ForeRunner
ATM Switch Network Configuration Manual
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Configuring PVCs
Co
nfigu
ri
ng PVCs
1.6 Traffic Types
NOTE
The following sections contain informal
definitions of the concepts presented. For a
detailed understanding of these issues, please
see the ATM Forum’s UNI 3.1 and TM 4.0
Specifications.
Quality of Service (QOS) Management is based on the bandwidth parameters associated with
a virtual connection and the class of service and ATM Adaptation Layer (AAL) used for that
connection. In order to support voice, video, and data, the ATM Forum has defined four
classes of service, or traffic types: Constant Bit Rate (CBR), Variable Bit Rate (VBR), Available
Bit Rate (ABR), and Unspecified Bit Rate (UBR).
•
At connection set-up time, traffic that uses a CBR parameter, such as a voice sig-
nal, makes a request for a dedicated Peak Cell Rate (PCR). Once the PCR is
defined, the ATM network must be able to guarantee that amount of bandwidth
for the duration of the connection.
•
At connection set-up time, traffic that uses a VBR parameter, such as a video and
data, makes a request for a dedicated PCR, Sustainable Cell Rate (SCR), and Max-
imum Burst Size (MBS). Once these cell rates are defined, the ATM network must
be able to guarantee these rates for the duration of the connection.
•
At connection set-up time, ABR traffic makes a request for a dedicated PCR and
Minimum Cell Rate (MCR). Once these cell rates are defined, the ATM network
must be able to guarantee the MCR rate for the duration of the connection. ABR
traffic sources adjust their transmission rate in response to information they
receive describing the status of the network and its capability to successfully
deliver data.
•
UBR traffic, such as broadcast information and ARP messages, is also known as
“best effort” service. UBR provides no bandwidth guarantees.
Because ATM is designed to provide a single network to transport this variety of traffic
classes, FORE’s traffic policing and Connection Admission Control (CAC) schemes are vital to
allowing this mix of traffic to flow smoothly.
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 ...