Transcript Internet - Department of Computer Science

Lowering the Barriers to Innovation
Jennifer Rexford
Computer 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
Tim Berners-Lee
CERN Researcher
World Wide Web
Shawn Fanning
Northeastern freshman
Napster
Meg
Whitman
E-Bay
iPhone
apps
Innovative Communication Media
Cable
Satellite
DSL
Cellular
Ethernet
Bluetooth
WiFi
Fiber optics
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 Principle
Whenever possible, communications operations
should occur at the end-points of a system.
Programmability
With 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 Carriers
IP 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
Run neat applications!
Operating System
packets
Overcome network limitations
– Retransmit lost or corrupted packets
– Put the received data back in order
– Slow down under congestion
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 protect
the Internet?
Nobody is In Charge
Around 50,000 independent networks
4
3
5
2
7
1
6
Web server
Client
How to manage a global federated network?
Hard to Change the Inside of the Internet
• Internet infrastructure
Internet Protocol
– Scalability
– Stability
– Reliability
– Performance
– Energy-efficiency
– Security
• 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
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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?)