Chapter 13: Network Design and Management

INTRODUCTION

For a computer network to be successful, it must be able to support both the current and future amounts of traffic, pay for itself within an acceptable period of time, and provide the services necessary to support users of the system. However, all these goals are difficult to achieve. First, computer networks are constantly increasing in complexity. Second is the difficulty for a business or person to define the future of computing within a company. Finally, computer network technology changes at high speed. Therefore, performing network management is also difficult. Network manager must possess computer and people skills, management skills, financial skins, and be able to keep up with changing technology

SYSTEMS DEVELOPMENT LIFE CYCLE

• Every company has number of major goals, therefore system planners and management personnels within company try to generate set of questions or problems to help company achieve those goals
• Systems development life cycle (SDLC) is a structured approach to the development of a business system, often include several phases:
• planning: identify problems, opportunities and objectives
• Analysis: determine information requirements, analyze system needs and prepare a written systems approve
• design: design and build the system
• implementation: install the system
• Maintenance: correct and update
• These phases are cyclical and usually never ending

NETWORK MODELING

• When updating or creating a new computer system, analyst will create set of models for both existing system and proposed system
• Network models can either:
• Demonstrate current state of network
• Model desired computer network
• Series of connectivity maps are network modeling tools that depict various locations involved over wide and local areas and interconnections between those locations

1. Wide Area Connectivity map

• In order to create the map, modelers should begin by identify each site or location in which the company has an office
• Each fixed site is denoted by a circle, mobile or wireless sites are indicated by circles containing letter M; and external sites are denoted by circles containing letter E
• A solid line between 2 sites a desire path for data transmission

• To identify each connection between sites, the following link characteristics can be applied to each connection
• d = distance of the connection (usually shown in either miles or kilometers)
• s = security level (high, medium, low, or none)
• du = duplexity (full duplex, half duplex, or simplex)
• dr = data rate desired (in bps)
• l = latency, or acceptable delay time across the network (usually in milliseconds, or ms)
• QoS = Quality of Service
• CBR - constant bit rate, VBR - variable bit rate, ABR - available bit rate, UBR - unreliable bit rate, or none
• de = delivery rate (sometimes called throughput percentage)

2. Metropolitan Area Connectivity Map

• Share some of the characteristics of wide area maps and local area maps
• data rate, quality of service and security are important parameters
• Failover time also have a strong impact on metropolitan area map

3. Local Area Connectivity Map

• Show the big picture design of a local area network
• Entire physical groups such as workstations are denoted in a single node
• Links between the nodes are defined by factors such as distance, security, data rate,  QoS duplexity, and throughput

• Local area detail connectivity map: can show how individual workstation or groups of workstations are clustered with switches, routers, hubs, and server farms

FEASIBILITY STUDIES

• There are a number of ways to determine if a proposed system is going to be feasible
• Technically feasible: proposed system can be created and implemented using currently existing technologies
• Financially feasible: system can be built given the company's current financial ability
• Operationally feasible: system operates as designed implemented
• Time feasible: system can be constructed in an agreed upon time frame
• Payback analysis:  a technique to use to determine a proposed system's costs and benefits
• To calculate payback analysis, you must know all expenses that will be incurred to create and maintain system, as well as all possible income derived from system
• You must also be aware of time value of money
• A dollar today is worth more than one dollar promised a year from now because dollar can be invested

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
• Computer stimulation: involves modeling an existing system or a proposed system using a computer-based stimulation tool and subjecting the model to varying degrees of user demand (called load)
• 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

CREATING A BASELINE

• Baseline: involves measuring and recording a network's state of operation over a given period of time
• Baseline can be used to determine current network performance and to help determine future network needs
• Baseline studies should be on going projects and not something started and stopped every so many years
• 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
• 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

NETWORK ADMINISTRATOR SKILLS

A good network administrator should have:

• computer skills
• people skills
• Management skills
• Financial planning skills
• knowledge of statistics
• Speaking and Writing skills

Certifications that network administrator can obtain:

• Microsoft Certified Solution Associate (MCSA)
• Cisco Certified Network Associate (CCNA)
• IBM Certified Systems Expert (CSE) and Certified Administrator (CA)

GENERATING USABLE STATISTICS

• Statistics, properly generated can be an invaluable aid to demonstrating current system demands and predicting future needs
• Mean time between failures (MTBF): average time a device or system will operate before it fails
• Mean time to repair (MTTR): average time necessary to repair a failure within the computer system
• Availability: probability that a particular component or system will be available during a fixed time period
• Availability % = (total available time - downtime)/ total available time
• Reliability: calculates the probability that a component or system will be operational for the duration of a transaction of time t.
• reliability equation: R(t) = e^-bt
  in which : b = 1/MTBF
                   t = the time interval of the operation

NETWORK DIAGNOSTIC TOOLS

1. Tools that test and debug network hardware

• Three common testing devices are:
• electrical testers (the simplest)
• cable testers
• local area network testers ( the most elaborate)

2. Network Sniffers

• Protocol analyzer or sniffer: monitors a network 24 hrs a day, seven day a week and captures and records all transmitted packets

3. Managing operation

• To assist network administrators and information technologies in doing their jobs, business have control center for their computing services
• one important elements of a control center is the help desk that answers all telephone calls and walk in questions regarding computer services

4. Simple network management protocol

• Network management protocol: facilitates the exchange of management information between network devices
• Simple Network Management protocol (SNMP): industry standard designed to manage network components from a remote location
• Agent: a managed element has management software
• SNMP manager: controls 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
• Management Information base (MIB): collection of information that is organized hierarchically and described the operating parameters of all managed agents
• Remote network monitoring (RMON) a protocol that allows a network administrator to monitor, analyze and troubleshoot a group of remotely managed elements