Bài giảng Network+ Certification - Chapter 14, Planning the Network

Chapter 14, Planning the Network |1| Chapter Overview A. Determining Network Needs B. Providing Fault Tolerance C. Collecting Essential Information Chapter 14, Lesson 1 Determining Network Needs 1. Evaluating Business Requirements A. The first step in developing a network plan is to understand the requirements of the organization that will run the network and the needs of the people who will use it. |2| B. Why does the organization want a new network installed? 1. You might be providing a network for a new installation that has no existing equipment. 2. You might be asked to network a group of existing stand-alone computers. 3. The organization might have an existing network that it wants to upgrade to a new or different technology. |3| C. What services does the organization want the network to provide? 1. An organization with an existing network (or a group of computers that it wants to connect to a network) probably has a basic idea of what services it wants the network to provide. a. An organization that wants a new installation might know less about what it needs. 2. At the most basic level, organizations usually want their users to be able to access shared drives and printers and connect to the Internet. a. Sharing drives and printers is a fundamental networking task that almost any network technology can provide. b. Computers must run the Transmission Control Protocol/Internet Protocol (TCP/IP) protocols to access the Internet, and they need a router to connect the network to an Internet service provider (ISP). 3. Users often know what they want in a network but do not understand the technical requirements and implementation issues. a. Some organizations might need to maintain elaborate databases, which require powerful servers with fast processors, a lot of memory, and large hard drives. b. Others might need to work with huge graphic images or full-motion video, which require enormous amounts of network bandwidth and a lot of storage. c. A financial company might want to provide users with real-time data feeds for multiple stock markets around the world, which require large amounts of internal bandwidth and high-speed Internet access. 2 Outline, Chapter 14 Network+ Certification, Second Edition d. You must determine what the organization wants and what it can afford, and then try to find a solution that satisfies both requirements. 4. In addition to talking to the heads of organizations about their network needs, it is a good idea to talk with the people who will use the network. a. Example: the owner of a company might decide that the network needs three laser printers. b. The network users can point out the best locations for the printers and request a printer with an envelope feeder to save the time they spend manually feeding envelopes. 2. Evaluating the Installation Site |4| A. A proper site evaluation helps you to choose 1. What type of network to install 2. What network medium to use 3. How to install the network |5| B. Distances between components 1. Understanding where the various computers and other network components must be located in relation to each other is a crucial part of the site evaluation. 2. Know the maximum distances supported by the protocols you will use. a. On a typical 10Base-T or 100Base-TX Ethernet network, computers can be up to 100 meters away from the hub. (1) A distance of 100 meters is far more than necessary in the average office networking environment. 3. Be sure to consider the actual route that your cables will take, not just the distance between the components. a. Cables must often snake up through a wall, through ceilings, around lighting fixtures, around doorways and other obstacles, and back down through another wall to complete a connection. b. You might need a cable that is much longer than the walking distance from a computer to the hub. c. Note where you might connect computers that are far apart, on different floors, or even in different buildings. (1) You might need to consider a fiber optic networking solution, which can span longer distances and run safely outdoors. 4. Consider the obstacles between the computers that are to be connected to the network. a. If the network will consist of computers that are all in a single room, you might be able to network them with prefabricated cables running loose around the perimeter of the room. b. You must plan an internal cable installation if (1) The network will be large (2) The computers are located in many different rooms (3) The site requires the most professional appearance possible c. Considerations for internal cable installations (1) Use bulk cable, installed into ceilings and walls Outline, Chapter 14 3 Network+ Certification, Second Edition (2) All cables are connected to a central patch panel at one end and to individual wall plates at each computer location. (3) Require additional planning, more equipment, and greater expertise (4) Are more expensive than external installations 5. Determine where to put the back-end components, such as hubs, servers, and routers. a. In all but the smallest installations, it is important to secure back-end equipment physically, such as in a locked room or closet, to protect it from damage. b. Depending on the size of the installation, you might need several locking closets to house servers, hubs, and patch panels. c. Large sites might need a full-fledged data center that (1) Contains all of the back-end components (2) Functions as the cabling nexus for an entire building or campus |6| C. Ergonomics 1. Planning a network includes a. Selecting equipment designs that are suitable for the working environment b. Placing equipment where it will be most useful and cause the least distraction 2. Examples a. Move the department laser printer off a user’s desk and onto a printer stand in a central location b. Purchase computers that can easily be placed on the floor or that fit under or beside desks, rather than on them |7| D. Environmental conditions 1. In addition to the physical locations of the network components, you must also be aware of the physical environment they will run in. 2. Be conscious of the climate conditions at all equipment locations and at all times of day. 3. Most office buildings maintain constant levels of temperature and humidity, but there are other important factors to consider. a. Is the climate during working hours maintained around the clock? (1) Some offices shut off the heat and air conditioning at night, and any computer equipment that is left running in a sealed building could easily overheat on a hot summer night or be affected by the cold in winter. b. Equipment closets where servers and other components are located might not be climate controlled. 4. A data center containing a large number of computers, routers, and other heat-producing devices will probably need an independent climate control system to keep the room cool enough. 5. Make sure a source of clean, consistent electrical power is available. 4 Outline, Chapter 14 Network+ Certification, Second Edition a. A data center might require its own electrical circuits to support a lot of equipment in a single location. b. Consider adding surge protection and a backup power supply for the entire installation, such as uninterruptible power supply (UPS) units, or even a backup generator with a failover switch. 6. Not every network installation is located in a comfortable office building. a. Some networks are exposed to extreme environments, such as outdoors or industrial areas that expose the equipment to abnormal amounts of heat or cold, humidity, dust, electromagnetic interference, or chemical vapors. b. Products that enable computers to operate in extreme conditions include (1) Waterproof keyboards (2) Computers with air filtering systems that keep out dust and other contaminants (3) Networking technologies to suit a variety of conditions, such as fiber optic and wireless media |8| E. Sources of interference 1. For internal cable installations, you must examine the anticipated cable locations and routes for possible obstructions and sources of interference. 2. Copper-based cables are highly susceptible to electromagnetic fields caused by fluorescent light fixtures, electric motors, and other types of electrical equipment. a. Even seemingly benign equipment such as television sets, radios, and electric heaters can affect network performance. b. Electromagnetic interference might cause error messages or other network problems. 3. Use cable routes that avoid sources of interference. a. If proper routes are not available, you might have to use cable with additional shielding, or even fiber optic cable, which is not affected by electromagnetic interference. 4. Be aware of the local fire and building codes for cabling. a. You might need to purchase cables with a special plenum-rated sheath to run them through the building’s ventilation spaces (which are called plenums). |9| 3. Selecting Hardware A. After you have determined the organization’s networking needs and evaluated the site, you can start to design the network and select the products needed to construct it. B. Computers 1. For a new network installation, you might be responsible for selecting the computers themselves. a. Select models that can fully support the networking tasks expected of them. Outline, Chapter 14 5 Network+ Certification, Second Edition 2. If you will be networking existing computers, consider their age and whether you need to upgrade them by adding memory or disk space. a. It does not make sense to install a state-of-the-art, high-speed network to connect old 486 computers. b. Depending on the users’ needs and the budget, you might have to settle for a more modest network or purchase new computers. C. Hardware compatibility 1. Compatibility is crucial when you use existing equipment, either an existing network or a group of stand-alone computers. 2. Many of the hardware purchasing decisions you make are based on the protocols you choose to run, especially at the data-link layer. 3. Most Ethernet products work well together, even when they are made by different manufacturers. a. Be sure that the products you select all support the same type of Ethernet. b. Example: when expanding an existing network, you might want to (1) Purchase dual-speed network interface cards (NICs) for the new computers and use Fast Ethernet (2) Leave the 10-Mbps NICs in the existing computers and upgrade them from regular Ethernet later c. In the preceding example, you must also purchase a dual-speed hub because, although a Fast Ethernet hub can support the new computers at 100 Mbps, it cannot support the old computers at 10 Mbps. (1) You cannot connect a 10-Mbps hub to a 100-Mbps hub, so the old and the new computers cannot communicate with each other. (2) A dual-speed hub with ports that can support either Fast Ethernet or regular Ethernet lets you connect all of the computers to one network. 4. Network interface adapters a. Make sure that you purchase NICs that use the appropriate bus type for the computers and the correct connector for your network medium. b. Make sure that network adapter drivers are available for your operating system. 5. When using a particular grade of cable (such as Category 5), be sure that all of the cabling components that carry network signals—including connectors, wall plates, patch panels, and patch cables—are of the same grade. 6 Outline, Chapter 14 Network+ Certification, Second Edition Chapter 14, Lesson 2 Providing Fault Tolerance |10| 1. What Is Fault Tolerance? A. Depending on the organization, an equipment failure or other service interruption can mean lost productivity, lost revenue, and, in some cases, even lost lives. B. Fault-tolerance mechanisms enable a computer or a network to continue operating despite the failure of a major compoment. 1. When network functions are absolutely critical, such as in hospitals or airport control towers, the fault-tolerance mechanisms can be incredibly elaborate. 2. In most cases, however, fault-tolerance mechanisms protect only a few key components from outages due to hardware or software faults. 2. Data Availability A. Many organizations must have their data available at all times. B. If a drive on a server fails, you can probably restore the data from a backup, but the time lost replacing the drive and restoring the data can mean lost productivity. C. Some of the hardware technologies used to provide greater data availability are mirroring, duplexing, volumes, disk striping, RAID, network attached storage (NAS), and Storage Area Networks (SANs). |11| 1. Mirroring a. An arrangement in which two identical hard drives connected to a single host adapter always contain identical data (1) The two drives appear to users as one logical drive. (2) Whenever users save data to the mirror set, the computer writes it to both drives simultaneously. (3) If one hard drive unit fails, the other takes over immediately until the malfunctioning drive is replaced. b. Many operating systems, including Windows 2000, Microsoft Windows NT, and Novell NetWare, support disk mirroring. c. Two main drawbacks of this technique: (1) The server provides only half of its available disk space to users. (2) Although mirroring protects against a drive failure, a failure of the host adapter or the computer can still render the data unavailable. |12| 2. Duplexing a. Disk duplexing provides a higher degree of data availability than mirroring because it uses duplicate host adapters as well as disk drives. b. Identical disk drives on separate host adapters maintain exact copies of the same data, creating a single logical drive, just as in disk mirroring. Outline, Chapter 14 7 Network+ Certification, Second Edition c. Allows the server to survive either a disk failure or a host adapter failure and still make its data available to users |13| 3. Volumes a. A volume is a fixed amount of data storage space on a hard drive or other storage device. (1) On a typical computer, the hard drive may be broken up into multiple volumes to separate data into discrete storage units. (2) Example: if you have drive C and drive D on your computer, these two letters can refer to two different hard drives or to two volumes on a single drive. b. Network servers function in the same way, but with greater flexibility. You can create (1) Multiple volumes on a single drive (2) A single volume out of multiple drives (called drive spanning) c. Drive spanning makes all of the storage space on multiple drives in a server appear as a single entity. d. Drive spanning has a drawback: if one of the hard drives containing part of the volume fails, the whole volume is lost. |14| 4. Disk striping a. A method in which you create a single volume by combining the storage on two or more drives and writing data alternately to each one b. When you use disk striping, the computer splits each file into multiple segments and writes alternate segments to each disk. (1) Normally, a spanned volume stores whole files on each disk. c. Advantage of striped volumes (1) Speeds up data access by enabling one drive to read a segment while the other drive’s heads are moving to the next segment (2) Servers often process dozens of file access requests at once (from various users), so disk striping can improve speed significantly. d. Disadvantages of striped volumes (1) Striped volumes are subject to the same problems as spanned volumes. (2) If one drive in the stripe set fails, the entire volume is lost. |15| 5. Redundant array of independent disks (RAID) a. A comprehensive data availability technology with various levels that provide all of the functions of mirroring, duplexing, volumes, and disk striping. b. Higher RAID levels store error correction information along with the data. (1) Even if a drive in a RAID array fails, its data still remains available from the other drives. c. Although RAID is available as a software product that works with standard disk drives, many high-end servers use dedicated RAID drive arrays, which (1) Consist of multiple hard drive units in a single housing 8 Outline, Chapter 14 Network+ Certification, Second Edition (2) Often have hot swap capability (a) Hot swapping is the ability to remove and replace a malfunctioning drive without shutting off the other drives in the array. (b) In hot swapping, the data remains continuously available to network users, even when the support staff is repairing a drive. |19| 6. Network attached storage (NAS) a. Uses a dedicated storage appliance that connects directly to the network and contains its own embedded operating system b. Essentially a multiplatform file server c. Computers on the network can access the NAS appliance in a variety of ways. |20| 7. Storage Area Networks (SANs) a. A SAN is a separate network installed at a local area network (LAN) site that connects servers to disk arrays and other network storage devices. b. This makes it possible to use dedicated storage hardware arrays without overloading the client network with storage-related traffic. c. SANs typically use the Fibre Channel protocol to communicate, but they can theoretically use any network medium and protocol. D. None of these data availability techniques are intended to replace regular backups using a device such as a tape drive. 3. Server Availability A. Technologies similar to specialized data availability techniques can make servers more reliable. 1. Some servers take the concept of hot swapping to the next level by providing redundant components that you can remove and replace without shutting down the entire computer. a. Examples: fan assemblies and various types of drives B. The ultimate solution for server fault tolerance is to have more than one server. C. Various server duplication technologies enable multiple computers to operate as one, so that if one server fails, another immediately takes its place. |21| 1. Novell NetWare SFT III a. One of the first commercially successful server duplication technologies b. NetWare SFT III is a version of NetWare that consists of two copies of the network operating system, plus a proprietary hardware connection that links the two separate server computers. (1) The servers run an application that synchronizes their activities. (2) When a user saves data to one server volume, the data is written to both servers at the same time. Outline, Chapter 14 9 Network+ Certification, Second Edition (3) If one of the servers should malfunction for any reason, the other server instantly takes its place. c. SFT III is designed solely to provide fault tolerance, but the next generation of this technology, clustering, does more. |23| 2. Clustering a. A technique for interconnecting multiple computers to form a unified computing resource and provide fault tolerance b. A cluster can also (1) Distribute the processing load for specific tasks among the various computers (2) Balance the processing load by allocating client requests to different computers in turn c. To increase the cluster’s speed and efficiency, you can connect another computer to the group. (1) The new computer adds its capabilities to those of the others. d. Both Microsoft and Novell support clustering. (1) Microsoft Windows 2000 Advanced Server and Microsoft Windows NT 4.0 Enterprise Edition (2) Novell NetWare Cluster Services for NetWare 5.1 4. Network Redundancy A. Service interruptions on a network are not always the result of a computer or drive failure; sometimes the network itself is to blame. B. Many larger internetworks include redundant components that allow traffic to reach a destination in more than one way. 1. If a network cable is cut or broken, or if a router or switch fails, redundant equipment enables data to take another path to its destination. 2. Typically, you have at least two routers or switches connected to each network, so that the computers can use either one as a gateway to the other segments. |25| a. For example, you can build an internetwork with two backbones, as shown on Slide 25. (1) Each workstation can use either of the routers on its local segment as a gateway. (2) You can also use this arrangement to balance the traffic on the two backbones by configuring half of the computers on each LAN to use one of the routers as their default gateway and the other half to use the other router. Chapter 14, Lesson 3 Collecting Essential Information |26| 1. Standardizing Workstation Configurations A. Many network administrators create a great deal of additional work for themselves by letting the configuration of the network evolve on its own. 10 Outline, Chapter 14 Network+ Certification, Second Edition 1. Allowing users to install and configure their own software might make them happy at first, but when something goes wrong later on, the network administrator is responsible for fixing the problem. 2. If the administrator does not know anything about the configuration of the user’s workstation, the job is much harder. B. Creating a standard workstation configuration for all users simplifies the troubleshooting process, because all of the computers are functionally the same. C. A workstation configuration can include any or all of the following elements: 1. Which applications are installed 2. Where the applications are installed 3. Where the users will store data files 4. Drive letter mappings for shared network drives 5. Local drive sharing parameters 6. Printer connections D. The ideal situation when deploying new network workstations is to make them completely identical, with one exception: 1. Parameters such as computer names and Internet Protocol (IP) addresses must be unique. E. Many administrators use a disk imaging program to build new workstations. F. Disk imaging creates bit-for-bit copies of a drive’s contents and makes it possible to create identically configured computers. 1. If several users have different requirements, you might need to create several different workstation configurations. G. With standard configurations, when a problem arises because of a hardware failure or user error, you can easily correct it. 1. In the worst-case scenario, you can completely restore the computer to its base configuration. 2. Selecting TCP/IP Parameters A. Configuring TCP/IP clients is a problematic aspect of building a new network because you cannot create an identical configuration for every workstation. 1. Every computer on the network must have a unique IP address. 2. Other parameters, such as the default gateway, can vary depending on the computer’s location. |27| B. The primary task in developing a TCP/IP configuration for your network is to select IP addresses. 1. The IP addresses you assign to your computers depend on many factors, including the following: a. How many computers are there? b. How many network segments are there? c. Will you connect the network to the Internet? d. If so, how will you connect the network to the Internet? Outline, Chapter 14 11 Network+ Certification, Second Edition e. Will your new computers interact with existing computers? 2. In most cases, it is a good idea to use private, unregistered network addresses for your computers, such as those discussed in Lesson 2 of Chapter 8, “TCP/IP Fundamentals.” a. When the network is connected to the Internet, use these addresses to protect the computers from unauthorized access. b. To use private addresses on an Internet-connected network, you must provide a way for users to access Internet services, such as network address translation (NAT) or a proxy server. c. If you want to use registered IP addresses (to make your computers visible from the Internet), you must obtain a range of addresses from your ISP. |28| C. Additional TCP/IP configuration issues 1. What routers should your workstations use as their default gateways? 2. Which Domain Name System (DNS) servers should the workstations use? 3. Should you run Windows Internet Name Service (WINS)? D. After you have determined what parameters you will assign to each workstation, you must create individual address assignments for each computer and choose a method for keeping track of them. 1. You will probably add more computers to the network someday, and you will need to know then which addresses are available. 2. The most convenient method for assigning and tracking TCP/IP configuration parameters is to use DHCP. 3. Even if you want to assign a specific address to each computer permanently, DHCP is an excellent tool for keeping track of the assignments and determining which computer is using which address. |29| 3. Creating Accounts A. Other important elements of network configuration that you should plan are the computer names, user account names, and administrative accounts and passwords. B. Assigning computer names 1. The best way to assign computer names and account names is to develop a formula and stick to it. a. Example: you can create computer names that use codes to represent the subnet the computer is located on or the physical location of the computer in the building. (1) Example: the name 3FLRNW9 might represent computer number nine in the northwest corner of the building’s third floor. b. Do not assign computer names based on the names of their users. (1) You do not want to change the name of the computer whenever someone new uses it. C. Assigning user account names 12 Outline, Chapter 14 Network+ Certification, Second Edition 1. For user account names, combining the user’s initials and several letters of the first and last name is appropriate. a. Example: using the first initial and the first five letters of the surname makes David Jaffe’s user name DJAFFE. b. In smaller companies, you might want to use the first name and last initial, as in DAVIDJ, but that can cause conflicts when, for example, David Jaffe and David Johnson work in the same department. D. You must also set a policy for the administrative accounts for your network and their passwords. 1. Depending on the network operating system you intend to use and the network configuration, you might need to create individual administrative accounts on many different computers (or possibly all of them). 2. Use the same password for these administrative accounts so that you are not locked out while you look up one of many passwords. E. In addition to creating individual user accounts, you must also decide which groups or organizational units you want to create to administer the accounts most efficiently. F. If you will use a hierarchical directory service, such as the Microsoft Active Directory service or Novell Directory Services (NDS), planning the directory tree is a complex undertaking. |30| Chapter Summary A. Determining network needs 1. Consult with both management and staff to determine what network services are required when you are planning a network installation. 2. Evaluate the site where the network is to be located to determine what type of network to install, what network medium to use, and how to install the network. 3. Check distances between network components, environmental conditions, local building codes, and possible sources of structural and electromagnetic interference. 4. Select network hardware carefully to ensure that all products are compatible. |31| B. Providing fault tolerance 1. Networks use a variety of data storage techniques to increase the efficiency and fault tolerance of the network storage subsystem. 2. Creating redundant paths through the network enables communications to continue, even if a cable breaks or a router fails. C. Collecting essential information 1. Creating standard workstation configurations simplifies the process of supporting the computers later. 2. Before installing the network, you must decide what IP addresses you will use and how you will assign them. 3. The best way to assign computer names and user account names is to develop a formula and use it consistently.