OSI model (Tamil)

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OSI model (Tamil)

  1. 1. i OSI Model Computer Networks & Internet Computing Nifras Ismail
  2. 2. 2OSI / ISO MODELContentsIntroduction ....................................................................................................................................3Layer 7 – Application Layer ................................................................................................................5Layer 6 – Presentation Layer ..............................................................................................................6Layer 5 – Session Layer ......................................................................................................................7Layer 4 – Transport Layer ..................................................................................................................8Layer 3 – Network Layer ....................................................................................................................8Layer 2 – Data Link Layer ....................................................................................................................9Layer 1 - Physical Layer .................................................................................................................... 10References 1. TechExams.net Tech Notes by. John Hiemstra 2. Computer Networks by. Andrew S. Tanenbaum 3. Computer Networks and Internet computing Lecture notes by. Dr. K. Sarveswaran 4. http://www.9tut.com/11 If I make any mistakes or comments about this book mail me : iamnifras@live.com
  3. 3. 3OSI / ISO MODELIntroduction SI Model network devices data transmitO . postal system1. Write your letter2. Insert it into an envelope3. Write information about sender and receiver on that envelope4. Stamp it5. Go to the post office and drop it into a mail inbox we go through some steps to achieve the target, 2 computers connect steps follow . OSI Model . There is 7 steps in this model to connect topc’sThis OSI Table is must be memorized in your heart by the correct order. You can easily All People Seem To Need Data Processingmemorized by the sentence below.
  4. 4. 4 table step layer . device want to send a data to another one that data 1st send to top of the table to bottom ofthe table , but when it receive that data from another it goes in another way ( device Data send data data receive .)Note: The OSI model layers are often referred to by number than by name (for example, we refersaying “layer 3″ to “network layer”) so you should learn the number of each layer as well. data processing layer header , header information ( where the datagoes down , how its going , network devices MAC address , network IP) header LayerReceiving part understand .
  5. 5. 5Now we see the deeper look of each layer on this OSI ModelLayer 7 – Application LayerIt provides the interface between the applications ( application usercommunication .) But notice that the programs you are using (like a webbrowser – IE, Firefox or Opera…) do not belong to Application layer,Telnet, FTP, email client (SMTP), Hyper Text Transfer Protocol (HTTP) , DNS areexamples of Application layer.HTTP :FTP : file transfer .SMTP : email .
  6. 6. 6OPTIONAL :DNS (Domain Name System)It provides domain name to the IPsAll hosts and IPs are saved in a file, that is name as host.txt in ARPANET, So thousands of hostname providing is not a simple problem its very complex, so they invented a method to provide theDomain Name System that is simply say DNS – This is an hierarchically domain based system.This domain names are provide like as postal system that is country , state, town, road and home.Domain names provide in 2 main top levels they are 1. Generic 2. CountriesExample diagram for the levels The top-level domains come in two flavors: generic and countries. The original generic domains were com (commercial), edu (educational institutions), gov (the U.S. Federal Government), int (certain international organizations), mil (the U.S. armed forces), net (network providers), and org (nonprofit organizations). The country domains include one entry for every country, as defined in ISO 3166.Layer 6 – Presentation Layer This layer ensure the presentation of the data. 2 computers communicate format bit format (1,0) datatransmit . data format . Presentation layer concentrate syntax and semantics of the information transmit. Inorder to make it possible for computers with different data representations to communicate, thedata structures to be exchanged can be defined in an abstract way, along with a standardencoding to be used on the wire. The presentation layer manages these abstract datastructures and allows higher-level data structures
  7. 7. 7 In general, it acts as a translator of the network. For example, you want to send anemail and the Presentation will format your data into email format. Or you want to send photosto your friend, the Presentation layer will format your data into GIF, JPG or PNG… format.Dictionary 1. Concentrate – 2. Syntax – 3. Semantics – 4. Transmit – 5. Representation – 6. Exchanged – 7. Abstract way – 8. Encoding – 9. Manage – 10. High-level structure – Human structure 11. General –Layer 5 – Session LayerThe session layer allows users on different machines to establish sessions, maintainedcommunication between them. - communication .Sessions offer various services including 1. Dialog control - 2. Token Management 3. Synchronization. – communication . 120MB Download file 80MB crash 80MB .Dictionary Dig 1. Crash - 2. Token - 3. Establish -
  8. 8. 8Layer 4 – Transport Layer Accept data from above layer and split it up into small segments – layer segments Network layer pass duty . Ensure all segments arrive correctly and upper layers isolated by inevitable changes inhardware devices ( send order all segment .hardware devices ( Routers , hubs , etc…….) layers .This layer maintain 1. Flow control of data – data . 2. Provides for error checking and recovery of data - error checking ( error- free – point – to – point channels) point point errors check . protocolTCP ( Transmission Control Protocol) , UDP ( User Diagram Protocol ) , NETBEUI , SPXDictionary Dig 1. Split – 2. Segments – 3. Arrive – 4. Isolate – 5. Inevitable- 6. Flow – 7. Provide – 8. Recovery – 9. Diagram – 10. Destination -Layer 3 – Network LayerTransport Layer segments packets . packets . packets original datadestination . address routing table packets routing .Network layer : 1. Path determination – source to destination path . 2. Routing – putting address 3. Delivery of packets across the inter-networks. – networks packets delivery . packets connection , . 4. Responsible for logical addressing (Example :IP)
  9. 9. 9 protocols :IP, IPX, ICMP, RIP, OSPX, BGFNetwork layor devices :Layer 3 Switches , Routers , WAP ( Wireless access point – wireless routers)Dictionary Dig 1. Determination – 2. Across – 3. Path – 4. Delivery – 5. Responsible – 6. Put -Layer 2 – Data Link LayerPackets Layer3 message Data frames headeradd .This header contains : 1. Adding hardware destination (MAC address) – doing by switches 2. Source addressAnd this header is also responsible to finding the next destination device on the local network,Note. Layer-3 ( Network layer ) finding the last destination path ( network ) not care who is thereceiving deviceExample of devices use in layer 2 are : switches , bridges ,WAPs ,It divides into mainly 2 parts : 1. LLC – Logical link control - Managing frames - Flow control - Error control 2. MAC – Media access control - Carries physical addresses (MAC addresses)Dictionary Dig 1. Contains- 2. Find- 3. Local network –
  10. 10. 10 4. Care – 5. Divides- 6. Manage 7. Carries- 8. Access -Layer -1 Physical LayerThe Physical Layer defines the physical characteristics of the network such as connections,voltage levels and timing. – . layer bit (1,0) data . - Computer wire data transfer 1,0 format 1 voltage 0 voltage layer .-( how many volts should be used to represent a 1 and how many for a 0) - bit nano seconds - Initial connection established - How many pins networks connectors pluged. physical layer . layer devices : Repeaters and hubs Transmission medium(copper wire, UTP, STP ,fiber …) .i I’m a student , If I make a mistake in this book please inform me - iamnifras@live.com

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