Compression and traffic shaping: Which, where and why?

In the never-ending quest for better network performance, two technologies – compression and traffic shaping – are often touted as bringing great advantages to enterprise networks. And while it’s true that these are both excellent solutions, you have to make sure that you’re applying the correct technology(ies) to solve the problem you’re actually experiencing.

Let’s start with compression, which boosts throughput by removing unnecessary information. Sometimes it works quite well, and sometimes it doesn’t, depending on whether the traffic you’re trying to compress is, well, compressible. In order for you to see a great deal of advantage from using compression, the information being transmitted must have repeating patterns or other recurring information that the compression algorithm can remove.

For instance, most data files are very compressible, and occasionally graphics can be compressed. Many Web pages can also be compressed quite effectively. On the other hand, some files are already in a compressed format. Compression algorithms can do very little to compress .zip files, for instance. There is a finite limit to the amount of total compression that can be achieved.

This having been said, please note our newsletter from last week (see editorial link below), which described how ITWorx, a maker of compression equipment, has reported performance acceleration of non-compressible (and compressible) traffic by adding technology to its gear that plays with the TCP window size to reduce TCP bandwidth constraints.

Generally speaking, if your problem is that large file transfers are taking too long, then using compression can be quite effective. For instance, in a recent test using an admittedly antiquated dial-up Internet access account, Steve was able to download a very large uncompressed file with an average throughput of about four or five times the modem speed. This type of acceleration also works well for faster Web surfing because of the compressibility of HTML files.

But compression isn’t a panacea. If you’re having response-time problems, you might need a different solution. Next time we’ll talk about the interplay of compression and traffic shaping.