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Network+ Guide to Networks 6 th Edition

Network+ Guide to Networks 6 th Edition. Chapter 5 Topologies and Ethernet Standards. Objectives. Describe the basic and hybrid LAN topologies, and their uses, advantages, and disadvantages Describe the backbone structures that form the foundation for most networks

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Network+ Guide to Networks 6 th Edition

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  1. Network+ Guide to Networks6th Edition Chapter 5 Topologies and Ethernet Standards

  2. Objectives • Describe the basic and hybrid LAN topologies, and their uses, advantages, and disadvantages • Describe the backbone structures that form the foundation for most networks • Compare the different types of switching used in data transmission • Explain how nodes on Ethernet networks share a communications channel • Identify the characteristics of several Ethernet standards Network+ Guide to Networks, 6th Edition

  3. Simple Physical Topologies • Physical topology: physical layout of the media, nodes, and devices on a network • It does not specify: • Device types • Connectivity methods • Addressing schemes • Fundamental shapes • Bus, ring, star • Hybrid Network+ Guide to Networks, 6th Edition

  4. Bus • Bus topology • Single cable • Connects all network nodes • No intervening connectivity devices • One shared communication channel (bus) • Physical medium • Coaxial cable (Thinnet & Thicknet) • Passive topology: each node passively listens for, then accepts, data directed to it • Uses broadcast to alert other nodes that a transmission is being sent Network+ Guide to Networks, 6th Edition

  5. Bus (cont’d.) • Terminators • 50-ohm resistors • Stop signal at end of wire • Used to prevent signal bounce • Signal bounce • Signal travels endlessly between two network ends • One end grounded • Removes static electricity that could adversely affect the signal Network+ Guide to Networks, 6th Edition

  6. Figure 5-1 A terminated bus topology network Courtesy Course Technology/Cengage Learning Network+ Guide to Networks, 6th Edition

  7. Bus (cont’d.) • Bus topology advantage • Relatively inexpensive • Disadvantages • Does not scale well • Not very fault tolerant Network+ Guide to Networks, 6th Edition

  8. Ring • Ring topology • Node connects to nearest two nodes • Circular network • Clockwise data transmission • One direction (unidirectional) around ring • Active topology: All workstations participates in data delivery (act as a repeater) vs. broadcasts (Bus) • Physical medium • Twisted pair or fiber-optic cabling Network+ Guide to Networks, 6th Edition

  9. Ring (cont’d.) • Drawbacks • Malfunctioning workstation can disable network • Not very flexible or scalable Figure 5-2 A ring topology network Courtesy Course Technology/Cengage Learning Network+ Guide to Networks, 6th Edition

  10. Star • Star topology: Nodes connects through a central connectivity device • Router or Switch (many years ago hubs were used) • Physical medium • Twisted pair or fiber-optic cabling • Single cable connects only two devices • Advantage • Fault tolerant • Flexible Network+ Guide to Networks, 6th Edition

  11. Star (cont’d.) • Most popular fundamental topology layout • Modern Ethernet networks based on star topology Figure 5-3 A star topology network Courtesy Course Technology/Cengage Learning Network+ Guide to Networks, 6th Edition

  12. Hybrid Topologies • Pure bus, ring, star topologies • Rarely exist because they can be too restrictive • Hybrid topology • More likely • Complex combination of pure topologies Network+ Guide to Networks, 6th Edition

  13. Star-Wired Ring • Star-wired ring topology • Star physical topology • Ring logical topology • Benefit • Star fault tolerance • Token Ring networks • IEEE 802.5 • Multistation Access Unit (MAU) creates a logical ring Network+ Guide to Networks, 6th Edition

  14. Star-Wired Ring (cont’d.) Figure 5-4 A star-wired ring topology network Courtesy Course Technology/Cengage Learning Network+ Guide to Networks, 6th Edition

  15. Star-Wired Bus • Star-wired bus topology • Workstation groups • Star-connected devices • Networked via single bus • Advantage • Covers longer distances • Easily interconnect or isolate different network segments • Basis for modern Ethernet networks Network+ Guide to Networks, 6th Edition

  16. Star-Wired Bus (cont’d.) Figure 5-5 A star-wired bus topology network Courtesy Course Technology/Cengage Learning Network+ Guide to Networks, 6th Edition

  17. Logical Topologies • Refers to way data transmitted between nodes • Rather than physical layout • Does not necessarily match physical topology • Most common logical topologies: bus & ring • Broadcast domain • All nodes connected to single repeating device or switch • Switches can be configured to separate broadcast domains Network+ Guide to Networks, 6th Edition

  18. Backbone Networks • Cabling connecting hubs, switches, & routers (connectivity devices) • Usually higher layer switches & routers • Typically have more throughput • Large organizations • Fiber-optic backbone • Enterprise-wide network backbones • Complex and more difficult to plan • Enterprise: refers to an entire organization, including local and remote offices, a mixture of computer systems, and a number of departments Network+ Guide to Networks, 6th Edition

  19. Serial Backbone • Simplest backbone • Two or more devices • Connect using single medium in daisy-chain fashion • Daisy-chain • Linked series of devices together • Low-cost LAN infrastructure expansion • Easily attach additional switches (connectivity devices) • Modern networks of any size don’t depend on simple serial backbones. Instead, they use a more scalable and fault-tolerant framework such as a distributed backbone Network+ Guide to Networks, 6th Edition

  20. Serial Backbone (cont’d.) • Backbone components • Could daisy chain Gateways& Routers Figure 5-6 A serial backbone Courtesy Course Technology/Cengage Learning Network+ Guide to Networks, 6th Edition

  21. Distributed Backbone • Connectivity devices: connected to one or more central connectivity devices, such as switches or routers, in a hierarchy • Benefit • Simple expansion • A more complicated distributed backbone • Connects multiple LANs using routers Network+ Guide to Networks, 6th Edition

  22. Distributed Backbone (cont’d.) • Additional benefits • Workgroup segregation • Drawback • Potential for single failure points, such as the connectivity devices at the uppermost layers Network+ Guide to Networks, 6th Edition

  23. Figure 5-7 A simple distributed backbone Courtesy Course Technology/Cengage Learning Network+ Guide to Networks, 6th Edition

  24. Figure 5-8 A distributed backbone connecting multiple LANs Courtesy Course Technology/Cengage Learning Network+ Guide to Networks, 6th Edition

  25. Collapsed Backbone • Uses a router or switch as the single central connection point for multiple subnetworks • Highest layer • Single router or switch with multiprocessors to handle the heavy traffic going through it • Risk: Central router failure • Routers may slow data transmission—because they cannot move traffic as quickly as switches Network+ Guide to Networks, 6th Edition

  26. Figure 5-9 A collapsed backbone Courtesy Course Technology/Cengage Learning Network+ Guide to Networks, 6th Edition

  27. Parallel Backbone • Most robust network backbone • More than one central router or switch connects to each network segment • Requires duplicate connections between connectivity devices • Advantage • Redundant links • Increased performance • Better fault tolerance Network+ Guide to Networks, 6th Edition

  28. Figure 5-10 A parallel backbone Courtesy Course Technology/Cengage Learning Network+ Guide to Networks, 6th Edition

  29. Switching • Logical network topology component • Determines connection creation between nodes • Three methods: • Circuit switching • Packet switching • Multiprotocol label switching (MPLS) Network+ Guide to Networks, 6th Edition

  30. Circuit Switching • Connection established between two network nodes • Before transmitting data • Dedicated bandwidth • Data follows same initial path selected by switch • Monopolizes bandwidth while connected • Resource wasted • Uses • Traditional telephone calls Network+ Guide to Networks, 6th Edition

  31. Packet Switching • Most popular • Breaks data into packets before transporting • Packets • Travel any network path to destination • Need not follow each other • Need not arrive in sequence • Reassembled at destination • Advantage of packet switching is that it does not waste bandwidth by holding a connection open until a message reaches its destination, as circuit switching does • Ethernet and the Internet are examples of packet-switched networks Network+ Guide to Networks, 6th Edition

  32. MPLS (Multiprotocol Label Switching) • Introduced by IETF in 1999 • Originally, MPLS was used by ISPs as a way to move traffic through their networks more quickly • Offers potentially faster transmission than packet- or circuit-switched networks • MPLS adds an MPLS label (shim) between Layer 3 and Layer 2 information • MPLS labels can include prioritization information—QoS (quality of service) • QoS is a means of sorting IP packets based on header information—i.e., what might be included in the MPLS header inserted as a label in a frame Network+ Guide to Networks, 6th Edition

  33. MPLS, (cont’d.) • Addresses some limitations of traditional packet switching • Without MPLS each router along the data’s path must interpret the IP datagram’s header to discover its destination address, and then perform a route lookup to determine where to forward the packet next—this slows up the transmission • Using MPLS the first router adds one or more labels called a shim (MPLS label) • MPLS Label (shim) include special addressing and sometimes prioritization information • Routers then only interpret the MPLS labels, which can point to exclusive, predefined data paths • Offers potentially faster transmission than traditionally packet-switched or circuit-switched networks • Router does not have to perform a route lookup—immediately knows where to forward the packets (predefined data paths) • Well suited for WANs Network+ Guide to Networks, 6th Edition

  34. MPLS (cont’d.) • Advantages • Create end-to-end paths • Addresses traditional packet switching limitations • Better QoS (quality of service) Figure 5-11 MPLS shim within a frame Courtesy Course Technology/Cengage Learning Network+ Guide to Networks, 6th Edition

  35. Ethernet • Most popular networking technology used on modern LANs • Benefits • Flexible • Can run on various network media • Offers excellent throughput at a reasonable cost • All variations use a common access method: • CSMA/CD Network+ Guide to Networks, 6th Edition

  36. CSMA/CD (Carrier Sense Multiple Access with Collision Detection) • Access method: controls how nodes access communication channel • Carrier sense • Ethernet NICs listen, wait until they detected (sense) that no other nodes are transmitting data • Multiple access • Several Ethernet nodes can simultaneously monitor traffic and access media Network+ Guide to Networks, 6th Edition

  37. CSMA/CD (cont’d.) • Collision: when two nodes simultaneously check channel, determine it is free, begin transmitting data • Collision detection • Manner that nodes respond to a collision • Requires collision detection routine • Enacted if node detects a collision • Jamming • NIC issues 32-bit sequence • Indicates previous message was faulty Network+ Guide to Networks, 6th Edition

  38. CSMA/CD (cont’d.) • Heavily trafficked network segments collisions are common • Collision rate greater than 5 percent of all traffic is unusual and may point to a problematic NIC or poor cabling on the network • Segment growth: large number of nodes can cause network performance issues Network+ Guide to Networks, 6th Edition

  39. Figure 5-12 CSMA/CD process Courtesy Course Technology/Cengage Learning Network+ Guide to Networks, 6th Edition

  40. CSMA/CD (cont’d.) • Collision domain:is the portion of a network where collisions can occur • Ethernet network design • Repeaters or hubs repeat collisions • Result in larger collision domain • Switches and routers • Separate collision domains Network+ Guide to Networks, 6th Edition

  41. Figure 5-13 Broadcast domains and collision domains Courtesy Course Technology/Cengage Learning Network+ Guide to Networks, 6th Edition

  42. CSMA/CD (cont’d.) • Ethernet cabling distance limitations • Effected by collision domains • Data propagation delay • Data travel time too long and CSMA/CD cannot identify collisions accurately • 100 or 1000 Mbps networks • Three segment maximum connected with two repeating devices • 10 Mbps buses • Five segment maximum connected with four repeating devices Network+ Guide to Networks, 6th Edition

  43. Ethernet Standards for Copper Cable • IEEE Physical layer standards • Specify how signals are transmitted to the media • They differ significantly in signal encoding methods • Encoding methods affect maximum throughput, segment length, wiring requirements Network+ Guide to Networks, 6th Edition

  44. Ethernet Standards for Copper Cable (cont’d.) • 10Base-T • 10 represents maximum throughput: 10 Mbps • Base indicates baseband transmission • T stands for twisted pair • Two pairs of wires: transmit and receive • Full-duplex transmission • Follows 5-4-3 rule of networking • Five network segments • Four repeating devices • Three populated segments maximum Network+ Guide to Networks, 6th Edition

  45. Figure 5-14 A 10Base-T network Courtesy Course Technology/Cengage Learning Network+ Guide to Networks, 6th Edition

  46. Ethernet Standards for Copper Cable (cont’d.) • 100Base-T (Fast Ethernet) • IEEE 802.3u standard • Similarities with 10Base-T • Baseband transmission, star topology, RJ-45 connectors • Supports three network segments maximum • Connected with two repeating devices • 100 meter segment length limit between nodes • 100Base-TX • 100-Mbps throughput over twisted pair • Full-duplex transmission: doubles effective bandwidth Network+ Guide to Networks, 6th Edition

  47. Figure 5-15 A 10Base-T network Courtesy Course Technology/Cengage Learning Network+ Guide to Networks, 6th Edition

  48. Ethernet Standards for Copper Cable (cont’d.) • 1000Base-T (Gigabit Ethernet) • IEEE 802.3ab standard • 1000 represents 1000 Mbps • Base indicates baseband transmission • T indicates twisted pair wiring • Uses all four pairs of wires in Cat 5 or higher cable • To transmit and receive signals • Data encoding scheme: different from 100Base-T • Standards can be combined • Maximum segment length: 100 meters, one repeater Network+ Guide to Networks, 6th Edition

  49. Ethernet Standards for Copper Cable (cont’d.) • 10GBase-T (10 Gbps over twisted pair) • IEEE 802.3an • Pushing limits of twisted pair • Requires Cat 6, 6a, or 7 cabling • Maximum segment length: 100 meters • Benefits • Very fast data transmission • Cheaper than fiber-optic • Uses • Connect network devices or connect servers or workstations to LAN Network+ Guide to Networks, 6th Edition

  50. Ethernet Standards for Fiber-Optic Cable • 100Base-FX (100 Mbps over Fiber) • 100-Mbps throughput, baseband, fiber-optic cabling • Multimode fiber containing at least two strands of fiber • Half-duplex mode • One strand receives; one strand transmits • 412 meters segment length • Full duplex-mode • Both strands send and receive • 2000 meters segment length • IEEE 802.3u standard Network+ Guide to Networks, 6th Edition

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