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Chapter 4 Network Topology and Design 1 Contents ÆPhysical Topologies ÆNetwork Architecture ÆMedia ÆPerformance Considerations ÆLAN Design Model ÆReview Questions 2 Physical Topologies The three most common topologies are the bus, star, and ring. 3 Physical Topologies (cont.) Bus 5 A bus topology connects all stations in a linear fashion, which accounts for the name “linear bus.” Fig. 4-1 illustrates this concept. 4 Physical Topologies (cont.) Bus (cont.) 5The merits of bus topology XIt is inexpensive. YIt is easy to design and implement because the stations are simply daisychained together. 5 Physical Topologies (cont.) Bus (cont.) 5The drawbacks of bus topology XIt is difficult to troubleshoot. YIt requires termination. 6 Physical Topologies (cont.) Star 5 The star network configuration which shown in Fig. 4-2 is the most popular physical topology. 7 Physical Topologies (cont.) Star (cont.) 5The merits of star topology XA break in one cable does not affect all other stations. YIt is easy to troubleshoot. p It does not termination. require 8 Physical Topologies (cont.) Star (cont.) 5The drawbacks of star topology X Hubs are more expensive than bus connectors. YA failure at the hub can affect the entire configuration. pStar topologies use more cable than bus topologies. 9 Physical Topologies (cont.) Ring 5 Ring network configurations are most seen in Token Ring and FDDI (Fiber Data Distributed Interface). 10 Physical Topologies (cont.) Toekn Ring 11 Physical Topologies (cont.) FDDI 12 Physical Topologies (cont.) Ring (cont.) 5The merits of ring topology X It prevents collisions. network oEach station functions as a repeater, so it does not require additional network hardware, such as hubs. 13 Physical Topologies (cont.) 5The drawbacks of ring topology XTo add a station, you must shut down the network temporarily. YA failure at one point can bring down the network. pMaintenance on a ring is more difficult than on a Star topology. 14 Physical Topologies (cont.) Influence of the 5-4-3 Rule on Topologies 5 The IEEE identifies a maximum number of repeaters, segments, and populated segments that can be used on any 10 Mbps Ethernet network. (see Fig. 4-3) 15 Physical Topologies (cont.) 5In Fig. 4-4, one violation of the 5-4-3 rule exists: the separation between St. 3 and Server 1 and Host 2 because six segments and five repeaters exist between these stations. 16 Physical Topologies (cont.) 5 Either the hub and segment of Station 3 must be removed, or the hub and segments of Server 1 and Host 2 must be removed. 17 Contents ÆPhysical Topologies ÆNetwork Architecture ÆMedia ÆPerformance Considerations ÆLAN Design Model ÆReview Questions 18 Network Architecture IEEE 802 5 The IEEE 802 covers issues concerning all types of networks- LAN, MAN, WAN, wireless. 19 Network Architecture (cont.) IEEE 802 (cont.) 5This section covers the following specifications: n802.2: LLC o802.3: CSMA/ CD p802.5: Token Ring q802.11: WLAN 20 Network Architecture (cont.) IEEE 802 (cont.) 5 Please study the contents from pages 121 to 125 by yourself. 21 Contents ÆPhysical Topologies ÆNetwork Architecture ÆMedia ÆPerformance Considerations ÆLAN Design Model ÆReview Questions 22 Media Three types of media commonly used in network: nTwisted-pair Cable oCoaxial Cable pFiber-Optic Cable 23 Media (cont.) Please study the contents from pages 126 to 134 by yourself. 24 Horizontal Cabling Standards Please study the subsection: Horizontal Cabling Standards from pages 134 to 138 by yourself. 25 Contents ÆPhysical Topologies ÆNetwork Architecture ÆMedia ÆPerformance Considerations ÆLAN Design Model ÆReview Questions 26 Performance Considerations When designing a network, you must keep in mind the network performance needs of the customer. 27 Performance Considerations (cont.) Items you should consider include: nConnection speed oUtilization and broadcast traffic pCollisions and contention qResource placement 28 Performance Considerations (cont.) 5 Transmission time 6 For example, the transmission time for a file size 300 MB transmitted under the speed of 56 Kbps is 2,400,000 / 56,00 = 42,857 s (or 11 hrs, 54 mins, and 17 secs) 29 Performance Considerations (cont.) 5 Throughput 6 For example, it takes six minutes for a file size 4 GB completely transmitted. The throughput is calculated by 32,000,000,000 / 360 = 88,888,889 bps 30 Performance Considerations (cont.) 5 Collisions and contention 6 When you are considering upgrading an existing network, you can check the rate of collisions on the network using a protocol analyzer or other network performancemonitoring tools. 31 Performance Considerations (cont.) 5 Resource placement 6 Network users should be on the same network segment as the resources they need to access. (see Fig. 4-14) 32 Testing Cable 33 Testing Cable (cont.) 34 Contents ÆPhysical Topologies ÆNetwork Architecture ÆMedia ÆPerformance Considerations ÆLAN Design Models ÆReview Questions 35 LAN Design Models There are two basic design strategies that are typically followed: 5Mesh design 5Hierarchical design 36 LAN Design Models (cont.) In a mesh design, there is no clear definition of where certain network function are performed. In Fig. 4-24, the mesh is a flat structure in which expansion of the network is done laterally. 37 LAN Design Models (cont.) Hierarchical design, on the other hand, are more structure and defined. These types of designs separate different equipment and network media by their connectivity functions. 38 LAN Design Models (cont.) Compared with a mesh design, a hierarchical design: 5Is easier to manage 5Is easier to troubleshoot 5Has improved scalability 5Allow easier analysis 39 LAN Design Models (cont.) Three hierarchical network models: the three-layer model, the two-layer model, and one-layer model are described in this subsection. 40 LAN Design Models (cont.) Three-layer Network Model 5 The three-layer network model is the most complex of the three models. It contains a core layer, a distribution layer, and an access layer. 41 LAN Design Models (cont.) Three-layer Network Model (cont.) 5 Core layer: Provides WAN connectivity between sites located in different geographical areas. 42 LAN Design Models (cont.) Three-layer Network Model (cont.) 5 Distribution layer: Used to interconnect building with separate LANs on a campus network. 43 LAN Design Models (cont.) Three-layer Network Model (cont.) 5 Access layer: Identifies a LAN or a group of LANs that provides users with access to network services. 44 LAN Design Models (cont.) Three-layer Network Model (cont.) 5 Fig. 4-25 illustrates how each layer would be categorized in a large network. 45 LAN Design Models (cont.) Two-layer Network Model 5 Network administrators use WAN connections to interconnect separate LANs, as shown in Fig. 4-26. 46 LAN Design Models (cont.) One-layer Network Model 5 Smaller networks can employ a one-layer network model strategy. 5 Servers may be distributed across the LAN or placed in one central location. (see Fig. 4-27) 47 Network Management Tools SNMP 5 The Simple Network Management Protocol (SNMP) is a TCP/IP standard protocol included in all major TCP/IP protocol suit. 48 Network Management Tools SNMP (cont.) 5 SNMP is a connectionless protocol that operates at layer 7 of OSI model and port number 161. 49 Network Management Tools (cont.) SNMP (cont.) 50 Contents ÆPhysical Topologies ÆNetwork Architecture ÆMedia ÆPerformance Considerations ÆLAN Design Model ÆReview Questions 51 Review Questions Which of the following UTP cable types are not rated for at least 100 Mbps transmission? (choose 2) A. Cat. 3 B. Cat. 4 C. Cat. 5 D. Cat. 6 Ans: C, D 52 Review Questions (cont.) Which of the following are benefits to installing fiberoptic cable? (choose all that apply) A. Impervious to EMI B. Small diameter C. Easy to install D. Low cost Ans: A, B 53 Review Questions (cont.) Which of the following is the correct specification for wireless technologies? A. 802.3 B. 802.5 C. 802.11 D. 802.4 E. None of the above Ans: C 54 Review Questions (cont.) Which of the following specification defines Token Ring? A. 802.3 B. 802.5 C. 802.11 D. 802.4 E. None of the above Ans: B 55 Review Questions (cont.) Which of the following is an advantage to using the bus topology? A. Centralized connection point B. Low implementation cost C. Easy of troubleshooting D. Fault tolerate Ans: B 56 Review Questions (cont.) Which type of connector is used with twisted-pair cabling? A. BNC B. SC C. T-connectors D. RJ-45 E. None of the above Ans: D 57 Review Questions (cont.) Which of the following cables have shielding that protect them from EMI? (choose all that apply) A. Fiber-optic B. RG-58 C. STP D. UTP Ans: A, B, C 58 Review Questions (cont.) Which wireless technology requires line-of-sight between the transmitter and receiver? A. Spread spectrum B. Direct sequencing C. Frequency hopping D. Infrared E. None of the above Ans: D 59 Review Questions (cont.) The usable distance of the UTP cable between MDF and IDF is ____ meters. Ans: 100 60 Review Questions (cont.) If single-mode fiber-optic cable is used between MDF and IDF, what is the maximum usable distance. Ans: 3,000 meters 61