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University of British Columbia CICS 515 (Part 1) Internet Computing Lecture 1 - Overview Instructor: Dr. Son T. Vuong Email: [email protected] May 8, 2012 The World Connected Introduction Information and Organization Instructor: Dr. Son Vuong ► Email: [email protected] ► Office Hours: T, Th: 1:00-2:00pm (CS 329) TA: ► Jonatan Schroeder ► Shahed Alam [email protected] [email protected] Lectures: T, Th: 11am-1 pm in DMP 110 Lab: Th: 2-4 pm (CS 045/051) Introduction 1-2 Text and Workload Text: Computer Networking: A Top Down Approach Featuring the Internet, 6th edition. Jim Kurose, Keith Ross. Addison-Wesley, April 2012. Course Load: ►2 Projects/Asgmts (20%) ► 2 Quizzes (10%) ► Midterm (25%) ► Final exam (45%) ► Bonus for class participation, BlueCT + Peerwise (4%) i Late penalty: 5*2 %, 0< i =< 3 (i = # days late) Website: www.icics.ubc.ca/~cics515 Vista: http://www.vista.ubc.ca/ (id=pwd=CWL) Introduction 1-3 Revised CISC 515 Outline (Tentative) 1. 2. 3. 4. 5. 6. 7. 8. (T - 08/5) Overview (Chapter 1) P1 (Th - 10/5) Application Layer (The Web and HTTP) (Ch 2) (T - 15/5) WebCache and Transport Layer (Ch 3) (Th - 17/5) Transport Layer (Ch 3) (T - 22/5) Transport Layer (TCP) (Ch 3) Quiz1 (Th - 24/5) TCP Congestion (P1) P2 (T-29/5) IP (Ch 4) IPv6 (Ch 4) Midterm (Th - 31/6) Other Protocols (ICMP, DHCP, DNS), Routing (RIP, OSPF) (Ch 4) 9. (T - 05/6) Routing (RIP, OSPF, BGP) (Ch 4) 10. (Th- 07/6) Data Link protocols (Ethernet) (Ch 5) (P2) 11. (T- 12/6) Wireless Networks (WiFi) (Ch 6) Quiz2 12. (Th-14/6) Review 13. (F-15/6) Final Exam Introduction 1-4 Chapter 1: Introduction Our goal: Overview: get context, what’s the Internet overview, “feel” of networking more depth, detail later in course approach: ► descriptive ► use Internet as example what’s a protocol? network edge network core access net, physical media Internet/ISP structure performance: loss, delay protocol layers, service models history Introduction 1-5 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 Protocol layers, service models 1.7 Delay & loss in packet-switched networks 1.8 History Introduction 1-6 What’s 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 1-7 “Cool” internet appliances IP picture frame http://www.ceiva.com/ Web-enabled toaster+weather forecaster World’s smallest web server http://www-ccs.cs.umass.edu/~shri/iPic.html Introduction 1-8 What’s 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 1-9 What’s 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 1-10 Uses of Internet • • • • Business Applications Home Applications Mobile Users Social Issues Introduction 1-11 Business Applications of Networks A network with two clients and one server. Introduction 1-12 Business Applications of Networks (2) The client-server model involves requests and replies. Introduction 1-13 Home Network Applications Access to remote information Person-to-person communication Interactive entertainment Electronic commerce Introduction 1-14 Home Network Applications (2) In peer-to-peer system there are no fixed clients and servers. Introduction 1-15 Home Network Applications (3) Some forms of e-commerce. Introduction 1-16 Mobile Network Users Combinations of wireless networks and mobile computing. Introduction 1-17 Classification of Networks Classification of interconnected processors by scale. Introduction 1-18 Example Networks The Internet Connection-Oriented Networks: X.25, Frame Relay, and ATM Ethernet Wireless LANs: 802:11 (WiFi) Introduction 1-19 Network Perspective Network users: services that their applications need, e.g., guarantee that each message it sends will be delivered without error within a certain amount of time Network designers: cost-effective design e.g., that network resources are efficiently utilized and fairly allocated to different users Network providers: system that is easy to administer and manage e.g., that faults can be easily isolated and it is easy to account for usage Introduction 1-20 Connectivity Building Blocks ► links: coax cable, optical fiber... ► nodes: general-purpose workstations... Direct Links ► point-to-point ► multiple access Introduction 1-21 Switched Networks A network can be defined recursively as: ► two or more nodes connected by a physical link, ► or by two or more networks connected by one or more nodes Internetworks Internet vs internet Introduction 1-22 A closer look at network structure: network edge: applications and hosts network core: ► routers ► network of networks access networks, physical media: communication links Introduction 1-23 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 Protocol layers, service models 1.7 Delay & loss in packet-switched networks 1.8 History Introduction 1-24 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 1-25 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 ► Internet’s connectionoriented service TCP service [RFC 793] reliable, in-order byte- stream data transfer ► loss: acknowledgements and retransmissions flow control: ► sender won’t overwhelm receiver congestion control: ► senders “slow down sending rate” when network congested Introduction 1-26 Network edge: connectionless service Goal: data transfer between end systems ► same as before! UDP - User Datagram Protocol [RFC 768]: Internet’s connectionless service ► unreliable data transfer ► no flow control ► no congestion control App’s using TCP: HTTP (Web), FTP (file transfer), Telnet (remote login), SMTP (email) App’s using UDP: streaming media, teleconferencing, DNS, Internet telephony 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 Protocol layers, service models 1.7 Delay & loss in packet-switched networks 1.8 History Introduction 1-28 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 1-29 Switching Strategies Circuit switching: dedicated circuit; send/receive a bit stream ► original telephone network Packet switching: store-and-forward; send/receive messages (packets) ► Internet Introduction 1-30 Switching Strategies (a) Circuit switching (b) Message switching (c) Packet switching Introduction 1-31 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 1-32 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 1-33 Packet-switching: store-and-forward L R Takes L/R seconds to R 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 = 3x 5 sec = 15 sec Introduction 1-34 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 1-35 Packet Switching: Message Segmenting L R R R R Now assume the message/packets go through 2 additional switches (over the path of 4 switches) What is the total delay to send the message without breaking into packets (i.e. non-pipelining) ? What is the total delay to send the message as 5000 packets (i.e. pipelining) ? Introduction 1-36 Q 1.1 Peer Instruction packet switching Now assume the message/packets go through 2 additional switches (over the path of 4 switches) What is the total delay to send the message as 5000 packets (i.e. pipelining) ? Answer: (A) 25 s (B) 15 s (C) 5.002 s (E) None of the above (D) 5.004 s Introduction 1-37 Q 1.1 Peer Instruction packet switching Now assume the message/packets go through 2 additional switches (over the path of 4 switches) What is the total delay to send the message as 5000 packets (i.e. pipelining) ? Answer: (A) 25 s (B) 15 s (C) 5.002 s (E) None of the above (D) 5.004 s Introduction 1-38 Packet-switched networks: forwarding Goal: move packets through routers from source to destination ► we’ll 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 1-39 Addressing and Routing Address: byte-string that identifies a node ► usually unique Routing: how to forward messages towards the destination node based on its address Types of addresses ► unicast: node-specific ► broadcast: all nodes on the network ► multicast: some subset of nodes on the network Introduction 1-40 Multiplexing Time-Division Multiplexing (TDM) Frequency-Division Multiplexing (FDM) L1 R1 L2 R2 L3 Switch 1 Switch 2 R3 Introduction 1-41 Circuit Switching: FDMA and TDMA Example: FDMA 4 users frequency time TDMA frequency time Introduction 1-42 Time Division Multiplexing (T1 Carrier) The T1 carrier (1.544 Mbps). (1 bit + 24 slots * 8 bits/slot) * 8000 frames/s = 193 bits/frame * 8000 frames/s = 1.544 Mbps Introduction 1-43 Peer Instruction 1.1 – T1 TDM Question How long does it take to send a file of 640,000 bits from host A to host B over a (sub)channel (a circuit) in a T1 TDM based circuit-switched network? ► ► ► Overall T1 TDM carrier capacity is 1.536 Mbps Data transmission uses one of the 24 slots of the T1 carrier 500 msec to establish end-to-end circuit Work it out! (A) 510 ms (B) 1500 ms (C) 2.5 s (D) 10.5 s (E) None of the above Introduction 1-44 1.1 Peer Instruction – T1 TDM Answer How long does it take to send a file of 640,000 bits from host A to host B over a (sub)channel (a circuit) in a T1 TDM based circuit-switched network? ► ► ► Overall TDM channel capacity is 1.536 Mbps (T1: 1.544 Mbps with 8Kbps framing) Data transmission uses one of the 24 slots of the TDM channel 500 msec = 0.5s to establish end-to-end circuit Answer: Each circuit= 1.536Mbps/24 = 64Kbps Tx(file) = 640Kb/64Kbps = 10s plus Tsetup (A) 510 ms (B) 1500 ms (C) 2.5 s (D) 10.5 s (E) None of the above Introduction 1-45 Peer Instruction 1.1 – T1 TDM Question How long does it take to send a file of 640,000 bits from host A to host B over 5 (sub)channels (circuits) in a T1 TDM based circuit-switched network? ► ► ► Overall T1 TDM carrier capacity is 1.536 Mbps Data transmission uses one of the 24 slots of the T1 carrier 500 msec to establish end-to-end circuit Work it out! (A) 510 ms (B) 1500 ms (C) 2.5 s (D) 10.5 s (E) None of the above Introduction 1-46 1.1 Peer Instruction – T1 TDM Answer How long does it take to send a file of 640,000 bits from host A to host B over 5 (sub)channel (circuits) in a T1 TDM based circuit-switched network? ► ► ► Overall TDM channel capacity is 1.536 Mbps (T1: 1.544 Mbps with 8Kbps framing) Data transmission uses one of the 24 slots of the TDM channel 500 msec = 0.5s to establish end-to-end circuit Answer: Each circuit= 1.536Mbps/24 = 64Kbps Tx(file) = 640Kb/(5x64Kbps) = 2s plus Tsetup (A) 510 ms (B) 1500 ms (C) 2.5 s (D) 10.5 s (E) None of the above Introduction 1-47 Statistical Multiplexing (ATDM) On-demand time-division, rather than fixed (STDM) Schedule link on a per-packet basis Packets from different sources interleaved on link Buffer packets that are contending for the link Packet queue may be processed FIFO Buffer (queue) overflow is called congestion ATDM or Concentrator … 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 Protocol layers, service models 1.7 Delay & loss in packet-switched networks 1.8 History Introduction 1-49 Protocols Building blocks of a network architecture Each protocol object has two different interfaces: ► service: operations on this protocol ► peer-to-peer (protocol): messages exchanged with peer Term “protocol” is overloaded ► specification of peer-to-peer interface ► module that implements this interface Introduction 1-50 Interfaces (Protocol and Service) Host 1 High-level object Protocol Host 2 SERVICE interface PROTOCOL Peer-to-peer interface High-level object Protocol Introduction 1-51 What’s a protocol? human protocols: “what’s 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 1-52 What’s 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 <file> time Q: Other human protocols? Introduction 1-53 Internet Architecture Defined by Internet Engineering Task Force (IETF) Hourglass Design Application vs Application Protocol (FTP, HTTP) FTP HTTP NV TFTP UDP TCP TCP IP NET1 NET2 Application UDP IP … NETn Network Introduction 1-54 ISO Architecture End host End host Application Application Presentation Presentation Session Session Transport Transport Network Network Network Network Data link Data link Data link Data link Physical Physical Physical Physical One or more nodes within the network Introduction 1-55 Reference Models The TCP/IP reference model. Introduction 1-56 Layering Use abstractions to hide complexity Abstraction naturally lead to layering Alternative abstractions at each layer Application programs Application programs Process-to-process Request/reply Message stream channel channel Host-to-host connectivity Host-to-host connectivity Hardware Hardware Introduction 1-57 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 1-58 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 application transport network link physical ack data network link physical application transport network link physical data application transport transport network link physical Introduction 1-59 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 1-60 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 Ht M Hn Ht M Hl Hn Ht M application transport network link physical destination application Ht transport Hn Ht network Hl Hn Ht link physical M message M segment M M datagram frame 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 Protocol layers, service models 1.7 Delay & loss in packet-switched networks 1.8 History Introduction 1-62 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 1-63 1.2 Peer Instruction - Packet Error Prob Question Let p be the bit error probability. Assume packet of length L bits. What's the packet error probability in terms of p and L? (A) (B) (C) (D) (E) (1- p) **L 1- p**L 1- p * L 1- (1-p)**L None of the above Introduction 1-64 1.2 Peer Instruction - Packet Error Prob Answer Let p be the bit error probability. Assume packet of length L bits. What's the packet error probability in terms of p and L? (A) (1- p) **L (B) 1- p**L prob (not all bits in error) (C) 1- p * L (D) 1- (1-p)**L (E) None of the above Answer: (D) prob(a bit not in error) = 1-p prob (L bits not in error) = (1-p)**L prob(packet error) = prob (not all bits not in error) = 1- (1-p)**L Introduction 1-65 What Goes Wrong in the Network? Bit-level errors (electrical interference) prob=p Packet-level errors (congestion) = 1-(1-p)f Link and node failures Messages are delayed Messages are delivered out-of-order Third parties eavesdrop The key problem is to fill in the gap between what applications expect and what the underlying technology provides. Introduction 1-66 Four sources of packet delay 1. nodal processing: ► check bit errors ► determine output link 2. queueing ► time waiting at output link for transmission ► depends on congestion level of router transmission A propagation B nodal processing queueing Introduction 1-67 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 1-68 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 1-69 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 1-70 Digression- Simple Queuing Model Queuing system – general properties: Arrival rate: λ = a msg/s Service rate: μ = R/L msg/s Service time: Ts = L/R = ρ / a s/msg Traffic intensity = Utilization factor = ρ = λ / μ = aL / R Little Formula: N = λ T = a T or T = N/a N = Nw + Ns and T = Tw + Ts M/M/1 Queue Model (M/M/1 is Kendall’ notation): Can derive: # in system: N = ρ / (1- ρ) # waiting in queue: Nw = ρ2 / (1- ρ) => Time in system: T = N/a = Ts / (1- ρ) (using Little formula) = Tw + Ts = N Ts + Ts = (N+1) Ts Waiting time: Tw = T – Ts = Ts / (1- ρ) - Ts = (1/ (1- ρ) - 1 )Ts = ρ Ts / (1- ρ) = N Ts Introduction 1-71 “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 1-72 “Real” Internet delays and routes traceroute: gaia.cs.umass.edu to www.eurecom.fr Three delay measements 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 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 reponse (probe lost, router not replying) 18 * * * 19 fantasia.eurecom.fr (193.55.113.142) 132 ms 128 ms 136 ms Introduction 1-73 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 1-74 Performance Metrics Bandwidth (throughput) (a) ► data transmitted per time unit ► link versus end-to-end ► notation KB = 210 bytes (b) 6 Mbps = 10 bits per second 1 second 1 second Latency (delay) ► time to send message from point A to point B ► one-way versus round-trip time (RTT) ► components Latency = Propagation + Transmit + Queue Propagation = Distance / c (c=3, 2.3, 2x10**8 m/s) Transmit = Size / Bandwidth Introduction 1-75 Bandwidth versus Latency Relative importance ► 1-byte: 1ms vs 100ms dominates 1Mbps vs 100Mbps ► 25MB: 1Mbps vs 100Mbps dominates 1ms vs 100ms Infinite bandwidth ► RTT dominates Throughput = TransferSize / TransferTime TransferTime = RTT + TransferSize / Bandwidth ► 1-GB file to 1-Gbps link as 1-MB packet to 1-Mbps link Introduction 1-76 Delay x Bandwidth Product Amount of data “in flight” or “in the pipe” Example: 100ms x 45Mbps = 560KB Delay Bandw idth Introduction 1-77 ITU Main sectors • • • Radiocommunications Telecommunications Standardization Development Classes of Members • • • • National governments Sector members Associate members Regulatory agencies Introduction 1-78 IEEE 802 Standards The 802 working groups. The important ones are marked with *. The ones marked with are hibernating. The one marked with † gave up. Introduction 1-79 Bad Timing The apocalypse of the two elephants. Introduction 1-80 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 Protocol layers, service models 1.7 Delay & loss in packet-switched networks 1.8 History Introduction 1-81 Internet History 1961-1972: Early packet-switching principles 1961: Kleinrock - queueing theory shows effectiveness of packetswitching 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 hosthost protocol first e-mail program ARPAnet has 15 nodes Introduction 1-82 Internet History 1972-1980: Internetworking, new and proprietary nets 1970: ALOHAnet satellite network in Hawaii 1973: Metcalfe’s PhD thesis proposes Ethernet 1974: Cerf and Kahn architecture for interconnecting networks late70’s: proprietary architectures: DECnet, SNA, XNA late 70’s: switching fixed length packets (ATM precursor) 1979: ARPAnet has 200 nodes Cerf and Kahn’s internetworking principles: ► minimalism, autonomy no internal changes required to interconnect networks ► best effort service model ► stateless routers ► decentralized control define today’s Internet architecture Introduction 1-83 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-IPaddress 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 1-84 Internet History 1990, 2000’s: commercialization, the Web, new apps Early 1990’s: ARPAnet decommissioned 1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995) early 1990s: Web ► hypertext [Bush 1945, Nelson 1960’s] ► HTML, HTTP: Berners-Lee ► 1994: Mosaic, later Netscape ► late 1990’s: commercialization of the Web Late 1990’s – 2000’s: more killer apps: instant messaging, peer2peer file sharing (e.g., Naptser) network security to forefront est. 100 million host, 500 million+ users backbone links running at Gbps Introduction 1-85