Description: C-paths consist of a layer 2 data link carrying an associated layer 3 signaling protocol. Layer 3 signaling is defined by the Control, Link Control, PSTN, BCC, and Protection protocols. Therefore, a C-path can exist for the Control protocol, the Link Control protocol, the PSTN protocol, the BCC protocol, and the Protection protocol. In addition, ISDN D-channel data is also carried over C-paths. Separate C-paths exist for ISDN Ds, p, and f-type data. There can only be one of each control, link control, and BCC C-Paths whereas multiple PSTN and ISDN C-Paths may exist.

A group of C-Paths are associated with a C-channel. The C-path for protection, however, is not carried in a C-channel.