Yealink SIP-T4X Administration Manual page 180

Parameters are explained in the following table:
Parameter
Specify preferential treatment for the specific record. The order
order
is from lowest to highest, lower order is MORE preferred.
Specify the preference for processing multiple NAPTR records
pref
with the same order value. Lower value is MORE preferred.
flags The flag "s" means to perform an SRV lookup.
Specify the transport protocols supported by the domain server:
SIP+D2U: SIP over UDP
service SIP+D2T: SIP over TCP
SIP+D2S: SIP over SCTP
SIPS+D2T: SIPS over TCP
regexp
Always empty for SIP services.
replacement
Specify a domain name for the next query.
The IP phone picks the first record, because its order of 90 is lower than 100. The pref
parameter 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.example.com". If the flag of the NAPTR record
returned is empty, the IP phone will perform the NAPTR query again according to the
previous NAPTR query result.
SRV (Service Location Record)
The IP phone performs a SRV query on the record returned from the NAPTR for the host
name and the port number. Example of SRV records:
Priority Weight
IN SRV 0 1
IN SRV 0 2
Parameters are explained in the following table:
Parameter
Specify preferential treatment for the specific host entry. Lower
Priority
priority is MORE preferred.
When priorities are equal, weight is used to differentiate the
Weight preference. The preference is from highest to lowest. Keep the
same to load balance.
Port Identify the port number to be used.
Target Identify the actual host for an A query.
Description
Port Target
5060 server1.example.com
5060 server2.example.com
Description
Configuring Advanced Features
165