While understanding the different network technologies and protocols is a core requirement of a network engineer, you are also expected to understand how to plan for a network implementation and perform the actual implementation, in addition to verification of the network and troubleshooting. In some cases, your input may be valuable to the design of the network itself; therefore, it is also important for you to understand design principles.
Using ad-hoc network designs typically results in inconsistent designs and implementations, suboptimal network performance and forwarding, and a plethora of other issues. Design methodologies are documented, systematic sets of distinct steps that help to ensure that all of the necessary tasks in the network design process are completed. Using a structured design methodology provides the following advantages:
- It ensures that all steps are covered when the process is followed.
- It provides a framework for the design process deliverables.
- It validates that you know how to meet customer and business requirements.
- It allows for consistency in the design and implementation of networks.
Many design methodologies can be used. Cisco recommends using the PPDIOO life-cycle approach. Using a comprehensive life-cycle approach lowers the total cost of ownership, increases network availability, increases business agility, and provides faster access to applications and services by using a structured approach that includes the following eight steps:
- Identifying customer requirements
- Identifying and analyzing the current network
- Designing network topologies and services
- Planning the network implementation
- Proof of concept (building pilots or prototypes)
- Documenting the network design
- Implementing and verifying the network design
- Monitoring and revising the network design
Each of these steps is as important as the step before and after it. In addition, it is recommended that each of these individual steps be completed as its own project. This ensures that all steps are completed. While there are many methodologies that incorporate these general steps, the following section describes the Cisco PPDIOO life-cycle approach and how it is centered around these eight fundamental steps.
The Cisco PPDIOO Life-Cycle Approach
PPDIOO stands for Prepare, Plan, Design, Implement, Operate, and Optimize. The PPDIOO life-cycle approach is somewhat similar to the IT Information Library (ITIL) framework in that both provide a network service’s life-cycle framework to help ensure that when the project is implemented the entire company will have everything it needs to operate and maintain the new network. The Cisco PPDIOO model encompasses all steps, from network vision to optimization. Figure 1-1 below is an illustration of the different phases of the PPDIOO life-cycle approach:
Fig. 1-1. The PPDIOO Life-Cycle Approach
During the prepare phase, key decision-makers identify the initial requirements. Tasks that are completed during this phase include gathering organizational requirements, network strategy, and business case strategy. After the business requirements have been captured, a high-level conceptual architecture is proposed.
The plan phase is used to understand the business requirements and to provide an accurate assessment of a company’s current network, security state, and overall readiness to support the proposed solution. The plan phase includes gathering network requirements, a full network examination, and a gap analysis. During this phase, design engineers verify the requirements, conduct workshops, and complete site surveys. The objective of this phase is to determine whether the company has adequate resources to manage a technology deployment project to completion. This phase is then concluded by developing a detailed project plan to identify resources, potential difficulties, individual responsibilities, and critical tasks necessary to deliver the final project on time and on budget. Considerations at this stage include carefully examining single points of failure, characterizing application and protocol traffic, and analyzing bandwidth availability.
The objective of the design phase is a comprehensive, detailed (low-level) design. A solid design can improve network performance and support high availability, reliability, security, and scalability. Proof of concept, which includes building pilots or prototypes, is also included in this phase to ensure that the design meets business and technical requirements. The design phase can also guide and accelerate successful implementation with a plan to stage, configure, test, and validate network operations. Additionally, during this phase, day-to-day operations and network management processes need to be anticipated, and, when necessary, custom applications can be created to integrate new systems into existing internetwork infrastructure.
The implement phase is the phase that you, as a CCNP-level network engineer will tie into the PPDIOO life-cycle approach. This phase includes the creation of a detailed implementation plan, which is then followed by the actual implementation itself. The implementation is based on design specifications, with the objective being to integrate devices without disrupting the existing network or creating points of vulnerability. Implementation and verification plans are described in detail in the following section.
The operate phase includes the day-to-day operation of the network. The objective of this phase is to improve service quality; reduce disruptions; mitigate outages; and maintain high availability, reliability, and security. Tools and technologies such as SNMP, IP Service Level Agreement (SLA), and Syslog should be used to avoid downtime and business interruption. These tools are described in detail later in this guide. In addition to the objectives listed above, a good operations team allows the business to accommodate upgrades, moves, additions, and changes easily while effectively reducing operating costs.
The optimize phase includes working with operations in order to establish and identify system improvements. This is based on proactive network monitoring, and, in some cases, reactive fault detection and correction. This phase seeks to improve network performance, expand services, and incorporate period reassessments of the network, which may result in a redesign if the current network is experiencing too many faults or does not meet performance expectations. The ultimate objective is continually evolving the network and improving results.
Implementation Planning and Verification
As was previously stated, as a CCNP-level network engineer, you will be heavily involved in the implement phase of the PPDIOO life-cycle approach. Your responsibilities will include not only creating implementation and verification plans but also performing the actual implementation and verifying the implementation. As a network engineer, you will be expected to perform the following activities:
- Analyze design documentation, which includes the actual network design and device configurations for routers and switches that will be included in the design.
- If possible, create a test plan for the proposed changes prior to their implementation into the production network. This may entail verifying the design in a lab.
- Create an implementation plan based on the design document. This plan should also include a back-out plan in the event that things do not go as expected.
- Write a verification plan, detailing how you will verify that the implementation was successful. This should be understood by less-technical staff as well.
- Perform reviews of your peer engineering staffs’ design documents, and test implementation and verification plans to discover possible weaknesses or omissions.
A good, solid implementation plan should include the following items:
- A checklist of tasks that need to be completed
- A list of tools and resources needed
- The schedule of work, coordinated with all needed resources
- The actual device configurations
- Documented verification processes and tests
- A fallback or back-out plan
It is important to create a checklist of the tasks that need to be completed and to check off each one following completion. This ensures that all tasks are completed and have been verified correctly. If you do not create a checklist, you may miss one or two steps, which may result in an unsuccessful implementation or unnecessary troubleshooting during the implementation.
It is always important to document the tools and resources needed during the implementation. Cisco offers many tools that simplify network implementation. Examples include Cisco Configuration Professional, Cisco Configuration Engine, and Cisco Software Activation on Integrated Services Routers. In addition to the tools, the implementation plan should include the resources needed to complete the implementation. This may include Cisco support or people from other groups within the organization.
Scheduling is used to ensure that all resources that are needed for the implementation will be available. This must be coordinated with and agreed upon by all parties.
Understanding the configuration is a core requirement. You should be able to look at the design and compare it with the configuration to discover any discrepancies, errors, or omissions that may result in an unsuccessful implementation.
It is important to document how you are going to verify that the device configurations have been implemented in the correct manner. The verification documentation should include a checklist of commands that will be used to verify various phases of the implementation and whether the output is what is expected.
Finally, it is important to have a fallback plan. While we all would like to think that the implementation will go without incident, realistically, unexpected events can and do often occur. It is therefore important to ensure that you have a plan to restore the network to its previous operational state in the event that the implementation is not successful.
Implementation Planning and Verification Methodologies
In addition to the PPDIOO life-cycle approach, the following methodologies can be used to ensure success when implementing the design. These methodologies include:
- Information Technology Infrastructure Library
- Fault, Configuration, Accounting, Performance, and Security
- Telecommunications Management Network
- ISO/IEC 20000
- Control Objectives for Information and related Technology
The Information Technology Infrastructure Library (ITIL) is a set of concepts and practices for Information Technology Services Management (ITSM), Information Technology (IT) development and IT operations. Within the ITIL framework, Service Transition provides guidelines on the transition of your project to operations.
Fault, Configuration, Accounting, Performance, and Security (FCAPS) is the International Organization for Standardization (ISO) Telecommunications Management Network (TMN) model and framework for network management. Within FCAPS, implementation planning and verification fall under the Configuration Management umbrella.
TMN is a protocol model defined by ITU-T for managing open systems in a communications network. The framework identifies four logical layers of network management and implementation planning and verification that fall under the Network Management logical layer.
The ISO/IEC 20000 is the first international standard for IT Service Management. The ISO/IEC 20000 is comprised of ten sections. The Planning & Implementing New or Changed Services section includes information on implementation planning.
Finally, the Control Objectives for Information and related Technology (COBIT) is a set of best practices (framework) for IT management created by the Information Systems Audit and Control Association (ISACA) and the IT Governance Institute (ITGI). COBIT also includes best practices for implementation planning.
In summation, it is important to ensure that the implementation and verification plan provides detailed descriptions of each step in order to reduce any issues associated with misinterpretation on the part of engineers. In some cases, this may require references to other parts of the design document.
Additionally, you should use implementation guidelines that have already been defined and follow those guidelines when implementing the design. A very important step is to include estimated times required for each step. This allows you to schedule the implementation effectively. Most organizations have some form of change management process that demands information on how long the implementation will take. Make sure that you allocate enough time to ensure that you can complete all tasks comfortably and without rushing.