X
X-Band
A portion of the radio frequency spectrum, 7 GHz and 8 GHz, used by military satellites.
X-ray Lithography
A lithographic process in which X-rays, rather than light or electron beams, are used to transfer circuit patterns to a silicon wafer. The advantage of X-rays is their shorter wavelengths, which reduce diffraction and yield greater resolution and finer line widths of features-which allows more transistors to be packed onto a chip.
X.121
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard that specifies the addressing conventions for any data terminal equipment (DTE) connected to an X.25 network.
X.21
A set of CCITT specifications for an interface between DTE and DCE for synchronous operation on public data networks. Includes connector, electrical, and dialing specifications.
X.21bis
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard that specifies the Physical-layer protocol for communication between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) on an X.25 network. X.21bis is nearly identical to RS-232.
X.25
A standard for packet-switched networks. It describes how data travels into and out of public data communications networks. Some examples in which X.25 networks are used include point-of-sale terminals, credit card verifications, and automatic teller machine transactions.
X.25/IP
Internet Protocol over X.25. A method of transporting IP packets on X.25 facilities when the circuit is established as an end-to-end X.25 connection.
X.25/T3POS
X.25/Transaction Processing Protocol for Point-of-Service. X.25/T3POS is a character-oriented, frame-formatted protocol designed for an X.25 packet-switched network. The protocol provides reliable and efficient data transactions between a host device and Data Terminal Equipment (DTE). The DTE is usually a client device communicating through an asynchronous port, while the host is a mainframe communicating by means of an X.25 packet network. The Lucent unit converts data arriving from the DTE to a format capable of being transmitted over a packet network. In addition, X.25/T3POS enables you to send data over the ISDN D channel while continuing to send traffic over both B channels.
X.29
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard that defines the interface for the exchange of control information and user data over a packet-switched network between data terminal equipment (DTE) and a packet assembler/disassembler (PAD).
X.3
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) recommendation that defines the user facilities available on all X.25 networks.
X.3 Profile
A complete set of X.3 parameters for data terminal equipment (DTE) on an X.25 network.
X.32
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard that defines the interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for devices connecting to a public data network by means of an ISDN link, a public switched telephone network (PSTN), or a circuit-switched public data network (CSPDN).
X.400
The ISO protocol for electronic mail that is expected to become widely accepted. Work is underway to make Internet mail systems interoperate with the X.400.
X.75
The International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard for connecting packet-switched networks.
XNS IDP
Xerox Networking System Internetwork Datagram Protocol
Xerox Network Standard (XNS)
The term used collectively to refer tot he suite of Internet protocols developed by researchers at Xerox Corporation. Although similar in spirit tot he DARPA Internet protocols, XNS uses different packet formats and terminology.
Xmodem
An error-correction protocol for modems. Modems that use Xmodem transmit data in 128-byte blocks. If a modem receives a block successfully, it returns a positive acknowledgment (ACK). If a modem detects an error, it sends back a negative acknowledgment (NAK), and the other modem resends the data.
A portion of the radio frequency spectrum, 7 GHz and 8 GHz, used by military satellites.
X-ray Lithography
A lithographic process in which X-rays, rather than light or electron beams, are used to transfer circuit patterns to a silicon wafer. The advantage of X-rays is their shorter wavelengths, which reduce diffraction and yield greater resolution and finer line widths of features-which allows more transistors to be packed onto a chip.
X.121
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard that specifies the addressing conventions for any data terminal equipment (DTE) connected to an X.25 network.
X.21
A set of CCITT specifications for an interface between DTE and DCE for synchronous operation on public data networks. Includes connector, electrical, and dialing specifications.
X.21bis
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard that specifies the Physical-layer protocol for communication between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) on an X.25 network. X.21bis is nearly identical to RS-232.
X.25
A standard for packet-switched networks. It describes how data travels into and out of public data communications networks. Some examples in which X.25 networks are used include point-of-sale terminals, credit card verifications, and automatic teller machine transactions.
X.25/IP
Internet Protocol over X.25. A method of transporting IP packets on X.25 facilities when the circuit is established as an end-to-end X.25 connection.
X.25/T3POS
X.25/Transaction Processing Protocol for Point-of-Service. X.25/T3POS is a character-oriented, frame-formatted protocol designed for an X.25 packet-switched network. The protocol provides reliable and efficient data transactions between a host device and Data Terminal Equipment (DTE). The DTE is usually a client device communicating through an asynchronous port, while the host is a mainframe communicating by means of an X.25 packet network. The Lucent unit converts data arriving from the DTE to a format capable of being transmitted over a packet network. In addition, X.25/T3POS enables you to send data over the ISDN D channel while continuing to send traffic over both B channels.
X.29
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard that defines the interface for the exchange of control information and user data over a packet-switched network between data terminal equipment (DTE) and a packet assembler/disassembler (PAD).
X.3
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) recommendation that defines the user facilities available on all X.25 networks.
X.3 Profile
A complete set of X.3 parameters for data terminal equipment (DTE) on an X.25 network.
X.32
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard that defines the interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for devices connecting to a public data network by means of an ISDN link, a public switched telephone network (PSTN), or a circuit-switched public data network (CSPDN).
X.400
The ISO protocol for electronic mail that is expected to become widely accepted. Work is underway to make Internet mail systems interoperate with the X.400.
X.75
The International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard for connecting packet-switched networks.
XNS IDP
Xerox Networking System Internetwork Datagram Protocol
Xerox Network Standard (XNS)
The term used collectively to refer tot he suite of Internet protocols developed by researchers at Xerox Corporation. Although similar in spirit tot he DARPA Internet protocols, XNS uses different packet formats and terminology.
Xmodem
An error-correction protocol for modems. Modems that use Xmodem transmit data in 128-byte blocks. If a modem receives a block successfully, it returns a positive acknowledgment (ACK). If a modem detects an error, it sends back a negative acknowledgment (NAK), and the other modem resends the data.
