3/ The team Communication Networks and Protocols* Bibiliography - - PDF document

SLIDE 1

3/

Comm 2001-2002 1

Communication Networks and Protocols*

Introduction and Background

Danny Dolev Danny Dolev

* * The lecture notes are based in part on the lecture notes of Dr. Yuval

The lecture notes are based in part on the lecture notes of Dr. Yuval Yarom Yarom, Prof. , Prof. Raj Jain Raj Jain,, Prof. Don ,, Prof. Don Towsley Towsley and and

• Prof. S.
• Prof. S. Keshav

Keshav

2 Comm 2001-2002 Danny Dolev

The team

• Bibiliography

Bibiliography

→ → Kurose & Ross,

Kurose & Ross,

✁ ✁ Computer Networking

Computer Networking

✂ ✂

→ → A.S.

A.S.Tanenbaum Tanenbaum, ,

✁ ✁ Computer Networks (3rd Edition)

Computer Networks (3rd Edition)

✂ ✂

→ → S.

• S. Keshav

Keshav, ,

✁ ✁ An Engineering Approach to Computer Networking

An Engineering Approach to Computer Networking

✂ ✂

→ → Comer???

Comer???

→ → W.R.Stevens,

W.R.Stevens,

✁ ✁ TCP/IP Illustrated, Volume 1

TCP/IP Illustrated, Volume 1

✂ ✂

→ → Gallager

Gallager & & Bertsekas Bertsekas, ,

✁ ✁ Data Networks

Data Networks

✂ ✂

• The lecture notes are based in part on lecture notes of Prof. Don

The lecture notes are based in part on lecture notes of Prof. Don Towsley Towsley, ,

• Prof. James Kurose, Dr. Yuval
• Prof. James Kurose, Dr. Yuval Yarom

Yarom, Prof. , Prof. Raj Jain Raj Jain, Prof. Keith Ross , Prof. Keith Ross and Prof. S. and Prof. S. Keshav Keshav

3 Comm 2001-2002 Danny Dolev

Part I: Introduction

Goals: Goals:

• get context, overview,

get context, overview,

✄ ✄ feel

feel

☎ ☎ of

• f

networking networking

• more depth, detail

more depth, detail later later in course in course

• approach:

approach:

✆ ✆

descriptive descriptive

✆ ✆

use Internet as example use Internet as example Overview: Overview:

• economic drive

economic drive

• bjective
• bjective
• what

what

✝ ✝ s the Internet

s the Internet

• what

what

✝ ✝ s a protocol?

s a protocol?

• network edge

network edge

• network core

network core

• access net, physical media

access net, physical media

• performance: loss, delay

performance: loss, delay

• protocol layers, service models

protocol layers, service models

• backbones,

backbones, NAPs NAPs, ISPs , ISPs

• history

history

• ATM network

ATM network

4 Comm 2001-2002 Danny Dolev

Economic Drive

✞ ✞

Today Today

✟ ✟ s economy

s economy

✆ ✆

manufacturing, distributing, and retailing manufacturing, distributing, and retailing elements elements

✆ ✆

but also but also

✠ ✠

publishing publishing

✠ ✠

banking banking

✠ ✠

film making film making… …. .

✆ ✆

main main

✡ ✡ product

product

✝ ✝ is creation and dissemination of information

is creation and dissemination of information

✆ ✆

part of the part of the

☛ ☛information economy

information economy

☞ ☞ ✞ ✞

Future economy will to be dominated by information exchange Future economy will to be dominated by information exchange

✆ ✆

e.g. smart home and wireless tags on groceries e.g. smart home and wireless tags on groceries

5 Comm 2001-2002 Danny Dolev

The Objective

✞ ✞

Ways to represent all types of information as bits Ways to represent all types of information as bits

✞ ✞

Ways to move Ways to move lots lots of bits

• f bits everywhere, cheaply

everywhere, cheaply, and with , and with quality of quality of service service

✆ ✆

need to engineer computer networks to meet these objectives need to engineer computer networks to meet these objectives

✞ ✞

Your generation is going to merge the current networks (telephony Your generation is going to merge the current networks (telephony and Internet) with sound-fiction services. and Internet) with sound-fiction services.

6 Comm 2001-2002 Danny Dolev

Common network technologies

✞ ✞

Two successful computer networks Two successful computer networks

✆ ✆

telephone network telephone network

✆ ✆

Internet Internet

✞ ✞

What comes next? What comes next?

✆ ✆ ✄ ✄ next-generation

next-generation

☎ ☎ Internet

Internet

✆ ✆

G3 cellular technology G3 cellular technology

✆ ✆

something like universal wireless communication network something like universal wireless communication network

✞ ✞

We will study these technologies We will study these technologies

SLIDE 2

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7 Comm 2001-2002 Danny Dolev

What

s the Internet: ✁ nuts and bolts ✂ view

• millions of connected computing

millions of connected computing devices: devices: hosts, end-systems hosts, end-systems

✄ ✄

pc pc

☎ ☎ s workstations, servers

s workstations, servers

✄ ✄

PDA PDA

☎ ☎ s phones, toasters

s phones, toasters

running running network apps network apps

• communication links

communication links

✄ ✄

fiber, copper, radio, satellite fiber, copper, radio, satellite

• routers:

routers: forward packets (chunks) of forward packets (chunks) of data thru network data thru network

✆ ✝✟✞✡✠☛✆✌☞✎✍✑✏ ✞✡✝✓✒✕✔✟✠☛✖ ✗ ✖ ✘✓✙✌✚✛✝✓✜✌✢ ✜ ✘✓✣☛✤ ✝☛✖ ✠☛✆✌☞✎✍✥✏ ✜✦✝✓✧✌✙✦✘☛✜ ✚★✝✓✜✡✢✌✩✌✙✦✠✡✙✟✤ ✝☛✖ ✩✌✘☛✜✦✪✦✘✫✜ ✒✕✝✭✬✫✤ ✆ ✘

8 Comm 2001-2002 Danny Dolev

What

s the Internet: ✁ nuts and bolts ✂ view

• protocols

protocols: : control sending, receiving of control sending, receiving of msgs msgs

✄ ✄

e.g., TCP, IP, HTTP, FTP, PPP e.g., TCP, IP, HTTP, FTP, PPP

• Internet:

Internet:

✄ ✄ network of networks

network of networks

☎ ☎ ✄ ✄

loosely hierarchical loosely hierarchical

✄ ✄

public Internet versus private intranet public Internet versus private intranet

• Internet standards

Internet standards

✄ ✄

RFC: Request for comments RFC: Request for comments

✄ ✄

IETF: Internet Engineering Task Force IETF: Internet Engineering Task Force

✆ ✝✟✞✡✠☛✆✌☞✎✍✑✏ ✞✡✝✓✒✕✔✟✠☛✖ ✗ ✖ ✘✓✙✌✚✛✝✓✜✌✢ ✜ ✘✓✣☛✤ ✝☛✖ ✠☛✆✌☞✎✍✥✏ ✜✦✝✓✧✌✙✦✘☛✜ ✚★✝✓✜✡✢✌✩✌✙✦✠✡✙✟✤ ✝☛✖ ✩✌✘☛✜✦✪✦✘✫✜ ✒✕✝✭✬✫✤ ✆ ✘

9 Comm 2001-2002 Danny Dolev

What

s the Internet: a service view

• communication

communication infrastructure infrastructure enables enables distributed applications: distributed applications:

✄ ✄

WWW, email, games, e-commerce, WWW, email, games, e-commerce, database., voting, database., voting,

✄ ✄

more? more?

• communication services provided:

communication services provided:

✄ ✄

connectionless connectionless

✄ ✄

connection-oriented connection-oriented

• cyberspace [Gibson]:

cyberspace [Gibson]:

✮ ✮ a consensual hallucination experienced daily by billions of

a consensual hallucination experienced daily by billions of

• perators, in every nation, ...."
• perators, in every nation, ...."

10 Comm 2001-2002 Danny Dolev

What

s a protocol?

human protocols: human protocols:

• ✄

✄ what

what

✝ ✝ s the time?

s the time?

☎ ☎

• ✄

✄ I have a question

I have a question

☎ ☎

• introductions

introductions … … specific specific msgs msgs sent sent … … specific actions taken when specific actions taken when msgs msgs received, or other events received, or other events network protocols: network protocols:

• machines rather than humans

machines rather than humans

• all communication activity in

all communication activity in Internet governed by protocols Internet governed by protocols protocols define format, order of protocols define format, order of msgs msgs sent sent and received among network entities, and received among network entities, and actions taken on and actions taken on msg msg transmission, transmission, receipt receipt

11 Comm 2001-2002 Danny Dolev

What

s a protocol?

a human protocol and a computer network protocol: a human protocol and a computer network protocol:

✯✱✰ ✯✱✰ ✲ ✝✡✙✳✙✌✴✓✘ ✙✟✤ ✒✵✘✭✶ ✷✕✸ ✹✵✹ ✺✥✻ ✏✼✞✟✝☛✖✟✖ ✘✭✞✌✙✟✤ ✝☛✖ ✜ ✘☛✽✓✾ ✺✥✻ ✏✼✞✟✝☛✖✟✖ ✘✭✞✌✙✟✤ ✝☛✖ ✜ ✘✭✔✫✆ ✗✫✾ ✿ ❀ ❁✭❂ ❁ ❁ ❃ ❄ ❅ ❅ ❆ ❇ ❈ ❇ ❉ ❊ ❋ ❉

• ❍✦❇

❋ ❋ ❉ ❀ ■

• ❅

❈ ❏ ■ ❀ ❑ ❉ ❂ ❁ ❍ ▲✦▼ ✰ ◆ ❖✥P ◗ ✰ ❘❙❖

12 Comm 2001-2002 Danny Dolev

A closer look at network structure:

✞ ✞

network edge: network edge: applications and applications and hosts hosts

✞ ✞

network core: network core:

✆ ✆

routers routers

✆ ✆

network of networks network of networks

✞ ✞

access networks, physical access networks, physical media: media: communication links communication links

SLIDE 3

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13 Comm 2001-2002 Danny Dolev

The network edge:

✞ ✞

end systems (hosts): end systems (hosts):

✄ ✄

run application programs run application programs

✄ ✄

e.g., WWW, email e.g., WWW, email

✄ ✄

at at

✁ ✁ edge of network

edge of network

✂ ✂ ✞ ✞

client/server model client/server model

✄ ✄

client host requests, receives service from client host requests, receives service from server server

✄ ✄

e.g., WWW client (browser)/ server; email e.g., WWW client (browser)/ server; email client/server client/server

✞ ✞

peer-peer model: peer-peer model:

✄ ✄

host interaction symmetric host interaction symmetric

✄ ✄

e.g.: teleconferencing e.g.: teleconferencing

14 Comm 2001-2002 Danny Dolev

Network edge: connection-oriented service

Goal: Goal: data transfer between end sys.

data transfer between end sys.

• handshaking:

handshaking: setup (prepare for) setup (prepare for) data transfer ahead of time data transfer ahead of time

✄ ✄

Hello, hello back human protocol Hello, hello back human protocol

✄ ✄

set up set up

• state

state

✁ ✁ in two

in two communicating hosts communicating hosts

• TCP - Transmission Control

TCP - Transmission Control Protocol Protocol

✄ ✄

Internet Internet

☎ ☎ s connection-oriented

s connection-oriented service service

TCP service TCP service

[RFC 793] [RFC 793]

• reliable, in-order

reliable, in-order byte-stream data byte-stream data transfer transfer

✄ ✄

loss: acknowledgements and loss: acknowledgements and retransmissions retransmissions

• flow control:

flow control:

✄ ✄

sender won sender won

☎ ☎ t overwhelm receiver

t overwhelm receiver

• congestion control:

congestion control:

✄ ✄

senders senders

✁ ✁ slow down sending rate

slow down sending rate

✂ ✂

when network congested when network congested

15 Comm 2001-2002 Danny Dolev

Network edge: connectionless service

Goal: Goal: data transfer between end

data transfer between end systems systems

✄ ✄

same as before! same as before!

• UDP

UDP - User

• User Datagram

Datagram Protocol [RFC Protocol [RFC 768]: Internet 768]: Internet

✝ ✝ s connectionless

s connectionless service service

✆ ✆

unreliable data transfer unreliable data transfer

✆ ✆

no flow control no flow control

✆ ✆

no congestion control no congestion control

App App

✟ ✟ s using TCP:

s using TCP:

• HTTP (WWW), FTP (file transfer),

HTTP (WWW), FTP (file transfer), Telnet (remote login), SMTP (email) Telnet (remote login), SMTP (email)

App App

✟ ✟ s using UDP:

s using UDP:

• streaming media, teleconferencing,

streaming media, teleconferencing, Internet telephony Internet telephony

16 Comm 2001-2002 Danny Dolev

The Network Core

• mesh of interconnected routers

mesh of interconnected routers

• the

the fundamental question: fundamental question: how is data how is data transferred through net? transferred through net?

✆ ✆

circuit switching: circuit switching: dedicated circuit dedicated circuit per call: telephone net per call: telephone net

✆ ✆

packet-switching: packet-switching: data sent thru net data sent thru net in discrete in discrete

✄ ✄ chunks

chunks

☎ ☎

17 Comm 2001-2002 Danny Dolev

Network Core: Circuit Switching

End-end resources reserved for End-end resources reserved for

✂ ✂ call

call

✄ ✄

• link bandwidth, switch capacity

link bandwidth, switch capacity

• dedicated resources: no sharing

dedicated resources: no sharing

• circuit-like (guaranteed)

circuit-like (guaranteed) performance performance

• call setup required

call setup required

18 Comm 2001-2002 Danny Dolev

Network Core: Circuit Switching

network resources (e.g., bandwidth) network resources (e.g., bandwidth) divided into divided into

✂ ✂ pieces

pieces

✄ ✄

• pieces allocated to calls

pieces allocated to calls

• resource piece

resource piece idle idle if not used by if not used by

• wning call
• wning call (no sharing)

(no sharing)

• dividing link bandwidth into

dividing link bandwidth into

✄ ✄ pieces

pieces

☎ ☎ ✆ ✆

frequency division frequency division

✆ ✆

time division time division

SLIDE 4

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19 Comm 2001-2002 Danny Dolev

Network Core: Packet Switching

each end-end data stream divided into each end-end data stream divided into packets packets

• user A, B packets

user A, B packets share share network network resources resources

• each packet uses full link bandwidth

each packet uses full link bandwidth

• resources used

resources used as needed as needed, , resource contention: resource contention:

• aggregate resource demand can

aggregate resource demand can exceed amount available exceed amount available

• congestion: packets queue, wait for

congestion: packets queue, wait for link use link use

• store and forward: packets move

store and forward: packets move

• ne hop at a time
• ne hop at a time

✆ ✆

transmit over link transmit over link

✆ ✆

wait turn at next link wait turn at next link

Bandwidth division into Bandwidth division into

✁ ✁ pieces

pieces

✂ ✂

Dedicated allocation Dedicated allocation Resource reservation Resource reservation

20 Comm 2001-2002 Danny Dolev

Network Core: Packet Switching

Packet-switching versus circuit switching: human restaurant analogy Packet-switching versus circuit switching: human restaurant analogy

• ther human analogies?
• ther human analogies?
• ✁

✂ ✄ ☎✝✆ ✬✟✩ ✞ ✙✌✴✭✘☛✜✟✖ ✘✓✙ ✄ ✾ ✟ ✆ ✬✓✩ ✠ ✟ ✆ ✬✟✩ ✡ ☛ ✩✌✙✦✠✟✙✟✤ ✩✌✙✓✤ ✞✌✠✫✆✟✒✳✧✭✆ ✙✟✤ ✔☛✆ ✘✌☞✎✤ ✖ ✣ ✍✏✎ ✑✒✎ ✑✔✓✖✕✘✗✚✙✖✛ ✜ ✑✖✢ ✣ ✤✥✙✒✦ ✢✚✦ ✧ ★✩✕ ✓✒✪✫✓✏✎ ✢ ✗✏✎ ✢ ✬ ✦ ✧✖✜

21 Comm 2001-2002 Danny Dolev

Network Core: Packet Switching

Packet-switching: Packet-switching: store and forward behavior store and forward behavior

demo

22 Comm 2001-2002 Danny Dolev

Store and forward

✞ ✞

Metadata allows us to forward packets when we want Metadata allows us to forward packets when we want

✞ ✞

E.g. letters at a post office headed for main post office E.g. letters at a post office headed for main post office

✆ ✆

address labels allow us to forward them in batches address labels allow us to forward them in batches

✞ ✞

Efficient use of critical resources Efficient use of critical resources

✞ ✞

Three problems Three problems

✆ ✆

hard to control delay within network hard to control delay within network

✆ ✆

switches need memory for buffers switches need memory for buffers

✆ ✆

convergence of flows can lead to congestion convergence of flows can lead to congestion

23 Comm 2001-2002 Danny Dolev

Packet switching versus circuit switching

• 1

1 Mbit Mbit link link

• each user:

each user:

✄ ✄

100Kbps when 100Kbps when

✁ ✁ active

active

✂ ✂ ✄ ✄

active 10% of time active 10% of time

• circuit-switching:

circuit-switching:

✄ ✄

10 users 10 users

• packet switching:

packet switching:

✄ ✄

with 35 users, probability > 10 with 35 users, probability > 10 active less that .004 active less that .004

Packet switching allows more users to use network! Packet switching allows more users to use network!

✭✯✮✥✰☛❖✲✱✒✰ ✳✵✴✷✶✫✸✹✰ ◆ ✰ ✺✼✻

24 Comm 2001-2002 Danny Dolev

Packet switching versus circuit switching

• Great for

Great for bursty bursty data data

✆ ✆

resource sharing resource sharing

✆ ✆

no call setup no call setup

• Excessive congestion:

Excessive congestion: packet delay and loss packet delay and loss

✆ ✆

protocols needed for reliable data transfer, congestion control protocols needed for reliable data transfer, congestion control

• Q: How to provide circuit-like behavior?

Q: How to provide circuit-like behavior?

✆ ✆

bandwidth guarantees needed for audio/video apps bandwidth guarantees needed for audio/video apps still an unsolved problem still an unsolved problem Is packet switching the winner under any condition? Is packet switching the winner under any condition?

SLIDE 5

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25 Comm 2001-2002 Danny Dolev

Packet-switched networks: routing

✞ ✞

Goal: Goal: move packets among routers from source to destination move packets among routers from source to destination

✆ ✆

we we

✝ ✝ ll study several path selection algorithms

ll study several path selection algorithms

✞ ✞

datagram datagram network: network:

✆ ✆

destination address destination address determines next hop determines next hop

✆ ✆

routes may change during session routes may change during session

✆ ✆

analogy: driving, asking directions analogy: driving, asking directions

✞ ✞

virtual circuit network: virtual circuit network:

✆ ✆

each packet carries tag (virtual circuit ID), tag determines next hop each packet carries tag (virtual circuit ID), tag determines next hop

✆ ✆

fixed path determined at fixed path determined at call setup time call setup time, remains fixed thru call , remains fixed thru call

✆ ✆

routers maintain per-call state routers maintain per-call state

26 Comm 2001-2002 Danny Dolev

Access networks and physical media

Q: How to connection end systems to Q: How to connection end systems to edge router? edge router?

• residential access nets

residential access nets

• institutional access networks (school,

institutional access networks (school, company) company)

• mobile access networks

mobile access networks Keep in mind: Keep in mind:

• bandwidth (bits per second) of

bandwidth (bits per second) of access network? access network?

• shared or dedicated?

shared or dedicated?

27 Comm 2001-2002 Danny Dolev

Residential access: point to point access

• Dialup via modem

Dialup via modem

✆ ✆

up to 56Kbps direct access to router up to 56Kbps direct access to router (conceptually) (conceptually)

• ISDN:

ISDN: intergrated intergrated services digital network: services digital network: 128Kbps all-digital connect to router 128Kbps all-digital connect to router

• ADSL:

ADSL: asymmetric digital subscriber line asymmetric digital subscriber line

✆ ✆

up to 1 Mbps home-to-router up to 1 Mbps home-to-router

✆ ✆

up to 8 Mbps router-to-home up to 8 Mbps router-to-home

✆ ✆

ADSL deployment ADSL deployment – –

✄ ✄ slow start

slow start

☎ ☎

28 Comm 2001-2002 Danny Dolev

Residential access: cable modems

• HFC: hybrid fiber coax

HFC: hybrid fiber coax

✄ ✄

asymmetric: up to 10Mbps upstream, 1 asymmetric: up to 10Mbps upstream, 1 Mbps downstream Mbps downstream

• network

network of cable and fiber attaches

• f cable and fiber attaches

homes to ISP router homes to ISP router

✄ ✄

shared access to router among home shared access to router among home

✄ ✄

issues: congestion, dimensioning issues: congestion, dimensioning

• deployment: available via cable

deployment: available via cable companies, e.g., companies, e.g., MediaOne MediaOne

29 Comm 2001-2002 Danny Dolev

Institutional access: local area networks

• company/

company/univ univ local area network local area network (LAN) (LAN) connects end system to edge router connects end system to edge router

• Ethernet:

Ethernet:

✆ ✆

shared or dedicated cable connects shared or dedicated cable connects end system and router end system and router

✆ ✆

10 10 Mbs Mbs, 100Mbps, Gigabit Ethernet , 100Mbps, Gigabit Ethernet

• deployment:

deployment: institutions, home LANs institutions, home LANs soon soon

30 Comm 2001-2002 Danny Dolev

Network types

Circuit switched Packet switched

• LAN (Local Area Network)

LAN (Local Area Network) 0-2 Km 0-2 Km

• MAN (Metropolitan Area Network)

MAN (Metropolitan Area Network) 2-50 Km 2-50 Km

• WAN (Wide Area Network)

WAN (Wide Area Network) > 50 Km > 50 Km

SLIDE 6

3/

31 Comm 2001-2002 Danny Dolev

Wireless access networks

• shared

shared wireless wireless access network access network connects end system to router connects end system to router

• wireless LANs:

wireless LANs:

✄ ✄

radio spectrum replaces wire radio spectrum replaces wire

✄ ✄

e.g., Lucent e.g., Lucent Wavelan Wavelan 10 Mbps 10 Mbps

• wider-area wireless access

wider-area wireless access

✄ ✄

CDPD: wireless access to ISP router CDPD: wireless access to ISP router via cellular network via cellular network

✶✁✥✰☛❖ ✰ ◗

• ◗

✰ ✂✫✺ ❘✄✂✫✶ ✰ ◆ ❖ ☎ ✂✥✰ ◗ ✰ ✱✆✂✼✮ ◗ ❖✲✱

32 Comm 2001-2002 Danny Dolev

Physical Media

• physical link:

physical link: transmitted data bit transmitted data bit propagates across link propagates across link

• guided media:

guided media:

✄ ✄

signals propagate in solid media: signals propagate in solid media: copper, fiber copper, fiber

• unguided media:

unguided media:

✄ ✄

signals propagate signals propagate freelye freelye.g., radio .g., radio

Twisted Pair (TP) Twisted Pair (TP)

• two insulated copper wires

two insulated copper wires

✄ ✄

Category 3: traditional phone wires, Category 3: traditional phone wires, 10 Mbps 10 Mbps ethernet ethernet

✄ ✄

Category 5 TP: 100Mbps Category 5 TP: 100Mbps ethernet ethernet

33 Comm 2001-2002 Danny Dolev

Physical Media: coax, fiber

Coaxial cable: Coaxial cable:

• wire (signal carrier) within a wire

wire (signal carrier) within a wire (shield) (shield)

✄ ✄

baseband baseband: single channel on cable : single channel on cable

✄ ✄

broadband: multiple channel on broadband: multiple channel on cable cable

• bidirectional

bidirectional

• common use in 10Mbs Ethernet

common use in 10Mbs Ethernet

Fiber optic cable: Fiber optic cable:

• glass fiber carrying light pulses

glass fiber carrying light pulses

• high-speed operation:

high-speed operation:

✄ ✄

100Mbps Ethernet 100Mbps Ethernet

✄ ✄

high-speed point-to-point high-speed point-to-point transmission (e.g., 5 transmission (e.g., 5 Gps Gps) )

• low error rate

low error rate

34 Comm 2001-2002 Danny Dolev

Physical media: radio

• signal carried in electromagnetic

signal carried in electromagnetic spectrum spectrum

• no physical

no physical

✄ ✄ wire

wire

☎ ☎

• bidirectional

bidirectional

• propagation environment effects:

propagation environment effects:

✄ ✄

reflection reflection

✄ ✄

• bstruction by objects
• bstruction by objects

✄ ✄

interference interference

Radio link types: Radio link types:

• microwave

microwave

✄ ✄

e.g. up to 45 Mbps channels e.g. up to 45 Mbps channels

• LAN

LAN (e.g., (e.g., waveLAN waveLAN) )

✄ ✄

2Mbps, 11Mbps 2Mbps, 11Mbps

• wide-area

wide-area (e.g., cellular) (e.g., cellular)

✄ ✄

e.g. CDPD, 10 e.g. CDPD, 10

☎ ☎ s Kbps

s Kbps

• satellite

satellite

✄ ✄

up to 50Mbps channel (or multiple up to 50Mbps channel (or multiple smaller channels) smaller channels)

✄ ✄

270 270 Msec Msec end-end delay end-end delay

✄ ✄

geosynchronous geosynchronous versus LEOS versus LEOS

35 Comm 2001-2002 Danny Dolev

Delay in packet-switched networks

packets experience packets experience delay delay on end-to-

• n end-to-

end path end path

• four

four sources of delay at each hop sources of delay at each hop

• nodal processing

nodal processing: :

✄ ✄

check bit errors check bit errors

✄ ✄

determine output link determine output link

• queueing

queueing

✄ ✄

time waiting at output link for time waiting at output link for transmission transmission

✄ ✄

depends on congestion level of depends on congestion level of router router

• ✁

✗✖✪ ✓✏✗✚✙ ★✖✙ ✢✏✦ ✓✖✧ ✢✚✪ ✙✏✧✚✣✞✝✘✦ ✣ ✣✏✦ ✓✖✧ ✧ ✓✠✟✖✙ ✬ ✗✖✪ ✓✖✛ ✑✒✣ ✣✏✦ ✧ ★ ✍✏✎ ✑✒✎ ✑ ✦ ✧ ★

36 Comm 2001-2002 Danny Dolev

Delay in packet-switched networks

Transmission delay: Transmission delay:

• R=link bandwidth (bps)

R=link bandwidth (bps)

• L=packet length (bits)

L=packet length (bits)

• time to send bits into link = L/R

time to send bits into link = L/R Propagation delay: Propagation delay:

• d = length of physical link

d = length of physical link

• s = propagation speed in medium

s = propagation speed in medium (~2x10 (~2x108

8 m/sec)

m/sec)

• propagation delay = d/s

propagation delay = d/s

• ✁

✗✖✪ ✓✏✗✚✙ ★✖✙ ✢✏✦ ✓✖✧ ✢✚✪ ✙✏✧✚✣✞✝✘✦ ✣ ✣✏✦ ✓✖✧ ✧ ✓✠✟✖✙ ✬ ✗✖✪ ✓✖✛ ✑✒✣ ✣✏✦ ✧ ★ ✍✏✎ ✑✒✎ ✑ ✦ ✧ ★

Note: Note: s and R are s and R are very very different different quantitites quantitites! !

SLIDE 7

3/

37 Comm 2001-2002 Danny Dolev

Queueing delay (revisited)

• R=link bandwidth (bps)

R=link bandwidth (bps)

• L=packet length (bits)

L=packet length (bits)

• a=average packet arrival rate

a=average packet arrival rate traffic intensity = La/R traffic intensity = La/R

• La/R ~ 0: average

La/R ~ 0: average queueing queueing delay small delay small

• La/R -> 1: delays become large

La/R -> 1: delays become large

• La/R > 1: more

La/R > 1: more

✄ ✄ work

work

☎ ☎ arriving than can be serviced, average delay

arriving than can be serviced, average delay infinite! infinite!

38 Comm 2001-2002 Danny Dolev

Protocol

✁ Layers ✂

Networks are complex! Networks are complex!

• many

many

✄ ✄ pieces

pieces

☎ ☎ :

:

✆ ✆

hosts hosts

✆ ✆

routers routers

✆ ✆

links of various media links of various media

✆ ✆

applications applications

✆ ✆

protocols protocols

✆ ✆

hardware, software hardware, software

Question: Question:

Is there any hope of Is there any hope of organizing

• rganizing

structure of network? structure of network? Or at least our discussion of networks? Or at least our discussion of networks?

39 Comm 2001-2002 Danny Dolev

Protocol layering

✞ ✞

A network that provides many services needs many protocols A network that provides many services needs many protocols

✞ ✞

Turns out that some services are independent Turns out that some services are independent

✞ ✞

But others depend on each other But others depend on each other

✞ ✞

Protocol A may use protocol B as a Protocol A may use protocol B as a step step in its execution in its execution

✆ ✆

for example, packet transfer is one step in the execution of the reliable file for example, packet transfer is one step in the execution of the reliable file transfer protocol example transfer protocol example

✞ ✞

This form of dependency is called This form of dependency is called layering layering

✆ ✆

reliable file transfer is reliable file transfer is layered layered above packet transfer protocol above packet transfer protocol

✆ ✆

like a subroutine like a subroutine

40 Comm 2001-2002 Danny Dolev

Organization of air travel

✞ ✞

a series of steps a series of steps

✙✟✤ ✞✓✢✌✘✓✙✁ ✔✓✧✟✜✦✞✡✴✭✠✡✩✌✘✄✂ ✬✓✠✡✣✟✣✓✠✡✣✟✘☎ ✞✟✴✓✘☛✞✓✢✆✂ ✣✟✠✟✙✦✘✓✩✝ ✆ ✝✡✠✆✞✟✂ ✜✌✧✓✖✌✚✥✠✌✗ ✙✦✠☛✢✦✘☛✝✆✠✡✠ ✠✭✤ ✜✦✔☛✆ ✠✫✖ ✘ ✜ ✝✭✧✦✙✟✤ ✖ ✣ ✙✟✤ ✞✓✢✌✘✓✙✁ ✞✡✝✓✒✕✔✫✆ ✠✭✤ ✖☛✂ ✬✓✠✡✣✟✣✓✠✡✣✟✘☎ ✞☛✆ ✠✭✤ ✒☞✂ ✣✟✠✟✙✦✘✓✩✝ ✧✓✖✓✆ ✝✡✠✆✞✄✂ ✜✌✧✓✖✌✚✥✠✌✗❙✆ ✠✫✖✌✞✎✤ ✖✦✣ ✠✭✤ ✜✦✔☛✆ ✠✫✖ ✘ ✜ ✝✭✧✦✙✟✤ ✖ ✣ ✠✭✤ ✜✦✔☛✆ ✠✫✖ ✘ ✜ ✝✭✧✦✙✟✤ ✖ ✣

41 Comm 2001-2002 Danny Dolev

Organization of air travel: a different view

Layers: Layers: each layer implements a service each layer implements a service

✆ ✆

via its own internal-layer actions via its own internal-layer actions

✆ ✆

relying on services provided by layer below relying on services provided by layer below

✙✟✤ ✞✓✢✌✘✓✙✁ ✔✓✧✟✜✦✞✡✴✭✠✡✩✌✘✄✂ ✬✓✠✡✣✟✣✓✠✡✣✟✘☎ ✞✟✴✓✘☛✞✓✢✆✂ ✣✟✠✟✙✦✘✓✩✝ ✆ ✝✡✠✆✞✟✂ ✜✌✧✓✖✌✚✥✠✌✗ ✙✦✠☛✢✦✘☛✝✆✠✡✠ ✠✭✤ ✜✦✔☛✆ ✠✫✖ ✘ ✜ ✝✭✧✦✙✟✤ ✖ ✣ ✙✟✤ ✞✓✢✌✘✓✙✁ ✞✡✝✓✒✕✔✫✆ ✠✭✤ ✖☛✂ ✬✓✠✡✣✟✣✓✠✡✣✟✘☎ ✞☛✆ ✠✭✤ ✒☞✂ ✣✟✠✟✙✦✘✓✩✝ ✧✓✖✓✆ ✝✡✠✆✞✄✂ ✜✌✧✓✖✌✚✥✠✌✗❙✆ ✠✫✖✌✞✎✤ ✖✦✣ ✠✭✤ ✜✦✔☛✆ ✠✫✖ ✘ ✜ ✝✭✧✦✙✟✤ ✖ ✣ ✠✭✤ ✜✦✔☛✆ ✠✫✖ ✘ ✜ ✝✭✧✦✙✟✤ ✖ ✣

42 Comm 2001-2002 Danny Dolev

Layered air travel: services

✻ ✝✓✧✭✖ ✙✦✘☛✜☛✍ ✙✡✝✎✍ ✞✟✝✓✧✓✖ ✙✌✘☛✜✏✞✭✘✑✆ ✤ ✪✦✘✫✜ ✗ ✝✆✠ ✔✟✘☛✜ ✩✡✝☛✖ ✑✓✬✓✠✡✣✟✩ ✬✓✠✡✣✟✣✓✠✡✣✟✘✄✍ ✞☛✆ ✠✭✤ ✒☞✍ ✙✌✝✎✍ ✬✓✠✡✣✟✣✓✠✡✣✟✘✄✍ ✞☛✆ ✠✭✤ ✒✒✞✭✘✑✆ ✤ ✪✦✘✫✜ ✗ ✔✟✘✭✝✟✔✫✆ ✘ ✙✡✜ ✠☛✖ ✩✡✠✌✘✫✜✡✓✫✆ ✝✡✠✎✞✎✤ ✖ ✣✼✣✓✠✡✙✦✘ ✙✌✝✼✠✓✜✌✜✡✤ ✪✦✠✫✆✌✣✓✠✡✙✦✘ ✜✌✧✓✖✌✚✥✠✌✗✔✍ ✙✌✝✎✍ ✜✌✧✭✖✦✚✥✠✌✗✕✞✭✘✑✆ ✤ ✪✌✘☛✜ ✗ ✝✆✠ ✔✫✆ ✠✫✖ ✘ ✠✭✤ ✜✦✔☛✆ ✠✫✖ ✘ ✜ ✝✭✧✦✙✟✤ ✖ ✣✕✠✟✜✦✝✓✒ ✩✡✝✓✧✟✜✦✞✌✘ ✙✌✝✁✞☛✘✓✩✌✙✟✤ ✖ ✠✡✙✟✤ ✝☛✖

SLIDE 8

3/

43 Comm 2001-2002 Danny Dolev

Distributed implementation of layer functionality

✙✟✤ ✞✓✢✌✘✓✙✁ ✔✓✧✟✜✦✞✡✴✭✠✡✩✌✘✄✂ ✬✓✠✡✣✟✣✓✠✡✣✟✘☎ ✞✟✴✓✘☛✞✓✢✆✂ ✣✟✠✟✙✦✘✓✩✝ ✆ ✝✡✠✆✞✟✂ ✜✌✧✓✖✌✚✥✠✌✗ ✙✦✠☛✢✦✘☛✝✆✠✡✠ ✠✭✤ ✜✦✔☛✆ ✠✫✖ ✘ ✜ ✝✭✧✦✙✟✤ ✖ ✣ ✙✟✤ ✞✓✢✌✘✓✙✁ ✞✡✝✓✒✕✔✫✆ ✠✭✤ ✖☛✂ ✬✓✠✡✣✟✣✓✠✡✣✟✘☎ ✞☛✆ ✠✭✤ ✒☞✂ ✣✟✠✟✙✦✘✓✩✝ ✧✓✖✓✆ ✝✡✠✆✞✄✂ ✜✌✧✓✖✌✚✥✠✌✗❙✆ ✠✫✖✌✞✎✤ ✖✦✣ ✠✭✤ ✜✦✔☛✆ ✠✫✖ ✘ ✜ ✝✭✧✦✙✟✤ ✖ ✣ ✙✒✦ ✪ ✗ ✬ ✙✏✧ ✑✩✪ ✓✏✎ ✢✏✦ ✧ ★

• ✁

✂ ✄ ☎ ✆ ✝ ✞ ✟ ✄ ✝ ☎ ✂ ✠ ☎ ✆ ✄ ☎ ☎ ✝ ✡ ✝ ✞ ✟ ✄ ✝ ☎ ✂ ✠ ☎ ✆ ✰ ✺ ◗ ❖✲✱✓❘❙❖☞☛✕✰

• ◗

❖ ★✰ ✱ ◗ ✱

• ▼✎▼

✰ ✌✝✰✑✰ ◗ ❖✫✰ ✙✒✦ ✪ ✗ ✬ ✙✏✧ ✑✩✪ ✓✏✎ ✢✏✦ ✧ ★ ✙✒✦ ✪ ✗ ✬ ✙✏✧ ✑✩✪ ✓✏✎ ✢✏✦ ✧ ★

44 Comm 2001-2002 Danny Dolev

Why layering?

Dealing with complex systems: Dealing with complex systems:

• explicit structure allows identification, relationship of complex system

explicit structure allows identification, relationship of complex system

✝ ✝ s pieces

s pieces

✆ ✆

layered layered reference model reference model for discussion for discussion

• modularization eases maintenance, updating of system

modularization eases maintenance, updating of system

✆ ✆

change of implementation of layer change of implementation of layer

✝ ✝ s service transparent to rest of system

s service transparent to rest of system

✆ ✆

e.g., change in gate procedure doesn e.g., change in gate procedure doesn

✝ ✝ t affect rest of system

t affect rest of system

• layering considered harmful?

layering considered harmful?

45 Comm 2001-2002 Danny Dolev

Internet protocol stack

• application:

application: supporting network applications supporting network applications

✄ ✄

ftp, ftp, smtp smtp, http , http

• transport:

transport: host-host data transfer host-host data transfer

✄ ✄

tcp tcp, , udp udp

• network:

network: routing of routing of datagrams datagrams from source to from source to destination destination

✄ ✄

ip ip, routing protocols , routing protocols

• link:

link: data transfer between neighboring network data transfer between neighboring network elements elements

✄ ✄

ppp ppp, , ethernet ethernet

• physical:

physical: bits bits

✄ ✄ on the wire

• n the wire

☎ ☎ ✹✸✹✸✛◆ ✰ ✌

• ◗

✰ ✂ ✺ ◗ ✱ ✫✺ ✰✥✸ ✂✹✱ ◗ ✺☛❖ ◗✎✍ ✂✫✱ ✻ ◆ ✰ ✺✼✻ ✸ ☎✑✏ ✰✑✰ ✌ ✛◆

46 Comm 2001-2002 Danny Dolev

Layering: logical communication

✙✏✗✏✗ ✬ ✦ ✛ ✙ ✢✏✦ ✓✖✧ ✢✚✪ ✙✏✧✚✣ ✗ ✓✒✪ ✢ ✧ ✑✖✢ ✤✥✓✒✪ ✜ ✬ ✦ ✧✖✜ ✗✓✒✕✔✒✣✚✦ ✛ ✙ ✬ ✙✏✗✏✗ ✬ ✦ ✛ ✙ ✢✏✦ ✓✖✧ ✢✚✪ ✙✏✧✚✣ ✗ ✓✒✪ ✢ ✧ ✑✖✢ ✤✥✓✒✪ ✜ ✬ ✦ ✧✖✜ ✗✓✒✕✔✒✣✚✦ ✛ ✙ ✬ ✙✏✗✏✗ ✬ ✦ ✛ ✙ ✢✏✦ ✓✖✧ ✢✚✪ ✙✏✧✚✣ ✗ ✓✒✪ ✢ ✧ ✑✖✢ ✤✥✓✒✪ ✜ ✬ ✦ ✧✖✜ ✗✓✒✕✔✒✣✚✦ ✛ ✙ ✬ ✙✏✗✏✗ ✬ ✦ ✛ ✙ ✢✏✦ ✓✖✧ ✢✚✪ ✙✏✧✚✣ ✗ ✓✒✪ ✢ ✧ ✑✖✢ ✤✥✓✒✪ ✜ ✬ ✦ ✧✖✜ ✗✓✒✕✔✒✣✚✦ ✛ ✙ ✬ ✧ ✑✖✢ ✤✥✓✒✪ ✜ ✬ ✦ ✧✖✜ ✗✓✒✕✔✒✣✚✦ ✛ ✙ ✬

Each layer: Each layer:

• distributed

distributed

• ✄

✄ entities

entities

☎ ☎ implement

implement layer functions at each layer functions at each node node

• entities perform actions,

entities perform actions, exchange messages exchange messages with peers with peers

47 Comm 2001-2002 Danny Dolev

Layering: logical communication

✙✏✗✏✗ ✬ ✦ ✛ ✙ ✢✏✦ ✓✖✧ ✢✚✪ ✙✏✧✚✣ ✗ ✓✒✪ ✢ ✧ ✑✖✢ ✤✥✓✒✪ ✜ ✬ ✦ ✧✖✜ ✗✓✒✕✔✒✣✚✦ ✛ ✙ ✬ ✙✏✗✏✗ ✬ ✦ ✛ ✙ ✢✏✦ ✓✖✧ ✢✚✪ ✙✏✧✚✣ ✗ ✓✒✪ ✢ ✧ ✑✖✢ ✤✥✓✒✪ ✜ ✬ ✦ ✧✖✜ ✗✓✒✕✔✒✣✚✦ ✛ ✙ ✬ ✙✏✗✏✗ ✬ ✦ ✛ ✙ ✢✏✦ ✓✖✧ ✢✚✪ ✙✏✧✚✣ ✗ ✓✒✪ ✢ ✧ ✑✖✢ ✤✥✓✒✪ ✜ ✬ ✦ ✧✖✜ ✗✓✒✕✔✒✣✚✦ ✛ ✙ ✬ ✙✏✗✏✗ ✬ ✦ ✛ ✙ ✢✏✦ ✓✖✧ ✢✚✪ ✙✏✧✚✣ ✗ ✓✒✪ ✢ ✧ ✑✖✢ ✤✥✓✒✪ ✜ ✬ ✦ ✧✖✜ ✗✓✒✕✔✒✣✚✦ ✛ ✙ ✬ ✧ ✑✖✢ ✤✥✓✒✪ ✜ ✬ ✦ ✧✖✜ ✗✓✒✕✔✒✣✚✦ ✛ ✙ ✬ ✟✖✙✚✢ ✙ ✟✖✙✚✢ ✙

E.g.: transport E.g.: transport

✖ ✖

take data from app take data from app

✖ ✖

add addressing, reliability add addressing, reliability check info to form check info to form

✁ ✁ datagram

datagram

✂ ✂ ✖ ✖

send send datagram datagram to peer to peer

✖ ✖

wait for peer to wait for peer to ack ack receipt receipt

✖ ✖

analogy: post office analogy: post office

✟✖✙✚✢ ✙ ✙✡✜ ✠☛✖ ✩✡✔✓✝✓✜ ✙ ✙✡✜ ✠☛✖ ✩✡✔✓✝✓✜ ✙ ✙✖✛✚✜

48 Comm 2001-2002 Danny Dolev

Layering: physical communication

✙✏✗✏✗ ✬ ✦ ✛ ✙ ✢✏✦ ✓✖✧ ✢✚✪ ✙✏✧✚✣ ✗ ✓✒✪ ✢ ✧ ✑✖✢ ✤✥✓✒✪ ✜ ✬ ✦ ✧✖✜ ✗✓✒✕✔✒✣✚✦ ✛ ✙ ✬ ✙✏✗✏✗ ✬ ✦ ✛ ✙ ✢✏✦ ✓✖✧ ✢✚✪ ✙✏✧✚✣ ✗ ✓✒✪ ✢ ✧ ✑✖✢ ✤✥✓✒✪ ✜ ✬ ✦ ✧✖✜ ✗✓✒✕✔✒✣✚✦ ✛ ✙ ✬ ✙✏✗✏✗ ✬ ✦ ✛ ✙ ✢✏✦ ✓✖✧ ✢✚✪ ✙✏✧✚✣ ✗ ✓✒✪ ✢ ✧ ✑✖✢ ✤✥✓✒✪ ✜ ✬ ✦ ✧✖✜ ✗✓✒✕✔✒✣✚✦ ✛ ✙ ✬ ✙✏✗✏✗ ✬ ✦ ✛ ✙ ✢✏✦ ✓✖✧ ✢✚✪ ✙✏✧✚✣ ✗ ✓✒✪ ✢ ✧ ✑✖✢ ✤✥✓✒✪ ✜ ✬ ✦ ✧✖✜ ✗✓✒✕✔✒✣✚✦ ✛ ✙ ✬ ✧ ✑✖✢ ✤✥✓✒✪ ✜ ✬ ✦ ✧✖✜ ✗✓✒✕✔✒✣✚✦ ✛ ✙ ✬ ✟✖✙✚✢ ✙ ✟✖✙✚✢ ✙

SLIDE 9

3/

49 Comm 2001-2002 Danny Dolev

Internet structure: network of networks

• roughly hierarchical

roughly hierarchical

• national/international backbone providers

national/international backbone providers ( (NBPs NBPs) )

✄ ✄

e.g. BBN/GTE, Sprint, AT&T, IBM, UUNet e.g. BBN/GTE, Sprint, AT&T, IBM, UUNet

✄ ✄

interconnect (peer) with each other interconnect (peer) with each other privately, or at public Network Access privately, or at public Network Access Point ( Point (NAPs NAPs) )

• regional ISPs

regional ISPs

✄ ✄

connect into connect into NBPs NBPs

• local ISP

local ISP, company , company

✄ ✄

connect into regional ISPs connect into regional ISPs

✭ ✁✁

• ✭

✁✁ ✁ ✭

• ✭
• ✪

✑✏★ ✦ ✓✏✧✚✙ ✬ ✂☎✄✝✆ ✪ ✑✏★ ✦ ✓✏✧✚✙ ✬ ✂☎✄✝✆ ✬ ✓✖✛ ✙ ✬ ✂☎✄✞✆ ✬ ✓✖✛ ✙ ✬ ✂☎✄✞✆

50 Comm 2001-2002 Danny Dolev

Intranet, Internet, and Extranet

✞ ✞

Intranets are administered by a single entity Intranets are administered by a single entity

✆ ✆

e.g. campus network e.g. campus network

✞ ✞

Internet is administered by a coalition of entities Internet is administered by a coalition of entities

✆ ✆

name services, backbone services, routing services etc. name services, backbone services, routing services etc.

✞ ✞

Extranet is a marketing term Extranet is a marketing term

✆ ✆

refers to exterior customers who can access privileged Intranet services refers to exterior customers who can access privileged Intranet services

51 Comm 2001-2002 Danny Dolev

National Backbone Provider

❖✠✟ ✡☛✟ ✁✔✁ ✭✌☞✞✍✏✎ ☛✒✑✔✓ ✶✁ ✌✼✻ ✶ ✂✫✺☛❖ ✺✭❖ ◗✎✍ ✂✫✱✌✻

52 Comm 2001-2002 Danny Dolev

Internet History

✖ ✖

1961: 1961: Kleinrock Kleinrock -

• queueing

queueing theory theory shows effectiveness of packet- shows effectiveness of packet- switching switching

✖ ✖

1964: 1964: Baran Baran - packet-switching in

• packet-switching in

military nets military nets

✖ ✖

1967: 1967: ARPAnet ARPAnet conceived by conceived by Advanced Advanced Reearch Reearch Projects Agency Projects Agency

✖ ✖

1969: 1969: first first ARPAnet ARPAnet node operational node operational

✖ ✖

1972: 1972:

✄ ✄

ARPAnet ARPAnet demonstrated publicly demonstrated publicly

✄ ✄

NCP (Network Control Protocol) NCP (Network Control Protocol) first host-host protocol first host-host protocol

✄ ✄

first e-mail program first e-mail program

✄ ✄

ARPAnet ARPAnet has 15 nodes has 15 nodes

1961-1972: Early packet-switching principles 53 Comm 2001-2002 Danny Dolev

Internet History

✖ ✖

1970: 1970: ALOHAnet ALOHAnet satellite network in Hawaii satellite network in Hawaii

✖ ✖

1973: 1973: Metcalfe Metcalfe

☎ ☎ s PhD thesis proposes

s PhD thesis proposes Ethernet Ethernet

✖ ✖

1974: 1974: Cerf Cerf and Kahn - architecture for and Kahn - architecture for interconnecting networks interconnecting networks

✖ ✖

late70 late70

☎ ☎ s:

s: proprietary architectures: proprietary architectures: DECnet DECnet, , SNA, XNA SNA, XNA

✖ ✖

late 70 late 70

☎ ☎ s:

s: switching fixed length packets switching fixed length packets (ATM precursor) (ATM precursor)

✖ ✖

1979: 1979: ARPAnet ARPAnet has 200 nodes has 200 nodes Cerf Cerf and Kahn and Kahn

☎ ☎ s internetworking principles:

s internetworking principles:

✄ ✄

minimalism, autonomy - no internal minimalism, autonomy - no internal changes required to interconnect changes required to interconnect networks networks

✄ ✄

best effort service model best effort service model

✄ ✄

stateless routers stateless routers

✄ ✄

decentralized control decentralized control define today define today

☎ ☎ s Internet architecture

s Internet architecture

1972-1980: Internetworking, new and proprietary nets 54 Comm 2001-2002 Danny Dolev

Internet History

• 1983:

1983: deployment of TCP/IP deployment of TCP/IP

• 1982:

1982: smtp smtp e-mail protocol defined e-mail protocol defined

• 1983:

1983: DNS defined for name-to-IP- DNS defined for name-to-IP- address translation address translation

• 1985:

1985: ftp protocol defined ftp protocol defined

• 1988:

1988: TCP congestion control TCP congestion control

• new national networks:

new national networks: Csnet Csnet, , BITnet BITnet, , NSFnet NSFnet, , Minitel Minitel

• 100,000 hosts connected to

100,000 hosts connected to confederation of networks confederation of networks

1980-1990: new protocols, a proliferation of networks

SLIDE 10

3/

55 Comm 2001-2002 Danny Dolev

Internet History

✖ ✖

Early 1990 Early 1990

☎ ☎ s:

s: ARPAnet decomissioned ARPAnet decomissioned

✖ ✖

1991: 1991: NSF lifts restrictions on commercial NSF lifts restrictions on commercial use of use of NSFnet NSFnet (decommissioned, 1995) (decommissioned, 1995)

✖ ✖

early 1990s: early 1990s: WWW WWW

✄ ✄

hypertext [Bush 1945, Nelson 1960 hypertext [Bush 1945, Nelson 1960

☎ ☎ s]

s]

✄ ✄

HTML, http: HTML, http: Berners Berners-Lee

• Lee

✄ ✄

1994: Mosaic, later Netscape 1994: Mosaic, later Netscape

✄ ✄

late 1990 late 1990

☎ ☎ s: commercialization

s: commercialization of the

• f the

WWW WWW

Late 1990 Late 1990

✝ ✝ s:

s:

✖ ✖

• est. 50 million computers on
• est. 50 million computers on

Internet Internet

✖ ✖

• est. 100 million+ users
• est. 100 million+ users

✖ ✖

backbone links backbone links runnning runnning at 1 at 1 Gbps Gbps

1990

s: commercialization, the WWW

56 Comm 2001-2002 Danny Dolev

ATM: Asynchronous Transfer Mode nets Internet: Internet:

• today

today

✝ ✝ s

s de facto de facto standard for global standard for global data networking data networking 1980 1980

✝ ✝ s:

s:

• telco

telco

✝ ✝ s

s develop ATM: competing develop ATM: competing network standard for carrying high- network standard for carrying high- speed voice/data speed voice/data

• standards bodies:

standards bodies:

✄ ✄

ATM Forum ATM Forum

✄ ✄

ITU ITU

ATM principles: ATM principles:

✖ ✖

small (48 byte payload, 5 byte header) small (48 byte payload, 5 byte header) fixed length fixed length cells cells (like packets) (like packets)

✁ ✁

fast switching fast switching

✁ ✁

small size good for voice small size good for voice

✖ ✖

virtual-circuit network: switches virtual-circuit network: switches maintain state for each maintain state for each

✁ ✁ call

call

✂ ✂ ✖ ✖

well-defined interface between well-defined interface between

✁ ✁ network

network

✂ ✂ and

and

✁ ✁ user

user

✂ ✂ (think of

(think of telephone company) telephone company)

57 Comm 2001-2002 Danny Dolev

ATM layers

✖ ✖

ATM Adaptation Layer ATM Adaptation Layer (AAL): (AAL): interface to upper interface to upper layers layers

✁ ✁

end-system end-system

✁ ✁

segmentation/reassembly segmentation/reassembly

✖ ✖

ATM Layer: ATM Layer: cell switching cell switching

✖ ✖

Physical Physical

✂✄✂✆☎ ✂✆✝✟✞ ✗✓✒✕✔✒✣✚✦ ✛ ✙ ✬ ✂✄✂✆☎ ✂✆✝✟✞ ✗✓✒✕✔✒✣✚✦ ✛ ✙ ✬ ✂✄✂✆☎ ✂✆✝✟✞ ✗✓✒✕✔✒✣✚✦ ✛ ✙ ✬ ✂✄✂✆☎ ✂✆✝✟✞ ✗✓✒✕✔✒✣✚✦ ✛ ✙ ✬ ✂✆✝✟✞ ✗✓✒✕✔✒✣✚✦ ✛ ✙ ✬

Where Where

☎ ☎ s the application?

s the application?

✖ ✖

ATM: lower layer ATM: lower layer

✖ ✖

functionality only functionality only

✖ ✖

IP-over ATM: later IP-over ATM: later

✙✏✗✏✗ ✬ ✦ ✛ ✙ ✢✏✦ ✓✖✧ ✝✡✠ ✆☞☛✍✌✏✎✝✆ ✂ ✆ ✙✏✗✏✗ ✬ ✦ ✛ ✙ ✢✏✦ ✓✖✧ ✝✡✠ ✆☞☛✍✌✏✎✝✆ ✂ ✆ ✙✏✗✏✗ ✬ ✦ ✛ ✙ ✢✏✦ ✓✖✧ ✝✡✠ ✆☞☛✍✌✏✎✝✆ ✂ ✆ ✙✏✗✏✗ ✬ ✦ ✛ ✙ ✢✏✦ ✓✖✧ ✝✡✠ ✆☞☛✍✌✏✎✝✆ ✂ ✆

58 Comm 2001-2002 Danny Dolev

Summary

Covered a Covered a

✄ ✄ ton

ton

☎ ☎ of material!

• f material!

✖ ✖

Internet overview Internet overview

✖ ✖

what what

☎ ☎ s a protocol?

s a protocol?

✖ ✖

network edge, core, access network network edge, core, access network

✖ ✖

performance: loss, delay performance: loss, delay

✖ ✖

layering and service models layering and service models

✖ ✖

backbones, backbones, NAPs NAPs, ISPs , ISPs

✖ ✖

history history

✖ ✖

ATM network ATM network

You now hopefully have: You now hopefully have:

• context, overview,

context, overview,

✄ ✄ feel

feel

☎ ☎ of

• f

networking networking

• more depth, detail

more depth, detail later later in course in course

59 Comm 2001-2002 Danny Dolev

Next: Protocol Layering