ANSI delegates standardization work to experts by accrediting an expert group to carry out the work. Committee T1 is accredited by ANSI to produce technical specifications for U.S. telecommunications networks. Committee T1 standards are easy to spot. They are numbered starting with T1, followed by a period and a document number, such as T1.403. ANSI standards are copyrighted and must be purchased.

The ITU develops recommendations for telecommunications through the work of its telecommunications sector, ITU-T. Related work is carried out in other sectors, so the “-T” is used to indicate the telecommunications standardization efforts. When only one ITU sector is involved, most documentation drops the “-T” in favor of the simpler “ITU.”

The ITU’s standardization work is divided into several series, and the resulting standards are labeled with the series letter and a document number. The most common series of wide-area networking standards are shown in Table F-1.

ITU recommendations must be purchased. Many recommendations are inter-linked, which means that understanding a topic often requires reading several recommendations. Large companies, especially telecommunications-equipment vendors and carriers, often obtain site licenses. If you work for a major vendor or carrier, you may have access to most, if not all, recommendations.

ITU recommendations are detailed documents that can be a challenge to implement fully. The Frame Relay Forum (FRF) publishes implementation agreements (IAs). IAs are interpretations of ITU recommendations; essentially, they are agreements by FRF members to make some of the complex ITU functionality optional. Such an approach allows for a phased rollout of complex features contained in existing standards. Compatibility testing performed by interoperability labs is based on the IA, which covers that particular functionality. IAs may be downloaded from the FRF web site for no charge.

The ISO is composed of representatives from 130 national standards bodies.^[37] Information technology specifications are carried out with the International Electrotechnical Commission (IEC) and are published as standards from the Joint Technical Committee ( JTC). ISO/IEC JTC specifications are numbered and dated. For example, the most recent HDLC specification is ISO/IEC 3309:1993, which gives both a specification number (3309) and a revision date (1993).

The IETF is different from most other standards bodies. In keeping with the functional anarchy of the Internet, the IETF has no fixed membership, and leadership is by example and technical contribution.

IETF standards are called Requests for Comments (RFCs). RFCs are numbered in chronological order. Not all RFCs are standards; the RFC series is a living history of the Internet, in which the best current practice information and descriptions of the current state of networking are mixed. Many RFCs dated April 1 are worth reading for the humor value.^[38]

RFCs are frequently updated to cope with changing technology. Unlike many other standards documents, RFCs are never revised and republished with the same numerical identifier. Each update to a protocol is published in a new RFC. New protocol versions are published in new RFCs that “obsolete” (i.e., supersede) older RFCs. The IETF maintains a list of RFCs that includes status information for each one. Manually checking the IETF list can be a chore, though. The RFC editor has made a search engine available that will pull up any related RFCs, including updates to preexisting RFCs, at http://www.rfc-editor.org/rfcsearch.html.

Devising standard protocol specifications is only half the battle in creating interoperable network protocols. A plethora of numerical identifiers are required to keep the network functioning.

All protocols may have option codes. Transport-layer protocols must be numbered and identified in the network layer header. Different network layers may have numerical identifiers in link layer headers. To take a concrete example from this book, consider the numerical identifiers in PPP. Interoperability requires that two implementations agree on PPP protocol numbers, LCP codes, LCP option numbers, as well as codes and option numbers for each network protocol transmitted across the link. Coordination of numerical assignments is handled by the Internet Assigned Numbers Authority (IANA). IANA is headquartered at the Information Sciences Institute at the University of Southern California.

Telcordia was formed in the 1984 AT&T divestiture. It was originally known as Bell Communications Research (Bellcore), the shared research arm of the Regional Bell Operating Companies. SAIC subsequently acquired Bellcore and renamed it Telcordia.

Bellcore was responsible for a great deal of the signaling specification that occurred in the post-divestiture telecommunications era. Although Bellcore technical reports were, in theory, only reports, products and services were often developed around them, and they have the force of standards.