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ISOC-Chicago 2001John Kristoff - DePaul University1 Journey to the Center of the Internet John Kristoff +1 312 362-5878 DePaul University.

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Presentation on theme: "ISOC-Chicago 2001John Kristoff - DePaul University1 Journey to the Center of the Internet John Kristoff +1 312 362-5878 DePaul University."— Presentation transcript:

1 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

2 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

3 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...

4 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

5 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

6 ISOC-Chicago 2001John Kristoff - DePaul University6 TCP/IP sends packet to adapter

7 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

8 ISOC-Chicago 2001John Kristoff - DePaul University8 Out the card, onto the wire...

9 ISOC-Chicago 2001John Kristoff - DePaul University9 Bit by bit...

10 ISOC-Chicago 2001John Kristoff - DePaul University10 Into the walls and ceilings...

11 ISOC-Chicago 2001John Kristoff - DePaul University11 Through the patch panel...

12 ISOC-Chicago 2001John Kristoff - DePaul University12 Onto the Ethernet switch...

13 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

14 ISOC-Chicago 2001John Kristoff - DePaul University14 And out the Internet router...

15 ISOC-Chicago 2001John Kristoff - DePaul University15 To the Internet towards ISOC.org!

16 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

17 ISOC-Chicago 2001John Kristoff - DePaul University17 The IP datagram

18 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

19 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

20 ISOC-Chicago 2001John Kristoff - DePaul University20 The TCP segment

21 ISOC-Chicago 2001John Kristoff - DePaul University21 The end-to-end picture

22 ISOC-Chicago 2001John Kristoff - DePaul University22 Dana to ISOC.org TCP/IP packet

23 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

24 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

25 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

26 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

27 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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