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Technical Standard: Networking Services (XNS), Issue 5.2 Draft 2.0
Copyright © 1999 The Open Group


abortive release

An abrupt termination of a transport connection, which may result in the loss of data.

asynchronous mode

The mode of execution in which transport service functions do not wait for specific asynchronous events to occur before returning control to the user, but instead return immediately if the event is not pending.


Connectionless (a deprecated synonym for "connectionless-mode").


Connection-oriented (a deprecated synonym for "connection-mode").

connection establishment

The phase in connection-mode that enables two transport users to create a transport connection between them.


A mode of transfer where a logical link is established between two endpoints. Data is passed over this link by a sequenced and reliable way.


A mode of transfer where different units of data are passed through the network without any relationship between them.

connection release

The phase in connection-mode that terminates a previously established transport connection between two users.


A unit of data transferred between two users of the connectionless-mode service.

data transfer

The phase in connection-mode or connectionless-mode that supports the transfer of data between two transport users.


The Domain Name System defined in RFC 1035. This system provides translation between host names and Internet addresses.


Event Management

expedited data

Data that are considered urgent. The specific semantics of expedited data are defined by the transport provider that provides the transport service.


Expedited Transport Service Data Unit

expedited transport service data unit

The amount of expedited user data, the identity of which is preserved from one end of a transport connection to the other (that is, an expedited message).


Fully-qualified domain name.

host byte order

The implementation-dependent byte order supported by the local host machine (see the Glossary entry for "Network Byte Order"). Functions are provided to convert 16 and 32-bit values between network and host byte order (see htonl()).


An entity that initiates a connection request.


International Organization for Standardization


An item marked "LEGACY" in this specification means that it is being retained for compatibility with older applications, but has limitations which makes it inappropriate for developing portable applications. New applications should use alternative means of obtaining equivalent functionality.

network byte order

The byte order in which the most significant byte of a multibyte integer value is transmitted first. This byte order is the standard byte order for Internet protocols.

network host database

A database whose entries define the names and network addresses of host machines. See gethostent().

network net database

A database whose entries define the names and network numbers of networks. See getnetent().

network protocol database

A database whose entries define the names and protocol numbers of protocols. See getprotoent().

network service database

A database whose entries define the names and local port numbers of services. See getservent().

orderly release

A procedure for gracefully terminating a transport connection with no loss of data.


Open System Interconnection


An entity with whom an initiator wishes to establish a transport connection.


A communications endpoint associated with a file descriptor that provides communications services using a specified communications protocol.


System V Interface Definition

synchronous mode

The mode of execution in which transport service functions wait for specific asynchronous events to occur before returning control to the user.


Transport Connection


Transmission Control Protocol


Transport Level Interface

transport address

The identifier used to differentiate and locate specific transport endpoints in a network.

transport connection

The communication circuit that is established between two transport users in connection-mode.

transport endpoint

The communication path, which is identified by a file descriptor, between a transport user and a specific transport provider. A transport endpoint is called passive before, and active after, a relationship is established, with a specific instance of this transport provider, identified by the TSAP.

transport provider identifier

A character string used by the function to identify the transport service provider.

transport service access point

A TSAP is a uniquely identified instance of the transport provider. A TSAP is used to identify a transport user on a certain endsystem. In connection-mode, a single TSAP may have more than one connection established to one or more remote TSAPs; each individual connection then is identified by a transport endpoint at each end.

transport service data unit

A unit of data transferred across the transport service with boundaries and content preserved unchanged. A TSDU may be divided into sub-units passed between the user and XTI. The T_MORE flag is set in all but the last fragment of a TSDU sequence constituting a TSDU. The T_MORE flag implies nothing about how the data is handled and passed to the lower level by the transport provider, and how they are delivered to the remote user.

transport service provider

A transport protocol providing the service of the transport layer.

transport service user

An abstract representation of the totality of those entities within a single system that make use of the transport service.


See Transport Service Access Point


See Transport Service Data Unit


User Datagram Protocol

user application

The set of user programs, implemented as one or more process(es) in terms of UNIX semantics, written to realise a task, consisting of a set of user required functions.


X/Open Transport Interface


X/Open Event Management Interface

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