INTRODUCTION The files in this directory document the currently assigned values for several series of numbers used in network protocol implementations. ftp://ftp.isi.edu/in-notes/iana/assignments The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols. The IANA is chartered by the Internet Society (ISOC) and the Federal Network Council (FNC) to act as the clearinghouse to assign and coordinate the use of numerous Internet protocol parameters. The Internet protocol suite, as defined by the Internet Engineering Task Force (IETF) and its steering group (the IESG), contains numerous parameters, such as internet addresses, domain names, autonomous system numbers (used in some routing protocols), protocol numbers, port numbers, management information base object identifiers, including private enterprise numbers, and many others. The common use of the Internet protocols by the Internet community requires that the particular values used in these parameter fields be assigned uniquely. It is the task of the IANA to make those unique assignments as requested and to maintain a registry of the currently assigned values. Requests for parameter assignments (protocols, ports, etc.) should be sent to <iana@isi.edu>. Requests for SNMP network management private enterprise number assignments should be sent to <iana-mib@isi.edu>. The IANA is located at and operated by the Information Sciences Institute (ISI) of the University of Southern California (USC). If you are developing a protocol or application that will require the use of a link, socket, port, protocol, etc., please contact the IANA to receive a number assignment. Joyce K. Reynolds Internet Assigned Numbers Authority USC - Information Sciences Institute 4676 Admiralty Way Marina del Rey, California 90292-6695 Electronic mail: IANA@ISI.EDU Phone: +1 310-822-1511 Most of the protocols are documented in the RFC series of notes. Some of the items listed are undocumented. Further information on protocols can be found in the memo, "Internet Official Protocol Standards" (STD 1). Data Notations The convention in the documentation of Internet Protocols is to express numbers in decimal and to picture data in "big-endian" order [COHEN]. That is, fields are described left to right, with the most significant octet on the left and the least significant octet on the right. The order of transmission of the header and data described in this document is resolved to the octet level. Whenever a diagram shows a group of octets, the order of transmission of those octets is the normal order in which they are read in English. For example, in the following diagram the octets are transmitted in the order they are numbered. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1 | 2 | 3 | 4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 5 | 6 | 7 | 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 9 | 10 | 11 | 12 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Transmission Order of Bytes Whenever an octet represents a numeric quantity the left most bit in the diagram is the high order or most significant bit. That is, the bit labeled 0 is the most significant bit. For example, the following diagram represents the value 170 (decimal). 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ |1 0 1 0 1 0 1 0| +-+-+-+-+-+-+-+-+ Significance of Bits Similarly, whenever a multi-octet field represents a numeric quantity the left most bit of the whole field is the most significant bit. When a multi-octet quantity is transmitted the most significant octet is transmitted first. Special Addresses There are five classes of IP addresses: Class A through Class E. Of these, Classes A, B, and C are used for unicast addresses, Class D is used for multicast addresses, and Class E addresses are reserved for future use. With the advent of classless addressing [CIDR1, CIDR2], the network-number part of an address may be of any length, and the whole notion of address classes becomes less important. There are certain special cases for IP addresses. These special cases can be concisely summarized using the earlier notation for an IP address: IP-address ::= { <Network-number>, <Host-number> } or IP-address ::= { <Network-number>, <Subnet-number>, <Host-number> } if we also use the notation "-1" to mean the field contains all 1 bits. Some common special cases are as follows: (a) {0, 0} This host on this network. Can only be used as a source address (see note later). (b) {0, <Host-number>} Specified host on this network. Can only be used as a source address. (c) { -1, -1} Limited broadcast. Can only be used as a destination address, and a datagram with this address must never be forwarded outside the (sub-)net of the source. (d) {<Network-number>, -1} Directed broadcast to specified network. Can only be used as a destination address. (e) {<Network-number>, <Subnet-number>, -1} Directed broadcast to specified subnet. Can only be used as a destination address. (f) {<Network-number>, -1, -1} Directed broadcast to all subnets of specified subnetted network. Can only be used as a destination address. (g) {127, <any>} Internal host loopback address. Should never appear outside a host. REFERENCES [COHEN] Cohen, D., "On Holy Wars and a Plea for Peace", IEEE Computer Magazine, October 1981. [CIDR1] Fuller, V., T. Li, J. Yu, and K. Varadhan, "Classless Inter-Domain Routing (CIDR): an Address Assignment and Aggregation Strategy", RFC 1519, September 1993. [CIDR2] Rekhter, Y., and T. Li, "An Architecture for IP Address Allocation with CIDR", RFC 1518, September 1993. []