|Informative Information for the Uninformed
Aside from the basic network design issues, other problems have arisen from the fact that Blizzard did not expect, or intend for, third party programs to use its Battle.net protocol. As a result, proper validation has not always been in place for certain conditions that would not be generated through the Blizzard client software.
As mentioned earlier, many developers eventually turned to the using the Battle.net protocol directly as opposed to the text-based protocol in order to circumvent certain limitations in the text-based protocol. There are a number of reasons for this. Historically, clients utilizing the Battle.net protocol have been able to enter channels that are already full (private channels on Battle.net have a limit of 40 users, normally), and have been able to perform various account management functions (such as creating accounts, changing passwords, managing user profile information, and so-forth) that are not doable through the text-based protocol.
In addition to having access to extended protocol-level functionality, clients using the Battle.net protocol are permitted to open up to eight connections to a single Battle.net network per IP address (as opposed to the text-based protocol, which only allows a single connection per IP address). This limit was originally four connections per IP address, and was raised after NATs, particularly in cyber cafes, gained popularity.
This was particularly attractive to a number of persons on Battle.net who used third-party chat clients for a variety of reasons. The primary reason was generally the same ``channel war'' phenomenon that has historically plagued IRC was also rather prevalent on Battle.net, and being able to field a large number of clients per IP address was seen as a significant advantage.
Due to the prevalence of ``channel wars'' on Battle.net, artificially large numbers of third-party clients utilizing the Battle.net protocol came into use. Although it is difficult to estimate the exact number of users of such clients, the author has observed upwards of several thousand being logged on to the service at once.
The development and usage of said third party clients has resulted in the discovery of a number of other issues with Battle.net. While most of the issues covered here are either already fixed or relatively minor, there is still value in discussing them.