Introduction to Computer Science and Engineering
Explainer
DNS: the internet's phonebook
Computers can't find umat.edu.gh by name. They need a number first.
Quick check · tap an answer to continue
Lesson notes
Key points
- Every device on the internet is reached by an IP address, a numeric label like 192.0.2.10.
- The Domain Name System, or DNS, translates human-friendly domain names into those IP addresses.
- Your resolver asks a root server, then the top-level domain server for .gh, then the domain's authoritative server.
- Answers are cached for a set time called TTL, so repeat lookups are fast and servers aren't overloaded.
Definitions
- IP address
- A numeric label that identifies a device's network interface so packets can be routed to it
- TTL
- Time To Live: how long a DNS answer may be cached before it must be looked up again
Takeaway: DNS turns names into IP addresses through a cached, layered lookup.
Quick check: Which server holds the final record for a domain?
- Root server
- Authoritative server
- TLD server
IP addressDNSResolution chainCaching & TTL
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