Lan basic


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Lan basic

  1. 1. Local Area Network Basics
  2. 2. IEEE Standards• An association that promotes engineering and electronic improvement• IEEE 802 was started in February 1980• IEEE 802 committee defines frames, speed, distances and types of cabling to use for networking
  3. 3. Protocols and Procedures• Protocols are set of rules which are used by the nodes on a network to communicate with each other• Protocols are developed by committees, different companies developed products confirming to those protocols Standard Protocols Ethernet Token Ring ARCnet
  4. 4. LAN Architecture - I• 802.3 – Defines a standard for physical layer and data link layer of the Ethernet architecture that uses wired connection – Ethernet is an architecture that mainly uses bus topology – Defines various cabling used for different types of topologies
  5. 5. LAN Architecture - II• 802.4 – Defines a standard for Token Bus architecture – Token bus is similar to token ring, but it uses coaxial cables
  6. 6. LAN Architecture - III• 802.5 – Defines a standard for Token ring architecture – Uses the 10 Base T cabling standard – Uses twisted pair cabling to connect devices instead of coaxial cable – Passes data from one computer to another like in a token bus network
  7. 7. IEEE 802.3 Logical relationship with OSI Reference Model• IEEE 802.3 physical layer corresponds to the OSI physical layer• OSI data link layer is divided into two IEEE 802 sublayers • The Media Access Control (MAC) sublayer • The Logical Link Control (LLC) sublayer
  8. 8. Ethernet• Defined by IEEE as the 802.3 standard• Most widely adapted LAN technology• Supports data transfer rates of 10 Mbps, 100 Mbps and 1 Gbps
  9. 9. Introduction to Ethernet• Nodes on an Ethernet network are either DTE (computer, printer) or DCE (switch, router)• Three data rates currently defined for the operation over optical fiber and twisted-pair cables – 10 Mbps – 10Base-T Ethernet – 100 Mbps - Fast Ethernet – 1000 Mbps - Gigabit Ethernet
  10. 10. Working of Ethernet• Ethernet frame is used to transfer data over a network• Each device in an Ethernet network is uniquely identified by a 48 bit (6 bytes) address called Ethernet address• Ethernet addresses are represented as six pairs of hexadecimal digits separated by a colon.
  11. 11. Elements of Ethernet System Elements of Ethernet System Set of Medium Access Medium Ethernet frame Control Rules
  12. 12. Ethernet Medium• Transmits information over the network• Computer D transmits information for Printer C• Computer B and A also receives the information• All devices inspect the destination address• If the received frame is not meant for them, they will reject the frame
  13. 13. Data Transmission• When a computer wants to transmit, it listens to the cable (transmission medium)• If two or more devices simultaneously transmit data on an idle cable, collision may occur
  14. 14. Example of Collision• Each device decides to broadcast an Ethernet frame to other device• Devices listens to the Ethernet medium and detects that no carrier is present• Devices transmit simultaneously, causing a collision
  15. 15. Carrier Sense Multiple Access/ Collision Detection (CSMA/CD)• Permits one device to access to the network media at a time to avoid collision• Networks using CSMA/CD technology such as Ethernet, network devices compete for the network media
  16. 16. Working of CSMA/CD
  17. 17. Carrier Sensing Multiple Access / Collision Avoidance (CSMA/CA)• Set of rules that can avoid collisions, unlike CSMA/CD that handles network transmissions once collisions are detected• In CSMA/CA, all devices are forced to wait for a random number of time slots and sense the medium again• If the medium is sensed to be busy, the device stops the timer until it becomes free again.
  18. 18. Types of Ethernet Cabling Standards10Base5 10Base2 10Base-T 10Base-F
  19. 19. 10Base-5• Thick coaxial cable is also referred to as thicknet• 10Base5 refers to specifications of thick coaxial cable carrying Ethernet signals• The 5 refers to the maximum segment length i.e. 500 meters• RG-8 coaxial cable is used• A 15-pin female DB connector called AUI connector is used to connect the device
  20. 20. 10Base-2• 10Base-2 (thin coaxial cable) is also referred to as thinnet• In 10Base-2, “2” refers to approximate maximum segment length of the cable which is 185 meters• 10Base2 uses RG-58 coaxial cable with BNC connectors• Cheaper and easier to install as compared to 10 Base 5 and 10 Base F
  21. 21. 10Base-T• Allows stations to be attached via twisted pair cable• 10 refers to the transmission speed of 10 Mbps• “T” refers to twisted pair cable• In a 10BaseT network, each computer (node) is connected to a hub
  22. 22. 10 Base-F• Uses fiber optic cable• Possesses excellent noise immunity and is the method of choice when running between buildings or widely separated hubs• 10 Base-F is expensive as the connectors and terminators used in 10 Base-F are costly
  23. 23. Comparing Ethernet TypesEthernet types 10Base5 10Base2 10BaseT 10BaseFMedia Type Thick coaxial Thin coaxial UTP Fiber-optic (RG8) (RG58)Max.segment length 500 185 100 1000 (meters)Frequency(MHZ) 10 10 10 10Max 100 30 1024 1024k Nodes/Segment
  24. 24. Extending the network• A computer network can be extended using repeaters, hubs and bridges• In computer networks, a bridge is an Internetworking device• Repeater regenerates signal• Repeaters remove the unwanted noise in an incoming signal• A hub is a multi port repeater which provides a common point for the connection of network devices