ISOC-Chicago 2001 John Kristoff - DePaul University 1

Journey to the Center of the Internet

John Kristoff

jtk@depaul.edu+1 312 362-5878DePaul UniversityChicago, IL 60604

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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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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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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

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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

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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/