SRV, or service, records are a new addition to the list of DNS resource records which allow a great deal of 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.
A number of machines can be specified for a given service, with differing priority and "weight" assigned, so the administrator can specify both the order in which the machines are queried and the proportion of requests each server would handle. This allows a slower machine to take a smaller amount of the traffic, maximising the efficiency of the service.
A number of programs are starting to make use of SRV records for such purposes as FTP, telnet and security applications, and they are commonly used for newer applications such as voice over IP and SIP.
Enabling SRV records for your easyDNS account
SRV records are not visable in the members page by default, so to make use of them you will first have to enable them in your account. To do this you first click the "view or edit domain and dns display options" link in the account m anagement module for your account.
On the page you are brought to look to the bottom of the list for "Show SRV Records:" You need to change this field from "no" to "yes" and then click the "done" link below the list to commit the changes.
Using SRV records with easyDNS
The above image shows the interface used to create SRV records in the easyDNS system, we will discuss each field to explain how the records need to be configured.
This is the service the record is being set up to handle, such as sip or ftp. This must be the standard designation for the service, so you will want to check the documentation on the service if you are not entirely sure what to enter.
This is the protocol the service is running on. Currently SRV records support the TCP and UDP protocols, which you can select from the drop down menu in this field. If the same service can be running on either protocol you can create SRV records for the same service pointing to the same or different machines as appropriate.
This is the name people will use to look for the service you are creating the record for, it can be the domain name itself or a specific host of that domain. If the host is to be the domain name itself, enter "@" in the host field rather than leaving it blank.
Like in an MX record, priority determines in what order the servers are queried if there is more than one SRV record for a given service. The lowest number prioroty is looked to first, so a server with a priority of 5 would be checked before a priority of 10. The higher priority numbers are checked in cases where the first server is unavailable.
Weight is a load balancing mechanism which determines the proportion of traffic the machine pointed to will handle. If 2 SRV records exist for the same service at the same priority, traffic will be directed to them in proportion to the weight. A server with a weight of 20 will receive twice the traffic as one with 10, if there is no load balancing going on it is recommended to use a weight of 0.
Port is the port number the service is run through on the machine providing it. This may or may not be a standard port designated in Assigned Numbers.
This is the host name of the machine providing the service for the domain. This name must be defined as an A record for the SRV record to function.
When you have entered all the information in the fields you need to click "next" to create the record.
If you need to create more than one SRV record at a time, you can click the in the upper right corner of the SRV records box to change the format to allow up to 4 SRV records at a time.
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