UDP — end of module

What this checks. That you can say precisely what UDP leaves out, and resist the summary that it is simply 'faster'. You need 3 of 4 to pass, and every option is explained afterwards — including the ones you did not pick.

1. 1/4A UDP datagram's Length field reads 22. How many bytes of application payload does it carry?

   Work out a value

   14

   22

   30
2. 2/4Someone says 'UDP is faster than TCP'. What is wrong with that as stated?

   Say why an answer is wrong

   Both put bytes on the same wire at the same speed; what UDP removes is waiting — for a handshake, for acknowledgements, for lost data to be re-sent

   Nothing — UDP has a smaller header, so it is faster

   UDP is actually slower because it has no windowing
3. 3/4What is the status of the UDP checksum?

   Tell two ideas apart

   Optional over IPv4 — a zero means 'not computed' — and mandatory over IPv6

   Mandatory everywhere, like TCP's

   Optional everywhere
4. 4/4A team is designing a protocol that sends one small request and expects one small response, with the client free to retry. Which transport fits, and why?

   Apply it somewhere new

   UDP — a connection setup would cost more round trips than the exchange itself, and the retry logic is one line

   TCP — reliability is always worth the cost

   Either — the choice makes no observable difference at this size