AASTRA 6700i series, 9143, 9480i, 9480i CT SIP Administrator Guide EN - Manual (Page 977)

A-246 41-001343-01 Rev 03, Release 3.2.2
DNS Query Setting
Parameter–
sip dns query type Configuration Files aastra.cfg, <mac>.cfg
Description Specifies the Domain Name Service (DNS) query method to use when the IP
Phones issue requests for DNS records using one of three methods: “A” only,
SRV& A, and NAPTR & SRV & A.
Format Integer
Default Value 1
Range 0 A only - The phone issues requests for “A” (Host IP Address) records
from the DNS server to get the IP address, and uses the default port
number of 5060.
1 SRV & A - The phone issues requests for “SRV” (Service Location
Record) records from the DNS server to get the port number. Most
often, the IP address is included in the response from the DNS server
to avoid extra queries. If there is no IP address returned in the
response, the phones send out the request for “A” records from the
DNS server to find the IP address.
2 NAPTR & SRV & A - First, the phone sends "NAPTR" (Naming
Authority Pointer) lookup to get the “SRV” pointer and service type. For
example, if Global SIP transport protocol on the phone is “UDP”, and
Proxy server on the phone is “test.aastra.com”, then:
1. If the NAPTR record is returned empty, the phone will use the
default value “_sip._udp.test.aastra.com" for the “SRV” lookup.
2. If the NAPTR record is returned "test.aastra.com SIP+D2U ....
_sip._udp.abc.aastra.com", the phone will use
“_sip._udp.abc.aastra.com" for the “SRV” lookup.
3. If the NAPTR record is returned "test.aastra.com SIP+D2T ....
_sip._tcp.test.aastra.com", where the service type TCP mismatches
the phone configured transport protocol “UDP”, the phone will ignore
this value and use the default value “_sip._udp.test.aastra.com" for the
“SRV” lookup.
Note: The phone does not use the service type sent by the NAPTR response
to switch its transport protocol, nor does it use the NAPTR response to
determine whether to use a secure or unsecure communication path
. The
phone will always use a global sip protocol that is configured on the phone
via configuration files or web user interface.
After performing NAPTR, the phone sends “SRV” lookup to get the IP
address and port number. If there is no IP address in the “SRV” response,
then it sends out an “A” lookup to get it.
Note: On the phone side, if you configure the phone with a Fully- Qualified
Domain Name (FQDN) proxy and specified port, the phone always sends “A
only” lookups to find the Host IP Address of the proxy.
Example sip dns query type: 2