RFC 3376 (rfc3376) - Page 3 of 53

Internet Group Management Protocol, Version 3

Alternative Format: Original Text Document
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RFC 3376                         IGMPv3                     October 2002


   Multicast Listener Discovery (MLD) is used in a similar way by IPv6
   systems.  MLD version 1 [MLD] implements the functionality of IGMP
   version 2; MLD version 2 [MLDv2] implements the functionality of IGMP
   version 3.

   The capitalized key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
   "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC-2119].  Due to the lack of italics, emphasis is indicated herein
   by bracketing a word or phrase in "*" characters.

2. The Service Interface for Requesting IP Multicast Reception

   Within an IP system, there is (at least conceptually) a service
   interface used by upper-layer protocols or application programs to
   ask the IP layer to enable and disable reception of packets sent to
   specific IP multicast addresses.  In order to take full advantage of
   the capabilities of IGMPv3, a system's IP service interface must
   support the following operation:

      IPMulticastListen ( socket, interface, multicast-address,
                          filter-mode, source-list )

   where:

   o "socket" is an implementation-specific parameter used to
     distinguish among different requesting entities (e.g., programs or
     processes) within the system; the socket parameter of BSD Unix
     system calls is a specific example.

   o "interface" is a local identifier of the network interface on which
     reception of the specified multicast address is to be enabled or
     disabled.  Interfaces may be physical (e.g., an Ethernet interface)
     or virtual (e.g., the endpoint of a Frame Relay virtual circuit or
     the endpoint of an IP-in-IP "tunnel").  An implementation may allow
     a special "unspecified" value to be passed as the interface
     parameter, in which case the request would apply to the "primary"
     or "default" interface of the system (perhaps established by system
     configuration).  If reception of the same multicast address is
     desired on more than one interface, IPMulticastListen is invoked
     separately for each desired interface.

   o "multicast-address" is the IP multicast address, or group, to which
     the request pertains.  If reception of more than one multicast
     address on a given interface is desired, IPMulticastListen is
     invoked separately for each desired multicast address.





Cain, et. al.               Standards Track
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