Stands for “Virtual Path Identifier.”

A VPI is an 8- to 12-bit header in an Asynchronous Transfer Mode (ATM) cell that identifies the trail the cell ought to take to its vacation spot. An ATM cell’s VPI works along with its Virtual Channel Identifier (VCI) to information a cell because it passes by way of a number of ATM switches. The dimension of a VPI depends upon the scale and scale of the ATM network; small networks use an 8-bit VPI that helps tons of of paths, whereas giant networks use a 12-bit VPI that helps a number of thousand distinctive paths.

ATM is a networking expertise that creates digital paths for knowledge cells to journey throughout to their vacation spot. Unlike IP routing, the place a packet in an information stream can take one among many attainable routes, ATM cells in an information stream all take the identical route. The VPI info in every cell’s header identifies the precise digital path the cell ought to take.

While ATM was designed to be more environment friendly at routing network site visitors, in follow ATM networks have been fairly complicated. The small dimension of every knowledge cell, mixed with the info taken up by VPI and VCI headers, resulted in important overhead. Ethernet and IP-based networking applied sciences have been less complicated and scaled higher to excessive site visitors, finally taking up the position that ATM networking had crammed.

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