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Datakom høsten 20021 Datakommunikasjon høsten 2002 Forelesning 1, 12. august.

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Presentasjon om: "Datakom høsten 20021 Datakommunikasjon høsten 2002 Forelesning 1, 12. august."— Utskrift av presentasjonen:

1 Datakom høsten Datakommunikasjon høsten 2002 Forelesning 1, 12. august

2 Datakom høsten Generell introduksjon zOm foreleser: yBjørn-Arild Kydland, sivilingeniør fra NTH 1984 yAnsatt hos Scandpower Information Technology. yTidligere Telenor og IBM. zOm kurset y13 forelesninger á 3 timer. Siste forelesning Ingen forelesning yRepitisjon y2 obligatoriske oppgaver yForelesningsnotater på norsk og engelsk yHjelpelærer: Ikke bestemt ennå. zPensum yComputer Networking, A top-down Approach Featuring the Internet, Kurose & Ross, Addison-Wesley, ISBN: yNy lærebok i år yForelesningsnotater yPesumliste er ikke klar ennå

3 Datakom høsten Generell intro forts. zInformasjonsutveksling ywwwref hjemmeside ynewsref hjemmeside zKrav til studentene yStill spørsmål - gode spørsmål og dumme spørsmål y3 vekttall er mer enn en full arbeidsdag per uke. zMålsetning yBygge opp et begrepsapparat rundt datakommunikasjon. yVekt på praktiske eksempler knyttet til Internett

4 Datakom høsten Foreløpig pensumliste z

5 Datakom høsten Hva skal dere lære? zNettverkskort zProtokoller zAdressering zApplikasjoner zISDN zLAN zWAN zISP zASP zEthernet zARP zTCP/IP zBro zSvitsj zRuter zFW zDNS zSNMP zSMTP

6 Datakom høsten Tele-/datakommunikasjonsnett PSTN IN - Node Telecom Management System Tactical and Strategic Military Networks Internet LAN GSM

7 Datakom høsten A Communications Model zSource yGenerates data to be transmitted zTransmitter yConverts data into transmittable signals zTransmission System yCarries data zReceiver yConverts received signal into data zDestination yTakes incoming data

8 Datakom høsten “Cool” internet appliances World’s smallest web server IP picture frame

9 Datakom høsten 20029

10 10 Simplified Communications Model - Diagram

11 Datakom høsten Key Communications Tasks zUtnyttelse av transmisjonsmedium zInterface (V.24, RJ 45, V.35 osv) zSignalgenerering zSynkronisering (mellom avsender og mottaker) zFeil deteksjon og korreksjon (av mottaker) zAdressering og ruting zRecovery zMeldingsformatering zSikkerhet (Konfidensialitet, Integritet og Tilgjengelighet) zDrift og vedlikehold (konfigurering, monitorering)

12 Datakom høsten Simplified Data Communications Model

13 Datakom høsten Networking zPoint to point communication not usually practical yDevices are too far apart yLarge set of devices would need impractical number of connections zSolution is a communications network

14 Datakom høsten Simplified Network Model

15 Datakom høsten WAN - Wide Area Networks zStore geografiske områder zBestår av en rekke noder zAlternative teknologier yLinesvitsjing (Circuit switching) yPakkesvitsjing (Packet switching) yFrame relay yAsynchronous Transfer Mode (ATM)

16 Datakom høsten Circuit Switching zDedikert kommunikasjonsvei mellom partene så lenge kommunikasjonen pågår. zEksempel: Telefonnettet

17 Datakom høsten Packet Switching zDatapakker sendes enkeltvis zDatapakkene behøver ikke ta samme vei gjennom nettet zDatapakkene sendes fra node til node mellom avsender og mottaker zBrukes mellom datamaskiner zEksempel: Datapak basert på X.25

18 Datakom høsten Frame Relay zPakksvitsjing systemer har stor overhead for å kompensere for feil zModerne systemer er mer pålitlige zFeil kan håndteres i endesysteme zDet meste av overhead for feilkontroll er tatt vekk zHastigheter fra 64 kbit/s til 2 Mbit/s

19 Datakom høsten Asynchronous Transfer Mode zATM zVidereutvikling av Frame relay zLittle overhead for error control zFixed packet (called cell) length zAnything from 10Mbps to Gbps zConstant data rate using packet switching technique

20 Datakom høsten Integrated Services Digital Network zISDN zLaget for å erstatte PSTN, dvs analog telefoni zPrøveprosjekt i Norge høsten 1989 zBle først populært når det kunne benyttes for å koble seg mot Internett zUtvidet aksess y30 tale/datakanaler, hver på 64 kbit/s y1 signaleringskanal på 64 kbit/s zGrunnaksess y2 tale/datakanaler, hver på 64 kbit/s y1 signaleringskanal på 16 kbit/s

21 Datakom høsten ADSL – Assymetric Digital Subscriber Line  Telenor tilbyr (h astighet inn/ut): y384 / 128 Kb/s laste ned lyd og bilde, samt gjøre flere ting på en gang (kostnad pr. måned 450,- kr) y 704 / 128 Kb/s laste ned filmklipp, programvare og andre store filer (kostnad pr. måned 550,- kr) y 1024 / 256 Kb/s laste ned og sende ut store filer raskt og effektivt (kostnad pr. måned 750,- kr)

22 Datakom høsten LAN - Local Area Networks zEn eller fler bygninger zEies vanligvis av den som henger utstyr på lokalnettet zHøyere datahastigheter enn WAN yEthernet 10 eller 100 Mbit/s zTidligere kun kringasting, dvs alle kan lytte på nettet zNå mer og mer svitsjede systemer + noe bruk av ATM

23 Datakom høsten Protocols zUsed for communications between entities in a system zMust speak the same language zEntities yUser applications y facilities yterminals zSystems yComputer yTerminal yRemote sensor

24 Datakom høsten Key Elements of a Protocol zSyntax yData formats ySignal levels zSemantics yControl information yError handling zTiming ySpeed matching ySequencing

25 Datakom høsten Protocol Architecture zTask of communication broken up into modules zFor example file transfer could use three modules yFile transfer application yCommunication service module yNetwork access module

26 Datakom høsten Simplified File Transfer Architecture

27 Datakom høsten A Three Layer Model zNetwork Access Layer zTransport Layer zApplication Layer

28 Datakom høsten Network Access Layer zExchange of data between the computer and the network zSending computer provides address of destination zMay invoke levels of service zDependent on type of network used (LAN, packet switched etc.)

29 Datakom høsten Transport Layer zReliable data exchange zIndependent of network being used zIndependent of application

30 Datakom høsten Application Layer zSupport for different user applications ze.g. , file transfer

31 Datakom høsten Addressing Requirements zTwo levels of addressing required zEach computer needs unique network address yIP-address zEach application on a (multi-tasking) computer needs a unique address within the computer yThe service access point or SAP yTCP/UDP port nummer: xSNMP port 25 xDNS port 53 xTelnet port 23

32 Datakom høsten Protocol Architectures and Networks

33 Datakom høsten Protocols in Simplified Architecture

34 Datakom høsten Operation of a Protocol Architecture

35 Datakom høsten TCP/IP Protocol Architecture zDeveloped by the US Defense Advanced Research Project Agency (DARPA) for its packet switched network (ARPANET) zUsed by the global Internet zNo official model but a working one. yApplication layer yTransport layer (host to host) yInternet layer yNetwork access layer yPhysical layer

36 Datakom høsten Physical Layer zPhysical interface between data transmission device (e.g. computer) and transmission medium or network zCharacteristics of transmission medium zSignal levels zData rates zetc.

37 Datakom høsten Network Access Layer zExchange of data between end system and network zDestination address provision yIP-address ( ) yhttp address (www.vg.no) zInvoking services like priority yReal time application

38 Datakom høsten Internet Layer (IP) zSystems may be attached to different networks zRouting functions across multiple networks zImplemented in end systems and routers

39 Datakom høsten Transport Layer zReliable delivery of data zOrdering of delivery zTCP or UDP zTCP is connection oriented zUDP is connectionless

40 Datakom høsten Application Layer zSupport for user applications ze.g. http, SMPT, FTP, SNMP

41 Datakom høsten Internetworking Protocols

42 Datakom høsten TCP/IP Protocol Architecture Model

43 Datakom høsten OSI Model zOpen Systems Interconnection zDeveloped by the International Organization for Standardization (ISO) zSeven layers zA theoretical system delivered too late! zTCP/IP is the de facto standard

44 Datakom høsten OSI Layers zApplication zPresentation zSession zTransport zNetwork zData Link zPhysical

45 Datakom høsten OSI Layers (1) zPhysical yPhysical interface between devices xMechanical xElectrical xFunctional xProcedural zData Link yMeans of activating, maintaining and deactivating a reliable link yError detection and control yHigher layers may assume error free transmission

46 Datakom høsten OSI Layers (2) zNetwork yTransport of information yHigher layers do not need to know about underlying technology yNot needed on direct links zTransport yExchange of data between end systems yError free yIn sequence yNo losses yNo duplicates yQuality of service

47 Datakom høsten OSI Layers (3) zSession yControl of dialogues between applications yDialogue discipline yGrouping yRecovery zPresentation yData formats and coding yData compression yEncryption zApplication yMeans for applications to access OSI environment

48 Datakom høsten OSI v TCP/IP

49 Datakom høsten Standards zRequired to allow for interoperability between equipment zAdvantages yEnsures a large market for equipment and software yAllows products from different vendors to communicate zDisadvantages yFreeze technology yMay be multiple standards for the same thing

50 Datakom høsten Standards Organizations zInternet Society yInternet Architecture Board (IAB) yInternet Engineering Task Force (IETF) yInternet Engineering Steering Group (IESG) zISO - International Standard for Organization yJTC – Joint Technical Committee zITU-T (tidligere CCITT) yITU- International Telecommunication Union y14 study groups zATM forum

51 Datakom høsten Further Reading zStallings, W. Data and Computer Communications (6th edition), Prentice Hall 1999 chapter 1 zWeb site for Stallings book ywww.shore.net/~ws/DCC6e.html zWeb sites for IETF, IEEE, ITU-T, ISO zInternet Requests for Comment (RFCs) zUsenet News groups ycomp.dcom.* ycomp.protocols.tcp-ip

52 Datakom høsten Internet History z1961: Kleinrock - queueing theory shows effectiveness of packet-switching z1964: Baran - packet- switching in military nets z1967: ARPAnet conceived by Advanced Research Projects Agency z1969: first ARPAnet node operational z 1972: yARPAnet demonstrated publicly yNCP (Network Control Protocol) first host-host protocol yfirst program yARPAnet has 15 nodes : Early packet-switching principles

53 Datakom høsten Internet History z1970: ALOHAnet satellite network in Hawaii z1973: Metcalfe’s PhD thesis proposes Ethernet z1974: Cerf and Kahn - architecture for interconnecting networks zlate70’s: proprietary architectures: DECnet, SNA, XNA zlate 70’s: switching fixed length packets (ATM precursor) z1979: ARPAnet has 200 nodes Cerf and Kahn’s internetworking principles: yminimalism, autonomy - no internal changes required to interconnect networks ybest effort service model ystateless routers ydecentralized control define today’s Internet architecture : Internetworking, new and proprietary nets

54 Datakom høsten Internet History z1983: deployment of TCP/IP z1982: smtp protocol defined z1983: DNS defined for name-to-IP-address translation z1985: ftp protocol defined z1988: TCP congestion control z new national networks: Csnet, BITnet, NSFnet, Minitel z 100,000 hosts connected to confederation of networks : new protocols, a proliferation of networks

55 Datakom høsten Internet History zEarly 1990’s: ARPAnet decommissioned z1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995) zearly 1990s: WWW yhypertext [Bush 1945, Nelson 1960’s] yHTML, http: Berners-Lee y1994: Mosaic, later Netscape ylate 1990’s: commercialization of the WWW Late 1990’s: z est. 50 million computers on Internet z est. 100 million+ users z backbone links running at 1 Gbps 1990’s: commercialization, the WWW

56 Datakom høsten Introduction: Summary Covered a “ton” of material! zInternet overview zwhat’s a protocol? znetwork edge, core, access network ypacket-switching versus circuit-switching zperformance: loss, delay zlayering and service models zbackbones, NAPs, ISPs zhistory You now have: z context, overview, “feel” of networking z more depth, detail later in course

57 Datakom høsten Informasjon om IP på maskin ipconfig -all Ethernet adapter Local Area Connection: Connection-specific DNS Suffix. : halden.scandpower.no Description : 3Com EtherLink XL 10/100 PCI or Complete PC Management NIC (3C905C-TX) Physical Address : DA-DD-2E-5E DHCP Enabled : No IP Address : Subnet Mask : Default Gateway : DNS Servers :

58 Datakom høsten ARP - Address Resolution Protocol arp -a Interface: on Interface 0x2 Internet Address Physical Address Type b0-3d dynamic a dynamic da-4f-31-8c dynamic a-48 dynamic a-fe dynamic c-8e dynamic fe-29 dynamic

59 Datakom høsten std. ruter Stor ruter Ruter med switsj Cisco5300 Server switch firewall eksempel på utstyrl nettverk


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