🪴 TJ's Notes 1.0

Computer Networks Lecture 5

4 min read

Computer Networks Lecture 5

Index

Main Topics

DXD and RXD

  • DXD (Data Exchange Driver): Typically refers to components responsible for handling data exchange between devices or systems, such as USB communications and serial ports.
  • RXD (Receive Data): The line used to receive data in serial communication, part of the RS-232 standard, working alongside the TXD (Transmit Data) line.

Media Cable

  • Media Cable: The physical medium used for data transfer between devices. Examples include:
    • Twisted Pair Cable: Commonly used in Ethernet networks (e.g., Cat5, Cat5e, Cat6).
    • Coaxial Cable: Used in older Ethernet networks and for cable internet.
    • Fiber Optic Cable: Uses light to transmit data, enabling high-speed transfers over long distances.

Ethernet

  • Ethernet: A set of networking technologies used in local area networks (LANs), defined by the IEEE 802.3 standard.

    • Operates at the Data Link Layer (Layer 2) of the OSI model.

    • Utilizes MAC addresses for hardware identification.

      RJ45

  • RJ45 (Registered Jack 45): A standardized network interface for connecting Ethernet cables.
    • Diagram of 8 Pins:
      • Pin 1: Transmit Data+ (TD+)
      • Pin 2: Transmit Data- (TD-)
      • Pin 3: Receive Data+ (RD+)
      • Pin 4: Unused (often used for Power over Ethernet)
      • Pin 5: Unused (often used for Power over Ethernet)
      • Pin 6: Receive Data- (RD-)
      • Pin 7: Unused
      • Pin 8: Unused

HUBS and Switches

  • HUBS:

    • Operate at the Physical Layer (Layer 1) of the OSI model.
    • Broadcast data to all ports, leading to potential collisions.
    • Limitations: Limited by the number of ports (typically 4 to 24).

  • Switches:

    • Operate at the Data Link Layer (Layer 2) of the OSI model.
    • Use MAC addresses to forward data only to the intended recipient, reducing collisions and enhancing network performance.
    • Advantages: Support more devices and provide better performance compared to hubs.

How to Get More than Hub Count

  • Daisy Chain Hubs: Connect multiple hubs in series, though this can lead to increased network collisions and degraded performance.
  • Use Switches: Replace hubs with switches to connect more devices and improve network performance.

Cable, Node, Switch, Hub

  • Cable: The physical medium connecting devices in a network.
  • Node: Any device connected to a network, such as computers, printers, or network storage.
  • Switch: Connects multiple nodes and uses MAC addresses to forward data to the correct destination.
  • Hub: A basic networking device connecting multiple nodes but broadcasting all data to all ports.

Why Layering is Required in Networking

  1. Functions Preferred at a Lower Layer May Be Ignored by a Higher Layer:

    • Allows abstraction and modularity in network design, with each layer functioning independently. Example: TCP handles reliable delivery, while IP handles routing.

  2. Easy to Implement Networking Stack:

    • Simplifies the development and troubleshooting of network protocols by allowing developers to focus on specific layers.

  3. Technologies Independence Can Be Maintained:

    • Ensures interoperability between different hardware and software, and allows integration of new technologies without changing the entire network stack. Example: Different physical media (Ethernet, Wi-Fi) can be used without altering higher layers.

Homework

  • Check TCP/IP Implementation in sys32:
    • Locate the TCP/IP implementation files in Windows (usually C:\Windows\System32).
    • Examine files like tcpip.sys to understand TCP/IP stack implementation in Windows.

References

  1. Windows Internals 7th Edition by Mark Russinovich, Microsoft Press
  2. Linux Network Internals

Commands and Examples

  • Checking TCP/IP Configuration in Windows:

    ipconfig /all
netstat -an

  • Viewing TCP/IP Implementation Files in Windows:

    dir C:\Windows\System32\drivers\tcpip.sys

  • Analyzing Network Interfaces in Linux:

    ifconfig -a
ip addr show

  • Monitoring Network Connections in Linux:

    netstat -tuln

These commands offer insights into network configurations and active connections on both Windows and Linux systems. The homework involves exploring the TCP/IP stack to understand its implementation and functionality.

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