Tips and Tricks 4:
Accelerating Your Modem
by Calroth

SAMPLE ONLY! - INCOMPLETE!

When people buy their modems, they look for bandwidth, not speed... they
buy a 33.6K modem, or maybe a 56K. But does bandwidth make a faster
modem? Which is the faster modem?

There's quite a distinction between speed and capacity. A sports car is
fast, faster than a semi-trailer, but which would you use to transfer
your goods? Which would you use to deliver a message quickly? A 56K
modem has high capacity, but it can be slow. If you want to bring down
your ping times for IRC, or for network gaming, then you'll want to
speed your modem up.

IRC network packets and game packets are small. Their priority is to be
delivered quickly, in real-time if possible.

One part of your modem at fault is its built-in data compression. Wait,
you say. Data compression is useful. It allows quicker file transfers.
You're right, but while it helps file transfers, it slows down IRC. The
modem's compression algorithm works better with large file packets. It
doesn't work well with small IRC packets. When the modem receives an IRC
packet, it waits a short time to see if there's anything more coming,
because it can compress better with more data. After 50 milliseconds, it
realises that there isn't any more coming, and it should just compress
and send the packet that it has. That's 100 milliseconds wasted: fifty
when your modem compresses data, and fifty at your ISP's end. Add
another hundred for your remote friend's modem.

The code to add to your modem initialisation string to disable data
compression is: %C0

Another feature of your modem which takes time is error correction.
Error correction also takes time, which can be critical during a netgame
situation. On the off chance of an error...

The code to add to your modem initialisation string to disable error
correction is: \N0

Finally, one last factor is DTE speed, the speed from your computer to
your modem. You may have it preset to 38.4K, or perhaps 57.6K. As long
as it's faster than your modem, you reason. That's true, but also adds
delay. At 115.2K, an IRC packet will reach your modem in half the time
of 57.6K, and one third the time of 38.4K. Most modems and computers can
handle 115.2K or 230.4K. Set your speed as high as your modem supports.
The savings here can be small, but substantial.

While not always ideal for file transfers, the suggestions presented
here are significant and enough to lower your ping time by several
notches. When you next beat the #trivbot or pull twenty consecutive
frags, you'll come to appreciate this.

I'd like to credit Stuart Cheshire's white paper: Latency and the Quest
for Interactivity, which provided the inspiration and many examples for
this article. The HTML version can be viewed at

Calroth is the channel manager of #macintosh, and a dab hand at Quake,
Bolo and Avara. When off IRC, he's almost a formidable opponent.