xmpp which avatar protocol to use

We are currently using openfire server for XMPP chat and serve avatars using vcards how ever there are like 4 different ways of serving avatars and some clients dont sup开发者_如何学Cport all of them.

What is the best method to use for avatars over xmpp?

XEP-0153 is the most widely-implemented, but it's the worst in almost every other direction. Please make sure to test your hashing code carefully, and to do negative caching, so that you don't end up constantly re-spamming everyone with vCard requests as fast as your client can send them out.