RFC 3171 (rfc3171) - Page 3 of 8

IANA Guidelines for IPv4 Multicast Address Assignments

RFC 3171             IANA IPv4 Multicast Guidelines          August 2001


4. Internetwork Control Block (224.0.1/24)

   Addresses in the Internetwork Control block are used for protocol
   control that must be forwarded through the Internet.  Examples
   include 224.0.1.1 (NTP [RFC 2030]) and 224.0.1.68 (mdhcpdiscover
   [RFC 2730]).

4.1. Assignment Guidelines

   Pursuant to section 4.4.2 of RFC 2780 [RFC 2780], assignments from the
   Internetwork Control block follow an Expert Review, IESG Approval or
   Standards Action process.  See [IANA] for the current set of
   assignments.

5. AD-HOC Block (224.0.2.0/24 - 224.0.255.0/24)

   Addresses in the AD-HOC block have traditionally been assigned for
   those applications that don't fit in either the Local or Internetwork
   Control blocks.  These addresses are globally routed and are
   typically used by applications that require small blocks of
   addressing (e.g., less than a /24).

5.1. Assignment Guidelines

   In general, the IANA SHOULD NOT assign addressing in the AD-HOC
   Block.  However, the IANA may under special special circumstances,
   assign addressing from this block.  Pursuant to section 4.4.2 of RFC
   2780 [RFC 2780], assignments from the AD-HOC block follow an Expert
   Review, IESG Approval or Standards Action process.  See [IANA] for
   the current set of assignments.

6. SDP/SAP Block (224.2/16)

   Addresses in the SDP/SAP block are used by applications that receive
   addresses through the Session Announcement Protocol [RFC 2974] for use
   via applications like the session directory tool (such as SDR [SDR]).

6.1. Assignment Guidelines

   Since addresses in the SDP/SAP block are chosen randomly from the
   range of addresses not already in use [RFC 2974], no IANA assignment
   policy is required.  Note that while no additional IANA assignment is
   required, addresses in the SDP/SAP block are explicitly for use by
   SDP/SAP and MUST NOT be used for other purposes.







Albanna, et al.          Best Current Practice