[Standards] Proposed XMPP Extension: STUN Server Discovery forJingle

Peter Saint-Andre stpeter at jabber.org
Wed Mar 28 16:51:12 UTC 2007

Robert McQueen wrote:
> Peter Saint-Andre wrote:
>> Matt Tucker wrote:
>>>  * Shouldn't the port value be optional? STUN typically operates at a
>>> well-known port of 3478. If no port is specified, it would be a good
>>> idea for the client to check DNS SRV for the host first, then use the
>>> default port if that fails. 
>> True, I'll fix that.
> This strikes me as kinda inconsistent, saying in the preamble that the
> intention of this XEP is to avoid the requirement for SRV lookups on the
> server (in case this is not possible to implement), and then later
> saying that if you don't get given a port number then you have to do a
> SRV lookup. Is the rationale that you want to allow servers to get away
> without SRV records, or do you want to allow clients to get away without
> implementing SRV lookups?

Er, yes, good point. A client can already use SRV lookups to discover 
STUN servers (RFC 3489). This protocol is for use in situations where 
discovery via SRV is not possible for either of the following reasons:

1. The client does not support SRV (perhaps less likely these days since 
SRV is normally done for XMPP port discovery anyway).

2. The deployment does not support SRV (still quite common).

> Other than this, this XEP gets a +1 from me. Might be worth saying that
> the server's disco info reply should be used to find whether this
> protocol is supported.

Naturally. I'll add that before publication (if the Council approves it 
for publication).


Peter Saint-Andre
XMPP Standards Foundation

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