Cabletron Systems manual BRIM-A6 User’s Guide B-3

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The ATM Cell

Header

Data

Generic Flow Control (GFC)

 

Virtual Path Identifier (VPI)

 

 

 

 

 

 

VPI

 

 

VCI/VPI

 

 

 

 

Virtual Channel Identifier (VCI)

 

 

 

 

 

 

VCI

 

Payload Type

 

Reserved

 

 

 

 

 

 

Header Check Sequence

 

 

 

 

 

 

 

 

Figure B-2 ATM Header Field Breakdown

The Header field is made up of several sub-fields which provide management/control information relating to a cell. Brief descriptions of each header field are as follows:

•Generic Flow Control (GFC) – provides the ability to control the traffic flow for different grades of service.

•Virtual Path Identifier (VPI) – identifies the virtual path to which the cell belongs.

•Virtual Channel Identifier (VCI) – identifies the virtual channel to which the cell belongs.

•Payload Type Indicator (PTI) – describes whether the information is user information, network information, or management information.

•Header Check Sequence (HCS) – detects bit errors; corrects single bit errors.

This method of fixed-cell length has many advantages over conventional packet transfer technologies; one major advantage is time. Since ATM cells are fixed in length, and all of the header data is the same, processing them is dramatically simplified. This eliminates the need for buffers and processors that tend to slow down transmission. By contrast, other LAN packets vary in length, making it necessary to check each incoming packet to ensure that it is complete and contains no errors.

BRIM-A6 User’s Guide

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Contents BRIM-A6 USER’S Guide BRIM-A6 User’s Guide Vcci Notice FCC NoticeDOC Notice Cabletron Software Program License Exclusion of Warranty and Disclaimer of LiabilityCabletron SYSTEMS, INC. Program License Agreement United States Government Restricted Rights Declaration of Conformity Contents Viii BRIM-A6 User’s Guide Chapter Introduction Using this ManualFollowing conventions are used throughout this document Document ConventionsBRIM-A6 Overview BRIM-A6 FeaturesRelated Manuals BRIM-A6 SpecificationsEMI EMCGetting Help Unpacking the Brim Chapter InstallationInstalling an Apim Installing ApimsInstalling a Brim in a MIM Installing BrimsRemoving the Brim Coverplate Installing a Brim in a Hub BRIM-A6 User’s Guide Chapter Local Management Keyboard Conventions Function Local Management Keyboard ConventionsATM Connection Tables Screen Using LIM to Create PVCsATM Connection Tables Screen Fields Using ATM Connection Tables Screen Commands ATM Connection Tables Screen CommandsDeleting PVCs from the Connection Tables Screen Adding PVCs to the Connection Tables ScreenBRIM-A6 Setup Screen Using LM to Create PvcsVCI BRIM-A6 Setup Screen FieldsVPI BRIM-A6 Setup Screen Commands Accessing the BRIM-A6 Add/Delete Entry Screen Using BRIM-A6 Setup Screen CommandsBRIM-A6 Add/Delete Entry Screen Fields Adding a PVC BRIM-A6 Add/Delete Entry Screen CommandsModifying a PVC Deleting a PVC BRIM-A6 LEDs ChapterDescribes each of the Apim LEDs Apim LEDsAPIM-21 Specifications Appendix a Apim SpecificationsAPIM-11 Specifications APIM-29 Specifications APIM-22 SpecificationsBNC APIM-67 SpecificationsATM Basics Appendix B ATM OverviewFigure B-1 ATM Cells ATM CellBRIM-A6 User’s Guide B-3 Virtual Channels and Virtual Paths ATM NetworkATM Protocol Permanent and Switched Virtual ChannelsB-6 BRIM-A6 User’s Guide BRIM-A6 User’s Guide B-7 B-8 BRIM-A6 User’s Guide
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