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Transcript
TK3133 Computer Network Technology LAN Technology 1 Introduction LAN concept and technology Importance of sharing in LAN Basic Network topology Hardware addressing and frame type identification 2 Network Category Network connection type : – Point to Point or Mesh network – Sharing communication lines 3 Point to point communication Original line configuration communication system Computer connected to Communication lines with each connected to two computers in forming mesh network or point to point Allow flexibility in hardware communication, packet formatting and etc. Provide security since communication lines are not shared 4 Point to point connection Number of wires increase when number of computer increases Exp: 2,3,4 computer connection 5 Point to point connection Adding a computer (Nth computer) require N1 new connections Number of connection = (N2 – N)/2 Limitation : expensive and too many lines 6 Sharing communication channels Differ with long distance network Prevent weaknesses in point to point : expensive, dedicated and overlapping Introducing LAN – sharing a communication channel (cable) by several computers 7 LAN Reducing number of communication channels LAN developed in early 1970 Main idea – reducing number of channels by sharing connection among computers But not suitable for long distance because of the coordination problem 8 LAN LAN technology reducing the cost by reducing number of connection But connected computers have to compete for using shared connection Using principle of locality of reference to acquire computer communication pattern. 9 Broadcasting network LAN is a broadcasting network – Data packet that sent by a station will be transmitted to all stations LAN topology – Network can be categorized according to the shape – 3 popular topologies • Star, ring and bus 10 Star topology All computers are connected to a middle point called hub Hub as device receives data packet and send it to destination 11 Star topology In practice, cable fixing can be parallel (or not) with computer 12 Star topology consequence :- 13 Ring topology Computers are connected in closed coil. First host will send data to the second host . Second host will send the data to the third host and so is for subsequent host. Short connection cable from computer to the ring 14 Ring topology A computer connected to another two computers. 15 Bus topology A cable connected to all computers A computer has a connector to the shared cable Computers should synchronized and allow only a computer send data at a time. 16 Bus topology A cable connected to many computers 17 Various topology Each topology has its own advantages and disadvantages Selection depends on wiring schema 18 Exp. of LAN Bus- Ethernet Ethernet is the most popular LAN network access control Developed by Xerox in the middle of 70s – maintain by IEEE Using bus topology – A cable – Connect various computers 19 LAN- Ethernet A Ethernet cable is called segment – Up to 500m lenght Transmission rate is 10Mbps, 100Mbps (Fast Ethernet) and 1Gbps (Gigabit Ethernet) Using Manchester encoding signal modulation 20 Manchester encoding (a) Binary encoding, (b) Manchester encoding, (c) Differential Manchester encoding. 21 LAN- Ethernet operation A computer send data at a time Signal is modulated carrier that transmitted from sender into two direction along the segment 22 Carrier Sense Multiple Access with Collision Detection CSMA/CD There in no central control management when computer send to ether use CSMA to coordinate transmission among connected computers Carrier sense: station listen to channel before sending Collision Detection: station can decide whether there is frame clash through listening to the channel while transmitting 23 CSMA/CD - IEEE 802.3 802.3 standard 802.3 basic is 10-Mbps “Ethernet” 24 Wireless LAN 802.11 and CSMA/CA Operating at 11Mbps using frequency in domain 2.4 GHz Avoiding clash by using CSMA with Collision Avoidance 25 LocalTalk LAN technology that use bus topology Interface include Macintosh computer Low-cost, easy to fix and connect use CSMA/CD 26 Token Bus - IEEE 802.4 Disadvantage because there is clash – Choose a technique that avoid clash Token concept – bus and ring Only sender that receives token is allowed to send frame After sending, pass the token 27 Token Bus Fix the whose turn after this to receive the token for equal access 28 Token Ring- IEEE 802.5 (IBM Token Ring) Operating at 4 and 16 Mbps No bus, only nodes and lines Use token transmission to synchronize access to the ring Each node sends frame following clock rotation by getting the token first 29 FDDI Fiber Distributed Data Interconnect (FDDI) is a ring technology – use fiber optic between station – Tansmission at the rate of 100Mbps Use a pair of fiber to create two coils with a centre – As a back-up if there is any damage 30 FDDI Using flow in two direction 31 ATM – Star network Asynchronous Transfer Mode technology that contain packet switch that connect to computers ATM switch form hub in which computer connected in star topology data from sender flow thorough switch to destinations 32 ATM – Star Network Transmission rate is over 100Mbps using fiber optic to connect computer to switch Each connection has 2 fiber 33 Communication in LAN Technique how to send message through LAN medium to specific computer destination Sender computer uses hardware address in frame to identify direction to destination Sender also identify type of data that brought in the frame 34 Identify destination Data is sent through the shared network reach all computers that connected to it Hardware interface trace the frame sent and extract frame from medium But many application only want data to be sent to destination and not all computers 35 Hardware addressing Many network technology has a hardware addressing schema that identify particular station or computer Each station is assigned to a numeric hardware address or unique physical address Sender will insert hardware address to each frame that sent from source and destination. Only station that recognized from frame receive copy of the frame 36 LAN hardware and packet filtering LAN Hardware Organization and computer 37 Hardware address Format numeric value Size is selected according to specific network technology Length is from 1 to 6 bytes unique in a LAN – static, dynamic and configurable 38 Frame Format and Frame Head LAN standard technology define frame format according to the network technology\ general format : Head has address and additional information (in fixed size field). Data area can be in various size 39 Example of frame format Ethernet frame format 40 Part 2- Introduction Interface card – Why need different card – What is transceiver? LAN wired schema Logical and physical topology How to improve LAN? 41 LAN speed and computer data transmission speed of LAN is faster compared to CPU LAN speed is not dependent to any processor speed – Allow mix system on it – New computer can be connected without influencing LAN speed 42 Network hardware interface Computer uses special hardware to network connection – Network Interface card (NIC) that understand electrical signal use on network, rate in which the data received and sent as well as frame detail Connector to computer receive cable to be connected to physical network 43 NIC and network hardware NIC is built for only one type of physical network – Ethernet interface cannot be used with Token Ring However, certain NIC can be used with other hardware similar to – thick, thin and 10BaseT Ethernet – 10Mbps and 100Mbps Ethernet 44 Connection between NIC and physical network 2 methods :– NIC is directly connected to medium – Cable from NIC connect to additional circuit that connected to medium Ethernet wiring method • Standard 10Base5 • standard 10Base2 • standard 10BaseT 45 Connection between NIC and physical network 46 10Base5 - Thick Ethernet Use ether cable AUI cable (drop cable) from NIC to transceiver AUI cable carry digital signal from NIC to transceiver Transceiver generate analog signal to ether cable 47 10Base5 - Thick Ethernet A AUI cable connected computer to transceiver 48 10Base5 49 10Base5 Transceiver 50 Ethernet segment 51 10Base2 - Thin Ethernet Use thinner ether cable – cheaper and easy to fix from thick-net coax Transceiver built on NIC – directly connected to medium Ether cable use BNC connector 52 10Base2 53 10Base2 - Thin-Net 54 10Base-T 10Base-T (Twisted pair/ TP Ethernet) Replace cable AUI with twisted pair cable replace thick coax with hub 55 10BaseT 56 UTP cable category 57 Ethernet All wiring technology use similar Ethernet specification – Similar frame format – Similar CSMA/CD algorithm NIC can accept all three connection technology 58 Comparing wiring scheme 59 Network Topology and Technology 10Base-T – Logically bus topology ; – But physical wiring is star topology – Also known as star-bus Ethernet 60 High-speed Ethernet 61 Fast Ethernet • Fast Ethernet cabling 62 Gigabit Ethernet Data rate 1000 Mbps or 1 Gbps Known as 1000BaseSX/LX or 1000BaseT Use switch Use fiber optic Act as network backbone to connect LAN and high-speed LAN 63 Improving LAN LAN technology is built with limitations of speed, distance and cost LAN technology can cover, up to several 100 meters How to improve LAN? 64 Built LAN for distance Many LAN uses shared medium - Ethernet, token ring The length of medium influences medium access sharing CSMA/CD – delay between frame, minimum length of the frame Token sending – time constrain for token Medium length influences the strength of electrical signal 65 Improving LAN Several techniques to widen LAN medium diameter coverage Many uses additional hardware LAN signal is carried between LAN segment The result is mix technology but original engineering constraint still remain and improvement in distance 66 Repeater To lengthen LAN medium Signal strength influence length limitation To prevent it use Repeater – both-ways, analog amplifier send back analog signal 67 Repeater A repeater effectively double the length of a LAN segment 68 Ethernet repeater Only copy signal between segment – Could not understand frame format – Does not contain hardware address Any Ethernet segment limited to 500 meter Repeater can double to 1,000 meter 69 Ethernet Repeater limit Ethernet standard include limiting 4 repeater between any two Ethernet station 70 Advantage and disadvantage of Repeater Easy to use –plug-in directly Repeater only resend analog signal Conflict influence overall network Noise is also carried along the network 71 Bridge Also connecting two LAN segment Resend frame from a segment to another Manage overall frame – Use NIC as other stations – Perform process in frame 72 Bridge Bridge used in connecting two LAN segment 73 Advantage of Bridge Easy to use – only plug-in Isolate conflict, noise Perform frame filtering – Only send frame whenever needed to LAN segment to destination – Send multicast packet and broadcast Use table 74 How bridge create table Bridge examine source address at each frame Add entry to the list for LAN segment about where the frame is received Should send any frame that no information about destination in the list to each bridge interface 75 Bridge table 76 Bridge Can use many bridge to reach LAN segment Disadvantage is consequence of loop – prevent it with Distributed Spanning Tree algorithma 77 Bridge between building Bridge is placed at a building with connector that connected to LAN segment in another building 78 Long distance Bridge Can use leased line, microwave, laser or satellite to connect two and LAN segment 79 Switching For every port to divide a LAN segment Similar to hub – hub shares a segment with all ports 80 Switch With switching, many stations can send simultaneously Provide higher bandwidth More expensive per port Economically, some suitable to use hub and others suitable to use switch 81