INFORMATION SYSTEMS TECHNICIAN TRAINING SERIES, MODULE 03--NETWORK COMMUNICATIONS

token-passing access method. However, we cannot connect a CSMA/CD segment to a token-passing segment. Bridges Bridges handle the first two layers of the OSI model—the physical layer and the data link layer. Like repeaters, bridges connect physically-isolated networks to forma single logical network; however, a bridge has a little more intelligence and can provide some translation between dissimilar protocols. For example, our token-passing segment wants to communicate with our CSMA/CD segment. The bridge will “repackage” the message from the token-passing segment into a format that the CSMA/CD segment will understand. Then, the bridge will act as a workstation on the CSMA/CD segment and contend for access. The same thing happens in reverse. A message is sent from the CSMA/CD segment to the token-passing segment. The bridge then “repackages” the message into a format the token-passing segment is expecting and waits for the token, just like any other workstation. An important point to remember is that a bridge will pass on any message it receives. Because the bridge is not smart enough to know that unlike LANs do not understand each other, it will go ahead and send the message. Because the two LANs speak a different “language,” the message will be ignored. Routers Routers only connect networks running similar access methods. They work at the third layer of the OSI model—the network layer. Like bridges and repeaters, routers can connect networks over different wiring media and topologies. However, unlike bridges, routers can intelligently determine the most efficient path to any destination, based on predetermined delimiters. Routers are often a better choice for interconnecting remote installations and congested networks requiring a single protocol. Let’s look at this more closely. Let’s say we have a LAN made up of three token- passing segments, and each segment is connected via a bridge. For a message to go from LAN A to LAN C, it would have to travel through LAN A and LAN B before it reaches its final destination, which is LAN C. See figure 2-2, frame A. On a LAN that has large amounts of message traffic, we can see how a bridge may slow down the system. On the other hand, if the segments are separated by routers, the router on LAN A would look at the destination of the message and determine the direct route to LAN C that would be shortest route, as shown in figure 2-2, frame B. Brouters A brouter can work in either the second and third layers of the OSI model—the data link layer or the network layer. A brouter is a combination of a bridge and router combined. If it can’t route a packet, it acts as a bridge. Brouters are particularly useful if you have two or more different networks. Working as a bridge, a brouter is protocol independent and can be used to filter local are a network traffic. Working as a router, a brouter is capable of routing packets across networks. Gateways Gateways work at OSI model layer 7—the application layer. A gateway functions to reconcile differences between two dissimilar networks. Messages are not only repackaged for transmission between different networks (CSMA/CD to token- passing), but the contents of the messages are converted into a format the destination can use and understand. Now our unlike LANs can talk to each other. Gateways can also provide links between microcomputer networks and mainframes. A gateway is generally a dedicated computer with an interface card and at least some type of software for both of the environments being connected. The gateway then runs special software that provides the necessary conversion and translation services which, in turn, allow the two environments to communicate. Figure 2-2.—Interconnecting LANS using (A) bridges and (B) routers. 2-2

Concentrators The main function of a concentrator is to serve as a termination point for cable running from individual nodes in a network. The cable connects to the network or to another wire center. A concentrator may have multiple boards or boxes mounted on a rack. Each board is essentially a hub, a wiring center for a single network’s nodes. Such boards generally include light-emitting diodes (LEDs) to indicate the status of each port on the board. Hubs A hub is a box with a number of connectors to which multiple nodes (PCs) are attached. It serves as a common termination point that can relay signals along the appropriate paths. All hubs provide connectivity, and some even provide management capabilities. A hub usually connects nodes that have a common architecture. Although the boundary between concentrators and hubs is not always clear, hubs are generally simpler and cheaper than concentrators. Modems In module 2, we introduced you to modems and how they are used in a data communications environment. They translate data from digital to analog form at the sending end of the communications path and from analog to digital at the receiving end. From a conceptual standpoint, this explanation is sufficient. However, if you are going to install a modem, you need MODEMS AT WORK.— Put simply, the object of a modem is to change the characteristics of a simple sine wave, referred to as a carrier signal. We know this carrier signal has several properties that can be altered to represent data. It has amplitude (height); it has frequency (a unit of time); and it has phase (a relative starting point). Modems are capable of altering one or more of these characteristics to represent data. The job a modem performs can be divided into two discrete parts or phases at each end of the communications link. At the sending end, it converts digital bit streams (strings of 0’s and 1’s) into analog sine waves. This is the encoding process. Another component within the modem then changes (modulates) the analog signal so the data may be transmitted simultaneously with other data and voice traffic that has also been modulated. This process is basically reversed at the receiving end. There, the analog signal is brought back to its basic level (demodulated), and the analog sine waves are reconverted (decoded) back into their corresponding bit streams (see figure 2-3). CODECs.— In today’s digital communications lines, voice traffic is considered the outsider that digital data used to be to analog lines. Voice can enter the data communications lines only after being encoded into digital form. It then must be decoded to be audible again at the receiving end. The device used to perform the encoding and decoding functions is known as a codec. This is simply another black box conversion device that has always been in existence in a slightly different form to know some of the technical aspects of modems. as part of a modem. Figure 2-3.—Digital data as it is encoded, modulated, transmitted, demodulated, and decoded. 2-3

Network Interface Card and Cabling To attach personal computers to the LAN, you must install a network interface card (NIC) into an empty expansion slot in the PC, install the appropriate software, and attach the network cable to the NIC. The other item you need to consider is what type of connector to use. But before deciding the type of connector to use, you need to know what type of cable and architecture you will be using. The cables may be twisted-pair cable, fiber optic cable, or coaxial cable. Twisted-pair cable The twisted-pair cable is easy to install and costs little on a per-foot basis. In some cases existing telephone cable may be used. Its disadvantages include limitations in capacity and speed. It is also susceptible to electrical interference unless it is shielded. Fiber optic cable Fiber optic cable is the best choice if a secure network is needed. Because the cable transmits light, the transmissions are immune to interference caused by electrical or electronic devices. Also, if your network will run through an area of heavy industrial activity or a work place with strong radio frequency interference, fiber optic cable is the most appropriate choice. Other advantages of the fiberoptic cable are that it lasts longer than other cable and can carry many more channels. Its disadvantages include its high price, poor connectivity, and low flexibility. Coaxial cable Coaxial cable, also called coax, networks have gained in popularity because of their use in cable television. The quantities of cable and connectors produced for cable television have greatly reduced the prices of these components for network users. Coaxial cable comes in various thicknesses and is designated by a number: RG-11, RG-58, RG-59, RG-62, etc. You can use either baseband or broadband transmission methods with coaxial cable. Baseband coaxial systems, which transmit digital signals unchanged over a single channel, have several advantages. They are inexpensive, simple, easy to install, and have low maintenance. They also allow very high data transmission rates. One disadvantage is they are limited to transmitting digital signals only. In contrast, broadband coaxial systems require the digital signal to be converted to an analog signal before transmission and then back to digital by modem at the receiving device. Broadband systems support data, voice, and video signals that may be transmitted simultaneously. Disadvantages of broadband systems are their higher installation costs and complex maintenance. Connectors The connector provides the physical link between two components. For example, a connector can link a cable and a NIC, a cable and a transceiver, or two cable segments. Connectors differ in their shape, size, gender, connection mechanism, and function. These features influence and determine where a connector can be used. Where necessary, special adapters may be used for connections involving different connector combinations. Connectors also differ in how sturdy they are, how easily and how often they can be attached and detached, and in how much signal loss there is at the connection point. The type of connector needed in a particular situation depends on the components involved and, for networks, on the type of cable and architecture being used. CONNECTOR FUNCTIONS.— A connector may be passing the signal along or absorbing it. A connector that passes a signal along may pass it unmodified or may clean and boost it. Connectors can serve a variety of purposes, including the following: Connect equal components, such as two segments of thin coaxial cable Connect almost equal components, such as thin to thick coaxial cable Connect unequal components, such as coaxial to twisted-pair cable Connect complementary components, such as a NIC to a network Terminate a segment CONNECTOR SHAPES.— Specially shaped connectors are used for particular types of connections or for connections in particular locations. For example, a T-connector attaches a device to a cable segment; an elbow connector allows wiring to meet in a corner or at a wall. 2-4

Figure 2-4.—Connector shapes. Table 2-1.—Cable connector shapes. The connector shapes used in networking setups are listed in table 2-1. Figure 2-4 shows examples of connector shapes. FIBER-OPTIC CONNECTORS.— Like electrical cable connectors, different types of fiber- optic connectors have different kinds of attachment mechanisms. The actual attachments between ferrule shells may be made by threading, snapping, or clicking. Table 2-2 lists the most commons types of fiber-optic connectors. Table 2-2.—Fiber-optic connectors. In addition to attachment mechanisms, fiber-optic connectors differ in the following ways: The size of the ferrule. Whether the connector can be keyed. This is the technique for making a connector asymmetrical, usually by adding a notch or plug, making it impossible to plug the connector in wrong. The number of matings the connectors can handle without producing unacceptable signal loss. 2-5

Whether the fiber must be twisted to make the INSPECTING COMPONENTS connection; multiple fibers cannot run through the same connector if it is to be twisted. The connectors differ in the way the fiber is attached to the connector itself. You can either use epoxy to glue the fiber into the connector, or you can crimp the connector and the ferrule together using a special crimping tool. CONNECTOR GENDERS.— Connector gender basically refers to whether a connector has plugs or sockets. The gender is important because the elements being connected must have complementary genders. A male connector is known as a plug; the female connector is known as a jack. With a few exceptions, such as the IBM® data connectors and certain fiber- optic connectors, all connector types have distinct genders. Figure 2-5 shows examples of male and female connectors. CONNECTOR MECHANISMS.— The connection mechanism defines how the physical contact is made to allow the signal to pass from one side of the connection to the other. Connection mechanisms differ in how sturdy they are. For example, the pin-and-socket connection at a serial port can be wobbly without extra support from the screws on either side of the plug. On the other hand, fiber-optic connectors must be cut to precise proportions and must not allow any play in the connection. The inspection of the components when they are received is limited to checking for any physical damage. This damage will include: Any damage to the packing material Damage to the case Hidden damage on the inside of the cabinet The inspection that is conducted needs to be as thorough as possible, since any damage discovered must be reported to the supplier. This inspection also needs to be accomplished as soon as the equipment arrives, because the longer you wait, the less likely it becomes that the supplier will replace the equipment. NETWORK TESTING Network testing is changing significantly because of the growth of digital network capability. Testing in the voice network has always been considered as much of an art as a science because of the variable nature of the different impairments encountered. The digital net work has been designed with more diagnostic capability, making it much easier to identify and isolate problems. The testing is done in the carrier environment, not in the user environment. Network Testing Methods There are three basic approaches to network testing, as follows: Figure 2-5.—Connector genders. 2-6

1. Rely on vendors. If you rely on a vendor for testing, you probably have a single vendor’s products in your network and are, therefore, locked into that vendor. Fewer vendors today are capable of providing this complete capability. 2. Use an organization dedicated to network problem solving (third party). At one time, third-party problem solving was considered a viable alternative, but today the expertise needed is so vast and covers such a wide variety of products that it is not feasible to provide the service. The carrier providing the majority of your circuits is the best for handling your network management. However, it is difficult for the carrier to be objective, and it is usually not very cost effective. 3. Use in-house network management. In-house network control is by far the most flexible in design and operation. Network administrators typically understand their problems better than any carrier or vendor could. Network problems are not always the result of network conditions; they may actually be operational problems. A disadvantage of in-house network control is that it requires more resources, such as knowledgeable people, equipment, space, and all of the other support overhead. Regardless of the testing method that is used, testing can be performed by both hardware tools and software programs. Hardware Testing The tools used are partly insurance and partly convenience devices. The greatest expense of a network comes when it is down or functioning incorrectly; it is important to be able to test components when things go wrong. Testing should also be accomplished before installing, to ensure that you do not install a faulty component. After they are installed, test components periodically to make sure they are functioning properly. Special tool are available for this purpose. Network testers can be very expensive, while convenience tools, such as wire crimpers and voltmeters, are quite inexpensive. The amount that is spent on tools will depend on the size of the network, the importance of the network’s contents, and who will be doing the maintenance on the network. The following are several types of hardware tools: Manufacturing tools for creating individual components, such as crimpers and dies for attaching wires to connectors. Construction tools for assembling and disassembling systems; for example, screwdrivers, pliers, chip removers, and chip installers. Testing tools for testing individual components or for monitoring the performance of a component or system, such as voltmeters, ammeters, and line scanners. Safety tools for making sure components are protected against damage from electrical and other dangers; for example, static cords, electrical mats, and shorting probes. BASIC TOOLS.— The level and range of tools you will need depends on the level of your involvement with the network. Regardless of the level, a few basic tools will almost certainly make your life easier: Screwdrivers, for opening machines, installing and removing expansion cards, and for attaching connectors; Pliers, for grasping objects; Wrenches or nut drivers, for tightening and loosening nuts; Chip removers/installers, for removing and installing computer chips; and Tweezers, for retrieving small parts and screws. In addition to these tools, some people might also have wire strippers, cutters, and soldering irons that can be used to set up special-purpose circuits or wiring connectors. If you are going to do any troubleshooting at all, you will need a voltmeter or ammeter (probably both), with an operator’s manual, to test the electrical activity. Use of the manual is essential to connect the meter properly; connecting the meter wrong can cause serious damage to sensitive circuitry. TOOLS FOR INSTALLING AND ATTACHING CABLE.— The tools used in making cables are specialized tools. They are used to attach the connectors onto the cable and then to test the cable. It is advisable to get the cables pre-made to the desired length by the manufacturer. Unfortunately, that isn’t always possible. To attach connectors to cable, you need the following tools: 2-7

a crimping tool, for pressing the cable and connector together, and a die for the specified cable/connection pair, to make sure cable and connector fit properly. Installation tool kits that include the crimping tool, die, cable, connectors, and cable ties can be purchased from manufacturers. These kits range in price from one or two hundred to several thousand dollars. TOOLS FOR TESTING CABLES.— Voltmeters and ammeters provide readings of voltage and current, or amperage by tapping into the circuit and recording the electrical activity as it occurs. These recorded values may or may not provide the details about what is happening along the lines of the network. Scanners are much more sophisticated testing tools. Some of the capabilities of scanners include the following: Check for faults in a cable. Test a cable’s compliance with network architectures. Monitor performance and electrical activity, given the type of cable and architecture involved. Test the cable’s wiring sequence. Generate and print a summary of the information obtained from the tests. A powerful scanner can test for cable quality, for the quality of the connections between cable segments, or between cable and device. A less poweful scanner will be able to test for noise, crosstalk, signal attenuation, resistance, cable length, and so on. Software Testing Diagnostic software can be used to help anticipate or catch problems early and to help deal with the problems once they have arisen. Network versions of diagnostic software may be expensive, but they can save the system under some circumstances. For example, virus detection software can save hours of reconstruction and reloading the system. Using software to test the hard disk can identify bad disk sectors before data can be written to them and move any data from bad sectors to a safe location. Another use of diagnostic software is performance monitoring and analysis, which involves tracking the networks behavior. This will help to identify 2-8 inefficiencies and bottlenecks, so they can be elimated. While monitoring the system’s performance, keep careful track of the following: Operating costs Threats to security User satisfaction User productivity Track these areas especially during the first few weeks after the network is installed. Do not be surprised if some of these measured indicators change drastically during this period. For example, costs may drop drastically after the startup period, while user satisfaction and productivity may rise after the initial problems are resolved. NETWORK PHYSICAL CONNECTIONS A network connection is a linkage between network elements. Physical connections concern the cables and connectors used to create the physical layout of the network. When building a network, you must first establish the physical connections. NETWORK BACKBONES Backbone cable refers to the cable that forms the main trunk, or backbone, of a network. Individual nodes and other devices may be connected to this cable using special adapters and a separate stretch of cable. Backbone cable is defined by the Electronics Industries Association/Telecommunications Industry Association-568 (EIA/TIA-568) committee as any “behind the scenes” cable; that is, cable running behind walls, in shafts, or under the ground. The EIA/TIA-568 recognizes four types of backbone cable; they are listed in table 2-3. The use of a backbone network to tie together a number of small access networks offers several advantages over the construction of a single large LAN. The various LANs connected to the backbone are able to operate in parallel, providing greater processing efficiency. The multiple-network approach is also more reliable, since each individual LAN can continue operating if one of the access networks, or even the backbone, fails. The backbone network must also be highly reliable, since the greater distances covered may make it difficult to locate and repair faults. The LANs that connect to the backbone must be flexible and low- cost in terms of installation and user connection.

Table 2-3.—Types of backbone cable. Connection to the backbone network may require a bridge, router, gateway, concentrator or hub, depending on the architectures of the various LANs and the backbone itself. The connectors used will also depend on the type of cable used for the backbone. If the backbone is coaxial cable, you would use a T-connector and barrel connectors to make the connection to another cable or a hardware device. The backbone manages the bulk of the traffic, and it may connect several different locations, buildings, and even smaller networks. The backbone often uses a higher-speed protocol than the individual local area network (LAN) segments. One obstacle to a successful backbone network is the high bandwidth that may be required to handle potentially heavy traffic. Because of this consideration, fiber-optic cable is the most sensible cabling for backbone networks. NODES The computers, or nodes, in a network may be used for workstations, servers, or both. PCs need a network interface card (NIC) installed for networking capabilities. The NICs mediate between the computer and the network by doing the necessary processing and translation to enable users to send or receive commands and data over the network. NICs are designed to support a particular network architecture, such as Ethernet® or ARCnet®. To connect a node directly to a backbone, you would use a drop cable for the connection. Nodes are normally connected to the backbone indirectly through a concentrator or a hub rather than with a drop cable. The elements needed to connect a node to a network include the following: Cable: twisted-pair, coaxial, or fiber-optic Wiring centers: hubs or concentrators Intranetwork links: connectors, repeaters, and so on Internetwork links: bridges, routers, gateways, and so on The cable provides a transmission medium, as well as the physical link between the nodes on the network. Connectors and repeaters attach cable sections to each other; connectors and transceivers attach NICs to a cable and, thereby, to the network. Transceivers enable different types of cable to be attached to each other. Terminators absorb a transmission at the end of a network, preventing the signal from traveling back in the other direction on the network. The types of intranetwork links allowed in the network depend on the type of cable used and on the network topology used. Wiring centers serve as a focal point for network elements, and may influence the logical arrangement of nodes on the network. Internetwork links may be bridges, routers, gateways, and soon. Such components serve to connect networks to each other. The type of internetwork link depends on whether the two networks are the same or not, and the amount of translation that is needed. NETWORK SERVER A server is the central computer in a network, and is responsible for managing the network. The server provides some type of network service. It may be hardware, such as a file server, or software, such as network level protocol for a transport level client. The server provides its service to other workstations on the network or to other processes. In a server-based network, the most important hardware server is the fileserver, which controls access to the files and data stored on one or more hard disks. 2-9

A server may be dedicated or nondedicated. Dedicated servers are used only as a server, not as a workstation. Nondedicated servers are used both as a server and a workstation. Networks with a dedicated server are known as server-based networks; those with nondedicated servers are known as peer-to peer networks. DEDICATED SERVERS Dedicated servers cannot be used for ordinary work. In fact, access to the server is often limited to prevent any access by unauthorized users. Most of the high-end network packages assume you are using a dedicated server. If the network has a dedicated server, it is most likely a file server. A dedicated fileserver runs the NOS software, and workstations run smaller programs whose function is to direct user commands to the workstation’s operating system or to the server. Both servers and workstations need NICs to function on the network. NONDEDICATED SERVERS A nondedicated server can be used as a workstation as well as a server. Using a server as a workstation has several disadvantages and is not advisable for larger networks. The following are disadvantages of nondedicated servers as compared to dedicated servers: 2-10 Many of the NOSs that allow the nondedicated server to run with DOS make them extremely slow and clumsy. While most dedicated servers have software that replaces DOS, such systems may also require a separate non-DOS partition on the hard disk. This allows the NOS to arrange and deal with the contents of the partition in a way that optimizes performance. Running applications on a DOS machine while it is also supposed to be running a network can lead to a deadly performance degradation. Certain tasks will tie up a DOS machine, effectively stopping the network until the task is finished. Adequate security is more difficult to maintain on a nondedicated server. SUMMARY In this chapter we discussed the different types of network components and their functions. We described cabling and the connectors used to connect the network hardware. We covered the purpose of the server and the differences between a dedicated and a nondedicated server. Remember, the driving factor for the type of hardware and cabling used is the topology of the network.

CHAPTER 3 NETWORK TROUBLESHOOTING Upon completing this chapter, you should be able to do the following: Describe how to diagnose and isolate problems with LANs. Describe how to troubleshoot network malfunctions. Explain how to test and evaluate the connection of networking system nodes. Explain how to troubleshoot communications line problems. With any network system, you should have a set of error procedures for personnel to follow to handle errors or malfunctions on the system. These error procedures are the steps to be taken when the system is not operating properly. They are different from the error- detection and diagnostic procedures used to isolate and correct transmission problems. A complete set of diagnostic procedures is necessary for the system. The system procedures are used to isolate the problem to the system or subsystem level. Since the facilities of a network may not be in the local area, it is necessary to have a set of test software and equipment with replacement components available for diagnosing and correcting problems. TROUBLESHOOTING LANS As a communications specialist, more than likely you will be expected to know how to troubleshoot problems on LANs. As a troubleshooter, you must be able to identify a wide range of network problems relating to hardware (the data terminal equipment, the communications link, repeaters, gateways, and so on), software (network operating system, applications, and soon), and peopleware (the end user). It will be your job to identify, isolate, and resolve both the simple and complex problems. DIAGNOSTIC TOOLS Normally, a problem can be solved without too much difficulty with the help of diagnostic tools. The best diagnostic tool available is accurate documentation. This documentation should include: Workstation and server configurations All network related software and equipment Location and paths of all wiring Updated records of all equipment and configurations changes With documentation in hand, along with the help of diagnostic software (a network management package or a LAN analyzer), and specialized diagnostic equipment, such as a datascope, a time domain reflectometer (TDR), or a breakout box, the job becomes routine. Classifying the problems and taking the necessary actions to resolve them are an important part of your job as a troubleshooter. However, it is equally important to remember to log all problems according to your activity’s procedures. This will identify recurring problems, provide information for long term solutions, and enhance your command’s training program. ISOLATING PROBLEMS When isolating a problem, consider the three major areas we discussed earlier-the user, the software, and the hardware, usually in that order. The majority of all network-related problems are caused by the user’s actions—operator errors. Users either do not understand how to operate their PC in a networking environment or they are unfamiliar with the application software package they are using. Most of the time you will find yourself responding to user problems and complaints. A user will call, saying such things as the following: 3-1

My terminal/PC is hung up, and I cannot get into the system. My terminal/PC screen suddenly went blank. My temninal/PC keeps coming up with the same error message. My terminal/PC will not allow me to access the disk file. My terminal/PC will not print. It will be your job to determine if the problem is user, software, or hardware related. Whenever you receive a call about a problem, obtain as much information as possible about the person and the problem. Ask the user’s name, phone number, the terminal/PC or node identification number, the nature of the problem, and what, if anything, occurred immediately preceding the problem. In addition, you should ask the user what application he or she was trying to access or currently working with at the time the problem occured. Ask whether other users are experiencing the same or similar problem, did any error messages appear on the screen, and be sure to ask whether the PC was moved before the problem occured. Sometimes moving hardware creates problems—the connector cable may not be seated properly. Once you have received initial information about a problem, it should help you to categorize the problem. Keep in mind most problems are the result of inexperienced users/operators. Because so many different types of errors can occur, it would be impossible for us to list them all, along with the necessary steps to resolve them. However, based on past experiences, we can provide you with some helpful hints and guidelines to follow. If the problem seems to be isolated to one user, it is probably user error; if the problem occurs with a group of users in a common geographic location, the problem is usually related to the cable; and if the problem is network wide, a close look at the network software is in order. Let us take a look at some of the more common problems that frequently occur and their solutions in connection with these three categories. PO3 Frost has just called to report he cannot log on to the LAN. You begin solving the problem by asking some preliminary questions. You find this is the first time PO3 Frost has used the LAN and no one else in his area is experiencing any problems. At this point, you should be able to recognize the problem is more than likely the result of an inexperienced operator (user error). The logical corrective action to take is to walk PO3 Frost through the proper log-on procedures and password security requirements. He follows your instructions and successfully logs onto the LAN. PO3 Frost should have been able to log onto the LAN by following the User’s Guide on LAN operations. You might want to review the guide to make sure it is current and available to all users. A few weeks later PO3 Frost calls again and reports he has been having intermittent problems while logged on to the LAN. Sometimes while he is saving or retrieving data, his machine locks up for no apparent reason. Again, no one in his immediate work area is experiencing problems. After obtaining all the pertinent information available, you believe the problem is faulty hardware. During the save and retrieve operations, a packet is generated and sent through the network interface card, onto the cable, and to its destination. So the two most logical components to check are the cable connections and the network interface card. The diagnostic tools to use are the time domain reflectometer (TDR) to check any breaks on the cable and the diagnostics that come with the interface card. PO3 Frost runs the card diagnostics at the terminal while you check the cable continuity. The network card passes the test, but the TDR detects a continuity break near his location. A LAN technician checks the connectors at the workstation and discovers one of the connectors has worked itself loose. After replacing the connector, the cable is tested again and passes. PO3 Frost logs on to the LAN and experiences no further problems. In this example we eliminated the cable itself because no other user on the cable segment was experiencing problems. Had there been other users also experiencing intermittent failures, then the cable would have immediately been our focal point of testing, since this is the commonality between the users. You arrive at work Tuesday morning and find a stack of messages waiting for you from users experiencing problems while trying to access the word processing program on the LAN. The only thing these users have in common is they all use the same file server. Immediately you focus your attention on the network operating system and software. You call PO3 Door to ask her a few questions before you begin troubleshooting any further. You learn PO3 Door is able to access all application programs on the LAN with the exception of the word processing program. You immediately log on to the network management program and monitor the data traffic. You discover no user has used the word processing program since 3-2

Monday at 1600. The only person authorized to use the LAN after 1600 is PO1 Brush, who is the network administrator. You call PO1 Brush and ask if any changes were made to the word processing program since yesterday. PO1 Brush states he installed a new version of the word processing program on Monday around 2200 to eliminate any work disruptions. You ask him to check the security access to this new version. You find PO1 Brush inadvertently restricted all users from accessing the new version of the word processing program after he removed the old one. He makes the necessary access changes, and everybody is once again happy and able to use the new version. As you can see, there is a pattern to the various types of errors/problems you will encounter. The problems you will be confronted with will range from the simple to the disastrous. They may be user/operator errors, software problems, or hardware malfunctions. Knowing which is sometimes easy. Under other conditions, it may be difficult for you to determine the source of the problem. The important thing is to learn from your past experiences. Keep a list of symptoms, probable causes, and ways you can use to trace a problem to its cause. This will assist you in diagnosing and troubleshooting problems. You will also find users have a tendency to make the same mistakes again and again, especially while they are learning. You can provide them a great service by explaining some of the more common problems they are likely to encounter, the reasons for the problems, and ways to avoid having them happen to them. NETWORK MALFUNCTIONS Any malfunction of the network is going to result in a nonavailability of the system to the users. The diagnosis and fixing of this malfunction becomes a high priority. There are three primary culprits to network malfunctions: component and server failures, and data collisions. COMPONENT FAILURE Component failures are categorized in two categories: hard faults and soft faults. Hard faults are relatively easy to find, and a diagnostic program will diagnose them correctly every time. Soft faults can be difficult to find, because they occur sporadically or only under specific circumstances, rather than every time the memory location is tested. A diagnostic program tests computer hardware and peripheral devices for correct operation. Most computers run a simple set of system checks when the computer is turned on. The PC tests are stored in read-only memory (ROM), and are known as power- on self tests (POSTs). If a POST detects an error condition, the computer will stop and display an error on the screen. Some computers will emit a beep signal to indicate the type of error. One of the best tools to use for network malfunctions is a network analyzer. A network analyzer is a product that can be used to monitor the activity of a network and the stations on it, and to provide daily summaries or long-term trends of network usage and performance. A network analyzer can do tasks such as: Count or filter network traffic. Analyze network activity involving specified protocols or frame structures. Generate, display, and print statistics about network activity, either as they are being generated or in summary form. Send alarms to a network supervisor or network management program if any of the statistics being monitored exceeds predetermined limits. Do trend or pattern analyses of network activity. Network analyzers may be software only or consist of both software and hardware. The latter may include an interface card enabling you to test the network directly. This card may include an on-board processor. Because of their greater capabilities, hardware/software analyzers are more expensive than the software only analyzers. In fact, the prices for the hardware/software analyzers can be several times as high as those for the software only versions. SERVER FAILURE The most obvious sign that the server has failed for some reason is that all users, except root, will not be able to logon to the system. Use the following steps as required to reestablish services: The first and easiest thing to try is to run the system distribution again. This will rebuild the system maps if nothing else is wrong and will allow users access to the system. Shutdown and reboot the system. During the boot process ensure that no failures occur on any of the nodes. 3-3

Verify the domain name. Look for the maps subdirectory; it should be the same as the domain name. If it is not there, you will need to run the system initialization command. If the above fails, ensure that all the files to be mapped are present on the server. If any have been deleted, they will have to be restored from the latest system saves. One of the best ways to avoid server malfunctions is to conduct maintenance on the server. It is important to set up a schedule for your server and strictly adhere to it. To check the hardware, you should do at least the following things: Clean the server carefully but thoroughly. Check cabling and connections for tightness and signs of bending or stress. Do not disconnect connectors unless necessary, since many connectors are rated for a limited number of matings. If possible, check the cabling with a line analyzer. Run thorough diagnostics on the storage medium and on other system components to identify the components that are likely to fail and to deal with these before they actually do fail. Check the quality of your power line by using a line tester. The hardest part of server maintenance is finding the time to conduct the maintenance, since the network will have to be offline to conduct. In many cases, server maintenance will need to be during off peak hours, late night or early morning, when there is little or no use. DATA COLLISIONS A data collision is the simultaneous presence of signals from two nodes on the network. A collision can occur when two nodes each think the network is idle and both start transmitting at the same time. Both packets involved in a collision are broken into fragments and must be retransmitted. Collision Detection To detect for a collision, nodes check the dc voltage on the line. A voltage level of two or more times higher 3-4 than expected indicates a collision, since this means there are multiple signals traveling along the backbone at the same time. In a CSMA/CD (carrier sense multiple access with collision detection) systems, all workstations or nodes attached to the network monitor the transmission medium at all times. When a node needs to send data, it waits until the line is quiet and then transmits. If two or more nodes happen to transmit data at the same instant, a collision occurs. Each node detects the collision and then waits for a variable amount of time (as programmed in the NIC’s microprocessor) before testing the bus again and retransmitting. Since each node waits for a different amount of time, say 10/1000 and 20/1000 of a second, it is very unlikely that the collision will occur a second time. The CSMA/CD detection method is further illustrated in figure 3-1. Collision Avoidance To avoid collisions, nodes can send special signals that indicate a line is being used for a transmission. In a Figure 3-1.—A bus network using the CSMA/CD access method.

CSMA/CA (carrier sense multiple access with collision avoidance) system, the media-access method uses RTS (ready to send) and CTS (clear to send) signals before sending a frame onto the network. A node transmits only after the node has requested access to the line and access has been granted. Other nodes will be aware of the RTS/CTS transmission and will not try to transmit at the same time. RTS.— A hardware signal sent from a potential transmitter to a destination to indicate that the transmitter wishes to begin a transmission. If the receiver is ready, it sends a CTS signal in return. CTS.— A hardware signal sent from a receiver to a transmitter to indicate that the transmitter can begin sending. ACTS signal is generally sent in response to an RTS signal from the transmitter. NETWORK SYSTEM CONNECTIONS The testing and evaluation of network connections is accomplished with the same test equipment that is used to test network components. This equipment includes voltmeters, ammeters, volt-ohm- milliammeters, and line scanners. All of this test equipment checks the voltage, resistance, and current that passes through the cable and the connectors between the network nodes. Any increase or decrease in voltage or current or an increase in the resistance will cause communications problems for the users. Whether the cable is pre-made or you make it, you should always test the cable before it installed into the network. This will alleviate the possibility of installing a bad cable or connector to the system. Any time that you can detect a bad connector will be to your advantage, since each connector has a limited number of connections before it has to be replaced. COMMUNICATION LINE PROBLEMS Communication line problems fall into three general categories: excessive noise, cabling, and backbone connections. With proper testing and precautions, these problems can be taken care of before they happen. EXCESSIVE NOISE Noise is the term for random electrical signals that become part of a transmission, and that serve to make the signal (information) component of the transmission more difficult to identify. Noise can take various forms, including the following: Impulse noise: voltage increases that last for just a short period, usually for only a few milliseconds. White noise: random background noise. Crosstalk: interference on one wire from another. There are limits set on the allowable levels for each of these types of noise. A noise filter can be used to remove random noise from a signal. In a transmission, signal-to-noise ratio (SNR) is the ratio between the signal and noise levels at a given point, usually at the receiving end of the transmission. The SNR value is generally expressed in dB. The SNR can be used to determine how long a cable segment can be before the signal loss is unacceptably high. The SNR also helps to determine whether a particular type of cable will work for the intended use. Cable testers can help determine whether a particular type of cable is appropriate in a specific environment. In general, digital signals have a much higher SNR than analog signals. Because analog signals in a broadband network must be confined to a portion of the total bandwidth, filtering and other signal-cleaning measures are necessary This confinement makes the signal more delicate and subject to distortion. Several types of filtering maybe used to help clean a broadband transmission. The filters are distinguished by the filtering technique they use as well as by where in the transmission process they are applied. For example, filters applied early in the transmission, prior to modulation, are known as baseband or premodulation filters. Those applied after the modulation are known as passband or postmodulation filters. CABLING Cables are good media for signals, but they are not perfect. The signal at the end of the cable should be as loud and clear as at the beginning, but this will not be true. Any transmission consists of signal and noise conponents. Even a digital signal degrades when transmitted over a wire. This is because the binary information must be converted to electrical form for transmission, and because the shape of the electrical signal changes over distance. 3-5

Signal quality degrades for several reasons, including attenuation, crosstalk, and impedance. Attenuation Attenuation is the decrease in signal strength, measured in decibels (dB) per 100 feet. Such loss happens as the signal travels over the wire. Attenuation occurs more quickly at higher frequencies and when the cable’s resistance is higher. In networking environments, repeaters are responsible for cleaning and boosting a signal before passing it on. Many devices are repeaters without explicitly saying so. For example, each node in a token- ring network acts as a repeater. Since attenuation is sensitive to frequency, some situations require the use of equalizers to boost different-frequency signals the appropriate amount. Crosstalk Crosstalk is interference in the form of a signal from a neighboring cable or circuit; for example, signals on different pairs of twisted wires in a twisted pair cable may interfere with each other. A commonly used measure of this interference in twisted-pair cable is near-end crosstalk (NEXT), which is represented in dB. The higher the dB value, the less crosstalk and the better is the cable. Additional shielding between the carrier wire and the outside world is the most common way to decrease the effects of crosstalk. Impedance Impedance, which is a measure of electrical resistance, is not directly a factor in a cable’s performance. However, impedance can become a factor if it has different levels at different locations in a network. In order to minimize the disruptive effects of different impedances in a network, special devices, called baluns, are used to equalize impedance at the connection. Impedance does reflect performance indirectly. The higher the impedance, the higher is the resistance; the higher the resistance, the greater is the attenuation at higher frequencies. Line Conditioning Line conditioning tries to eliminate the effects of certain types of distortions on the signal. It becomes 3-6 more necessary as transmission speeds increase. Two types of line conditioning are available: C conditioning tries to minimize the effects of distortion related to signal amplitude and distortion due to envelope delay. D conditioning tries to minimize the effects of harmonic distortion in addition to the amplitude and envelope delay distortions handled by type C conditioning. A line driver is a component that includes a transmitter and a receiver; it is used to extend the transmission range between devices that are connected directly to each other. In some cases a line driver can be used in place of a modem, for short distances of 10 miles or less. To test a particular section of cable, you can use a line-testing tool. A line monitor is a low-end line- testing tool that tells you if the line is intact. A high-end line-testing tool can do very precise measurements using time domain reflectometry (TDR). A TDR is a device used to test the integrity of a section of cable before the cable is even unwound. This diagnostic method uses a signal of a known amplitude and duration, which is sent along a stretch of cable. Depending on the amount of time the signal takes to return and on the cable’s nominal velocity of propagation, the TDR can determine the distance the signal traveled and whether there are any shorts or opens in the cable. BACKBONE CONNECTIONS In addition to the inherent problems of the cabling, backbone connections add the problems that come with the use of connectors. They have only a limited number of times that they can be connected before they have to be replaced. These connectors are used in several places along the backbone, each presenting one more place for trouble to start. Some of the places that connectors are used are: At the server At the repeater, concentrator, and the gateway Along the backbone for each drop or tap At the splice and coupler (used with fiberoptic) Each of the connections uses a different type of connector, each with its own limitations. For example:

A vampire tap is a connector that uses two prongs to pierce the cable to make its connection. When it is used, one of the prongs can be bent and not make a proper connection. An RJ connector is the same type of connector used to plug your telephone into the wall. When it is used, the plastic clip has a tendency to break off the connector, resulting in the plug not locking in place. 3-7 SUMMARY In this chapter we discussed the how to troubleshoot communications line problems, network malfunctions, and how to test and evaluate the connection of networking system nodes. As with any troubleshooting, individual manufacturers of both hardware and software will have their own techniques to follow. What we have tried to do is give you a brief overview of the type of trouble that you can expect to run into and some basics as how to begin the troubleshooting.

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APPENDIX I GLOSSARY A ATTENUATION— Loss of communication signal energy. B BASEBAND— The frequency band occupied by individual information bearing signals before they are combined with a carrier in the modulation process. BISYNC— Controlling of data transmission by timing signals generated at the sending and receiving stations. BROADBAND— Transmission facilities whose bandwidth is greater than that available on voice- grade facilities. BUS— Channel or path for transferring data and electrical signals. C CARRIER SENSE MULTIPLE ACCESS (CSMA)— A protocol that controls access to a network’s bus. CARRIER SENSE MULTIPLE ACCESS WITH COLLISION AVOIDANCE (CSMA/CA)— A protocol that requires carrier sense and in which a data station that intends to transmit sends a jam signal. CARRIER SENSE MULTIPLE ACCESS WITH COLLISION DETECTION (CSMA/CD)— A protocol that requires carrier sense and in which a transmitting data station that detects another signal while transmitting, stops sending, sends a jam signal, and then waits for a variable time before trying again. CLEAR TO SEND— A hardware signal sent from a receiver to a transmitter to indicate that the transmitter can begin sending. CROSSTALK— The disturbance caused in a circuit by an unwanted transfer of energy from another circuit. F FILTER— A device or program that separates data, signals, or material in accordance with specified criteria. FIREWALL— One or more components that control the flow of network traffic between networks. H HANDSHAKING— The process through which the rules for exchanging data over a communications line are defined for the two devices involved. I IMPEDANCE— A measure of electrical resistance. INTERNATIONAL STANDARDS ORGANIZA- TION (ISO)— The international agency responsible for developing standards for information exchange. INTERRUPT REQUEST LINES— Physical connections between hardware devices and the interrupt request. L LINE DRIVER— A component that includes a transmitter and a receiver. LINK— The communications media used to connect nodes. M MULTITASKING— A mode of operation that provides for concurrent performance of two or more tasks. N NETWORK INTERFACE CARD (NIC)— The expansion card that allows the workstation to communicate with the network. AI-1

NETWORK OPERATING SYSTEM (NOS)— A software package that makes it possible to implement and control a network and that enables users to make use of resources and services on that network. NODE— The point at the end of a branch. NOISE— Random electrical signals that become part of a transmission, and that serve to make the signal (information) component of the transmission more difficult to identify. O OPEN SYSTEMS INTERCONNECTION (OSI)— The networking standard for interconnecting dissimilar computer systems. P PROTOCOL— A formal set of conventions governing the format and control of inputs and outputs between two communicating processes. R READY TO SEND— A hardware signal sent from a potential transmitter to a destination to indicate that the transmitter wishes to begin a transmission. S SYNCHRONOUS DATA LINK CONTROL (SDLC)— Primary protocol supported under System Network Architecture (SNA). SIGNAL-TO-NOISE RATIO (SNR)— The ratio between the signal and noise levels at a given point, usually at the receiving end of the transmission. T TIME DOMAIN REFLECTOMETER— A device used to test the integrity of a section of cable. TOPOLOGY— The physical or logical layout of a LAN. AI-2

APPENDIX II GLOSSARY OF ACRONYMS AND ABBREVIATIONS A AWG— American wire gauge. B Bisync— Binary synchronous communications protocol. BNC— Barrel nut connector. bps— Bits per second. C CAD— Computer aided design. CODEC— Coder/decoder. CSMA— Carrier sense multiple access. CSMA/CA— Carrier sense multiple access with collision avoidance. CSMA/CD— Carrier sense multiple access with collision detection. CTS— Clear to send. D dB— Decibel. E EIA/TIA— Electronics Industries Association/ Telecommunications Industry Association. F FSCK— Filesystem check. FTP— File transfer protocol. G Gbps— Gigabits per second. H HTTP— Hypertext transfer protocol. I IP— Intemet protocol. IRQ— Intermpt request line. ISO— International Standards Organization. L LAN— Local area network LED— Light-emitting diode. M MAN— Metropolitan area network. MAU— Multistation access unit. Mbps— Megabits per second. MIC— Medium interface connector. MODEM— Modulator-demodulator. N NEXT— Near-end crosstalk. NIC— Network interface card. NOS— Network operating system. O OSI— Open systems interconnection. P POST— Power-on self test. R RJ— Registered jack. ROM— Read-only memory. RTS— Ready to send. S SC— Subscriber connector. SDLC— Synchronous data link control. SMA— Sub-miniature assembly. AII-1

SNR— Signal-to-noise ratio. TELNET— Telecommunications network. ST— Straight tip. U STP— Shielded twisted pair. UDP— User datagram protocol. T UTP— Unshielded twisted pair. TCP— Transmission control protocol. W TDR— Time domain reflectometer. WAN— Wide area network. AII-2

APPENDIX III REFERENCES USED TO DEVELOP THIS NRTC NOTE: Although the following references were current when this NRTC was published, their continued currency cannot be assured. When consulting these references, keep in mind that they may have been revised to reflect new technology or revised methods, practices, or procedures; therefore, you need to be sure that you are studying the latest references. Feibel, Werner, Novell’s® Complete Encyclopedia of Networking, Sybex Inc., Alameda, CA, 1995. Gibbs, Mark, Absolute Beginner’s Guide to Networking, Second Edition, Sams Publishing, Indianapolis, IN 1995. Liebing, Edward, NetWare User’s Guide, M & T Books, New York, NY , 1993. Lowe, Doug, Networking F or Dummies,IDG Books Worldwide, Inc., Foster City, CA, 1994. Martin, James, Local Area Networks Architectures and Implementations, Prentice Hall, Englewood Cliffs, NJ, 1989. Ported SNAP I/II System Administration Manual TAC-3 V ersion, NA VMASSO Document Number 54-94-1, Navy Management System Support Office, Chesapeake, V A, 1994. Sherman, Ken, Data Communications User’s Guide, Third Edition, Prentice Hall, Englewood Cliffs, NJ, 1990. AIII-1

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INDEX A Access methods, 1-12 contention, 1-12 network standards, 1-13 token passing, 1-13 Analyze configuration, 1-6 C Cabling, 1-15, 3-5 cable selection, 1-17 coaxial, 1-16, 2-4 . excessive noise, 3-5 fiber optic, 1-17, 2-4 impedance, 3-6 line conditioning, 3-6 twisted-wire pairs, 1-16, 2-4 Coaxial, 1-16, 2-4 baseband, 2-4 broadband, 2-4 Collision avoidance, 3-4 CTS, 3-5 RTS, 3-5 Communication line problems, 3-5 attenuation, 3-6 backbone connections, 3-6 cabling, 3-5 Connectors, 2-4 function, 2-4 genders, 2-6 mechanisms, 2-6 shapes, 2-4 Crosstalk, 1-16, 3-6 D Data collisions, 3-4 avoidance, 3-4 detection, 3-4 E Excessive noise, 3-5 crosstalk, 3-5 impulse, 3-5 white, 3-5 F Firewalls, 1-18 application layer, 1-18 choosing, 1-19 packet filters, 1-18 H Hardware testing, 2-7 basic tools, 2-7 tools for installing cable, 2-7 tools for testing cables, 2-8 I Install components, 2-1 bridges, 2-2 brouters, 2-2 concentrators, 2-3 connectors, 2-4 gateways, 2-2 hubs, 2-3 modems, 2-3 network interface card, 2-4 repeaters, 2-1 routers, 2-2 L LAN configurations, 1-9 bus, 1-10 distributed tree, 1-11 ring, 1-11 star, 1-9 Links, 1-1 M Monitor, 1-3 N Network analyzer, 3-3 Network components, 2-1 inspecting, 2-6 install, 2-1 testing, 2-6 Network configurations, 1-4 analyze configuration, 1-6 network parameters, 1-5 network port configuration, 1-5 software configurations, 1-5 system parameters, 1-4 system resource limits, 1-6 Network design, 1-9 access methods, 1-12 cabling, 1-15 calculating capacity, 1-9 firewalls, 1-18 LAN configurations, 1-9 network operating system, 1-18 operating system, 1-18 protocols, 1-12 requests, 1-9 Network malfunctions, 3-3 component failure, 3-3 data collision, 3-4 Network operations, 1-1 monitor, 1-3 network startup/shutdown, 1-2 remote terminals, 1-2 review audit logs, 1-4 server failure, 3-3 Network parameters, 1-5 modifying, 1-5 setting, 1-5 Network physical connections, 2-8 backbones, 2-8,3-6 nodes, 2-9 Network port configuration, 1-5 port address or name, 1-5 Network server, 2-9 dedicated, 2-10 nondedicated, 2-10 Network software, 1-6 application, 1-7 installation, 1-7 restoration, 1-8 system, 1-6 testing, 1-8 Network startup/shutdown, 1-2 system shutdown, 1-3 system startup, 1-2 Network testing, 2-6 hardware, 2-7, 3-5 methods, 2-6 software, 2-8 Nodes, 1-1 O OSI model, 1-13 layer 1, 1-14 layer 2, 1-14 layer 3, 1-14 layer 4, 1-15 layer 5, 1-15 layer 6, 1-15 layer 7, 1-15 P Protocols, 1-12 Bisync, 1-12 SDLC, 1-12 R Reboot, 1-3 Remote Terminals, 1-2 logins, 1-2 remote console, 1-2 S System modes, 1-3 multi-user, 1-3 single-user, 1-3 System parameters, 1-4 hardware interrupt, 1-4 software interrupt, 1-4 System resources limits, 1-6 hardware, 1-6 software, 1-6 System restoration, 1-8 reconfiguration, 1-8 redundancy, 1-8 rerouting, 1-8 T Troubleshooting, 3-1 diagnostic tools, 3-1 isolating problems, 3-1 INDEX-1

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ASSIGNMENT 1 Textbook Assignment: “Network Administration,” chapter 1, pages 1-1 through 1-19. 1-1. Networking gives an individual the capability to communicate and connect with another individual or another system in order to accomplish which of the following tasks? 1. Send messages 2. Share resources 3. Extend processing 4. Perform multiprocessing 1-2. Which of the following types of cables is NOT used for communications? 1. Coaxial 2. Fiber optic 3. Solid core 4. Twisted-pair 1-3. Login procedures that are accomplished by dialing into an access server are known by which of the following terms? 1. Dialup access 2. Distance access 3. Extended access 4. Remote access 1-4. The first thing that the initialization program checks is which of the following areas? 1. Connections 2. Memory 3. Peripherals 4. User accounts 1-5. 1-6. 1-7. 1-8. What is the function of the kernel? 1. Establishes communications 2. Initializes the system 3. Mounts and initializes system files 4. Verifies the integrity of the root filesystem How many primary modes of system operation are there? 1. One 2. Two 3. Three 4. Four Rebooting the system is called for in how many common situations? 1. Five 2. Two 3. Six 4. Four When shutting down the system, turning off the power to the CPU is recommended under which of the following times or conditions? 1. End of the day 2. End of the week 3. Normal conditions 4. Emergency conditions 1

1-9. Which of the following is NOT a reason why you should monitor the network? 1. To enable you to tune your network 2. To establish communications 3. To maintain a performance history 4. To provide a statistical basis for equipment purchases 1-10. The main importance of reviewing audit/event logs is which of the following functions? 1. Check system throughput 2. Monitor system degradation 3. Monitor system security 4. Verify password attempts 1-11. By using the audit logs, a network administrator can track which of the following areas? 1. Which files were accessed 2. When files were accessed 3. Who accesed certain files 4. Each of the above 1-12. How many interrupt request lines (IRQs) are there in a PC environment? 1-13. 1-14. 1-15. 1-16. IRQ values for a device may be set through software or manually by which of the following ways? 1. DIP switches 2. Expansion slot 3. Type of cable used 4. Order in which device was installed Network performance is governed by which of the following areas? 1. Administration 2. Hardware 3. Software 4. Both 2 and 3 above Besides a physical interface between the device and the computer, what other type of interface does a port provide? 1. Electrical 2. Logical 3. Parallel 4. Transfer Which of the following terms is used to describe the process used by an application to test a remote device? 1. Pinging 2. Ringing 3. Signaling 4. Sounding 1. 14 2. 16 3. 18 4. 20 2

1-17. 1-18. 1-19. 1-20. The interface between the telecommunications access software and the application programs is known by which of the following terms? 1. Network operating system 2. Network system software 3. Telecommunications access software 4. Teleprocessing monitor Electronic mail is classified as what type of software program? 1. Communications 2. Utility 3. Network access 4. Network operating Which of the following terms describes the prevention of files from being updated by more than one user at a time? 1. Data integrity 2. Data validity 3. System access 4. System security access can be designated by which of the following terms? 1. Private 2. Public 3. Shared 4. Each of the above 1-21. 1-22. 1-23. 1-24. Network software often provides some type of locking capability. This locking feature prevents which of the following actions? 1. Access to the file while it is being worked on 2. Logging onto more than one workstation at a time 3. Security violations from occurring 4. Unauthorized users from logging onto the network Once the software is installed on the network, it must be tested. 1. True 2. False How many methods are used to provide service restoration after system degradation? 1. Five 2. Two 3. Three 4. Four 3 The different levels of DELETED

1-25. 1-26. 1-27. 1-28. 1-29. What is the minimum 1-30. percentage to be used in calculating the available resources for the network? 1. 10 2. 15 3. 20 4. 25 How many major types of LAN configurations are there? 1-31. 1. Five 2. Six 3. Three 4. Four Which of the following topologies was the earliest type? 1. Bus 2. Ring 3. Star 4. Distributed Which of the following topologies permits centralized diagnostics of all functions? 1. Bus 2. Ring 3. Star 4. Distributed Which of the following topologies is used in many low-cost LANs? 1. Bus 2. Ring 3. Star 1-32. 4. Distributed 4 1-33. Which of the following topologies normally requires the entire network be brought down to add a new node? 1. Bus 2. Ring 3. Star 4. Distributed Which of the following topologies can be easily adapted to the physical arrangement of the facility site? 1. 2. 3. 4. Bus Ring Star Distributed Which of the following protocols is/are used-to control line discipline? 1. Asynchronous data control 2. Binary synchronous communications 3. Synchronous data link control 4. Both 2 and 3 above The access method that will be used is governed primarily by which of the following factors? 1. Protocol 2. Topology 3. Both 1 and 2 4. Network operating system

1-34. 1-35. 1-36. 1-37. Using the token passing access method, what, if anything, happens when the transmitting station receives the same token? 1. 2. 3. 4. 1. 2. 3. 4. The message is being sent The message has been passed around the network The message has been appended by another station Nothing How many layers are there in the OSI reference model? Five Six Seven Eight The physical layer is which layer number of-the OSI reference model? 1. One 2. Two 3. Three 4. Four Which layer provides error-free transmission of information over the physical medium? 1. Data link 2. Network 3. Physical 4. Transport 1-38. 1-39. 1-40. 1-41. 1-42. The network layer is which layer number of the OSI reference model? 1. One 2. Two 3. Three 4. Four The transport layer is which layer number of the OSI reference model? 1. Five 2. Two 3. Three 4. Four Which layer ensures data units are delivered error-free, in sequence, with no losses or duplications? 1. Network 2. Presentation 3. Session 4. Transport Which layer performs the functions that enable two applications to communicate across the network? 1. Network 2. Presentation 3. Session 4. Transport Which layer formats data to be presented to the application layer? 1. Network 2. Presentation 3. Session 4. Transport 5

1-43. 1-44. 1-45. 1-46. Which layer represents the services that directly support users? 1. Application 2. Network 3. Physical 4. Session Which of the following cable types is the least expensive? 1. Coaxial 2. Fiber optic 3. Solid core 4. Twisted-pair For network purposes, 22- and 24-gauge wire are the most common types of which of the following types of cables? 1. Coaxial 2. Fiber optic 3. Solid core 4. Twisted-pair Which of the following types of cable can handle a data flow of up to approximately one Mbps? 1. Coaxial 2. Fiber optic 3. Solid core 4. Twisted-pair 1-47. Coaxial cable is used extensively in LANs whenever the distance involved is relatively short, generally less than how many miles (a) for baseband and (b) for broadband? 1. (a) 1 (b) 5 2. (a) 2 (b) 5 3. (a) 2 (b) 10 4. (a) 5 (b) 10 1-48. 1-49. Why is fiber optic cable immune to electrical interference of any kind? 1. Has only one strand per cable 2. Has thick shielding 3. Carries no electrical current 4. Uses double insulation on each wire 1-50. 6 DELETED DELETED

1-51. 1-52. Firewalls can be divided into how many different categories? 1. Five 2. Two 3. Three 4. Four What piece of hardware is 1-53. Which of the following features can be provided by a firewall? 1. Address translation 2. Authentication 3. Virtual private networks 4. All of the above typically used to implement packet filtering? 1. Bridge 2. Gateway 3. Hub 4. Router 7

ASSIGNMENT 2 Textbook Assignment: “LAN Hardware,” chapter 2, pages 2-1 through 2-10; “Network Troubleshooting,” chapter 3, pages 3-1 through 3-7. 2-1. 2-2. 2-3. 2-4. 2-5. Which of the following devices is used to amplify electrical signals carried by the network? 1. Bridge 2. Gateway 3. Repeater 4. Router Which of the following devices is used to connect identical network segments? 1. Bridge 2. Gateway 3. Repeater 4. Router Which of the following devices handles the first two layers of the OSI model? 1. Bridge 2. Gateway 3. Repeater 4. Router Which of the following devices works at the third layer of the OSI model? 1. Bridge 2. Gateway 3. Repeater 4. Router Which of the following devices works at layer seven of the OSI model? 1. Bridge 2. Gateway 3. Repeater 4. Router 2-6. Which of the following devices serves as a termination point for a cable running from individual nodes in a network? 1. Bridge 2. Concentrator 3. Gateway 4. Hub 2-7. Which of the following devices is a box with a number of connectors to which multiple nodes are attached? 1. Bridge 2. Concentrator 3. Gateway 4. Hub 2-8. Which of the following factors need to be decided on before determining the type of connector to use? 1. Architecture only 2. Cable only 3. Both architecture and cable 4. Environment 2-9. Which of the following cables is the best choice if a secure network is needed? 1. Coaxial 2. Fiber optic 3. Solid core 4. Twisted-pair 8

2-10. 2-11. 2-12. 1. 2. 3. 4. 2-13. 1. 2. 3. 4. 2-14. 2-15. Which of the following cables is identified by a designation number of RG-11? 1. Coaxial 2. Fiber optic 3. Solid core 4. Twisted-pair Which of the following signals is NOT supported by a broadband system? 1. Data 2. Digital 3. Video 4. Voice What type of connector is used to link two segments of cable in a straight run? Barrel Elbow RJ T What type of connector is used to connect telephones to the wall? Barrel Elbow RJ T An ST connector is rated for what number of matings? 1. 200 2. 500 3. 800 4. 1000 An SC connector is rated for what number of matings? 1. 200 2. 500 3. 800 4. 1000 2-16. 2-17. 2-18. 2-19. 2-20. 2-21. An SMA connector is rated for what number of matings? 1. 200 2. 500 3. 800 4. 1000 Fiber optic connectors differ from other connectors in which of the following ways? 1. Size of the ferrule 2. Keyed connector 3 The number of matings 4. All of the above Components should be tested at all but which of the following times? 1. Before they are installed 2. During the installation 3. After they are installed 4. When things go wrong To test electrical activity, you will need which of the following pieces of test equipment? 1. Armature 2. Calibrator 3. Conditioner 4. Voltmeter Which of the following pieces of test equipment should be used to check for faults in a cable? 1. Calibrator 2. Conditioner 3. Scanner 4. Voltmeter What term refers to the cable that forms the main trunk of a network? 1. Backbone 2. Main link 3. Node drop 4. Primary run 9

2-22. 2-23. 2-24. 2-25. 2-26. What type of cable is a 100-ohm, multipair cable used for voice grade communications? 1. Coaxial 2. Fiber optic 3. STP 4. UTP How many types of backbone cable are there? 1. One 2. Two 3. Three 4. Four What cable manages the bulk of the traffic on a network? 1. Backbone 2. Main link 3. Node drop 4. Primary run What device mediates between the computer and the network by doing the necessary processing and translation to enable users to send or receive commands and data over the network? 1. Network access card 2. Network interface card 3. Network operations card 4. Network union card Which of the following equipment is used to attach cable sections to each other? 1. Concentrators 2. Repeaters 3. Terminators 4. Transceivers 2-27. 2-28. 2-29. 2-30. 2-31. 10 Which of the following equipment is used to absorb a transmission at the end of a network? 1. Concentrators 2. Repeaters 3. Terminators 4. Transceivers Which of the following is NOT a category of network problems? 1. Commware 2. Hardware 3. Peopleware 4. Software Which of the following is NOT a specialized diagnostic tool? 1. Breakout box 2. Datascope 3. Time domain reflectometer 4. Voltmeter Which of the following areas cause the majority of all network-related problems? 1. Cabling failures 2. Operating system failures 3. Power outages 4. User actions To determine the problem, which of the following information should be gathered? 1. Nature of the problem 2. Node identification number 3. User’s name 4. All of the above

2-32. How many primary culprits are there to network malfunctions? 1. Five 2. Two 3. Three 4. Four 2-33. Component failures are categorized into which of the following types of faults? 1. Hard and soft 2. Hard and permanent 3. Soft and temporary 4. Permanent and temporary 2-34. PC tests are stored in ROM, 1. 2. 3. 4. are known by which of following terms? Boot test Pre-startup test Power-on self test Start test 2-35. Which of the following pieces of test equipment is the best tool to use for network malfunctions? 1. Line conditioner 2. Network analyzer 3. Time domain reflectometer 4. Voltmeter 2-36. When a network malfunction is detected, the alarm is sent to which of the following persons? 1. Department head 2. Network supervisor 3. Security officer 4. User 2-37. To reestablish services, which of the following steps is the first and easiest to try? 1. Run the system distribution 2. Run the system initialization command 3. Shutdown and reboot the system 4. Verify the domain name 2-38. Which of the following terms is used to describe what occurs when two nodes start transmitting at the same time? 1. Collision 2. Derail 3. Jam 4. Wreck 2-39. When a node needs to send data, it waits until the line is quiet and then transmits. This protocol is known by what term? 1. CSMA/CA 2. CSMA/CB 3. CSMA/CD 4. CSMA/CE 2-40. In a CSMA/CA system, the media-access method uses which of the following signals before sending a frame onto the network? 1. NTS and CTS 2. RTS and CTS 3. WTS and NTS 4. WTS and RTS 11

2-41. 2-42. 2-43. 2-44. 2-45. Which of the following terms is described as a hardware signal sent from a potential transmitter to a destination to indicate that the transmitter wishes to begin a transmission? 1. BTS 2. NTS 3. RTS 4. WTS Whether the cable is pre-made or you make it, it should always be tested before it is installed. 1. True 2. False Communication line problems fall into how many different categories? 1. Five 2. Two 3. Three 4. Four Which of the following terms is not a form of noise? 1. Blocktalk 2. Crosstalk 3. Impulse 4. White Which of the following ratios is used to determine how long a cable segment can be before the signal loss is unacceptably high? 1. NER 2. NNR 3. SER 4. SNR 2-46. 2-47. 2-48. 2-49. 2-50. Filters applied early in the transmission are known by which of the following terms? 1. Baseband 2. Broadband 3. Passband 4. Preband Which of the following terms is used to describe the decrease in signal strength measured in decibels per 100 feet? 1. Crosstalk 2. Impedance 3. Attenuation 4. Degradation A commonly used measure of interference in twisted-pair cable is referred to by which of the following names? 1. 2. 3. 4. Front-end crosstalk Inter-end crosstalk Mid-to-end crosstalk Near-end crosstalk Which of the followinq terms is a measure of electrical resistance? 1. Crosstalk 2. Impedance 3. Attenuation 4. Degradation How many types of line conditioning are available? 1. Five 2. Two 3. Three 4. Four 12

2-51. Which of the following equipment is used to extend the transmission range between devices that are connected directly to each other? 1. Line conditioner 2. Line driver 3. Network analyzer 4. Time domain reflectometer 13

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