Overview of SS7
Every phone call that
is made utilizes the SS7 signaling network. This is the network that checks
to see if the destination phone is busy before the actual call is placed,
saving valuable bandwidth in an overcrowded PSTN. Essentially, the SS7
network is a packet data network that provides out-of-band signaling for
call control and advanced intelligent network services, such as 800 lookup,
Caller ID, local number portability, etc. GDC provides a NEBS Level
III compliant provisioning solution for the transport of signaling channels
that eliminates the need for channel banks.
The SS7 network is comprised of Signaling Points and
Signaling Links. The Signaling Links exchange messages between network
elements, usually over 56 or 64 kbps bidirectional channels. This signaling
occurs out-of-band on dedicated channels. Out-of-band signaling enables
faster call setup times, more efficient use of voice circuits, as well
as allowing for advanced features such as Caller ID. Ultimate Redundancy Because the SS7 network is critical to call processing, redundancy is critical. For example, both SCPs and STPs are usually deployed in pairs — in different buildings — to ensure that the network will continue to function if one fails. All of the links are also deployed in pairs. If one link fails, signaling traffic is rerouted over the redundant link. Again, the redundant equipment is located in a different physical location. Often, these links are established through separate physical connections dedicated solely to transporting the signaling traffic. Therefore, the signaling traffic system and management paths remain in place even when the primary voice trunks are out of order.
Figure 1 — Basic SS7 Network Architecture
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