Administrator’s Guide for SIP-T5 Series Smart Media Phones
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is unimportant as there is no other record with order 90. The flag “s” indicates performing the
SRV query next. TCP will be used, targeted to a host determined by an SRV query of
“_sip._tcp.yealink.pbx.com”. If the flag of the NAPTR record returned is empty, the IP phone will
perform NAPTR query again according to the previous NAPTR query result.
SRV (Service Location Record)
The IP phone performs an SRV query on the record returned from the NAPTR for the host name
and the port number. Example of SRV records:
Priority Weight Port Target
IN SRV 0 1 5060 server1.yealink.pbx.com
IN SRV 0 2 5060 server2.yealink.pbx.com
Parameters are explained in the following table:
Specify preferential treatment for the specific host entry. Lower
priority is more preferred.
When priorities are equal, weight is used to differentiate the
preference. The preference is from highest to lowest. Keep the same
to load balance.
Identify the port number to be used.
Identify the actual host for an A query.
SRV query returns two records. The two SRV records point to different hosts and have the same
priority 0. The weight of the second record is higher than the first one, so the second record will
be picked first. The two records also contain a port “5060”, the IP phone uses this port. If the
Target is not a numeric IP address, the IP phone performs an A query. So in this case, the IP
phone uses “server1.yealink.pbx.com" and “server2.yealink.pbx.com" for the A query.
A (Host IP Address)
The IP phone performs an A query for the IP address of each target host name. Example of A
records:
Server1.yealink.pbx.com IN A 192.168.1.13
Server2.yealink.pbx.com IN A 192.168.1.14
The IP phone picks the IP address “192.168.1.14” first.
Procedure
SIP Server Domain Name Resolution can be configured using the following methods.
Central Provisioning
(Configuration File)
Configure the transport method on the IP
phone.
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