Apparatus for determining a protocol of messages traversing a signalling link in a telecommunications network includes a memory for storing one or more predetermined characteristic of a message in the protocol that can be used to distinguish that protocol from other protocols. A protocol auto-discovery module is coupled to the memory and to a module that extracts channels from signalling link timeslots. The protocol auto-discovery module determines whether the predetermined characteristic is present in the sampled message and identifies the signalling link as carrying messages in the particular protocol if the predetermined characteristic is present in the sampled message. The identification may be based on a confidence measure stored in a channel configuration table which is incremented when a message on the signalling link is identified as being in that particular protocol and decremented when a message is identified as being in another protocol.