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Data and Computer Communications

Data and Computer Communications. Chapter 16 – High Speed LAN s. Ninth Edition by William Stallings. High Speed LAN s. Congratulations . I knew the record would stand until it was broken . - Yogi Berra. Introduction. rapid changes in technology designs broader use of LANs

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Data and Computer Communications

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  1. Data and Computer Communications Chapter 16 – High Speed LANs Ninth Edition by William Stallings Data and Computer Communications, Ninth Edition by William Stallings, (c) Pearson Education - Prentice Hall, 2011

  2. High Speed LANs Congratulations. I knew the record would stand until it was broken. - Yogi Berra

  3. Introduction • rapid changes in technology designs • broader use of LANs • new schemes for high-speed LANs • high-speed technologies: • Fast and Gigabit Ethernet • Fibre Channel • High-Speed Wireless LANs

  4. Characteristics of Some High-Speed LANs 802.11n : 540 Mbps max 100 Mbps typical

  5. CSMA/CD Precursors

  6. CSMA/CD Precursors • Carrier Sense Multiple Access (CSMA) • station listens to determine if there is another transmission in progress • if idle, station transmits • waits for acknowledgment • if no acknowledgment, collision is assumed and station retransmits • utilization far exceeds ALOHA

  7. Nonpersistent CSMA

  8. 1-persistent CSMA • 1-persistent CSMA avoids idle channel time • 1-persistent CSMA rules: • if medium idle, transmit; • if medium busy, listen until idle; then transmit immediately • 1-persistent stations are selfish • if two or more stations waiting, a collision is guaranteed

  9. P-persistent CSMA • a compromise to try and reduce collisions and idle time • p-persistent CSMA rules: • if medium idle, transmit with probability p, and delay one time unit with probability (1–p) • if medium busy, listen until idle and repeat step 1 • if transmission is delayed one time unit, repeat step 1 • issue of choosing effective value of p to avoid instability under heavy load

  10. Value of p? • have n stations waiting to send • at end of tx, expected number of stations is np • if np>1 on average there will be a collision • repeated tx attempts mean collisions likely • eventually when all stations trying to send have continuous collisions hence zero throughput • thus want np<1 for expected peaks of n • if heavy load expected, p small • but smaller p means stations wait longer

  11. CSMA • fig 16.1

  12. Description of CSMA/CD

  13. CSMA/CDOperation

  14. Which Persistence Algorithm? • IEEE 802.3 uses 1-persistent • both nonpersistent and p-persistent have performance problems

  15. Binary Exponential Backoff • for backoff stability, IEEE 802.3 and Ethernet both use binary exponential backoff • stations repeatedly resend when collide • on first 10 attempts, mean random delay doubled • value then remains same for 6 further attempts • after 16 unsuccessful attempts, station gives up and reports error • 1-persistent algorithm with binary exponential backoff efficient over wide range of loads • backoff algorithm has last-in, first-out effect

  16. Collision Detection

  17. IEEE 802.3 MAC Frame Format • Preample: 10101010 … • Start of Frame Delimiter: 10101011 • Length/Type: • If less than or equal to 1500, then the Length/Type field indicates the number of MAC client data octets contained in the subsequent MAC Client Data field • If greater than or equal to 1536 decimal then the Length/Type field indicates the nature of the MAC client protocol (Type interpretation).

  18. Jumbo frame : 9000 bytes payload

  19. A VLAN Configuration

  20. A VLAN Configuration CFI : Canonical format indicator (used for compatibility between Ethernet networks and token ring networks)

  21. 10Mbps Specification(802.3# where #=e,i,…) 10Base5 : link 10Base2 : link

  22. 100Mbps Fast Ethernet • MLT-3 • 4B/5B-NRZI (table) • 8B6T

  23. 100BASE-X • uses a unidirectional data rate 100 Mbps over single twisted pair or optical fiber link • encoding scheme same as FDDI • 4B/5B-NRZI

  24. 100BASE-T4 • 100-Mbps over lower-quality Cat 3 UTP • takes advantage of large installed base • does not transmit continuous signal between packets • useful in battery-powered applications • can not get 100 Mbps on single twisted pair • so data stream split into three separate streams • four twisted pairs used • data transmitted and received using three pairs • two pairs configured for bidirectional transmission • use ternary signaling scheme (8B6T)

  25. Full Duplex Operation • traditional Ethernet half duplex • using full-duplex, station can transmit and receive simultaneously • 100-Mbps Ethernet in full-duplex mode, giving a theoretical transfer rate of 200 Mbps • stations must have full-duplex adapter cards • and must use switching hub • each station constitutes separate collision domain • CSMA/CD algorithm no longer needed • 802.3 MAC frame format used

  26. Mixed Configurations • Fast Ethernet supports mixture of existing 10-Mbps LANs and newer 100-Mbps LANs • supporting older and newer technologies • stationsattach to 10-Mbps hubs using 10BASE-T • hubs connected to switching hubs using 100BASE-T • high-capacity workstations and servers attach directly to 10/100 switches • switches connected to 100-Mbps hubs use 100-Mbps links • 100-Mbps hubs provide building backbone • connected torouter providing connection to WAN

  27. Gigabit Ethernet Configuration

  28. Gigabit Ethernet - Differences • Carrier extension • at least 4096 bit-times long (512 bit-times for 10/100 Mbps) • Frame bursting (for a small number of frames) • The last two features are not needed if a switched hub is used to provide dedicated media access

  29. Gigabit Ethernet – Physical

  30. Ethernet Switch • Show demo • Cisco Catalyst 3350 series • GBIC (Gigabit Interface Converter)

  31. 10Gbps Ethernet(IEEE 802.3a# where #= e, k, n, p, q) • http://en.wikipedia.org/wiki/10_Gigabit_Ethernet • growing interest in 10Gbps Ethernet • high-speed backbone use • future wider deployment • alternative to ATM and other WAN technologies • uniform technology for LAN, MAN, or WAN • advantages of 10Gbps Ethernet • no expensive, bandwidth-consuming conversion between Ethernet packets and ATM cells • IP and Ethernet together offers QoS and traffic policing approach ATM • have a variety of standard optical interfaces

  32. 10Gbps Ethernet Configurations

  33. 10Gbps Ethernet Options

  34. 10Gbps Ethernet coding 64B/66Bcodingisused (guarantees a bit transition every 66 bits)

  35. 100-Gbps Ethernet(IEEE 802.3ba) • preferred technology for wired LAN • preferred carrier for bridging wireless technologies into local Ethernet networks • cost-effective, reliable and interoperable • popularity of Ethernet technology: • availability of cost-effective products • reliable and interoperable network products • variety of vendors

  36. 100Gbps Ethernet • Standards • defined: • 40Gbps • 100Gbps • Note: • GbE = Gigabit Ethernet

  37. Multilane Distribution used to achieve the required data rates • multilane distribution: • switches implemented as multiple parallel channels • separate physical wires, different frequencies or wave lengths • virtual lanes: • if a different number of lanes are actually in use, virtual lanes are distributed into physical lanes in the PMD (physical medium dependent) sublaver (n. of virtual lanes may not be equal to n. of physical lanes) • form of inverse multiplexing

  38. Multiline Distribution for 100Gbps Ethernet Codingused: 64B/66B VL# : lanenumber ~VL#: bit inverse of VL# Frm # : frame marker (to locate the alignment block)

  39. Multiline Distribution for 100Gbps Ethernet VL# : lanenumber ~VL#: bit inverse of VL# Frm # : frame marker (to locate the alignment block) Multiplexingvirtuallanes to physical media : http://www.ixiacom.com/pdfs/library/white_papers/PCS_white_paper.pdf

  40. Media Options for 40-Gbps and 100-Gbps Ethernet

  41. Summary • traditional Ethernet • high speed LANs emergence • Ethernettechnologies • CSMA & CSMA/CD media access • 10MbpsEthernet • 100MbpsEthernet • 1GbpsEthernet • 10GbpsEthernet • multilane distribution • IEEE 802.1Q VLAN standard

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