tnk108 introduction lecture 1a

TNK108 TNK108 Datornt/Computer Networks 2010p

Scott Fowler

Lecture 1

Book for the courseBook for the course

Computer Networking: A Top-Down Approach: International Version, 5/E

James F. Kurose, University of Massachusetts, AmherstJa es u ose, U e s y o assac use s, e sKeith W. Ross, Polytechnic University, Brooklyn

Publisher: Pearson Higher Education

Sid 2

ISBN-10: 0131365487ISBN-13:9780131365483

Scott Fowler, ITN

Course Information (contd)Course Information (cont d) Literature Literature

Lecture notes

Textbook: J Kurose and K Ross Computer Textbook: J. Kurose and K. Ross, Computer Networking A Top Down Approach, 5th edition

Lecture notes and lab assignments: Lecture notes and lab assignments: http://webstaff.itn.liu.se/~scofo47/TNK108/tnk108.html(password = )

Supplement material, if needed, will be specified or handed out

Course Staff

Me -> Scott Fowler

Arash Matinrad

Scott Fowler, ITNSid 3

Course Information (contd)Course Information (cont d) Examination and grading

2 closed book written exams (3 credits)

90% -100% = 5 (ECTS A)

75% 89% = 4 (ECTS B) 75% -89% = 4 (ECTS B)

60% -74% = 3 (ECTS C)

0 -59% = fail (ECTS F)0 59% a ( C S )

Overall grade = exam, if the result of the lab assignments is pass

Lab assignments (3 credits)g ( ) Pass / fail

Show your work and results to the course staff during lab hours

Re-examination Re-examination periods, not responsible for the times

A single written exam covering the entire scope of the course

Scott Fowler, ITNSid 4

Chapter 1: roadmapChapter 1: roadmap

1.1 What is the Internet?

1.2 Network edge end systems, access networks, links

1.3 Network core circuit switching, packet switching, network structure

1 4 Delay loss and throughput in packet-switched1.4 Delay, loss and throughput in packet switched networks

1 5 Protocol layers service models1.5 Protocol layers, service models

1.6 Networks under attack: security

1.7 HistoryIntroduction 1-5

Whats the Internet: nuts and bolts view

millions of connected Mobile networkPCcomputing devices: hosts = end systems

Global ISPserver

wirelesslaptop running network apps

Home networkRegional ISP

laptopcellular handheld

i ti li k

I tit ti l t k

Regional ISP

access points

communication links fiber, copper,

radio satellite Institutional networkwiredlinks

p radio, satellite transmission

rate = bandwidth

router

rate = bandwidthrouters: forward

packets (chunks of packets (chunks of data)

Whats the Internet: nuts and bolts view

protocols control sending, Mobile networkp otoco s co t o se d g,receiving of msgs e.g., TCP, IP, HTTP, Skype,

Mobile network

Global ISPg , , , , yp ,

Ethernet

Internet: network of Home networkR i l ISPnetworks

loosely hierarchicalRegional ISP

public Internet versus private intranet

I d d

Institutional network

Internet standards RFC: Request for comments IETF: Internet Engineering

Task Force Introduction 1-7

Whats the Internet: a service view

communication infrastructure enables distributed applications:

Web, VoIP, email, games, e-commerce, file sharing

communication services provided to apps:

reliable data delivery from source to destination

best effort (unreliable) data delivery

Introduction 1-8

Whats a protocol?What s a protocol?human protocols: network protocols:u a p otoco s

whats the time?I h ti

et o p otoco s

machines rather than humans I have a question

introductions

humans

all communication activity in Internet

specific msgs sent

activity in Internet governed by protocols

protocols define format, specific actions taken

when msgs received,

protocols define format, order of msgs sent and received among network

or other events entities, and actions taken on msgtransmission receipttransmission, receipt

Introduction 1-9

Whats a protocol?What s a protocol?a human protocol and a computer network protocol:a u a p otoco a d a co pute et o p otoco

Hi

Hi TCP ti

TCP connectionrequest

HiGot thetime?

TCP connectionresponse

Get http://www.awl.com/kurose-rosstime?2:00

Get http://www.awl.com/kurose ross

timetime

Q: Other human protocols? Introduction 1-10

A closer look at network structure:A closer look at network structure:

network edge: network edge:applications and hostshosts

access networks, physical media:physical media:wired, wireless communication linkscommunication links

network core:i t t d interconnected routers

network of network of networks

Introduction 1-11

The network edge:The network edge: end systems (hosts): end systems (hosts): run application programs e g Web email e.g. Web, email at edge of network

client/server model client/server model client host requests, receives

service from always-on server e.g. Web browser/server;

email client/server peer-peer model: peer-peer model:

minimal (or no) use of dedicated servers

e.g. Skype, BitTorrent

Access networks and physical media

Q: How to connect end Q o to co ect e dsystems to edge router?

residential access nets residential access nets institutional access

networks (schoolnetworks (school, company)

mobile access networks mobile access networksKeep in mind:

b d idth (bit bandwidth (bits per second) of access network?network?

shared or dedicated?

Physical MediaPhysical MediaTwisted Pair (TP)

bit: propagates betweentransmitter/rcvr pairs two insulated copper wires

physical link: what lies between transmitter & receiver

Category 3: traditional phone wires, 10 Mbps Eth treceiver

guided media:Ethernet

Category 5: 100Mbps Ethernet signals propagate in solid

media: copper, fiber, coax

id d di

100Mbps Ethernet

unguided media: signals propagate freely, e.g.,

radioradio

Introduction 1-14

Physical Media: coax, fiber

Coaxial cable: Fiber optic cable:Coaxial cable: two concentric copper

conductors

glass fiber carrying light pulses, each pulse a bit

bidirectional baseband:

high-speed operation: high-speed point-to-point

transmission (e g 10s baseband: single channel on cable legacy Ethernet

transmission (e.g., 10 s-100s Gps)

low error rate: repeaters legacy Ethernet broadband: multiple channels on cable

pspaced far apart ; immune to electromagnetic noise

multiple channels on cable HFC (Hybrid fibre-coaxial)

Introduction 1-15

Physical media: radio

signal carried in Radio link types:s g a ca edelectromagnetic spectrum

yp terrestrial microwave

e.g. up to 45 Mbps channels no physical wire bidirectional

LAN (e.g., Wifi) 11Mbps, 54 Mbps

bidirectional propagation environment

effects:

wide-area (e.g., cellular) 3G cellular: ~ 1 Mbps

t lliteffects: reflection obstruction by objects

satellite Kbps to 45Mbps channel (or

multiple smaller channels) obstruction by objects interference

multiple smaller channels) 270 msec end-end delay geosynchronous versus low

altitude

Introduction 1-16

Internet structure: network of networks

roughly hierarchical at center: small # of well-connected large networks at center: small # of well connected large networks tier-1 commercial ISPs (e.g., Verizon, Sprint, AT&T, Qwest,

Level3), national & international coverage) g

large content distributors (Google, Akamai, Microsoft) treat each other as equals (no charges)q ( g )

IXP IXP

Ti 1 ISP & Large Content Distributor (e.g., Google)

Large Content Distributor

(e.g., Akamai)Tier 1 ISPTier-1 ISPs &Content

Distributors, interconnect

Tier 1 ISP Tier 1 ISP

interconnect (peer) privately or at Internet Exchange Points

Introduction 1-17

Exchange Points IXPs

Tier-1 ISP: e.g., Sprint

to/from backbone

POP: point-of-presence

peering.

to/from customers

Introduction 1-18


tier-2 ISPs: smaller (often regional) ISPsconnect to one or more tier-1 (provider) ISPsconnect to one or more tier-1 (provider) ISPs

each tier-1 has many tier-2 customer nets tier 2 pays tier 1 providerp y p

tier-2 nets sometimes peer directly with each other (bypassing tier 1) , or at IXP

Tier 2ISPIXP IXPTier 2

ISPTier 2

PLarge Content

Distributor (e.g., Google)


(e.g., Akamai)Tier 1 ISP

ISP ISP

Tier 1 ISP Tier 1 ISP

( g , )

Tier 2P

Introduction 1-19

Tier 1 ISP r STier 2ISP

ISP Tier 2ISP

Tier 2ISP

Tier 2ISP

Tier 2ISP


Tier 3 ISPs local ISPs Tier-3 ISPs, local ISPs customer of tier 1 or tier 2 network

last hop (access) network (closest to end systems)

Tier 2

last hop ( access ) network (closest to end systems)

Tier 2ISP

Large Content Large Content

IXP IXP

Tier 1 ISP

Tier 2ISP

Tier 2ISP

Large Content Distributor (e.g., Google)



Tier 1 ISP Tier 1 ISPTier 2

Tier 2ISP Tier 2

ISPTier 2 Tier 2 Tier 2

ISP

Introduction 1-20

ISPISP ISP ISP ISP


a packet passes through many networks from source a packet passes through many networks from source host to destination host

Tier 2Tier 2ISP

Large Content Large Content

IXP IXP

Tier 1 ISP

Tier 2ISP

Tier 2ISP

Large Content Distributor (e.g., Google)



Tier 1 ISP Tier 1 ISPTier 2

Tier 2ISP Tier 2

ISPTier 2 Tier 2 Tier 2

ISP

Introduction 1-21

ISPISP ISP ISP ISP

Chapter 1: roadmap








How do loss and delay occur?

packets queue in router bufferspackets queue in router buffers packet arrival rate to link exceeds output link capacity packets queue, wait for turn

packet being transmitted (delay)

A

BBpackets queueing (delay)

free (available) buffers: arriving packets d d (l ) f f b ffdropped (loss) if no free buffers

Introduction 1-23

Four sources of packet delay

Atransmission

A propagation

Bnodal

processing queueing

dnodal = dproc + dqueue + dtrans + dprop

dproc: nodal processing check bit errors

dqueue: queueing delay time waiting at output link check bit errors

determine output link typically < msec

time waiting at output link for transmission

depends on congestion level of routertypically msec of router

Introduction 1-24

Four sources of packet delay

Atransmission

A propagation

Bnodal

processing queueing

dnodal = dproc + dqueue + dtrans + dprop

dtrans: transmission delay: L: packet length (bits)

dprop: propagation delay: d: length of physical linkL: packet length (bits)

R: link bandwidth (bps) dtrans = L/R

d: length of physical link s: propagation speed in

medium (~2x108 m/sec)/d d d

Introduction 1-25

dprop = d/sdtrans and dpropvery different

Queueing delay (revisited)

i

n

g

R: link bandwidth (bps) L: packet length (bits)

e

q

u

e

u

e

d

e

l

a

y

a: average packet arrival rate

a

v

e

r

a

g

e

traffic intensity = La/R

a

L /R 0 La/R ~ 0: avg. queueing delay small La/R -> 1: avg. queueing delay large

La/R ~ 0

La/R > 1: more work arriving than can be serviced, average delay infinite!

Introduction 1-26

La/R -> 1

Real Internet delays and routes

What do real Internet delay & loss look like? Traceroute program: provides delay measurement

from source to router along end-end Internet path towards destination. For all i: sends three packets that will reach router i on path towards

destination

router i will return packets to sender router i will return packets to sender sender times interval between transmission and reply.

3 b 3 b3 probes

3 probes

3 probes

Introduction 1-27

Real Internet delays and routes

traceroute: gaia.cs.umass.edu to www.eurecom.fr

1 cs-gw (128.119.240.254) 1 ms 1 ms 2 ms

Three delay measurements from gaia.cs.umass.edu to cs-gw.cs.umass.edu

g ( )2 border1-rt-fa5-1-0.gw.umass.edu (128.119.3.145) 1 ms 1 ms 2 ms3 cht-vbns.gw.umass.edu (128.119.3.130) 6 ms 5 ms 5 ms4 jn1-at1-0-0-19.wor.vbns.net (204.147.132.129) 16 ms 11 ms 13 ms 5 jn1-so7-0-0-0.wae.vbns.net (204.147.136.136) 21 ms 18 ms 18 ms 6 abilene vbns abilene ucaid edu (198 32 11 9) 22 ms 18 ms 22 ms6 abilene-vbns.abilene.ucaid.edu (198.32.11.9) 22 ms 18 ms 22 ms7 nycm-wash.abilene.ucaid.edu (198.32.8.46) 22 ms 22 ms 22 ms8 62.40.103.253 (62.40.103.253) 104 ms 109 ms 106 ms9 de2-1.de1.de.geant.net (62.40.96.129) 109 ms 102 ms 104 ms10 de.fr1.fr.geant.net (62.40.96.50) 113 ms 121 ms 114 ms

trans-oceaniclink

10 de.fr1.fr.geant.net (62.40.96.50) 113 ms 121 ms 114 ms11 renater-gw.fr1.fr.geant.net (62.40.103.54) 112 ms 114 ms 112 ms12 nio-n2.cssi.renater.fr (193.51.206.13) 111 ms 114 ms 116 ms13 nice.cssi.renater.fr (195.220.98.102) 123 ms 125 ms 124 ms14 r3t2-nice.cssi.renater.fr (195.220.98.110) 126 ms 126 ms 124 ms15 lb 3t2 ft t (193 48 50 54) 135 128 13315 eurecom-valbonne.r3t2.ft.net (193.48.50.54) 135 ms 128 ms 133 ms16 194.214.211.25 (194.214.211.25) 126 ms 128 ms 126 ms17 * * *18 * * *19 f t i f (193 55 113 142) 132 128 136

* means no response (probe lost, router not replying)19 fantasia.eurecom.fr (193.55.113.142) 132 ms 128 ms 136 ms

Introduction 1-28

Chapter 1: roadmap








Protocol Layers

Networks are complex,et o s a e co p e ,

with many pieces:

h t Question: hosts routers

Question:Is there any hope of organizing structure of links of various

media

organizing structure of network?

applications protocols Or at least our discussion f t k ? protocols hardware, software

of networks?

Introduction 1-30

Organization of air travel

ti k t ( h ) ti k t ( l i )ticket (purchase)

baggage (check)

ticket (complain)

baggage (claim)

gates (load) gates (unload)

runway takeoff

airplane routing

runway landing

airplane routingairplane routing airplane routing

airplane routing

a series of steps

Introduction 1-31

Layering of airline functionality

ticket (purchase)

baggage (check)

ticket (complain)

baggage (claim

ticket

baggage

gates (load)

runway (takeoff)

airplane routing airplane routing airplane routing

gates (unload)

runway (land)

airplane routing

gate

takeoff/landing

airplane routingairplane routing

departureairport

arrivalairport

intermediate air-trafficcontrol centers

airplane routing airplane routing airplane routing airplane routing

Layers: each layer implements a service

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

relying on services provided by layer below

Introduction 1-32

Why layering?Why layering?Dealing with complex systems:Dealing with complex systems: explicit structure allows identification, relationship of

complex systems piecescomplex system s pieces

layered reference model for discussion modularization eases maintenance, updating of

system

change of implementation of layers service transparent to rest of system

e.g., change in gate procedure doesnt affect rest of system

layering considered harmful?Introduction 1-33

Internet protocol stack

application: supporting network applications application: supporting network applications FTP, SMTP, HTTP

transport: process-process data transferapplication

p p p

TCP, UDP network: routing of datagrams from source to

transport

kg g

destination

IP, routing protocolsnetwork

link link: data transfer between neighboring

network elements

Eth t 802 11 (WiFi) PPP

link

physical Ethernet, 802.11 (WiFi), PPP physical: bits on the wire

p y

Introduction 1-34

ISO/OSI reference model

presentation: allow applications to presentation: allow applications to interpret meaning of data, e.g., encryption, compression, machine-

applicationpresentation

specific conventions

session: synchronization,

presentationsession

ycheckpointing, recovery of data exchange

transportnetwork

Internet stack missing these layers! these services, if needed, must be

linkphysical, ,

implemented in application

needed?

physical

needed?

Introduction 1-35

sourceapplication

Encapsulationmessage M application

transportnetwork

li kHtHn M

segment Htdatagram

message MHt M

Hnlink

physicallink

HtHnHl Mframe

linkphysical

switch

d ti tidestinationapplicationtransportHt M

M

networklink

physicalHtHnHl M

HtHn M

HtHn M

transportnetwork

linkphysical

HtHnHl MHtHn M

t

routerphysical

Introduction 1-36

Chapter 1: roadmap








Network Security

field of network security: field of network security: how bad guys can attack computer networks how we can defend networks against attacks how to design architectures that are immune to

attacks

Internet not originally designed with (much) g y g ( )security in mind original vision: a group of mutually trusting users original vision: a group of mutually trusting users

attached to a transparent network Internet protocol designers playing catch up Internet protocol designers playing catch-up security considerations in all layers!

Introduction 1-38

Bad guys: put malware into hosts via Internet

malware can get in host from a virus worm or trojan malware can get in host from a virus, worm, or trojan horse.

spyware malware can record keystrokes, web sites visited, upload info to collection site.visited, upload info to collection site.

infected host can be enrolled in botnet used for infected host can be enrolled in botnet, used for spam and DDoS attacks.

malware often self-replicating: from one infected host, seeks entry into other hosts

Introduction 1-39

Bad guys: put malware into hosts via InternetTrojan horse worm:

i f i b i l i i

guy pu m w

hidden part of some otherwise useful software

today often in Web page

infection by passively receiving object that gets itself executed today often in Web page

(Active-X, plugin)

virus

self- replicating: propagates to other hosts, users

virus infection by receiving object

(e.g., e-mail attachment),

Sapphire Worm: aggregate scans/secin first 5 minutes of outbreak (CAIDA, UWisc data)

( g )actively executing

self-replicating: propagate itself to other hosts sersitself to other hosts, users

Introduction 1-40

Bad guys: attack server, network infrastructureDenial of Dervice (DoS): attackers make resources

(server bandwidth) unavailable to legitimate traffic by

g y ,

(server, bandwidth) unavailable to legitimate traffic by overwhelming resource with bogus traffic

1. select target2 break into hosts 2. break into hosts

around the network (see botnet)( )

3. send packets to target from compromised h

targethosts

g

Introduction 1-41

The bad guys can sniff packets

Packet sniffing:Packet sniffing: broadcast media (shared Ethernet, wireless)

promiscuous network interface reads/records all packets (e.g., including passwords!) passing by

A C

Bsrc:B dest:A payload

B

Wireshark software used for end-of-chapter l b i (f ) k t ifflabs is a (free) packet-sniffer

Introduction 1-42

The bad guys can use false sourceThe bad guys can use false source addresses

IP fiIP spoofing: send packet with false source address

A CA C

Bsrc:B dest:A payload

Introduction 1-43

The bad guys can record and playback

record-and-playback: sniff sensitive info (e.g., password), and use later

password holder is that user from system point of view

CA

B

src:B dest:A user: B; password: foo

B

l t it (th h t Ch t 8)Introduction 1-44

lots more on security (throughout, Chapter 8)

Chapter 1: roadmapChapter 1: roadmap








Internet History1961-1972: Early packet-switching principles

1961: Kleinrock - queueing theory shows effectiveness of packet switching

1972: ARPAnet public demonstration

of packet-switching

1964: Baran - packet-switching in military nets

NCP (Network Control Protocol) first host-host protocol

g y

1967: ARPAnet conceived by Advanced Research P j t A

first e-mail program ARPAnet has 15 nodes

Projects Agency

1969: first ARPAnet node operationaloperational

Introduction 1-46

Internet History1972-1980: Internetworking, new and proprietary nets

1970: ALOHAnet satellite network in Hawaii

1974: Cerf and Kahn -Cerf and Kahns internetworking

principles: 1974: Cerf and Kahn -architecture for interconnecting networks1976 Eth t t X PARC

p p minimalism, autonomy -

no internal changes required to interconnect 1976: Ethernet at Xerox PARC

late70s: proprietary architectures: DECnet, SNA,

required to interconnect networks

best effort service modelXNA

late 70s: switching fixed length packets (ATM precursor)

stateless routers decentralized control

packets (ATM precursor) 1979: ARPAnet has 200 nodes

define todays Internet architecture

Introduction 1-47

Internet Historyy1980-1990: new protocols, a proliferation of networks

1983: deployment of TCP/IP

new national networks: Csnet, BITnet, NSFnet,

1982: smtp e-mail protocol defined

Minitel

100,000 hosts p 1983: DNS defined for

name-to-IP-address

,connected to confederation of

t ktranslation

1985: ftp protocol

networks

p pdefined

1988: TCP congestion 1988: TCP congestion control

Introduction 1-48

Internet History1990, 2000s: commercialization, the Web, new apps

early 1990s: ARPAnet decommissioned

late 1990s 2000s: more killer apps: instant

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

more killer apps: instant messaging, P2P file sharing

network security to forefront( , ) early 1990s: Web hypertext [Bush 1945, Nelson

est. 50 million host, 100 million+ users

yp [ ,1960s]

HTML, HTTP: Berners-Lee backbone links running at

Gbps

1994: Mosaic, later Netscape late 1990s: commercialization of

th W bthe Web

Introduction 1-49

Internet Historyy

2010:2010:

~750 million hosts voice, video over IP P2P applications: BitTorrent

(file sharing) Skype (VoIP), PPLive (video)

more applications: YouTube, gaming, Twitter

wireless, mobility

Introduction 1-50

Introduction: SummaryCovered a ton of material! Internet overview

You now have: context overview Internet overview

whats a protocol? network edge core access

context, overview, feel of networking

more depth, detail to network edge, core, access network packet-switching versus

p ,follow!

packet-switching versus circuit-switching

Internet structureInternet structure performance: loss, delay,

throughputg p layering, service models security security history

Introduction 1-51

tnk108 introduction lecture 1a

Documents

network protocols

ethernet internet

lab assignments

p otoco s whats

network structure1

mobile networkp otoco

ects c

ects b