System Description; Atm Overview; Virtual Circuits - 3Com 3C63100-AC-C - PathBuilder S600 Bridge/router Reference Manual

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ATM Overview

Virtual Circuits

S D
YSTEM
This chapter provides a brief overview of ATM (Asynchronous Transfer Mode)
technology, describes the PathBuilder
S600), and lists PathBuilder S600 system specifications. It includes the following
sections:
ATM Overview
n
PathBuilder S600 with STX Overview
n
Specifications
n
Options and Parts List
n
ATM provides the means of simultaneously transferring a wide variety of services
with different protocols and bandwidth requirements such as voice, packet data,
and video between end users or user networks. It does so by segmenting the input
data streams into 53 byte cells, assigning the cells to virtual circuits set up in the
ATM network, multiplexing the cells for transmission according to the bandwidth
requirements of the individual data streams, and reassembling the cells into the
original data streams at the receiving end.
For more detail about how to apply the PathBuilder S600 to provide ATM WAN
access, see "Application Overview" in Chapter 4.
ATM networks are organized into virtual circuits or logical duplex paths between
two ATM unit ports, as shown in Figure 1.
Figure 1 Virtual Circuit Scheme
{
Virtual
VCI 1 (Transmit)
Circuit
VCI 1 (Receive)
VCIs
VCIs
{
Virtual
VCI 1 (Transmit)
Circuit
VCI 1 (Receive)
ESCRIPTION
®
S600 WAN Access Switch (PathBuilder
VPI 1
VPI 2
{
VPI 3
{
VPI 1
Transmission
Path
Transmission
Path