Many applications may have external users, who need to connect to the database remotely and access or exchange database data, often over dialup, satellite or public wide area networks. There are two key issues here: firstly that by using public band widths there is a security risk. Secondly, even reasonable amounts of data can congest a poor band width without compression.
Compression reduces the file size, which increases speed. However the big issue for connection speed is latency, which can be measured for example by pinging the server. Latency is a more critical factor than the bandwidth.
Many people set up VCNs through to their service, which solves both issues. The VPN does the compression for you and provides you with a secure tunnel. Alternatively there is an excellent free tool on the market, Zebedee, offering a tunnel that can be used to compress and encrypt the TCP traffic between the Firebird server and the client, similar to SSH or SSL. Basically you have a small piece of software sitting on the server and on the client. You need to specify some port redirections and it listens on one port, decompresses the data and pushes it through to the correct port where the Firebird server (or Firebird client) can be reached. By return it compresses and encrypts data going out. It is even possible to specify client ID files so that the connection is only allowed when the respective client ID files are available both on the server and the client.
The software can be downloaded from http://www.winton.org.uk/zebedee and is available for Windows, Linux and Unix. It is open source and completely free.