SRV (SeRVice) records allow flexibility and stability to services making use of them. Like a "general use" MX record, the SRV records relate to a particular service of the domain, like FTP or SIP, rather than a specific machine the way A or C-name records do.
Several programs are starting to make use of SRV records for VOIP.
An OnSIP customer would create an SRV record to take the place of the domain.onsip.com address given by default. With an SRV record a user with the SIP address of:
could become just:
assuming that the user can create an SRV record for acme.com.
For OnSIP, when setting up a SRV record, the general settings are:
Name: acme.com (your domain name goes here)
TTL: 1 hour
In BIND, an SRV record would look like this:
_sip._udp.acme.com. 3600 IN SRV 0 0 5060 sip.onsip.com.
To test that the SRV record has been entered correctly you need to run the
dig command from a terminal window on a Unix/Linux system (including OS X).
For Windows see the
The following screen shot shows the command:
dig _sip._udp.bytetel.com SRV (replace bytetel.com with your domain name but keep everything else there).
If everything has been set up correctly you will get a confirmation answer:
This shows that the SIP SRV record for bytetel.com points to port 5060 at sip.onsip.com.