Network Management - Networking - Lecture Slides, Slides of Computer Networks

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Network Management and

Software-Defined Networking (SDN)

Goal for today

• Provide the “why” of software-defined networking
  • Some history
  • Some gossip
  • And an exercise in architectural thinking
• Not much of the “what”
  • but enough that some of you will want to know more

Caveats

• I cofounded a startup (Nicira) that worked on SDN
  • My views may be biased
  • I have no financial interest in the outcome, just ego
• SDN is not a revolutionary technology…
  • …just a way of organizing network functionality
• But that’s all the Internet architecture is….
  • The Internet architecture isn’t clever, but it is deeply wise
  • We know SDN isn’t clever, but we hope it is wise….

Context

• Where did SDN come from?
• And what is the state of networking as a field?
• Keep context in mind as you learn about SDN…

Current Status of SDN

• SDN widely accepted as “ future of networking ”
  • More than 100 members in ONF (almost “everyone”)
  • Commercialized, in production use (few places)
    • E.g., controls Google’s WAN; NTT moving to deploy
• An insane level of SDN hype, and backlash…
  • SDN doesn’t work miracles, merely makes things easier
• But the real question is: why the rapid adoption?

The Field of Networking…

• Research built a great artifact: Internet
  • Mostly unrelated to academic research which came later
• CS networking now largely the study of the Internet
• Also interesting research in wireless, optical
  • Much of it is EE research into underlying technologies
  • Some wireless research (such at Katabi at MIT) broader
• But we failed to create an academic discipline

We are left with two key questions

• Why the rapid adoption of SDN?
  • What problem is it solving?
• Why is networking behind other fields in CS?
  • What is missing in the field?
• The answers are related, but will unfold slowly

Network Management

Original goals for the control plane

• Basic connectivity : route packets to destination
  • Local state computed by routing protocols
  • Globally distributed algorithms
• Interdomain policy : find policy-compliant paths
  • Done by fully distributed BGP
• For long time, these were the only relevant goals!
  • What other goals are there in running a network?

Isolation

• L2 bcast protocols often used for discovery
  • Useful, unscalable, invasive
• Want multiple logical LANs on a physical network
  • Retain usefulness, cope with scaling, provide isolation
• Use VLANs (virtual LANs) tags in L2 headers
  • Controls where broadcast packets go
  • Gives support for logical L2 networks
  • Routers connect these logical L2 networks
• No universal method for setting VLAN state

Traffic Engineering

• Want to avoid persistent overloads on links
• Choose routes to spread traffic load across links
• Two main methods:
  • Setting up MPLS tunnels
  • Adjusting weights in OSPF
• Often done with centralized computation
  • Take snapshot of topology and load
  • Compute appropriate MPLS/OSPF state
  • Send to network

Network management has many goals

• Achieving these goals is job of the control plane…
• …which currently involves many mechanisms
• Globally distributed: routing algorithms
• Manual/scripted configuration: ACLs, VLANs
• Centralized computation: Traffic engineering

How Did We Get Into This

Mess?

How Have We Managed To Survive?

• Net. admins miraculously master this complexity
  • Understand all aspects of networks
  • Must keep myriad details in mind
• This ability to master complexity is both a blessing
  • …and a curse!