[SIPForum-discussion] SIP NAPTR

[MÉSZÁROS Mihály]

Dear all!

I have a question about SIP DNS based service location, and discovery

start of example DNS zone file
============================================================================
$TTL    60
$ORIGIN atlanta.test.
@       IN      SOA     a1.atlanta.test. root.a1.atlanta.test. (
                     2010011201         ; Serial
                         604800         ; Refresh
                          86400         ; Retry
                        2419200         ; Expire
                         604800 )       ; Negative Cache TTL
;
@               IN      NS      a1
@               IN      NS      a2
a1              IN      A      
a1              IN      AAAA      
a2              IN      A      
a2              IN      AAAA      

;;                              Priority        Weight  Port    Target
_sips._tcp      IN      SRV     10              0       5061    a1
_sips._tcp      IN      SRV     20              0       5061    a2
_sip._tcp       IN      SRV     10              0       5060    a1
_sip._tcp       IN      SRV     20              0       5060    a2
_sip._udp       IN      SRV     10              0       5060    a1
_sip._udp       IN      SRV     20              0       5060    a2

;============================================================================

The zone file above can continue in my example with two versions of 
NAPTR records.

;;                              order   pref    flags   service         
regexp  replacement
@               IN      NAPTR   10      50      "s"     "SIPS+D2T"      
""      _sips._tcp
@               IN      NAPTR   20      50      "s"     "SIP+D2T"       
""      _sip._tcp
@               IN      NAPTR   30      50      "s"     "SIP+D2U"       
""      _sip._udp

OR

;;                              order   pref    flags   service         
regexp                         replacement
@               IN      NAPTR   10      50      "s"     "SIPS+D2T"      
"!^(.*)$!_sips._tcp.\\1!"      .
@               IN      NAPTR   20      50      "s"     "SIP+D2T"       
"!^(.*)$!_sip._tcp.\\1!"       .
@               IN      NAPTR   30      50      "s"     "SIP+D2U"       
"!^(.*)$!_sip._udp.\\1!"       .

My questions are:

    * The second three NAPTR RR-s are valid?
    * Are the second RR-s equialent with the first three RR-s? If not, why?

Can the regexp be not empty?
rfc3263 section 4.1 says something but not clear for me that it speaking 
about the rfc3263 example or it is a general rule.

   These NAPTR records provide a mapping from a domain to the SRV record
   for contacting a server with the specific transport protocol in the
   NAPTR services field.  *The resource record will contain an empty
   regular expression* and a replacement value, which is the SRV record
   for that particular transport protocol. 

I couldn't find a MUST or SHOLD about this behavior.

Can any of you clarify this?

If i am so lucky and my email find an expert, i hope i can ask he/she to 
clarify SIP+ NAPTR.
For example can the SIP+D2X can be so complex like this? Is it valid? Or 
if not then where is problem with it?

;;                 order pref flags service    regexp replacement
@        IN NAPTR 10 10    ""    "SIP+D2T" ""                          
redirect
redirect  IN NAPTR 5  10    ""    "SIP+D2T" ""                          .
redirect  IN NAPTR 10 10    ""    "SIP+D2T" ""                          
redirect2.
redirect2 IN NAPTR 10 10    "s"   "SIP+D2T" 
"!(.*)$!_sip._tcp.\\1!"             .


Many thanks!
Any help or suggestion highly appreciated!

Regards,
Misi
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