Networking tutorials introduction to networking

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  • 1. Networking Tutorials - Introduction to Networking Vinod Jadhav

2. There are a variety of physical and logical network layouts in use today. As a network administrator, you might find yourself working on these different network layouts or topologies and, as such, will require knowledge of how they are designed to function. This tutorial reviews general network considerations such as the various topologies used on today's networks, LANs, PANs, and WANs, and the IEEE standards. LANs, WANs, and PANs Networks are classified according to their geographical coverage and size. The two most common network classifications are local area networks (LANs) and wide area networks 3. LANs A LAN is a data network that is restricted to a single geographical location and typically encompasses a relatively small area such as an office building or school. The function of the LAN is to interconnect workstation computers for the purposes of sharing files and resources. Because of its localized nature, the LAN is typically high speed and cheaper to set up than a WAN. Figure 1.1 shows an example of a LAN. Local area network 4. WANs A WAN is a network that spans more than one geographical location often connecting separated LANs. WANs are slower than LANs and often require additional and costly hardware such as routers, dedicated leased lines, and complicated implementation procedures. Figure 2 shows an example of a WAN 5. PANs Wireless technologies have introduced a new term Wireless Personal Area Networks (WPAN). WPAN refers to the technologies involved in connecting devices in very close proximity to exchange data or resources. An example of this can be seen through connecting a laptop with a PDA to synchronize an address book. Because of their small size and the nature of the data exchange, WPAN devices lend themselves well to ad hoc networking. Ad hoc networks are those that have devices connect directly to each other and not through a wireless access point. Ad hoc wireless networks are discussed later in this chapter. Because of the close proximity of WPAN networking, short-range wireless technologies are typically used. This includes Bluetooth and Infrared. The key WPAN technology supported in Windows XP Professional, for example, is Infrared Data Association (IrDA). In addition, the IEEE wireless standards, including 802.11b/g, can be used to create a WPAN. 6. Network Models There are two basic wired network models from which to choosethe peer-to-peer network model and the client/server model. The model used for a network is determined by several factors, including how the network will be used, how many users will be on the network, and budgetary considerations. 7. Peer-to-peer Networking A peer-to-peer network is a decentralized network model offering no centralized storage of data or centralized control over the sharing of files or resources. All systems on a peer-to-peer network can share the resources on their local computer as well as use resources of other systems. Peer-to-peer networks are cheaper and easier to implement than client/server networks, making them an ideal solution for environments in which budgets are a concern. The peer-to-peer model does not work well with large numbers of computer systems. As a peer-to-peer network grows, it becomes increasingly complicated to navigate and access files and resources connected to each computer because they are distributed throughout the network. Further, the lack of centralized data storage makes it difficult to locate and back up key files. Peer-to-peer networks are typically found in small offices or in residential settings where only a limited number of computers will be attached and only a few files and resources shared. A general rule of thumb is to have no more than 10 computers connected to a peer-to-peer network. 8. Client/Server Networking Model The client/server networking model is, without question, the most widely implemented model and the one you are most likely to encounter when working in real-world environments. The advantages of the client/server system stem from the fact that it is a centralized model. It allows for centralized network management of all network services, including user management, security, and backup procedures. A client/server network often requires technically skilled personnel to implement and manage the network. This and the cost of a dedicated server hardware and software increase the cost of the client/server model. Despite this, the advantages of the centralized management, data storage, administration, and security make it the network model of choice. Table 1 summarizes the characteristics of the peer-to-peer and client/server network models. 9. Table 1 Comparison of Networking Models Attribute Peer-to-Peer Network Client/Server Network Size Restricted to a maximum of 10 computers. The size of the network is limited only by server size and network hardware, and it can have thousands of connected systems. Administration Each individual is responsible for the administration of his or her own system. A administrator is not needed. A skilled network administrator is often required to maintain and manage the network. Security Each individual is responsible for maintaining security for shared files or resources connected to the system. Security is managed from a central location but often requires a skilled administrator to cSorrectly configure. Cost Minimal startup and implementation cost. Requires dedicated equipment and specialized hardware and administration, increasing the cost of the network. Implementation Easy to configure and set up. Often requires complex setup procedures and skilled staff to set up. 10. Centralized and Distributed Computing The terms centralized and distributed computing are used to describe where the network processing takes place. In a centralized computing model, one system provides both the data storage and the processing power for client systems. This networking model is most often associated with computer mainframes and dumb terminals, where no processing or storage capability exists at the workstation. These network environments are rare, but they do still exist. A distributed network model has the processing power distributed between the client systems and the server. Most modern networks use the distributed network model, where client workstations share in the processing responsibilities 11. Distributed Computing 12. Network Topologies A topology refers to both the physical and logical layout of a network. The physical topology of a network refers to the actual layout of the computer cables and other network devices. The logical topology of a network, on the other hand, refers to the way in which the network appears to the devices that use it. Several topologies are in use for networks today. Some of the more common include the bus, ring, star, mesh, and wireless topologies. The following sections provide an overview of each. 13. Bus Topology A bus network uses a trunk or backbone to which all of the computers on the network connect. Systems connect to this backbone using T connectors or taps. To avoid signal reflection, a physical bus topology requires that each end of the physical bus be terminated. Figure 3 shows an example of a physical bus topology. Figure 3 Physical bus topology. 14. Table 2 Advantages and Disadvantages of the Bus Topology Advantages Disadvantages Compared to other topologies, a bus is cheap and easy to implement. There might be network disruption when computers are added or removed. Requires less cable than other topologies. Because all systems on the network connect to a single backbone, a break in the cable will prevent all systems from accessing the network. Does not use any specialized network equipment. Difficult to troubleshoot. The most common implementation of a linear bus is the IEEE 802.3 standard. Table 2 summarizes the advantages and disadvantages of the bus topology. 15. Ring Topology The ring topology is actually a logical ring, meaning that the data travels in circular fashion from one computer to another on the network. It is not a physical ring topology. Figure 4 shows the logical layout of a ring network. Figure 4 Logical design of the ring network. 16. Table 3 Advantages and Disadvantages of the Ring Topology Advantages Disadvantages Cable faults are easily located, making troubleshooting easier. Expansion to the network can cause network disruption. Ring networks are moderately easy to install. A single break in the cable can disrupt the entire network. In a true ring topology, if a single computer or section of cable fails, there is an interruption in the signal. The entire network becomes inaccessible. Network disruption can also occur when computers are added or removed from the network, making it an impractical network design in environments where there is constant change to the network. Ring networks are most commonly wired in a star configuration. In a Token Ring network, a multistation access unit (MSAU) is equivalent to a hub or switch on an Ethernet network. The MSAU performs the token circulation internally. To create the complete ring, the ring in (RI) port on each MSAU is connected to the ring out (RO) port on another MSAU. The last MSAU in the ring is then connected to the first, to complete the ring. Table 3 summarizes the advantages and disadvantages of the ring topology. 17. Star Topology In the star topology, all computers and other network devices connect to a central device called a hub or switch. Each connected device requires a single cable to be connected to the hub, creating a point-to-point connection between the device and the hub. Using a separate cable to connect to the hub allows the network to be expanded without disruption to the network. A break in any single cable will not cause the entire network to fail. Figure 1.5 provides an exam