Part I: Introduction - University of Windsor

Part I: Introduction - University of Windsor

Chapter 1 Computer Networks and the Internet A note on the use of these ppt slides: Were making these slides freely available to all (faculty, students, readers). Theyre in PowerPoint form so you can add, modify, and delete slides (including this one) and slide content to suit your needs. They obviously represent a lot of work on our part. In return for use, we only ask the following: If you use these slides (e.g., in a class) in substantially unaltered form, that you mention their source (after all, wed like people to use our book!) If you post any slides in substantially unaltered form on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and note our copyright of this material. Computer Networking: A Top Down Approach Featuring the Internet, 2nd edition. Jim Kurose, Keith Ross Addison-Wesley, July 2002. Thanks and enjoy! JFK/KWR All material copyright 1996-2002 J.F Kurose and K.W. Ross, All Rights Reserved

Introduction 1-1 Chapter 1: Introduction Our goal: Overview: get context, overview, whats the Internet whats a protocol? feel of networking more depth, detail later in course approach: descriptive use Internet as example network edge network core access net, physical media Internet/ISP structure performance: loss, delay protocol layers, service models

history Introduction 1-2 Chapter 1: roadmap 1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Network access and physical media 1.5 Internet structure and ISPs 1.6 Delay & loss in packet-switched networks 1.7 Protocol layers, service models 1.8 History Introduction 1-3 Whats the Internet: nuts and bolts view millions of connected computing devices: hosts, end-systems PCs workstations, servers PDAs phones, toasters

router server mobile local ISP running network apps communication links workstation regional ISP fiber, copper, radio, satellite transmission rate = bandwidth routers: forward packets (chunks of data) company network

Introduction 1-4 Cool internet appliances IP picture frame http://www.ceiva.com/ Web-enabled toaster+weather forecaster Worlds smallest web server http://www-ccs.cs.umass.edu/~shri/iPic.html Introduction 1-5 Whats the Internet: nuts and bolts view protocols control sending, receiving of msgs e.g., TCP, IP, HTTP, FTP, PPP Internet: network of router

server workstation mobile local ISP networks loosely hierarchical public Internet versus private intranet Internet standards RFC: Request for comments IETF: Internet Engineering Task Force regional ISP company network Introduction 1-6

Whats the Internet: a service view communication infrastructure enables distributed applications: Web, email, games, ecommerce, database., voting, file (MP3) sharing communication services provided to apps: connectionless connection-oriented cyberspace [Gibson]: a consensual hallucination experienced daily by billions of operators, in every nation, ...." Introduction 1-7 Whats a protocol?

human protocols: whats the time? I have a question introductions specific msgs sent specific actions taken when msgs received, or other events network protocols: machines rather than humans all communication activity in Internet governed by protocols protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt Introduction 1-8 Whats a protocol? a human protocol and a computer network protocol: Hi

TCP connection req Hi TCP connection response Got the time? Get http://www.awl.com/kurose-ross 2:00 time Q: Other human protocols? Introduction 1-9 A closer look at network structure: network edge: applications a, hosts,

switches network core: routers network of networks access networks, physical media: communication links Introduction 1-10 Chapter 1: roadmap 1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Network access and physical media 1.5 Internet structure and ISPs 1.6 Delay & loss in packet-switched networks 1.7 Protocol layers, service models 1.8 History Introduction

1-11 The network edge: end systems (hosts): run application programs e.g. Web, email at edge of network client/server model client host requests, receives service from always-on server e.g. Web browser/server; email client/server peer-peer model: minimal (or no) use of dedicated servers e.g. Gnutella, KaZaA

Introduction 1-12 Network edge: connection-oriented service Goal: data transfer between end systems handshaking: setup (prepare for) data transfer ahead of time Hello, hello back human protocol set up state in two communicating hosts TCP - Transmission Control Protocol Internets connectionoriented service TCP service [RFC 793] reliable, in-order byte-

stream data transfer loss: acknowledgements and retransmissions flow control: sender wont overwhelm receiver congestion control: senders slow down sending rate when network congested Introduction 1-13 Network edge: connectionless service Goal: data transfer between end systems same as before! UDP - User Datagram

Protocol [RFC 768]: Internets connectionless service unreliable data transfer no flow control no congestion control Apps using TCP: HTTP (Web), FTP (file transfer), Telnet (remote login), SMTP (email) Apps using UDP: streaming media, teleconferencing, DNS, Internet telephony Introduction 1-14 Chapter 1: roadmap 1.1 What is the Internet? 1.2 Network edge

1.3 Network core 1.4 Network access and physical media 1.5 Internet structure and ISPs 1.6 Delay & loss in packet-switched networks 1.7 Protocol layers, service models 1.8 History Introduction 1-15 The Network Core mesh of interconnected routers the fundamental question: how is data transferred through net? circuit switching: dedicated circuit per call: telephone net packet-switching: data sent thru net in discrete chunks Introduction 1-16 Network Core: Circuit Switching

End-end resources reserved for call link bandwidth, switch capacity dedicated resources: no sharing circuit-like (guaranteed) performance call setup required Introduction 1-17 Network Core: Circuit Switching network resources (e.g., bandwidth) divided into pieces pieces allocated to calls resource piece idle if not dividing link bandwidth into pieces frequency division time division

used by owning call (no sharing) Introduction 1-18 Circuit Switching: TDMA and TDMA Example: FDMA 4 users frequency time TDMA frequency time Introduction 1-19 Network Core: Packet Switching each end-end data stream divided into packets

user A, B packets share network resources each packet uses full link bandwidth resources used as needed Bandwidth division into pieces Dedicated allocation Resource reservation resource contention: aggregate resource demand can exceed amount available congestion: packets queue, wait for link use store and forward: packets move one hop at a time transmit over link wait turn at next link Introduction 1-20 Packet Switching: Statistical Multiplexing 10 Mbs Ethernet

A B statistical multiplexing C 1.5 Mbs queue of packets waiting for output link D E Sequence of A & B packets does not have fixed pattern statistical multiplexing. In TDM each host gets same slot in revolving TDM frame. Introduction 1-21 Packet switching versus circuit switching Packet switching allows more users to use network! 1 Mbit link each user:

100 kbps when active active 10% of time circuit-switching: 10 users packet switching: N users 1 Mbps link with 35 users, probability > 10 active less than .0004 Introduction 1-22 Packet switching versus circuit switching Is packet switching a slam dunk winner? Great for bursty data resource sharing simpler, no call setup

Excessive congestion: packet delay and loss protocols needed for reliable data transfer, congestion control Q: How to provide circuit-like behavior? bandwidth guarantees needed for audio/video apps still an unsolved problem (chapter 6) Introduction 1-23 Packet-switching: store-and-forward L R R Takes L/R seconds to transmit (push out) packet of L bits on to link or R bps Entire packet must arrive at router before it can be transmitted on next link: store and forward delay = 3L/R

R Example: L = 7.5 Mbits R = 1.5 Mbps delay = 15 sec Introduction 1-24 Packet Switching: Message Segmenting Now break up the message into 5000 packets Each packet 1,500 bits 1 msec to transmit packet on one link pipelining: each link works in parallel Delay reduced from 15 sec to 5.002 sec Introduction 1-25 Packet-switched networks: forwarding Goal: move packets through routers from source to destination

well study several path selection (i.e. routing)algorithms (chapter 4) datagram network: destination address in packet determines next hop routes may change during session analogy: driving, asking directions virtual circuit network: each packet carries tag (virtual circuit ID), tag determines next hop fixed path determined at call setup time, remains fixed thru call routers maintain per-call state Introduction 1-26 Network Taxonomy Telecommunication networks Circuit-switched networks

FDM TDM Packet-switched networks Networks with VCs Datagram Networks Datagram network is not either connection-oriented or connectionless. Internet provides both connection-oriented (TCP) and connectionless services (UDP) to apps. Introduction 1-27 Chapter 1: roadmap 1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Network access and physical media 1.5 Internet structure and ISPs

1.6 Delay & loss in packet-switched networks 1.7 Protocol layers, service models 1.8 History Introduction 1-28 Access networks and physical media Q: How to connection end systems to edge router? residential access nets institutional access networks (school, company) mobile access networks Keep in mind: bandwidth (bits per second) of access network? shared or dedicated? Introduction 1-29 Residential access: point to point access Dialup via modem up

to 56Kbps direct access to router (often less) Cant surf and phone at same time: cant be always on ADSL: asymmetric digital subscriber line up to 1 Mbps upstream (today typically < 256 kbps) up to 8 Mbps downstream (today typically < 1 Mbps) FDM: 50 kHz - 1 MHz for downstream 4 kHz - 50 kHz for upstream 0 kHz - 4 kHz for ordinary telephone Introduction 1-30 Residential access: cable modems HFC: hybrid fiber coax asymmetric: up to 10Mbps upstream, 1 Mbps downstream network of cable and fiber attaches homes to ISP router shared access to router among home issues: congestion, dimensioning

deployment: available via cable companies, e.g., MediaOne Introduction 1-31 Residential access: cable modems Diagram: http://www.cabledatacomnews.com/cmic/diagram.html Introduction 1-32 Cable Network Architecture: Overview Typically 500 to 5,000 homes cable headend cable distribution network (simplified) home Introduction 1-33

Cable Network Architecture: Overview cable headend cable distribution network (simplified) home Introduction 1-34 Cable Network Architecture: Overview server(s) cable headend cable distribution network home Introduction 1-35 Cable Network Architecture: Overview FDM:

V I D E O V I D E O V I D E O V I D E O V I D E

O V I D E O D A T A D A T A C O N T R O L 1

2 3 4 5 6 7 8 9 Channels cable headend cable distribution network home Introduction 1-36

Company access: local area networks company/univ local area network (LAN) connects end system to edge router Ethernet: shared or dedicated link connects end system and router 10 Mbs, 100Mbps, Gigabit Ethernet deployment: institutions, home LANs happening now LANs: chapter 5 Introduction 1-37 Wireless access networks shared wireless access network connects end system to router via base station aka access point wireless LANs: 802.11b (WiFi): 11 Mbps

wider-area wireless access provided by telco operator 3G ~ 384 kbps Will it happen?? WAP/GPRS in Europe router base station mobile hosts Introduction 1-38 Home networks Typical home network components: ADSL or cable modem router/firewall/NAT Ethernet wireless access

point to/from cable cable modem headend wireless laptops router/ firewall Ethernet (switched) wireless access point Introduction 1-39 Physical Media Bit: propagates between transmitter(tx)/receiver(rx) pairs physical link: what lies

between transmitter & receiver guided media: Twisted Pair (TP) two insulated copper wires Category 3: traditional phone wires, 10 Mbps Ethernet Category 5 TP: 100Mbps Ethernet signals propagate in solid media: copper, fiber, coax unguided media: signals propagate freely, e.g., radio Introduction 1-40

Physical Media: coax, fiber Coaxial cable: two concentric copper conductors bidirectional baseband: single channel on cable legacy Ethernet broadband: multiple channel on cable HFC Fiber optic cable: glass fiber carrying light pulses, each pulse a bit high-speed operation: high-speed point-to-point transmission (e.g., 5 Gps) low error rate: repeaters

spaced far apart ; immune to electromagnetic noise Introduction 1-41 Physical media: radio signal carried in electromagnetic spectrum no physical wire bidirectional propagation environment effects: reflection obstruction by objects interference Radio link types: terrestrial microwave e.g. up to 45 Mbps channels

LAN (e.g., WaveLAN) 2Mbps, 11Mbps wide-area (e.g., cellular) e.g. 3G: hundreds of kbps satellite up to 50Mbps channel (or multiple smaller channels) 270 msec end-end delay geosynchronous versus LEOS Introduction 1-42 Chapter 1: roadmap 1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Network access and physical media 1.5 Internet structure and ISPs

1.6 Delay & loss in packet-switched networks 1.7 Protocol layers, service models 1.8 History Introduction 1-43 Internet structure: network of networks roughly hierarchical at center: tier-1 ISPs (e.g., UUNet, BBN/Genuity, Sprint, AT&T), national/international coverage treat each other as equals Tier-1 providers interconnec t (peer) privately Tier 1 ISP Tier 1 ISP NAP Tier-1 providers also interconnect at public network

access points (NAPs) Tier 1 ISP Introduction 1-44 Tier-1 ISP: e.g., Sprint Sprint US backbone network Introduction 1-45 Internet structure: network of networks Tier-2 ISPs: smaller (often regional) ISPs Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs Tier-2 ISP pays tier-1 ISP for connectivity to rest of Internet tier-2 ISP is customer of tier-1 provider

Tier-2 ISP Tier-2 ISP Tier 1 ISP Tier 1 ISP Tier-2 ISP NAP Tier 1 ISP Tier-2 ISPs also peer privately with each other, interconnect at NAP Tier-2 ISP Tier-2 ISP Introduction 1-46 Internet structure: network of networks Tier-3 ISPs and local ISPs

last hop (access) network (closest to end systems) local ISP Local and tier- 3 ISPs are customers of higher tier ISPs connecting them to rest of Internet Tier 3 ISP local ISP Tier-2 ISP local local ISP ISP Tier-2 ISP Tier 1 ISP

Tier 1 ISP Tier-2 ISP local local ISP ISP NAP Tier 1 ISP Tier-2 ISP local ISP Tier-2 ISP local ISP Introduction 1-47 Internet structure: network of networks a packet passes through many networks! local ISP

Tier 3 ISP local ISP Tier-2 ISP local local ISP ISP Tier-2 ISP Tier 1 ISP Tier 1 ISP Tier-2 ISP local local ISP ISP NAP Tier 1 ISP Tier-2 ISP

local ISP Tier-2 ISP local ISP Introduction 1-48 Chapter 1: roadmap 1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Network access and physical media 1.5 Internet structure and ISPs 1.6 Delay & loss in packet-switched networks 1.7 Protocol layers, service models 1.8 History Introduction 1-49 How do loss and delay occur? packets queue in router buffers packet arrival rate to link exceeds output link capacity packets queue, wait for turn

packet being transmitted (delay) A B packets queueing (delay) free (available) buffers: arriving packets dropped (loss) if no free buffers Introduction 1-50 Four sources of packet delay 1. nodal processing: check bit errors determine output link 2. queuing time waiting at output link for transmission depends on congestion level of router transmission A

propagation B nodal processing queueing Introduction 1-51 Delay in packet-switched networks 3. Transmission delay: R=link bandwidth (bps) L=packet length (bits) time to send bits into link = L/R transmission A 4. Propagation delay: d = length of physical link s = propagation speed in medium (~2x108 m/sec) propagation delay = d/s Note: s and R are very different quantities!

propagation B nodal processing queueing Introduction 1-52 Caravan analogy ten-car caravan toll booth Cars propagate at 100 km 100 km/hr Toll booth takes 12 sec to service a car (transmission time)

car~bit; caravan ~ packet Q: How long until caravan is lined up before 2nd toll booth? toll booth 100 km Time to push entire caravan through toll booth onto highway = 12*10 = 120 sec Time for last car to propagate from 1st to 2nd toll both: 100km/(100km/hr)= 1 hr A: 62 minutes Introduction 1-53 Caravan analogy (more) ten-car caravan

toll booth 100 km toll booth 100 km Yes! After 7 min, 1st car at Cars now propagate at 1000 km/hr Toll booth now takes 1 min to service a car Q: Will cars arrive to 2nd booth before all cars serviced at 1st booth? 2nd booth and 3 cars still at 1st booth. 1st bit of packet can arrive at 2nd router before packet is fully transmitted at 1st

router! See Ethernet applet at AWL Web site Introduction 1-54 Nodal delay d nodal d proc d queue d trans d prop dproc = processing delay typically a few microsecs or less dqueue = queuing delay depends on congestion dtrans = transmission delay = L/R, significant for low-speed links dprop = propagation delay

a few microsecs to hundreds of msecs Introduction 1-55 Queueing delay (revisited) R=link bandwidth (bps) L=packet length (bits) a=average packet arrival rate traffic intensity = La/R La/R ~ 0: average queueing delay small La/R -> 1: delays become large La/R > 1: more work arriving than can be serviced, average delay infinite! Introduction 1-56 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 sender times interval between transmission and reply. 3 probes 3 probes 3 probes Introduction 1-57 Real Internet delays and routes traceroute: gaia.cs.umass.edu to www.eurecom.fr Three delay measurements from gaia.cs.umass.edu to cs1 cs-gw (128.119.240.254) 1 ms 1 ms 2 ms gw.cs.umass.edu 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 link 9 de2-1.de1.de.geant.net (62.40.96.129) 109 ms 102 ms 104 ms 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 * * * * means no response (probe lost, router not 18 * * * 19 fantasia.eurecom.fr replying) (193.55.113.142) 132 ms 128 ms 136 ms Introduction 1-58 Trace route to www.uwindsor.ca mobile::ket$tracert.exe www.uwindsor.ca

Tracing route to web4.uwindsor.ca [137.207.90.107] over a maximum of 30 hops: 1 <10 ms <10 ms 10 ms . [192.168.0.1] 2 60 ms 80 ms 71 ms HSE-London-ppp207876.sympatico.ca [64.228.132.1] 3 70 ms 70 ms 220.1]

4 70 ms 70 ms 4.230.235.101] 5 80 ms 80 ms 8.107.130] 6 70 ms 80 ms 7 80 ms 80 ms 8 80 ms 70 ms 9 80 ms 80 ms 10 80 ms 80 ms 11 81 ms 80 ms 12 80 ms 80 ms 13 80 ms 81 ms 14 80 ms 80 ms 70 ms HSE-Sherbrooke-ppp98100.qc.sympatico.ca [64.230. 70 ms core2-windsor12-Gigabite4-0.in.bellnexxia.net [6 70 ms core1-toronto63-pos6-8.in.bellnexxia.net [206.10 80 ms 64.230.242.93 80 ms 206.108.107.142 90 ms 64.230.242.193 80 ms 64.230.242.150 81 ms 154.11.3.25 80 ms 154.11.6.7 100 ms 209.115.145.122 80 ms w126.wednet.on.ca [209.202.75.126] 81 ms restricted.uwindsor.ca [137.207.232.5] Introduction

1-59 www.yahoo.com

Tracing route to www.yahoo.akadns.net [216.109.118.66] over a maximum of 30 hops: 1 2 10 ms <10 ms 10 ms . [192.168.0.1] 70 ms 70 ms 70 ms HSE-London-ppp207876.sympatico.ca [64.228.132.1] 3 70 ms 70 ms 71 ms HSE-Sherbrooke-ppp98100.qc.sympatico.ca [64.230. 220.1] 4 70 ms 70 ms 80 ms core2-windsor12-Gigabite4-0.in.bellnexxia.net [6 4.230.235.101] 5 80 ms 80 ms 70 ms core1-toronto63-pos6-15.in.bellnexxia.net [64.23 0.235.117] 6 71 ms 70 ms 70 ms 64.230.242.97 7 80 ms 91 ms 100 ms 206.108.107.186 8 91 ms 100 ms 90 ms 206.108.103.214 9 90 ms 90 ms 100 ms 206.108.103.198 10 90 ms 100 ms 100 ms 208.173.135.185 11 100 ms 100 ms 90 ms agr1-loopback.NewYork.cw.net [206.24.194.101] 12 90 ms 100 ms 101 ms dcr2-so-6-0-0.NewYork.cw.net [206.24.207.177] 13 100 ms 100 ms 111 ms dcr1-loopback.Washington.cw.net [206.24.226.99] 14 90 ms 110 ms 100 ms bhr1-pos-10-0.Sterling2dc3.cw.net [206.24.238.38 ] 15 320 ms 101 ms 100 ms csr11-ve240.Sterling2dc3.cw.net [216.109.66.82] 16 100 ms 101 ms 100 ms 216.109.75.254

17 90 ms 100 ms 100 ms vl31.bas2-m.dcn.yahoo.com [216.109.120.146] 18 100 ms 100 ms 100 ms p3.www.dcn.yahoo.com [216.109.118.66] Trace complete. Introduction 1-60 Packet loss queue (aka buffer) preceding link in buffer has finite capacity when packet arrives to full queue, packet is dropped (aka lost) lost packet may be retransmitted by previous node, by source end system, or not retransmitted at all Introduction 1-61 Chapter 1: roadmap 1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Network access and physical media 1.5 Internet structure and ISPs

1.6 Delay & loss in packet-switched networks 1.7 Protocol layers, service models 1.8 History Introduction 1-62 Protocol Layers Networks are complex! many pieces: hosts routers links of various media applications protocols hardware, software Question: Is there any hope of organizing structure of network? Or at least our discussion of networks? Introduction 1-63

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 a series of steps Introduction 1-64

Organization of air travel: a different view ticket (purchase) ticket (complain) baggage (check) baggage (claim) gates (load) gates (unload) runway takeoff runway landing airplane routing airplane routing airplane routing Layers: each layer implements a service via its own internal-layer actions relying on services provided by layer below Introduction

1-65 Layered air travel: services Counter-to-counter delivery of person+bags baggage-claim-to-baggage-claim delivery people transfer: loading gate to arrival gate runway-to-runway delivery of plane airplane routing from source to destination Introduction 1-66 Distributed implementation of layer functionality baggage (check) baggage (claim) gates (load) gates (unload) runway takeoff runway landing

airplane routing airplane routing arriving airport ticket (complain) Departing airport ticket (purchase) intermediate air traffic sites airplane routing airplane routing airplane routing Introduction 1-67 Why layering? Dealing with complex systems: explicit structure allows identification, relationship of

complex systems 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 1-68 Internet protocol stack application: supporting network applications FTP, SMTP, STTP transport: host-host data transfer TCP, UDP network: routing of datagrams from source to destination

IP, routing protocols link: data transfer between neighboring network elements PPP, Ethernet application transport network link physical physical: bits on the wire Introduction 1-69 Layering: logical communication Each layer: distributed entities implement layer functions at each node

entities perform actions, exchange messages with peers application transport network link physical application transport network link physical network link physical application transport network link physical application

transport network link physical Introduction 1-70 Layering: logical communication E.g.: transport take data from app add addressing, reliability check info to form datagram send datagram to peer wait for peer to ack receipt analogy: post office data application transport transport network link

physical ack application transport network link physical data network link physical application transport network link physical data application transport transport network link physical

Introduction 1-71 Layering: physical communication data application transport network link physical application transport network link physical network link physical application transport network link physical data

application transport network link physical Introduction 1-72 Protocol layering and data Each layer takes data from above adds header information to create new data unit passes new data unit to layer below source M application Ht M transport network Hn Ht M link Hl HnHt M physical destination application

Ht transport HnHt network Hl HnHt link physical M message M segment M M datagram frame Introduction 1-73 Chapter 1: roadmap 1.1 What is the Internet?

1.2 Network edge 1.3 Network core 1.4 Network access and physical media 1.5 ISPs and Internet backbones 1.6 Delay & loss in packet-switched networks 1.7 Internet structure and ISPs 1.8 History Introduction 1-74 Internet History 1961-1972: Early packet-switching principles 1961: Kleinrock - queueing theory shows effectiveness of packet-switching 1964: Baran - packetswitching in military nets 1967: ARPAnet conceived by Advanced Research Projects Agency 1969: first ARPAnet node operational 1972:

ARPAnet demonstrated publicly NCP (Network Control Protocol) first host-host protocol first e-mail program ARPAnet has 15 nodes Introduction 1-75 Internet History 1972-1980: Internetworking, new and proprietary nets 1970: ALOHAnet satellite network in Hawaii

1973: Metcalfes PhD thesis proposes Ethernet 1974: Cerf and Kahn architecture for interconnecting networks late70s: proprietary architectures: DECnet, SNA, XNA late 70s: switching fixed length packets (ATM precursor) 1979: ARPAnet has 200 nodes Cerf and Kahns internetworking principles: minimalism, autonomy no internal changes required to interconnect networks best effort service model stateless routers decentralized control define todays Internet architecture Introduction 1-76 Internet History 1980-1990: new protocols, a proliferation of networks

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

1-77 Internet History 1990, 2000s: commercialization, the Web, new apps Early 1990s: ARPAnet decommissioned 1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995) early 1990s: Web hypertext [Bush 1945, Nelson 1960s] HTML, HTTP: Berners-Lee 1994: Mosaic, later Netscape late 1990s: commercialization of the Web Late 1990s 2000s: more killer apps: instant messaging, peer2peer file sharing (e.g., Napster) network security to forefront est. 50 million host, 100

million+ users backbone links running at Gbps Introduction 1-78 Introduction: Summary Covered a ton of material! Internet overview whats a protocol? network edge, core, access network packet-switching versus circuit-switching Internet/ISP structure performance: loss, delay layering and service models history You now have: context, overview, feel of networking more depth, detail to follow! Introduction

1-79

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