The ITU Telecommunication Standardization Sector (ITU-T) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU); it coordinates standards for telecommunications.
The standardization work of ITU dates back to 1865, with the birth of the International Telegraph Union. It became a United Nations specialized agency in 1947, and the International Telegraph and Telephone Consultative Committee (CCITT, from French: Comité Consultatif International Téléphonique et Télégraphique) was created in 1956. It was renamed ITU-T in 1993.[1]
ITU has been an intergovernmental public-private partnership organization since its inception and now has a membership of 191 countries (Member States) and over 700 public and private sector companies as well as international and regional telecommunication entities, known as Sector Members and Associates, which undertake most of the work of the Sector.[2]
ITU-T has a permanent secretariat, the Telecommunication Standardization Bureau (TSB), based at the ITU HQ in Geneva, Switzerland. The elected Director of the Bureau is Malcolm Johnson of the UK. Johnson was elected by the ITU Membership to the directorship for a 4-year term in November 2006 and was reelected for a second term starting January 2011.
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The ITU-T mission is to ensure the efficient and timely production of standards covering all fields of telecommunications on a worldwide basis, as well as defining tariff and accounting principles for international telecommunication services.[3]
The international standards that are produced by the ITU-T are referred to as "Recommendations" (with the word ordinarily capitalized to distinguish its meaning from the ordinary sense of the word "recommendation"), as they become mandatory only when adopted as part of a national law.
Since the ITU-T is part of the ITU, which is a United Nations specialized agency, its standards carry more formal international weight than those of most other standards development organizations that publish technical specifications of a similar form.[4]
Although the ITU itself dates back to 1865,[1] the formal standardization processes are more recent.
Two consultative committees were created by the ITU’s 1925 Paris conference to deal with the complexities of the international telephone services (known as CCIF, as the French acronym) and long-distance telegraphy (CCIT).[5]
In view of the basic similarity of many of the technical problems faced by the CCIF and CCIT, a decision was taken in 1956 to merge them to become the single International Telegraph and Telephone Consultative Committee (CCITT, in the French acronym).[5]
In 1992, the Plenipotentiary Conference (the top policy-making conference of ITU) saw a reform of ITU, giving the Union greater flexibility to adapt to an increasingly complex, interactive and competitive environment. It was at this time that CCITT was renamed the Telecommunication Standardization Sector (ITU-T), as one of three Sectors of the Union alongside the Radiocommunication Sector (ITU-R) and the Telecommunication Development Sector (ITU-D).[6]
Historically, the Recommendations of the CCITT were presented to four-yearly plenary assemblies for endorsement, and the full set of Recommendations were published after each plenary assembly. However, the delays in producing texts, and translating them into other working languages, did not suit the fast pace of change in the telecommunications industry.[7]
The rise of the personal computer industry in the early 1980s created a new common practice among both consumers and businesses of adopting "bleeding edge" communications technology even if it was not yet standardized. Thus, standards organizations had to put forth standards much faster, or find themselves ratifying de facto standards after the fact.
The ITU-T now operates under much more streamlined processes. The time between an initial proposal of a draft document by a member company and the final approval of a full-status ITU-T Recommendation can now be as short as a few months (or less in some cases). This makes the standardization approval process in the ITU-T much more responsive to the needs of rapid technology development than in the ITU's historical past.[8] New and updated Recommendations are published on an almost daily basis, and much of the library of over 3,270 Recommendations is now free of charge online.[9][10][11] (Specifications jointly maintained by the ITU-T and ISO/IEC are not free.[12])
ITU-T has moreover tried to facilitate cooperation between the various forums and standard-developing organizations (SDOs). This collaboration is necessary to avoid duplication of work and the consequent risk of conflicting standards in the market place.[13]
In the work of standardization, ITU-T cooperates with other SDOs, e.g., the International Organization for Standardization (ISO) and the Internet Engineering Task Force (IETF).[14]
Most of the work of ITU-T is carried out by its Sector Members and Associates, while the Telecommunication Standardization Bureau (TSB) is the executive arm of ITU-T and coordinator for a number of workshops and seminars to progress existing work areas and explore new ones. The events cover a wide array of topics in the field of information and communication technologies (ICT) and attract high-ranking experts as speakers, and attendees from engineers to high-level management from all industry sectors.[15]
The technical work, the development of Recommendations, of ITU-T is managed by Study Groups (SGs). The people involved in these SGs are experts in telecommunications from all over the world. There are currently 13 SGs. Study groups meet face to face according to a calendar issued by the TSB.[16] SGs are augmented by Focus Groups (FGs), an instrument created by ITU-T, providing a way to quickly react to ICT standardization needs and allowing great flexibility in terms of participation and working methods. The key difference between SGs and FGs is that the latter have greater freedom to organize and finance themselves, and to involve non-members in their work. Focus Groups can be created very quickly, are usually short-lived and can choose their own working methods, leadership, financing, and types of deliverables.[17] Recent examples include work on Next Generation Networking, Internet Protocol Television (IPTV) and digital identity management.[18]
The “Alternative Approval Process” (AAP) is a fast-track approval procedure that was developed to allow standards to be brought to market in the timeframe that industry now demands.
This dramatic overhaul of standards-making by streamlining approval procedures was implemented in 2001 and is estimated to have cut the time involved in this critical aspect of the standardization process by 80 to 90 per cent. This means that an average standard which took around four years to approve and publish until the mid nineties, and two years until 1997, can now be approved in an average of two months, or as little as five weeks.
Besides streamlining the underlying procedures involved in the approval process, an important contributory factor to the use of AAP is electronic document handling. Once the approval process has begun the rest of the process can be completed electronically, in the vast majority of cases, with no further physical meetings.
The introduction of AAP also formalizes public/private partnership in the approval process by providing equal opportunities for both Sector Members and Member States in the approval of technical standards.
Once the text of a draft Recommendation prepared by SG experts is considered mature, it is submitted for review to an SG meeting. If agreed by the meeting it is given Consent. This means that the SG has given its consent that the text is sufficiently mature to initiate a final review process leading to approval of the draft Recommendation.
After this Consent has been achieved, TSB announces the start of the AAP procedure by posting the draft text to the ITU-T web site and calling for comments. This gives the opportunity for all members to review the text. This phase, called Last Call, is a four-week period in which comments can be submitted by Member States and Sector Members.
If no comments other than editorial corrections are received, the Recommendation is considered approved since no issues were identified that might need any further work. However, if there are any comments, the SG chairman, in consultation with TSB, sets up a comment resolution process by the concerned experts. The revised text is then posted on the web for an Additional Review period of three weeks.
Similar to the Last Call phase, in Additional Review the Recommendation is considered as approved if no comments are received. If comments are received, it is apparent that there are some issues that still need more work, and the draft text and all comments are sent to the next Study Group meeting for further discussion and possible approval.[19]
Those Recommendations considered as having policy or regulatory implications are approved through what is known as the “Traditional Approval Process” (TAP), which allows a longer period for reflection and commenting by Member States. TAP Recommendations are also translated into the six working languages of ITU (Arabic, Chinese, English, French, Russian and Spanish).[20]
ITU-T Recommendations are the names given to telecommunications and computer protocol specification documents published by ITU-T.
Many of the Recommendations that define OSI are also ISO standards.
Standards for Internet protocols are typically developed in the IETF, and standards for mobile telephone systems are developed in ETSI and other forums.
ITU-T issues Recommendations that have names like X.500, where X is the series and 500 is an identifying number. When a Recommendation is updated, it will (mostly) keep the same number, so the year of issue may be necessary to identify a specific version of a Recommendation. The term "X.500" is used both to refer to the specific X.500 Recommendation, and to the entire family of Recommendations named X.5xx, where the specific X.500 Recommendation forms the introduction and overview to the set.
| Series | Description |
|---|---|
| A | Organization of the work of ITU-T |
| B | Means of expression: definitions, symbols, classification |
| C | General telecommunication statistics |
| D | General tariff principles |
| E | Overall network operation, telephone service, service operation and human factors |
| F | Non-telephone telecommunication services |
| G | Transmission systems and media, digital systems and networks |
| H | Audiovisual and multimedia systems |
| I | Integrated services digital network |
| J | Cable networks and transmission of television, sound programme and other multimedia signals |
| K | Protection against interference |
| L | Construction, installation and protection of cables and other elements of outside plant |
| M | Telecommunication management, including TMN and network maintenance |
| N | Maintenance: international sound programme and television transmission circuits |
| O | Specifications of measuring equipment |
| P | Telephone transmission quality, telephone installations, local line networks |
| Q | Switching and signalling |
| R | Telegraph transmission |
| S | Telegraph services terminal equipment |
| T | Terminals for telematic services |
| U | Telegraph switching |
| V | Data communication over the telephone network |
| X | Data networks, open system communications and security |
| Y | Global information infrastructure, Internet protocol aspects and next-generation networks |
| Z | Languages and general software aspects for telecommunication systems |
G Series Recommendations
Transmission systems and media, digital systems and networks
| Specification Range | Specification Type |
|---|---|
| G.100 - G.199 | INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS |
| G.200 - G.299 | GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIERTRANSMISSION SYSTEMS |
| G.300 - G.399 | INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES |
| G.400 - G.449 | GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES |
| G.450 - G.499 | COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY |
| G.600 - G.699 | TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS |
| G.700 - G.799 | DIGITAL TERMINAL EQUIPMENTS |
| G.800 - G.899 | DIGITAL NETWORKS |
| G.900 - G.999 | DIGITAL SECTIONS AND DIGITAL LINE SYSTEM |
| G.1000 - G.1999 | QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS |
| G.6000 - G.6999 | TRANSMISSION MEDIA CHARACTERISTICS |
| G.7000 - G.7999 | DATA OVER TRANSPORT – GENERIC ASPECTS |
| G.8000 - G.8999 | PACKET OVER TRANSPORT ASPECTS |
| G.8000 - G.8099 | Ethernet over Transport aspects |
| G.8100 - G.8199 | MPLS over Transport aspects |
| G.8200 - G.8299 | Quality and availability targets |
| G.8600 - G.8699 | Service Management |
| G.9000 - G.9999 | ACCESS NETWORKS |
Y Series Recommendations
Global Information Infrastructure, Internet Protocol Aspects And Nextgeneration Networks
| Specification Range | Specification Type |
|---|---|
| GLOBAL INFORMATION INFRASTRUCTURE | |
| Y.100–Y.199 | General |
| Y.200–Y.299 | Services, applications and middleware |
| Y.300–Y.399 | Network aspects |
| Y.400–Y.499 | Interfaces and protocols |
| Y.500–Y.599 | Numbering, addressing and naming |
| Y.600–Y.699 | Operation, administration and maintenance |
| Y.700–Y.799 | Security |
| Y.800–Y.899 | Performances |
| INTERNET PROTOCOL ASPECTS | |
| Y.1000–Y.1099 | General |
| Y.1100–Y.1199 | Services and applications |
| Y.1200–Y.1299 | Architecture, access, network capabilities and resource management |
| Y.1300–Y.1399 | Transport |
| Y.1400–Y.1499 | Interworking |
| Y.1500–Y.1599 | Quality of service and network performance |
| Y.1600–Y.1699 | Signalling |
| Y.1700–Y.1799 | Operation, administration and maintenance |
| Y.1800–Y.1899 | Charging |
| NEXT GENERATION NETWORKS | |
| Y.2000–Y.2099 | Frameworks and functional architecture models |
| Y.2100–Y.2199 | Quality of Service and performance |
| Y.2200–Y.2249 | Service aspects: Service capabilities and service architecture |
| Y.2250–Y.2299 | Service aspects: Interoperability of services and networks in NGN |
| Y.2300–Y.2399 | Numbering, naming and addressing |
| Y.2400–Y.2499 | Network management |
| Y.2500–Y.2599 | Network control architectures and protocols |
| Y.2700–Y.2799 | Security |
| Y.2800–Y.2899 | Generalized mobility |
In addition to the ITU-T Recommendations, which have non-mandatory status until they are adopted in national laws, ITU-T is also the custodian of a binding international treaty, the International Telecommunication Regulations. The ITRs go back to the earliest days of the ITU when there were two separate treaties, dealing with telegraph and telephone. The ITRs were adopted, as a single treaty, at the World Administrative Telegraphy and Telephone Conference held in Melbourne, 1988 (WATTC-88).[21]
In line with the current Constitution and Convention of ITU, the ITRs can be amended through a World Conference on International Telecommunications (WCIT), and the next is scheduled for 2012. Before then a process of review of the ITRs, which began in 1998, will continue.[22]
The ITRs comprise ten articles which deal, inter alia, with the definition of international telecommunication services, cooperation between countries and national administrations, safety of life and priority of telecommunications and charging and accounting principles. The adoption of the ITRs in 1988 is often taken as the start of the wider liberalization process in international telecommunications, though a few countries, including United States and United Kingdom, had made steps to liberalize their markets before 1988.[23]
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