Introduction Chapter 1: Roadmap

Home , Bandwidth (computing), BITNET, Cable modem, Circuit switching, DECnet, Internetworking

Chapter 1 Chapter 1: Introduction Introduction Our goal: Overview: v get “feel” and v what’s the Internet? terminology v what’s a protocol? v more depth, detail later in course v network edge; hosts, access net, physical media A note on the use of these ppt slides: v approach: We’re making these slides freely available to all (faculty, students, readers). v network core: packet/circuit They’re in PowerPoint form so you can add, modify, and delete slides § use Internet as (including this one) and slide content to suit your needs. They obviously Computer Networking: switching, Internet structure represent a lot of work on our part. In return for use, we only ask the A Top Down Approach , example following: th v v If you use these slides (e.g., in a class) in substantially unaltered form, that 5 edition. performance: loss, delay, you mention their source (after all, we’d like people to use our book!) Jim Kurose, Keith Ross v If you post any slides in substantially unaltered form on a www site, that throughput you note that they are adapted from (or perhaps identical to) our slides, and Addison-Wesley, April note our copyright of this material. 2009. v security

What’s the Internet: “nuts and bolts” Chapter 1: roadmap view PC v millions of connected Mobile network 1.1 What is the Internet? server computing devices: Global ISP 1.2 Network edge wireless hosts = end systems v end systems, access networks, links laptop § running network apps cellular 1.3 Network core handheld Home network v communication links v circuit switching, packet switching, network structure Regional ISP § fiber, copper, 1.4 Delay, loss and throughput in packet-switched access points radio, satellite networks Institutional network wired § transmission 1.5 Protocol layers, service models links rate = 1.6 Networks under attack: security bandwidth 1.7 History v routers: forward router packets (chunks of data) Introduction 1-3 Introduction 1-4

What’s the Internet: “nuts and bolts” What’s the Internet: a service view view v communication v protocols control sending, Mobile network receiving of msgs infrastructure enables Global ISP distributed applications: § e.g., TCP, IP, HTTP, Skype, Ethernet § Web, VoIP, email, games, v Internet: “network of Home network e-commerce, file sharing networks” Regional ISP v communication services § loosely hierarchical provided to apps: § public Internet versus § reliable data delivery private intranet Institutional network from source to v Internet standards destination § RFC: Request for comments § “best § IETF: Internet Engineering effort” (unreliable) Task Force data delivery

Introduction 1-5 Introduction 1-6

1 What’s a protocol? What’s a protocol?

human protocols: network protocols: a human protocol and a computer network protocol: v “what’s the v machines rather than time?” humans Hi v “I have a question” v all communication TCP connection request v introductions activity in Internet Hi TCP connection governed by protocols response Got the … specific msgs sent protocols define format, time? Get http://www.awl.com/kurose-ross … specific actions taken order of msgs sent and 2:00 when msgs received, received among network or other events entities, and actions time taken on msg transmission, receipt Q: Other human protocols? Introduction 1-7 Introduction 1-8

Chapter 1: roadmap A closer look at network structure:

v network edge: 1.1 What is the Internet? applications and 1.2 Network edge v end systems, access networks, links hosts 1.3 Network core v access networks, v circuit switching, packet switching, network structure physical media: 1.4 Delay, loss and throughput in packet-switched wired, wireless networks communication 1.5 Protocol layers, service models links v network core: 1.6 Networks under attack: security § interconnected 1.7 History routers § network of Introduction 1-9 networks Introduction 1-10

The network edge: Access networks and physical media v end systems (hosts): Q: How to connect end § run application programs systems to edge § e.g. Web, email router? § at “edge of network” peer-peer v residential access nets v client/server model v institutional access § client host requests, receives networks (school, service from always-on server company) client/server § e.g. Web browser/server; email v mobile access networks client/server v peer-peer model: Keep in mind: § minimal (or no) use of v bandwidth (bits per dedicated servers second) of access § e.g. Skype, BitTorrent network? Introduction 1-11 v shared or dedicated? Introduction 1-12

2 Dial-up Modem Digital Subscriber Line (DSL)

central Existing phone line: Internet office 0-4KHz phone; 4-50KHz telephone home upstream data; 50KHz-1MHz network Internet phone downstream data

DSLAM home home ISP dial-up PC modem telephone modem (e.g., AOL) splitter network DSL modem central office home PC v uses existing telephony infrastructure § home directly-connected to central office v uses existing telephone infrastructure v up to 56Kbps direct access to router (often less) v up to 1 Mbps upstream (today typically < 256 kbps) v can’t surf, phone at same time: not “always on” v up to 8 Mbps downstream (today typically < 1 Mbps) v dedicated physical line to telephone central office Introduction 1-13 Introduction 1-14

Residential access: cable modems Residential access: cable modems

v uses cable TV infrastructure, rather than telephone infrastructure v HFC: hybrid fiber coax § asymmetric: up to 30Mbps downstream, 2 Mbps upstream v network of cable, fiber attaches homes to ISP router § homes share access to router § unlike DSL, which has dedicated access

Introduction 1-15 Diagram: http://www.cabledatacomnews.com/cmic/diagram.html Introduction 1-16

Cable Network Architecture: Overview Cable Network Architecture: Overview

server(s)

Typically 500 to 5,000 homes

cable headend cable headend

home home cable distribution cable distribution network (simplified) network

Introduction 1-17 Introduction 1-18

3 Cable Network Architecture: Overview Cable Network Architecture: Overview

FDM (more shortly):

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

cable headend cable headend

home home cable distribution cable distribution network (simplified) network

Introduction 1-19 Introduction 1-20

Fiber to the Home Ethernet Internet access

ONT

optical Internet 100 Mbps institutional fibers router to institution’s ONT Ethernet optical switch ISP fiber OLT 100 Mbps

optical 1 Gbps central office splitter

ONT 100 Mbps server v optical links from central office to the home v two competing optical technologies: v typically used in companies, universities, etc § Passive Optical network (PON) v 10 Mbps, 100Mbps, 1Gbps, 10Gbps Ethernet § Active Optical Network (PAN) v today, end systems typically connect into Ethernet v much higher Internet rates; fiber also carries switch television and phone services Introduction 1-21 Introduction 1-22

Wireless access networks Home networks

v shared wireless access Typical home network components: network connects end system v DSL or cable modem to router router v router/firewall/NAT § via base station aka “access v ” Ethernet point base v wireless access point v wireless LANs: station § 802.11b/g (WiFi): 11 or 54 Mbps v wider-area wireless access wireless to/from laptops § provided by telco operator cable router/ cable § ~1Mbps over cellular system modem firewall (EVDO, HSDPA) mobile headend hosts wireless § next up (?): WiMAX (10’s Mbps) access over wide area Ethernet point

Introduction 1-23 Introduction 1-24

4 Physical Media Physical Media: coax, fiber

Twisted Pair (TP) Coaxial cable: Fiber optic cable: v bit: propagates between v two insulated copper v two concentric copper v glass fiber carrying light transmitter/rcvr pairs wires conductors pulses, each pulse a bit v physical link: what lies § Category 3: traditional v bidirectional v high-speed operation: between transmitter & phone wires, 10 Mbps v baseband: § high-speed point-to-point receiver Ethernet § single channel on cable transmission (e.g., § Category 5: ’ ’ v guided media: § 10 s-100 s Gpbs) 100Mbps Ethernet legacy Ethernet § signals propagate in solid v broadband: v low error rate: repeaters media: copper, fiber, coax § multiple channels on spaced far apart ; v unguided media: cable immune to § signals propagate freely, § HFC electromagnetic noise e.g., radio

Introduction 1-25 Introduction 1-26

Physical media: radio Chapter 1: roadmap

v signal carried in Radio link types: electromagnetic v terrestrial microwave 1.1 What is the Internet? spectrum § e.g. up to 45 Mbps channels 1.2 Network edge v end systems, access networks, links v no physical “wire” v LAN (e.g., WiFi) v bidirectional § 11Mbps, 54 Mbps 1.3 Network core v circuit switching, packet switching, network structure v propagation v wide-area (e.g., cellular) environment effects: § 3G cellular: ~ 1 Mbps 1.4 Delay, loss and throughput in packet-switched § reflection v satellite networks § obstruction by objects § Kbps to 45Mbps channel (or 1.5 Protocol layers, service models § interference multiple smaller channels) 1.6 Networks under attack: security § 270 msec end-end delay 1.7 History § geosynchronous versus low altitude

Introduction 1-27 Introduction 1-28

The Network Core Network Core: Circuit Switching

无法显示图像。您的计算机可能因内存不足而无法打开图像，或图像已遭损坏。 v 请重新启动计算机，然后再次打开该文件。如果仍然显示红色 x ，则可能需要 mesh of interconnected删除此图像，然后重新插入该图像。 end-end resources routers reserved for v the fundamental “call” question: how is data v link bandwidth, switch transferred through capacity net? v dedicated resources: § circuit switching: no sharing dedicated circuit per call: telephone net v circuit-like (guaranteed) § packet-switching: data performance sent thru net in discrete “chunks” v call setup required

Introduction 1-29 Introduction 1-30

5 Network Core: Circuit Switching Circuit Switching: FDM and TDM

Example: network resources v dividing link bandwidth FDM (e.g., bandwidth) into “pieces” 4 users divided into § frequency division “pieces” § time division frequency v pieces allocated to calls v resource piece idle if time not used by owning call TDM (no sharing)

frequency

time Introduction 1-31 Introduction 1-32

Numerical example Network Core: Packet Switching

each end-end data stream resource contention: v How long does it take to send a file of divided into packets v aggregate resource 640,000 bits from host A to host B over a v user A, B packets share demand can exceed circuit-switched network? network resources amount available § all link speeds: 1.536 Mbps v each packet uses full link v congestion: packets § each link uses TDM with 24 slots/sec bandwidth queue, wait for link § 500 msec to establish end-to-end circuit v resources used as needed use v store and forward: packets move one hop Let’s work it out! Bandwidth division into at a time “ ” pieces § node receives complete Dedicated allocation packet before Resource reservation forwarding

Introduction 1-33 Introduction 1-34

Packet Switching: Statistical Multiplexing Packet-switching: store-and-forward

100 Mb/s L C A Ethernet statistical multiplexing R R R

1.5 Mb/s v takes L/R seconds to Example: B transmit (push out) § L = 7.5 Mbits queue of packets packet of L bits on to § R = 1.5 Mbps waiting for output link at R bps link § transmission delay = 15 v store and forward: sec entire packet must

D E arrive at router before it can be v sequence of A & B packets has no fixed timing pattern transmitted on next link § bandwidth shared on demand: statistical multiplexing. more on delay shortly … v delay = 3L/R (assuming v TDM: each host gets same slot in revolving TDM frame. zero propagation Introduction 1-35 delay) Introduction 1-36

6 Packet switching versus circuit switching Packet switching versus circuit switching

Packet switching allows more users to use network! Is packet switching a “slam dunk winner?” v great for bursty data Example: § resource sharing § 1 Mb/s link ….. N § simpler, no call setup § each user: users v excessive congestion: packet delay and loss • 100 kb/s when “active” 1 Mbps link § • active 10% of time protocols needed for reliable data transfer, congestion control v v circuit-switching: Q: How to provide circuit-like behavior? § bandwidth guarantees needed for audio/video apps § 10 users Q: how did we get value 0.0004? v packet switching: § still an unsolved problem (chapter 7) Q: what happens if > 35 users ? § with 35 users, probability > 10 active at same time Q: human analogies of reserved resources (circuit is less than .0004 switching) versus on-demand allocation (packet-switching)? Introduction 1-37 Introduction 1-38

Internet structure: network of networks Internet structure: network of networks v roughly hierarchical “tier-2” ISPs: smaller (often regional) ISPs v at center: small # of well-connected large networks v connect to one or more tier-1 (provider) ISPs § “tier-1” commercial ISPs (e.g., Verizon, Sprint, AT&T, § each tier-1 has many tier-2 customer nets Qwest, Level3), national & international coverage § tier 2 pays tier 1 provider § large content distributors (Google, Akamai, Microsoft) v tier-2 nets sometimes peer directly with each other § treat each other as equals (no charges) (bypassing tier 1) , or at IXP

IXP IXP Tier 2 IXP ISP IXP Tier 2 Tier 2 Tier-1 ISPs & ISP ISP Large Content Large Content Tier 1 ISP Distributor Content Distributor Large Content Tier 1 ISP Large Content (e.g., Akamai) (e.g., Google) Distributor Distributor Distributors, (e.g., Google) interconnect (e.g., Akamai) (peer) privately

… or at Internet Tier 1 ISP Tier 1 ISP Tier 2 Exchange Points Tier 1 ISP Tier 1 ISP ISP Tier 2 IXPs Tier 2 Tier 2 Tier 2 Tier 2 ISP ISP ISP ISP ISP Introduction 1-39 Introduction 1-40

Internet structure: network of networks Internet structure: network of networks

v “Tier-3” ISPs, local ISPs v a packet passes through many networks from source v customer of tier 1 or tier 2 network host to destination host § last hop (“access”) network (closest to end systems)

Tier 2 Tier 2 IXP ISP IXP IXP ISP IXP Tier 2 Tier 2 Tier 2 Tier 2 ISP ISP ISP ISP Large Content Tier 1 ISP Large Content Large Content Tier 1 ISP Large Content Distributor Distributor Distributor Distributor (e.g., Akamai) (e.g., Google) (e.g., Akamai) (e.g., Google)

Tier 2 Tier 1 ISP Tier 1 ISP Tier 2 Tier 1 ISP Tier 1 ISP ISP Tier 2 ISP Tier 2 Tier 2 Tier 2 Tier 2 Tier 2 Tier 2 Tier 2 Tier 2 Tier 2 ISP ISP ISP ISP ISP ISP ISP ISP ISP ISP

Introduction 1-41 Introduction 1-42

7 Chapter 1: roadmap How do loss and delay occur?

packets queue in router buffers 1.1 What is the Internet? v packet arrival rate to link exceeds output link capacity 1.2 Network edge v v end systems, access networks, links packets queue, wait for turn

1.3 Network core packet being transmitted (delay) v circuit switching, packet switching, network structure 1.4 Delay, loss and throughput in packet-switched

networks A 1.5 Protocol layers, service models 1.6 Networks under attack: security B

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

Introduction 1-43 Introduction 1-44

Four sources of packet delay Four sources of packet delay

transmission transmission A A propagation propagation

B B nodal nodal processing queueing processing queueing

dnodal = dproc + dqueue + dtrans + dprop dnodal = dproc + dqueue + dtrans + dprop

dproc: nodal processing dqueue: queueing delay dtrans: transmission delay: dprop: propagation delay: § check bit errors § time waiting at output link § L: packet length (bits) § d: length of physical link § determine output link for transmission § R: link bandwidth (bps) § s: propagation speed in § medium (~2x108 m/sec) § typically < msec depends on congestion level § dtrans = L/R of router dtrans and dprop § dprop = d/s very different Introduction 1-45 Introduction 1-46

Caravan analogy Caravan analogy (more)

100 km 100 km 100 km 100 km

ten-car toll toll ten-car toll toll

caravan booth booth caravan booth booth

v cars “propagate” at § time to “push” entire v cars now “propagate” at 1000 km/hr caravan through toll 100 km/hr v toll booth now takes 1 min to service a car booth onto highway = v toll booth takes 12 sec to 12*10 = 120 sec v Q: Will cars arrive to 2nd booth before all cars service car (transmission § time for last car to serviced at 1st booth? time) propagate from 1st to § A: Yes! After 7 min, 1st car arrives at second booth; three v car~bit; caravan ~ packet 2nd toll both: 100km cars still at 1st booth. /(100km/hr)= 1 hr v § 1st bit of packet can arrive at 2nd router before packet is Q: How long until caravan § A: 62 minutes is lined up before 2nd fully transmitted at 1st router! (see Ethernet applet at AWL Web site toll booth? Introduction 1-47 Introduction 1-48

8 “Real” Internet delays and Queueing delay (revisited) routes

v R: link bandwidth (bps) v What do “real” Internet delay & loss look like? v L: packet length (bits) v Traceroute program: provides delay delay delay v a: average packet measurement from source to router along end-end arrival rate Internet path towards destination. For all i:

average queueing average § sends three packets that will reach router i on path traffic intensity towards destination = La/R § router i will return packets to sender La/R ~ 0 § sender times interval between transmission and reply. v La/R ~ 0: avg. queueing delay small v La/R -> 1: avg. queueing delay large v La/R > 1: more “work” arriving 3 probes 3 probes than can be serviced, average delay infinite! 3 probes

La/R -> 1 Introduction 1-49 Introduction 1-50

“Real” Internet delays and routes Packet loss

traceroute: gaia.cs.umass.edu to www.eurecom.fr v queue (aka buffer) preceding link in buffer has Three delay measurements from gaia.cs.umass.edu to cs-gw.cs.umass.edu finite capacity 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 v packet arriving to full queue dropped (aka lost) 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 v 5 jn1-so7-0-0-0.wae.vbns.net (204.147.136.136) 21 ms 18 ms 18 ms lost packet may be retransmitted by previous 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 node, by source end system, or not at all 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 buffer 11 renater-gw.fr1.fr.geant.net (62.40.103.54) 112 ms 114 ms 112 ms (waiting area) packet being transmitted 12 nio-n2.cssi.renater.fr (193.51.206.13) 111 ms 114 ms 116 ms A 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 * * * B 18 * * * * means no response (probe lost, router not replying) packet arriving to 19 fantasia.eurecom.fr (193.55.113.142) 132 ms 128 ms 136 ms full buffer is lost

Introduction 1-51 Introduction 1-52

Throughput Throughput (more)

v throughput: rate (bits/time unit) at which v Rs < Rc What is average end-end throughput? bits transferred between sender/receiver § instantaneous: rate at given point in time Rs bits/sec Rc bits/sec § average: rate over longer period of time

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

R bits/sec s Rc bits/sec serverserver, sends with bits pipelink that capacity can carry pipelink thatcapacity can carry bottleneck link (fluid)file ofinto F pipebits fluidRs bits/sec at rate Rfluidc bits/sec at rate R bits/sec) to send to client s Rc bits/sec) link on end-end path that constrains end-end throughput

Introduction 1-53 Introduction 1-54

9 Throughput: Internet scenario Chapter 1: roadmap

v per-connection 1.1 What is the Internet? R end-end s 1.2 Network edge R throughput: mi s Rs v end systems, access networks, links 1.3 Network core n(Rc,Rs,R/10) v circuit switching, packet switching, network structure v in practice: R or R R c s 1.4 Delay, loss and throughput in packet-switched is often Rc Rc networks bottleneck Rc 1.5 Protocol layers, service models 1.6 Networks under attack: security 1.7 History 10 connections (fairly) share backbone bottleneck link R bits /sec Introduction 1-55 Introduction 1-56

Protocol “Layers” Organization of air travel

Networks are complex, ticket (purchase) ticket (complain) with many “pieces”: baggage (claim) v hosts baggage (check) Question: v routers Is there any hope of gates (load) gates (unload) v links of various organizing structure of media network? runway takeoff runway landing

v applications airplane routing airplane routing v protocols Or at least our discussion airplane routing v hardware, of networks? software v a series of steps

Introduction 1-57 Introduction 1-58

Layering of airline functionality Why layering? Dealing with complex systems: ticket (purchase) ticket (complain) ticket v explicit structure allows identification, baggage (check) baggage (claim baggage relationship of complex system’s pieces gates (load) gates (unload) gate § layered reference model for discussion runway (takeoff) runway (land) takeoff/landing

airplane routing airplane routing airplane routing airplane routing airplane routing v modularization eases maintenance, updating of

departure intermediate air-traffic arrival system airport control centers airport § change of implementation of layer’s service transparent to rest of system Layers: each layer implements a service § e.g., change in gate procedure doesn’t affect v via its own internal-layer actions rest of system v relying on services provided by layer below v layering considered harmful?

Introduction 1-59 Introduction 1-60

10 Internet protocol stack ISO/OSI reference model

v application: supporting network v presentation: allow applications to applications application interpret meaning of data, e.g., application § FTP, SMTP, HTTP encryption, compression, machine presentation v transport: process-process data transport -specific conventions session transfer v session: synchronization, § TCP, UDP network checkpointing, recovery of data transport exchange v network: routing of datagrams from network source to destination link v Internet stack “missing” these link § IP, routing protocols layers! physical v link: data transfer between § these services, if needed, must physical neighboring network elements be implemented in application § Ethernet, 802.111 (WiFi), PPP § needed? v physical: bits “on the wire” Introduction 1-61 Introduction 1-62

source Encapsulation Chapter 1: roadmap message M application segment Ht M transport

datagram Hn Ht M network frame Hl Hn Ht M link 1.1 What is the Internet? physical 1.2 Network edge link v end systems, access networks, links physical 1.3 Network core switch v circuit switching, packet switching, network structure 1.4 Delay, loss and throughput in packet-switched networks destination Hn Ht M network H H H M link M application l n t Hn Ht M 1.5 Protocol layers, service models physical Ht M transport 1.6 Networks under attack: security Hn Ht M network router 1.7 History Hl Hn Ht M link physical

Introduction 1-63 Introduction 1-64

Network Security Bad guys: put malware into hosts via Internet

v field of network security: v malware can get in host from a virus, worm, or § how bad guys can attack computer networks Trojan horse. § how we can defend networks against attacks § how to design architectures that are immune to v spyware malware can record keystrokes, web sites attacks visited, upload info to collection site.

v Internet not originally designed with v infected host can be enrolled in botnet, used for (much) security in mind spam and DDoS attacks. § original vision: “a group of mutually trusting users attached to a transparent network” J v malware often self-replicating: from one infected § Internet protocol designers playing “catch host, seeks entry into other hosts -up” § security considerations in all layers! Introduction 1-65 Introduction 1-66

11 Bad guys: put malware into hosts via Internet Bad guys: attack server, network infrastructure

Trojan horse worm: Denial of Service (DoS): attackers make resources v hidden part of some v infection by passively receiving (server, bandwidth) unavailable to legitimate traffic otherwise useful software object that gets itself by overwhelming resource with bogus traffic v today often in Web page executed (Active-X, plugin) v self- replicating: propagates to 1. select target virus other hosts, users 2. break into hosts v infection by receiving Sapphire Worm: aggregate scans/sec in first 5 minutes of outbreak (CAIDA, UWisc data) object (e.g., e-mail around the network attachment), actively (see botnet) executing 3. send packets to target v self-replicating: propagate from compromised target itself to other hosts, hosts users

Introduction 1-67 Introduction 1-68

The bad guys can sniff packets The bad guys can use false source addresses Packet sniffing: IP spoofing: send packet with false source address v broadcast media (shared Ethernet, wireless) v promiscuous network interface reads/records all A C packets (e.g., including passwords!) passing by

A C src:B dest:A payload B

src:B dest:A payload B

v Wireshark software used for end-of-chapter labs is a (free) packet-sniffer

Introduction 1-69 Introduction 1-70

The bad guys can record and playback Chapter 1: roadmap record-and-playback: sniff sensitive info (e.g., password), and use later 1.1 What is the Internet? v password holder is that user from system point of 1.2 Network edge view v end systems, access networks, links 1.3 Network core C v circuit switching, packet switching, network structure A 1.4 Delay, loss and throughput in packet-switched

src:B dest:A user: B; password: foo networks 1.5 Protocol layers, service models B 1.6 Networks under attack: security 1.7 History … lots more on security (throughout, Chapter 8)

Introduction 1-71 Introduction 1-72

12 Internet History Internet History

1961-1972: Early packet-switching principles 1972-1980: Internetworking, new and proprietary nets v 1970: ALOHAnet satellite v 1961: Kleinrock - queueing v 1972: network in Hawaii Cerf and Kahn’s theory shows § ARPAnet public demonstration v internetworking principles: effectiveness of packet 1974: Cerf and Kahn - § NCP (Network Control Protocol) architecture for -switching § minimalism, autonomy - first host-host protocol interconnecting networks no internal changes v 1964: Baran - packet § first e-mail program v 1976: Ethernet at Xerox required to -switching in military nets PARC interconnect networks § ARPAnet has 15 nodes v 1967: ARPAnet conceived v late70’s: proprietary § best effort service by Advanced Research architectures: DECnet, SNA, model Projects Agency XNA § stateless routers v 1969: first ARPAnet node v late 70’s: switching fixed § decentralized control operational length packets (ATM define today’s Internet precursor) architecture v 1979: ARPAnet has 200 nodes

Introduction 1-73 Introduction 1-74

Internet History Internet History 1980-1990: new protocols, a proliferation of networks 1990, 2000’s: commercialization, the Web, new apps

v 1983: deployment of v new national networks: v early 1990’s: ARPAnet late 1990’s – 2000’s: decommissioned TCP/IP Csnet, BITnet, v more killer apps: instant v 1991: NSF lifts restrictions on v NSFnet, Minitel messaging, P2P file sharing 1982: smtp e-mail commercial use of NSFnet v network security to protocol defined v 100,000 hosts (decommissioned, 1995) forefront v connected to v early 1990s: Web 1983: DNS defined for v est. 50 million host, 100 name-to-IP-address confederation of § hypertext [Bush 1945, Nelson million+ users 1960’s] translation networks v backbone links running at § HTML, HTTP: Berners-Lee v 1985: ftp protocol Gbps defined § 1994: Mosaic, later Netscape § late 1990’s: v 1988: TCP congestion commercialization of the Web control

Introduction 1-75 Introduction 1-76

Internet History Introduction: Summary

2010: Covered a “ton” of You now have: material! v v ~750 million hosts context, overview, v Internet overview “feel” of v voice, video over IP v what’s a protocol? networking v P2P applications: BitTorrent v network edge, core, access v more depth, detail to (file sharing) Skype (VoIP), network follow! PPLive (video) § packet-switching versus v more applications: YouTube, circuit-switching gaming, Twitter § Internet structure v wireless, mobility v performance: loss, delay, throughput v layering, service models v security

Introduction 1-77 v history Introduction 1-78