N&SA-2025-S1-Wk3-1

Domain Name System (DNS)

Purpose of DNS

• The primary function of DNS is to translate domain names into IP addresses.

Historical Context: ARPANET

• ARPANET, the precursor to the internet, facilitated resource sharing among colleagues.
• Early network management was simple due to the small scale of the network.
• DNS was initially managed manually using a host file that mapped names to IP addresses.

Host File Characteristics

• Easy to implement and understand.
• Simple text file format ensured a unified understanding.
• Manual updates managed centrally by the SAI Network Information Systems Information Centre at Stanford Research Institute.
• Updates distributed via electronic mail initially, then via FTP for downloading the latest version.

Challenges with Host Files

• As the network expanded, managing DNS via a host file became increasingly difficult.
• Updating the host file was time-consuming.
• The size and complexity of the host file grew substantially, making it hard to manage.

Solution: Domain Name System (DNS)

• An investigation was initiated to replace the host file system with a more scalable solution.
• Goals included a consistent naming structure and a generic solution applicable for multiple purposes.
• Paul Mockapetris from USC Information Sciences Institute designed the architecture of DNS.
• Details can be found in RFCs (Request for Comments) 882 and 883.
• Transition plan released in November 1983, with completion targeted for early 1984.

DNS Infrastructure: Namespace

• The DNS database structure is an inverted tree of nodes.
• The root of the tree is at the top, with branches extending downwards.
• Each node has a label; the root node is labeled with a dot and has no name.
• The hierarchy includes top-level domains (TLD), second-level domains, and potentially third-level domains.

Domains

• A domain comprises a node in the namespace and all its descendants, forming a subtree.
• A domain's name corresponds to the name of the node at the root of its subtree.
• Examples of top-level domains: .com, .edu, .gov.