This question was raised this year in RNDM 2013 (The 5th International Workshop on Reliable Networks Design and Modeling) during the key note speech given by Luigi Fratta as well as during the final panel.
Telecom networks have been designed to be reliable and survivable against the possibility of failures. These failures can be small scale such as an equipment failure or can impact larger network segments as in natural disasters. Availability is an important specification in the service level agreements guaranteeing a certain level of reliability in fixed networks. For a specific network resource, it is defined as the probability of being “up” and functioning at a given time in the future. When it comes to mobile networks, availability means coverage, mobility management, roaming; while reliability is about throughput guarantees, low outages, resilience to interference… In order to increase the availability, over dimensioning in mobile networks; and capacity over-provisioning in fixed networks became a common trend. The main target for traffic engineering has been load-balancing relying on the network resources being always “on” including the backup capacity.
On the other hand, green network design and traffic engineering strategies are trying to off-load the traffic towards limited amount of active resources in order to be able to switch-off the lightly loaded resources and minimize power consumption. While we are shifting the gear towards green network solutions, what will happen to our core objectives: quality of service and availability as a significant part of it? Do we need to choose in between a green network solution and reliable network solution?
It is clear for all network operators and capacity providers that priority design parameter is quality of service and reliability. But there should be a limit in increasing the redundant capacity, the survivability and quality of services. Where should we put the threshold? This is where content aware resource allocation strategies come into the picture. Because if you can define certain level of requirements for recovery times or resource availability based on the type of content, then you can also clarify the compromise between energy-efficiency and the reliability. Green network design problem then becomes a problem of clarifying the limits of the capacity that you should provide and specifying the reliability requirements based on the content and services.