MADCAP, Multicast Address Dynamic Client Allocation Protocol

Description Glossary RFCs Publications Obsolete RFCs


Protocol suite: TCP/IP.
Protocol type:Application layer configuration protocol.
Multicast addresses:
Ports:2535 (UDP).
MIME subtype:
Working groups: malloc, Multicast-Address Allocation.

RFC 2730:

MADCAP is a protocol that allows hosts to request multicast address allocation services from multicast address allocation servers.

MADCAP is built on a client-server model, where hosts request address allocation services from address allocation servers. When a MADCAP client wishes to request a service, it unicasts or multicasts a message to one or more MADCAP servers, each of which optionally responds with a message unicast to the client.

MAC header IP header UDP header MADCAP header Data :::

MADCAP header:

0001020304050607 0809101112131415 1617181920212223 2425262728293031
Version Msgtype Addrfamily
Options :::

Version. 8 bits.
MADCAP protocol version. Must be cleared to 0.

Msgtype. 8 bits.
MADCAP message code.

2OFFER. RFC 2730
4RENEW. RFC 2730
5ACK. RFC 2730
6NAK. RFC 2730

Addrfamily. 16 bits.
Defines the default address family (such as IPv4 or IPv6) for this MADCAP message, using the address family numbers defined in by the IANA. Unless otherwise specified, all addresses included in the message will be from this family.

Xid. 32 bits.
A transaction identifier. This number MUST be chosen by the client so that the combination of xid, msgtype, and Lease Identifier is unique across all MADCAP messages received by a MADCAP server over a period of [XID-REUSE-INTERVAL] (10 minutes).

Options. Variable length.

00End. RFC 2730
14Lease Time. RFC 2730
2variableServer Identifier. RFC 2730
3variableLease Identifier. RFC 2730
4variableMulticast Scope. RFC 2730
5 variable Option Request List. RFC 2730
6 4 Start Time. RFC 2730
7 4 Number of Addresses Requested RFC 2730
8 variable Requested Language. RFC 2730
9 variable Multicast Scope List. RFC 2730
10 variable List of Address Ranges. RFC 2730
11 4 Current Time. RFC 2730
12 variable Feature List. RFC 2730
13 4 Retry Time. RFC 2730
14 4 Minimum Lease Time. RFC 2730
154Maximum Start Time. RFC 2730
16variableError. RFC 2730
17 Multicast Nesting State. RFC 2907


MADCAP client.
(RFC 2730) A host requesting multicast address allocation services via MADCAP.

MADCAP server.
(RFC 2730) A host providing multicast address allocation services via MADCAP.

Multicast Scope.
(RFC 2730) A range of multicast addresses configured so that traffic sent to these addresses is limited to some subset of the internetwork.

Multicast Scope List.
(RFC 2730) A list of multicast scope zones. Since it can be difficult to determine which multicast scope zones are in effect, MADCAP clients can ask MADCAP servers to supply a Multicast Scope List listing all of the zones available to the client. For each scope zone, the list includes the range of multicast addresses for this scope, a maximum TTL or hop count to be used for this scope, and one or more zone names for this scope zone.

Scope ID.
(RFC 2730) The lowest numbered address in a multicast scope.

Scope Zone.
(RFC 2730) One multicast scope may have several instances, which are known as Scope Zones or zones, for short. For instance, an organization may have multiple sites. Each site might have its own site-local Scope Zone, each of which would be an instance of the site-local Scope. However, a given interface on a given host would only ever be in at most one instance of a given scope. Messages sent by a host in a site-local Scope Zones to an address in the site-local Scope would be limited to the site-local Scope Zone containing the host.

Zone Name.
(RFC 2730) A human readable name for a Scope Zone. An ISO 10646 character string with an RFC 1766 language tag. One zone may have several zone names, each in a different language. For instance, a zone for use within IBM's locations in Switzerland might have the names "IBM Suisse", "IBM Switzerland", "IBM Schweiz", and "IBM Svizzera" with language tags "fr", "en", "de", and "it".


[RFC 2730] Multicast Address Dynamic Client Allocation Protocol (MADCAP).

[RFC 2907] MADCAP Multicast Scope Nesting State Option.


Obsolete RFCs:

Description Glossary RFCs Publications Obsolete RFCs