Connectionless-mode Network Service (CLNS) or simply Connectionless Network Service is an
OSI network layer datagram service
A datagram is a basic transfer unit associated with a packet-switched network. Datagrams are typically structured in header and payload sections. Datagrams provide a connectionless communication service across a packet-switched network. The de ...
that does not require a circuit to be established before data is transmitted, and routes messages to their
destinations
:''This article covers a Girl Scouts of the USA, Girl Scouts event: for vacation destinations see Vacation spot (disambiguation)''
Girl Scout Destinations, formerly Wider Opportunities or Wider Ops, are events for individual Girl Scouts (ages 11 ...
independently of any other messages.
["Section 3: Definition of the Connectionless-Mode Service"]
''ITU-T Recommendation X.213: Open Systems Interconnection – Network service definition'', International Telecommunication Union, October 2001
, Chapter 2, Section 1 in ''IS-IS Network Design Solutions'', Cisco Press, 7 February 2002, As such it is a "
best-effort" rather than a "
reliable" delivery service. CLNS is not an
Internet
The Internet (or internet) is the Global network, global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a internetworking, network of networks ...
service, but provides capabilities in an
OSI network environment similar to those provided by the
Internet protocol suite
The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suite are ...
. The service is specified in ISO/IEC 8348, the OSI Network Service Definition (which also defines the connection-oriented service, CONS.)
Connectionless-mode Network Protocol
Connectionless-mode Network Protocol (CLNP) is an OSI protocol deployment. CLNS is the service provided by the Connectionless-mode Network Protocol (CLNP). From August 1990 to April 1995 the
NSFNET
The National Science Foundation Network (NSFNET) was a program of coordinated, evolving projects sponsored by the National Science Foundation (NSF) from 1985 to 1995 to promote advanced research and education networking in the United States. The ...
backbone supported CLNP in addition to
TCP/IP
The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suite are ...
. However, CLNP usage remained low compared to TCP/IP.
Transport Protocol Class 4 (TP4) in conjunction with CLNS
CLNS is used by ISO
Transport Protocol
Transport (in British English) or transportation (in American English) is the intentional movement of humans, animals, and goods from one location to another. Modes of transport include air, land ( rail and road), water, cable, pipelines, a ...
Class 4 (TP4), one of the five transport layer protocols in the OSI suite. TP4 offers error recovery, performs segmentation and reassembly, and supplies multiplexing and demultiplexing of data streams over a single virtual circuit. TP4 sequences PDUs and retransmits them or re-initiates the connection if an excessive number are unacknowledged. TP4 provides reliable transport service and functions with either connection-oriented or connectionless network service. TP4 is the most commonly used of all the OSI transport protocols and is similar to the
Transmission Control Protocol
The Transmission Control Protocol (TCP) is one of the main communications protocol, protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP). Therefore, th ...
(TCP) in the
Internet protocol suite
The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suite are ...
.
Protocols providing CLNS
Several protocols provide the CLNS service:
[
* Connectionless-mode Network Protocol (CLNP), as specified in ITU-T Recommendation X.233.
* End System-to-Intermediate System (ES-IS), a routing exchange protocol for use in conjunction with the protocol for providing the CLNS (ISO 9542).
* Intermediate System-to-Intermediate System (IS-IS), an intradomain routing exchange protocol used in both the OSI and Internet environments (ISO/IEC 10589 and RFC 1142).
* Interdomain Routing Protocol (IDRP), the OSI equivalent of BGP.
* Signalling Connection Control Part (SCCP), as specified in ITU-T Recommendation Q.711''ITU-T Recommendation Q.711: Specifications of Signalling System No. 7 – Signalling connection control part (SCCP)'']
International Telecommunication Union, March 2001 is a
Signaling System 7
Signalling System No. 7 (SS7) is a set of telephony signaling protocols developed in the 1970s that is used to setup and teardown telephone calls on most parts of the global public switched telephone network (PSTN). The protocol also performs ...
protocol.
See also
*
X.25 protocol suite, an OSI Connection Oriented Network Service (CONS)
References
{{Reflist
External links
What is CLNS?- a brief introduction by Ivan Pepelnjak
ITU-T recommendations
OSI protocols
Network layer protocols