GE instruction manual Multilink ML1200 Managed Field Switch Igmp, Igmp Concepts

Digital Energy

Multilin

Multilink ML1200

Managed Field Switch

Chapter 15: IGMP

15.1Overview

15.1.1 Description

Internet Group Management Protocol (IGMP) is defined in RFC 1112 as the standard for IP multicasting in the Internet. It is used to establish host memberships in particular multicast groups on a single network. The mechanisms of the protocol allows a host to inform its local router, using Host Membership Reports that it wants to receive messages addressed to a specific multicast group. All hosts conforming to level 2 of the IP multicasting specification require IGMP.

15.1.2 IGMP Concepts

The ML1200 supports IGMP L2 standards as defined by RFC 1112. IGMP is disabled by default and needs to be enabled on the MultiLink ML1200 Managed Field Switch. IP multicasting is defined as the transmission of an IP datagram to a “host group”, a set of zero or more hosts identified by a single IP destination address. A multicast datagram is delivered to all members of its destination host group with the same “best-efforts” reliability as regular unicast IP datagrams, i.e. the datagram is not guaranteed to arrive at all members of the destination group or in the same order relative to other datagrams.

The membership of a host group is dynamic; that is, hosts may join and leave groups at any time. There is no restriction on the location or number of members in a host group, but membership may be restricted to only those hosts possessing a private access key. A host may be a member of more than one group at a time. A host need not be a member of a group to send datagrams to it.

A host group may be permanent or transient. A permanent group has a well-known, administratively assigned IP address. It is the address and not the membership that is permanent – at any time, a permanent group may have any number of members, even

MULTILINK ML1200 MANAGED FIELD SWITCH – INSTRUCTION MANUAL 15–1