Business data communications 4e chapter 15

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 Business Data Communic ations, 4e 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 Communic ations, 4e 802.3 Medium Notation ✘ Notation format: ✘ 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 Communic ations, 4e 802.3 10BaseX Media Options Business Data Communic ations, 4e 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 Communic ations, 4e 802.3 100Base-T Options Business Data Communic ations, 4e 802.3 100BaseX Media Options Business Data Communic ations, 4e 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 Communic ations, 4e Gigabit Ethernet Media Options Business Data Communic ations, 4e 10 Example 100-Mbps Ethernet Backbone Strategy Business Data Communic ations, 4e 11 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 Communic ations, 4e 12 802.5 Transmission Media ✘ Original specified shielded twisted pair with data rates of 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 Communic ations, 4e 13 Fibre Channel ✘ combine the best features of channel and protocolbased 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 packetswitched network, in contrast to the typical sharedmedium LAN Business Data Communic ations, 4e 14 Fibre Channel Goals ✘ 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 Business Data Communic ations, 4e 15 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 Communic ations, 4e 16 Fibre Channel Protocol 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 Communic ations, 4e 17 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 Communic ations, 4e 18 Wireless LAN Requirements ✘ 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 Business Data Communic ations, 4e 19 IEEE 802.11 Standards ✘ Association/Re-Association/Disassociation ✘ Authentication ✘ Privacy ✘ Physical Media ✘ Infrared at or 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 and Mbps Business Data Communic ations, 4e 20 ... switched hub must be used Business Data Communic ations, 4e 802.3 100Base-T Options Business Data Communic ations, 4e 802.3 100BaseX Media Options Business Data Communic ations, 4e Gigabit Ethernet... connectivity Business Data Communic ations, 4e Gigabit Ethernet Media Options Business Data Communic ations, 4e 10 Example 100-Mbps Ethernet Backbone Strategy Business Data Communic ations, 4e 11 Token... place of segment length for twisted pair and fiber Business Data Communic ations, 4e 802.3 10BaseX Media Options Business Data Communic ations, 4e Fast Ethernet (100Mbps) ✘ Easy to integrate with