Computer Network Questions and Answers

Answer: A

Correct answer: 5-7

In a network user address the first four digits are the DNIC, digits 5 to 7 the area, and 8 to 12 the terminal.

Answer: C

Correct answer: 8-12

Digits 8 to 12 identify the terminal, following the four-digit DNIC and the three-digit area code.

Answer: C

Correct answer: 15

With n bits for sequence numbers a go-back-N window may be at most \( 2^{n}-1 \), one less than the number of distinct sequence numbers, so that a full window can never be mistaken for an empty one:

\[ 2^{4}-1 = 15 \]

Answer: A

Correct answer: Hot potato routing

Hot potato routing sends each packet out on whichever queue is shortest, getting rid of it as fast as possible without regard to where it is going. Flooding sends copies everywhere, and static routing consults a fixed table.

Answer: C

Correct answer: UUCP

UUCP - Unix to Unix Copy - copies files between machines over a single link, and was the basis of early mail and news distribution. TFTP is a trivial transfer protocol and UART is a hardware device.

Answer: D

Correct answer: 11010100

The 2’s complement is formed by inverting every bit and adding 1. Starting from 00101100, inversion gives 11010011, and adding 1 gives 11010100. Note that 11010011 - the second option - is the 1’s complement, which is the classic trap. A quicker method for hand working: copy the bits from the right up to and including the first 1, then invert everything to the left of it. Here the rightmost 1 is in the third position, so 100 is copied and 00101 becomes 11010, giving the same answer. 2’s complement is the standard representation for signed integers because it makes subtraction identical to addition - the processor needs no separate subtractor - and because it has only one representation of zero, unlike 1’s complement and sign-magnitude, which have two. In eight bits it represents the range −128 to +127, the asymmetry arising from that single zero.

Answer: C

Correct answer: both (a) and (b)

Slotted ALOHA divides time into slots equal to one frame time and allows transmission only at a slot boundary, which halves the vulnerable period and doubles the throughput. Both properties follow from the same requirement: every station must agree on where the slots begin, which needs global synchronisation.

Answer: C

Correct answer: synchronization

In asynchronous serial transmission the receiver has no clock from the sender, so each character is framed by a start bit that marks its beginning and a stop bit that returns the line to idle. They carry no data and exist only to keep the receiver in step.

Answer: C

Correct answer: Carrier sense systems

Carrier sense schemes can be run either way: as plain contention, in which every station has equal standing, or with priority, in which higher-priority stations wait a shorter interval before transmitting and so win the medium. TDM and register insertion allocate access by position rather than by priority.

Answer: B

Correct answer: 45

A full-duplex line serves both directions, and no station connects to itself, so the number of connections is the number of unordered pairs:

\[ \binom{10}{2} = \frac{10\times 9}{2} = 45 \]