Re: [reSIProcate] How does a client build a DNS lookup that restr icts the responses to UDP?
Good deal. I missed that in the RFC. On another look at sec. 4.1, I see it
doesn't say to not use NAPTR if the transport is specified but the port is
not. Rather, I see it just says to use NAPTR if neither the transport or
port are specified. So, if the transport is specified, it just uses the
default SRV for _sip._udp? If there's a line that explictly says how this
works regarding the default SRV record, that will help.
Thanks, yall have helped a lot.
Dave
-----Original Message-----
From: Byron Campen [mailto:bcampen@xxxxxxxxxxxx]
Sent: Thursday, December 07, 2006 1:07 PM
To: Dave Mason
Cc: resiprocate-devel@xxxxxxxxxxxxxxxxxxxx
Subject: Re: [reSIProcate] How does a client build a DNS lookup that restr
icts the responses to UDP?
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
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>