Computer Networking: Introduction 1-PDF

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. Computer They obviously represent a lot of work on our part. In return for use, we only ask the following: 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!) Down Approach  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. 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  more depth, net, physical media detail later in  network core: packet/circuit course switching, Internet structure  approach:  performance: loss, delay, use Internet throughput  security as example  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  billions of connected mobile network server computing devices: hosts = end systems global ISP wireless laptop running network apps smartphone home  communication network regional ISP wireless links links fiber, copper, wired links radio, satellite transmission rate: bandwidth  packet switches: router forward packets institutional (chunks of data) network routers and switches 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 home e.g., TCP, IP, HTTP, Skype, network regional ISP 802.11  Internet standards RFC: Request for comments IETF: Internet Engineering Task Force institutional network Introductio 1-6 n What’s the Internet: a service view mobile network  infrastructure that provides services to global ISP applications: 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 Introductio 1-7 n What’s a protocol? human protocols: network protocols:  “what’s the time?”  machines rather  “I have a question” than humans  introductions  all communication activity in Internet governed by … specific messages protocols sent … specific actions protocols define format, taken when messages received, order of messages or other events sent and received among network entities, and actions taken on message 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 servers often in data centers global ISP home  access networks, network regional ISP physical media: wired, wireless communication links  network core: interconnected routers institutional network of network networks 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 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 equency division multiplexing: different channels transmitte 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 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, operator, 10’s km 54, 450 Mbps  between 1 and 10 Mbps transmission rate  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 transmission rate R 2 1 link transmission rate, R: link transmission rate aka link capacity, aka host 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 twisted pair (TP)  physical link: what lies  two insulated copper between transmitter & wires receiver Category 5: 100 Mbps,  guided media: 1 Gbps Ethernet Category 6: 10Gbps signals propagate in solid 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 conductors light pulses, each pulse  bidirectional a bit  broadband:  high-speed operation: multiple channels on high-speed point-to-point cable transmission (e.g., 10’s- HFC 100’s Gbps transmission rate)  low error rate: repeaters spaced far apart immune to electromagnetic noise Introduction 1-21 Physical media: radio  signal carried in radio link types: electromagnetic  terrestrial microwave spectrum e.g. up to 45 Mbps  no physical “wire” channels  bidirectional  LAN (e.g., WiFi)  propagation 54 Mbps environment effects:  wide-area (e.g., cellular) reflection 4G cellular: ~ 10 Mbps obstruction by  satellite Kbps to 45Mbps channel (or objects multiple smaller channels) interference 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 321 source destination R bps R bps  takes L/R seconds to one-hop numerical transmit (push out) L- example: bit packet into link at R  L = 7.5 Mbits bps  R = 1.5 Mbps  store and forward:  one-hop entire packet must transmission delay = arrive at router before 5 sec  it end-end can be delay = 2L/R transmitted (assuming on next linkzero more on delay shortly … propagation delay) 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 forwarding: move taken by packets packets from router’s  routing algorithms input to appropriate router output routing algorithm local forwarding table header value output link 0100 3 1 0101 2 0111 2 3 2 1001 1 11 01 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 Q: what happens if > 35 users ? at same time is less than.0004 * * Check out the online interactive exercises for more examples: h ttp://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 access net … 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 access net … net access access net … … net access access net net connecting each access ISP … … to each other directly doesn’t … access access … net scale: O(N2) connections. net access net access net access net access … … … net access access net access net net 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 access net … 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 access net … 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 Internet exchange point access access … access net net … 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 peering link 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 access net … 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 access net … 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 IX IX IX P P P 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 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  check bit errors delay  determine output link  time waiting at  typically < msec output link for transmission  depends on Introduction 1-44 Four sources of packet delay transmission A propagation B nodal processing queueing dnodal = dproc + dqueue + dtrans + dprop dtrans: transmission dprop: propagation delay: delay:  d: length of physical link  L: packet length (bits)  s: propagation speed dtrans and  R: link bandwidth dprop (bps) (~2x108 m/sec)  dtrans = L/R very different  dprop = d/s * Check out the online interactive exercises for more examples: h ttp://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” 100 km/hr entire caravan  toll booth takes 12 sec to through toll booth onto highway = service car (bit 12*10 = 120 sec transmission time)  time for last car to  car ~ bit; caravan ~ propagate from 1st packet to 2nd toll both:  Q: How long until 100km/(100km/hr)= caravan is lined up 1 hr  A: 62 minutes before 2nd toll booth? 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 delay (bps)  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, with server sends link capacity pipe that can carry link capacity pipe that can carry file ofbits F bits fluid at rate Rs bits/sec fluid at rate Rc bits/sec to(fluid) send into to client pipe 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 onlink end-end path that constrains end-end throughput Introduction 1-53 Throughput: Internet scenario  per-connection end-end Rs throughput: Rs Rs min(Rc,Rs,R/10)  in practice: Rc or R Rs is often bottleneck 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: is there any hope of  routers organizing structure of  links of various network? media  applications …. or at least our discussion of  protocols networks?  hardware, 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: routing of datagrams network from source to destination IP, routing protocols link  link: data transfer between neighboring network elements physical 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, e.g., application encryption, compression, presentation machine-specific conventions session  session: synchronization, checkpointing, recovery of transport data exchange network  Internet stack “missing” these layers! link these services, if needed, must be implemented in physical application needed? Introduction 1-61  source Encapsulatio message segment Ht M M application transport n 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 ARPAnet public demo shows effectiveness NCP (Network Control of packet-switching Protocol) first host-host  1964: Baran - protocol packet-switching in first e-mail program military nets ARPAnet has 15 nodes  1967: ARPAnet 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 architecture for principles: interconnecting networks minimalism, autonomy -  1976: Ethernet at Xerox PARC no internal changes required to interconnect  late70’s: proprietary networks architectures: DECnet, SNA, best effort service model XNA stateless routers  late 70’s: switching fixed decentralized control length packets (ATM define today’s Internet 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 TCP/IP networks: CSnet,  1982: smtp e-mail BITnet, NSFnet, protocol defined Minitel  1983: DNS defined  100,000 hosts for name-to-IP- connected to address translation confederation of  1985: ftp protocol networks 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:  1991: NSF lifts restrictions on instant messaging, commercial use of NSFnet (decommissioned, 1995) P2P file sharing  early 1990s: Web  network security to hypertext [Bush 1945, forefront Nelson 1960’s]  est. 50 million host, HTML, HTTP: Berners-Lee 100 million+ users 1994: Mosaic, later  backbone links Netscape running at Gbps 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 you now have: material!  context, overview,  Internet overview “feel” of networking  what’s a protocol?  more depth, detail  network edge, core, to follow! access network 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) capture copy of all Network (IP) Ethernet Link (Ethernet) (pcap) frames sent/receive Physical d