SS7 - notes

Few salient points
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Terms and more
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BEC (Basic Error Correction)


Telcordia administers ANSI Point Codes.
User Part Unavailable (UPU)
Mixed Linkset
Combined Linkset
Alias Point Code/Capability Point Code

quasi-associated route

Class3 Switch/Class 4 Switch



Switches are also known as exchanges; within the United States, the term exchange is used interchangeably with Central Office (CO) or End Office (EO).

Network signaling is also known as inter-switch signaling, network-network signaling, or trunk signaling.

PSTN (public switched telephone network) = Plain Old Telephone Service (POTS).

How voice circuit is reserved?
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What is the voice path?
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SS7 Signaling can do lot more ---
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• translate toll-free numbers into "routable" numbers
• validate credit and calling cards
• provide billing information
• remove faulty trunks from service
• provide the support for supplementary services (such as caller ID),
• roaming with your cellular telephone
• local number portability (LNP)

Non-circuit related signaling
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modern telephone networks can perform signaling while a call is in progress, especially for supplementary services—for example, to introduce another called party into the call, or to signal the arrival of another incoming call (call waiting) to one of the parties. In fact, since the 1980s, signaling can take place even when there is not a call in place. This is known as non-circuit related signaling and is simply used to transfer data between networks nodes. It is primarily used for query and response with telecommunications databases to support cellular networks, intelligent networks, and supplementary services. For example, in Public Land Mobile Networks (PLMNs), the visitor location register (VLR) that is in charge of the area into which the subscriber has roamed updates the home location register (HLR) of the subscriber's location. PLMNs make much use of non-circuit-related signaling, particularly to keep track of roaming subscribers.


TUP versus ISUP
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ISUP resides at Level 4 of the SS7 stack with its predecessor, the Telephone User Part (TUP). TUP is still used in many countries, but ISUP is supplanting it over time. TUP also provides a call setup and release that is similar to ISUP, but it has only a subset of the capabilities. TUP is not used in North America because its capabilities are not sufficient to support the more complex network requirements.