Computer Networks Previous Year Questions

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PCI (Peripheral Component Interconnect) is a high-bandwidth, processor-independent bus that can work as a mezzanine or peripheral bus.

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With multiple threads the browser can download and render several small images at the same time instead of one after another, which speeds up loading.

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In a multimode step-index fiber, the core has the same density (refractive index) everywhere, with a sudden step at the cladding. In graded-index fiber the density changes gradually.

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HTTP (HyperText Transfer Protocol) is used to access web pages on the World Wide Web. SMTP is for email, and SLIP is a serial-line link protocol.

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Web pages are written in HTML (HyperText Markup Language). HTTP is the protocol that transfers them.

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In handshaking, the sender signals that data is ready and the receiver replies with an acknowledgement signal. Strobe control uses only one control signal.

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DNS (Domain Name System) translates domain names such as example.com into IP addresses.

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Eavesdropping is secretly intercepting or listening to private communication in real time over a network without permission.

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ARP maps a known IP address to the matching MAC (hardware) address on a local network. RARP does the reverse.

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With full-duplex lines and no self-connection, each pair of lines needs one crosspoint. So the count is n(n−1)/2 = 10 × 9 / 2 = 45.

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X.21 is an ITU-T standard interface for connecting stations (DTE) to circuit-switched digital networks.

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In a star topology every device has its own point-to-point link to a central hub or controller. In a mesh, every device links directly to every other device.

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The OSI model has 7 layers: Physical, Data Link, Network, Transport, Session, Presentation and Application.

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Bit synchronization is done by the Physical layer, not the Data Link layer. Data Link handles framing, error control and flow control. The other pairs are correct.

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Each character needs 1 start + 7 data + 1 parity + 1 stop = 10 bits. So 19,200 bps ÷ 10 = 1920 characters per second.

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SSL encrypts data and is traditionally placed at the Presentation layer in OSI terms, because encryption and decryption are presentation-layer jobs. It sits between the application and transport layers.

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10Base5 is the original Thick Ethernet (thicknet): 10 Mbps, baseband, 500 m segments on thick coaxial cable. 10Base2 is Thin Ethernet.

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Optical fibre carries light signals. This gives very high bandwidth and long distances, and it is immune to electromagnetic interference, but it is expensive.

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ARPANET stands for Advanced Research Projects Agency Network. It was the US Department of Defense network that led to the Internet.

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Bandwidth is the transmission capacity of a channel, meaning how much data it can carry per unit time, measured in bps or Hz.

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An internal computer bus moves data in parallel over very short distances, so it gives a far higher data rate than telephone lines, modems or leased lines.

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The upper four OSI layers (Transport, Session, Presentation, Application) are host-to-host (end-to-end) layers. The lower layers handle hop-by-hop delivery over the network.

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A bridge filters and forwards frames using MAC addresses, so it works at the data link layer (layer 2).

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In a mesh topology each device has dedicated links to the others, so a single link failure does not affect the network. This gives the highest reliability.

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An IPv4 address is 32 bits = 4 bytes, usually written as four dotted decimal octets.

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A multiplexer selects one of several inputs and sends it over a single output line, so many data sources can share one transmission line.

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A consumer first does wait(F) to make sure a full slot exists, then wait(M) for mutual exclusion on the buffer, and only then removes the item.

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The relational, hierarchical and network models are record-based logical models. The E-R model is an object-based conceptual model.

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In optical fibre, light stays inside the glass core by total internal reflection at the core-cladding boundary.

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Optical fibre gives high bandwidth over long distances with little loss and no electromagnetic interference, so it is best for linking offices in different cities.

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Total bandwidth = 10 channels × 3000 Hz + 9 guard bands × 300 Hz = 30,000 + 2,700 = 32,700 Hz. Ten channels need only nine guard bands between them.

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A modem (modulator-demodulator) converts digital data into analog signals for transmission over telephone lines and converts them back at the receiver. Switches, hubs and repeaters handle signals that stay digital.

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Pulse code modulation samples, quantises and encodes a signal into binary pulses, giving a digital signal. AM, FM and ASK modulate an analog carrier.

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A Wide Area Network covers large geographical areas such as cities or countries. A LAN covers a single building or campus.

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In a slotted ring, a station may transmit only when it holds an empty slot or token circulating on the ring. CSMA/CD is a contention (random access) protocol.

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Baud rate = 1000 signal units per second. Bit rate = baud × bits per unit = 1000 × 4 = 4000 bps.

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SMTP (Simple Mail Transfer Protocol) transfers e-mail between mail servers. HTTP is for web pages, FTP for files and SNMP for network management.

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Objects communicate by message passing, that is, one object calls another object's methods.

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Common topologies are bus, star, ring, mesh, tree and hybrid. "Singleton network" is not a topology.

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The session layer establishes, maintains and terminates sessions. Setting up the logical path (routing) between source and destination is the network layer's job, not the data link layer's.

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Circuit switching sets up a dedicated path before transfer, and packet switching breaks the data into packets that are routed independently. Both are true.

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A honeypot is a decoy system set up to lure attackers so their methods can be observed and studied.

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Database models include hierarchical, network, relational and object-oriented. There is no "inheritance model".

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LANs, mobile networks and the Internet are distributed systems of separate networked computers. Parallel computing usually uses processors sharing memory in one machine, so it is counted as different.

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An axon is the long cylindrical fibre that carries impulses away from a neuron to other neurons.

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Flooding sends every incoming packet out on every outgoing line except the one it arrived on.

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Satellite-to-earth transmission uses the downlink frequency, and earth-to-satellite uses the uplink frequency.

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Non-adaptive (static) routing algorithms decide routes in advance and ignore current traffic and topology. Adaptive algorithms react to them.

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XMODEM is a simple file-transfer protocol for uploading and downloading files between computers over modems. It sends data in 128-byte blocks with a checksum.