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Ethernet CSMA PowerPoint Presentation
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Ethernet CSMA

Ethernet CSMA

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Ethernet CSMA

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    1. Ethernet (CSMA/CD) Overview

    2. Ethernet 1-2-3 Originated from a project by Digital, Intel, and Xerox The most popular LAN standard in the world Connects 80% of LAN devices The IEEE (Institute for Electrical and Electronics Engineers) 802.3 CSMA/CD (Carrier Sensing Multiple Access with Collision Detection) committee now forms and administers Ethernet standards The unit of data traveling on Ethernet is called frame (many variations in structure) Ethernet and CSMA/CD can be used interchangeably Implemented on NICs (Network Interface Cards) Ethernet technology is at the physical and data link layers

    3. Ethernet Standards

    4. Ethernet and OSI Model

    5. IEEE 802.3 CSMA/CD Protocol Implemented in the Data Link Layer (Layer 2) Rule #1: Do not talk if someone else is speaking If a NIC does not hear another station sending, it may transmit If another station is transmitting, a NIC must wait until no station is transmitting Rule #2: Wait if two or more try to talk at the same time Occasionally, two or more stations transmit at the same time (collision) All involved stations stop transmitting and wait for a random amount of time When the wait is over, follow Rule#1 The during of the random wait increase if the collision occurs again After 16 collisions and random wait, the NIC gives up trying to deliver the frame

    6. CSMA

    7. Collision Detection

    8. Ethernet Frame Formats Ethernet Version II Original format Include a 2-byte Type field to indicate higher-layer (the Network Layer) protocol carried inside the frame IEEE 802.3 Novell uses this format The 2-byte Type field was replaced by the length field IEEE 802.3 with 802.2 LLC (Logical Link Control) IEEE 802.3 with SNAP (SubNetwork Access Protocol)

    9. Ethernet Version II Format

    10. Version II Example

    11. Explanation of the Example Destination address The MAC address of the device the frame is intended for An address of FF FF FF FF FF FF means broadcasting will be discussed with ARP (Address Resolution Protocol) Source address NIC address of the sending machine Type 81 37 means Novell traffic

    12. Ethernet Cabling Options Dealing with the Physical Layer (Layer 1) Cabling specifications Topologies: (the order in which stations receive bits) Connectors 10Mbps 10Base5 10Base2 10baseT 10BaseFL 100Mbps 100BaseTX 100BaseT4 100BaseFX (multimode Fiber Optic) Gigabit Ethernet

    13. 10Base5 Ethernet

    14. Characteristics of 10Base5 Ethernet Uses a large coaxial cable Stations are connected to the cable using a vampire tap A transceiver or MAU (medium attachment unit) is mounted on the vampire tap An AUI (attachment interface unit) cable runs from the transceiver to the station Coaxial cable is installed in a bus topology (straight line) with a 50W terminator. One end should be grounded Can have up to 100 stations, up to 500 meters The LAN fails if there is one break in the cabling system

    15. 10Base2 Ethernet

    16. Characteristics of 10Base2 Ethernet Uses thinner cable (RG58) BNC T-connectors are used Cabling is configured in a bus topology Each of the cable is terminated with a 50W terminator Up to 30 stations cab be attached Cabling cannot exceed 185 meters (607 feet) in total length for a segment A single cable fault causes total LAN failure

    17. 10BaseT Ethernet

    18. Characteristics of 10BaseT Ethernet UTP (unshielded Twisted Pairs) cabling, category 3 or higher, is installed A hub and NIC are used to connect devices Has a 100-meter distance limitation RJ45 connectors are used on the hubs and NICs Pins 1, 2, 3, and 6 are used on the RJ45 connectors If one cable breaks, only that connection is affected Patch panels and wall jacks are used to facilitate moves, additions, or changes

    19. 10BaseFL Ethernet (Fiber Link)

    20. Characteristics of 10BaseFL Ethernet Can be used to connect end users or as background connection Use duplex connections (two strands of fiber) Uses multimode fiber optic cable Supports distances of 2,000 meters Connects the transmit port of one device to the receive port of the other component on both ends

    21. Ethernet Hubs Hubs receiving the bit stream from the transmitting device Hubs examine the incoming bit stream, resynchronize each bit, and flood the bit stream to the other posts on the collision domain at 100 percent strength

    22. 10Mbps Ethernet Design: The 5-4-3 Rule