Compression does not necessarily need to be done by the web server. It can be implemented as a proxy server installed on the same or on a standalone server. Such a server can work with any web server. It can run on a different platform under a different operating system.
If you can install a compression server on the server side and decompression on the client side, you can use better compression algorithms. Proxy-based solutions give you real power, but they usually are more sophisticated. I recommend that you use them only in the following cases:
To move compression to separate servers to reduce web server CPU load.
To compress an Internet line with traffic when web servers are not available for administration.
To use with a web server that does not support content compression.
There are several proxy-based solutions. Most of these companies have solutions for ISPs and enterprise- size networks:
Fourelle provides several compression solutions, including server- and client-side proxy: http://www.fourelle.com/
HyperSpace has a compression proxy server: http://www.ehyperspace.com/
Packeteer has AppCelera a "compression, conversion, and caching" proxy: http://www.packeteer.com/
VIGOS has the Website Accelerator, reverse-proxy software that compresses and optimizes content: http://www.vigos.com/
For maximum compatibility, consider one of these proxy solutions. They avoid problems with SSL and dynamic content. VIGOS Website Accelerator is a reverse-proxy software solution that automatically removes whitespace, optimizes graphics, compresses content, and includes their SmartShrink database, which they say eliminates HTTP compression compatibility problems.
For maximum speed, consider a hardware compression proxy. Packeteer's AppCelera ICX is a hardware/software appliance that automatically adjusts the optimization level based on the user 's browser type and connection speed. It uses compression, image optimization, and conversion from GIFs to PNGs or JPEGs, caching, and SSL processing to minimize page size. AppCelera reports on user and server response times, load, and connection profiles. Packeteer also incorporates delta encoding in their latest products.