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Understanding Layer 2, 3, and 4 protocols

This chapter excerpt explains the layers of the OSI model, switching, TCP, UDP, and VRRP.

Optimizing Network Performance with Content Switching

Chapter 2: Understanding Layer 2, 3, and 4 Protocols

This book excerpt is from Chapter 2 of "Optimizing Network Performance with Content Switching: Server, Firewall...

and Cache Load Balancing" by Matthew Syme/Philip Goldie, Addison-Wesley Professional, copyright 2004, ISBN 0131014684. This book will publish in July, 2003. All rights reserved. This chapter is posted with permission from Addison-Wesley Professional.

This chapter includes the following sections:

The OSI seven-layer model – What is a layer?

  • The Application Layer (Layer 7)
  • The Presentation Layer (Layer 6)
  • The Session Layer (Layer 5)
  • The Transport Layer (Layer 4)
  • The Network Layer (Layer 3)
  • The Data Link Layer (Layer 2)
  • The Physical Layer (Layer 1)
  • Putting all the layers together

Switching at the different layers

  • Layer 2 switching
  • Layer 3 switching and routing

Understanding Layer 4 protocols
Transport Control Protocol (TCP)

  • The lifecycle of a TCP session
    1. Initiating a session
    2. Data transfer
    3. Terminating a session

User Datagram Protocol (UDP)

  • A simple UDP data flow
    • The request
    • The response

Virtual Router Redundancy Protocol (VRRP)

  • Layer 2 and 3 redundancy
  • The components of VRRP
  • VRRP addressing
  • VRRP operation


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