Aastra 9000i Series Administrator's Manual page 678

•
You can configure up to 4 DNS SRV records, with each server having a priority which tells the
phone which server to use, and a host name or target. The IP phone will use the DNS SRV record
with the lowest-numbered priority value first, and will only failover to other records if the
connection with this record's host fails. Thus a service may have a designated failover server,
which is only used if the primary server fails.
If a service has multiple SRV records with the same priority value, the IP phone(s) use the weight
field to determine which host to use. The weight value is a ratio compared to the weight of other
records with the same name and priority value.
In the following example, both the priority and weight fields are used to provide a combination of
load balancing and backup service.
Example
sip dns srv1 name: _sip._udp.example.com
sip dns srv1 priority: 10
sip dns srv1 weight: 60
sip dns srv1 port: 5060
sip dns srv1 target: bigbox.example.com
sip dns srv2 name: _sip._udp.example.com
sip dns srv2 priority: 10
sip dns srv2 weight: 20
sip dns srv2 port: 5060
sip dns srv2 target: smallbox1.example.com
sip dns srv3 name: _sip._udp.example.com
sip dns srv3 priority: 10
sip dns srv3 weight: 20
sip dns srv3 port: 5060
sip dns srv3 target: smallbox2.example.com
sip dns srv4 name: _sip._udp.example.com
sip dns srv4 priority: 20
sip dns srv4 weight: 10
sip dns srv4 port: 5060
sip dns srv4 target: backupbox.example.com
The first three records (SRV 1, 2, and 3) share a priority of 10, so the weight field's value is used
by the phones to load balance across the three target host names.
Bigbox will get 60% of the load, and smallbox1 and smallbox2 will each get 20% load.
41-001343-01 Rev 02, Release 3.2.2
Note: The "X" indicates a DNS SRV with a value from 1 to 4.
Note: The "sip dns srvX weight" parameter must be configured but the
phones will support this feature in a future release.
6-57