Networking Basics Questions and Answers

Answer: A

The device is a Router.

A router works at the network layer (Layer 3). It reads the destination IP address in each packet, looks it up in its routing table and forwards the packet towards the destination network, connecting separate networks together.

Bridges and switches work at the data link layer (Layer 2) using MAC addresses, and a hub works at the physical layer (Layer 1), repeating signals. Some switches add Layer 3 routing, but the device defined by Layer 3 forwarding is the router.

Answer: D

The answer is All of the above.

The standard uses of a computer network include resource sharing (printers, files, programs and data used from any machine), a powerful communication medium (e-mail, messaging, shared documents) and high reliability, since files can be copied to several machines and work can continue if one of them fails.

The paper prints 'Power communication medium' for powerful communication medium. Since all three are uses, choosing any one alone is incomplete.

Answer: D

The methods are Packet switching and Circuit switching.

In circuit switching, as in the old telephone network, a dedicated path is set up between the two ends before data flows and held for the whole call. In packet switching, as on the Internet, data is cut into packets that travel independently through the switches and share the links with other traffic.

Each alone is only half the answer, and 'line switching' is not a standard switching method.

Answer: B

The computers are connected by a cable and an interface card.

Each computer on a LAN has a network interface card (NIC), which has a unique MAC address and converts the computer's data into signals on the cable, such as an Ethernet cable plugged into the card's port.

A modem connects a computer to a telephone or cable line for wide-area access, not to a LAN. Telephone lines are a wide-area medium, and 'special wires' names no actual device.

Answer: B

Error detection at the data link layer is done with Cyclic redundancy codes.

The sender divides the frame's bits by a fixed generator polynomial and appends the remainder as the frame check sequence. The receiver repeats the division; a non-zero remainder means the frame was corrupted. Ethernet uses a 32-bit CRC this way.

Bit stuffing is used for framing, to keep the flag pattern out of the data. Hamming codes are designed to correct errors rather than just detect them, and are used mainly in memory. Equalization is a physical-layer technique for distorted signals.

Answer: B

Encryption and decryption are functions of the Presentation layer.

In the OSI model, layer 6, the presentation layer, deals with how data is represented: translation between formats, encryption and decryption, and compression.

The session layer manages dialogues and synchronisation, and the transport layer provides end-to-end delivery and flow control, so neither is the OSI home of encryption.

Answer: A

Framing is a design issue of the data link layer. This layer breaks the bit stream from the network layer into frames, adds the header and trailer, and deals with error control, flow control and access to the shared medium.

Representation of bits and synchronization of bits are physical layer matters, since the physical layer deals with how bits are encoded and timed on the medium. Connection control is the concern of upper layers such as the transport layer. So only framing belongs to the data link layer.

Answer: A

The coaxial cable of category RG-59, with an impedance of 75 ohms, is used for cable TV. It is a thin cable with a solid centre conductor, suited to carrying video signals from the antenna or a cable network to the television set.

Ethernet uses 50 ohm cables: thin Ethernet uses RG-58 and thick Ethernet uses RG-8 or RG-11. So the options that name Ethernet types are wrong because their cables are of a different impedance and category.

Answer: B

Delaying an outgoing acknowledgement so that it travels on the next outgoing data frame is called piggybacking. It saves a separate frame and so makes better use of the channel, which is the point of the technique in data link and transport protocols. Bit stuffing inserts extra bits to keep a flag pattern out of the data, pipelining sends several frames before waiting for acknowledgement, and broadcasting sends a frame to all stations, so none of these describes attaching the acknowledgement to a data frame. The keyed answer is piggy backing.

Answer: C

HTTP is a protocol of the application layer (3), TCP belongs to the transport layer (1), BGP is a routing protocol of the network layer (4) and HDLC is a data link layer protocol (2), so the code is 3 1 4 2. The other codes put TCP or HDLC in the wrong layer: the first code, for instance, places HDLC in the application layer and HTTP in the data link layer. The keyed answer is the third code.