1. Software Defined Networking
Nick McKeown
Stanford University

2. (part 1)
My talk will be in three parts. I want to keep you on your toes, so I’m not going to tell you what the 2nd and 3rd parts are yet.
To get the ball rolling, I thought I’d start by telling you a little bit about what I do.

3. Why I love my job I work with people much smarter than me.
I get to work on intellectually interesting ideas.
… that might positively change the practice.
Then, we try to actually change the practice.

4. Whatever it takes Prove a theorem Write a paper Build a demo
Talk to lots of industry people
Write a standard
Give lots of talks
Write a blog
Start a company
Build an open source tool …

5. Choosing research projects
Pick a problem that is intellectually interesting.
And improves the practice.
And industry doesn’t like (yet).

6. Ethane Martin Casado et al [Sigcomm ‘07]
Policy
“Laptops can’t accept incoming connections”
“A can’t talk to B”
Network Control Plane
Control
Packet
Forwarding
Packet
Forwarding
Packet
Forwarding
Packet
Forwarding
Packet
Forwarding

7. Microsoft: “Come on in….”
Cisco: “It will never work…”
Raw nerve.
We must be onto something.

8. Checklist Intellectually interesting. And improves the practice.
And industry doesn’t like (yet).

9. Corollary: You can’t give stuff away
Example 1: Order of magnitude faster router (1997)
Tried to give Tiny-Tera away for free.
Industry wasn’t ready.
Started Abrizio.
Example 2: Network Memory (2001)
Tried to give it away for free, to save $500M per year.
Started Nemo.
Example 3: Ethane (2007)
Tried to give it away for free; early stages of SDN.
Started Nicira.

10. I put everything in public domain
Industry
Invests huge amounts to develop and sell products.
Patents protect ideas, giving the confidence to invest.
University research
Serves society at large.
Stay ahead by running fast, not by protecting.
Makes it easier to work with industry.
If it’s good research, industry doesn’t see it yet.
Everything in public domain since 1999.

11. (part 2)
In part 2 of my talk I’m going to tell you about software defined networking. What it is, what it isn’t. What are the technical consequences and what will be some of the business consequences.

12. Urs Hölzle (Google), ONS 2012
If you are in any doubt about whether OpenFlow/SDN will be deployed in the WAN
Urs Hölzle (Google), ONS 2012

13. Software Defined Networks
Martin Casado

14. (when we clear away all the hype)
What is SDN?
(when we clear away all the hype)

15. SDN is the separation of the control plane from the forwarding plane.

16. Software Defined Network (SDN)
Control
Program
Control
Program
Control
Program
Global Network Map
Network OS
Packet
Forwarding
Abstract
Forwarding
Model
(e.g. OpenFlow)
Packet
Forwarding
Packet
Forwarding
Packet
Forwarding
Packet
Forwarding

17. The Technical Benefits (1)
Well-defined control abstraction
Control plane can run on modern servers
Can adopt software engineering best-practices
Easier to add new control programs
…or customize locally
Solve distributed systems problem once, rather than for every protocol

18. OSPF OSPF Dijkstra Network OS OS Dijkstra 5% 95% Specialized Hardware
Packet
Forwarding
Global Network Map
Network
Map
95% OS
Specialized
Hardware

19. The Technical Benefits (2)
Well-defined forwarding abstraction
e.g. OpenFlow
Vendor-agnostic interface to forwarding plane
Simpler, lower-cost, lower-power hardware

20. Match-Action Forwarding Abstraction
“Plumbing primitives”
Action Primitives
“Forward to ports 4 & 5”
“Push header Y after bit 12”
“Pop header bits 8-12”
“Decrement bits 13-18”
“Drop packet” … H H’
Match
Action F
Action(F) G
Action(G) H
Action(H)

21. Multiple Table Match-ActionHn H1 H’ \
Match
Action F1
Action(F) G1
Action(G) H1
Action(H)
Match
Action Fn
Action(F) Gn
Action(G) Hn
Action(H)

22. OpenFlow Philosophy Long-term, forwarding looking
Match: Very general, not protocol specific.
Action: Small instruction set, not protocol specific.
Make it easy to add new headers and actions.
Any network (packet, circuit, radio).
Short-term, backward looking
Match: include well-known header fields.
Action: necessary set for existing protocols.
Support existing protocols on existing switch chips.

23. New switch chips emerging
Match
Table
Action
Match
Table
Action H
Output
Queues
HEADER In
Out
Data H
Data H
Recombine
DATA

24. The Technical Benefits (3)
Well-defined forwarding behavior
The forwarding tables capture the entire forwarding behavior.
Control plane writes the forwarding state.
Therefore, we can verify its correctness.

25. Software Defined Network (SDN)
firewall.c …
if( TCP_port == SMTP)
dropPacket();
Control
Program
Control
Program
Control
Program
Global Network Map
Network OS
Match
Action A
Action(A) B
Action(B) C
Action(C)
Match
Action A
Action(A) G
Action(G) H
Action(H)
Packet
Forwarding
Packet
Forwarding
Match
Action X
Action(X) Y
Action(Y) Z
Action(Z)
Match
Action F
Action(F) G
Action(G) H
Action(H)
Packet
Forwarding
Packet
Forwarding
Match
Action A
Action(A) G
Action(G) D
Action(D)
Packet
Forwarding

26. Software Defined Network (SDN)1
firewall.c …
if( TCP_port == SMTP)
dropPacket();
Control
Program
Control
Program
Control
Program
Global Network Map 2
Network OS
Match
Action A
Action(A) B
Action(B) C
Action(C)
Match
Action A
Action(A) G
Action(G) H
Action(H)
Packet
Forwarding
Packet
Forwarding 3
Match
Action X
Action(X) Y
Action(Y) Z
Action(Z)
Match
Action F
Action(F) G
Action(G) H
Action(H)
Packet
Forwarding
Packet
Forwarding
Match
Action A
Action(A) G
Action(G) D
Action(D)
Packet
Forwarding

27. Software Defined Network (SDN)
“A can talk to B”
“Guests can’t reach PatientRecords”
“No loops”
Policy
Control
Program
Control
Program
Control
Program
Global Network Map
Network OS
Match
Action A
Action(A) B
Action(B) C
Action(C)
Match
Action A
Action(A) G
Action(G) H
Action(H)
Packet
Forwarding
Packet
Forwarding
Match
Action X
Action(X) Y
Action(Y) Z
Action(Z)
Forwarding
Behavior
Match
Action F
Action(F) G
Action(G) H
Action(H)
Packet
Forwarding
Packet
Forwarding
Match
Action A
Action(A) G
Action(G) D
Action(D)
Packet
Forwarding

28. Networks notoriously hard to debug
Today, even simple questions hard to answer:
Can host A talk to host B?
What are all the packet headers from A that can reach B?
Are there any loops in the network?
Is Group X provably isolated from Group Y?
What happens if I remove a line in the config file?

29. Header Space Analysis A B Header Data Header Data L 01110011…1

30. Header Space Analysis 1 2

31. The set of packets from A that can reach B

32. All packets from A that can reach B

33. Header Space Analysis [Kazemian NSDI ‘12]
Consequences
Abstract forwarding model; protocol independent
Finds all packets from A that can reach B
Find loops, regardless of protocol or layer
Can prove that two groups are isolated
Can verify if network adheres to policy

34. HSA as a “foundation” Analogy to Boolean algebra for logic design
HSA enables many tools and methods
Independent static checking
In-line in-controller invariance checking
Dynamic testing: Automatic test packet generation
Dynamic testing: Automatic performance monitoring
Analogy to Boolean algebra for logic design

35. SDN: Business Consequences

36. The Business Consequences
Vertical integration will finally be replaced by a more competitive industry with a level playing field.
Large growth in software industry for networking. Faster innovation.
Hardware switches will focus on capacity, fan-out and power. (Think Intel for networking).
Multi $Bn tools industry will emerge.

37. Corollary The customer and end-user will be better served
Networks will be cheaper.
Networks will be faster.
Networks will be (much) more reliable.
Networks will improve faster.
Networks will be in service of the owner, the operator, the customer and the application rather than just the high-margin vendor.
SDN is in the best interest of society at large.
To resist is to be protectionist and self-serving.

38. Vertically integrated
App
Specialized
Applications
Linux
Mac OS
Windows
(OS) or
Open Interface
Specialized
Operating
System
Microprocessor
Open Interface
Specialized
Hardware
Vertically integrated
Closed, proprietary
Slow innovation
Small industry
Horizontal
Open interfaces
Rapid innovation
Huge industry

39. Vertically integrated
App
Specialized
Features
Control
Plane or
Open Interface
Specialized
Control
Plane
Merchant
Switching Chips
Open Interface
Specialized
Hardware
Vertically integrated
Closed, proprietary
Slow innovation
Horizontal
Open interfaces
Rapid innovation

40. Tens of millions of lines of code. Closed, proprietary, outdated.
Specialized
Features
Hundreds of protocols
6,500 RFCs
Specialized
Control
Plane
Tens of millions of lines of code.
Closed, proprietary, outdated.
Specialized
Hardware
Billions of gates.
Power hungry and bloated.

41. “My box now has an OpenFlow interface too!”
What SDN isn’t
Ram in even more lines of code…
“My box now has an OpenFlow interface too!”

42. (part 3)

43. What’s new? Separation of control from forwarding.
Programmatic control of forwarding by writing entries into tables.
Transport networks have done this for decades!

44. Natural Evolution: Converged Control
Program
Control
Program
Control
Program
Global Network Map
Network OS
Direct Control of
Hardware, or
Virtual transport network
Control
Data Center
Data Center
Transport
Network
MPLS
MPLS
New ONF Working Group: Optical Transport

45. Match-Action Forwarding Abstraction
OpenFlow
OpenFlow
Packet flow
Circuit/channel
Packet flow
Match
Action F
Action(F) G
Action(G)
Match
Action F
Action(F) G
Action(G)
OpenFlow
Circuit/channel
Match
Action F
Action(F) G
Action(G)

46. Dynamic Circuit Switching
Transport
Network
Packet
Network
Packet
Network
Transport
Network
UNI
UNI

47. Why it was supposed to happen
Technology: High capacity optical crossconnects. Aggregation: High capacity packet networks. Cost: Circuit switches cost less; use less power. Standard: GMPLS.

48. Why GMPLS failed Router vendors prevented it.
GMPLS standard much too complicated.

49. OSPF-TE, RSVP-TE + many more
Packet Network
Transport Network
IP/MPLS Control Plane
OSPF-TE, RSVP-TE + many more
GMPLS Control Plane
OSPF-TE, RSVP-TE
EMS
EMS
EMS
Proprietary Interface
UNI
Vendor Islands
We Didn’t Make it Easy! 49

50. OSPF-TE, RSVP-TE + many more
Packet Network
Transport Network
IP/MPLS Control Plane
OSPF-TE, RSVP-TE + many more
GMPLS Control Plane
OSPF-TE, RSVP-TE
OSPF-TE, RSVP-TE
OSPF-TE, RSVP-TE
EMS
EMS
EMS
Proprietary Interface
UNI
Vendor Islands
GMPLS
OSPF
RSVP
175k
Quagga
50k
Linux 50

51. Good Architecture Simplifies
3% as much code!
Aggregation
Dynamic Bandwidth
Recovery
4.7k
Global Network Map
68k
Network OS
NOX
Linux
Quagga
Linux
OSPF
RSVP
50k
175k
GMPLS
Packet
Network
Packet
Network
Transport
Network

52. Conclusions
SDN is here to stay: It introduces the right abstractions into network control.
It will sweep away protectionist practices, and level the playing field.
It will enable converged control of packet and transport networks.
I don’t recommend sitting on the sidelines.

53. Apps
Specialized
Features
Specialized
Control
Plane
Specialized
Hardware

54. Apps
Network OS
Specialized
Control
Plane
Simpler
Hardware
Specialized
Hardware