Editing V5 interface (section)

==The layer 3 protocols==
* '''Control protocol''' - This controls the setup and basic management of the V5 link from the Access Network (AN) to the Local Exchange (LE).
* '''PSTN protocol''' - Translation of the analogue signals for POTS into a digital form for transfer from AN to LE. (i.e. off-hook, digit dialling, on hook etc.).
* '''BCC protocol''' - In V5.2 since any channel could be allocated to the call, this protocol is assigned the job of managing the assignment of channels to a call. (Only in v5.2)
* '''Link control protocol''' - For managing up to 16 E1 links. It controls the status of the links (i.e. in service/out of service).
* '''Protection protocol''' - Used in V5.2; this protocol is duplicated on two or more channels on two or more links and provides instant failover in the event of one failing.

V5.1 only supports the Control, [[Public switched telephone network|PSTN]] and ISDN protocols. V5.2 also supports BCC, Link  Control and Protection protocols.

V5 layer 3 protocols are transported on a layer 2 protocol called LAPV5, a variation of the LAP-D or Link Access Procedures, D channel ISDN transport layer. 

V5 is a protocol stack which controls circuit-switched communication paths.