Signaling Link Selection

The signaling link selection (or SLS) is a field in the Message Transfer Part (MTP) level 3 frame of Signalling System No. 7 (SS7), a set of telephony signaling protocols which are used to set up most of the world's public switched telephone network telephone calls.

The SLS is used as a label to route MTP level 3 messages in the SS7 network. Level 3 is the Signalling Network Functional Level (Network Level).

SLS can also be used in reference to the algorithm that an SS7 node uses for selection of the appropriate signaling link to use for communicating with an adjacent SS7 node. Factors such as load balancing and link availability are used to determine the appropriate link.