were similar to today's IPv4 address, but at the time the most-significant 8 bits were the host number. The least-significant portion of the socket number (bits 33 through 40) was an entity called Another Eightbit Number, abbreviated AEN. Today, network socket refers to a related but distinct concept, namely the internal address of an endpoint used only within the node. On March 26, 1972, Vint Cerf and Jon Postel called for documenting the then-current usages and establishing a socket number catalog in RFC 322. Network administrators were asked to submit a note or place a phone call, "describing the function and socket numbers of network service programs at each HOST". This catalog was subsequently published as RFC 433 in December 1972 and included a list of hosts and their port numbers and the corresponding function used at each host in the network. This first registry function served primarily as documentation of usage and indicated that port number usage was conflicting between some hosts for "useful public services". The document promised a resolution of the conflicts based on a standard that Postel had published in May 1972 in RFC 349, in which he first proposed official assignments of port numbers to network services and suggested a dedicated administrative function, which he called a czar, to maintain a registry. The 256 values of the AEN were divided into the following ranges: The Telnet service received the first official assignment of the value 1. In detail, the first set of assignments was: In the early ARPANET, the AEN was also called a socket name, and was used with the Initial Connection Protocol (ICP), a component of the Network Control Protocol (NCP). NCP was the forerunner of the modern Internet protocols. Today the terminology service name is still closely connected with port numbers, the former being text strings used in some network functions to represent a numerical port number. References Internet protocols 1972 introductions