Network Design and Management

Transcription

1 Network Design and Management Chapter 13 Learning Objectives After reading this chapter, you should be able to: Recognize the systems development life cycle and define each of its phases Explain the importance of creating one or more location connectivity diagrams Outline the differences between technical, financial, operational, and time feasibility Create a cost-benefit analysis incorporating the time value of money Explain why performing capacity planning and traffic analysis is difficult Describe the steps involved in performing a baseline study Discuss the importance of a network manager and the skills required of that position Calculate component and system reliability and availability Recognize the basic hardware and software network diagnostic tools Describe the importance of a help desk with respect to managing network operations List the main features of the Simple Network Management Protocol (SNMP) and distinguish between a manager and an agent Describe the use of the Remote Network Monitoring (RMON) protocol and its relationship to SNMP Chapter Outline 1. Introduction 2. Systems Development Life Cycle 3. Network Modeling a. Wide area connectivity map b. Metropolitan area connectivity map c. Local area connectivity map 4. Feasibility Studies 5. Capacity Planning 6. Creating a Baseline

2 7. Network Administrator Skills 8. Generating Useable Statistics 9. Network Diagnostic Tools a. Tools that test and debug network hardware b. Network sniffers c. Managing operations d. Simple Network Management Protocol (SNMP) 10. Capacity Planning and Network Design In Action: Better Box Corporation 11. Summary Lecture Notes Introduction For a computer network to be successful, it has to be able to support the current and future amount of traffic, pay for itself within an acceptable amount of time, and provide the services necessary to support users of the system. Why are these goals so challenging? First, computer networks continue to increase in complexity. A second reason is how difficult it is for an individual or a business to properly define the future of computing within a company. Finally, computer network technology changes at a breakneck speed. Why is understanding basic computer system development concepts so important? These concepts are important because during your computer network career you will either be designing or updating a network system, or you will be assisting one or more persons who are designing or updating a network system. Systems Development Life Cycle To properly understand a problem, analyze all possible solutions, select the best solution, and implement and maintain the solution, you need to follow a well-defined plan. One of the most popular and successful plans used by businesses today is the systems development life cycle (SDLC). The systems development life cycle (SDLC) is a methodology for a structured approach for the development of a business system, including planning, analysis, design, implementation and support. A methodology is a series of steps and tasks that professionals, such as systems developers, can follow to build quality systems faster, with fewer risks, and at lower costs.

3 Network Modeling If a systems analyst or even a person such as yourself has been called upon to contribute to the design of a computer network, you will want to create one or more network models. These network models can either demonstrate the current state of the network or model the desired computer network. To model a network environment for a corporation, you create a figure called a location connectivity diagram. A location connectivity diagram (LCD) is a network modeling tool that depicts the various locations involved in a network and the interconnections between those locations. Feasibility Studies Analyzing and designing a new computer system can be time-consuming and expensive. While the project is in the analysis phase and before a system is designed and installed, a feasible solution must be found. The term feasible has several meanings when applied to computer-based projects. The proposed system must be technically feasible, financially, feasible, operationally feasible, and time feasible. Capacity Planning Capacity planning involves trying to determine the amount of network bandwidth necessary to support an application or a set of applications. Capacity planning is a fairly difficult and time-consuming operation, and it is easy to plan poorly and thus design a system that will not support the intended applications. A number of techniques exist for performing capacity planning, including linear projection, computer simulation, benchmarking, and analytical modeling. Creating a Baseline Creating a baseline for an existing computer network involves the measurement and recording of a network s state of operation over a given period of time. As you will see shortly, creating a baseline involves capturing many network measurements over all segments of a network, including numerous measurements on workstations, user applications, bridges, routers, and switches. Network Manager Skills Since many network managers are dealing with both computers and people, they need the skills necessary to work with both. A checklist of skills for the network manager would include a wide platform of technology skills, including but not limited to knowledge of local area networks, wide area networks, voice telecommunication systems, data transmission systems, video transmission, basic hardware concepts, and basic software skills. A network manager should also have people skills, including the ability to talk to users in order to service problems and explore new applications. Along with people skills, a network manager also needs training skills. Training skills include the ability to train users or other network support personnel.

4 Generating Useable Statistics To support changes to a network, a network administrator needs funding. Management, unfortunately, is not always receptive to investing more funds in technology. Often management needs to be convinced that services are suffering and response time is not what it needs to be. Statistics on computer network systems can be a very useful tool for demonstrating the need to invest in technology. If properly generated, statistics can be used to support the request for a new system or modifications to an existing system. Four statistics, or measures, that are useful in evaluating networks are mean time between failures, mean time to repair, availability, and reliability. Managing Operations To assist network managers and information technologists in doing their jobs, the computing services within a business need a control center. It contains in one easily accessible place all the network documentation, including network resource manuals, training manuals, baseline studies, all equipment documentation, user manuals, vendor names and telephone numbers, procedure manuals, and forms necessary to request services or equipment. The control center can also contain a training center to assist users and other information technologists. In addition, the control center contains all hardware and software necessary to control and monitor the network and its operations. Network monitoring usually involves a network management protocol, which facilitates the exchange of management information between network devices. This information can be used to monitor network performance, find network problems, and then solve those problems, all without physically touching the affected device. Network Diagnostic Tools To support a computer network and all of its workstations, nodes, wiring, applications, and protocols, network personnel need an arsenal of diagnostic tools. The arsenal of possible diagnostic tools continues to grow with more powerful and helpful tools becoming available every day. Diagnostic tools can be grouped into two categories: tools that test and debug the network hardware and tools that analyze the data transmitted over the network. Capacity Planning and Network Design In Action: BringBring Corporation To see how capacity planning and network design work in a realistic setting, this chapter s In Action example returns to the BringBring example from Chapter 12. BringBring is expanding its data networking capability and has asked you to help design its new corporate network. It wants to add new hardware and software and provide new data applications. Although the company has enough funds to support the new applications, it wants to seek the most cost-effective solution for the long run.

5 Quick Quiz 1. Why should you know how to design a network? You may have to assist a systems analyst in planning a new network or modification to an existing network; you may be called upon to design or upgrade a network by yourself. 2. What functions of the SDLC model relate directly to network design? Feasibility studies, cost-benefit analysis, capacity planning, traffic analysis, baselining, and network modeling 3. What is Simple Network Management Protocol (SNMP)? SNMP is a protocol that allows a network manager to manage network components from a single location. Many types of devices, such as hubs, bridges, routers, switches, and servers contain SNMP support. Discussion Topics 1. Speculate why the maintenance phase of SDLC is often so much larger than the other phases. 2. Is the importance of a certified network engineer going to be replaced with individuals that do not have a certificate but have much experience or a college degree? Teaching Tips 1. If possible, bring to class a handheld network analyzer tool and plug it in to the classroom network jack. If this is not possible, perhaps the network support personnel can demonstrate a software tool that performs network analysis. 2. Perform a baseline study on the campus network (or portion of the network). This might be a good project to divide amongst students.

6 Solutions to Review Questions 1. Describe each phase of the systems development life cycle. Planning: determining which projects to examine; Analysis: learning about the current system and recommending a business solution; Design: creating the computer-based solution; Implementation: installing the system; Maintenance 2. What is the primary goal of the planning phase of SDLC? Determining which projects to examine further 3. What is the primary goal of the analysis phase of SDLC? To study the current system and recommend a business solution to the problem 4. What is the primary goal of the design phase of SDLC? To create a physical solution (which often includes computers) for the business solution presented in the analysis phase 5. What is a connectivity map and how can it assist you in designing a network? A graph that shows all locations that need to be interconnected, the distances involved, and a possible type of interconnection medium 6. Describe the four different types of feasibility studies. Technically feasible: someone can actually create this system; Financially feasible: solution can be afforded; Operationally feasible: talent exists that can operate the system; Time feasible: solution can be created in a reasonable amount of time 7. What is meant by the time value of money? A dollar today is worth more one year from now due to investing. 8. Describe the four different ways to perform capacity planning. Linear projection, computer simulation, benchmarking, analytical modeling 9. For what reasons might someone perform a baseline study? To update a system; to simply understand where system is today

7 10. List the three most important skills a network manager should possess. Technical skills, people skills, training skills 11. What is the difference between mean time between failures and mean time to repair? Mean time between failures: how long until something breaks; Mean time to repair: how long to fix something 12. What is meant by the statistical term availability? Probability a device will be available in a given time frame 13. What is meant by the term utilization? Percentage of use of a particular device 14. What is meant by the statistical term reliability? Probability of how reliable a device will be during a given time frame 15. What basic diagnostic tools are used to support a computer network? Diagnostic tools that test and debug the network hardware and diagnostic tools that analyze the data transmitted over the network 16. What should be found in the control center for a network operation? Documentation, training manuals, help desk, demo workstations, monitoring software 17. What is the function of the Simple Network Management Protocol? To monitor and possibly control network devices from a single point 18. What is the difference between a manager and an agent in SNMP? An agent is usually controlled by a manager. (An agent can also become a manager.) 19. How can Remote Network Monitoring be used to assist SNMP? Remote Network Monitoring can allow a manager to work from a remote location.

8 Suggested Solutions to Exercises 1. State during which phase or phases of the systems development life cycle the following actions are performed: a. Create a data dictionary b. Install the system c. Train users d. Write documentation e. Perform feasibility studies f. Test the system g. Create files and databases Analysis, implementation, implementation, design and implementation, analysis, design and implementation, design 2. Using the following data, calculate the payback period. Development cost: $418,040 Operation and maintenance costs (year 0 to year 6): 0; $15,045; $16,000; $17,000; $18,000; $19,000; $20,000 Discount rate: 6% Benefits (year 0 to year 6): $0; $150,000; $170,000; $190,000; $210,000; $230,000; $250,000 Payback should occur during the fourth year. 3. Create a simple analytical model that includes two formulas for calculating the approximate total time T for n terminals using roll call polling and hub polling. Use TD = time to transmit data, TRP = time to transmit a roll call poll, and THP = time to transmit a hub poll. Roll call poll: T = n*trp + m*td where n = number of stations and m = number of stations with data to return Hub poll: T = n*thp + m*td where n = number of stations (passing the poll takes time) and m = number of stations with data to return 4. You are performing a baseline study for your company, which is located on the east coast. Your company does a lot of work with businesses on the west coast. You note peak network utilization at approximately noon, when most of your employees are on lunch break. What could be causing this peak activity? Employees from the west coast must be accessing the east coast system via remote entry or the Internet at that time.

9 5. During a baseline study, a high number of cyclic checksum errors were discovered but no runts. Explain precisely what this information has to do with network segment length. If the segments are too long, then a collision won t be heard until after the workstation has completed sent the frame. It may not, however, be a runt. It might just be a frame with a checksum error. 6. A component has been operating continuously for three months. During that time, it has failed twice, resulting in 4.5 hours of downtime. Calculate the availability of the component during this three-month period If a component has a MTBF = 10 hours and a transaction takes 20 minutes, calculate the reliability of the component. R = e (1/10)* = If a component has a MTBF = 500 hours and a transaction takes 4 seconds, calculate the reliability of the component. R = e (1/500)*(4/60) = If a network has four devices with the availabilities of 0.994, 0.778, 0.883, and 0.5, what is the availability of the entire network? Is it possible for an SNMP agent in a managed device to also serve as a manager? Explain how this situation might work. Yes. A server may be used as an agent to supply current statistics and may also be used as a manager to control attached devices. 11. What are the differences between network line continuity testers and network cable testers? Continuity testers simply test to see if a wire is broken. Network cable testers can tell if the wires in a cable connection are reversed or there are other more elaborate problems. 12. You are working for a small company that has a local area network with two hubs. The communications line between the hubs has just been cut, but you don t know that. How can you determine what has happened?

10 You might try using a cable tester and see if you can determine the length of the cable that runs between hubs. If the length appears too short, there might be a problem. You could also try a software tester and try sending messages to other workstations, waiting for replies. If all workstations on a single hub are not responding, one would conclude it is either the line to the hub or the hub itself. You might also consider using managed hubs and SNMP. Thinking Outside the Box 1. You have been asked to create a help desk for the computer support division of your company. What services will your help desk provide? How will you provide those services? What type of employees will you hire to work at the help desk? Items such as install/update/repair software/hardware; update antivirus; diagnose hardware and software; provide training and literature; can provide many services by providing an address and Web page access 2. Your company wants to create a Web server to promote its business. One of the features of the Web server is that it allows remote users to download service bulletins and repair manuals. These bulletins and repair manuals are approximately 240,000 bytes in size. You anticipate that approximately 30 users per hour will want to download these documents. What speed communications line do you need to support this demand? If you consider that 30 users per hour will access, you need to guarantee a maximum of 2 minutes per download. 240,000 bytes equals 1,920,000 bits. When transferring 1,920,000 bits over a dial-up connection of approximately 40,000 bps, this will take 48 seconds, well under the 2 minutes maximum requirement. Thus, anything faster (such as cable, DSL, or T-1) should be more than sufficient.