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.

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.

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 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.

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.