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

[Robert Sparks]

On Dec 7, 2006, at 12:22 PM, Dave Mason wrote:

> Hi, I just found a quick followup...
>
> I find that if I do a lookup with a URI such as
> "sip:user at domain.com;transport=udp", the library ignores the NAPTR  
> records
> and chooses the _sip._udp.<domain.com> SRV record.
This is what 3263 specifies. Putting ;transport=udp in the URI  
selects the transport, so you
skip NAPTR.
> 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.
Correct.
>
> Is this a known condition that DNS admins will take into account,
yes. (But they have to read 3263 to know to do it).
> 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 at estacado.net]
> Sent: Tuesday, December 05, 2006 5:04 PM
> To: Dave Mason
> Cc: resiprocate-devel at list.resiprocate.org
> Subject: Re: [reSIProcate] How does a client build a DNS lookup that
> restricts the responses to UDP?
>
> 	Well, you can always do sip:user at domain.com;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 at domain.com (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
>> _______________________________________________
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>> resiprocate-devel at list.resiprocate.org
>> https://list.resiprocate.org/mailman/listinfo/resiprocate-devel
>
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