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Software Defined Networking

Textbook Note

This section summarizes the content in the SDN Textbook: Chapter 1-3

Introduction

Keywords

Software Defined Networks

A network in which the control plane is physically separate from the forwarding plane, and a single control plane controls several forwarding devices

Bare-Metal

hardwares without a bundled operating system or a set of network applications



Planes: Control Plane and Data Plane

Control Plane Data Plane
General Description
  • Usually implemented on general purpose CPU
  • Determines how and where packets are forwarded
    		•
  • Usually implemented on high-speed hardware
  • Forwarding state + packet header → forwarding decision
    		•
    Specific Task
  • Routing
  • Traffic engineering
  • Failure detection/recovery
    		•
  • IP forwarding
    		•

    Control Plane: Centralized vs Distributed

    Centralized Distributed

    Data Plane: Programmable vs Fixed Function

    Programmable Fixed Function

    Use Case

    How does SDN progress outside of academia?

    The industries are slowing pushing SDN development forwards. However, unlike in academia, which uses pure-play SDN for research and exploration purposes, industries are very careful about centralizing their control plane. Therefore, ISPs like AT&T usually deploy a hybrid SDN. Also, network businesses are more interested in logical control plane than an open API for data plane due to protfits and their business models



    Network Virtualization



    Switching Fabrics



    Traffic Engineering for WANs

    • Without a central view of all traffic across the network, there is no way to find an optimized path. This is because locally optimized decision may not be the globally optimized decision, and therefore cause inefficiency and ineffectiveness in the global network



    Ways that a centralized SDN controllers can optimize traffic flow engineering

    1. Calculate globally optimized paths
    2. Obtain traffic flow information and classify priorities for different types of data flow.



    Basic Architecture

    Lecture Note

    Questions

    My questions for the Texbook

    1. Do we have a clearer definition for the boundary between the control plane and the data plane?
      A:

    2. How can you implement a centralized control plane at the scale of the Internet?
      A:

    3. How is non-SND network out-of-band management different from SDN control plane?
      A:

    4. What does northbound API mean?
      A:

    5. How do control plane and data plane in virtual network work?
      A:

    6. Can you elaborate more on MPLS?
      A:

    7. Why does MPLS-GBP VPNs still need connection to nearby Telcos?
      A:

    8. How is leaf-spine topology different from Clos topology?

    9. What is flow objectives (as compared to standard legacy protocols)?

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