Скачать или смотреть Application layer (2/5): The domain name system (DNS) (Computer networks)

The domain name system (DNS) is a set of protocols and zone files that forms a distributed database. This system is used to resolve names of servers to their addresses, that are used by the lower layers of the protocol stack to route messages between their origins and destinations.

The DNS exemplifies two of the core design principles of the Internet: local autonomy and fault tolerance via redundancy.

The video introduces the DNS as a set of nodes that are arranged hierarchically. The NS entries at each node of the twee point to nameservers that enable one to query the subdomains of any given domain. The operation of the toot nameservers as the starting point of this hierarchy is explained.

The video illustrates how to use tools, such as nslookup and whois to navigate the DNS tree in a practical context. The operation of iterative name resolution is demonstrated in some detail; where appropriate, recursive name resolution is illustrated. It is hoped that viewers will get their hands dirty by following the path from the toot namerservers to a given domain using iterative techniques. Viewers are also encouraged to explore the SOA entries of various networks and consider the logic that underlies the selection of specific SOA values.

A small example zone file in bind notation is explored. While not expressly covered in the video, it is hoped that some viewers will create a zone file, install bind, and get it to a stage where it can be queried.

It is hoped that the variety of DNS issues that are introduced will provide the viewer with a reasonably detailed understanding of the design, operation, and principles of the DNS.

The video is part of a lecture series made at home to continue online education during COVID-19 lockdown.