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Chapter 15: LAN Systems

Chapter 15: LAN Systems. Business Data Communications, 4e. High-Speed LANs. Why? Extraordinary growth in speed, power, and storage capacity of PCs Increasing use of LANs as computing platforms Examples Server farms Workgroups with “power” requirements High-speed backbones.

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Chapter 15: LAN Systems

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  1. Chapter 15:LAN Systems Business Data Communications, 4e

  2. High-Speed LANs • Why? • Extraordinary growth in speed, power, and storage capacity of PCs • Increasing use of LANs as computing platforms • Examples • Server farms • Workgroups with “power” requirements • High-speed backbones Business Data Communications, 4e

  3. Traditional Ethernet • Ethernet and CSMA/CD (IEEE 802.3) • Carrier sense multiple access with collision detection • Four step procedure • If medium is idle, transmit • If medium is busy, listen until idle and then transmit • If collision is detected, cease transmitting • After a collision, wait a random amount of time before retransmitting Business Data Communications, 4e

  4. 802.3 Medium Notation • Notation format:<data rate in Mbps><signaling method><maximum segment length in hundreds of meters> • e.g 10Base5 provides 10Mbps baseband, up to 500 meters • T and F are used in place of segment length for twisted pair and fiber Business Data Communications, 4e

  5. 802.3 10BaseX Media Options Business Data Communications, 4e

  6. Fast Ethernet (100Mbps) • Easy to integrate with existing systems • Can use UTP (-TX) or fiber (-FX) • Uses star-wired topology, using a central multiport repeater (broadcast method) • If NICs support full-duplex mode, switched hub must be used Business Data Communications, 4e

  7. 802.3 100Base-T Options Business Data Communications, 4e

  8. 802.3 100BaseX Media Options Business Data Communications, 4e

  9. Gigabit Ethernet • Still under development • Retains CSMA/CD protocol and Ethernet format, ensuring smooth upgrade path • Uses optical fiber over short distances • 1-gbps switching hub provides backbone connectivity Business Data Communications, 4e

  10. Gigabit Ethernet Media Options Business Data Communications, 4e

  11. Example 100-Mbps Ethernet Backbone Strategy Business Data Communications, 4e

  12. Token Ring LANs (802.5):Medium Access Control • Token “seized” by changing a bit on the circulating frame to indicate start of frame rather than token • Default configuration requires sender to complete transmission and begin receiving transmitted frame before releasing the token • “Early token release” allows release of token after transmission but before receipt of frame Business Data Communications, 4e

  13. 802.5 Transmission Media • Original specified shielded twisted pair with data rates of 4 and 16mbps • New addition to standard allows use of UTP for 4mbps • Utilizes differential Manchester encoding • 1997 update to IEEE 802.5 introduced dedicated token ring (DTR). Business Data Communications, 4e

  14. Fibre Channel • combine the best features of channel and protocol-based technologies • the simplicity and speed of channel communications • the flexibility and inter-connectivity that characterize protocol-based network communications. • more like a traditional circuit-switched or packet-switched network, in contrast to the typical shared-medium LAN Business Data Communications, 4e

  15. Full-duplex links with two fibers per link Performance from 100 Mbps to 800 Mbps on a single link (200 Mbps to1600 Mbps per link) Support for distances up to 10 km Small connectors High-capacity utilization with distance insensitivity Greater connectivity than existing multidrop channels Broad availability (i.e., standard components) Support for multiple cost/performance levels, from small systems to supercomputers Ability to carry multiple existing interface command sets for existing channel and network protocols Fibre Channel Goals Business Data Communications, 4e

  16. Fibre Channel Elements • Nodes • The end systems • Includes one or more N_ ports for interconnection • Fabric • Collection of switching elements s between systems • Each element includes multiple F_ ports • Responsible for buffering and for routing frames between source and destination nodes Business Data Communications, 4e

  17. Fibre ChannelProtocol Architecture • FC-0 Physical Media: Includes optical fiber, coaxial cable, and shielded twisted pair, based on distance requirements • FC-1 Transmission Protocol: Defines the signal encoding scheme • FC-2 Framing Protocol: Defines topologies, frame format, flow/error control, and grouping of frames • FC-3 Common Services: Includes multicasting • FC-4 Mapping: Defines the mapping of various channel and network protocols to Fibre Channel Business Data Communications, 4e

  18. Wireless LANS • LAN extension • Wireless network connected to a main wire-based network • Cross-building interconnect • Point-to-point link between networks in separate buildings • Nomadic access • Wireless link between a LAN hub and a mobile data terminal • Ad hoc networks • a peer-to-peer network (no centralized server) set up temporarily to meet some immediate need. Business Data Communications, 4e

  19. Throughput Number of nodes: Connection to backbone LAN Service area Battery power consumption Transmission robustness and security Co-located network operation License-free operation Handoff/roaming Dynamic configuration Wireless LAN Requirements Business Data Communications, 4e

  20. IEEE 802.11 Standards • Association/Re-Association/Disassociation • Authentication • Privacy • Physical Media • Infrared at 1 or 2 Mbps at a wavelength of 850-950 nm • Direct-sequence spread spectrum in the 2.4-GHz ISM band • Frequency-hopping spread spectrum in the 2.4-GHz ISM band, at data rates of 1 and 2 Mbps. Business Data Communications, 4e

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