[aen1]

Sadly enough, I've been ask the UDP/TCP question many times, so I have a good answer, though I have never studied either in depth. So, in theory that would be a great question. But, it is asked too often to really be of any use.

[xxqs]

actually a great interview question is what happens when you click a link in the browser. All the steps down to how deep you understand it: through the kernel calls, DNS packets, ARP, Ethernet frames, IP routing, TCP acknowledgements, HTTP headers, MIME types, and so on.

[aen1]

How is that good? It's all memorization

[xxqs]

nope, this is all about understanding the logic and how the system components interact with each other.

Besides, you can dig deeper in any direction, depending on the candidate profile. For a network engineer, understanding on the packet level is important. For a web programmer, the interaction between server and client is important (HTTP headers, MIME types etc, webserver scalability etc.). For a sysadmin, understanding of processes and interaction of applications and OS is important. All those can be derived just from a simple question -- what happens when you click on a link

[tomblomfield]

I agree - you can memorise answers on a fairly generic level, but digging deeper in a relevant area, or talking about edge cases, exposes whether a person really understands what's going on.

[xxqs]

besides, how can one memorize if the questions are unknown?