- Implementing Cisco Networking Solutions
- Harpreet Singh
- 502字
- 2025-04-04 18:14:23
Design phase
The business requirements have been drilled down into technical requirements until the planning phase. Now is the time to convert the technical requirements into the actual protocol-level details that will ensure that the network delivers the technical, functional, and performance requirements that the network is being designed for. In this phase of the network lifecycle, some of the most technical decisions are made such as:
- What should be the physical topology of the network?
- What should be the logical topology of the network?
- How should we plan for redundancy at the node level, site level, and at a service level?
- What should be the IP addressing schema for the network?
- What protocols should run on the network?
- How do we prioritize the different types of applications on the network?
- How do we segment the users on the network?
- How do we ensure security of the network devices?
- What management protocols should be run on the network?
- How would the different services be deployed on the network?
- How would we ensure that adding a new service does not impact any existing service?
It is in the design phase of the network lifecycle that the documents called the High-level design (HLD) and Low-level design (LLD) documents are made. The high-level design talks about the network design at a protocol level, and the low-level design talks about how to implement the design on the network devices and arriving at configuration templates. These design documents detail the design to meet the requirements of availability, reliability, flexibility, security, scalability, and performance.
The detailed design can also help in chalking out the day-to-day operational activities and network management processes, thereby simplifying network operations and helping to reduce OPEX and TCO. The design phase is also the phase when the design is validated on a staged network in the lab and configuration templates are fine-tuned.
Another important activity in the design phase is to define the test cases that will be executed on the network to ensure that the network is built as designed. The test case document is generally called an Acceptance Test Plan (ATP) document or a Network Ready for Use (NRFU) test plan. Having a documented test plan down to the details on how to execute the tests and what commands to run to validate the network implementation is crucial to ensure that the network will run as per the required specifications. A typical NRFU will have two parts: one covering the test cases that can be carried out on a standalone basis at each site, and the other part covering the end-to-end service testing across the entire network. The NRFU document can also add additional parts specific to network integration/service migration if the new network has to be integrated with any existing assets, or any existing services need to be migrated on the network that is being built.
We will cover these activities like choosing the right protocols and building the configuration templates based on these protocol choices in Chapters 3 to 9.