User's Manual

Table Of Contents
Configuration Guide of XGS-5240-Series
43-1
Chapter 43 IPv6 Multicast Protocol
43.1 MLD
43.1.1
Introduction to MLD
MLD (Multicast Listener Discovery) is the multicast group member (receiver) discov
ery protocol serving IPv6 multicast. It is similar to IGMP Protocol in IPv4 multicast appli
cation. Correspondingly, MLD Protocol version1 is similar to IGMP Protocol version2, an
d MLD Protocol version2 is similar to IGMP Protocol version3. Current firmware suppo
rts MLDv1/ MLDv2.
The IPv6 multicast hosts can join or leave from multicast group at any location, an
y time, regardless of the total number of group members. It is unnecessary and imposs
ible for multicast switch to store the relationship among all host members. Multicast swi
tch simply finds out via MLD protocol if there are receivers of certain multicast group o
n the network segment connected to each port. The only thing host need to do is to k
eep the record of which multicast groups it joined.
MLD is unsymmetrical between host and switch: the host needs to respond the ML
D query message of multicast switch with membership report message; the switch perio
dically sends membership query message and determines if there is host joining a spe
cific group in its subnetworks according to the response message received, and after it
receives the report of a host quitting from the group, it sends out the query for the gr
oup to confirm if there is no member left in it.
There are three types of protocol messages of MLD Protocol, that is, Query, Repo
rt and Done (which is corresponding to Leave of IGMPv2). Like IGMPV2, the Query m
essages include General Query and Specific Group Query. General Query uses the mul
ticast address FF02::1 of hosts as destination address, the group address is 0; and Sp
ecific Group Query use its group address as destination address. The multicast address
es of MLD use 130, 131 and 132 as data types denoting the three kinds of messages
mentioned above. Other logic is basically same as IGMPv2.
MLD protocol version2 use FF02::16 as destination address of membership report, and
143 as data type. The other logic of MLD Protocol version2 is similar to IGMP Protocol
version3.
43.1.2 MLD Configuration Task List