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ISOC-Chicago 2001John Kristoff - DePaul University1 Journey to the Center of the Internet John Kristoff jtk@depaul.edu +1 312 362-5878 DePaul University Chicago, IL 60604
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ISOC-Chicago 2001John Kristoff - DePaul University2 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
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ISOC-Chicago 2001John Kristoff - DePaul University3 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...
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ISOC-Chicago 2001John Kristoff - DePaul University4 Take me to www.isoc.orgwww.isoc.org Web site clicked is www.isoc.orgwww.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?"www.isoc.org DNS server replies: "www.isoc.org = 206.131.249.182"www.isoc.org
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ISOC-Chicago 2001John Kristoff - DePaul University5 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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ISOC-Chicago 2001John Kristoff - DePaul University6 TCP/IP sends packet to adapter
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ISOC-Chicago 2001John Kristoff - DePaul University7 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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ISOC-Chicago 2001John Kristoff - DePaul University8 Out the card, onto the wire...
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ISOC-Chicago 2001John Kristoff - DePaul University9 Bit by bit...
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ISOC-Chicago 2001John Kristoff - DePaul University10 Into the walls and ceilings...
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ISOC-Chicago 2001John Kristoff - DePaul University11 Through the patch panel...
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ISOC-Chicago 2001John Kristoff - DePaul University12 Onto the Ethernet switch...
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ISOC-Chicago 2001John Kristoff - DePaul University13 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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ISOC-Chicago 2001John Kristoff - DePaul University14 And out the Internet router...
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ISOC-Chicago 2001John Kristoff - DePaul University15 To the Internet towards ISOC.org!
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ISOC-Chicago 2001John Kristoff - DePaul University16 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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ISOC-Chicago 2001John Kristoff - DePaul University17 The IP datagram
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ISOC-Chicago 2001John Kristoff - DePaul University18 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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ISOC-Chicago 2001John Kristoff - DePaul University19 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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ISOC-Chicago 2001John Kristoff - DePaul University20 The TCP segment
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ISOC-Chicago 2001John Kristoff - DePaul University21 The end-to-end picture
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ISOC-Chicago 2001John Kristoff - DePaul University22 Dana to ISOC.org TCP/IP packet
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ISOC-Chicago 2001John Kristoff - DePaul University23 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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ISOC-Chicago 2001John Kristoff - DePaul University24 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
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ISOC-Chicago 2001John Kristoff - DePaul University25 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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ISOC-Chicago 2001John Kristoff - DePaul University26 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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ISOC-Chicago 2001John Kristoff - DePaul University27 References http://www.reed.com/Papers/EndtoEnd.html http://www.reed.com/Papers/EndtoEnd.html http://www.ietf.org http://www.ietf.org RFC 2775 Internet Transparency RFC 1958 Architectural Principles of the Internet http://www.nanog.org http://www.nanog.org http://networks.depaul.edu http://networks.depaul.edu http://condor.depaul.edu/~jkristof/ http://condor.depaul.edu/~jkristof/
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