Web ProForum Tutorials medical-site.info Copyright © Signaling System 7 ( SS7) is an architecture for performing out-of-band signaling in support of the. SS7 is a set of telephony signaling protocols that are This tutorial provides an overview of Signaling System. No. 7 (SS7) network architecture and protocols. SS7 Tutorial. Overview. Common Channel Signaling System No. 7 (i.e., SS7 or C7) is a global standard for telecommunications defined by the.
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To understand the SS7 protocol, it is helpful to understand the concept of protocol It is beyond the scope of this tutorial to fully investigate the OSI model. node in the SS7 network (DPC, SSN). Instead, it is an alias for such an address that needs to be translated into an SS7 network address. With that definition out. The SS7 is held together by a digital sister of the switch known as a Sig- nalling Transfer Point (STP). The requirements of voice switching and digital transfer are .
Printed in the USA. Common Channel Signaling System Figure 1. The SS7 standard defines the procedures and proto- and billing. The two forms of signaling that you are col by which network elements in the public switched most familiar with used by Patton products are: Figure 1.
The SS7 network and protocol are used for: Signaling However the principal disadvantage of ISDN-PRI is its Everything in the telecommunications network is use of Associated Signaling mode, which only works based on signaling—call setup, connection, teardown, with directly trunked switches. Associated Signaling mode. Associated Signaling With this type of signaling, the signaling link directly Signaling Links Common parallels associated voice trunks.
Thus, dedicated channel signaling links must be provisioned between every intercon- SS7 messages are 56 or 64 kbps bidirectional chan- nected switch. See Figure Signaling occurs out-of-band on dedi- Figure Associated Signaling cated channels rather than in-band on voice channels. SS7 is a form of common channel signaling, that pro- vides intelligence to the network, and allows quicker call setup and teardown—saving time and money.
Compared to in-band signaling, out-of-band signal- ing provides: Although used in the SS7 network, it is not pre- ty to read a Point Code and determine if the message ferred. Figure Non-Associated Signaling Each signaling point in the SS7 network is uniquely identified by a numeric point code.
Point codes are car- ried in signaling messages exchanged between signal- ing points to identify the source and destination of each message. Each signaling point uses a routing table to select the appropriate signaling path for each message. There are three kinds of signaling points in the SS7 network see Figure 6: Quasi-associated sig- naling is the preferred signaling mode for SS7. SS7 Signaling Points Figure Each SP is identified by a unique from a subscriber line to SS7 signaling messages.
All SPs signaling points are connected using typi- cally pairs of Links. Only messages originating from or destined to the signaling end point Messages are not originated by an STP. STPs switch SS7 messages between signaling points. Gateway STPs serve as the interface into another net- Type B—Bridge Links used to connect work and they can provide protocol conversion. STPs also provide traffic and usage measurements.
The distinction An SCP provides application access. It is an interface between a B link and a D link is rather arbitrary.
For to applications such as databases. An SCP communicates with applications using primi- tives. A primitive is an interface that provides access from one level of a protocol to another level. The protocol used to access and interface a database application is TCAP.
E links provide an alternate signaling path if an signaling point due to link failure s. E may also be deployed in pairs to improve reliability; links are not usually provisioned unless the benefit of unlike STPs, however, mated SCPs are not intercon- a marginally higher degree of reliability justifies the nected by signaling links.
Note that SCPs may also be deployed in pairs to improve reliability. In networks without STPs. Secondary STPs within the same network are connected via a quad of D links. F links directly connect signaling points. A C link is used only when an STP has no other route available to a destination signaling point due to link failure s. F links are not usually used in networks with STPs. Like most modern protocols. The letter designation allows differing congestion and recovery treatment.
It ensures that messages can be delivered between signaling points across the SS7 network regardless of whether they are directly connected. SS7 Protocol Layers The SS7 protocol is designed to both facilitate these functions and to maintain the network over which they are provided. All links use the same physical connections. It includes such capabilities as node addressing.
Signaling links utilize DS—0 channels and carry raw signaling data at a rate of 56 kbps or 64 kbps 56 kbps is the more common implementation. It incorporates such capabilities as error checking. It ensures that the two end points of a signaling link can reliably exchange signaling messages. GT routing allows SPs to use alias addressing to save them from having to maintain overly large physical address tables. The MTP can only receive and deliver messages from a node as a whole.
Examples of subsystems are call processing. The first of these is the capability to address applications within a signaling point. Despite its name.
In the North American version of SS7. The SCCP allows these subsystems to be addressed explicitly. While MTP network-management messages and basic call-setup messages are addressed to a node as a whole. A physical address consists of a point code and an application reference called a subsystem number SSN. Enhanced routing is called global title GT routing.
A GT is a directory number that serves as an alias for a physical network address. It keeps SPs from having overly large routing tables that would be difficult to provision and maintain. MD USA phone: A logical group of links between two SP is called a linkset.
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