[jdev] dialback

Peter Saint-Andre stpeter at jabber.org
Tue Jun 6 11:29:42 CDT 2006

Hash: SHA1

Ben Turner wrote:
> On Fri, Jun 02, 2006 at 09:02:55AM -0600, Peter Saint-Andre wrote:
>> If Server1 does not support XMPP 1.0 (including TLS), it MUST NOT
>> include the version='1.0' attribute in the stream header it sends to
>> Server2. However, if it supports dialback it MUST include the dialback
>> namespace declaration in the stream header it sends to Server2. So if
>> Server1 supports only dialback and not TLS, it would send:
>> <stream:stream
>>        xmlns='jabber:server'
>>        xmlns:stream='http://etherx.jabber.org/streams'
>>        xmlns:db='jabber:server:dialback'
>>        to='Server1'>
>> If Server2 detects that the stream header from Server1 does not include
>> the version='1.0' attribute but does include the dialback namespace
>> declaration, then it MUST NOT attempt to perform TLS negotiation.
>> If Server2 breaks that rule and attempts to perform TLS negotiation
>> anyway (BAD SERVER, BAD!), Server1 would in all likelihood simply close
>> the stream with </stream:stream> (since it is probably an older server
>> implementation) but it might first send an appropriate stream error,
>> such as <not-authorized/> or <unsupported-stanza-type/> (though in
>> practice this is doubtful).
> Hi Peter,
> Thanks for that bit of info.
> Another quick question. If server1 (which supports TLS) attempts to connect with
> server2 (which _doesn't_ support TLS) and server1 discovers this fact through
> the absence of a version='1.0' in server2's stream header, is server1 supposed
> to keep using the same TCP connection or open a new one? 
> I have noticed that Wildfire opens a new TCP connection once it discovers that
> dialback is required, it even sends a stream header without version='1.0' after
> opening the new TCP connection. Why not just keep using the already opened TCP
> connection?

I see no particular reason to close the TCP connection. Degrading
gracefully to "XMPP 0.9" on the same TCP connection seems preferable.


- --
Peter Saint-Andre
Jabber Software Foundation

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