router that it wants to receive transmissions addressed to a specific multicast address group. Use the IGMP Configuration screen to set key parameters for multicast filtering as shown below.

	Figure 3-30. IGMP Configuration
Parameter	Description
IGMP Status	If enabled, the switch will monitor network traffic to determine
	which hosts want to receive multicast traffic.
Act as IGMP	If enabled, the switch can serve as the “querier,” which is
Querier	responsible for asking hosts if they want to receive multicast
	traffic. (Not available for the current firmware release.)
IGMP Query Count	The maximum number of queries issued for which there has
	been no response before the switch takes action to solicit
	reports. (Range: 2 - 10.)
IGMP Report Delay	The time (in seconds) between receiving an IGMP Report for an
	IP multicast address on a port before the switch sends an IGMP
	Query out that port and removes the entry from its list.
	(Range: 5 - 30.)

Note: The default values are indicated in the sample screen.

DNswitch 800 Configuring and Monitoring the Switch 37