1. Introduction

Computer Networking: A Top Down Approach th 6 edition Jim Kurose, Keith Ross

Addison-Wesley

March 2012

All material copyright 1996-2012 J.F Kurose and K.W. Ross, All Rights Reserved

Introduction 1-1 1. Introduction Goals: v get “feel” and terminology v defer depth and detail to later in course v understand concepts using the as example

Introduction 1-2 1. Introduction: roadmap 1.1 what is the Internet? 1.2 network edge § end systems, access networks, links 1.3 network core § , circuit switching, network structure 1.4 delay, loss, throughput in networks 1.5 protocol layers 1.6 networks under attack: security 1.7 history

Introduction 1-3 What’s the Internet: “nuts and bolts” view

PC v hosts or end-systems mobile network server § millions of connected computing devices global ISP laptop running network apps home network v communication links regional ISP wireless § fiber, copper, , links satellite with different wired links transmission rates or

v packet switches router v forward packets or institutional chunks of data network

Introduction 1-4 “Fun” internet appliances

Web-enabled toaster + weather forecaster

IP picture frame

Tweet-a-watt: monitor energy use

Slingbox: watch, control cable TV remotely Internet refrigerator InternetInternet phones phones

Introduction 1-5 What’s the Internet: “nuts and bolts” view

mobile network v Internet: “network of networks” § Interconnected ISPs global ISP v protocols control sending, receiving of msgs § e.g., TCP, IP, HTTP, , 802.11 home network v Internet standards regional ISP § RFC: Request for comments § IETF: Internet Engineering Task Force

institutional network

Introduction 1-6 What’s the Internet: a service view

mobile network v Infrastructure that provides services to applications: global ISP § Web, VoIP, email, games, e- commerce, social nets, … home network v provides programming regional ISP interface to apps § hooks that allow sending and receiving app programs to “connect” to Internet § provides service options, analogous to postal service institutional network

Introduction 1-7 What’s a protocol? human protocols: network protocols: v “what’s the time?” v machines rather than v “I have a question” humans v introductions v all communication activity in Internet governed by … specific msgs sent protocols … specific actions taken when msgs received, or protocols define format, order other events of msgs sent and received among network entities, and actions taken on msg transmission, receipt

Introduction 1-8 What’s a protocol? a human protocol and a protocol:

Hi TCP connection request Hi TCP connection response Got the time? Get http://www.awl.com/kurose-ross 2:00 time

Q: other human protocols?

Introduction 1-9 1. Introduction: roadmap 1.1 what is the Internet? 1.2 network edge § end systems, access networks, links 1.3 network core § packet switching, circuit switching, network structure 1.4 delay, loss, throughput in networks 1.5 protocol layers, service models 1.6 networks under attack: security 1.7 history

Introduction 1-10 A closer look at network structure: v network edge: mobile network § hosts: clients and servers global ISP § servers often in data centers

home v network access networks, physical regional ISP media: wired, wireless communication links v network core: § interconnected routers § network of networks institutional network

Introduction 1-11 Access networks and physical media

Q: How to connect end systems to edge router? v residential access nets v institutional access networks (school, company) v mobile access networks keep in mind: v bandwidth (bits per second) of access network? v shared or dedicated?

Introduction 1-12 Access net: (DSL)

central office The image cannot be displayed network

DSL splitter DSLAM

ISP voice, data transmitted at different frequencies over DSL access dedicated line to central office multiplexer

v use existing telephone line to central office DSLAM § data over DSL phone line goes to Internet § voice over DSL phone line goes to telephone net v < 2.5 Mbps upstream transmission rate (typically < 1 Mbps) v < 24 Mbps downstream transmission rate (typically < 10 Mbps)

Introduction 1-13 Access net: cable network

cable headend …

cable splitter modem

C O V V V V V V N I I I I I I D D T D D D D D D A A R E E E E E E T T O O O O O O O A A L

1 2 3 4 5 6 7 8 9 Channels frequency division : different channels transmitted in different frequency bands

Introduction 1-14 Access net: cable network

cable headend …

cable splitter modem CMTS termination system data, TV transmitted at different frequencies over shared cable ISP distribution network v HFC: hybrid fiber coax § asymmetric: up to 30Mbps downstream transmission rate, 2 Mbps upstream transmission rate v network of cable, fiber attaches homes to ISP router § homes share access network to cable headend § unlike DSL, which has dedicated access to central office Introduction 1-15 Fiber to the home (FTTH) v Fully path all the way to the home § e.g., Verizon FIOS, Google § ~30 Mbps to 1Gbps v Active (like switched Ethernet) or passive optical networking as shown below

Introduction 1-16 Access net: home network

wireless devices

to/from headend or central office often combined in single box

cable or DSL modem

wireless access router, firewall, NAT point (54 Mbps) wired Ethernet (100 Mbps)

Introduction 1-17 Enterprise access networks (Ethernet)

institutional link to ISP (Internet)

institutional router

Ethernet institutional mail, switch web servers

v typically used in companies, universities, etc v 10 Mbps, 100Mbps, 1Gbps, 10Gbps transmission rates v end systems typically connect into Ethernet switch possibly through a wireless access point

Introduction 1-18 Wireless access networks v shared wireless access network connects end system to router § via aka “access point” wireless LANs: wide-area mobile access § within building (100 ft) § provided by telco (cellular) § 802.11b/g/n (WiFi): 11, 54,256 operator, 10’s km Mbps transmission rate § between 1 and 20 Mbps § , /LTE

to Internet

to Internet

Introduction 1-19 Host: sends packets of data sending host: v breaks app message into smaller chunks, known as two packets, packets, of length L bits L bits each v transmits packet into access network at transmission rate R 2 1 § aka link capacity or link R: link transmission rate bandwidth host

packet time needed to L (bits) transmission = transmit L-bit = delay packet into link R (bits/sec)

1-20 Physical media v bit: propagates between /receiver pairs v physical link: what lies between transmitter & receiver v guided media: § signals propagate in solid media: copper, fiber, coax v unguided media: § signals propagate freely, e.g., radio

Introduction 1-21 Physical media: , coax, fiber

twisted pair (TP) fiber optic cable: v two insulated copper v glass fiber carrying light wires pulses, each pulse a bit § Category 5: 100 Mbps, 1 Gpbs Ethernet v high-speed operation: § Category 6: 10Gbps § high-speed point-to-point transmission (e.g., 10’s-100’s Gpbs transmission rate) v low error rate: § repeaters spaced far apart § immune to electromagnetic : noise v two concentric copper conductors v broadband: § multiple channels on cable § HFC Introduction 1-22 Physical media: radio

v signal carried in radio link types: electromagnetic spectrum, v terrestrial i.e., no physical “wire” § e.g. up to 45 Mbps channels v LAN (e.g., WiFi) v propagation environment § 11Mbps, 54 Mbps effects: v wide-area (e.g., cellular) § reflection § 3G cellular: ~ few Mbps § obstruction by objects v satellite § interference § Kbps to 45Mbps channel (or multiple smaller channels) § 270 msec end-end delay § geosynchronous versus low earth-orbitting (LEO)

Introduction 1-23 1. Introduction: roadmap

1.1 what is the Internet? 1.2 network edge § end systems, access networks, links 1.3 network core § packet switching, circuit switching, network structure 1.4 delay, loss, throughput in networks 1.5 protocol layers, service models 1.6 networks under attack: security 1.7 history

Introduction 1-24 The network core v mesh of interconnected routers v packet-switching: hosts break application-layer messages into packets § forward packets from one router to the next across links on path from source to destination § each packet transmitted at full link capacity

Introduction 1-25 Packet-switching: store-and-forward

end-end transmission delay = 2L/R

L bits per packet

3 2 1 source desnaon R bps R bps

v takes L/R seconds to transmit (push out) L-bit Example packet into link at R bps • L=1500B v store and forward: entire • R=1.5Mbps packet must arrive at router • Transmission delay = ? before it can be transmitted on next link

Introduction 1-26 Packet Switching: queueing delay, loss

C A R = 100 Mb/s D R = 1.5 Mb/s B queue of packets E waiting for output link

queuing and loss: v If arrival rate (in bits) to link exceeds transmission rate of link for a period of time: § packets will queue, wait to be transmitted on link § packets can be dropped (lost) if memory (buffer) fills up

Introduction 1-27 Two key network-core functions routing: determines source- forwarding: move packets from destination route taken by router’s input to appropriate packets router output § routing algorithms

routing algorithm

local forwarding table header value output link 0100 3 1 0101 2 0111 2 3 2 1001 1

dest address in arriving packet’s header Network Layer 4-28 Alternative core: circuit switching end-end resources allocated to, reserved for “call” between source & dest: v In diagram, each link has four circuits. § call gets 2nd circuit in top link and 1st circuit in right link. v dedicated resources: no sharing § circuit-like (guaranteed) performance v circuit segment idle if not used by call (no sharing) v Commonly used in traditional telephone networks Introduction 1-29 Circuit switching: FDM versus TDM

Example: FDM 4 users

frequency

time TDM

frequency

time

Introduction 1-30 Packet switching versus circuit switching packet switching allows more users to use network!

example: § 1 Mb/s link

….. § each user: N users • 100 kb/s when “active” • active 10% of time 1 Mbps link

v circuit-switching: § 10 users v packet switching: Q: how did we get value 0.0004? § with 35 users, probability > 10 active at same time is less Q: what happens if > 35 users ? than .0004 *

Introduction 1-31 Packet switching versus circuit switching is packet switching a “slam dunk winner?” v great for bursty data § resource sharing § simpler, no call setup v excessive congestion possible: packet delay and loss § protocols needed for reliable data transfer, congestion control v Q: How to provide circuit-like behavior? § bandwidth guarantees needed for audio/video apps § still an unsolved problem (chapter 7)

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

Introduction 1-32 Q: Circuit-switched capacity v Consider a circuit-switched network with N=100 users where each user is active with probability p=0.2 and when active, sends data at a rate R=1Mbps. How much capacity must the network be provisioned with to guarantee service to all users? A. 100 Mbps B. 20 Mbps C. 200 Mbps D. 50 Mbps E. 500 Mbps

Introduction 1-33 Q: Packet-switched utilization v Consider a packet-switched network with N=100 users where each user is active with probability p=0.2 and when active, sends data at a rate R=1Mbps. What is the probability that the are collectively using C=50Mbps of bandwidth? A. Np B. pC/R C. C(N,C/R)pC/R(1-p)N-C/R D. pC/R(1-p)N-C/R E. p/N

Introduction 1-34 Internet structure: network of networks

v End systems connect to Internet via access ISPs (Internet Service Providers) § Residential, company and university ISPs v Access ISPs in turn must be interconnected. v So that any two hosts can send packets to each other v Resulting network of networks is very complex v Evolution was driven by economics and national policies v Let’s take a stepwise approach to describe current Internet structure Internet structure: network of networks

Question: given millions of access ISPs, how to connect them together?

access access … net net … access net access access net net access access net net

…

access access net net

access net access net

access

net

access … … … … net access access net access net net Internet structure: network of networks

Option: connect each access ISP to every other access ISP?

access access … net net … access net access access net net … access access net net connecting each access ISP

…

… … to each other directly doesn’t access access net scale: O(N2) connections. net

access net access net

access

net

access … … … … net access access net access net net Internet structure: network of networks

Option: connect each access ISP to a global transit ISP? Customer and provider ISPs have economic agreement.

access access … net net … access net access access net net access access net net

… global

access access net ISP net

access net access net

access

net

access … … … … net access access net access net net Internet structure: network of networks

But if one global ISP is viable business, there will be competitors ….

access access … net net … access net access access net net access access net net ISP A

…

access access net ISP B net

access ISP C net access net

access

net

access … … … … net access access net access net net Internet structure: network of networks

But if one global ISP is viable business, there will be competitors …. which must be interconnected Internet exchange point access access … net net … access net access access net net IXP access access net net ISP A

…

access IXP access net ISP B net

access ISP C net access net

access peering link

net

access … … … … net access access net access net net Internet structure: network of networks

… and regional networks may arise to connect access nets to ISPS

access access … net net … access net access access net net IXP access access net net ISP A

…

access IXP access net ISP B net

access ISP C net access net

access

net regional net

access … … … … net access access net access net net Internet structure: network of networks … and content provider networks (e.g., Google, Microsoft, Akamai ) may run their own network, to bring services, content close to end users access access … net net … access net access access net net IXP access access net net ISP A

… Content provider network

access IXP access net ISP B net

access ISP B net access net

access

net regional net

access … … … … net access access net access net net Internet structure: network of networks

Tier 1 ISP Tier 1 ISP Google

IXP IXP IXP

Regional ISP Regional ISP

access access access access access access access access ISP ISP ISP ISP ISP ISP ISP ISP v at center: small # of well-connected large networks § “tier-1” commercial ISPs (e.g., Level 3, Sprint, AT&T, NTT), national & international coverage § content provider network (e.g, Google): private network that connects it data centers to Internet, often bypassing tier-1, regional ISPs Introduction 1-43

Tier-1 ISP: e.g., Sprint

POP: point-of-presence

to/from backbone

peering … … … … … to/from customers

Introduction 1-44 1. Introduction: roadmap 1.1 what is the Internet? 1.2 network edge § end systems, access networks, links 1.3 network core § packet switching, circuit switching, network structure 1.4 delay, loss, throughput in networks 1.5 protocol layers, service models 1.6 networks under attack: security 1.7 history

Introduction 1-45 How do loss and delay occur?

packets queue (wait for their turn) in router buffers when packet arrival rate to link exceeds output link capacity

packet being transmitted (delay)

A

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

Introduction 1-46 Four sources of packet delay

transmission A propagation

B processing queueing

dnodal = dproc + dqueue + dtrans + dprop

dproc: processing delay dqueue: queueing delay § check bit errors § time waiting at output link § determine output link for transmission § typically << msec § depends on congestion level of router

Introduction 1-47 Four sources of packet delay

transmission A propagation

B processing queueing

dnodal = dproc + dqueue + dtrans + dprop

dtrans: transmission delay: dprop: propagation delay: § L: packet length (bits) § d: length of physical link § R: link bandwidth (bps) § s: propagation speed in medium (~2x108 m/sec) § dtrans = L/R dtrans and dprop § dprop = d/s very different

Introduction 1-48 Caravan analogy

100 km 100 km

ten-car toll toll caravan booth booth

v cars “propagate” at § time to “push” entire 100 km/hr caravan through toll v toll booth takes 12 sec to booth onto highway = service car (bit transmission 12*10 = 120 sec time) § time for last car to v car~bit; caravan ~ packet propagate from 1st to 2nd toll both: 100km/ v Q: How long until caravan is lined up before 2nd toll (100km/hr)= 1 hr booth? § A: 62 minutes

Introduction 1-49 Caravan analogy (more)

100 km 100 km

ten-car toll toll caravan booth booth

v suppose cars now “propagate” at 1000 km/hr v and suppose toll booth now takes one min to service a car v Q: Will cars arrive to 2nd booth before all cars serviced at first booth?

§ A: Yes! after 7 min, 1st car arrives at second booth; three cars still at 1st booth.

Introduction 1-50 Queueing delay (revisited)

v R: link bandwidth (bps) v L: packet length (bits) delay delay v a: average packet arrival rate

averagequeueing traffic intensity = La/R

v La/R ~ 0: avg. queueing delay small La/R ~ 0 v La/R -> 1: avg. queueing delay large v La/R > 1: more “work” arriving than can be serviced, average delay infinite!

La/R -> 1 Introduction 1-51 “Real” Internet delays and routes

v what do “real” Internet delay & loss look like? v 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 times interval between transmission and reply.

3 probes 3 probes

3 probes

Introduction 1-52 “Real” Internet delays, routes

traceroute: gaia.cs.umass.edu to www.eurecom.fr 3 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 ms 2 border1-rt-fa5-1-0.gw.umass.edu (128.119.3.145) 1 ms 1 ms 2 ms 3 cht-vbns.gw.umass.edu (128.119.3.130) 6 ms 5 ms 5 ms 4 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 ms 7 nycm-wash.abilene.ucaid.edu (198.32.8.46) 22 ms 22 ms 22 ms trans-oceanic 8 62.40.103.253 (62.40.103.253) 104 ms 109 ms 106 ms 9 de2-1.de1.de.geant.net (62.40.96.129) 109 ms 102 ms 104 ms link 10 de.fr1.fr.geant.net (62.40.96.50) 113 ms 121 ms 114 ms 11 renater-gw.fr1.fr.geant.net (62.40.103.54) 112 ms 114 ms 112 ms 12 nio-n2.cssi.renater.fr (193.51.206.13) 111 ms 114 ms 116 ms 13 nice.cssi.renater.fr (195.220.98.102) 123 ms 125 ms 124 ms 14 r3t2-nice.cssi.renater.fr (195.220.98.110) 126 ms 126 ms 124 ms 15 eurecom-valbonne.r3t2.ft.net (193.48.50.54) 135 ms 128 ms 133 ms 16 194.214.211.25 (194.214.211.25) 126 ms 128 ms 126 ms 17 * * * 18 * * * * means no response (probe lost, router not replying) 19 fantasia.eurecom.fr (193.55.113.142) 132 ms 128 ms 136 ms

* Do some traceroutes from exotic countries at www.traceroute.org Introduction 1-53 Delays: Q1 v Propagation delay depends on the size of the packet. True or false? A. True B. False

Introduction 1-54 Delays: Q2 v Which of the following delays is significantly affected by the load in the network? A. Processing delay B. Queuing delay C. Transmission delay D. Propagation delay

Introduction 1-55 Delays: Q3 v Consider a packet that has just arrived at a router. What is a correct order of the delays encountered by the packet until it reaches the next-hop router? A. Processing, queuing, transmission, propagation B. Transmission, processing, propagation, queuing C. Propagation, processing, transmission, queuing D. Queuing, processing, propagation, transmission

Introduction 1-56 Delays: Q4

v Consider two packets P1, P 2 queued at a router R1 at time t0 as shown above. At what time t1 does P1 reach R2? Assume zero processing delay and speed of light is V m/sec.

A. D1/V B. 2L/C1 + D1/V C. L/C1 + D1/V D. 2L/C1 E. L/C1 + 2D1/V Introduction 1-57 Delays: Q5

v Consider two packets P1, P 2 queued at a router R1 at time t0 as shown above. At what time t2 does P2 reach R2? Assume zero processing delay and speed of light is V m/sec.

A. 2L/C1 + D1/V B. 2L/C1 + 2D1/V C. L/C1 + 2D1/V D. 2D1/V E. 2L/C1 Introduction 1-58 Delays: Q6

v Consider two packets P1, P 2 queued at a router R1 at time t0 as shown above. At what time t3 does P1 leave R2? Assume zero processing delay and speed of light is V m/sec.

A. L/C1 + D1/V + L/C2 B. 2L/C1 + 2(D1/V + L/C2) C. 2L/C1 + 2D1/V D. L/C1 + D1/V + D2/V E. L/C1 + D1/V + L/C2 + D2/V Introduction 1-59 Delays: Q7

v Consider two packets P1, P 2 queued at a router R1 at time t0 as shown above. Does P2 experience queuing delay at R2? Assume zero processing delay and speed of light is V m/sec.

Introduction 1-60 Packet loss v queue (aka buffer) preceding link has finite capacity v packet arriving to full queue dropped (aka lost) v lost packet may be retransmitted by previous , by source end system, or not at all

buffer A (waiting area) packet being transmitted

B packet arriving to full buffer is lost

Introduction 1-61 Throughput

v throughput: rate (bits/time unit) at which bits transferred between sender/receiver § instantaneous: rate at given point in time § average: rate over longer period of time

serverserver, sends with bits link pipe capacity that can carry link pipe capacity that can carry (fluid)file of intoF bits pipe Rs bits/secfluid at rate Rc bits/secfluid at rate to send to client Rs bits/sec) Rc bits/sec)

Introduction 1-62 Throughput (more)

v Rs < Rc What is average end-end throughput?

Rs bits/sec Rc bits/sec

v Rs > Rc What is average end-end throughput?

R bits/sec s Rc bits/sec

bottleneck link link on end-end path that constrains end-end throughput

Introduction 1-63 Throughput: Internet scenario

v Per-connection end- end throughput: Rs R min(Rc,Rs,R/k) s Rs v in practice: Rc or Rs is often bottleneck R

Rc Rc

Rc

Client connections (fairly) share

backbone bottleneck link R bits/sec

Introduction 1-64 1. Introduction: roadmap 1.1 what is the Internet? 1.2 network edge § end systems, access networks, links 1.3 network core § packet switching, circuit switching, network structure 1.4 delay, loss, throughput in networks 1.5 protocol layers, service models 1.6 networks under attack: security 1.7 history

Introduction 1-65 Protocol “layers”

Networks are complex, with many “pieces”: § hosts Question: § routers is there any hope of § links of various organizing structure of media network? § applications § protocols …. or at least our § hardware, discussion of networks? software

Introduction 1-66 Organization of air travel

ticket (purchase) ticket (complain)

baggage (check) baggage (claim)

gates (load) gates (unload)

runway takeoff runway landing

airplane routing airplane routing airplane routing

v a series of steps

Introduction 1-67 Layering of airline functionality

ticket (purchase) ticket (complain) ticket

baggage (check) baggage (claim baggage

gates (load) gates (unload) gate

runway (takeoff) runway (land) takeoff/landing

airplane routing airplane routing airplane routing airplane routing airplane routing

departure intermediate air-traffic arrival airport control centers airport

layers: each layer implements a service § via its own internal-layer actions § relying on services provided by layer below

Introduction 1-68 Why layering? dealing with complex systems: v explicit structure allows identification, relationship of complex system’s pieces § layered reference model for discussion § reusable component design v modularization eases maintenance § change of implementation of layer’s service transparent to rest of system, e.g., change in gate procedure doesn’t affect rest of system v layering considered harmful?

Introduction 1-69 Internet protocol stack

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

v transport: process-process data transfer transport

§ TCP, UDP network v network: routing of datagrams from source to destination link § IP, routing protocols

v link: data transfer between physical neighboring network elements § Ethernet, 802.111 (WiFi), PPP v physical: bits “on the wire”

Introduction 1-70 ISO/OSI reference model

v presentation: allow applications to interpret meaning of data, application e.g., encryption, compression, presentation machine-specific conventions v session: synchronization, session

checkpointing, recovery of data transport exchange network v Internet stack “missing” these layers! link

§ these services, if needed, must be physical implemented in application § needed?

Introduction 1-71 source Encapsulation message M application segment Ht M transport

datagram Hn Ht M network frame Hl Hn Ht M link physical link physical

switch

destination Hn Ht M network H H H M link M application l n t Hn Ht M physical Ht M transport

Hn Ht M network router Hl Hn Ht M link physical

Introduction 1-72 1. Introduction: roadmap 1.1 what is the Internet? 1.2 network edge § end systems, access networks, links 1.3 network core § packet switching, circuit switching, network structure 1.4 delay, loss, throughput in networks 1.5 protocol layers, service models 1.6 networks under attack: security 1.7 history

Introduction 1-73 Network security

v 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 v Internet not originally designed with (much) security in mind § original vision: “a group of mutually trusting users attached to a transparent network” J § Internet protocol designers playing “catch-up” § security considerations in all layers!

Introduction 1-74 Bad guys: put malware into hosts via Internet

v malware can get in host from: § virus: self-replicating infection by receiving/executing object (e.g., e-mail attachment) § worm: self-replicating infection by passively receiving object that gets itself executed

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

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

Introduction 1-75 Bad guys: attack server, network infrastructure

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

1. select target 2. break into hosts around the network (see botnet) 3. send packets to target from compromised hosts target

Introduction 1-76 Bad guys can sniff packets packet “sniffing”: § broadcast media (shared ethernet, wireless) § promiscuous network interface reads/records all packets (e.g., including passwords!) passing by

A C

src:B dest:A payload B

v wireshark software used for labs is a (free) packet-sniffer

Introduction 1-77 Bad guys can use fake addresses

IP spoofing: send packet with false source address

A C

src:B dest:A payload B

… lots more on security (throughout, Chapter 8)

Introduction 1-78 1. Introduction: roadmap 1.1 what is the Internet? 1.2 network edge § end systems, access networks, links 1.3 network core § packet switching, circuit switching, network structure 1.4 delay, loss, throughput in networks 1.5 protocol layers, service models 1.6 networks under attack: security 1.7 history

Introduction 1-79 Internet history 1961-1972: Early packet-switching principles

v 1961: Kleinrock - v 1972: queueing theory shows § ARPAnet public demo effectiveness of packet- § NCP (Network Control switching Protocol) first host-host v 1964: Baran - packet- protocol switching in military nets § first e-mail program v 1967: ARPAnet § ARPAnet has 15 nodes conceived by Advanced Research Projects Agency v 1969: first ARPAnet node operational

Introduction 1-80 Internet history 1972-1980: Internetworking, new and proprietary nets v 1970: ALOHAnet satellite network in Hawaii Cerf and Kahn’s v 1974: Cerf and Kahn - internetworking principles: architecture for interconnecting § minimalism, autonomy - no networks internal changes required to interconnect networks v 1976: Ethernet at Xerox PARC § best effort service model v late70’s: proprietary architectures: DECnet, SNA, § stateless routers XNA § decentralized control v late 70’s: switching fixed length define today’s Internet packets (ATM precursor) architecture v 1979: ARPAnet has 200 nodes

Introduction 1-81 Internet history 1980-1990: new protocols, a proliferation of networks

v 1983: deployment of TCP/IP v new national networks: v 1982: SMTP e-mail protocol Csnet, BITnet, NSFnet, v 1983: DNS defined for name-to-IP-address v 100,000 hosts connected translation to confederation of networks v 1985: FTP protocol defined v 1988: TCP congestion control

Introduction 1-82 Internet history 1990, 2000’s: commercialization, the Web, new apps v early 1990’s: ARPAnet late 1990’s – 2000’s: decommissioned v more killer apps: instant v 1991: NSF lifts restrictions on messaging, P2P file sharing commercial use of NSFnet v network security to (decommissioned, 1995) forefront v early 1990s: Web v est. 50 million host, 100 § hypertext [Bush 1945, Nelson million+ users 1960’s] v backbone links running at § HTML, HTTP: Berners-Lee Gbps § 1994: Mosaic, later Netscape § late 1990’s: commercialization of the Web

Introduction 1-83 Internet history

2005-present v ~1 billion traditional hosts (desktops, laptops, tablets) v 4-5 billion phones about a billion of which are data capable v Aggressive deployment of broadband access v Increasing ubiquity of high-speed wireless access v Emergence of online social networks: § Facebook: ~1 billion users v Service providers (Google, Microsoft) create their own networks § Bypass Internet, providing “instantaneous” access to search, email, etc. v E-commerce, universities, enterprises running their services in “cloud” (eg, Amazon EC2)

Introduction 1-84 Introduction: summary

covered a “ton” of material! you now have: v Internet overview v context, overview, “feel” v what’s a protocol? of networking v network edge, core, access v more depth, detail to network follow! § packet-switching versus circuit-switching § Internet structure v performance: loss, delay, throughput v layering, service models v security v history

Introduction 1-85