Ch14

Chapter 14 Network Design and Management Data Communications and Computer Networks: A Business User’s Approach

Data Communications and Computer Networks Chapter 14 Introduction Properly designing a computer network is a difficult task. It requires planning and analysis, feasibility studies, capacity planning, and baseline creation skills. Performing network management is difficult too. A network manager must possess computer and people skills, management skills, financial skills, and be able to keep up with changing technology.

Data Communications and Computer Networks Chapter 14 Systems Development Life Cycle (SDLC) Every business has a number of goals. System planners and management personnel within a company try to generate a set of questions, or problems, to help the company achieve those goals. 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. SDLC is a methodology, or plan, for a structured approach to the development of a business system.

Systems Development Life Cycle SDLC involves several phases. These phases are often: Planning Analysis Design Implementation Maintenance These phases are cyclical and usually never ending.

Data Communications and Computer Networks Chapter 14 Cycle of the phases

Data Communications and Computer Networks Chapter 14 Systems Development Life Cycle A systems analyst is typically responsible for managing a project and following the SDLC phases. Anyone, however, may be called upon to assist a systems analyst. Or anyone may have to assume some of the duties of a systems analyst. Individuals that are called upon to support a computer network should understand the basic phases of SDLC.

Data Communications and Computer Networks Chapter 14 Systems Development Life Cycle Planning Phase - Identify problems, opportunities, and objectives. Analysis Phase - Determine information requirements. Information requirements can be gathered by sampling and collecting hard data, interviewing, questionnaires, observing environments, and prototyping. Design Phase - Design the system that was recommended and approved at the end of the analysis phase.

Data Communications and Computer Networks Chapter 14 Systems Development Life Cycle Implementation Phase - The system is installed and preparations are made to move from the old system to the new. Maintenance Phase - The longest phase, involves the ongoing maintenance of the project. Maintenance may require personnel to return to an earlier phase to perform an update.

Data Communications and Computer Networks Chapter 14

Data Communications and Computer Networks Chapter 14 Network Modeling When updating or creating a new computer system, the analyst will create a set of models for both the existing system (if there is one) and the proposed system. Network models can either demonstrate the current state of the network or can model the desired computer network. A location connectivity diagram is a network modeling tool that depicts the various locations involved in a a network and the interconnections between those locations.

Data Communications and Computer Networks Chapter 14 Network Modeling An overview location connectivity diagram shows the big picture of geographic locations of network facilities. External users and mobile users can be identified, as well as the locations primary to a business. A detailed location connectivity diagram is a close-up model of a single location and the networks that reside at the location. Working groups and the distances between those groups can be identified with a detailed diagram.

Data Communications and Computer Networks Chapter 14 X means a special site

Feasibility Studies There are a number of ways to determine if a proposed system is going to be feasible. Technically feasible means the proposed system can be created and implemented using currently existing technology. It can be done. Financially feasible means the proposed system can be built given the company’s current financial ability. We can afford it. Operationally feasible means the system operates as designed and implemented. It’ll work after we build it and it will be used.

Feasibility Studies Time feasible means the system can be constructed in an agreed upon time frame. Payback analysis ascertains costs and benefits of proposed system usually on an annual basis. Payback analysis is a good technique to use to determine financial feasibility. To calculate payback analysis, you must know all the expenses that will be incurred to create and maintain the system, as well as all possible income derived from the system. You must also be aware of the time value of money (a dollar today is worth more than one dollar promised a year from now because the dollar can be invested).

System Costs: One time costs: Personal costs Computer usage costs for analysis Hardware and software Training, support and management Supplies, furniture, space Recurring costs: Lease payments Licenses Salaries of support personal Ongoing supplies Maintenance Planned replacement

Data Communications and Computer Networks Chapter 14 Capacity Planning Capacity planning involves trying to determine the amount of network bandwidth necessary to support an application or a set of applications. A number of techniques exist for performing capacity planning, including linear projection, computer simulation, benchmarking, and analytical modeling. Linear projection involves predicting one or more network capacities based on the current network parameters and multiplying by some constant.

Data Communications and Computer Networks Chapter 14 Capacity Planning A computer simulation involves modeling an existing system or proposed system using a computer-based simulation tool. Benchmarking involves generating system statistics under a controlled environment and then comparing those statistics against known measurements. Analytical modeling involves the creation of mathematical equations to calculate various network values.

Data Communications and Computer Networks Chapter 14 Creating a Baseline Involves the measurement and recording of a network’s state of operation over a given period of time. A baseline can be used to determine current network performance and to help determine future network needs. Baseline studies should be ongoing projects, and not something started and stopped every so many years.

Data Communications and Computer Networks Chapter 14 Creating a Baseline To perform a baseline study, you should: Collect information on number and type of system nodes, including workstations, routers, bridges, switches, hubs, and servers. Create an up-to-date roadmap of all nodes along with model numbers, serial numbers and any address information such as IP or Ethernet addresses. Collect information on operational protocols used throughout the system.

Data Communications and Computer Networks Chapter 14 Creating a Baseline To perform a baseline study, you should: List all network applications, including the number, type and utilization level. Create a fairly extensive list of statistics to help meet your goals. These statistics can include average network utilization, peak network utilization, average frame size, peak frame size, average frames per second, peak frames per second, total network collisions, network collisions per second, total runts, total jabbers, total CRC errors, and nodes with highest percentage of utilization.

Data Communications and Computer Networks Chapter 14 Network Manager Skills A good network manager will possess many skills: Computer skills People skills Management skills Financial planning skills Knowledge of statistics Speaking and writing skills

Generating Useable Statistics Statistics, properly generated, can be an invaluable aid to demonstrating current system demands and predicting future needs. Mean time between failures (MTBF) Mean time to repair (MTTR) Availability is the probability that a particular component or system will be available during a fixed time period Reliability is the probability that over a period of time the particular component or device will be available

Generating Useable Statistics Mean time between failures (MTBF) is the average time a device or system will operate before it fails. (from the manufacturer!) Large or small? Mean time to repair (MTTR) is the average time necessary to repair a failure within the computer system. Includes swap time, time to bring the system back up, replacement time, etc. Large or small?

Generating Useable Statistics Availability is the probability that a particular component or system will be available during a fixed time period. A( t ) = a/(a+b) + b/(a+b) x e -(a+b)t A = 1 means the system is nearly always operational in which: a = 1/MTTR b = 1/MTBF e = natural log function t = the time interval

Generating Useable Statistics Suppose we want to calculate the availability of a modem that has a MTBF of 3000 hours and a MTTR of 1 hour. The availability of this modem for an 8-hour period is: a = 1/1 b = 1/3000 = 0.00033 A(8 hours) =1/(1 + 0.00033) + 0.00033/(1 + 0.00033) x e -(1 + 0.00033)8 = 0.9997 + 0.00033 x 0.000335 = 0.9997 Not available 3 out of 10,000 times you want it.

Data Communications and Computer Networks Chapter 14 Generating Useable Statistics Reliability is the probability that over a period of time the particular component or device will be available (not fail): R( t ) = e – bt R( 0 ) = e – 0 = 1 in which: b = 1/MTBF t = the time interval of the operation

Data Communications and Computer Networks Chapter 14 Generating Useable Statistics What is the reliability of a modem if the MTBF is 3000 hours and a transaction takes 20 minutes, or 1/3 of an hour (0.333 hours): R(0.333 hours) = e -(1/3000)(0.333) = e -0.000111 = 0.99989 Not reliable for .011 percent of the time.

Data Communications and Computer Networks Chapter 14 Generating Useable Statistics So what do you want? Availability and reliability between 0.9999 and 0.99999 is desired! What is this in number of hours between failure for a year of service?

Data Communications and Computer Networks Chapter 14 Managing Operations There are many services and functions available to assist an individual in managing computer network operations. One of the more useful is Simple Network Management Protocol (SNMP) . SNMP is an industry standard designed to manage network components from a remote location. Currently in version 3, SNMP supports agents, managers, and the Management Information Base (MIB).

Data Communications and Computer Networks Chapter 14 Managing Operations A managed element has management software, called an agent , running in it. A second object, the SNMP manager , controls the operations of a managed element and maintains a database of information about all managed elements. A manager can query an agent to return current operating values, or can instruct an agent to perform a particular action. The Management Information Base (MIB) is a collection of information that is organized hierarchically and describes the operating parameters of all managed agents.

Data Communications and Computer Networks Chapter 14 Managing Operations SNMP operates on a network between the application layer and the UDP/IP layer (not TCP/IP) – the transport layer.

Data Communications and Computer Networks Chapter 14 Network Diagnostic Tools To assist a network support person, a number of diagnostic tools are available: Electrical testers (voltage, etc.) Cable testers (open circuits, etc.) Network testers (view the entire network0 Protocol analyzers (monitors packets)

Data Communications and Computer Networks Chapter 14 Capacity Planning and Network Design In Action: BringBring Corporation Returning to BringBring Corporation from an earlier chapter, let’s complete our design, including e-mail and Internet access for each of the four sites. A linear projection can be used to estimate the amount of Internet traffic at each site. An overview location connectivity diagram gives us a big picture of the network interconnections.

Data Communications and Computer Networks Chapter 14 Capacity Planning and Network Design In Action: BringBring Corporation A second linear projection can be used to determine the amount of local area network traffic within each site.

Ch14

More Related Content

What's hot (18)

Viewers also liked (16)

Similar to Ch14 (20)

Recently uploaded (20)

Ch14