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Transcript
Motivation • Providing basic knowledge about conception, implementation and functioning of computer networks. • Configuration of a network in order to gain experience in that subject. Computer Net Lab/ Praktikum Datenverarbeitung 2 1 History • 1969 the resarch network „ARPANET“ was introduced. It consists of 4 connected computers. • 1976 Queen Elizabeth II. sent an Email from England to America. • 1980 (27th of Oktober) the ARPANET was stopped by a virus. • 1983 the servers got names. Since that time it is not longer neccessary to know the exact path to another system. • 1984 DNS (Domain name services) was established. • 1990 300000 Computers were connected to the Internet. A text oriented search-system (archie) was created. • 1991 Tim Berners-Lee developed the hypertext sytem. The Birthday of HTML. • Today it is assumed that more than one billion (1.000.000.000) computers are connected. Computer Net Lab/ Praktikum Datenverarbeitung 2 2 What is LAN • A local area network is used for the bit seriell transmission among connected but independent devices. A LAN is located within a limited area and belongs completly to the operating company. • LAN is an acronym for „local area network“. A LAN is a group of computers and peripherals in a close area that are connected to share information and resources. Computer Net Lab/ Praktikum Datenverarbeitung 2 3 LAN jobs (1) • Message exchange mail systems • Access to central/shared devices printer, scanner • Access to rescources of other computers distributed programming/calculation • Access to central data shareable Data data bases user administration Computer Net Lab/ Praktikum Datenverarbeitung 2 4 LAN jobs (2) Shared use of information Centralization of administration and support Shared use of hardware and Software Computer Net Lab/ Praktikum Datenverarbeitung 2 5 LAN Modelling • Network size, number of clients, area of the network • Reliability, redundance • Security, avoidance of unauthorized access, firewalls • Costs (purchase, maintenance, administration) • Functionality Computer Net Lab/ Praktikum Datenverarbeitung 2 6 Functions in a LAN Mail server Mailserver Mail server Fax server Faxserver Fax server Database server Databaser server Datenbank Database File-Fileandand printprint server server Directory Serviceserver Client computer Computer Net Lab/ Praktikum Datenverarbeitung 2 7 Network types Peer-to-Peer Network Client-/Server Network Computer Net Lab/ Praktikum Datenverarbeitung 2 8 Network topology Hub BUS STAR Computer Net Lab/ Praktikum Datenverarbeitung 2 RING 9 Network technology (Ethernet) Signal transmission Signal detection CSMA (Carrier Sense Multiple Access) Attributes Access method transfer rate Detect collision CD (Collision Detection) Description CSMA/CD Standard-Ethernet - 10 Mbit/s Fast Ethernet - 100 Mbit/s Gigabit Ethernet - 1 Gbit/s (1.000 Mbit/s) Computer Net Lab/ Praktikum Datenverarbeitung 2 10 Network technology (Token Ring) Logical Physical Attributes Description Access method Tokenpassing transfer rate 4 bis 16 Mbit/s for all cable types Computer Net Lab/ Praktikum Datenverarbeitung 2 11 Network components • Repeater amplifies electrical signals • Hub delivers all packages to all connected stations • Bridge allows the segmentation of a network • Switch delivers packages only to the target computer • Router determines the best route between sender and receiver • Gateway data transfer management from one net into another one Computer Net Lab/ Praktikum Datenverarbeitung 2 12 Protocols Protocol = data transmission language A communication between 2 computers requires that both computers understand the same protocol • NetBeui fast, not routeable, only in Microsoft environment • IPX/SPX Protocol collection for Novell, routeable • Apple Talk Kommunication protokoll for Apple-Network, routeable • TCP/IP Protocol collection for different computer types, routeable Computer Net Lab/ Praktikum Datenverarbeitung 2 13 TCP/IP • • • TCP and IP are two different protocols They build a protocol family with other protocols like UDP and ICMP Only the combination of these protocols offers the well known functionality of a network routeable Windows-Client Segment 1 Windows-Client Segment 2 TCP/IP TCP/IP Router Computer Net Lab/ Praktikum Datenverarbeitung 2 14 IP IP (Internet Protocol) has 3 main tasks: 1. 2. 3. It carries the transport protocols TCP and UDP. It builds IP-Packages out of the data which have to be transmitted It adds additional information, the IP-Header. It contains source and destination address. Computer Net Lab/ Praktikum Datenverarbeitung 2 15 TCP • • • TCP (Transmission Control Protocol) confirms every received data package TCP repeats each data package until its receiving is confirmed TCP is reliable, that means the transmission is guaranteed 32 BIT Computer Net Lab/ Praktikum Datenverarbeitung 2 16 IP-Addresses (1) • The addressing within TCP/IP Networks is realised by use of IPAdresses • 32 Bit Value (IP Byte V4): Byte Byte Byte • Each node (IP-Address) in the Internet is unique • IP-Addresses are divided in Classes • IP-Addresses are divided in Network part (Network-ID) and Host part (Host-ID) • Certain IP-Addresses have special meanings Computer Net Lab/ Praktikum Datenverarbeitung 2 17 IP Address classes Class A 1.Byte(1-126) Network-ID 0xxxxxxx Network-ID Class B 1.Byte(128-191) 10xxxxxx Network-ID Class C 1.Byte(192-223) 110xxxxx Host-ID Host-ID xxxxxxxx Host-ID xxxxxxxx xxxxxxxx Klasse A : 126 nets each with 16777214 devices Klasse B : 16382 nets each with 65534 devices Klasse C : 2097150 nets each with 254 devices. Computer Net Lab/ Praktikum Datenverarbeitung 2 18 Address guidelines • Network ID 127 ist not allowed - 127 is reserved for loopback function (localhost) • Network -ID and Host-ID can‘t be 255 - 255 is the Broadcast Adress • Network -ID and Host-ID can‘t be 0 - 0 means only that network • Host ID must be unique Computer Net Lab/ Praktikum Datenverarbeitung 2 19 IP-Addresses (2) 192.168.2.100 IPAdresse 192.168.3.100 192.168.1.100 192.168.1.0 192.168.2.0 192.168.3.0 Network-Address (Host-ID = 0) 192.168.1.100 192.168.2.101 Computer Net Lab/ Praktikum Datenverarbeitung 2 Host-ID 20 Subnetmask (1) • Seperates Network-ID and Host-ID • Is used in order to decide if the target host is located in the own network or in an external (remote) one • lokal: Net-ID of sender is equal to receivers Net-ID • remote: Net-ID of sender differs from receivers Net-ID IP-Address 10.50.100. 200 Subnetmask 255.255.255. 0 Network- ID 10.50.100. 0 Computer Net Lab/ Praktikum Datenverarbeitung 2 21 Subnetmask (2) Sender-IP 10.50.100. 200 Subnetmask 255.255.255. 0 Network-ID Sender 10.50.100. 0 Receiver-IP 10.50.101. 220 Subnetmask 255.255.255. 0 Network- ID Receiver 10.50.101. 0 Network-ID of sender differs from network-ID of receiver => Receiver IP ist not in the same network Computer Net Lab/ Praktikum Datenverarbeitung 2 22 Private IP-Addresses • There are IP-Ranges which are exclusivly used for private purposes. • Therefore addresses of this range will never be found in the WWW. • There are following private IP-Ranges: 10.0.0.0 10.255.255.255 (A) 172.16.0.0 172.31.255.255 (B) 192.168.0.0 192.168.255.255 (C) Computer Net Lab/ Praktikum Datenverarbeitung 2 23 DHCP • DHCP (Dynamic Host Configuration Protocol) • Enables the automatically configuration of client-devices • Requires a DHCP-Servers which distributes the settings automatically to the clients • Client devices receive an IP-Address, address of the gateway, subnetmask and address of the DNS server • Benefit: manual configuration of the client device installation is not longer necessary Computer Net Lab/ Praktikum Datenverarbeitung 2 24 DNS • DNS = Domain Name Service • Unique host names are used • DNS allows the assignment: IP-Addresses Host name • Each host which should be accessible via its name needs an entry within the database of a name server. Otherwise this machine is only accessible via ist IP-Address • Example: nslookup www.uni-duisburg.de 134.91.4.169 Computer Net Lab/ Praktikum Datenverarbeitung 2 25 IP-Adresses used in our lab Privates Class C-Netz Gateway-IP HUB Client-IP Server-IP Computer Net Lab/ Praktikum Datenverarbeitung 2 26 NAT • Nat = Network Address Translation • Enables the assignment between private IP-Addresses and offical IP-Addresses => Hosts with a private IP-Address have access to the internet. 192.168.0.10 Webserver Webbrowser w2.x2.y2.z2 w1.x1.y1.z1 Internet NAT Computer Net Lab/ Praktikum Datenverarbeitung 2 27 Little exercise 1. 2. What do you think? What kind of IP-Network does our university have? www.uni-due.de = 132.252.184.87 In our lab we will use six (netnumber 1-6) private class C-Nets. Following rules should be used for the setup of the net: Private Class C-Net: 192.168.<netnumber>.xxx The server should get the first IP-Address from the available IP-Adress-Range. The gateway should get the last IP-Address from the available IP-Adress-Range. Clients should get the rest from the available IP-Adress-Range. What are the IP-addresses of server and gateway? What is the IP-Adress-range of the clients? What is the subnetmask? Computer Net Lab/ Praktikum Datenverarbeitung 2 28 Short answer 1. The network of our university is a class B net because the first byte (132) lies in the range between 128-191 Z.B. www.uni-due.de = 132.252.184.87 2. netnumber is 1=> Address of the subnet: Address of the server: Client-Addresses: Gateway address: Broadcast-Address: 192.168.1.0 192.168.1.1 192.168.1.2 - 192.168.1. 253 192.168.1.254 192.168.1.255 Computer Net Lab/ Praktikum Datenverarbeitung 2 29 Netzwerktechnologien (Ethernet 2) Computer Net Lab/ Praktikum Datenverarbeitung 2 30