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OSI MODEL
OSI LAYER <ul><li>Virtually all networks in use today are based in some fashion  </li></ul><ul><li>on the  Open Systems In...
THE OSI REFERENCE MODEL 7  Application 6  Presentation 5  Session 4  Transport 3  Network 2  Data Link 1  Physical The OSI...
<ul><li>The seven layers, which separate into two sets, are:  </li></ul><ul><li>APPLICATION SET   </li></ul><ul><ul><li>La...
The seven layers of the OSI Reference Model
This is the layer that actually interacts with the operating system or application whenever the user chooses to transfer  ...
<ul><li>RESPONSIBLE FOR APPLICATION LAYER </li></ul><ul><li>Interface between the user & the computer (applications &  </l...
<ul><li>CORRESPONDING PROTOCOLS </li></ul><ul><ul><li>1.   SNMP 6.  FTP </li></ul></ul><ul><ul><li>2. TELNET 7.  WWW </li>...
P R E S E N T A T I O N  L A Y E R The Presentation layer performs code conversion and  data reformatting (syntax translat...
<ul><li>P R E S E N T A T I O N  L A Y E R </li></ul><ul><li>RESPONSIBLE FOR PRESENTATIOAN LAYER </li></ul><ul><li>Transla...
RESPONSIBLE FOR THE PRESENTATION LAYER 7. Messages are sent between layers 8. Communicates through  GATEWAYS   and  APPLIC...
  S E S S I O N  L A Y E R   This Layer establishes, maintains and ends communication  with the receiving device.  The Ses...
S E S S I O N  L A Y E R 3  Network 2  Data Link 7  Application 6  Presentation 5  Session 4  Transport 1  Physical This l...
<ul><li>RESPONSIBLE FOR SESSION LAYER </li></ul><ul><li>Responsible for opening, using and closing session.  </li></ul><ul...
RESPONSIBLE FOR SESSION LAYER 4. Handles remote procedure calls. 5.Communicates through Gateways & application interfaces....
The Transport layer ensures data is successfully sent and received between the two computers. If data is sent incorrectly,...
T R A N S P O R T  L A Y E R This layer breaks up the data from the sending host and then reassembles it in the receiver. ...
<ul><li>RESPONSIBLE FOR TRANSPORT LAYER </li></ul><ul><li>Responsible for  PACKET HANDLING .  Ensures error free  </li></u...
RESPONSIBLE FOR TRANSPORT LAYER 5. Acknowledges successful receipt of data. 6. TCP/SPX - connection oriented communication...
<ul><li>The Network layer establishes, maintains, and terminates  </li></ul><ul><li>logical and/or physical connections.  ...
N E T W O R K  L A Y E R 7  Application 6  Presentation 5  Session 4  Transport 3  Network 2  Data Link 1  Physical Someti...
<ul><li>RESPONSIBLE FOR  NETWORK LAYER </li></ul><ul><li>Logical addressing - software addresses to hardware  </li></ul><u...
RESPONSIBLE FOR  NETWORK LAYER 5. Sends messages and reports errors regarding packet  delivery (ICMP) 6. Communicates thro...
D A T A L I N K  L A Y E R <ul><li>The Data-Link layer handles the physical transfer, framing,  </li></ul><ul><li>flow con...
D A T A L I N K  L A Y E R This layer provides reliable transit of data across a physical link. Makes decisions based on p...
<ul><li>RESPONSIBLE FOR DATALINK LAYER </li></ul><ul><li>Provides for flow of data over a single link from one  </li></ul>...
RESPONSIBLE FOR DATALINK LAYER 6. CRC is added at this Layer (Error detection). 7. If CRC fails at the receiving computer,...
<ul><li>RESPONSIBLE FOR DATALINK LAYER </li></ul><ul><li>10. Manages physical layer communications between  </li></ul><ul>...
<ul><li>RESPONSIBLE FOR DATALINK LAYER </li></ul><ul><li>LLC (Logical Link Control) - The upper sub-layer, which  </li></u...
<ul><li>CORRESPONDING PROTOCOLS </li></ul><ul><li>HDLC - (High-level Data Link Control) </li></ul><ul><li>It Supports Asyn...
P H Y S I C A L  L A Y E R <ul><li>The Physical layer provides the electrical and mechanical  </li></ul><ul><li>interface ...
P H Y S I C A L  L A Y E R 7  Application 6  Presentation 5  Session 4  Transport 3  Network 2  Data Link 1  Physical This...
<ul><li>RESPONSIBLE FOR PHYSICAL LAYER </li></ul><ul><li>Data (BITS) is sent across physical media like wires and ‘ </li><...
RESPONSIBLE FOR PHYSICAL LAYER 5. Specifies how signals are transmitted on network 6. Communicates through:  REPEATERS, HU...
 
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Hardware7

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  1. 1. OSI MODEL
  2. 2. OSI LAYER <ul><li>Virtually all networks in use today are based in some fashion </li></ul><ul><li>on the Open Systems Interconnection (OSI) standard. </li></ul><ul><li>OSI was developed in 1984 by the International Organization </li></ul><ul><li>for Standardization (ISO), a global federation of national </li></ul><ul><li>standards organizations representing approximately 130 </li></ul><ul><li>Countries. </li></ul><ul><li>The ISO created the OSI to make the IOS more efficient. </li></ul><ul><li>ISO - International Organization for Standardization </li></ul><ul><ul><ul><li>OSI - Open System Interconnection </li></ul></ul></ul><ul><ul><ul><li>IOS - Internet work Operating System </li></ul></ul></ul>
  3. 3. THE OSI REFERENCE MODEL 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical The OSI Model will be used throughout your entire networking career!
  4. 4. <ul><li>The seven layers, which separate into two sets, are: </li></ul><ul><li>APPLICATION SET </li></ul><ul><ul><li>Layer 7: Application </li></ul></ul><ul><ul><li>Layer 6: Presentation </li></ul></ul><ul><ul><li>Layer 5: Session </li></ul></ul><ul><ul><li>TRANSPORT SET </li></ul></ul><ul><ul><li>Layer 4: Transport </li></ul></ul><ul><ul><li>Layer 3: Network </li></ul></ul><ul><ul><li>Layer 2: Data </li></ul></ul><ul><ul><li>Layer 1: Physical </li></ul></ul>THE OSI REFERENCE MODEL
  5. 5. The seven layers of the OSI Reference Model
  6. 6. This is the layer that actually interacts with the operating system or application whenever the user chooses to transfer files, read messages or perform other network related activities. A P P L I C A T I O N L A Y E R 3 Network 2 Data Link 7 Application 6 Presentation 5 Session 4 Transport 1 Physical This layer deal with networking applications. Examples:  Email  Web browsers PDU - User Data
  7. 7. <ul><li>RESPONSIBLE FOR APPLICATION LAYER </li></ul><ul><li>Interface between the user & the computer (applications & </li></ul><ul><li>Gateways). </li></ul><ul><li>Provides services that directly support user applications, </li></ul><ul><li>such as the USER INTERFACE, E-MAIL, FILE TRANSFER, </li></ul><ul><li>TERMINAL EMULATION, DATABASE ACCESS, etc. </li></ul><ul><li>Allows applications to use the network. </li></ul><ul><li>Handles Network access, flow control & error recovery. </li></ul>A P P L I C A T I O N L A Y E R
  8. 8. <ul><li>CORRESPONDING PROTOCOLS </li></ul><ul><ul><li>1. SNMP 6. FTP </li></ul></ul><ul><ul><li>2. TELNET 7. WWW </li></ul></ul><ul><ul><li>3. HTTP 8. SMB </li></ul></ul><ul><ul><li>4. TCP 9. TFTP </li></ul></ul><ul><ul><li>5. NFS 10. SMTP </li></ul></ul><ul><li>CORRESPONDING DEVICES </li></ul><ul><li>GATEWAYS </li></ul>A P P L I C A T I O N L A Y E R
  9. 9. P R E S E N T A T I O N L A Y E R The Presentation layer performs code conversion and data reformatting (syntax translation). It is the translator of the network, making sure the data is in the correct form for the receiving application. This layer is responsible for presenting the data in the required format which may include:  Encryption  Compression PDU - Formatted Data 3 Network 2 Data Link 7 Application 6 Presentation 5 Session 4 Transport 1 Physical
  10. 10. <ul><li>P R E S E N T A T I O N L A Y E R </li></ul><ul><li>RESPONSIBLE FOR PRESENTATIOAN LAYER </li></ul><ul><li>Translation of data into understandable format for </li></ul><ul><li>transmission </li></ul><ul><li>2 . Handles character encoding, bit order and byte order </li></ul><ul><li>issues. Encodes and decodes data. </li></ul><ul><li>3. Data compression and encryption takes place at this layer. </li></ul><ul><li>4. Generally determines the structure of data </li></ul><ul><li>5. The redirector works at this layer. </li></ul><ul><li>6. Responsible for protocol conversion </li></ul>
  11. 11. RESPONSIBLE FOR THE PRESENTATION LAYER 7. Messages are sent between layers 8. Communicates through GATEWAYS and APPLICATION INTERFACES CORRESPONDING PROTOCOLS JPEG· MIDI· MPEG·  All kinds of music pictures & movie formats·  CORRESPONDING DEVICES GATEWAY
  12. 12. S E S S I O N L A Y E R This Layer establishes, maintains and ends communication with the receiving device. The Session layer decides when to turn communication on and off between two computers It provides the mechanisms that control the data-exchange process and coordinates the interaction between them. It sets up and clears communication channels between two communicating components.
  13. 13. S E S S I O N L A Y E R 3 Network 2 Data Link 7 Application 6 Presentation 5 Session 4 Transport 1 Physical This layer establishes, manages, and terminates sessions between two communicating hosts. Example:  Client Software ( Used for logging in) PDU - Formatted Data
  14. 14. <ul><li>RESPONSIBLE FOR SESSION LAYER </li></ul><ul><li>Responsible for opening, using and closing session. </li></ul><ul><li>It allows applications on connecting systems to establish </li></ul><ul><li>a session. </li></ul><ul><li>2. Provides synchronization between communicating computers </li></ul><ul><li>(nodes), messages are sent between layers (i.e. Manages </li></ul><ul><li>upper layer errors). </li></ul><ul><li>3. Also places checkpoints in the data flow, so that if trans </li></ul><ul><li>-mission fails, only the data after the last checkpoint needs </li></ul><ul><li>to be retransmitted. </li></ul>S E S S I O N L A Y E R
  15. 15. RESPONSIBLE FOR SESSION LAYER 4. Handles remote procedure calls. 5.Communicates through Gateways & application interfaces. CORRESPONDING PROTOCOLS Network File System (NFS CORRESPONDING DEVICES GATEWAYS S E S S I O N L A Y E R
  16. 16. The Transport layer ensures data is successfully sent and received between the two computers. If data is sent incorrectly, this layer has the responsibility to ask for retransmission of the data. This layer acts as an interface between the bottom and top three layers. By providing the session layer with a reliable message-transfer service, it hides the detailed operation of the underlying network from the session layer. This layer maintains flow control of data and provides for error checking and recovery of data between the devices. T R A N S P O R T L A Y E R
  17. 17. T R A N S P O R T L A Y E R This layer breaks up the data from the sending host and then reassembles it in the receiver. It also is used to insure reliable data transport across the network. PDU - Segments 3 Network 2 Data Link 7 Application 6 Presentation 5 Session 4 Transport 1 Physical
  18. 18. <ul><li>RESPONSIBLE FOR TRANSPORT LAYER </li></ul><ul><li>Responsible for PACKET HANDLING . Ensures error free </li></ul><ul><li>delivery. Repackages messages, divides messages into </li></ul><ul><li>smaller packets (Fragments and reassembles data), and </li></ul><ul><li>handles error handling </li></ul><ul><li>2. Ensures proper sequencing and without loss and duplication. </li></ul><ul><li>3. Takes action to correct faulty transmissions. </li></ul><ul><li>4. Controls flow of data. </li></ul><ul><li>5. Acknowledges successful receipt of data. </li></ul>T R A N S P O R T L A Y E R
  19. 19. RESPONSIBLE FOR TRANSPORT LAYER 5. Acknowledges successful receipt of data. 6. TCP/SPX - connection oriented communication for applications to ensure error free delivery. 8. Communicates through Gateway Services, routers & Brouters. CORRESPONDING PROTOCOLS TCP, UDP, SPX, NetBEUI CORRESPONDING DEVICES GATEWAYS T R A N S P O R T L A Y E R
  20. 20. <ul><li>The Network layer establishes, maintains, and terminates </li></ul><ul><li>logical and/or physical connections. </li></ul><ul><li>The network layer is responsible for translating logical </li></ul><ul><li>addresses, or names, into physical addresses. </li></ul><ul><li>It provides network routing and flow-control functions across </li></ul><ul><li>the computer-network interface </li></ul><ul><li>This layer provides transparent transfer of data between end </li></ul><ul><li>systems.   </li></ul>N E T W O R K L A Y E R
  21. 21. N E T W O R K L A Y E R 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical Sometimes referred to as the “Cisco Layer”. Makes “Best Path Determination” decisions based on logical addresses (usually IP addresses). PDU – Packets
  22. 22. <ul><li>RESPONSIBLE FOR NETWORK LAYER </li></ul><ul><li>Logical addressing - software addresses to hardware </li></ul><ul><li>addresses are resolved (ARP/RARP). </li></ul><ul><li>2. Routing of message (Packets) between hosts & networks </li></ul><ul><li>(IP/IPX). </li></ul><ul><li>3. Determining the best route (Makes routing decisions & </li></ul><ul><li>forwards packets for devices that could be farther away </li></ul><ul><li>than a single link. </li></ul><ul><li>4. Moves information to the correct address. </li></ul>N E T W O R K L A Y E R
  23. 23. RESPONSIBLE FOR NETWORK LAYER 5. Sends messages and reports errors regarding packet delivery (ICMP) 6. Communicates through GATEWAY SERVICES, ROUTERS & BROUTERS CORRESPONDING PROTOCOLS 1. IP 4. ARP 7. ICMP 2. IPX 5. RARP 8. DLC 3. RIP 6. OSPF   9. NetBEUI CORRESPONDING DEVICES ROUTERS & BROUTERS N E T W O R K L A Y E R
  24. 24. D A T A L I N K L A Y E R <ul><li>The Data-Link layer handles the physical transfer, framing, </li></ul><ul><li>flow control and error-control functions (and retransmission </li></ul><ul><li>in the event of an error) over a single transmission link. </li></ul><ul><li>It is responsible for getting the data packaged and onto the </li></ul><ul><li> network cable. </li></ul><ul><li>The data link layer provides the network layer reliable </li></ul><ul><li> information-transfer capabilities. </li></ul><ul><li>The data-link layer is often subdivided into two parts. </li></ul><ul><ul><ul><li>Logical Link Control (LLC) </li></ul></ul></ul><ul><ul><ul><li>Medium Access Control (MAC) </li></ul></ul></ul>
  25. 25. D A T A L I N K L A Y E R This layer provides reliable transit of data across a physical link. Makes decisions based on physical addresses (usually MAC addresses). PDU – Frames 3 Network 2 Data Link 7 Application 6 Presentation 5 Session 4 Transport 1 Physical
  26. 26. <ul><li>RESPONSIBLE FOR DATALINK LAYER </li></ul><ul><li>Provides for flow of data over a single link from one </li></ul><ul><li>device to another </li></ul><ul><li>2. Controls access to communication channel </li></ul><ul><li>3. Controls flow of data. </li></ul><ul><li>4. Packets placed into frames at this layer. </li></ul><ul><li>5. Identifies the specific computer on the network. </li></ul>D A T A L I N K L A Y E R
  27. 27. RESPONSIBLE FOR DATALINK LAYER 6. CRC is added at this Layer (Error detection). 7. If CRC fails at the receiving computer, this layer will request re-transmission. 8. MAC addresses are resolved at this Layer (switches, brouters and bridges function on this layer using the MAC sub layer) 9. Sends data from network layer to physical layer. D A T A L I N K L A Y E R
  28. 28. <ul><li>RESPONSIBLE FOR DATALINK LAYER </li></ul><ul><li>10. Manages physical layer communications between </li></ul><ul><li> connecting systems. </li></ul><ul><li>11. Data frames are sent between layers. </li></ul><ul><li>12. Communicates through: SWITCHES, BRIDGES & INTELLIGENT </li></ul><ul><li> HUBS </li></ul><ul><li>13. The data-link layer is often subdivided into two parts. </li></ul><ul><ul><ul><li>i) Logical Link Control (LLC) </li></ul></ul></ul><ul><ul><ul><li>ii) Medium Access Control (MAC) </li></ul></ul></ul>D A T A L I N K L A Y E R
  29. 29. <ul><li>RESPONSIBLE FOR DATALINK LAYER </li></ul><ul><li>LLC (Logical Link Control) - The upper sub-layer, which </li></ul><ul><li>establishes and maintains links between communicating </li></ul><ul><li>devices. Also responsible for frame error correction and </li></ul><ul><li>hardware addresses. </li></ul><ul><li>  </li></ul><ul><li>MAC (Media Access Control) - The lower sub-layer, </li></ul><ul><li>which controls how devices share a media channel. </li></ul><ul><li>Either through CONTENTION or TOKEN PASSING. </li></ul>D A T A L I N K L A Y E R
  30. 30. <ul><li>CORRESPONDING PROTOCOLS </li></ul><ul><li>HDLC - (High-level Data Link Control) </li></ul><ul><li>It Supports Asynchronous & synchronous Transmissions. Uses LLC flow control. </li></ul><ul><li>CORRESPONDING DEVICES </li></ul><ul><li>BROUTERS </li></ul><ul><li>BRIDGES </li></ul><ul><li>SWITCHES </li></ul>D A T A L I N K L A Y E R
  31. 31. P H Y S I C A L L A Y E R <ul><li>The Physical layer provides the electrical and mechanical </li></ul><ul><li>interface to the network medium (the cable). </li></ul><ul><li>This layer gives the data-link layer its ability to transport a </li></ul><ul><li>stream of serial data bits between two communicating </li></ul><ul><li>Systems. </li></ul><ul><li>It conveys the bits that move along the cable. </li></ul><ul><li>It is responsible for making sure that the raw bits get from </li></ul><ul><li>one place to another, no matter what shape they are in. </li></ul>
  32. 32. P H Y S I C A L L A Y E R 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical This is the physical media through which the data, represented as electronic signals, is sent from the source host to the destination host. Examples:  CAT5 (what we have)  Coaxial (like cable TV)  Fiber optic PDU – Bits
  33. 33. <ul><li>RESPONSIBLE FOR PHYSICAL LAYER </li></ul><ul><li>Data (BITS) is sent across physical media like wires and ‘ </li></ul><ul><li>hubs. </li></ul><ul><li>2. Responsible for encoding scheme (like Manchester </li></ul><ul><li>encoding) </li></ul><ul><li>3. Defines cables, cards and physical aspects. </li></ul><ul><li>4. Provides electrical and mechanical interfaces for a </li></ul><ul><li>network. </li></ul>P H Y S I C A L L A Y E R
  34. 34. RESPONSIBLE FOR PHYSICAL LAYER 5. Specifies how signals are transmitted on network 6. Communicates through: REPEATERS, HUBS, SWITCHES, CABLES, CONNECTORS, RECEIVERS, & MULTIPLEXERS CORRESPONDING PROTOCOLS None CORRESPONDING DEVICES 1. Brouters  4. Amplifiers 7. Receivers 10. Cables 2. Hubs 5. Transceivers 8. Transmitters 11. Switches 3. Repeaters   6. Multiplexers    9. Connectors  P H Y S I C A L L A Y E R
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