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Comparing Traditional Networks and SDN

May 15, 2025

Lecture Notes: Traditional Network Architecture vs. Software-Defined Networking (SDN)

Introduction

  • Discussion about traditional network architecture compared to software-defined architecture.
  • SDN is a buzzword, used differently by various vendors.

Traditional Network Architecture

  • Path Selection Decisions

    • Made by network devices (e.g., load balancers, routers, switches).
    • Dependent on communication between routers and switches via protocols (e.g., OSPF, BGP, RSVP, LLDP).
    • Communication is isolated within the network segment.
  • Application and Network Communication

    • No direct communication between the network and the application.
    • Load balancers communicate with applications, but invisibly to the network.
    • No impact or visibility between applications and the network regarding service uptime.

Software-Defined Networking (SDN)

  • Path Selection Decisions

    • Made by applications with complete network visibility.
  • Role of Load Balancers

    • Optional in SDN architecture.
    • In pure SDN, load balancers might not be necessary.
  • SDN Controller

    • Applications communicate with a network controller.
    • The controller communicates with the network to adapt to application needs.
    • Separation of control plane and data plane.
    • BGP is a standard protocol supporting this separation (unlike OSPF).
  • Functionality of SDN Controllers

    • Monitor both application and network status.
    • Keep a pulse on application status and load balance if needed.
    • Program the network based on application needs without programming the application itself.

SD-WAN and SDN

  • SD-WAN as an Example

    • Applicable to remote or branch networks.
    • Controller oversees WAN behavior.
    • Large enterprises with many branches benefit from SD-WAN intelligence.
  • Comparison with Pure SDN

    • SD-WAN controller as a type of SDN controller.
    • Pure SDN controllers typically manage LAN or data center networks.

Conclusion

  • Fundamental architectural change from traditional networks.
  • Next steps include lab demonstrations on SDN controllers.
  • Future video will illustrate practical application and network programming with SDN.