ForeRunner
ATM Switch Network Configuration Manual
1 - 1
Co
nfigu
ri
ng PVCs
CHAPTER 1
Configuring PVCs
To establish a permanent communication link between two sites, it is necessary to establish
permanent virtual circuits (PVCs) at each switch along the communications path. This chapter
discusses the creation of PVCs through the ATM Management Interface (AMI), a command-
line user interface to ForeRunner ATM switches.
1.1 General Concepts
Each ATM cell contains a virtual path identifier (VPI) and a virtual channel identifier (VCI) as
part of its five-byte ATM header. The VPI and VCI are used to route the cell through the ATM
network. When a switch fabric receives a cell, it examines the ATM header to determine the
correct output port, VPI, and VCI for the cell. For example, an ATM switch fabric can be con-
figured such that any cell received on port A1 with VPI|VCI = 0|32 is switched to port B2
with VPI|VCI = 0|35. The translation from input port, VPI, and VCI to output port, VPI, and
VCI is achieved via a mapping table in the switch fabric’s memory.
The VCI value of cells does not change as the cell is switched through the ATM network via a
virtual path. In a single switch environment, a cell’s VPI and VCI are translated only once, but
in a multiple switch environment a cell’s VPI and VCI are translated many times. It is impor-
tant to remember that a cell’s VPI and VCI are of local significance only (i.e., link-by-link). It is
also important to note that virtual connections are unidirectional; that is, they are valid in one
direction only. The VPI and VCI may change as the cell is switched through the network.
Summary of Contents for forerunner series
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Page 16: ...TOC 10 ForeRunner ATM Switch Network Configuration Manual Table of Contents ...
Page 20: ...LOF 4 ForeRunner ATM Switch Network Configuration Manual List of Figures ...
Page 22: ...LOT 2 ForeRunner ATM Switch Network Configuration Manual List of Tables ...
Page 30: ...viii ForeRunner ATM Switch Network Configuration Manual Preface ...
Page 144: ...3 58 ForeRunner ATM Switch Network Configuration Manual Configuring an Emulated LAN ...
Page 180: ...6 12 ForeRunner ATM Switch Network Configuration Manual ATM Forum PNNI ...
Page 220: ...9 6 ForeRunner ATM Switch Network Configuration Manual Configuring Timing ...
Page 300: ...D 24 ForeRunner ATM Switch Network Configuration Manual Configuring FramePlus Modules ...
Page 308: ...Acronyms 8 ForeRunner ATM Switch Network Configuration Manual Acronyms ...
Page 346: ...Glossary 38 ForeRunner ATM Switch Network Configuration Manual Glossary ...
Page 352: ...Index 6 ForeRunner ATM Switch Network Configuration Manual Index ...