ITU-T

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ITU-T is the telecom standardization organization, previously known as CCITT, of the International Telecommunication Union (ITU). It issues recommendations that have names like X.500, where X is the series and 500 is a serial number.

See ITU-T's own website, http://www.itu.int/ITU-T/

Significant ITU-T series and recommendations are:

  • 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
    • E.123 Notation for national and international telephone numbers
    • E.163 Numbering plan for the international telephone service
    • E.164 The international public telecommunication numbering plan
      • Supplement 2 - Number Portability
  • F - Non-telephone telecommunication services
  • G - Transmission systems and media, digital systems and networks
  • H - Audiovisual and multimedia systems
    • H.225.0 Also known as RTP
    • H.261 Video compression standard, circa 1991
    • H.263 Video compression standard, circa 1995
    • H.263v2 (a.k.a. H.263+) Video compression standard, circa 1998
    • H.323 Packet-based multimedia communications systems
      • Annex D - Real-time facsimile over H.323 systems
      • Annex G - Text conversation and Text SET
      • Annex J - Security for H.323 Annex F
      • Annex K - HTTP based service control transport channel in H.323
      • Annex M.1 - Tunnelling of signalling protocol (Qsig) in H.323
      • Annex M.2 - Tunneling of signalling protocol (Isup) in H.323
    • H.332 H.323 extended for loosely coupled conferences
  • I - Integrated services digital network (ISDN)
  • J - 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 - TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits
  • 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
    • V.1 Equivalence between binary notation symbols and the significant conditions of a two-condition code
    • V.24 List of definitions for interchange circuits between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) - equivalent to EIA RS 232
    • V.32 A family of 2-wire, duplex modems operating at data signalling rates of up to 9600 bit/s for use on the general switched telephone network and on leased telephone-type circuits
    • V.32bis A duplex modem operating at data signalling rates of up to 14 400 bit/s for use on the general switched telephone network and on leased point-to-point 2-wire telephone-type circuits
    • V.42bis Data compression procedures for data circuit-terminating equipment (DCE) using error correction procedures
    • V.90 A digital modem and analogue modem pair for use on the Public Switched Telephone Network (PSTN) at data signalling rates of up to 56 000 bit/s downstream and up to 33 600 bit/s upstream
  • X - Data networks and open system communication
    • X.1 International user classes of service in, and categories of access to, public data networks and Integrated Services Digital Networks (ISDNs)
    • X.21 Interface between Data Terminal Equipment and Data Circuit-terminating Equipment for synchronous operation on public data networks
    • X.25 Interface between Data Terminal Equipment (DTE) and Data Circuit-terminating Equipment (DCE) for terminals operating in the packet mode and connected to public data networks by dedicated circuit
    • X.110 International routing principles and routing plan for public data networks
    • X.121 International numbering plan for public data networks
    • X.200 Information technology - Open Systems Interconnection - Basic Reference Model: The basic model
    • X.208 Specification of Abstract Syntax Notation One (ASN.1)
    • X.209 Specification of Basic Encoding Rules for Abstract Syntax Notation One (ASN.1)
    • X.400 Message handling services: Message handling system and service overview
    • X.500 Information technology - Open Systems Interconnection - The Directory: Overview of concepts, models and services Common text with ISO/IEC
    • X.509 Information technology - Open Systems Interconnection - The Directory: Public-key and attribute certificate frameworks
  • Y - Global information infrastructure and Internet protocol aspects
  • Z - Languages and general software aspects for telecommunication systems