Abstract
The excessive energy consumption of backbone networks is causing concerns among network operators. This thesis focuses on the design of Energy-aware Traffic Engineering (ETE) schemes which improve the energy-efficiency of different backbone networks by enabling the delivery of traffic by the smallest number of network devices so that the remaining devices can go to sleep during the periods of low traffic demands. The first proposed ETE scheme is called Time-driven Link Sleeping (TLS) which uses only two network routing topologies: the full topology with all links being active, and a reduced one with a subset of links sleeping. The key novelty of TLS lies in its ability to jointly optimize the reduced network topology and the off-peak period during which it is operated. Moreover, an extension to TLS makes it robust to single link failures. The second ETE scheme is a Green Load-balancing Algorithm (GLA) which complements TLS and other existing ETE schemes by jointly optimizing the IGP link weights in backbone networks for improved load-balancing and energy-efficiency after these existing ETE schemes put links to sleep. The final contribution is an online distributed ETE scheme called Green Backup Paths (GBP) which dynamically diverts traffic from some selected links onto their backup paths, which were pre-installed to protect against link failure, so that these links have the opportunity to go to sleep without affecting the primary purpose of the backup paths. The distributed nature of GBP makes it scalable to large networks and be very responsive to sudden traffic changes since multiple routers can concurrently make interference-free decisions. The simple TLS scheme with GLA is ideally suited for networks which experience a regular traffic pattern because of their offline nature while the more complex GBP scheme is more suitable when there is dynamic traffic because of its online nature.