Sip Server Domain Name Resolution - Matrix Sparsh VP110 User Manual

If the outbound proxy server is required and the transport is set to DNS-NAPTR, you must set the port of
outbound proxy server to 0 for NAPTR, SRV and A queries.

SIP Server Domain Name Resolution

If a domain name is configured for a SIP server, the IP address (es) associated with that domain name will be
resolved through DNS as specified by RFC 3263. The DNS query involves NAPTR, SRV and A queries, which
allows the IP phone to adapt to various deployment environments. The IP phone performs NAPTR query for the
NAPTR pointer and transport protocol (UDP, TCP and TLS), the SRV query on the record returned from the
NAPTR for the target domain name and the port number, and the A query for the IP addresses.
If an explicit port (except 0) is specified and the transport type is set to DNS-NAPTR, A query will be performed
only. If a SIP server port is set to 0 and the transport type is set to DNS-NAPTR, NAPTR and SRV queries will be
tried before falling to A query. If no port is found through the DNS query, 5060 will be used.
The following details the procedures of DNS query for the IP phone to resolve the domain name (for example,
matrix_ippbx.com) of working server into the IP address, port and transport protocol.
NAPTR (Naming Authority Pointer)
First, the IP phone sends NAPTR query to get the NAPTR pointer and transport protocol. Example of NAPTR
records:
order pref flags
IN NAPTR 90 50
IN NAPTR 100 50
Parameters are explained in the following table:
Parameter
order
pref
flags
service
regexp
Matrix SPARSH VP110 User Guide
service regexp
"s" "SIP+D2T" ""
"s" "SIP+D2U" ""
Specify preferential treatment for the specific record. The order is from
lowest to highest, lower order is more preferred.
Specify the preference for processing multiple NAPTR records with the same
order value. Lower value is more preferred.
The flag "s" means to perform an SRV lookup.
Specify the transport protocols:
SIP+D2U: SIP over UDP
SIP+D2T: SIP over TCP
SIP+D2S: SIP over SCTP
SIPS+D2T: SIPS over TCP
Always empty for SIP services.
replacement
_sip._tcp.matrix_ippbx.com
_sip._udp.matrix_ippbx.com
Description
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