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Maximising Modem Performance for the Internet

Most modern modems and software will work straight away without complex configuration or a need for a detailed understanding. There are however a number of simple things which one can do to maximise the speed of transfers achieved and the reliability of the connection. This document gives some hints on how to get the maximum out of your modem and some shortcuts when configuring, for example, for Internet connections. It also explains some of the jargon which is endemic in the communications field. Windows 95 has made communications much easier but it is still a poorly documented maze.

In order to get the best from a modem it helps to understand a little about how the data communication takes place. The latest modems contain considerable in-built computing power (or in some cases of internal PCI modems use the main CPU's power) which allows them to carry out error correction and data compression to get high speed data communication over noisy low bandwidth telephone lines. They are capable of negotiating with other modems to ensure the type and speed of connection is optimised. You do not have to know what is at the other end but you one thing you can be sure of is that all the facilities available on his equipment will be enabled by an Internet Service Provider (ISP) or service such as CompuServe or AOL or they would rapidly go out of business. What you have to make sure that your modem has all the facilities it has available turned on. In many cases this will be the default when the modem is turned on but your software must either leave them turned on or know about how to use them - more of that latter.

So far we have been speaking about the link between the two modems over the telephone lines - there is however the link between the computer and the modem and it is here that many users lose performance. This is also the link most likely to be left to the user to configure. The first and most important thing is that the speed must be set as high as possible the modem will try and usually succeed in establishing a connection where the data is compressed which increases the effective transmission speed. For example a 28.8K V34 modem will use try to use the V42bis protocol which can compress by up to four times allowing a data throughput of up to 115.2K.. If you only set 28.8K there will a bottleneck into the computer which will not create errors just slow the transfers without the naive user ever realising! Do not however expect an overall improvement of 4x as compression varies on the type of data and many of the big downloads you will do are of data which has already been compressed where there will be few benefits. The best known type of compressed data is Zipped data (.ZIP). Graphic data is also usually in a compressed form (eg the .GIF and .JPG files used on Web sites) where again you will not see all the benefits.

As well as setting a speed most programmes will need to be told what sort of modem you have. In most cases everything will work if you either let the system autodetect the modem or just tell it that it is a Standard Modem but this may not allow all the facilities to be accessed. Windows 95 has a large number of Modems you can choose otherwise the Modem supplier will probably have provided you with a disk with a suitable driver to install. This is worth doing once you have got the system all up and running and you will then find that a number of boxes in the Windows 95 modem configuration are no longer "greyed out" and you can not only explicitly turn on data compression and error correction but also specify that you will only accept such connections. This ensures robust links and, as explained above, can give dramatic improvements. There is a separate page covering Installing a Modem under Windows 95/98

If you are using a programme which does not use the Windows 95 Modem software, which is however quiet unusual these days, then you need to do the same sort of configuration but it may not be possible to use the drivers provided and here it become more difficult. Early versions of CompuServe, for example, provided quite a lot of drivers and then the ability to fine tune by setting up the modem commands for turning on and off particular facilities. The commands for configuring are sent down the serial line as text strings before the Modem starts to send and receive data and the basic set are almost always what are called Hayes Compatible as Hayes produced the first modems using this type of set up and hence the de facto standard. The modem also sends back responses as text strings which the software recognises. The problem is that many of the advanced features are not completely standard between modems and you may have to read the manuals very carefully and experiment unless the modem provider extracts the relevent information for you.

Even if you use the Windows 95 Modem there are a few things which can catch the unwary. The Modem software sends the various strings to configure the Modem and looks at the responses to see that they make sense. It then dials the number you set up and again checks to see that there is dial tone and that a connection has been established and tells you what the modem has reported. Different modems report in different ways however and when Windows 95 (or other programmes) tell you that you have a connection at 28.8K this can mean different things. Some Modems report the speed between the Computer and the Modem so you always get what you set - others will report the speed of connection which has been established. Most are also capable of reporting the actual protocols which have been negotiated for error correction and data compression which depend , as discussed above, on the modems at each end of the line and the quality of line. Windows 95 only gives the speed when it tells you are connected so you only have part of the story. You can however generate a log file of what has gone on by checking a box and this is worth doing whilst you are optimising the system and this will tell you what has been sent and received by the modem (but not all the data!). You should not leave the log file on permanently as the information is appended so it gets bigger and bigger!

You can experiment with the commands by using a terminal programme in the computer connected to the correct port. The modem will work out the speed but in this case there is no point in setting it too high as the computer may not keep up. Windows 3.1 has a terminal programme which made this simple but Windows 95 is too sophisticated and the Hyperterminal does not expect you to want to do simple things and you have to create a test connection with, for example, your own number. You can alternatively creating a dummy Dial Up Network connection and turning on check box to bring up the terminal screen before dialling. Try simple commands such as AT <return> which does nothing but echo back OK and AT&F which does a reset and replies OK. This is also the first thing to do if you have any doubts about whether the Modem is working. You can then work through the commands you have decided are what are needed to get the best out of the modem and dial up and even see what is reported for a connection. I should however emphasise that you should not need to do this if the Modem Supplier gives proper support.

I will now go on to how to connect to Internet from Windows 95. In the early days this caused a great deal of grief but in practice I have found it very easy although we do run straight back into the alphabet soup. I did not get any real success until I understood a little of how the Internet works and the way that a PC couples into it. This is best thought of as a series of layers. The top layer is your application programme such as your Browser. This connects through a Windows Socket which is a programme (More correctly a Dynamic Linking Library (DLL)) called Winsock.dll. Winsock.dll sits in the machine and when Internet Explorer or any other application wants to communicate it takes control of the modem and dials up a connection to your Internet Provider (IP) (a Point of Presence PoP in the jargon) and establishes a your link. This socket Winsock.dll usually remembers your password as well as the telephone numbers etc. once it has been configured. It also needs to know lots of other pieces of information to set up the Internet connection.

We have now got to Internet Provider which is really just another computer with lots of modems connected which routes the communications. The type of connection used is normally called a PPP (Point To Point) connection and the protocol is TCP/IP - you need to know that much to help understand how to configure your connection . You also need to understand how the information is sent around to understand other bits of jargon.

Firstly every user and site on the World Wide Web (Internet) has a unique address - this is the 12 figure number you sometimes see on the browser status displays in 4 groups of three figure numbers separated by periods. This is fixed in the case of Web sites but may be transient for users connecting through a service provider which will have been allocated a big block of addresses one of which is allocated to you for as long as you are connected. The familiar addresses, otherwise know as domains, such as www.microsoft.com have to be translated to the numeric addresses. This is done by what is called a domain name server (DNS) - a big look up table at your provider for common sites which also knows other DNSs to search for sites it does not hold locally. These DNSs have addresses just like any other site.

Once the address is known the data is sent off in an appropriate direction in little packets each of which has a header so it knows where it came from and where it is going (like an envelope round a letter). They may have to go through many machines to get to there destination and there are many different routes they can take between the interconnected machines and the route will depend on which routes are available and their loading. Not all packets making up a message need go the same way but usually do. There is built in error checking and correction in that when the message is received a confimatory message is sent back - if a confirmation is not received then another set of packets is sent off. All this is completely invisible but explains why the times can vary so much and why the addresses are so important. Your communications software needs to know what your address is for the replies and where to start to look up the absolute address of the destination. Hint: All the major providers I have tried allocate a name to you and also tell you the DNS so when you configure the system all you need to do is check the boxes marked Server Assigned IP address and Server Assigned DNS.

Windows 95 does a lot of the hard work for you in setting up the connection and hides from you things like Winsock.dll which is fine if you only use what is called Dial Up Networking (DUN) to connect to the Internet. Although it is unlikely these days it is worth noting that is that DUN does create and use a Winsock.dll which may overwrite or conflict with the ones installed already by early versions of service providers software. If you think you may have legacy software then start by searching for all the winsock.dll on the system. There should be two from Microsoft in Windows Folders which are about 42K in length and those are the ones you need. The other thing to remember is that the Windows 95 Dial Up networking is for 32 bit programmes - this is correct for most of the new software you will want to use including the excellent new free Browser from Microsoft, Internet Explorer 3.0 (shows when this was first written - we are now on IE 5) . Windows 98 has an upgraded Winsock (version 2) which can be downloaded for use with Windows 95 - this is suggested with some software.

You may ask why it is called a Dial Up Networking connection - this is because the Internet is just regarded as any other network connect made over the telephone by Windows 95. This does mean that Dial Up Networking must be installed and configured to include TCP/IP as one of its network protocols before you start the real business. It also means that you have to make sure you are configured as a user with a log in password otherwise the system is not considered secure and it refuses to save your Internet Provider password, quite logical but not made clear in any documentation I have found.

The above all makes it sound very difficult to set up Windows for Internet connections. It took me several hours the first time mainly because I did not understand what or why I was doing things, hopefully the information above combined with some specific instructions will make it much easier for you. The last time certainly only took me a few minutes to configure an additional connection to a new service provider. A number of ISPs such as FreeServe are covered explicitely in the Howto Technical Articles series on how to do this and a Guide to Selecting an ISP

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Copyright © Peter and Pauline Curtis
Content revised: First Written: 3rd October, 1996
Content revised: 29th July 1999
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