Signalling Connection Control Part: Difference between revisions

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{{SS7stack}}{{distinguish|Skinny Client Control Protocol}}

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The '''Signalling Connection Control Part''' ('''SCCP''') is a [[network layer]]<ref>[http://www.itu.int/rec/T-REC-Q.1400/en/ ITU-T Recommendation Q.1400].</ref> protocol that provides extended [[routing]], [[flow control (data)|flow control]], segmentation, [[connection-oriented communications|connection-orientation]], and [[error correction]] facilities in [[Signaling System 7]] telecommunications networks. SCCP relies on the services of [[Message Transfer Part|MTP]] for basic routing and error detection.

==Published specification==

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==Routing facilities beyond MTP==

Although [[Message Transfer Part|MTP]] provides routing capabilities based uponon the [[Point Code]], SCCP allows routing using a [[Point Code]] and [[Subsystem number]] or a [[Global Title]].

A Point Code is used to address a particular node on the network, whereas a [[Subsystem number]] addresses a specific application available on that node. SCCP employs a process called [[Global Title Translation]] to determine [[Point Code]]s from [[Global Title]]s so as to instruct [[Message Transfer Part|MTP]] on where to route messages.

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==Protocol classes==

SCCP provides 4 classes of protocol tofor its applications:

* '''Class 0''': Basic connectionless.

* '''Class 1''': Sequenced connectionless.

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===Class 0: Basic connectionless===

The SCCP Class 0 protocol class is the most basic of the SCCP protocol classes. Network Service Data Units passed by higher layers to the SCCP in the originating node are delivered by the SCCP to higher layers in the destination node. They are transferred independently of each other. Therefore, they may be delivered to the SCCP user out-of-sequence. Thus, this protocol class corresponds to a pure [[connectionless protocol|connectionless network service]]. As a connectionless protocol, no network connection is established between the sender and the receiver.

===Class 1: Sequenced connectionless===

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Class 3 service builds upon Class 2, but also allows for expedited (urgent) messages to be sent and received, and for errors in sequencing (segment re-assembly) to be detected and for SCCP to restart a connection should this occur.

==Transport over IP Networksnetworks==

In the [[SIGTRAN]] suite of protocols, there are two primary methods of transporting SCCP applications across [[Internet Protocol]] networks: SCCP can be transported indirectly using the [[M3UA|''MTP level 3 User Adaptation'' protocol (M3UA)]], a protocol which provides support for users of [[Message Transfer Part|MTP-3]]—including SCCP. Alternatively, SCCP applications can operate directly over the ''SCCP User Adaptation'' protocol (SUA) which is a form of modified SCCP designed specifically for use in IP networking.

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== References ==

<references/>

== External links ==

[[Category:ITU-T recommendations]]