Virtual path identifier definition
Virtual path identifier (VPI) refers to a key component of the asynchronous transfer mode (ATM) protocol, used primarily for telecommunication networks. In an ATM network, data is segmented and sent in fixed-size packets or “cells”. Identifiers such as the virtual path identifier or the virtual channel identifier help route the cell to its intended destination. Virtual path identifiers are considered outdated and have been largely replaced by modern protocols and mechanisms.
See also: asynchronous transfer mode, multiprotocol label switching
Virtual path identifier drawbacks:
- Complexity. ATM networks, including the use of VPI and VCI, can be complex to set up and manage compared to modern networking technologies.
- Overhead. As ATM cells have headers that contain VPI and VCI information, it adds overhead, reducing the effective bandwidth available for data.
- Fixed cell size. Fixed-size cells can lead to inefficiencies, especially when transmitting small amounts of data.
Virtual path identifier alternatives:
- MPLS (multiprotocol label switching). MPLS operates by prefixing packets with an MPLS label. This label determines the packet's path through the network, similar to how VPI would in an ATM network.
- Ethernet. VLAN (virtual local area network) tags can segment traffic in a manner somewhat similar to VPI. The VLAN tag identifies which VLAN the frame belongs to and thus, how it should be processed within the network.
- IP networks. The source and destination IP addresses in packet headers determine the path for the packets, while the dynamic routing protocols find the best path.
