How fast does my connection to the Internet need to be in order to use the service?
Your connection speed (bandwidth) must be sufficiently high for the type of vocal codec you are using. Vocal codecs (or just "codec") are the standard means by which your IP Phone (UA) encodes your voice and transmits it across the Internet. The codec that is picked for a particular phone call is primarily determined by your UA's configured preferences. Consult your UA's manual to determine how to change codec preferences.
To use the best quality / highest bandwidth codecs (G711a/u) we recommend a connection speed of no less than 90Kb/s in each direction (up and down).
See the knowledgebase article on codecs for more information.