Introduction to Network Security Concepts

Sep 30, 2024

Network Security Lecture Notes

Introduction to Network Security

  • New chapter focusing on Network Security.
  • Assumes prior knowledge of Computer Networks.
  • Overview of key concepts related to network protocols will be provided as needed.
  • Topics to cover:
    • Definition of network security.
    • Vulnerabilities in networks.
    • Network attacks.
    • Defense mechanisms.

Understanding the Internet

  • The term Internet can be divided into two parts: inter (interconnect) and net (networks).
  • Heterogeneous Networks: Different types of networks (e.g., Ethernet, fiber optics, wireless).
  • Communication between endpoints (nodes A and B) can be complex:
    • Error control.
    • Reliability.
    • Media sharing.

Internet Protocol Stack

  • Layers: Modular design for ease of implementation and fault tolerance.
  • Five Layers (not seven, as session and presentation layers are not commonly used):
    1. Physical Layer: Enables bit transmission on media.
    2. Link Layer: Allows communication between neighboring nodes.
    3. Network Layer: Manages end-to-end routing of messages.
    4. Transport Layer: Handles process-to-process communication.
    5. Application Layer: Specific to user applications (e.g., email, web browsing).

Core Networking Concepts

  • Protocols: Agreements on communication formats and rules (e.g., ARP, OSPF, TCP).
  • Service Interface: Communicates requests for functionality between layers.
  • Peer Interface: Interactions between peer layers on different machines.

Encapsulation and Decapsulation

  • Each layer adds a header for communication with peers.
  • Encapsulation: Adding headers as data passes down the protocol stack.
  • Decapsulation: Removing headers as data moves up the protocol stack.
  • Example: An IP header used for routing between routers.

Multiplexing and Demultiplexing

  • Multiplexing: Process of deciding which higher layer protocol a packet should be sent to.
  • Demultiplexing: Distributing incoming packets to the correct higher layer protocol based on header fields (e.g., port numbers).

Network Interactions

  • Example of communication through various networks (e.g., Ethernet, Token Ring).
  • Packet Switching: Sharing resources across the network.
    • Contrast with Circuit Switching (dedicated resources).
    • Store and Forward: Buffers packets due to shared links, can lead to buffer overflow and packet loss.

Internet Characteristics

  • Best Effort Service: Datagram model with no connection setup.
    • Internet does its best to deliver packets but with no guarantees (loss, corruption, reordering possible).
  • Principle of keeping it simple allows interconnection of heterogeneous networks using a common protocol (IP).

Conclusion

  • Overview of core concepts in networking concluded.
  • Essential knowledge for understanding network security and defense mechanisms.