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SRV Record
Unlike most other DNS records that specify a server or an IP address, a DNS SRV record specifies both a host and a port for a specific service like voice over IP (VoiP), instant messaging, and other services.
What are SRV Records Used For?
SRV records are mainly used to help with service discovery. In simple terms, they’re used to establish connections between a server and a host name. So, when an application needs to find a service it will search for the SRV record.
When it finds the SRV record it will go through the list of services and their hostnames to find:
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The hostname.
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Ports.
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Priority and weight.
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IP address, if necessary.
Ports are virtual places that determine what processes network traffic goes to within a computer. This makes it easier for the computer to differentiate between different types of traffic. For example, VoiP traffic will go to one port, while email messages will go to another. Similar to IP addresses, ports are assigned a number and certain services, like IMAP, SMTP, and POP3 need to connect to specific ports in addition to connecting to a specific server.
Ports are virtual places that determine what processes network traffic goes to within a computer. This makes it easier for the computer to differentiate between different types of traffic. For example, VoiP traffic will go to one port, while email messages will go to another. Similar to IP addresses, ports are assigned a number and certain services, like IMAP, SMTP, and POP3 need to connect to specific ports in addition to connecting to a specific server.
The difference between weight and priority is that priority will be looked at first. So, if there are three servers with different priority values, the service will always query the server with the lowest priority value first, irrespective of what their weight values are.
When their priority value is set to the same value, weight will come into play and the service will query the server with the highest weight value first.
Why are SRV Records Important?
Because SRV records identify which computers host specific services, it's important that they are configured correctly. If they're not, services might use the wrong ports and preferences, for example, a new email client that will then use the wrong ports in its configuration. This means creating an SRV record saves time later on when services need to be configured.
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