Network Design Fundamentals and Methodologies

Key Network Concepts and Design Principles

Essential Network Terminology

Usability

The ease with which network users can access the network and its services. This includes goals for simplifying user tasks.

Management (Fault, Configuration, Accounting, Performance, Security)

The five key areas of network management: Fault Management, Configuration Management, Accounting Management, Performance Management, and Security Management.

Bandwidth

The data-carrying capacity of a circuit, measured in bits per second (bits/sec).

Throughput

The quantity of error-free data transmitted per unit of time by a circuit, measured in bits/bytes per second or packets per second.

Five Nines

High availability of service, commonly taken to mean 99.999% uptime.

Silent Failure

A backup circuit, ready to use when needed. This functions as an exerciser to ensure readiness.

Utilization

A measurement of how much bandwidth is being used (as a percentage of the maximum possible).

Availability

The probability of no failure when the system is required for use.

Reliability

The probability of no system failure.

Top-Down Network Design Steps

A structured approach to network design involves several key phases:

1. Analyze Requirements:
   • Business goals and constraints
   • Technical goals and tradeoffs
   • Characterize the existing network
   • Characterize network traffic
2. Design the Logical Network:
   • Define network topology
   • Select switching and routing protocols
3. Design the Physical Network:
   • Select technologies and devices
4. Test and Optimize the Network:
   • Test and optimize the network design
   • Document the network design

Importance of Structured Network Design

Why use a structured, systematic method for network design?

Using a structured approach helps divide the project into manageable modules, making them easier to manage and modify. This top-down approach primarily focuses on user requirements. Furthermore, developing logical modules before physical models aids in designing and implementing the system effectively.

What problems can occur if such methods are not used?

Without a structured method, there is a high possibility of missing user requirements. If users update new requirements, it becomes very difficult to modify the existing system.

Comparing Top-Down Network Design with PDIOO Method

Compare and contrast the top-down network design method shown in Figure 1-1 with the PDIOO method shown in Figure 1-2.

Why Explore Organizational Structures in Network Design?

Understanding an organization's divisional and group structures helps identify the amount of data available to employees and focuses on data flow. It also assists in locating major user communities and characterizing traffic flow effectively.

ITSM and ITIL in Network Design

ITSM and ITIL: Definitions, Benefits, and Challenges

ITSM (Information Technology Service Management)

Defines the framework and processes to help an organization align the delivery of IT services with business needs. ITSM's main focus is on processes and emphasizes customer importance.

ITIL (Information Technology Infrastructure Library)

Consists of documentation that represents a widely adopted version of ITSM best practices.

Benefits of ITSM/ITIL for Network Design:

• Enhances IT service skills.
• Typically delivers good value for money by optimizing service delivery.

Potential Impediments of ITSM for Network Design:

ITSM can cause delays or impede a network design project if its principles are rigidly followed without flexibility, potentially leading to bureaucratic hurdles or a lack of agility in adapting to specific project needs.