I'm following up on my last rant on multiple transports. It's a topic with nuance, but I still think it's a worthwhile caution to avoid multiple transports in non-realtime standard protocols.

Yngve talked about multiple transports used by Opera Mini for cell phone Web browsing. This is in the context of what appears to be a proprietary protocol; at least it's not standardized. Opera Mini talks to a transcoder run by Opera, so interoperability is mostly handled by not having multiple vendors of the client or the server. Skype was another example, but again Skype does not use a standard. More generally, Yngve talked about TCP-based applications that need to bypass firewalls and can use HTTP as a tunnel. Yngve, you're right about the general world of protocols, but what do you think about broadly standardized protocols?

Ralph and Joe pointed out that there are multiple implementations of BOSH, the HTTP binding for XMPP. This is interesting; I was aware of the proposal but had no idea how widely adopted it is. If it really becomes universally supported in servers, then we could write any new application on top of XMPP and it will work over HTTP as well as natively over TCP. Now that's interoperability!