A set of rules that define how data is formatted, transmitted, and received over a network. Protocols specify message formats, sequencing, error handling, and authentication so that devices from different manufacturers can communicate reliably.
Protocols are like the rules of a language — both sides must agree on how to communicate, or the message is meaningless.
Showing a random 20 of 50 problems.
Example 1
challenge
Why does HTTPS still leak the destination hostname (e.g., bank.com) to a network observer even though the page content is encrypted?
Example 2
easy
Trace one HTTPS web request: name the protocols involved at each step (name lookup, transport, security, application).
Example 3
medium
Match: 'transfers files between hosts' vs 'transfers web pages'. Which is FTP and which is HTTP?
Example 4
medium
Why must HTTP rely on a lower-level protocol like TCP?
Example 5
hard
HTTP/3 replaces TCP+TLS with QUIC over UDP. Name one concrete benefit of this redesign.
Example 6
medium
A page loads but DNS lookup is timing out for some assets. Which layer is failing — name resolution or transport?
Example 7
easy
A network protocol is best defined as a set of ___ for how devices communicate.
Example 8
easy
Which protocol is used to load web pages in a browser?
Example 9
challenge
Design question: a new app needs to stream live sensor data with very low latency but tolerates occasional dropped samples. Which transport protocol should it use, and why?
Example 10
medium
You visit https://example.com. Trace which protocol takes each step: (1) name lookup, (2) reliable connection, (3) encryption, (4) page request.
Example 11
medium
Which protocol assigns an IP address to a device when it joins a local network?
Example 12
hard
Why can the same HTTP protocol work over Wi-Fi, cellular, and fiber without changes?
Example 13
medium
Which protocol does each use: (a) sending email, (b) transferring files, (c) loading a web page?
Example 14
hard
You can ping a server (ICMP works) but HTTPS to it hangs. Which higher-layer step is most likely failing — TCP handshake or TLS handshake or DNS?
Example 15
medium
Which transport-layer protocol drops reliability for low latency and is preferred for live video and gaming?
Example 16
medium
You type a domain name and a web page loads. Which two protocols (one for name lookup, one for the page) are involved?A page load uses two protocols: DNS for name lookup, HTTP for the page transfer
Example 17
medium
Match the job to the protocol: 'reliable in-order bytes' vs 'route packets by address'. Which is TCP and which is IP?TCP handles reliable in-order delivery; IP handles routing hop by hop
Example 18
medium
A new app from vendor A talks to a server from vendor B with no shared protocol. What is the predictable result?
Example 19
challenge
Explain why layering protocols (HTTP over TCP over IP) is better than one giant all-in-one protocol.
Example 20
medium
A laptop and a printer from different brands can print over Wi-Fi only if they share what?