V5 interface
Encyclopedia
V5 is a family of telephone network protocol
s defined by ETSI which allow communications between the telephone exchange
, also known in the specifications as the local exchange (LE), and the local loop
. With potentially thousands of subscribers connected to the LE there is the problem of physically managing thousands of wires out to the local subscribers (and the costs associated with that). Prior to the specification of V5 the manufacturers of exchange equipment had proprietary solutions to the problem. These solutions did not inter-operate and meant being tied into a single manufacturer's method at each exchange.
V5 provided a standard set of protocols from the subscriber to the LE. The AN (or Access Network
) was defined as a reference point. Signalling between this point and the LE was standardised and therefore allowed a multiple vendor solution, provided the specifications were followed. This resulted in a single link (or in the case of V5.2 multiple links) from the AN to the LE, reducing the need for many lines along this point (or more likely no need for a proprietary solution to manage the single link). The final link to the local loop remained the same with digital signalling (ISDN) and analogue signalling for basic telephony (also known as POTS
in the industry).
The protocols are based on the principle of common channel signalling where message-based signalling for all subscribers uses the same signalling channel(s) rather than separate channels existing for different subscribers.
V5 comes in two forms:
V5.1 only supports the Control, 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.
Communications protocol
A communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications...
s defined by ETSI which allow communications between the telephone exchange
Telephone exchange
In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls...
, also known in the specifications as the local exchange (LE), and the local loop
Local loop
In telephony, the local loop is the physical link or circuit that connects from the demarcation point of the customer premises to the edge of the carrier or telecommunications service provider's network...
. With potentially thousands of subscribers connected to the LE there is the problem of physically managing thousands of wires out to the local subscribers (and the costs associated with that). Prior to the specification of V5 the manufacturers of exchange equipment had proprietary solutions to the problem. These solutions did not inter-operate and meant being tied into a single manufacturer's method at each exchange.
V5 provided a standard set of protocols from the subscriber to the LE. The AN (or Access Network
Access network
An access network is that part of a telecommunications network which connects subscribers to their immediate service provider. It is contrasted with the core network, which connects local providers to each other...
) was defined as a reference point. Signalling between this point and the LE was standardised and therefore allowed a multiple vendor solution, provided the specifications were followed. This resulted in a single link (or in the case of V5.2 multiple links) from the AN to the LE, reducing the need for many lines along this point (or more likely no need for a proprietary solution to manage the single link). The final link to the local loop remained the same with digital signalling (ISDN) and analogue signalling for basic telephony (also known as POTS
Plain old telephone service
Plain old telephone service is the voice-grade telephone service that remains the basic form of residential and small business service connection to the telephone network in many parts of the world....
in the industry).
The protocols are based on the principle of common channel signalling where message-based signalling for all subscribers uses the same signalling channel(s) rather than separate channels existing for different subscribers.
V5 comes in two forms:
- V5.1 (ETS 300 324-1) in which there is a 1 to 1 correspondence between subscriber lines and bearer channelBearer channelA bearer channel is a DS-0 that carries call content i.e. one that does not carry signaling.In the Common Channel Signaling scheme for telecommunications, signaling is sent out-of-band, while all other traffic rides bearer channels...
s in the aggregate link to the exchange. A V5.1 interface relates to a single aggregate E1T-carrierIn telecommunications, T-carrier, sometimes abbreviated as T-CXR, is the generic designator for any of several digitally multiplexed telecommunications carrier systems originally developed by Bell Labs and used in North America, Japan, and South Korea....
(2 Mbit/s) link between a multiplexer and an exchange. - V5.2 (ETS 300 347-1) which provides for concentrationRemote concentratorIn modern telephony a remote concentrator, Remote Concentrator Unit , or Remote Line Concentrator is the lowest level in the telephone switch hierarchy.Subscribers' analogue telephone/PSTN lines are terminated on concentrators...
where there are not enough bearer channelBearer channelA bearer channel is a DS-0 that carries call content i.e. one that does not carry signaling.In the Common Channel Signaling scheme for telecommunications, signaling is sent out-of-band, while all other traffic rides bearer channels...
s in the aggregate link(s) to accommodate all subscribers at the same time. A single V5.2 interface can control up to 16 E1T-carrierIn telecommunications, T-carrier, sometimes abbreviated as T-CXR, is the generic designator for any of several digitally multiplexed telecommunications carrier systems originally developed by Bell Labs and used in North America, Japan, and South Korea....
links at once and can include protection of the signalling channels.
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. (ie 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 (ie 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, PSTN
Public switched telephone network
The public switched telephone network is the network of the world's public circuit-switched telephone networks. It consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all inter-connected by...
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
Link Access Procedures, D channel
Link Access Procedures on the D channel , specified in ITU-T Q.920 and ITU-T Q.921, is the second layer protocol on the ISDN protocol stack in the D channel.It is heavily based on HDLC.-External links:*http://www.protocols.com/pbook/pdf/isdn.pdf...
ISDN transport layer.
V5 is a protocol stack which controls circuit-switched communication paths.
Subsequent developments
Portions of V5 were re-used for a new service known as Narrowband Multimedia Delivery Service (or NMDS). In particular the PSTN protocol was re-used and combined with ISDN to provide a service to the subscriber. This allowed a digital connection to the subscribers house and the re-use of analogue phones across the digital connection. The AN reference point was replaced by an ISDN-like NTE. This NTE managed an analogue service and a basic rate ISDN service to the subscribers home.See also
- SS7SS7SS-7 can stand for:* Signaling System #7, a set of telephone signaling protocols.* The R-16 missile, with NATO reporting name SS-7 Saddler.* China Railways SS7, an electric locomotive model in China.* Super Socket 7, a chip socket introduced by AMD...
Signaling System Seven - for communications between exchanges. - OSI modelOSI modelThe Open Systems Interconnection model is a product of the Open Systems Interconnection effort at the International Organization for Standardization. It is a prescription of characterizing and standardizing the functions of a communications system in terms of abstraction layers. Similar...
- Telcordia (formerly Bellcore) GR-303-CORE, Integrated Digital Loop Carrier System Generic Requirements, Objectives, and Interface, which is the standard that describes the ANSI equivalent of V5.2
- BT HighwayBT HighwayBT Highway was a UK retail ISDN2e service from British Telecom which was announced in November 1997 and withdrawn in February 2007. In the domestic market, it was sold as BT Home Highway and for small businesses, BT Business Highway...
British Telecom's NMDS implementation.