Table of Contents Link to heading

• Life Cycle Approach
• The Need to Use a System Lifecycle
  • Designing the Network
  • Maintaining the Network
• PPDIOO Life Cycle
• Stage 1 - Prepare
• Stage 2 - Plan
• Stage 3 - Design
• Stage 4 - Implement
• Stage 5 - Operate
• Stage 6 - Optimise
• PPDIOO Phases – Summary
• Life Cycle – Summary

Life Cycle Approach Link to heading

provides several key benefits aside from keeping the design process organised.

• Lower the total cost of network ownership
• Increase network availability
• Improve business agility
• Speed access to applications and services
• Identify and validating technology requirements
• Plan for infrastructure changes and resource requirements
• Develop a sound network design aligned with technical requirements and business goals
• Accelerate successful implementation
• Improve the efficiency of your network and of the staff supporting it
• Reduce operating expenses by improving the efficiency of operational processes and tools

The Need to Use a System Lifecycle Link to heading

Network Management = Designing the Network + Maintaining the Network

Organisations increasingly rely on their network infrastructure to provide mission-critical services.

Creating a network requires combining:

1. Best practices in network design
2. How to best meet the client’s requirements

Designing the Network Link to heading

• A system life cycle provides distinct stages in the change management process and they are repeated, as the need arises.
• Cisco’s PPDIOO Network life cycle gives us a scheme to guide design processes.
• Design is important because the network needs to provide what the client needs; and these needs generally change over time (e.g. organisation growth)

Maintaining the Network Link to heading

Maintaining a network requires constant attention to how it is running and this is best served by adopting a service model.

• The service model provides a framework of stages that indicate how to manage change.
• Maintenance is important because modern networks are composed of many different devices, each needing its own particular attention.
• If maintenance checks reveal that change is necessary, we move from the Maintenance mode in the life cycle to the Design mode.
• However, the important point to note, is that we use the lifecycle for both!

PPDIOO Life Cycle Link to heading

1. Prepare – Involve establishing the organisational requirements, developing a network strategy, and proposing a high-level conceptual architecture identifying technologies that can best support the architecture. The prepare phase can establish a financial justification for network strategy by assessing the business case for the proposed architecture.
2. Plan – Involve identifying initial network requirements based on goals, facilities, user needs, and so on. The plan phase involves characterising sites and assessing any existing networks and performing a gap analysis to determine whether the existing system infrastructure, sites, and the operational environment can support the proposed system. A project plan is useful for helping manage the tasks, responsibilities, critical milestones, and resources required to implement changes to the network. The project plan should align with the scope, cost, and resource parameters established in the original business requirements.
3. Design – The initial requirements that were derived in the planning phase drive the activities of the network design specialists. The network design specification is a comprehensive detailed design that meets current business and technical requirements, and incorporates specifications to support availability, reliability, security, scalability, and performance. The design specification is the basis for the implementation activities.
4. Implement – The network is built or additional components are incorporated according to the design specifications, with the goal of integrating devices without disrupting the existing network or creating points of vulnerability.
5. Operate – Operation is the final test of the appropriateness of the design. The operational phase involves maintaining network health through day-to-day operations, including maintaining high availability and reducing expenses. The fault detection, correction, and performance monitoring that occur in daily operations provide the initial data for the optimisation phase.
6. Optimise – Involves proactive management of the network. The goal of proactive management is to identify and resolve issues before they affect the organisation. Reactive fault detection and correction (troubleshooting) is needed when proactive management cannot predict and mitigate failures. In the PPDIOO process, the optimisation phase can prompt a network redesign if too many network problems and errors arise, if performance does not meet expectations, or if new applications are identified to support organisational and technical requirements.

Stage 1 - Prepare Link to heading

Some elements to consider when creating a network or expanding a pre-existing one are:

• Define what services the organisation will require – what it intends to conduct on the network.
• Network Strategy: What is the proposed network meant to do?
• Propose a high-level idea of the architecture, with the required technologies that will support it.
• Build a business case – financial outlay with expected returns.

Stage 2 - Plan Link to heading

• Relate the current physical network to the proposal.
• Define what physical resources exist and which resources will be needed, for the new network.
• Can the old network support adding the new, or are more changes needed?
• Once this first gap analysis is run, create a project plan to define the change management steps (e.g. create a basic Gantt chart – details entered later).
• The project plan would define roles, responsibilities, areas of change, timelines, stages, etc.
• This project plan should align with the scope and cost of the business vision.

Stage 3 - Design Link to heading

• The original planning requirements serve to drive the detailed characteristics of the network.
• The design is comprehensive and translates all the required client business expectations into the technical features of the network.
• More details are added to complete the project plan (e.g. Gantt chart).

The technical characteristics of the network reflect best network design practice:

• Availability
• Reliability
• Security
• Performance
• Scalability

Stage 4 - Implement Link to heading

The Network is either built, or the original one expanded, according to plan.

If it is an expanded network:

• The expansion process should not interrupt the original network operations.
• Security should not be compromised in the upgrade.
• Such elements as deadlines, stages, time, cost, etc. need to comply with the plan.
• The implementation should reflect the original design specifications.

Planning a network implementation:

• Implementation Components:
  • Description of the step
  • Reference to design documents
  • Detailed implementation guidelines
  • Detailed roll-back guidelines in case of failure
  • Estimated time needed for implementation
• Summary Implementation Plan – overview of implementation plan
• Detailed Implementation Plan – describes exact steps necessary to complete the implementation phase, including steps to verify and check the work of the network engineers implementing the plan

Stage 5 - Operate Link to heading

How the network operates is a sound question to settle at the end of the Implementation phase:

• Maintenance of daily network operations.
• Is the network offering high availability?
• Performance monitoring: How well is it working?
• Any faults detected?
• Take baseline measurements to Benchmark network performance.

Stage 6 - Optimise Link to heading

Baseline performance measurements from the previous stage form the actions of the Optimisation stage:

• Proactive management of the network means that we need to note issues that may arise – before they arise
• Reactive management means that we need to troubleshoot issues after the fact – which usually means that some ‘damage’ has already occurred
  • e.g. lost productivity, due to people not being able to do their job; lost connections; lost data; security issues, etc. are all part of Reactive management.
• Optimisation checks can flag that network performance has decreased over the initial benchmarking.
  • e.g. more users are on the network, or there are too many network issues.
• Such situations in the PPDIOO cycle could prompt a network redesign.
• New software could also have detrimental effects on network performance, so reexamining the settings can help recover lost performance.

PPDIOO Phases – Summary Link to heading

1. Prepare – establish organisational requirements.
2. Plan – identify initial network requirements.
3. Design – comprehensive, based on planning outcomes.
4. Implement – build network according to design.
5. Operate – maintain network health.
6. Optimise – proactive management of network.

Life Cycle – Summary Link to heading

• Evolutionary changes are occurring within the campus network.
• Evolution requires careful planning and deployments based on hierarchical designs.
• As the network evolves, new capabilities are added, usually driven by application data flows.
• Implementing the increasingly complex set of business-driven capabilities and services in the campus architecture is challenging if done in a piecemeal fashion.
• Any successful architecture must be based on a foundation of solid design theory and principles. The adoption of an integrated approach based on solid systems design principles is a key to success.