Panasonic 1200N User Manual

The number of lines accommodated can be increased by connecting a number of
ATM Switch units. Line interface can be used to connect the ATM Switch units. An
interface dedicated to connections between units is not necessary. When a number
of the ATM Switch units are connected to increase the number of lines, the actual
number of lines accommodated is the total number of lines less the number of lines
between the units.

ATM, or Asynchronous Transfer Mode, is a communication method that will serve
as the basis for tomorrow's communication network, B-ISDN. 

In ATM, all data in the network are exchanged in fixed-length, 53-byte blocks
called "cells." This allows much faster and broader communications compared to
the conventional STM or packet switching method. 

The communication channels for cells are such virtual connections as VP (Virtual
Path) and VC (Virtual Channel). These are identified by the VPI (Virtual Path
Identifier) and VCI (Virtual Channel Identifier) stored in the 5-byte header of each
cell.

 is a conceptual diagram of VP and VC in an ATM network, and the

format of ATM cells.