It maybe that you're using several mods that are spamming addon traffic. Carbonite may look like the culprit because it's traffic is easily visible due to the custom channels that it uses. However, many addons use hidden chat messages (that are sent via normal channels, but aren't displayed by the WoW client under normal operation).
In order to see what's really going on you either need to enable chatlogging or, better yet, use
Spamalyzer to see all of that hidden addon spam and/or see total I/O figures by addon.