[PDF] - Introduction and Background Danny Dolev Danny Dolev * The lecture PDF Document

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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

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Part I: Introduction

Goals: Goals:

get context, overview,

get context, overview,

feel

f
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

what

what

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

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

is creation and dissemination of information

part of the

part of the

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

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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

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

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Whats 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

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Whats 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

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

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Whats 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

Whats a protocol?

human protocols: human protocols:

what

what

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

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Whats a protocol?

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

✂✁☎✄✝✆✞✄✟✄✟✠✞✡

☛☞☛☞✌✎✍☎✏ ✍☎✑ ✒✔✓☎✑ ✕✗✖✘✍☞✓☞✓☎✑ ✁✞✙✚✕✗☛✎✏ ✛✟✙✜✁☎✢✣✑ ✆✞✄☞✖

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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

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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

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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:

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:

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

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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 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

frequency division

frequency division

time division

time division

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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?

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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

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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!

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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?

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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

✁ ✁

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?

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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

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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

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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

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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

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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

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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

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

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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

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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! !

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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

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

:

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?

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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

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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

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Layered air travel: services

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Distributed implementation of layer functionality

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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

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

e.g., change in gate procedure doesn

e.g., change in gate procedure doesn

t affect rest of system

layering considered harmful?

layering considered harmful?

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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

n the wire
n the wire
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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

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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

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Layering: physical communication

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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

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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

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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

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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

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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:

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:

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)

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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

f 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

f
f

networking networking

more depth, detail

more depth, detail later later in course in course

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59 Comm 2001-2002 Danny Dolev