> For the complete documentation index, see [llms.txt](https://ss7.learn-telecom.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ss7.learn-telecom.com/link-types/a-link.md).

# A - Link

**Explanation of SS7 A - Link**

SS7 (Signaling System No. 7) is a set of telephony signaling protocols used to set up and tear down telephone calls, route SMS messages, and perform other telephony-related functions. 

The 'A-Link' in SS7 architecture specifically refers to the Access Link which connects a Signaling Point (SP) to a Signaling Transfer Point (STP).

An 'A-Link' is typically characterized by:

* High availability and reliability.
* Redundancy to prevent single points of failure.
* Use in both national and international signaling.

A typical SS7 network configuration ensures that the A-Link is robust to support critical communication signaling tasks.