Multicast address allocation

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Multicast address allocation

DHCP servers running Microsoft® Windows Server 2003 allow the assignment of multicast addresses, in addition to the assignment of unicast addresses.

A proposed Internet Engineering Task Force (IETF) standard defines a client/server protocol, the Multicast Address Dynamic Client Allocation Protocol (MADCAP), for defining multicast address allocation between supporting servers and clients. The primary benefit of the proposed MADCAP standard is that you can use it to leverage your existing network infrastructure for assigning multicast addresses in the same way as other IP addresses are currently assigned using DHCP.

Typical applications for multicast are conferencing and audio, which usually require users to specially configure multicast addresses. Unlike IP broadcasts, which are received by all computers or other hosts on the network, a multicast address is a group of computers, using the concept of a group membership to identify the computers to which the message is to be sent.

The multicast address allocation feature has two parts:

  1. A MADCAP server, which distributes multicast addresses.

    To use this feature, the administrator first configures multicast scopes and the corresponding multicast IP ranges on the server, through the DHCP console. Once these scopes are configured and activated, the DHCP Server service can provide multicast addresses in the same way it normally provides unicast IP addresses where DHCP scopes are used.

  2. Client-side application programming interfaces (APIs), which MADCAP clients can use to request, renew, or release multicast addresses.

    Applications that implement MADCAP client support can call these APIs to request a multicast address from a given multicast scope at the MADCAP server. The underlying MADCAP implementation uses protocol messages similar to the DHCP messaging format to negotiate the multicast address lease between the client and server.

For more information, see Using multicast scopes.