[Standards] updated STUN discovery proposal

[Sean Egan]

On 4/19/07, Peter Saint-Andre <stpeter at jabber.org> wrote:
> "STUN servers will change all the time" was not among his reasons. But
> he can defend his reasoning better than I can...

I'm mostly fine with as long as we can put a "username" and "password"
attribute in there to allow for authentication with the STUN server.

These username and password values will probably want to expire for
security on many implementations. That's a good enough reason to
consider these values to "change all the time."