Lowering the Barriers to Innovation Jennifer Rexford Computer Science Department Princeton...
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Lowering the Barriers to Innovation
Jennifer RexfordComputer Science Department
Princeton University
http://www.cs.princeton.edu/~jrex
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Flash Back to 1984
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Fast Forward to Today
• How computers work– Electrical engineering degree at Princeton
• Making multiple computers work together– Parallel computing research at U. Michigan
• Interconnecting computers via the Internet– Research at AT&T Labs
• Designing the future Internet– Research and teaching with undergraduate
and graduate students at Princeton
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How the Internet Enables Innovation
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Innovative Applications
Shawn FanningNortheastern freshman
Napster
Tim Berners-LeeCERN ResearcherWorld Wide Web
Meg Whitman
E-Bay
iPhone apps
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Innovative Communication Media
Ethernet
Fiber optics
Cable
DSL
WiFi
Cellular
Satellite
Bluetooth
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Telephone Network
Smart Network
Dumb Terminals
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Plain Old Telephone Service (POTS)
• Dumb phones– Dial a number– Speak and listen
• Smart switches– Set up and tear down a circuit– Forward audio along the path
• Limited services– Audio– Later, fax, caller-id, …
• A monopoly for a long time
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Internet
Dumb Network
Smart Terminals
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Power at the Edge
End-to-End PrincipleWhenever possible, communications
operations should occur at the end-points of a system.
ProgrammabilityWith programmable end hosts, new
network services can be added at any time, by anyone.
And then computers became powerful and ubiquitous….
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What Does the “Dumb” Network Do?
Best-Effort Packet Delivery
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Internet Protocol (IP) Packet Switching
• Much like the postal system– Divide information into letters– Stick them in envelopes– Deliver them independently– And sometimes they get there
• What’s in an IP packet?– The data you want to
send– A header with the “from”
and “to” addresses
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Why Packets?
• Data traffic is bursty– Logging in to remote machines– Exchanging e-mail messages
• Don’t waste bandwidth– No traffic exchanged during idle periods
• Better to allow sharing of resources– Different transfers share access to same links
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Why Best Effort?
• Best-effort delivery– Packets may be lost, corrupted, delayed,
or delivered out-of order
• Keeps the network simple– No retransmission, error correction, or
guarantees of packet delivery, …
source destination
IP network
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Supporting Diverse Link Technologies
• Best-effort packet delivery over most anything– Serial link, fiber optic link, coaxial cable,
wireless• Even birds
– IP Datagrams over Avian CarriersIP over Avian Carriers was actually implemented, sending 9 packets over a distance of approximately 3 miles, each carried by an individual pigeon, and they received 4 responses, with a packet loss ratio of 55%, and a response time ranging from 3000 seconds to over 6000 seconds.
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Power to the User’s Computer
Operating System
packetsOvercome network limitations
– Retransmit lost or corrupted packets– Put the received data back in order– Slow down under congestion
Run neat applications!
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The Result: Tremendous Innovation
Internet Protocol
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So, What’s the Problem?
(And where do I come in?)
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Misplaced Trust in the End Host
• Security vulnerabilities– No strict notions of identity– Powerful computers
• Many attacks– Denial of service– Spam e-mail– Phishing– Identity theft
• How do we protectthe Internet?
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Nobody is In Charge
1
2
3
4
5
67
ClientWeb server
Around 50,000 independent networks
How to manage a global federated network?
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Hard to Change the Inside of the Internet
• Internet infrastructure– Scalability– Stability– Reliability– Performance– Energy-efficiency– Security
Internet Protocol
• Can we make the inside programmable?– To unleash a wave of innovation
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My Research Challenge
• A future Internet worthy of our trust– More secure, scalable, stable, reliable,
efficient, …– More flexible and evolvable over time
• Despite all the challenges– Greedy and malicious users– Networks driven by economics and politics
• Without losing all the good stuff– Innovative applications – Innovative communication media
• I think this will keep me busy for awhile!
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What I Love About My Job
• Learn new stuff all the time• Pick the research problems I work on• Pick the people I want to work with• Have real impact on the world today• And (hopefully) bigger impact in the
future• While wearing jeans to work every day!
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Thanks!
(Any Questions?)