Q1) Why do you suggest Stac/Microsoft compression and why does it reduce latency?

A1) Hardware compression built into modems 'buffers' the data in compressed 'windows' while it is being sent/received over the connection and then decompresses before sending the data over COM (serial) port. The data is only in a compressed state 'modem to modem', not the complete connection. This extra overhead and buffering in the modem itself and uncompressed data being sent over the COM (serial) port increases latency. 

Stac/Microsoft compression however compresses at the TCP/IP packet level, the data is compressed over the complete connection. With hardware compression disabled on the modem this means that data is also sent and received by the modem immediately, without buffering, which reduces latency. Removing the buffering and keeping the packets compressed while they are transmitted over the COM (serial) port also reduces load and time to send/receive over the COM (serial) port. It also stops the COM (serial) port being saturated with decompressed buffered data from the modem, this is sometimes referred to as 'buffer overrun'. The end result is reduced latency, no overruns and increased tolerance of higher game network settings such as rate, maxpackets for modem. ISDN does not have any compression by default, enabling Stac/Microsoft compression results in improved latency and increased download speeds for any compressible data.



Q2) I have enabled Stac/Microsoft Compression for my modem connection but I can no longer ping servers or browse webpages on the internet.

A2) Enable Error control as mentioned in the Optimizing a modem based dial-up connection or use a modem string to lower connect speed. In the case of ISP rack configuration problems you may have to disable IP Header Compression which can be found by clicking on TCP/IP Settings in Creating a dial-up networking connection. Having to disable IP Header Compression is unusual, contact your ISP.



Q3) When using the strings my modem returns the error 'port was already open' or refuses to even dial out. Only a reboot and removal of the string will allow me to communicate with the modem.

A3) You have used an incorrect string for your modem, if you are using the Rockwell/Conexant Chipset Based Modems strings make sure you try all the variants or see Q12) of this page. If none of the suggestions work try adding AT to the front of the strings - Example: AT%C0+MS=12,1,300,56000



Q4) When playing online although it is okay the majority of the time I do regularly/sometimes get a prolonged period of lag with very high ping or complete loss of packets.

A4) There are many reasons for this, the most likely are that your connection rate is too high and the modem is falling back/falling forward in speed or the ISP could have problems with Stac/Microsoft compression. To address the former limit your connection speed or try another modulation type as described in Modem strings for tweaks and stability, another option is to try an alternative dialup number or change ISP. If you have disabled error control then try enabling it as described in Optimizing a modem based dial-up connection.



Q5) Do you know of any utility that will help me to identify the cause of my connection problems with regard to where high ping or packet loss is occurring?

A5) Download UOTrace and use it in advanced mode. Enter the IP address of the game server you are having problems with into the box next to the 'link test' button. Click on the 'trace route' button and once the trace is complete click on the 'poll' button. The program will ping each router along the way to the game servers and you will see from the 'avg ping', highest ping', '% Lost' and 'Pkts r/s' columns where the problem is. Once you have identified the router(s) at fault highlight it and click on 'whois'. This will tell you the name and ISP at fault, if whois does not return a name then look at the hop just before and after to get an idea of who owns the router.



Q6) My connection speed varies a lot, sometimes I get 42000 other times I get 48000 what causes this?

A6) If the connection varies by a large amount it could be due to your telecommunication company exchange/ISP's telecommunication company exchange being overloaded, routing over noisy switches or your modem not adapting to new signal level in time. To address the former try an alternative ISP number which may route the call differently, if it is the latter, myth or not, some users have reported that adding commas at the end of the DUN dialup number allows time for the modem to adjust to the line dB/Noise level - Example: 08451234567,,,



Q7) I know my ISP supports Stac/Microsoft compression and others are using it with success, I however cannot seem to get compression.

A7) If your ISP supports compression and you are not getting 'Microsoft compression' / 'Stac compression' then try enabling 'Error Control' as described in Optimizing a modem based dial-up connection. In the case of ISP rack configuration problems you may have to disable IP Header Compression which can be found by clicking on TCP/IP Settings in Creating a dial-up networking connection. Having to disable IP Header Compression is unusual, contact your ISP.



Q8) When dialling in to connect I get the error 'The computer you're dialling in to does not respond to a network request.....' or similar and cannot connect to my ISP at all.

A8) This is usually a result of a problem with error control or a network protocol that cannot be negotiated. Make sure that you have setup the DUN as described in Creating a dial-up networking connection. If you have optimized your connection using Optimizing a modem based dial-up connection section then try enabling error control and removing the modem tweak string. In the case of ISP rack configuration problems you may have to disable IP Header Compression which can be found by clicking on TCP/IP Settings as described in Creating a dial-up networking connection. Having to disable IP Header Compression is unusual, contact your ISP. If you still cannot connect then either try another dialup number for your ISP or disable Stac compression and re-enable hardware compression.



Q9) I have setup my connection to automatically redial the ISP until connected, however after 10-20 dials the modem refuses to connect and always return an error. Only powering off the modem and then powering on allows me to redial/connect.

A9) Some modems/flash revisions have settings for the 'blacklist' function which will stop or delay redials to a number that has been called xx times. The xx value is set by the modem manufacturer in the flash/firmware. This will mean that once xx dials have been made only a reset of the modem or a very long delay before dialling again will allow that number to be connected to. Make sure that you have the latest flash for the modem and try to disable the blacklist function using the strings that follow:

USR/3COM modems use S40=7 or S40=2
Cirrus Logic modems use *NC9
Lucent modems use %T21,18,0
Rockwell/Conexant modems use %TCB

You may need to add AT to the command string, for example the Rockwell/Conexant string, AT%TCB. See Optimizing a modem based dial-up connection for information on where to enter modem strings.



Q10) My Rockwell/Conexant chipset based modem is flashed to V90 yet I still cannot get connection speeds greater than 31200 or 33600. The ISP I am using does support v90 on the number I am dialling.

A10) Some Rockwell/Conexant chipset based modems require the string S202=32 (ATS202=32) to allow V90 connection to dialup racks such as 3Com. See Optimizing a modem based dial-up connection for information on where to enter modem strings.



Q11) What is the best ISDN card or TA for online gaming?

A11) Avoid an external ISDN TA no matter if it is USB or serial, always buy an internal PCI card or ISA card. Internal ISDN cards can be split into two types, passive and active/semi-active. The best passive ISDN cards for online gaming are the Asuscom ISDNLink PCI P-IN100-ST-D and the Eicon Diva 2 standard. The only active/semi-active card worth mentioning for online gaming is the Eicon Diva 2 Pro, expensive and only really worth the extra money if you wish to use its V34 modem features.



Q12) There are many string variants for Rockwell/Conexant chipset based modems. How do I know which string to use without testing each one in turn?

A12) Use a communications package such as Hyperterminal and set it up to communicate with the modem. Enter AT+MS=? at the prompt and a syntax template will be shown. Compare the template shown with those listed in the modem strings section for Rockwell/Conexant Chipset Based Modems.



Q13) The error codes displayed after failing to connect are not very helpful as they are just numbers. What do the numbers mean?

A13) Some versions of Windows offer a help and trouble shooting option after a failed connection. If your version of Windows does not or you just want a complete list of error codes and their meaning you can find them in the DialUp Networking Error Codes section of this guide.



Q14) I have setup my modem connection as described in the guide and my pings are much lower while allowing me to have a higher rate and FPS setting. However I regulary get disconnected from my ISP.

A14) Try adding the string S10=60 to the front of any string you are using, this will help with noisy line conditions. See Optimizing a modem based dial-up connection for information on where to enter modem strings. You could also try lowering the connect speed using a modem string. If you have disabled error control then try enabling it as described in Optimizing a modem based dial-up connection.



Q15) Just after joining a game my pings quickly rise to 999+, it is definitely not my game settings as I have checked those.

A15) There is a known timing bug in the TCP/IP stack for Windows9x which causes packets to be resent, this can flood an upstream connection. Make sure you have installed the latest updates for your system and then backup the file called Vtcp.386 in your windows/system directory. Download and install the Windows95 or Windows98 TCP/IP patch that addresses this problem and then reboot. If the problem persists or there are other issues caused by installing the patch replace Vtcp.386 with the one from the backup.



Q16) What is V.92?

A16) V.92, sometimes called V90+, is a standard to improve upstream(upload) speeds over the current 33600 maximum upstream speed of V90. The proposal also includes improved connection times and call waiting compatibility. Current modems may be flash upgradable but the ISP must also be running V92 capable dialup racks. Currently on target for late Summer 2000. Update: July 4th 2000 The ITU have agreed on the V.92 standard. Press release can be found at the ITU website. Update: June 2001, V.92 is now appearing in modems.