ITPEC IP April 2020 Question 30

It connects an IP address and a domain name — DNS (Domain Name System) is the Internet's name-resolution service.

People use names such as www.example.com, but packets are delivered by IP address. When a PC needs to reach a host by name, it asks a DNS server, which answers with the matching IP address (name resolution); the PC then connects to that address. DNS servers are organised in a hierarchy, each responsible for its own part of the domain name space.

Answer (b)

Why not others:

• •(a) — finding the MAC address that belongs to an IP address is ARP (Address Resolution Protocol), used inside a LAN to address a frame to the right device
• •(c) — choosing the route a packet takes from its destination IP address is routing, the job of a router
• •(d) — converting between analog and digital signals is the job of a modem

Key rule: Each kind of address has its own mechanism: DNS turns names into IP addresses, ARP turns IP addresses into MAC addresses on the local network, DHCP assigns IP addresses, and routers forward packets by IP address.

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