> Technical Notes > Modem Troubleshooting

8.3.3

GSS Technical Note: Modem Troubleshooting Guide for cc:Mail

by Ron Herardian
©1998 Global System Services Corporation (GSS)

OVERVIEW

Modem connection reliability issues are very common with cc:Mail Router and Mobile.  Most of the available information focuses on the cc:Mail Router command lines but a variety of other factors can interfere with Router-to-Router communications.  At the same time, there are several command line parameters related to modem communications but no available summary of when they should be used.  This GSS technical notes addresses the gap in available information.

For Router-to-Router modem communication errors follow these steps:

I. HARDWARE CONFIGURATION:

The first thing to do is rule out obvious possibilities and hardware problems.

1. Ideally, you will have the same make and model of modem on both sides and the same ROM revision.
2. Many manufacturers issue updates to their ROMs to correct problems with their modems.
3. Make sure you have 16550 UARTs in the PC (older PCs have 8250 chips which do not work reliably for speeds over 9600 Baud.  Make sure the Router machines are not overworked.  If the Router machine is overworked connections can be lost applies only to Windows systems).

II. CC:MAIL TROUBLESHOOTING:

1. TROUBLE-SHOOT: Use the diagnostics parameter on both router command lines and pinpoint where it fails, i.e., is it during modem handshaking, ADE and Bulletin Board messages, or regular messages?  Does the connection fail early on, during small messages, or only when transferring large attachments?  Try to understand the exact steps leading up to the problem and identify exactly what the applications and the modems are doing when a problem occurs.

2. POST OFFICE AND NETWORK PROBLEMS: When using Remote Call Through—where users call into a Router running at a hub post office which then connects to a subordinate post office—check the integrity, fragmentation (free message bytes), and reclaim status of the hub and the user’s home post office.  Post office problems can cause very unreliable Routers.  Try ANALYZE and RECLAIM for DB8 post offices.  For high-traffic POs consider using the MSGWAIT parameter, e.g., MSGWAIT/15.  Also check NFT Error logs and see if Routers are appearing regularly as this could point to a capacity problem on the network or at the server (look for warnings writing which are read retries).

III. CC:MAIL ROUTER SOFTWARE CONFIGURATION:

1. Check the modem strings on both sides.
   For data connection lost errors, use of the LSEC parameter on both sides is recommended for long-distance calls and mandatory for international calls. Consider using the TIMEOUT parameter, e.g., TIMEOUT/60.
2. Check Router versions, version 6.1x is recommended.  Preferably run the same version on both ends of the connection.
3. Only as a last resort, consider reducing the speed of the connection where line conditions are poor or if calls are international.
4. If none of these things work get out the modem books and review the command line from cc:Mail (sometimes they are wrong).  Here are the guidelines for correct modem configuration:

            Respond to DTR normal, do not force true
            Set to AT mode
            Set result codes true
            Set Verbal (word) result codes true
            Set Local Echo true (displays commands)
            Disable Auto Answer
            Set Carrier Detect (CD) to disconnect when dropped
            Set Smart/Auto-Reliable mode true
            Restore modem defaults upon reset
            Read switches upon reset
            Display long form result  handshaking (flow control)
            Disable XON/XOFF flow control
            Set to RJ11 pin-out dial line
            Set to Asynchronous mode

Most of the parameters above are modem defaults for most modems sold today.  Specific commands may vary from one modem to another although most are common, e.g., ATV1 for verbal result codes.  Note that these guidelines apply to Mobile also.  In general, modem command lines should reset the modem to factory defaults (AT&F) then configure only the specific settings given above which deviate from the modem's defaults.

STUBBORN INTERNATIONAL CALLS: If following these guidelines exhaustively has not resolved international calling problems fall back to using a matched pair of 9600 Baud modems, Hayes brand recommended.  These modems are most reliable for international calling, if slow.

IV. MOBILE:

The Mobile Backgrounder application is actually a cc:Mail Router, however, the manner in which it is configured varies from the standard Router command line.  In general the same guidelines given above apply to Mobile as well.  Specifically, the user of the LSEC parameter is generally recommended for long-distance or international calls (in the 16-bit Mobile client this is set under the Mobile/Locations/Communications/Advanced options).

It is imperative to use the correct modem configuration file with Mobile.  Selecting a generic modem file or a modem file from a similar modem is not recommended.

About GSS

Global System Services Corporation (GSS) is the leading provider of consulting and professional services for large-scale and distributed infrastructure systems such as email and messaging, directory services, groupware, and wireless solutions. GSS customers include Fortune 500 companies, large services providers and telecom companies, government agencies, major messaging product vendors, and innovative technology startups.

GSS provides a complementary suite of services including strategic technology consultation and competitive vendor and product analysis, product and system architecture and design, system development deployment, customization, and testing, technical support, email migration, and other IT services. GSS has been directly responsible for some of the largest global systems and solutions and counts as customers many of the largest companies in the world.

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©1995-2005 by Global System Services Corporation (GSS). Portions of this material are copyright ©1995-1999 by Ron Herardian