Chapter 4 Network Topology and Design

Contents Physical Topologies Network Architecture Media Performance Considerations LAN Design Model Review Questions

Physical Topologies The three most common topologies are the bus, star, and ring.

Physical Topologies (cont.) Bus A bus topology connects all stations in a linear fashion, which accounts for the name linear bus. Fig. 4-1 illustrates this concept.

Physical Topologies (cont.) Bus (cont.) The merits of bus topology It is inexpensive. It is easy to design and implement because the stations are simply daisychained together.

Physical Topologies (cont.) Bus (cont.) The drawbacks of bus topology It is difficult to troubleshoot. It requires termination.

Physical Topologies (cont.) Star The star network configuration which shown in Fig. 4-2 is the most popular physical topology.

Physical Topologies (cont.) Star (cont.) The merits of star topology A break in one cable does not affect all other stations. It is easy to troubleshoot. It does not require termination.

Physical Topologies (cont.) Star (cont.) The drawbacks of star topology Hubs are more expensive than bus connectors. A failure at the hub can affect the entire configuration. Star topologies use more

Physical Topologies (cont.) Ring Ring network configurations are most seen in Token Ring and FDDI (Fiber Data Distributed Interface).

Physical Topologies (cont.) Toekn Ring

Physical Topologies (cont.) FDDI

Physical Topologies (cont.) Ring (cont.) The merits of ring topology It prevents network collisions. Each station functions as a repeater, so it does not require additional network hardware, such as hubs.

Physical Topologies (cont.) The drawbacks of ring topology To add a station, you must shut down the network temporarily. A failure at one point can bring down the network. Maintenance on a ring is more difficult than on a

Physical Topologies (cont.) Influence of the 5-4-3 Rule on Topologies 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)

Physical Topologies (cont.) In 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.

Physical Topologies (cont.) 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.

Network Architecture IEEE 802 The IEEE 802 covers issues concerning all types of networks- LAN, MAN, WAN, wireless.

Network Architecture (cont.) IEEE 802 (cont.) This section covers the following specifications: 802.2: LLC 802.3: CSMA/ CD 802.5: Token Ring 802.11: WLAN

Network Architecture (cont.) IEEE 802 (cont.) Please study the contents from pages 121 to 125 by yourself.

Media Three types of media commonly used in network: Twisted-pair Cable Coaxial Cable Fiber-Optic Cable

Media (cont.) Please study the contents from pages 126 to 134 by yourself.

Horizontal Cabling Standards Please study the subsection: Horizontal Cabling Standards from pages 134 to 138 by yourself.

Performance Considerations When designing a network, you mustkeep in mind the network performance needs of the customer.

Performance Considerations (cont.) Items you should consider include: Connection speed Utilization and broadcast traffic Collisions and contention Resource placement

Performance Considerations (cont.) Transmission time 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)

Performance Considerations (cont.) Throughput 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

Performance Considerations (cont.) Collisions and contention 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.

Performance Considerations (cont.) Resource placement Network users should be on the same network segment as the resources they need to access. (see Fig. 4-14)

Testing Cable

Testing Cable (cont.)

Contents Physical Topologies Network Architecture Media Performance Considerations LAN Design Models Review Questions

LAN Design Models There are two basic design strategies that are typically followed: Mesh design Hierarchical design

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.

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.

LAN Design Models (cont.) Compared with a mesh design, a hierarchical design: Is easier to manage Is easier to troubleshoot Has improved scalability Allow easier analysis

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.

LAN Design Models (cont.) Three-layer Network Model 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.

LAN Design Models (cont.) Three-layer Network Model (cont.) Core layer: Provides WAN connectivity between sites located in different geographical areas.

LAN Design Models (cont.) Three-layer Network Model (cont.) Distribution layer: Used to interconnect building with separate LANs on a campus network.

LAN Design Models (cont.) Three-layer Network Model (cont.) Access layer: Identifies a LAN or a group of LANs that provides users with access to network services.

LAN Design Models (cont.) Three-layer Network Model (cont.) Fig. 4-25 illustrates how each layer would be categorized in a large network.

LAN Design Models (cont.) Two-layer Network Model Network administrators use WAN connections to interconnect separate LANs, as shown in Fig. 4-26.

LAN Design Models (cont.) One-layer Network Model Smaller networks can employ a one-layer network model strategy. Servers may be distributed across the LAN or placed in one central location. (see Fig. 4-27)

Network Management Tools SNMP The Simple Network Management (SNMP) is a standard included in Protocol TCP/IP protocol all major TCP/IP protocol suit.

Network Management Tools SNMP (cont.) SNMP is a connectionless protocol that operates at layer 7 of OSI model and port number 161.

Network Management Tools (cont.) SNMP (cont.)

Ans: C, D 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: A, B 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: C 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: B 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

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

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

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

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

Review Questions (cont.) The usable distance of the UTP cable between MDF and IDF is meters. Ans: 100

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