Introduction to Information Technologies Chapter 1 - Introduction Fall 2004 Computer Networks Chapter 1 - Introduction History of Internet

Välkommen till Datornätverk A, 5p! Introduction to Information Technologies Fall 2004 Välkommen till Datornätverk A, 5p! Denna kurs avser att ge dig grundläggande förståelse för hur Internet och lokala nätverk är uppbyggda. Kursens karta är TCP/IP- och OSI-modellerna. Målsättningen är att ge dig grundläggande teoretiska och praktiska kunskaper om datakommunikationsprotokoll, nätutrustning, nättopologier, transmissionsmedier, grundläggande adresserings- och routingbegrepp samt enklare verktyg för felsökning av nät. Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 Fler kurser inom området Kursen ingår i flera av våra utbildningsprogram. Det finns flera påbyggnadskurser inom området, bl.a. följande distanskurser: Datateknik A, Nätverksövervakning och drift. Datateknik B, Trådlös Internetaccess. Datateknik C, TCP/IP-nätverk. Överlappande kurser Kursen överlappar till stor del med följande kurser, och kan därför INTE ingå i samma examen: Datateknik A, Internet och datakommunikation 5 poäng Datateknik A, Datakommunikation och drift av nätverk Datateknik B, Multimedie- och kommunikationssystem 4 poäng Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 Kursuppläggning Kurslitteratur: Forouzan, ”Data communications and networking”, 3rd edition, eller senare. Kurswebbplats: webct.miun.se. Besvara samtliga ”quizzar” (automaträttade felvalsfrågor) med minst 60% rätt svar. Två laborationstillfällen En avslutande proejektuppgift. Muntlig redovisning för campusstudenter. Tentamen: Ta med miniräknare. Lektionsplanering och slides: Se WebCT. Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 Chapter 1 Introduction Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 Amount of information Think about a number between 0 and 15. I am now going to guess it using as few yes and no questions as possible. I start by asking: Is the number larger than or equal to 8? Yes Is the it larger than or equal to 12? (The interval is successively divided by 2.) No. Is the number larger than or equal to 10? Is the number larger than or equal to 9? Yes. The amount of information you give me when you tell me that the number is 9 is 4 bits, because the amount of information in bits is the minimum number of yes and no questions that are required. We had 16 options, which is = 24 = 2·2·2·2, corresponding to 4 bits. If the number of options was 32 = 25 , it would require 5 bits. If yes is represented by the binary digit ”1”, and no by ”0”, the value in the above example can be represented by 1 0 1 1. Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 Bits and Bytes N bit can represent M=2N different values. M values can be represented by N = 2log M =log M / log 2 values Example: The N=7 bit ASCII character code consists of M=128 codes. 8 bits = 1 byte (a unit for measuring amount of data) 1 kbit = 1000 bit (previously 1024 bit). 1 Mbit = 1000 kbit (previously 1024 kbit). 1 Gbit = 1000 Mbit. 1 Tbit = 1000 Gbit. Spring 2006 Computer Networks History of Internet

Punkt-till-punkt-förbindelser Introduction to Information Technologies Fall 2004 Punkt-till-punkt-förbindelser Nivå 6 2 1 7 Mikrofon Högtalare Källkodning Källavkodning Digitalisering, komprimering 0110 Felhantering Lägger till fel- rättande eller felupptäckande kod, t.ex. checksumma. Felupptäckt och omsändning, eller felrättning 0100010 Bitfel 0110010 NACK Flödesstyrning Buffert Handskakning 0110010 ACK Modulation Demodulation Elektrisk representation Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 Figure 2.17 The OSI seven layer model Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 The TCP/IP five layer model Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 TCP/IP-modellen Exempel: SMTP, HTTP TCP, UDP IP Ethernet Spring 2006 Computer Networks History of Internet

The Key Elements of a Protocol Introduction to Information Technologies Fall 2004 The Key Elements of a Protocol Syntax referes to the structure of data, meaning the order in which they are presented Semantics refferes to the meaning of each section of bits, how a particular pattern to be interpreted and which action should be taken based on the interpretation Timing refferes to when data should be sent and how fast they can be sent Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 Standards Standards provide guidelines to the manufacturers, vendors, goverment agencies and other service providers to ensure connectivity between different entities Development of standards is a very slow process Two types of standards: De jure (by law) – legislated by an officially recognized body, for example IEEE or ETSI. De facto (by fact) – that are actually implemented into the products) propriatory (closed) nonpropriatory (open) Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 Data Representation Text – using different codes Each character is represented by certain number of bits The number of bits in the code determins the number of different characters ASCII (7 bits), Extended ASCII (8 bits), Unicode (16 bits), ISO (32 bits) Numbers – Binary number system Images – A matrix of pixels represented by bit patterns Video – A combination of images Audio – Digitized voice and music Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 Direction of Data Flow Simplex channel The transmission is only in one direction Half-duplex channel The transmission is in both directions, but only one at a time (both directions cannot be used at the same time) Duplex channel The transmission is in both directions without limitation Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 Figure 1.2 Simplex Example: Video monitor. TV and radio broadcasting. Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 Figure 1.3 Half-duplex Example: Communication radio. 2-wire Ethernet. Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 Figure 1.4 Full-duplex Example: Telephony. 4-wire Ethernet. Spring 2006 Computer Networks History of Internet

Different Line Configurations Introduction to Information Technologies Fall 2004 Different Line Configurations Point-to-point Two devices on a single channel (dedicated channel) Multipoint Many devices on a single channel (shared channel) Example: Bus network Wireless Network Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 Topology of Networks Topology defines the arrangement of links in a network Topology Ring Partial Mesh Full Mesh Bus Star Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 Figure 1.9 Star topology or switch Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 Figure 1.10 Bus topology Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 Figure 1.11 Ring topology Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 LAN, MAN och WAN Lokalt nätverk Globalt nätverk Stadsnät Spring 2006 Computer Networks History of Internet

Computer Networks Classification Introduction to Information Technologies Fall 2004 Computer Networks Classification 0.1 m Circuit board Data flow machine 1 m System Multicomputer Room 10 m 100 m Building Local area Network (LAN) 1 km Campus 10 km City Metropolitan Area Network (MAN) 100 km Country Wide Area Network (WAN) Continent 1000 km 10,000 km Planet The Internet Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 Nättopologier för WAN Växlat WAN (stjärnnät) T.ex. X.25 eller ATM Hopkopplade LAN och WAN = internetwork T.ex. Internet. Nätnoder: Växel. Kopplar ihop punkt-till-punkt-länkar. Router=vägväljare, kopplar ihop nätverk med olika teknologier. Datorer, terminaler, skrivare, etc. Spring 2006 Computer Networks History of Internet

Internetworking Concept and Model Introduction to Information Technologies Fall 2004 Internetworking Concept and Model The goal is to build a unified, cooperative interconnection of networks that supports a universal communication service Detaches the notions of communication from the details of network technologies, and hides low level details from the user Provides a mechanism that delivers packet from their source to their ultimate destination in real time Spring 2006 Computer Networks History of Internet

Introduction to Information Technologies Fall 2004 The Internet Today Communication is possible by using a common Internet protocol that glues different networks. Internet emerged from the academic community and therefore has no central governance so far. Spring 2006 Computer Networks History of Internet

The internet versus the Internet Introduction to Information Technologies Fall 2004 The internet versus the Internet Internetowork or internet (small ”i”) – generic term to mean an interconnection of networks Internet (Uppercase I) – the specific worldwide network that uses the IP protocol (Internet protocol) Spring 2006 Computer Networks History of Internet