Domain Name System

- [Instructor] Every device that's connected to…the internet, such as a web or email server,…a VoIP phone, or other end device,…has an IP address.…Domain name system, or DNS,…maps a host name to an IP address…and works like the internet's phone book.…This enables devices to connect with one another.…Whenever you place a call to a SIP address,…the server will request the address from the DNS server.…

Once it's resolved, you can make the call.…With DNS, there are a number of…different types of resource records.…These resource records are used to specify a resource type…and an IP address to locate the resource.…Some commonly seen records are a type A record.…A type A resource record is used for…an IP version four address.…You might also see a quad A,…which is used for an IP version six address.…

A mail exchange record will redirect mail to a mail server.…And the last entry is a service record,…which defines available services…such as HTTP, LDAP, and SIP.…Similar to the way a mail exchange record…is used to send and receive mail,…