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Introduction : SS7

Communications networks connect terminal equipment by using nodes.  The nodes have to
exchange signaling information in order to control the setup of connections.

The signaling link can be viewed as a tunnel which connects two exchanges and accepts and conveys all signaling information.

Signaling information transfer is made possible by sending messages. A message is an information block whose structure and meaning of the single elements in the block are defined by specifications.

Components of a Signaling Network

  • signaling end points (SEP)
  • signaling transfer points (STP)
  • signaling relay points


Signaling End Points (SEP)
 These are the source and destination of signaling traffic. Can be identified as switching elements 
Signaling Transfer Points (STP)
Based on destination the signaling transfer point (STP) forward the received signaling message to another STP or to a signaling end point

Signaling Relay Points (SRP)

Received signaling message are relayed by the transport layer called Signaling Connection Control Part (SCCP) where the destination address is determined by “Global Title Translation”. Messages are not processed by the signaling relay point. It is basically an STP that use global title translation to route message.

All signaling points are identified by a Signaling Point Code (SPC) which is identified by a numbering scheme defined in the standards 

Signaling Modes

  • associated signaling mode
  • quasi-associated signaling mode
Associated Signaling Mode
Commonly used in association with the signaling circuit group. Signaling links are connected with those signaling points which is also the end-point. Nowadays this is no longer a common implementation as SIP is becoming popular and preferred way to implement voice traffic. 
Quasi-associated Signaling Mode
Signaling follow different routes. In the case of circuit group, although nodes A and B are connected adjacent to each other. The signaling is handled by one or more signaling transfer points.

Signaling Routes

The path through the signaling network from node A to B is called signaling route (or MTP route). Between nodes there can be two or more signaling routes can be used to reach a specific destination.

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