The paper provides an introduction to the V5 interface. The V5 interface is a kind of open, standard Service Node Interface (SNI) between an Access Network (AN) and a Service Node (SN). It provides interoperability and compatibility for equipment supplied by different vendors, both at switch side and at access network side.

This paper introduces V5-related basic concepts, an access model, a protocol architecture, the LapV5, an AN frame relay, and various L3 protocol layers. Several applications, including an optical access network and a wireless access network, are also discussed. Suggestions are given for the enhancement of the second edition of V5.