Re: [reSIProcate] How does a client build a DNS lookup that restr icts the responses to UDP?

[Byron Campen <bcampen@xxxxxxxxxxxx>]

	This is the behavior specified in RFC 3263, so DNS admins should be  
expecting it (although 3263 can be a little tricky to wade through).

Best regards,
Byron Campen

> Hi, I just found a quick followup...
>
> I find that if I do a lookup with a URI such as
> "sip:user@xxxxxxxxxx;transport=udp", the library ignores the NAPTR  
> records
> and chooses the _sip._udp.<domain.com> SRV record.  Thus, if the DNS
> response has a NAPTR with a different preference for UDP such as
> _sip2._udp.<domain.com>, it will be ignored in favor of the default.
>
> Is this a known condition that DNS admins will take into account,  
> or should
> I first do a lookup without it, and search those results for UDP  
> transports?
> If none are found, then I do a lookup with ";transport=udp"  
> appended to
> guarantee a UDP response?  (I hate to do two lookups if I don't  
> need to.)
> What's the proper way to use the library (DnsInterface class) for  
> this case?
>
> Regards,
> Dave
>
>
> -----Original Message-----
> From: Byron Campen [mailto:bcampen@xxxxxxxxxxxx]
> Sent: Tuesday, December 05, 2006 5:04 PM
> To: Dave Mason
> Cc: resiprocate-devel@xxxxxxxxxxxxxxxxxxxx
> Subject: Re: [reSIProcate] How does a client build a DNS lookup that
> restricts the responses to UDP?
>
>         Well, you can always do sip:user@xxxxxxxxxx;transport=udp. Also, if
> your stack doesn't support TCP, it should use UDP instead. Lastly,  
> if there
> are no TCP SRVs in DNS, you should also get UDP results.
>
> Best regards,
> Byron Campen
>
> > Hi,
> >
> > I find that if a DNS server is set up with NAPTR records for a domain
> > that specify TLS/TCP is most preferred, then TCP, the UDP last, and a
> > client does a DNS lookup for sip:user@xxxxxxxxxx (through
> > DnsInterface), the DNS server only returns records for TLS/TCP.
> >
> > How do you configure the lookup on the client side to ask for only  
> > UDP
> > records, even if they are least preferred on the server?
> >
> > Regards,
> > Dave
> > _______________________________________________
> > resiprocate-devel mailing list
> > resiprocate-devel@xxxxxxxxxxxxxxxxxxxx
> > https://list.resiprocate.org/mailman/listinfo/resiprocate-devel

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