SRV record

What is an SRV record?

In the Domain Name System, a service record (SRV record) specifies servers by hostname and port number. Without needing to know the actual addresses of the servers, it is possible to make a server discoverable and designate high-priority and high-availability servers using a single domain and an SRV record. An SRV record can possibly save you time in the future.

Understand the purpose of an SRV record

The DNS server's zone configuration file is where SRV records are entered. They provide the hostname and port of the machine providing the service, together with the symbolic service name, protocol name, domain name, time to live, class, priority, and relative weight compared to other records.

Without having to know a server's precise address, SRV records are used to make services available on a network, such as SIP for VoIP telephony. Administrators can use many servers for a single domain by using the weight and priority features, with additional servers being available in the event that the main server fails.

The purpose of SRV records is to generate data for various services that are frequently found on systems and commonly linked to SIP Configurations. SRV Records uses a special method for generating names. In simple terms, it begins with an underscore, then includes the service name, a period, another underscore, the system protocol, one more dot, and finally the domain name.

What goes in an SRV record?

The following elements are part of the SRV record service:

Service: The desired service's symbolic name.
Protocol: The desired service's transport protocol; in most cases, this is either TCP or UDP.
Name: The domain name, with a dot at the end, for which this record is active.
TTL: The default DNS time-to-live field.

What is the difference between priority and weight in SRV records?

The "weight" and "priority" of each server listed in an SRV record are always indicated. Administrators can give one server supporting a certain service priority over another by changing the "priority" value in an SRV record. A server with a lower priority value will experience more traffic than other servers. The "weight" value is similar, though; a server with a higher weight will get more traffic than servers with a lower weight.

The main difference between the two is that priority is considered first. If there are three servers, Servers A, B, and C, and each has a priority of 10, 20, and 30, then their "weight" is irrelevant. The service will always check Server A first.