Virtual Path Identifier abbreviated as VPI is a data communication identifier that uniquely identifies a network path for an asynchronous transfer mode (ATM) cell packet to reach its destination node. It is a method of sending data in small data packs.
VPIs are 8 to 16-bit numeric headers inside each ATM cell packets.
Here transmission path is the optical fibre used for transmitting high-speed data. The idea behind dividing the virtual connection identifier into two parts i.e. virtual path identifier(VPI) and virtual circuit identifier(VCI) is to allow hierarchical routing. Most of the switches in a typical ATM network are routed using VPIs.
The connection between two endpoints of a fibre or transmission path is accomplished through a virtual path and virtual circuit. The physical fibre may consist of many virtual paths. A virtual path provides a connection between two switches. Cell networks are based on virtual circuits. Cells belonging to a single message follow the same virtual circuits. There are several virtual paths that utilize media bandwidth. If media bandwidth is B and there are N VPs then each VP has a bandwidth B/N. Each virtual path is divided into several virtual channels. VPI determines the VP for each particular user and their usage.
In the ATM header, the bandwidth of the communication route is reasonably classified into separate virtual path using their VPIs. Each VP is allowed a fixed bandwidth.
With the usage of optical fibres and virtual path identifiers, the quality of services in data connection and bandwidth has improved significantly.
These are specified by parameters and usage which makes the process standardized.
To allow uninterrupted connections switching and semi-permanent virtual connections are present.
It is used to connect end-users.
It manages data and signals between end to end-user.
It also finds usage between end-user and the network entity.
It reduces the complexity of network design providing a simpler network.
The consistency and network performance is improved.
It diminishes setup timings and processing of small connections.
1. What is the difference between VC and VP i.e. virtual channel and virtual path?
A virtual connection is a logical connection to the virtual circuit. In ATMs, virtual channels having the same endpoints are grouped together into virtual paths.
2. How do VCI and VPI work in ATM network?
VPI or VCI are connection identifiers and ATMs identifies these only. A virtual
channel connection (or virtual circuit) is the essential unit, which conveys a single stream of cells, all together, from client to client. A bundle of virtual circuits can be packaged together into a virtual path connection. A virtual path connection can be made from start to finish over an ATM network.
3. Why ATM is asynchronous?
Asynchronous transfer mode (ATM) is a switching strategy utilized by telecommunication networks that uses nonconcurrent time-division multiplexing to encode information into little, fixed-sized cells. This is not quite the same as Ethernet or web, which utilize variable packet sizes for data. ATM is the centre convention utilized over the synchronous optical system (SONET) spine of the integrated digital services network (ISDN).