(#3 of 7) Continuing our series on design principles , the next area of consideration is scalability. Every design guide you ever read extols the virtues of making networks scalable, but in reality what does this mean? The usual definition of the term relates to ensuring a network has sufficient capacity for the current usage patterns and for projected future growth. This works at two levels - at a micro level, this is ensuring that we provide sufficient ports of the appropriate speed, that we use network devices with sufficient aggregate throughput, that the circuits we specify have sufficient bandwidth for the use cases identified during the collection of user requirements. We monitor those elements and carry out trend analysis to ensure the environment stays within the bounds within which we built the network, and we can add more capacity simply and with minimal disruption when it is required. At a macro level, we ensure our overall network archit...