[Users] OpenSER and transport selection (SRV and NAPTR)

Joachim Fabini Joachim.Fabini at tuwien.ac.at
Fri Dec 16 11:02:35 CET 2005


Hi Bogdan, 

> the host (like name) is mandatory - if no port and no proto is given, 
> you will use the host name (sip.com) to do NAPTR lookup to get the 
> supported protos and than SRV lookup to get the machine name and port.
> 
> if only the port is missing, only SRV lookup will be done to get the 
> machine name and port.
> 
> if only proto is missing, it will be assumed UDP and normal 
> (A record) DNS lookup performed.

Hmmh, seems to me that there's a slight misunderstanding 
here. The new function should imho also replace the current 
t_relay() - from the user's point of view this means for me: 
route the message statefully to the next hop.

The user does not need to (and can not, except he does
the RFC3263 resolution manually) specify a destination 
proxy - OpenSER should be able to determine it according 
to the SIP DNS resolution rules (RFC 3263). 

So my point of view: if no host is passed, OpenSER uses 
the destination URI to query the DNS (NAPTR) to determine 
what protocol the destination proxy prefers (Samuel made
the correct point in his email, RFC 3263 states that the 
destination proxy must decide on the protocol to use) 
and then must do the SRV record and possibly A record 
lookup for the correct host to contact. 

> time? hard to say...until the next release anyhow...

Doesn't sound too optimistic if we need it in the next 
three months, right?... ;)

Thanks,
best regards
--Joachim





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