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Osi layers
Osi layers
Osi layers
Osi layers
Osi layers
Osi layers
Osi layers
Osi layers
Osi layers
Osi layers
Osi layers
Osi layers
Osi layers
Osi layers
Osi layers
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Osi layers

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    • 1. OSI Reference Model
    • 2. OSI Reference Model • OSI was developed by the International Organization for Standardization (ISO) and introduced in 1984. • It is a layered architecture (consists of seven layers). • Each layer defines a set of functions in data communication.
    • 3. OSI Model Layers Layer - 7 Application Application Layer - 6 Presentation Presentation Layer - 5 Session Session Layer - 4 Transport Transport Layer - 3 Network Network Layer - 2 Data Link Data Link Layer - 1 Physical Physical User support Layers or Software Layers Core layer of the OSI Network support Layers or Hardware Layers
    • 4. Application Layer Application Layer is responsible for providing an interface for the users to interact with application services or Networking Services . Ex: Web browser etc. Identification of Services is done using Port Numbers. Port is a logical communication Channel Port number is a 16 bit identifier. Total No. Ports 0 – 65535 Reserved Ports 1 - 1023 unreserved Ports 1024 – 65535
    • 5. Examples of Networking Services Service Port No HTTP 80 FTP 21 SMTP 25 TELNET 23 TFTP 69
    • 6. Presentation Layer defines a specific format for the date to be sent over the network The major functions described at this layer are.. Encoding – Decoding Ex: ASCII, EBCDIC (Text) JPEG,GIF,TIFF (Graphics) MIDI,WAV (Voice) MPEG,DAT,AVI (Video) Encryption – Decryption Ex: DES, 3-DES, AES Compression – Decompression
    • 7. Session Layer • It deals with sessions or Interactions between the applications. • It is responsible for establishing, maintaining and terminating the sessions. • Session layer organizes communication through simplex, half-duplex or full-duplex
    • 8. Transport Layer Transport Layer It is responsible for end-to-end transportation of data between the applications. The major functions described at the Transport Layer are.. • Identifying Service • Multiplexing & De-multiplexing • Segmentation • Sequencing & Reassembling • Error Correction • Flow Control
    • 9. Identifying a Service Services are identified at this layer with the help of Port No’s. The major protocols which takes care of Data Transportation at Transport layer are…TCP,UDP TCP • Transmission Control Protocol UDP • User Datagram Protocol • Connection Oriented • Connection Less • Reliable • Unreliable communication communication( with Ack’s ) ( no Ack’s ) • Slower data Transportation • Faster data Transportation • Protocol No is 6 • Protocol No is 17 Eg: HTTP, FTP, SMTP Eg: DNS, DHCP, TFTP
    • 10. Network Layer • It is responsible for end-to end Transportation of data across multiple networks. • Logical addressing & Path determination (Routing) are described at this layer. The protocols works at Network layer are Routed Protocols: IP,IPX, AppleTalk.. Etc Routed protocols acts as data carriers and defines logical addressing. Routing Protocols: RIP, OSPF.. Etc Routing protocols performs Path determination (Routing). Routers, Multilayer Switches operate at this layer
    • 11. Datalink Layer It is responsible for end-to-end delivery of data between the devices on a Network segment. Data link layer comprises of two sub-layers. • MAC (Media Access Control) It deals with hardware addresses (MAC addresses). MAC addresses are 12 digit Hexa-decimal identifiers used to identify the devices uniquely on the network segment. It also provides ERROR DETECTION using CRC (Cyclic Redundancy Check) and FRAMING (Encapsulation). Ex: Ethernet, Token ring…etc • Logical Link Control (LLC) LLC used to support multiple network protocols with single NIC card. • Switches, Bridges Work in this layer
    • 12. Physical Layer • It transfers the data in bits format i.e. 01010101010 (zeros and ones). • Conversion of bits over the media depends on type of the media used • Copper media : Electrical signals of different voltages • Fiber media : Light pulses of different wavelengths • Wireless media: Radio frequency waves • Hubs,repeaters, modems operate at this layer
    • 13. Data format at different Layers Application Application Data Presentation Presentation Data Session Session Data Transport Transport Segment Network Network Packet Data Link Data Link Frame Physical Physical Bits
    • 14. Comparing OSI with TCP/IP Layers OSI Layers TCP/IP Layers Application Application Presentation Presentation Application Application Session Session Transport Transport Host-to-Host Host-to-Host Network Network Internet Internet Data Link Data Link Physical Physical Network Network Access Access

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