Determining the Packet Length | NETGEAR XM128 ISDN specs

Reference Guide for the Model XM128 ISDN Digital Modem

Determining the Packet Length

The user’s information is sent on a frame-by-frame basis for V.120 and X.75, sometimes called packetized. The maximum frame length on the sending side should not exceed the maximum frame length that the receiving side allows. Sometimes this information is exchanged during handshaking. However, few manufacturers, if any, have implemented this mechanism.

If the sending side sends packets greater than what the receiving side allows, the receiving side discards the frame and replies with a Frame Reject Frame (FRMR). The FRMR indicates that the information received is too long. Both sides then reset their link layer negotiation and send the frame again. Usually this process repeats until the call gets disconnected.

The Model XM128 modem has a fixed maximum receiving frame size of 2048 octets, which is larger than most devices can support. The default maximum sending frame size is 252 octets for V.120 and 2048 for X.75. If you need to change the maximum sending frame size, the ATCL command is used.

To change the maximum sending frame size, use the following commands and follow these steps:

1.Enter ATCL252 (set the frame size to 252 octets, user value between 1 and 2048).

You should receive this message:

OK

2.Enter ATCL? (to inquire about the current setting of the packet length).

You should receive this message:

Maximum user data length in a packet (byte) : 252

ISDN Overview

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NETGEAR XM128 ISDN manual Determining the Packet Length

Contents

USA NETGEAR, Inc EN 55 022 Declaration of Conformance TrademarksStatement of Conditions Certificate of the Manufacturer/Importer Bestätigung des Herstellers/ImporteursVCCI-2 Statement Customer Support World Wide Web Bulletin Board Service Contents Reference Guide for the Model XM128 Isdn Digital Modem Error Correction and Data Compression with Chapter Advanced Isdn Appendix a Technical Specifications Appendix E Connector Pin Assignments Figures Xii Tables Xiii Tables 10-1 Table F-1 Xvi Tables Purpose Preface Use of Enter, Type, and Press ConventionsSpecial Message Formats Other Conventions Manual contentsRelated Publication DSU Manuals Chapter Introduction Features Reference Guide for the Model XM128 Isdn Digital Modem Interface options Front PanelInterface Options PWR LED descriptionsLabel Color Activity Description DSR DTRRTS CTS Rear panel of the Model XM128 modem with S interface Rear Panel Rear panel components PowerLabel Description ON/OFFPage Package Contents Chapter Installation Model XM128 modem connections Installing the Modem Verifying Hardware Installation Page Selecting the Appropriate Windows 95 Driver INF file Setup for Windows 95 and Windows NT Click on Close Configuring Your Modem Using a Terminal Program Chapter ConfigurationConfiguring Your Isdn Line and Network Terminal programs Understanding AT CommandsOperating system Program Unix Type of AT command Example Quick Tips for Issuing AT CommandsSupported AT command types Using AT Commands to Verify Modem Response Communication Speed SetupResult codes commands Command Description Switches supported by the Model XM128 modem Switch Type Setup for North America Type ATSPIDO=n and Enter Spid Setup for North America Entering DNs Setup for Europe and the United Kingdom AT commands for setting MSN AT commands for setting protocolsProtocol AT command Multiple subscriber number AT command Making Async to Sync PPP and Slip calls Internet and Remote Access PPP and SlipChapter Async to Sync PPP Keeping a Line Connection During Idle Time Model XM128 modem modem responds Multilink PPP Making a call using Multilink PPPAnswering Async to Sync PPP calls Endpoint Discriminator Dialing Pre-stored Phone NumbersS85 register values Value Description Call Bumping Dynamic Channel Allocation Page Chapter Isdn Overview Commands for Outgoing CallsDialing Out Using Isdn Mode Dialing Out for Analog Adapter Port Dialing Out Using Isdn Mode Optional Speech Bearer ServiceManually Switching Communication Modes Call placing commands Dialing commandsAT Command Dial string it maps to Placing the Call Digital Data Commands for Incoming Calls Determining the Packet Length Commands for assigning Isdn numbers Answering a Call Using MSN Best-effort Call Answering Data over Speech Channel Best-effort call answering bit commands Ambiguity Resolution Switch for Voice CallsCommand Function Multi Auto-Answering of Data Calls Parameter 110 120 Isdn protocol specificationsUnderstanding Isdn Communication Protocols AT Command Description Configuration commandsIsdn Communications Answering a V.110 Call Selecting V.120 for German National Isdn 1TR6 Selecting V.120 for European Isdn DSS1 Switch Making a V.120 Call Answering a V.120 Call Dialing in V.120 Mode Identifying Your Line Provisioning Kbps Speeds Making an X.75 Call Isdn Communications EuropeAnswering an X.75 Call Making a Bundled Call with Dialing Prestored Phone Numbers Bundle Connection with V.42bis Data Compression Page Call Control for DSS1 Chapter Advanced Isdn S108+n= Function Control of Outgoing Service IndicatorRegister values and functions S108.n= Function Outgoing low-layer compatibility commandsControl of Isdn Phone Numbers and Subaddresses Reference Guide for the Model XM128 Isdn Digital Modem Call Control for 1TR6 Old German Isdn Control of EAZ Endgeräteauswahlziffer Command Function Answering a Call for DSS1 Answering a Call Best-effort Call Answering Answering a Call for 1TR6 Multi-Auto-Answering of Data Calls Ambiguity Resolution Switch for Voice Calls Data Call Indication Disable Inbound Call Connection Placing a Call for DSS1 Point-to-Point ConfigurationPlacing a Call Placing a Call for 1TR6 User-To-User Information Page Chapter Analog Call Handling Frequently used AT commands AT Commands for Analog CallsFrequently used AT commands European switches AT Command Description of command Placing a Call from the Analog Adapter Making and Receiving Analog Calls Accepting an Incoming Call Upgrading with Flash Eprom Chapter Modem UpgradeDefinitions for the d modifier Modifier Definition Kernel Mode Upgrade Instructions Power-on Self-test Chapter TroubleshootingTest Sequence Test Description Loopback with Self-test AT&T10 Loopback TestsIsdn Loopback test AT&T9 B1/B2 Loopback with Self-test Diagnostic Command Using The Embedded Protocol Analyzer Modem Reset Capturing the Protocol Data Setting up the Embedded EPA Commands for analyzing captured data EPA CommandsAnalyzing the Captured Data Atct Key Function Description Control key functionsPage General Specifications Appendix a Technical SpecificationsNetwork Protocols and Standards Compatibility Security Physical Specifications Power AdapterEnvironmental Specifications Data Compression Security Types and Levels Appendix B Security Functions Level 2 Security Level 1 SecurityTable B-1 Types of security Type 1 Security Type 2 Security Level 3 Security Setting and Modifying PasswordsTable B-2 Levels of security Level Table B-3 Auto callback commands Nonpassword Auto Callback FunctionAT*GC0 AT*GC1 Simplex Mode Appendix C AT Command Set ReferenceOperation Mode of the DTE Interface Command Options Function and description AT Command DescriptionsTable C-1 Basic AT command set CE1 CE0CH? CL? Dtmf CP0CP1 USA Model XM128 modem returns result code SPID0 Description of ATI3 OutputSPID1 SPID? Output parameter Output value description Table C-2 ATI3 command outputTable C-3 Extended AT& command set Result Codes Knn =phone number Table C-4 Extended AT* command set Table C-4 lists the extended AT* command set Appendix D Status Registers and Result Codes Viewing and Setting S-Registers Examples for Setting S-Registers Setting S-Registers Table D-1 Binary conversion table Table D-2 Setting bitBit Binary Decimal Hexadecimal Value Operation Example Decimal Hexadecimal Binary Table D-3 Basic S-registers ATSn=x Command Function and description DefaultRegister Descriptions Table D-4 Extended S-registers ATSn=x See also S-register ATX2 ATX3 ATX4 ATX1 S24= Bitmapped register S35= Bitmapped register When Data/Voice is pressed Do not send low-layer compatibility Enables loopback 4 test DCA function is enabled Reference Guide for the Model XM128 Isdn Digital Modem Reference Guide for the Model XM128 Isdn Digital Modem Reference Guide for the Model XM128 Isdn Digital Modem Message handling systems MHS Reference Guide for the Model XM128 Isdn Digital Modem Speed is greater than 19200 bps ATXn Result Code Option Table Table D-5 ATXn command setting options Connect Supported Result Code Chart Symbol ReferenceTable D-6. Result code chart Field name Possible values Result Code Field DescriptionsTable D-7 Result code field descriptions Table D-8 Connect strings Connect Strings for Error Corrected ConnectionsPage RJ-45 Plug and Connector Appendix E Connector Pin Assignments RCV + XMT + Pin Assignment Table E-3. RJ-11 connector pin assignments RJ-11 Plug and ConnectorPage Appendix F Serial Port Interface Signal/pin description Signal direction Signal nameRS-232 Serial Interface Table F-1 Serial port interface Table F-2 Asynchronous flow control cable connection Asynchronous Cable ConnectionsTXD RXD RTS CTS DSR CD DCD DTR Isdn Overview Appendix G Isdn Reference Basic Rate Interface Out-of-Band Signaling Isdn Basic Rate Interface Points Terminal Adapter or Digital Modem Spid Setup Ordering Isdn Service Reference Guide for the Model XM128 Isdn Digital Modem Table G-1 Isdn line configuration Order Form for AT&T 5ESS Switch NI-1 Isdn Table G-2 Isdn line configuration Order Form for DMS-100 Switch NI-1 or Custom Isdn Order Form for Ewsd NI-1 Isdn Table G-3 Isdn line configuration Numerics Index Isdn Reference Guide for the Model XM128 Isdn Digital Modem Reference Guide for the Model XM128 Isdn Digital Modem