Dat ak om m unik asjon høst en 2002 Forelesning 1, 12. august Datakom høsten 2002 1
Generell int roduk sjon ] Om foreleser: \ Bjørn-Arild Kydland, sivilingeniør fra NTH 1984 \ Ansatt hos Scandpower Information Technology. \ Tidligere Telenor og I BM. ] Om kurset \ 13 forelesninger á 3 timer. Siste forelesning 11.11. Ingen forelesning 19.08 \ Repitisjon 18.11 \ 2 obligatoriske oppgaver \ Forelesningsnotater på norsk og engelsk \ Hjelpelærer: Ikke bestemt ennå. ] Pensum \ Computer Networking, A top-down Approach Featuring the Internet, Kurose & Ross, Addison-Wesley, ISBN: 0-201-47711-4 \ Ny lærebok i år \ Forelesningsnotater \ Pesumliste er ikke klar ennå Datakom høsten 2002 2
Generell int ro fort s. ] Informasjonsutveksling \ epost bak@scandpower.com \ www ref hjemmeside \ news ref hjemmeside ] Krav til studentene \ Still spørsmål - gode spørsmål og dumme spørsmål \ 3 vekttall er mer enn en full arbeidsdag per uke. ] Målsetning \ Bygge opp et begrepsapparat rundt datakommunikasjon. \ Vekt på praktiske eksempler knyttet til Internett Datakom høsten 2002 3
Foreløpig pensum list e ] Datakom høsten 2002 4
Hva sk al dere læ re? ] Nettverkskort ] Protokoller ] Adressering ] Applikasjoner ] ISDN ] LAN ] WAN ] ISP ] ASP ] Ethernet ] ARP ] TCP/ IP ] Bro ] Svitsj ] Ruter ] FW ] DNS ] SNMP ] SMTP Datakom høsten 2002 5
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A Com m unic at ions Model ] Source \ Generates data to be transmitted ] Transmitter \ Converts data into transmittable signals ] Transmission System \ Carries data ] Receiver \ Converts received signal into data ] Destination \ Takes incoming data Datakom høsten 2002 7
Cool int ernet applianc es IP picture frame http://www.ceiva.com/ World s smallest web server http://www-ccs.cs.umass.edu/~shri/ipic.html Datakom høsten 2002 8
Datakom høsten 2002 9
Sim plified Com m unic at ions Model - Diagram Datakom høsten 2002 10
K ey Com m unic at ions Task s ] Utnyttelse av transmisjonsmedium ] Interface (V.24, RJ 45, V.35 osv) ] Signalgenerering ] Synkronisering (mellom avsender og mottaker) ] Feil deteksjon og korreksjon (av mottaker) ] Adressering og ruting ] Recovery ] Meldingsformatering ] Sikkerhet (Konfidensialitet, Integritet og Tilgjengelighet) ] Drift og vedlikehold (konfigurering, monitorering) Datakom høsten 2002 11
Sim plified Dat a Com m unic at ions Model Datakom høsten 2002 12
Net w ork ing ] Point to point communication not usually practical \ Devices are too far apart \ Large set of devices would need impractical number of connections ] Solution is a communications network Datakom høsten 2002 13
Sim plified Net w ork Model Datakom høsten 2002 14
WAN - Wide Area Net w ork s ] Store geografiske områder ] Består av en rekke noder ] Alternative teknologier \ Linesvitsjing (Circuit switching) \ Pakkesvitsjing (Packet switching) \ Frame relay \ Asynchronous Transfer Mode (ATM) Datakom høsten 2002 15
Circ uit Sw it c hing ] Dedikert kommunikasjonsvei mellom partene så lenge kommunikasjonen pågår. ] Eksempel: Telefonnettet Datakom høsten 2002 16
Pac k et Sw it c hing ] Datapakker sendes enkeltvis ] Datapakkene behøver ikke ta samme vei gjennom nettet ] Datapakkene sendes fra node til node mellom avsender og mottaker ] Brukes mellom datamaskiner ] Eksempel: Datapak basert på X.25 Datakom høsten 2002 17
Fram e Relay ] Pakksvitsjing systemer har stor overhead for å kompensere for feil ] Moderne systemer er mer pålitlige ] Feil kan håndteres i endesysteme ] Det meste av overhead for feilkontroll er tatt vekk ] Hastigheter fra 64 kbit/s til 2 Mbit/s Datakom høsten 2002 18
Async hronous Transfer Mode ] ATM ] Videreutvikling av Frame relay ] Little overhead for error control ] Fixed packet (called cell) length ] Anything from 10Mbps to Gbps ] Constant data rate using packet switching technique Datakom høsten 2002 19
Int egrat ed Servic es Digit al Net w ork ] ISDN ] Laget for å erstatte PSTN, dvs analog telefoni ] Prøveprosjekt i Norge høsten 1989 ] Ble først populæ rt når det kunne benyttes for å koble seg mot Internett ] Utvidet aksess \ 30 tale/datakanaler, hver på 64 kbit/ s \ 1 signaleringskanal på 64 kbit/ s ] Grunnaksess \ 2 tale/ datakanaler, hver på 64 kbit/s \ 1 signaleringskanal på 16 kbit/ s Datakom høsten 2002 20
ADSL Assym et ric Digit al Subsc riber Line ] Telenor tilbyr (hastighet inn/ ut): \ 384 / 128 Kb/ s laste ned lyd og bilde, sam t gjøre flere ting på en gang (kostnad pr. m åned 450,- kr) \ 704 / 128 Kb/ s laste ned film klipp, program vare og andre store filer (kostnad pr. m åned 550,- kr) \ 1024 / 256 Kb/ s laste ned og sende ut store filer raskt og effektivt (kostnad pr. m åned 750,- kr) Datakom høsten 2002 21
LAN - Loc al Area Net w ork s ] En eller fler bygninger ] Eies vanligvis av den som henger utstyr på lokalnettet ] Høyere datahastigheter enn WAN \ Ethernet 10 eller 100 Mbit/s ] Tidligere kun kringasting, dvs alle kan lytte på nettet ] Nå mer og mer svitsjede systemer + noe bruk av ATM Datakom høsten 2002 22
Prot oc ols ] Used for communications between entities in a system ] Must speak the same language ] Entities \ User applications \ e-mail facilities \ terminals ] Systems \ Computer \ Terminal \ Remote sensor Datakom høsten 2002 23
K ey Elem ent s of a Prot oc ol ] Syntax \ Data formats \ Signal levels ] Semantics \ Control information \ Error handling ] Timing \ Speed matching \ Sequencing Datakom høsten 2002 24
Prot oc ol Arc hit ec t ure ] Task of communication broken up into modules ] For example file transfer could use three modules \ File transfer application \ Communication service module \ Network access module Datakom høsten 2002 25
Sim plified File Transfer Arc hit ec t ure Datakom høsten 2002 26
A Three Layer Model ] Network Access Layer ] Transport Layer ] Application Layer Datakom høsten 2002 27
Net w ork Ac c ess Layer ] Exchange of data between the computer and the network ] Sending computer provides address of destination ] May invoke levels of service ] Dependent on type of network used (LAN, packet switched etc.) Datakom høsten 2002 28
Transport Layer ] Reliable data exchange ] Independent of network being used ] Independent of application Datakom høsten 2002 29
Applic at ion Layer ] Support for different user applications ] e.g. e-mail, file transfer Datakom høsten 2002 30
Addressing Requirem ent s ] Two levels of addressing required ] Each computer needs unique network address \ IP-address ] Each application on a (multi-tasking) computer needs a unique address within the computer \ The service access point or SAP \ TCP/ UDP port nummer: [ SNMP port 25 [ DNS port 53 [ Telnet port 23 Datakom høsten 2002 31
Prot oc ol Arc hit ec t ures and Net w ork s Datakom høsten 2002 32
Prot oc ols in Sim plified Arc hit ec t ure Datakom høsten 2002 33
Operat ion of a Prot oc ol Arc hit ec t ure Datakom høsten 2002 34
TCP/IP Prot oc ol Arc hit ec t ure ] Developed by the US Defense Advanced Research Project Agency (DARPA) for its packet switched network (ARPANET) ] Used by the global Internet ] No official model but a working one. \ Application layer \ Transport layer (host to host) \ Internet layer \ Network access layer \ Physical layer Datakom høsten 2002 35
Physic al Layer ] Physical interface between data transmission device (e.g. computer) and transmission medium or network ] Characteristics of transmission medium ] Signal levels ] Data rates ] etc. Datakom høsten 2002 36
Net w ork Ac c ess Layer ] Exchange of data between end system and network ] Destination address provision \ IP-address (193.69.136.8) \ http address (www.vg.no) ] Invoking services like priority \ Real time application Datakom høsten 2002 37
Int ernet Layer (IP) ] Systems may be attached to different networks ] Routing functions across multiple networks ] Implemented in end systems and routers Datakom høsten 2002 38
Transport Layer ] Reliable delivery of data ] Ordering of delivery ] TCP or UDP ] TCP is connection oriented ] UDP is connectionless Datakom høsten 2002 39
Applic at ion Layer ] Support for user applications ] e.g. http, SMPT, FTP, SNMP Datakom høsten 2002 40
Int ernet w ork ing Prot oc ols Datakom høsten 2002 41
TCP/IP Prot oc ol Arc hit ec t ure Model Datakom høsten 2002 42
OSI Model ] Open Systems Interconnection ] Developed by the International Organization for Standardization (ISO) ] Seven layers ] A theoretical system delivered too late! ] TCP/ IP is the de facto standard Datakom høsten 2002 43
OSI Layers ] Application ] Presentation ] Session ] Transport ] Network ] Data Link ] Physical Datakom høsten 2002 44
OSI Layers (1) ] Physical \ Physical interface between devices [ Mechanical [ Electrical [ Functional [ Procedural ] Data Link \ Means of activating, maintaining and deactivating a reliable link \ Error detection and control \ Higher layers may assume error free transmission Datakom høsten 2002 45
OSI Layers (2) ] Network \ Transport of information \ Higher layers do not need to know about underlying technology \ Not needed on direct links ] Transport \ Exchange of data between end systems \ Error free \ In sequence \ No losses \ No duplicates \ Quality of service Datakom høsten 2002 46
OSI Layers (3) ] Session \ Control of dialogues between applications \ Dialogue discipline \ Grouping \ Recovery ] Presentation \ Data formats and coding \ Data compression \ Encryption ] Application \ Means for applications to access OSI environment Datakom høsten 2002 47
OSI v TCP/IP Datakom høsten 2002 48
St andards ] Required to allow for interoperability between equipment ] Advantages \ Ensures a large market for equipment and software \ Allows products from different vendors to communicate ] Disadvantages \ Freeze technology \ May be multiple standards for the same thing Datakom høsten 2002 49
St andards Organizat ions ] Internet Society \ Internet Architecture Board (IAB) \ Internet Engineering Task Force (IETF) \ Internet Engineering Steering Group (IESG) ] ISO - International Standard for Organization \ JTC Joint Technical Committee ] ITU-T (tidligere CCITT) \ ITU- International Telecommunication Union \ 14 study groups ] ATM forum Datakom høsten 2002 50
Furt her Reading ] Stallings, W. Data and Computer Communications (6th edition), Prentice Hall 1999 chapter 1 ] Web site for Stallings book \ www.shore.net/ ~ ws/ DCC6e.html ] Web sites for IETF, IEEE, ITU-T, ISO ] Internet Requests for Comment (RFCs) ] Usenet News groups \ comp.dcom.* \ comp.protocols.tcp-ip Datakom høsten 2002 51
Int ernet Hist ory (DUO\SDFNHWVZLWFKLQJSULQFLSOHV ] 1961: Kleinrock - queueing theory shows effectiveness of packet-switching ] 1964: Baran - packetswitching in military nets ] 1967: ARPAnet conceived by Advanced Research Projects Agency ] 1969: first ARPAnet node operational ] 1972: \ ARPAnet demonstrated publicly \ NCP (Network Control Protocol) first host-host protocol \ first e-mail program \ ARPAnet has 15 nodes Datakom høsten 2002 52
Int ernet Hist ory,qwhuqhwzrunlqjqhzdqgsursulhwdu\qhwv ] 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 Datakom høsten 2002 53
Int ernet Hist ory QHZSURWRFROVDSUROLIHUDWLRQRIQHWZRUNV ] 1983: deployment of TCP/ IP ] 1982: smtp e-mail protocol defined ] 1983: DNS defined for name-to-ip-address translation ] 1985: ftp protocol defined ] 1988: TCP congestion control ] new national networks: Csnet, BITnet, NSFnet, Minitel ] 100,000 hosts connected to confederation of networks Datakom høsten 2002 54
Int ernet Hist ory VFRPPHUFLDOL]DWLRQWKH::: ] Early 1990 s: ARPAnet decommissioned ] 1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995) ] early 1990s: WWW \ hypertext [Bush 1945, Nelson 1960 s] \ HTML, http: Berners-Lee \ 1994: Mosaic, later Netscape \ late 1990 s: commercialization of the WWW Late 1990 s: ] est. 50 million computers on Internet ] est. 100 million+ users ] backbone links running at 1 Gbps Datakom høsten 2002 55
Int roduc t ion: Sum m ary Covered a ton of material! ] Internet overview ] what s a protocol? ] network edge, core, access network \ packet-switching versus circuit-switching ] performance: loss, delay ] layering and service models ] backbones, NAPs, ISPs ] history You now have: ] context, overview, feel of networking ] more depth, detail later in course Datakom høsten 2002 56
Inform asjon om IP på m ask in 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......... : 00-50-DA-DD-2E-5E DHCP Enabled........... : No IP Address............ : 193.69.136.78 Subnet Mask........... : 255.255.255.0 Default Gateway......... : 193.69.136.54 DNS Servers........... : 193.69.136.53 Datakom høsten 2002 57
ARP - Address Resolution Protocol arp -a Interface: 193.69.136.78 on Interface 0x2 Internet Address Physical Address Type 193.69.136.34 00-60-b0-3d-82-74 dynamic 193.69.136.54 00-10-5a-66-21-78 dynamic 193.69.136.60 00-50-da-4f-31-8c dynamic 193.69.136.61 00-60-97-17-2a-48 dynamic 193.69.136.91 00-60-08-49-2a-fe dynamic 193.69.136.115 08-00-09-70-2c-8e dynamic 193.69.136.133 08-00-09-87-fe-29 dynamic Datakom høsten 2002 58
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