Traffic Trends: Both Drivers and Measures of Cost-Effective and Energy-Efficient Technologies and Architectures for Backbone Optical Networks

While technologies and applications can be revolutionary, the communication networks that use and support them tend to be evolutionary. Arguably, this is because the complexity, cost, and criticality of a communication infrastructure far exceed those of any individual new component or use. And too, commensurate with the predictions of future technologies and applications that could bring radical change is uncertainty. Consequently, access, regional, national and global backbone networks are usually built-out and replaced gradually for reasons of affordability, backward compatibility, and deployment flexibility. Conversely, to remain viable, the inherent inertia of large networks suggests it is imperative that potential changes in the requirements, technological choices, and architectural options are considered and understood well in advance of decisions and actions. Roadmapping of requirements and technologies is intended to frame plausible reference scenarios in the face of the unknowns. Naturally, the expected traffic is a basic requirement imposed on network design. However, the traffic flowing across a general, multi-purpose communication network, such as an optical backbone, is not an immutable quantity. It is rarely constant in time or uniform over space. Rather, traffic is one of many interdependent variables of a network and is the result of the complex interactions among them. Variables that influence network traffic include the details of users' applications and behaviors, transport costs, resource constraints, pricing strategies, network element and network architectures and capabilities, and their temporal and geographic variations ­ to name but a few.