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ISOC-Chicago 2001 John Kristoff - DePaul University 1
Journey to the Center of the Internet
John Kristoff
[email protected]+1 312 362-5878DePaul UniversityChicago, IL 60604
ISOC-Chicago 2001 John Kristoff - DePaul University 2
Internet as a layered architecture
Application layer Web, email
Transport layer Reliability, flow control
Internet layer Routing, global addressing
Link layer Ethernet, PPP
Physical layer Wires, radio, optical fiber
ISOC-Chicago 2001 John Kristoff - DePaul University 3
Meet Ms. Dana Paquette
She has a high-speed Internet connection
She's browsing the web
She just clicked on a web link
Let's watch...
ISOC-Chicago 2001 John Kristoff - DePaul University 4
Take me to www.isoc.org
Web site clicked is www.isoc.org
IP doesn't understand names
We must convert this to an IP address
TCP/IP software to DNS server: "What is the IP address of www.isoc.org?"
DNS server replies: "www.isoc.org = 206.131.249.182"
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Protocol stack, connect()!
Create destination TCP/IP packet using: Destination host = 206.131.249.182 Destination application = http (port 80)
Fill in source host information Source IP address Source application number Other info (we'll return to specifics later)
Send connection request
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TCP/IP sends packet to adapter
ISOC-Chicago 2001 John Kristoff - DePaul University 7
Ethernet card encapsulates data
Could be wireless, FDDI, cable modem, etc. TCP/IP packet goes into payload Ethernet dest. address = gateway router
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Out the card, onto the wire...
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Bit by bit...
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Into the walls and ceilings...
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Through the patch panel...
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Onto the Ethernet switch...
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To the campus router...
Peels off layer 2 info
Router performs lookup for IP dest.
Forwards towards destination network
Decrements time to live field
Re-computes IP checksum
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And out the Internet router...
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To the Internet towards ISOC.org!
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IP ties everything together
IP carries data end-to-end across links
Routers examine IP layer information They forward towards the destination Similar to the sorting process of postal service
Identifies both a source and destination
Unreliable - no guaranteed delivery!
Primary role of IP: to move packets around
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The IP datagram
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The case for reliability
Sometimes the network is offered more packets than it can handle Can't queue forever
Might prefer to drop packets rather than delay them
Sender can easily re-send packets
Need a protocol to ensure reliability The case for TCP!
Note: reliability is placed in the hands of end-points
We'll come back to this in a minute
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Congestion control and avoidance
TCP increases transmission rate over time
If TCP detects a packet loss it slows down
Competing TCPs lead to fairness over time
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The TCP segment
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The end-to-end picture
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Dana to ISOC.org TCP/IP packet
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End-to-end principle
Guiding principle of the Internet architecture
Considers where to put intelligence
Minimize functions and features within the communcations system
Need end-to-end functions anyway
Argues against fate-sharing and network statefulness
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Is the Internet broken?
E2E is being violated as standard practice Network address translation (NAT) Firewalls Various middleboxes
New applications are difficult to deploy
IPv6 could shift move back towards E2E
Architecture has probably changed forever
...won't come all the way back
ISOC-Chicago 2001 John Kristoff - DePaul University 25
Anything else wrong with the 'net?
Security, security and security There will continue to be major issues here Internet is based on trust relationships Host security is hard, net security doesn't work
Routing table growth Not a critical problem, but causing some concern Increase in multi-homing casing table bloat
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What's new and exciting?(or "the I finished too early slide")
Wireless
Interactive applications Voice and games
IPv6
DNS
High-speed technologies and testbeds
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References
http://www.reed.com/Papers/EndtoEnd.html
http://www.ietf.org RFC 2775 Internet Transparency RFC 1958 Architectural Principles of the Internet
http://www.nanog.org
http://networks.depaul.edu
http://condor.depaul.edu/~jkristof/