List of ITU-T V-series recommendations

Source: Wikipedia, the free encyclopedia.

The ITU-T V-Series Recommendations on Data communication over the telephone network specify the protocols that govern approved modem communication standards and interfaces.[1]

Note: the bis and ter suffixes are ITU-T standard designators of successive iterations of a standard (bis and ter are derived from the Latin for "twice" and "thrice").

General standards

Applies to V.1–V.9

  • V.1 is an ITU-T recommendation, entitled Equivalence between binary notation symbols and the significant conditions of a two-condition code.
  • V.2 is an ITU-T recommendation, approved in November 1988, titled Power levels for data transmission over telephone lines.
  • V.4 is an ITU-T recommendation, approved in November 1988, titled General structure of signals of International Alphabet No. 5 code for character oriented data transmission over public telephone networks.
  • V.5 was an ITU-T recommendation, approved in November 1988, titled Standardization of data signalling rates for synchronous data transmission in the general switched telephone network. It has been withdrawn since.
  • V.6 was an ITU-T recommendation, approved in November 1988, titled Standardization of data signalling rates for synchronous data transmission on leased telephone-type circuits. It has been withdrawn since.
  • V.7 is an ITU-T recommendation, approved in November 1988, titled Definitions of terms concerning data communication over the telephone network.
  • V.8 is an ITU-T recommendation, first approved in September 1994, titled Procedures for starting sessions of data transmission over the public switched telephone network. It has been superseded three times. The current version was approved in November 2000.
    • V.8bis is an ITU-T recommendation, first approved in August 1996, titled Procedures for the identification and selection of common modes of operation between data circuit-terminating equipments (DCEs) and between data terminal equipments (DTEs) over the public switched telephone network and on leased point-to-point telephone-type circuits. It has been superseded twice. The current version was approved in November 2000.

Interfaces and voiceband modems

Applies to V.10–V.34

Ad hoc standards

In order to gain first-mover advantage, many modem companies introduced models based on upcoming V-series standards before they reached final ratification. In other cases, companies introduced non-standard systems but gave them ITU-like names.

  • V.32terbo, or V.32ter for short, was a 19.2 kbit/s standard introduced by
    AT&T Paradyne
    . It was based on V.32bis and did little other than increase the data rate. V.32ter is compatible with V.32bis at speeds of 14.4 kbit/s and lower, but it is not compatible with V.34 at 19.2.
  • V.FC, short for V.Fast Class and sometimes referred to as V.FAST, was developed by Hayes and Rockwell to introduce a 28.8 kbit/s standard while the V.34 efforts dragged on. V.FC was not compatible with V.34, although most V.34 modems could support V.FC, notably, those using Rockwell chipsets.[8]

Wideband modems

Applies to V.35–V.39

  • V.35 is an ITU-T standard located on layer 1 on the OSI model. Max speed is 2 Mbit/s and synchronous only. Withdrawn ITU-T recommendation for 48 kbit/s data transmission over wideband circuits. The physical and electrical characteristics of this interface are now specified in ITU-T recommendation V.11.
  • V.36 is an ITU-T standard located on layer 2 on the OSI model called Modems For Synchronous Data Transmission Using 60–108 kHz Group Band Circuits.

Error control and data compression

Applies to V.40–V.49

  • V.41 is a code-independent error control system. It defines the ITU-T standard CRC-16 polynomial as x16 + x12 + x5 + 1
  • V.42 is an error correction protocol. Its function is to allow the receiver to immediately request re-transmission of any lost data packets. However, it does not guarantee how quickly the error-free data will be delivered to the receiving end. V.42 is generally included in dialup modems. It also defines the ITU-T standard CRC-32 polynomial as x32+x26+x23+x22+x16+x12+x11+x10+x8+x7+x5+x4+x2+x+1, and includes the
    LAPM
    framing protocol.
  • V.44 is based on LZJH (Lempel-Ziv-Jeff-Heath) adaptive data compression developed by Hughes Electronics for its DirecPC satellite Internet, and incorporated into the v.92 dial-up modem standard. V.44 offers somewhat better compression performance for certain types of data than the V.42bis standard, on average allowing 15% greater throughput. For instance, a 53.3 kbit/s connection with V.44 can transmit up to 53.3×6 = 320 kbit/s using pure text. In reality, the overall data rate rarely exceeds 3:1 compression (~150 kbit/s). The compression tends to get better and worse over time due to noise on the line, or due to the transfer of already-compressed files (ZIP files, JPEG images, MP3 audio, MPEG video). At some points the modem will be sending compressed files at 53 kbit/s, uncompressed files at 160 kbit/s, and pure text at 320 kbit/s, or any value in between.[9][10]

Simultaneous transmission of data and other signals

Applies to V.60–V.99

Interworking with other networks

Applies to V.100–V.199

Interface layer specifications for data communication

Applies to V.200–V.249

  • V.230 is an ITU-T recommendation, approved in November 1988, titled General data communications interface layer 1 specification.

Control procedures

Applies to V.250–V.299

  • V.250, originally known as V.25ter, is an ITU-T recommendation for serial asynchronous automatic dialing and control.[11]

Digital circuit modems

Applies to V.300–V.399

  • V.300 is an ITU-T recommendation, first approved in January 1997, titled A 128 (144) kbit/s data circuit-terminating equipment standardized for use on digital point-to-point leased circuits.

See also

References

  1. ^ ITU-T (2006-09-29). "Data communication over the telephone network". ITU. Retrieved 2008-03-02.
  2. ^ "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". www.itu.int. Retrieved 2020-08-20.
  3. ^ "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". www.itu.int. Retrieved 2020-08-20.
  4. ^ Vendors rallying around high-speed modem scheme
  5. ^ "V.34: a modem operating at data signalling rates of up to 28 800 bit/s for use on the general switched telephone network and on leased point-to-point 2-wire telephone-type circuits". www.itu.int. Retrieved 2020-07-05.
  6. ^ "V.34: A modem operating at data signalling rates of up to 33 600 bit/s for use on the general switched telephone network and on leased point-to-point 2-wire telephone-type circuits". www.itu.int. Retrieved 2020-07-05.
  7. ^ "V.34: A modem operating at data signalling rates of up to 33 600 bit/s for use on the general switched telephone network and on leased point-to-point 2-wire telephone-type circuits". www.itu.int. Retrieved 2020-07-05.
  8. ^ "V.FC"
  9. ^ Willdig, Karl; Patrik Chen (August 1994). "What You Need to Know about Modems". Archived from the original on 2007-01-04. Retrieved 2008-03-02.
  10. ^ Mitronov, Pavel (2001-06-29). "Modem compression: V.44 against V.42bis". Pricenfees.com. Archived from the original on 2017-02-02. Retrieved 2008-03-02.
  11. ^ Supplement (04/95) to Recommendation V.25ter - Serial asynchronous automatic dialling and control

External links

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