Lowering the Barriers to Innovation Jennifer Rexford Computer Science Department Princeton University jrex.

Lowering the Barriers to Innovation

Jennifer RexfordComputer Science Department

Princeton University

http://www.cs.princeton.edu/~jrex

Flash Back to 1984

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

How the Internet Enables Innovation

Innovative Applications

Shawn FanningNortheastern freshman

Napster

Tim Berners-LeeCERN ResearcherWorld Wide Web

Meg Whitman

E-Bay

iPhone apps

Innovative Communication Media

Ethernet

Fiber optics

Cable

DSL

WiFi

Cellular

Satellite

Bluetooth

Telephone Network

Smart Network

Dumb Terminals

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

Internet

Dumb Network

Smart Terminals

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….

What Does the “Dumb” Network Do?

Best-Effort Packet Delivery

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

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

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

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.

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!

The Result: Tremendous Innovation

Internet Protocol

So, What’s the Problem?

(And where do I come in?)

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?

Nobody is In Charge

1

2

3

4

5

67

ClientWeb server

Around 50,000 independent networks

How to manage a global federated network?

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

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!

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!

Thanks!

(Any Questions?)