MASC, Multicast Address-Set Claim

Description Glossary RFCs Publications Obsolete RFCs


Protocol suite: TCP/IP.
Protocol type:Application layer protocol.
Multicast addresses:
Ports:2587 (TCP).
MIME subtype:
Working groups: malloc, Multicast-Address Allocation.

RFC 2909:

MASC is used by a node (typically a router) to claim and allocate one or more address prefixes to that node's domain. Each prefix has an associated lifetime, and is chosen out of a larger prefix with a lifetime at least as long, in a manner such that prefixes are aggregatable. At any time, each MASC node will typically advertise several prefixes with different lifetimes and scopes, allowing Multicast Address Allocation Servers (MAAS's) in that domain or child MASC domains to choose appropriate addresses for their clients.

The MASC protocol is used by MASC domains to claim and allocate address sets for use by Multicast Address Allocation Servers (MAASs) within each domain. Typically one or more border routers of each domain that requires multicast address space of its own would run MASC.

A MASC message is processed only after it is entirely received. The maximum message size is 4096 bytes. All implementations are required to support this maximum message size.

MAC header IP header TCP header MASC header Data :::

MASC header:

0001020304050607 0809101112131415 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Length Type reserved
Data :::

Length. 16 bits. Unsigned integer.
This field indicates the total length of the message, including the header, in bytes. The value of this field must always be at least 4 and no greater than 4096, and may be further constrained, depending on the message type. No padding of extra data after the message is allowed, so this field must have the smallest value required given the rest of the message.

Type. 8 bits.
MASC message type.

3 Notification.

reserved. 8 bits.
Must be cleared to 0 by the sender and ignored by the receiver.


MAAS, Multicast Address Allocation Server.
(RFC 2909) A host providing multicast address allocation services to end users (e.g. via MADCAP).

MASC server.
A node running MASC.


[RFC 2909] The Multicast Address-Set Claim (MASC) Protocol.


Obsolete RFCs:

Description Glossary RFCs Publications Obsolete RFCs