Chapter 1 Introduction PDF - Computer Networking

Chapter 1 Introduction A note on the use of these Powerpoint slides: We’re making these slides freely available to all (faculty, students, readers). They’re in PowerPoint form so you see the animations; and can add, modify, and delete slides (including this one) and slide content to suit your needs...

Chapter 1 Introduction A note on the use of these Powerpoint slides: We’re making these slides freely available to all (faculty, students, readers). They’re in PowerPoint form so you see the animations; and 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: Computer Networking: A Top  If you use these slides (e.g., in a class) that you mention their source (after all, we’d like people to use our book!)  If you post any slides 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. Down Approach Thanks and enjoy! JFK/KWR 7th edition Jim Kurose, Keith Ross All material copyright 1996-2016 Pearson/Addison Wesley J.F Kurose and K.W. Ross, All Rights Reserved April 2016 Introduction 1-1 Chapter 1: introduction our goal: overview:  get “feel” and  what’s the Internet? terminology  what’s a protocol?  network edge; hosts, access net,  more depth, detail physical media later in course  network core: packet/circuit  approach: switching, Internet structure use Internet as  performance: loss, delay, throughput example  security  protocol layers, service models  history Introduction 1-2 Chapter 1: 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 1-3 What’s the Internet: “nuts and bolts” view PC mobile network  billions of connected server computing devices: wireless laptop hosts = end systems global ISP smartphone running network apps home  communication links network regional ISP wireless fiber, copper, radio, links satellite wired links transmission rate: bandwidth  packet switches: forward router packets (chunks of data) institutional routers and switches network Introduction 1-4 “Fun” Internet-connected devices Web-enabled toaster + weather forecaster IP picture frame http://www.ceiva.com/ Tweet-a-watt: Slingbox: watch, monitor energy use control cable TV remotely sensorized, bed mattress Internet refrigerator Internet phones Introduction 1-5 What’s the Internet: “nuts and bolts” view mobile network  Internet: “network of networks” Interconnected ISPs global ISP  protocols control sending, receiving of messages e.g., TCP, IP, HTTP, Skype, 802.11 home network  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  infrastructure that provides services to applications: global ISP Web, VoIP, email, games, e- commerce, social nets, … home network  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:  “what’s the time?”  machines rather than  “I have a question” humans  introductions  all communication activity in Internet governed by protocols … specific messages sent … specific actions taken when messages protocols define format, order of received, or other events messages sent and received among network entities, and actions taken on message transmission, receipt Introduction 1-8 What’s a protocol? a human protocol and a computer network 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 Chapter 1: 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:  network edge: mobile network hosts: clients and servers global ISP servers often in data centers home  access networks, physical network regional ISP media: wired, wireless communication links  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?  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 1-12 Access network: digital subscriber line (DSL) central office telephone network DSL splitter modem DSLAM ISP voice, data transmitted at different frequencies over DSL access dedicated line to central office multiplexer  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  < 2.5 Mbps upstream transmission rate (typically < 1 Mbps)  < 24 Mbps downstream transmission rate (typically < 10 Mbps) Introduction 1-13 Access network: 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 multiplexing: different channels transmitted in different frequency bands Introduction 1-14 Access network: cable network cable headend … cable splitter cable modem modem CMTS termination system data, TV transmitted at different frequencies over shared cable ISP distribution network  HFC: hybrid fiber coax asymmetric: up to 30Mbps downstream transmission rate, 2 Mbps upstream transmission rate  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  Access network: 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 (1 Gbps) Introduction 1-16 Enterprise access networks (Ethernet) institutional link to ISP (Internet) institutional router Ethernet institutional mail, switch web servers  typically used in companies, universities, etc.  10 Mbps, 100Mbps, 1Gbps, 10Gbps transmission rates  today, end systems typically connect into Ethernet switch Introduction 1-17 Wireless access networks  shared wireless access network connects end system to router via base station aka “access point” wireless LANs: wide-area wireless access  within building (100 ft.)  provided by telco (cellular)  802.11b/g/n (WiFi): 11, 54, 450 operator, 10’s km Mbps transmission rate  between 1 and 10 Mbps  3G, 4G: LTE to Internet to Internet Introduction 1-18 Host: sends packets of data host sending function:  takes application message  breaks into smaller two packets, chunks, known as packets, L bits each of length L bits  transmits packet into access network at 2 1 transmission rate R R: link transmission rate link transmission rate, host aka link capacity, aka link bandwidth packet time needed to L (bits) transmission = transmit L-bit = delay packet into link R (bits/sec) Introduction 1-19 Physical media  bit: propagates between transmitter/receiver pairs  physical link: what lies twisted pair (TP) between transmitter &  two insulated copper receiver wires  guided media: Category 5: 100 Mbps, 1 Gbps Ethernet signals propagate in solid Category 6: 10Gbps media: copper, fiber, coax  unguided media: signals propagate freely, e.g., radio Introduction 1-20 Physical media: coax, fiber coaxial cable: fiber optic cable:  two concentric copper  glass fiber carrying light conductors pulses, each pulse a bit  bidirectional  high-speed operation:  broadband: high-speed point-to-point multiple channels on cable transmission (e.g., 10’s-100’s Gbps transmission rate) HFC  low error rate: repeaters spaced far apart immune to electromagnetic noise Introduction 1-21 Physical media: radio  signal carried in radio link types: electromagnetic spectrum  terrestrial microwave  no physical “wire” e.g. up to 45 Mbps channels  bidirectional  LAN (e.g., WiFi)  propagation environment 54 Mbps effects:  wide-area (e.g., cellular) reflection 4G cellular: ~ 10 Mbps obstruction by objects  satellite interference Kbps to 45Mbps channel (or multiple smaller channels) 270 msec end-end delay geosynchronous versus low altitude Introduction 1-22 Chapter 1: 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 1-23 The network core  mesh of interconnected routers  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 1-24 Packet-switching: store-and-forward L bits per packet 3 2 1 source destination R bps R bps  takes L/R seconds to transmit one-hop numerical example: (push out) L-bit packet into link at R bps  L = 7.5 Mbits  store and forward: entire  R = 1.5 Mbps packet must arrive at router  one-hop transmission before it can be transmitted delay = 5 sec on next link  end-end delay = 2L/R (assuming zero propagation delay) more on delay shortly … Introduction 1-25 Packet Switching: queueing delay, loss R = 100 Mb/s C A D R = 1.5 Mb/s B queue of packets E waiting for output link queuing and loss:  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 1-26  Two key network-core functions routing: determines source- destination route taken by forwarding: move packets from packets router’s input to appropriate  routing algorithms router output routing algorithm local forwarding table header value output link 0100 3 1 0101 2 0111 2 3 2 1001 1 destination address in arriving packet’s header Introduction 1-27 Alternative core: circuit switching end-end resources allocated to, reserved for “call” between source & dest:  in diagram, each link has four circuits. call gets 2nd circuit in top link and 1st circuit in right link.  dedicated resources: no sharing circuit-like (guaranteed) performance  circuit segment idle if not used by call (no sharing)  commonly used in traditional telephone networks Introduction 1-28 Circuit switching: FDM versus TDM Example: FDM 4 users frequency time TDM frequency time Introduction 1-29 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  circuit-switching: 10 users  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 * * Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose_ross/interactive/ Introduction 1-30 Packet switching versus circuit switching is packet switching a “slam dunk winner?”  great for bursty data resource sharing simpler, no call setup  excessive congestion possible: 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 7) Q: human analogies of reserved resources (circuit switching) versus on-demand allocation (packet-switching)? Introduction 1-31 Internet structure: network of networks  End systems connect to Internet via access ISPs (Internet Service Providers) residential, company and university ISPs  Access ISPs in turn must be interconnected. so that any two hosts can send packets to each other  Resulting network of networks is very complex evolution was driven by economics and national policies  Let’s take a stepwise approach to describe current Internet structure Introduction 1-32 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 Introduction 1-33 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 access to each other directly doesn’t access net scale: O(N2) connections. net access net access net access net access net access access net access net net Introduction 1-34 Internet structure: network of networks Option: connect each access ISP to one 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 net ISP access net access net access net access net access net access access net access net net Introduction 1-35 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 net ISP B access net access net ISP C access net access net access net access access net access net net Introduction 1-36 Internet structure: network of networks But if one global ISP is viable business, there will be competitors …. which must be interconnected access access Internet exchange point net net access net access access net net access IXP access net net ISP A access net IXP ISP B access net access net ISP C access net access peering link net access net access access net access net net Introduction 1-37 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 access IXP access net net ISP A access net IXP ISP B access net access net ISP C access net access net regional net access net access access net access net net Introduction 1-38 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 access IXP access net net ISP A Content provider network access net IXP ISP B access net access net ISP C access net access net regional net access net access access net access net net Introduction 1-39 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  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 1-40 Tier-1 ISP: e.g., Sprint POP: point-of-presence to/from backbone peering … … … … … to/from customers Introduction 1-41 Chapter 1: 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 1-42 How do loss and delay occur? packets queue in router buffers  packet arrival rate to link (temporarily) 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 1-43 Four sources of packet delay transmission A propagation B nodal processing queueing dnodal = dproc + dqueue + dtrans + dprop dproc: nodal processing 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 1-44 Four sources of packet delay transmission A propagation B nodal 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 (~2x108 m/sec)  dtrans = L/R dtrans and dprop  dprop = d/s very different * Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose_ross/interactive/ * Check out the Java applet for an interactive animation on trans vs. prop delay Introduction 1-45 Caravan analogy 100 km 100 km ten-car toll toll caravan booth booth  cars “propagate” at  time to “push” entire 100 km/hr caravan through toll  toll booth takes 12 sec to booth onto highway = service car (bit transmission 12*10 = 120 sec time)  time for last car to  car ~ bit; caravan ~ packet propagate from 1st to  Q: How long until caravan is 2nd toll both: lined up before 2nd toll 100km/(100km/hr)= 1 booth? hr  A: 62 minutes Introduction 1-46 Caravan analogy (more) 100 km 100 km ten-car toll toll caravan booth booth  suppose cars now “propagate” at 1000 km/hr  and suppose toll booth now takes one min to service a car  Q: Will cars arrive to 2nd booth before all cars serviced at first booth? A: Yes! after 7 min, first car arrives at second booth; three cars still at first booth Introduction 1-47 Queueing delay (revisited) average queueing  R: link bandwidth (bps) delay  L: packet length (bits)  a: average packet arrival rate traffic intensity = La/R  La/R ~ 0: avg. queueing delay small La/R ~ 0  La/R -> 1: avg. queueing delay large  La/R > 1: more “work” arriving than can be serviced, average delay infinite! La/R -> 1 * Check online interactive animation on queuing and loss Introduction 1-48 “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 1-49 “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 1-50  Packet loss  queue (aka buffer) preceding link in buffer has finite capacity  packet arriving to full queue dropped (aka lost)  lost packet may be retransmitted by previous node, by source end system, or not at all buffer packet being transmitted A (waiting area) B packet arriving to full buffer is lost * Check out the Java applet for an interactive animation on queuing and loss Introduction 1-51 Throughput  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 server, server withbits sends linkpipe capacity that can carry linkpipe capacity that can carry file of into (fluid) F bitspipe Rs bits/sec fluid at rate Rc bits/sec fluid at rate to send to client Rs bits/sec) Rc bits/sec) Introduction 1-52 Throughput (more)  Rs < Rc What is average end-end throughput? Rs bits/sec Rc bits/sec  Rs > Rc What is average end-end throughput? Rs bits/sec Rc bits/sec bottleneck link link on end-end path that constrains end-end throughput Introduction 1-53 Throughput: Internet scenario  per-connection end- end throughput: Rs min(Rc,Rs,R/10) Rs Rs  in practice: Rc or Rs is often bottleneck R Rc Rc Rc 10 connections (fairly) share backbone bottleneck link R bits/sec * Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose_ross/interactive/ Introduction 1-54 Chapter 1: 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 1-55 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 1-56 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 1-57 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 1-58 Why layering? dealing with complex systems:  explicit structure allows identification, relationship of complex system’s pieces layered reference model for discussion  modularization eases maintenance, updating of system change of implementation of layer’s service transparent to rest of system e.g., change in gate procedure doesn’t affect rest of system  layering considered harmful? Introduction 1-59 Internet protocol stack  application: supporting network applications FTP, SMTP, HTTP application  transport: process-process data transfer transport TCP, UDP network  network: routing of datagrams from source to destination link IP, routing protocols  link: data transfer between physical neighboring network elements Ethernet, 802.111 (WiFi), PPP  physical: bits “on the wire” Introduction 1-60 ISO/OSI reference model  presentation: allow applications to interpret meaning of data, application e.g., encryption, compression, machine-specific conventions presentation  session: synchronization, session checkpointing, recovery of data transport exchange network  Internet stack “missing” these layers! link these services, if needed, must be physical implemented in application needed? Introduction 1-61  message M source application Encapsulation segment Ht M transport datagram Hn Ht M network frame Hl Hn Ht M link physical link physical switch destination Hn Ht M network M application Hl Hn Ht M link Hn Ht M Ht M transport physical Hn Ht M network Hl Hn Ht M link router physical Introduction 1-62 Chapter 1: 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 1-63 Network security  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  Internet not originally designed with (much) security in mind original vision: “a group of mutually trusting users attached to a transparent network”  Internet protocol designers playing “catch-up” security considerations in all layers! Introduction 1-64 Bad guys: put malware into hosts via Internet  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  spyware malware can record keystrokes, web sites visited, upload info to collection site  infected host can be enrolled in botnet, used for spam. DDoS attacks Introduction 1-65 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 1-66 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  wireshark software used for end-of-chapter labs is a (free) packet-sniffer Introduction 1-67 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 1-68 Chapter 1: 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 1-69 Internet history 1961-1972: Early packet-switching principles  1961: Kleinrock -  1972: queueing theory shows ARPAnet public demo effectiveness of packet- NCP (Network Control switching Protocol) first host-host  1964: Baran - packet- protocol switching in military nets first e-mail program  1967: ARPAnet ARPAnet has 15 nodes conceived by Advanced Research Projects Agency  1969: first ARPAnet node operational Introduction 1-70 Internet history 1972-1980: Internetworking, new and proprietary nets  1970: ALOHAnet satellite network in Hawaii Cerf and Kahn’s  1974: Cerf and Kahn - internetworking principles: architecture for interconnecting minimalism, autonomy - no networks internal changes required to  1976: Ethernet at Xerox PARC interconnect networks best effort service model  late70’s: proprietary architectures: DECnet, SNA, stateless routers XNA decentralized control  late 70’s: switching fixed length define today’s Internet packets (ATM precursor) architecture  1979: ARPAnet has 200 nodes Introduction 1-71 Internet history 1980-1990: new protocols, a proliferation of networks  1983: deployment of  new national networks: TCP/IP CSnet, BITnet, NSFnet,  1982: smtp e-mail Minitel protocol defined  100,000 hosts connected  1983: DNS defined for to confederation of name-to-IP-address networks translation  1985: ftp protocol defined  1988: TCP congestion control Introduction 1-72 Internet history 1990, 2000’s: commercialization, the Web, new apps  early 1990’s: ARPAnet late 1990’s – 2000’s: decommissioned  more killer apps: instant  1991: NSF lifts restrictions on messaging, P2P file sharing commercial use of NSFnet  network security to (decommissioned, 1995) forefront  early 1990s: Web  est. 50 million host, 100 hypertext [Bush 1945, million+ users Nelson 1960’s]  backbone links running at HTML, HTTP: Berners-Lee Gbps 1994: Mosaic, later Netscape late 1990’s: commercialization of the Web Introduction 1-73 Internet history 2005-present  ~5B devices attached to Internet (2016) smartphones and tablets  aggressive deployment of broadband access  increasing ubiquity of high-speed wireless access  emergence of online social networks: Facebook: ~ one billion users  service providers (Google, Microsoft) create their own networks bypass Internet, providing “instantaneous” access to search, video content, email, etc.  e-commerce, universities, enterprises running their services in “cloud” (e.g., Amazon EC2) Introduction 1-74 Introduction: summary covered a “ton” of material! you now have:  Internet overview  context, overview, “feel”  what’s a protocol? of networking  network edge, core, access  more depth, detail to network follow! packet-switching versus circuit-switching Internet structure  performance: loss, delay, throughput  layering, service models  security  history Introduction 1-75  Chapter 1 Additional Slides Introduction 1-76  application (www browser, packet email client) analyzer application OS packet Transport (TCP/UDP) Network (IP) capture copy of all Ethernet Link (Ethernet) (pcap) frames sent/receive Physical d