Network Topology Basics

Topology of a Network

• Topology defines the structure of a network, showcasing how components are interconnected.

• Types of Topology

  • Physical topology: Represents the physical arrangement of network devices.
  • Logical topology: Represents the flow of data within the network.

Bus Topology

• Description: All devices are connected to a single cable, called the backbone cable.

• Connection: Devices connect with drop cables to the backbone cable.

• Data Transmission: Messages are broadcasted on the backbone cable, received by all devices.

• Standards: Mainly used in 802.3 (Ethernet) and 802.4 standard networks.

• Advantages:

  • Cost-effective cabling.
  • Moderate data speeds (up to 10 Mbps).
  • Familiar technology for installation and troubleshooting.
  • Device failure does not affect other devices.

• Disadvantages:

  • Extensive cabling requirements.
  • Difficult to troubleshoot cable faults.
  • Signal interference caused by simultaneous transmissions.
  • Slows down network performance when adding new devices.
  • Attenuation (signal loss) requires repeaters to regenerate the signal.

Ring Topology

• Description: Similar to bus topology but with connected ends.

Hybrid Topology

• Description: Combines different types of topologies for data transfer.

• Example: Combining a ring topology in one part of a bank and a bus topology in another.

• Advantages:

  • Reliable: Fault in one part does not affect the entire network.
  • Scalable: Can easily expand the network size.
  • Flexible: Adaptable to various organizational needs.
  • Effective: Can maximize strengths and minimize weaknesses of different topologies.

• Disadvantages:

  • Complex network design.
  • Expensive hub requirements.
  • High infrastructure costs due to cabling and devices.

Types of Computer Networks

• Wired Networks: Use physical connections (cables) to connect devices.
• Wireless Networks: Use radio waves for communication between devices without cables.

The Internet

• Origins:

  • ARPANET (Advanced Research Projects Agency Network) was initially designed to provide a communication network that could survive a nuclear attack.
  • The first public launch of the World Wide Web occurred on August 6, 1991.

• Client and Server Interaction:

  • Clients (user devices) connect to the internet through an Internet Service Provider (ISP).
  • When a client requests a webpage, it connects to the server hosting the webpage.

• Packet Transmission:

  • Information is broken into packets for efficient transmission.
  • Each packet contains an address to guide it to the receiving device.
  • Routers, part of the Packet Routing Network, handle packet forwarding based on addresses.

• Transfer Control Protocol (TCP):

  • Responsible for ensuring reliable delivery of packets.
  • Packets are reassembled at the receiver in the correct order.

• Steps in Message Transmission:

  • Computer 1 sends a message to Computer 2.
  • The message is split into packets.
  • TCP ensures packet delivery and quality.
  • Packets reach Computer 2 and are reassembled.

Father of the Internet: Tim Berners-Lee

• Key Roles: Developed the World Wide Web, HTTP, HTML, and URLs.
• Background : Graduated with a Physics degree from Oxford University in 1976.
• Current Role: Director of the World Wide Web Consortium (W3C).

Network Layers

Data Link Layer

• Responsibilities: Packet routing and forwarding.

Network Layer

• Devices: Routers (layer 3 devices) provide routing services.

• Protocols: Network layer protocols, such as IP and IPv6, handle network traffic routing.

• Functions:

  • Internetworking: Establishing logical connections between devices.
  • Addressing: Assigning source and destination addresses to packets.
  • Routing: Determining the optimal path for data flow.
  • Packetizing: Converting data into packets.

Transport Layer

• Responsibilities:

  • Ensuring message order and preventing duplication of data.
  • Reliable transfer of data.

• Segmenting: Receives data from upper layers and divides it into segments.

• End-to-End Connection: Provides a point-to-point connection between communicating devices.

• Protocols:

  • Transmission Control Protocol (TCP): Reliable connection-oriented protocol for transferring data over the internet.

    • Establishes and maintains connections, divides data into segments, and reorders received packets.

  • User Datagram Protocol (UDP): Unreliable connectionless protocol.

    • It does not require acknowledgements from the receiver, and data delivery is not guaranteed.

• Port Numbers:

  • Each process on a node has a unique port number for identification.
  • Ports are similar to extensions of IP addresses.

• Specific Addresses:

  • User-friendly addresses exist for specific applications, such as email addresses and URLs.

Transmission Media

• Guided Media: Physical media used for signal transmission.

• Twisted Pair: A pair of insulated copper wires twisted together to reduce noise interference.

  • Types:
    • Unshielded Twisted Pair (UTP): Widely used in telecommunications.
    • Shielded Twisted Pair (STP): Contains a mesh surrounding the wires for higher transmission rates.

• Advantages of Twisted Pair:

  • Cost-effective.
  • Easy to install.
  • Suitable for high-speed LANs.

• Disadvantages of Twisted Pair:

  • Limited distance due to signal attenuation.