JUNOS High Availability

Chapter 18. Network Scalability

Opinions vary widely about the definition of network scalability. Some consider it to be the network’s ability to handle growing amounts of work and the increasing demands for resources and services. To others, true network scalability must include elements of modularity and mathematical logic. According to this second definition, for a network to be truly scalable, the addition of hardware should yield processing, throughput, and service capacities proportional to the characteristics of the hardware added.

While neither definition is wrong, we’d say they’re both missing parts of the picture. The second definition implies that network scalability is a simple byproduct of hardware capacity. Both definitions assume the network will only grow. In the modern economy, it is sometimes necessary for a network to shrink in capacity and cost, while oftentimes retaining all functionality.

A more modern definition of network scalability is the ability of the network to retain all functionality and services while adjusting its capacity and cost to properly fit demand. This definition implies that the network can get bigger and smaller. It’s with this definition in mind that we approach the discussion in this chapter.