aloha dr. abramson: could we eat the telco’s lunch? evolution of computer networking
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Aloha Dr. Abramson: Could We Eat The Telco’s Lunch? Evolution of Computer Networking. Ravi Prakash Department of Computer Science. create your future. www.utdallas.edu. Surf the Net or Net the Surf?. 1970: network multiple University of Hawaii campuses. Wireless hub-and-spoke: - PowerPoint PPT PresentationTRANSCRIPT
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Aloha Dr. Abramson: Could We Eat The Telco’s Lunch?
Evolution of Computer Networking
Ravi Prakash
Department of Computer Science
create your future www.utdallas.edu
create your future www.utdallas.educreate your future www.utdallas.edu
Surf the Net or Net the Surf?
• 1970: network multiple University of Hawaii campuses.
• Wireless hub-and-spoke:– Source to central campus.– Broadcast received signal to destination.
• What if multiple sources transmit concurrently?
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ALOHA: Multiple Access
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From ALOHA to Ethernet
• No central relay.• Listen before speaking.• Jamming signal on collision.• Random back-off and retry.
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The Past: Circuit Switched
Request • Reservation based.– Dedicated resources.
• Guaranteed quality of service
• Resource utilization?
Time
Send entiremessage
Response
Data
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Do Computers Talk Like That?
• No, no, no, no, ………………..no, no, no, …………………., no, no, no, no, ………………………………., no, no, …..
• Kleinrock et al.: Why waste resources?– Unlearn what Ma Bell taught us.– Learn from the Post Office instead– IP Datagrams
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Towards Packet Switching
Time Time
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Statistical Multiplexing
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Routing & Packet Switching
Source
Destination
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Danger, Will Robinson!
• Packets being dropped by routers!• Packets corrupted over links!• Network becoming too big to discover
routes!
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The Reliability Question
• The TCP answer– Cerf & Kahn, 1974
• If at first you don’t succeed, try, try, try again.– Acknowledgments.– Timers.– Retransmissions.
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Too Big To Fail?Chop, chop, chopAS1
AS2
AS4
AS6
AS5
AS3X
Y
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Hierarchical RoutingAS1
AS2
AS4
AS6
AS5
AS3
IDR: Intra-domain routing
IDR
IDR
IDR
IDR
IDR
IDRStub ASStub AS
Transit AS
Transit AS
Transit AS
Inter-AS path
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The Crash of October,1986
• NSFnet backbone traffic dropped from 32 kbits/s to 40 bits/s!– Blame it on TCP.– If at first you don’t succeed, try, try, try
again…but don’t be bull-headed.• Van Jacobson (1987): congestion-
control algorithm.
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Network Congestion
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TCP’s Congestion & Flow Control
1 2 3 4 5 6 7 8 9 101112131415161718192021222324252627282930313233343536373839400
20
40
60
80
100
120
140
Window Size
Slo
w S
tart
Slo
w S
tart
Congestion Avoidance
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Design Principles
• Distributed control.• Keep the network core simple.• Push all the complexity to the edge of
the network.– Fundamentally different from the Telco
approach.– Facilitates creation of new applications.– Has security implications.
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Killer (?) Applications
• Email• FTP• Web browsing & search• Voice over IP• Torrent• Streaming audio and video
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Winners and Others
Winners include:• Google• Yahoo• Amazon• Skype• Vonage• Netflix
Non-winners:• Verizon• AT&T…at&t… &at t• Time Warner• Sprint• Comcast
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Net Neutrality Debate
• Carriers/ISPs unable to share in the profits of content providers.
• Are carriers trying to stifle competition?– Deep packet inspection– Metered data transport– Bundling
• Telefonica intends to charge Google for its traffic.
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Oh What a Ride!
• Last 20 years:– 9600-baud modem to 10 Mbps FIOS at
home.– Plain text email to elaborate attachments.– Travel agents to Travelocity.– AT&T to Skype and Vonage.– $3/min to $19.95/month unlimited to India.