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chapter 7 ethernet lans

Chapter 7. Networking for Manufacturing. 7-2. 7.1 CSMA/CD. carrier-sense multiple access with collision detection-Ethernet-IEEE 802.3intended for commercial and light industrial environment-physical layer-MAC layer. Chapter 7. Networking for Manufacturing. 7-3. Precursors. random access or contention technique-no fixed time or order for transmission-stations competing for time on the shared mediumALOHA or pure ALOHA-earliest contention technique-originally for ground-based pack9447

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chapter 7 ethernet lans

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    1. CHAPTER 7 Ethernet LANs CSMA/CD 10-Mbps Ethernet 100-Mbps Ethernet Gigabit Ethernet

    2. Chapter 7 Networking for Manufacturing 7-2 7.1 CSMA/CD carrier-sense multiple access with collision detection - Ethernet - IEEE 802.3 intended for commercial and light industrial environment - physical layer - MAC layer

    3. Chapter 7 Networking for Manufacturing 7-3 Precursors random access or contention technique - no fixed time or order for transmission - stations competing for time on the shared medium ALOHA or pure ALOHA - earliest contention technique - originally for ground-based packet radio - free for all

    4. Chapter 7 Networking for Manufacturing 7-4 ALOHA Algorithm - transmission of a frame whenever a station has something to send - wait for the maximum round-trip propagation delay - if an ACK is received during that time, ok - otherwise send it again - after certain number of repeated failures, give up - receiving station to check the correctness of incoming frame by CRC - immediate ACK if valid - ignore the reception if invalid due to noise or collision maximum utilization of about 18 %

    5. Chapter 7 Networking for Manufacturing 7-5 slotted ALOHA - time slots of equal length - transmission start at the beginning of a slot - collision with total overlap - requires some technique for synchronizing slots - maximum utilization of about 37 % propagation delay - the longer it is, the greater chance of collision - short propagation delay compared to frame transmission time in most LANs - if a station can sense the presence of a signal, the station can operate based on quite up-to-date information

    6. Chapter 7 Networking for Manufacturing 7-6 carrier sense multiple access (CSMA) - listen before talk (LBT) - a station with a frame to send listens to the medium to check if another station is talking - if the medium is busy, retry some time later - if the medium is quiet, then transmit - wait for ACK for a period considering the roundtrip propagation delay and contention process of the ACK - if no ACK, assume a collision and retransmit - collision can happen only if other station begins to transmit during the period of the propagation delay improved performance

    7. Chapter 7 Networking for Manufacturing 7-7 nonpersistent CSMA - if busy, check the medium again after a retransmission delay generated from a probability distribution 1-persistent CSMA - if busy, continue to listen until the medium becomes idle and then transmit immediately p-persistent CSMA - if idle, transmit with probability p, or delay one time unit with probability of 1-p (usually the time unit of the maximum propagation delay) - if busy, continue to listen until the medium becomes idle and decide according to the above rule

    8. Chapter 7 Networking for Manufacturing 7-8

    9. Chapter 7 Networking for Manufacturing 7-9 Description of CSMA/CD listen while talk (LWT) capacity waste due to transmission of collided frames in CSMA CSMA/CD procedure - if a collision is detected during transmission, immediately cease the ongoing transmission - send a short jamming signal to let all stations know that there has been a collision - wait a random amount of time and then try to transmit

    10. Chapter 7 Networking for Manufacturing 7-10

    11. Chapter 7 Networking for Manufacturing 7-11

    12. Chapter 7 Networking for Manufacturing 7-12 frame transmission time longer than the time taken to detect a collision - required to have long frames in order for stations to detect a collision which algorithm when the medium is busy ? - 1-persistent for most cases - Ethernet, MITREnet, and IEEE 802.3 - binary random back-off in Ethernet and IEEE by increasing the mean of back-off time by the factor of two at every collision up to 16 attempts

    13. Chapter 7 Networking for Manufacturing 7-13 implementation of carrier sense - sensing transitions of Manchester coding for baseband implementation of collision detection - baseband: * higher voltage swing than that produced by a single transmitter * two attenuated signals may not produce voltage higher than CD threshold - twisted-pair star-wiring approach * logical collision detection * more than one input channel with active signal to any hub

    14. Chapter 7 Networking for Manufacturing 7-14

    15. Chapter 7 Networking for Manufacturing 7-15 frame structure - preamble - start frame delimiter - destination address - source address - length - pad - frame check sequence MAC Frame

    16. Chapter 7 Networking for Manufacturing 7-16 MAC Compatibility Considerations Table 7.1 on p. 180 - slotTime - interFrameGap - attemptLimit - backoffLimit - jamSize - maxFrameSize - minFrameSize - burstLimit

    17. Chapter 7 Networking for Manufacturing 7-17 7.2 10-MBPS ETHERNET <data rate in Mbps><signaling method><maximum segment length in hundreds of meters> alternatives - 10BASE5 - 10BASE2 - 10BASE-T - 10BROAD36 - 10BASE-F

    18. Chapter 7 Networking for Manufacturing 7-18

    19. Chapter 7 Networking for Manufacturing 7-19 Medium Access Unit locations of cable attachment and station - minimum electronics at the cable attachment - rest at the station medium attachment unit (MAU) - at the tap - transmit and receive signals - recognize the presence of a signal - recognize a collision

    20. Chapter 7 Networking for Manufacturing 7-20 10BASE5 - original - 50-ohm coaxial cable 10BASE2 - Cheapernet - thinner 50-ohm coaxial cable 10BASE-T - multiport repeater - star topology (logical bus) - unshielded twisted pair

    21. Chapter 7 Networking for Manufacturing 7-21

    22. Chapter 7 Networking for Manufacturing 7-22

    23. Chapter 7 Networking for Manufacturing 7-23 10BASE-F - added in 1993 - 10BASE-FP - 10BASE-FL - 10BASE-FB - a pair of optical fibers - Manchester encoding

    24. Chapter 7 Networking for Manufacturing 7-24 10BROAD36 - 75-ohm CATV coax - dual or split configuration - scramble - DPSK - bit-by-bit comparison for collision detection - collision enforcement signal - 4-MHz band for collision enforcement signal - total 18 MHz for a channel for dual cable configuration - total 36 MHz for split configuration

    25. Chapter 7 Networking for Manufacturing 7-25 7.3 100-MBPS ETHERNET 100BASE-T, a.k.a. Fast Ethernet - 100BASE-X * 100BASE-TX * 100BASE-FX - 100BASE-T4 - Fig. 7.7 and Table 7.3 on p. 186

    26. Chapter 7 Networking for Manufacturing 7-26 100BASE-X encoding scheme - efficiency for fast transmission speed - timing information - electrical balance 4B/5B –NRZI encoding - 4 bits of data into a 5-bit code group represented by NRZI - for 100BASE-FX - Table 7.5 on pp. 200-201 MLT-3 - to reduce electromagnetic radiation - 4B/5B-NRZ - scrambling, three level encoding (Fig. 7.16 on p. 203) - for 100BASE-TX

    27. Chapter 7 Networking for Manufacturing 7-27 100BASE-T4 Category 3 UTP - 3 pairs used for transmission in either direction - 331/3 Mbps on a single pair - Fig. 7.8 on p. 188 8B6T encoding - 8-bit data into 6 ternary symbols - 25 Mbaud for 331/3 Mbps - Fig. 7.17 on p. 204 - Table 7.6

    28. Chapter 7 Networking for Manufacturing 7-28 Configuration and Operation classes of repeaters - class I for mixed medium (and encoding) - class II for a single medium full-duplex operation - simultaneous transmission and reception - full-duplex interface card - LAN switch instead of repeater (no collision) mixed configuration - 10 and 100 Mbps - autonegotiation

    29. Chapter 7 Networking for Manufacturing 7-29 7.4 GIGABIT ETHERNET switching technique - full-duplex - no contention physical media - 1000BASE-LX - 1000BASE-SX - 1000BASE-T - 1000BAXE-CX

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