Computer Networks Overview Quiz

Computer Networking

• A computer network connects two or more devices to exchange information and share resources. Connections can use copper wire, telephone lines, lasers, radio waves, satellites, or infrared light beams.

Lecture Outline

• What is a computer network?
• Objectives of networks
• Uses of computer networks
• Network types: LAN, MAN, WAN
• Network topology
• Casting
• Transmission modes

Objectives of Networks

• Sharing resources (databases, CPUs)
• Interprocess communication (between users and processors)
• Interactive sessions between geographically separated users
• High reliability through alternative sources of supply (if one processor fails, another can take over, etc.). If one link fails, another route can be used.
• Distributing processing functions (e.g., one node translates, another processes and formats data).
• Centralized control for geographically distributed systems (e.g., inventory management, handling accounts in finance).

Uses of Computer Networks

• Software firms can provide access to their programs over a network (important if program is large, machine-dependent, or embedded in libraries).
• Networks provide equal access to services, regardless of geographic location.
• Networks allow for national or international access to services, such as universities and telemedicine.
• E-commerce (online shopping, ordering, etc.).
• Access to financial institutions (online banking, bill pay, investment management).
• Personalized online newspapers (picking specific topics, storing articles locally).
• Online libraries for journals, books, and conference proceedings.
• Electronic mail (email).
• Videoconferencing for communication across distances (shared virtual blackboards).

Network Types: LAN – MAN – WAN

LAN (Local Area Network)

• Connects devices within a limited geographical area (e.g., home, school, office).
• No central computer needed; each computer plays a similar role.
• Can span up to 1 km in radius.
• Uses devices like routers, switches, hubs, repeaters, and bridges.
• High-bandwidth media and multi-access are used.
• Enables communication, file transfer, etc.
• Can connect to other LANs or WANs.

MAN (Metropolitan Area Network)

• Connects two or more LANs in a geographic area like a city or group of buildings.
• Can span from 5 to 50 kilometers.
• Not usually owned by a single organization, but associations of users or a single network provider.
• Users share resources in a larger area compared to LAN.

WAN (Wide Area Network)

• connects larger geographical areas (states, countries, continents).
• Often used to span long distances, and the internet is a WAN.
• Ownership and management is distributed over several locations.
• Uses routers, communication servers, and modems.
• Allows full-time and part-time connectivity over different interfaces.
• Provides access to computers or file servers outside the network's immediate area.

Network Topology

• Network configuration; how devices connect to each other in a network.
• Three main goals of a network topology:
  • Maximum reliability
  • Least cost path routing for network traffic.
  • Best possible response time and throughput for users.

Bus Topology

• Each device connects directly to a common cable.
• One machine acts as the master at a time for transmission.
• Conflicts may arise if two machines transmit simultaneously.
• Troubleshooting can be difficult if one device fails because the entire network can shut down.

Ring Topology

• Devices are connected in a circular pattern.
• Packets travel until they reach their destination.
• Easily modified by adding or removing devices.
• Bandwidth must be shared amongst all devices.
• Entire network may go down if a single node fails.

Star Topology

• Each device has dedicated wires connecting to the central hub.
• Hub is the central point of all traffic.
• Enables network troubleshooting, and gathers network statistics from the central point.
• Network failure may occur if the central hub fails.
• Costly to cable as all cable runs must be connected to a single hub or central point.

Mesh Topology

• Two types: full mesh (every device connects to every other device) and partial mesh (only connections exist to other devices it commonly interacts with).
• Used in hybrid topologies.
• Example is the Tree topology combining a bus and a mesh topology.

Casting

• Data transmission from a source to a destination.
• Three types:
  • Unicast (one-to-one): data to a single recipient
  • Broadcast (one-to-all): data to all devices in a network.
  • Multicast (one-to-many): data to a specific group of subscribers.

Transmission Modes

Simplex

• One-way communication.
• Information is sent from one device to another but the receiver cannot send back information. (e.g., TV, Radio Broadcast.)

Half-Duplex

• Two-way but only one device can send at a time (e.g., walkie-talkie).
• Devices take turns transmitting.

Full-Duplex

• Two-way communication where both devices can send and receive simultaneously. (e.g., phone call, video conferencing).