cs2505 network computingcjs/pub/lectures/01-basics.pdfq: how to connect end systems to edge router?...

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CS2505Network Computing

Prof. Cormac J. Sreenan

University College Cork CS2505 1

Copyright Notice: The CS2505 lecture notes are adapted from material provided by J.F. Kurose and K.W. Ross and includes material by C.J. Sreenan, L.L.. Peterson, B.S. Davie and others. This material is copyrighted and so these lecture notes must not be copied or distributed without permission.

Instructor Details

EmailFor Prof Sreenan: cjs@cs ucc ieFor Prof. Sreenan: [email protected] put CS2505 in “Subject” line of messageAlways send from cs.ucc.ie to avoid being labelled as spam

Office Hours


Office HoursFor Prof. Sreenan: normally Tues. 3-4pm, or by appointment (better!). Room 1-75

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Course Information

CS2505 is a 5-credit module24 lectures plus practical laboratory sessions24 lectures plus practical laboratory sessionsTwo lectures per week (Period 2 only)

AssessmentSummer Exam. 80%Lab. assignments 20%

C s bsit


Course websitewww.cs.ucc.ie/~cjs/teach/CS2505Lecture notes added as the course progresses; also lab. details

Textbooks

Required to purchase:J Kurose & K Ross “Computer J. Kurose & K. Ross, Computer Networking”, Addison-Wesley Pub.Preferably 5th edition (Java)

Other good books (in library):L. Peterson and B. Davie. "Computer Networks: A Systems Approach“. Morgan Kaufmann Pub 4th Edition


Morgan Kaufmann Pub. 4 Edition (2007)A. Tanenbaum, "Computer Networks", Prentice Hall Pub. 4th edition (2002)

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Course Overview

Networking Basics

Application layer

Transport layer


Network Management

Part 1: IntroductionOur goal:

get “feel” and t i l

Overview:what’s the Internet?

terminologymore depth, detail later in courseapproach:

use Internet as example

what’s a protocol?network edge; hosts, access net, physical medianetwork core: packet/circuit switching, Internet structureperformance: loss delay


performance: loss, delay, throughputsecurityprotocol layers, service modelshistory

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Part 1: roadmap

1.1 What is the Internet?1 2 Network edge1.2 Network edge

end systems, access networks, links1.3 Network core

circuit switching, packet switching, network structure1.4 Delay, loss and throughput in packet-switched

networks1 5 P l l i d l


1.5 Protocol layers, service models1.6 Networks under attack: security1.7 History

What’s the Internet: “nuts and bolts” view

millions of connected computing devices: hosts = end systems

Mobile network

Global ISP

PC

server

hosts = end systemsrunning network apps Home network

Institutional network

Regional ISP

wirelesslaptopcellular handheld

wired

access points

communication linksfibre, copper, radio, satellite


router

wiredlinks transmission

rate = bandwidthrouters: forward packets (chunks of data)

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“Cool” internet appliances

Web-enabled toaster +

IP picture framehttp://www.ceiva.com/

weather forecaster


World’s smallest web serverhttp://www-ccs.cs.umass.edu/~shri/iPic.html Internet phones

What’s the Internet: “nuts and bolts” view

protocols control sending, receiving of msgs

TCP IP HTTP Sk

Mobile network

Global ISPe.g., TCP, IP, HTTP, Skype, Ethernet

Internet: “network of networks”

loosely hierarchicalpublic Internet versus private intranet

Home network

Institutional network

Regional ISP


private intranetInternet standards

RFC: Request for commentsIETF: Internet Engineering Task Force

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What’s the Internet: a service viewcommunication infrastructure enables distributed applications:distributed applications

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

communication services provided to apps:

reliable data delivery from source to


from source to destination“best effort” (unreliable) data delivery

What’s a protocol?human protocols:

“what’s the time?”network protocols:

machines rather than h“I have a question”

introductions

… specific msgs sent… specific actions taken

when msgs received

humansall communication activity in Internet governed by protocols

protocols define format, order of msgs sent and


when msgs received, or other events

order of msgs sent and received among network

entities, and actions taken on msg

transmission, receipt

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What’s a protocol?a human protocol and a computer network protocol:

Hi

HiGot thetime?2:00

TCP connectionrequest

TCP connectionresponseGet http://www.facebook.com


Q: Other human protocols?

2:00<file>

time

Part 1: roadmap







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A closer look at network structure:network edge:applications and pphostsaccess networks, physical media:wired, wireless communication links


network core:interconnected routersnetwork of networks

The network edge:end systems (hosts):

run application programse.g. Web, emailat “edge of network”

client/server

peer-peer

client/server modelclient host requests, receives service from always-on servere.g. Web browser/server; m il li nt/s


email client/serverpeer-peer model:

minimal (or no) use of dedicated serverse.g. Skype, BitTorrent

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Access networks and physical media

Q: How to connect end systems to edge router?

d l residential access netsinstitutional access networks (university, company)mobile access networks

Keep in mind:

University College Cork CS2505 17-17

Keep in mind: bandwidth (bits per second) of access network?shared or dedicated?

Concept of Bandwidth

Amount of data that can be transmitted per time unitper time unit

Example: 10 Mega bits per second (Mb/s or Mbps) or 100 Kilo bits per second (Kb/s)Also called data rate or capacity

Notation distinguish between bits (b) and bytes (B)distinguish between bits (b) and bytes (B)One byte = 8 bits; bytes sometimes called octetsKb/s = 103 bits per second; Mb/s = 106 bits per second


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telephonenetwork Internet

central office

Dial-up Modem

homedial-upmodem

ISPmodem(e.g., eircom)

homePC

Uses existing telephony infrastructure


Uses existing telephony infrastructureHome is connected to central office

up to 56Kb/s direct access to router (often less)Can’t surf and phone at same time: not “always on”

homephone

InternetExisting phone line:0-4KHz phone; 4-50KHz upstream data; 50KHz-1MHz downstream data

Digital Subscriber Line (DSL)

telephonenetwork

DSLmodem

homePC

DSLAM

splitter

centraloffice


Also uses existing telephone infrastructureup to 3.5 Mb/s upstream (today typically < 1 Mb/s)up to 24 Mb/s downstream (today typically < 8 Mb/s)dedicated physical line to telephone central office

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Residential access: cable modems

Does not use telephone infrastructureInstead uses cable TV infrastructureInstead uses cable TV infrastructure

HFC: hybrid fibre coaxasymmetric: up to 30Mb/s downstream, 2 Mb/s upstream

network of cable and fibre attaches homes to ISP router

University College Cork CS2505 21-21

homes share access to router unlike DSL, which has dedicated access

Residential access: cable modems

University College Cork CS2505 22Diagram: http://www.cabledatacomnews.com/cmic/diagram.html

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Cable Network Architecture: Overview

Typically 500 to 5,000 homes


home

cable headend

cable distributionnetwork (simplified)


server(s)


home

cable headend

cable distributionnetwork

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home

cable headend

cable distributionnetwork (simplified)


CO

FDM (more shortly):

Channels

VIDEO

VIDEO

VIDEO

VIDEO

VIDEO

VIDEO

DATA

DATA

NTROL

1 2 3 4 5 6 7 8 9


home

cable headend

cable distributionnetwork

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ONT

ONT

opticalfibres

Internet

Fibre to the HomeONT= Optical Network TerminatorOLT = Optical Line Terminator

OLT

central officeopticalsplitter

ONT

ONT

opticalfibre

Optical links from central office to the home


pTwo competing optical technologies:

Passive Optical network (PON) Active Optical Network (PAN)

Much higher Internet rates; fibre also carries television and phone services

100 Mb/s

Ethernet

Institutionalrouter

To Institution’s

Ethernet Internet access

100 Mb/s

100 Mb/s1 Gb/s

server

Ethernetswitch ISP


server

Typically used in companies, universities, etc10 Mb/s, 100Mb/s, 1Gb/s, 10Gb/s EthernetToday, end systems typically connect into Ethernet switch

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Wireless access networksshared wireless access network connects end system to routerto router

via base station aka “access point”

wireless LANs:802.11b/g (WiFi): 11 or 54 Mb/s

wider-area wireless accessprovided by telco operator

basestation

router


provided by telco operatorUp to 2Mb/s over 3G cellular system 100 Mb/s to 1 Gb/s in 4G cellular systems

mobilehosts

Home networksTypical home network components:

DSL or cable modemt /fi ll/NATrouter/firewall/NAT

Ethernetwireless accesspoint

wirelesslaptops

modem


wirelessaccess point

laptopsrouter/firewall

to/fromCable or

phone network

Ethernet

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Physical Media

Bit: propagates betweentransmitter/rcvr pairs

Twisted Pair (TP)two insulated copper wirestransmitter/rcvr pairs

physical link: what lies between transmitter & receiverguided media:

signals propagate in solid media: copper fibre coax

wiresCategory 3: traditional phone wires, 10 Mb/s EthernetCategory 5: 100Mb/s Ethernet


media: copper, fibre, coaxunguided media:

signals propagate freely, e.g., radio

Physical Media: coax, fibre

Coaxial cable:two concentric copper

d t

fibre optic cable:glass fibre carrying light pulses each pulse a bitconductors

bidirectionalbaseband:

single channel on cablelegacy Ethernet

broadband:multiple channels on

pulses, each pulse a bithigh-speed operation:

high-speed point-to-point transmission (e.g., 10-100 Gps)

low error rate: repeaters spaced far apart ; immune


multiple channels on cableHFC

spaced far apart ; immune to electromagnetic noise

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Physical media: radio

signal carried in electromagnetic spectrum

Radio link types:terrestrial microwave

t 45 Mb/ h lspectrumno physical “wire”bidirectionalpropagation environment effects:

reflection

e.g. up to 45 Mb/s channelsLAN (e.g., Wifi)

11Mb/s, 54 Mb/swide-area (e.g., cellular)

3G cellular: ~ 2 Mb/ssatellite


obstruction by objectsinterference

Kb/s to 45Mb/s channel (or multiple smaller channels)270 msec end-end delaygeosynchronous versus low altitude

Part 1: roadmap







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The Network Core

mesh of interconnected routersroutersthe fundamental question: how is data transferred through net?

circuit switching:dedicated circuit per call: telephone net


call: telephone netpacket-switching: data sent thru net in discrete “chunks”

Network Core: Circuit Switching

End-end resources reserved for “call”reserved for calllink bandwidth, switch capacitydedicated resources: no sharingcircuit-like


(guaranteed) performancecall setup required

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Network Core: Circuit Switchingnetwork resources

(e.g., bandwidth) dividing link bandwidth into “pieces”

divided into “pieces”pieces allocated to callsresource piece idle if not used by owning call (no sharing)

frequency divisiontime division


Circuit Switching: FDM and TDM

FDM 4 usersExample:

frequency

timeTDM


frequency

time

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Numerical example

How long does it take to send a file of 640 000 bits from host A to host B over a 640,000 bits from host A to host B over a circuit-switched network?

All links are 1.536 Mb/sEach link uses TDM with 24 slots/sec500 msec to establish end-to-end circuit


Let’s work it out!

Network Core: Packet Switchingeach end-end data stream

divided into packets B k h

resource contention:aggregate resource d d d user A, B packets share

network resourceseach packet uses full link bandwidth resources used as needed

demand can exceed amount availablecongestion: packets queue, wait for link usestore and forward: packets move one hop


p pat a time

Node receives complete packet before forwarding

Bandwidth division into “pieces”Dedicated allocationResource reservation

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Packet Switching: Statistical Multiplexing

A C100 Mb/sEthernet statistical multiplexing

B1.5 Mb/s

D E

queue of packetswaiting for output

link


Sequence of A & B packets does not have fixed pattern, bandwidth shared on demand statistical multiplexing.

TDM: each host gets same slot in revolving TDM frame.

E

Packet-switching: store-and-forward

R R RL

takes L/R seconds to transmit (push out) packet of L bits on to link at R b/sstore and forward: entire packet must arrive at router before

Example:L = 7.5 MbitsR = 1.5 Mb/stransmission delay = 15 sec


arrive at router before it can be transmitted on next linkdelay = 3 L/R (assuming zero propagation delay)

more on delay shortly …

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Packet switching versus circuit switching

1 Mb/s link

Packet switching allows more users to use network!1 Mb/s linkeach user:

100 kb/s when “active”active 10% of time

circuit-switching:10 users

N users1 Mb/s link


10 userspacket switching:

At least 10; depends on probability of users being active at same time

Packet switching versus circuit switching

great for bursty data

Is packet switching a clear winner?

great for bursty dataresource sharingsimpler, no call setup

excessive congestion: packet delay and lossprotocols needed for reliable data transfer, congestion control

University College Cork CS2505 44Introduction 1-44

Q: How to provide circuit-like behavior?bandwidth guarantees needed for audio/video appsstill an unsolved problem

Q: human analogies of reserved resources (circuit switching) versus on-demand allocation (packet-switching)?

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Internet structure: network of networks

roughly hierarchicalat center: “tier-1” ISPs (e.g., Global Crossing, Level 3, g gSprint, AT&T), national/international coverage

treat each other as equals

Tier 1 ISPTier-1 providers interconnect


Tier 1 ISP Tier 1 ISP

interconnect (peer) privately

Tier-1 ISP: e.g., Sprint

POP: point-of-presence

…

to/from customers

peering

to/from backbone

….

………


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“Tier-2” ISPs: smaller (often regional) ISPsConnect to one or more tier-1 ISPs, possibly other tier-2 ISPs

Tier 1 ISPTier-2 ISPTier-2 ISPTier-2 ISP pays

tier-1 ISP for connectivity to rest of Internet

Tier-2 ISPs also peer privately with each other.



Tier-2 ISP Tier-2 ISP

Tier-2 ISP

tier-2 ISP is customer oftier-1 provider


“Tier-3” ISPs and local ISPs last hop (“access”) network (closest to end systems)

Tier 1 ISPTier-2 ISPTier-2 ISP

localISPlocal

ISPlocalISP

localISP Tier 3

ISPLocal and tier-3 ISPs are customers ofhigher tier ISPs




Tier-2 ISP

localISP

localISP

localISP

localISP

ISPsconnecting them to rest of Internet

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a packet passes through many networks!

Tier 1 ISPTier-2 ISPTier-2 ISP

localISPlocal

ISPlocalISP

localISP Tier 3

ISP




Tier-2 ISP

localISP

localISP

localISP

localISP

Part 1: roadmap







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How do loss and delay occur?packets queue in router buffers

packet arrival rate to link exceeds output link p pcapacitypackets queue, wait for turn

A

packet being transmitted (delay)


Bpackets queueing (delay)

free (available) buffers: arriving packets dropped (loss) if no free buffers

Four sources of packet delay

1. nodal processing:check bit errors

2. queueingtime waiting at output check bit errors

determine output link

A propagation

transmission

time waiting at output link for transmission depends on congestion level of router


B

propagation

nodalprocessing queuing

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Delay in packet-switched networks3. Transmission delay:

R=link bandwidth (b/s)4. Propagation delay:

d = length of physical linkL=packet length (bits)time to send bits into link = L/R

s = propagation speed in medium (~2x108 m/sec for copper)propagation delay = d/s

t smissi

Note: s and R are very different quantities!


A

B

propagation

transmission

nodalprocessing queueing

Vehicle analogy

toll toll ten-car convoy

100 km 100 km

cars “propagate” at 100 km/hrtoll booth takes 12 sec to service car (transmission time)

Time to “push” all cars through toll booth onto highway = 12*10 = 120 secTime for last car to

boothboothconvoy


)car~bit; convoy~packetQ: How long until cars are lined up before 2nd toll booth?

propagate from 1st to 2nd toll both: 100km/(100km/hr)= 1 hrA: 62 minutes

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Vehicle analogy (more)

toll toll ten-carconvoy

100 km 100 km

Cars now “propagate” at 1000 km/hrToll booth now takes 1 min to service a car

Yes! After 7 min, 1st car at 2nd booth and 3 cars still at 1st booth.1st bit of packet can arrive at 2nd router

boothboothconvoy


Q: Will cars arrive to 2nd booth before all cars serviced at 1st booth?

before packet is fully transmitted at 1st router!

Nodal delayproptransqueueprocnodal ddddd +++=

dproc = processing delaytypically a few microsecs or less

dqueue = queuing delaydepends on number of hops (routers) and traffic

dtrans = transmission delay


trans y= L/R, significant for low-speed links

dprop = propagation delaya few microsecs to hundreds of millisecs (msecs)

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Queueing delay (revisited)

R=link bandwidth (b/s)L=packet length (bits)L=packet length (bits)a=average packet arrival rate

traffic intensity = La/Rwhere La is arrival rate

L /R 0 i d l ll


La/R ~ 0: average queueing delay smallLa/R -> 1: delays become largeLa/R > 1: more “work” arriving than can be serviced, average delay infinite!

“Real” Internet delays and routes

What do “real” Internet delay & loss look like? 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 destinationrouter i will return packets to senderrouter i will return packets to sendersender times interval between transmission and reply.


3 probes

3 probes

3 probes

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“Real” Internet delays and routestraceroute: gaia.cs.umass.edu to www.eurecom.fr

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

1 cs-gw (128.119.240.254) 1 ms 1 ms 2 ms2 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 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 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 ms

g m g m

trans-oceaniclink


12 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 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 fantasia.eurecom.fr (193.55.113.142) 132 ms 128 ms 136 ms

* means no response (probe lost, router not replying)

Packet loss

queue (aka buffer) preceding link has finite capacitycapacitypacket arriving to full queue dropped (aka lost)lost packet may be retransmitted by previous node, by source end system, or not at all

Apacket being transmitted

buffer (waiting area)


A

Bpacket arriving tofull buffer is lost

( g )

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Throughputthroughput: rate (bits/time unit) at which bits transferred between sender/receiver

instantaneous: rate at given point in timeaverage: rate over longer period of time


server, withfile of F bits

to send to client

link capacityRs bits/sec

link capacityRc bits/sec

pipe that can carryfluid at rateRs bits/sec)

pipe that can carryfluid at rateRc bits/sec)

server sends bits (fluid) into pipe

Throughput (more)Rs < Rc What is average end-end throughput?

Rs bits/sec Rc bits/sec

Rs > Rc What is average end-end throughput?

R bits/s R bit /


Rs bits/sec Rc bits/sec

link on end-end path that constrains end-end throughputbottleneck link

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Throughput: Internet scenario

Rs Rs

Rs

Rs

Rc Rc

R

per-connection end-end throughput: min(Rc,Rs,R/10)in practice: Rc or R i ft


10 connections (fairly) share backbone bottleneck link R bits/sec

RcRs is often bottleneck

Part 1: roadmap







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Protocol “Layers”Networks are complex!

many “pieces”:hostsrouterslinks of various mediaapplicationsprotocols

Question:Is there any hope of organizing structure of

network?

Or at least our discussion


protocolshardware, software

Or at least our discussion of networks?

Organization of air travel

ticket (purchase) ticket (complain)

lbaggage (check)

gates (load)

runway takeoff

airplane routing

baggage (claim)

gates (unload)

runway landing

airplane routing

l


a series of steps

airplane routing

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ticket (purchase) ticket (complain) ticket

Layering of airline functionality

baggage (check)

gates (load)

runway (takeoff)

airplane routing

departureairport

arrivalairport

intermediate air-trafficcontrol centers

airplane routing airplane routing

baggage (claim

gates (unload)

runway (land)

airplane routing

baggage

gate

takeoff/landing

airplane routing

L h l i l t i


Layers: each layer implements a servicevia its own internal-layer actionsrelying on services provided by layer below

Why layering?Dealing with complex systems:

explicit structure allows identification, relationship of complex system’s pieces

layered reference model for discussionmodularization eases maintenance, updating of system

change of implementation of layer’s service transparent to rest of system


transparent to rest of systeme.g., change in gate procedure doesn’t affect rest of system

layering considered harmful?

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Internet protocol stackapplication: supporting network applications application

FTP, SMTP, HTTPtransport: process-process data transfer

TCP, UDPnetwork: routing of datagrams from source to destination

pp

transport

network

link


IP, routing protocolslink: data transfer between neighboring network elements

PPP, Ethernetphysical: bits “on the wire”

physical

ISO/OSI reference modelpresentation: allow applications to interpret meaning of data, e.g.,

ti i hiapplication

encryption, compression, machine-specific conventionssession: synchronization, checkpointing, recovery of data exchangeInternet stack “missing” these

presentationsession

transportnetwork

link


layers!these services, if needed, must be implemented in applicationneeded?

linkphysical

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sourceapplicationtransportnetwork

linkphysical

HtHn M

segment Ht

datagramHtHnHl M

Encapsulationmessage M

Ht M

Hnframe

destination network

linkphysical

HtHn M

switch


applicationtransportnetwork

linkphysical

HtHnHl MHtHn MHt M

M linkphysical

HtHnHl M HtHn M

router

Part 1: roadmap







37

Network SecurityThe field of network security is about:

how bad guys can attack computer networksy phow we can defend networks against attackshow to design architectures that are immune to attacks

Internet not originally designed with (much) security in mind


original vision: “a group of mutually trusting users attached to a transparent network” ☺Internet protocol designers playing “catch-up”Security considerations in all layers!

Bad guys can put malware into hosts via Internet

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.

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


p

Malware is often self-replicating: from an infected host, seeks entry into other hosts

38

Bad guys can put malware into hosts via Internet

Trojan horseHidden part of some

Worm:infection by passively

otherwise useful softwareToday often on a Web page (Active-X, plugin)

Virusinfection by receiving object (e g e-mail

y p yreceiving object that gets itself executedself- replicating: propagates to other hosts, usersSapphire Worm: aggregate scans/sec

in first 5 minutes of outbreak (CAIDA, UWisc data)


object (e.g., e mail attachment), actively executingself-replicating: propagate itself to other hosts, users

Bad guys can attack servers and network infrastructure

Denial of service (DoS): attackers make resources (server, bandwidth) unavailable to legitimate traffic gby overwhelming resource with bogus traffic

1. select target2. break into hosts

around the network (see botnet)

d k t t d


3. send packets toward target from compromised hosts

target

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The bad guys can sniff packetsPacket 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

Wireshark software used in labs is a (free) packet-sniffer

The bad guys can use false source addresses

IP spoofing: send packet with false source address

A

B

C

src:B dest:A payload


40

The bad guys can record and playback

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

password holder is that user from system point of view

AC


B

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

Part 1: roadmap







41

Internet History

1961: Kleinrock - queueing theory shows

1972:ARPA t bli d t ti

1961-1972: Early packet-switching principles

theory shows effectiveness of packet-switching1964: Baran - packet-switching in military nets1967: ARPAnet conceived by Advanced Research Projects Agency

ARPAnet public demonstrationNCP (Network Control Protocol) first host-host protocol first e-mail programARPAnet has 15 nodes


Projects Agency1969: first ARPAnet node operational

Internet History

1970: ALOHAnet satellite network in Hawaii

Cerf and Kahn’s internetworking principles:

1972-1980: Internetworking, new and proprietary nets

1974: Cerf and Kahn -architecture for interconnecting networks1976: Ethernet at Xerox PARClate70’s: proprietary architectures: DECnet, SNA, XNA

pr nc plesminimalism, autonomy - no internal changes required to interconnect networksbest effort service modelstateless routersdecentralized control

define today’s Internet architecture


XNAlate 70’s: switching fixed length packets (ATM precursor)1979: ARPAnet has 200 nodes

42

Internet History

1983: deployment of TCP/IP

new national networks: C BIT

1980-1990: new protocols, a proliferation of networks

TCP/IP1982: smtp e-mail protocol defined 1983: DNS defined for name-to-IP-address translation

Csnet, BITnet, NSFnet, Minitel100,000 hosts connected to confederation of networks


1985: ftp protocol defined1988: TCP congestion control

Internet History

Early 1990’s: ARPAnet decommissioned

Late 1990’s – 2000’s:

1990, 2000’s: commercialization, the Web, new apps

decommissioned1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995)early 1990s: Web

hypertext [Bush 1945, Nelson 1960’s]HTML HTTP B L

more killer apps: instant messaging, P2P file sharingnetwork security to forefrontest. 50 million host, 100 million+ usersbackbone links running at


HTML, HTTP: Berners-Lee1994: Mosaic, later Netscapelate 1990’s: commercialization of the Web

gGb/s

43

Internet HistoryToday:

~1 billion hostsVoice Video over IPVoice, Video over IPP2P applications: BitTorrent (file sharing) Skype (VoIP), PPLive (video)more applications: YouTube, gamingwireless, mobility


Internet Statistics


44

Internet Statistics

WWW


facebook

Introduction: SummaryCovered a “ton” of material!

Internet overviewh ’ l?

You now have:context, overview,

what’s a protocol?network edge, core, access network

packet-switching versus circuit-switchingInternet structuref l d l

context, o er ew, “feel” of networkingmore depth, detail to follow!


performance: loss, delay, throughputlayering, service modelssecurityhistory

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