I'll have to 100% disagree with this statement.

NAPTR and SRV are how it should always be done.  Toss in some GEO dns and you have many of the problems solved.  SRV records should never be optional they should be required to function properly.  The NATPR records order preference of records which works in many hard and soft phones.

Example which this works:

<92>:host -t NAPTR bkw.org
bkw.org has NAPTR record 10 10 "s" "SIPS+D2T" "" _sips._tcp.bkw.org.
bkw.org has NAPTR record 20 20 "s" "SIP+D2S" "" _sip._sctp.bkw.org.
bkw.org has NAPTR record 30 30 "s" "SIP+D2T" "" _sip._tcp.bkw.org.
bkw.org has NAPTR record 40 40 "s" "SIP+D2U" "" _sip._udp.bkw.org.

<93>:host -t SRV _sips._tcp.bkw.org
_sips._tcp.bkw.org has SRV record 10 0 5061 sip.bkw.org.

<94>:host -t SRV _sip._sctp.bkw.org.
_sip._sctp.bkw.org has SRV record 10 0 5060 sip.bkw.org.

<95>:host -t SRV _sip._tcp.bkw.org.
_sip._tcp.bkw.org has SRV record 10 0 5060 sip.bkw.org.

<96>:host -t SRV _sip._udp.bkw.org.
_sip._udp.bkw.org has SRV record 10 0 5060 sip.bkw.org.

With these records in place my Eyebeam will register to my FreeSWITCH instance via TLS since it was listed as the highest preference.  The same goes for my Snom phones on my desk.  They see the NAPTR's, SRV's and do exactly what I told them to do via DNS.

The internet wouldn't exist today without DNS and if your DNS is that fragile you need to figure out why because without it we would be in for a world of hurt.... Not sure about you but I don't wanna remember what 4 billion IP's go to.

Bottom line is NO SRV NO NAPTR you're doing it wrong in my opinion because as a SIP UA you have to look them all up anyway since its NOT optional as per the spec.

/b


On Oct 29, 2008, at 6:54 PM, Yuval Hertzog wrote:

4. I would strongly recommend reconsidering the use of any DNS feature (such as SRV records) when deploying a telephony infrastructure. Of course, it all depends what this deployment is for. DNS is commonly used in the ITSP space due to the vast audience but enterprises (all sized) are recommended to refrain adding DNS to the list of point-of-failures in their telephony architectures.