Data Center Networking

The magic of the cloud is that it is always on and always available from anywhere. Users have come to expect that services are there when they need them. A data center (or warehouse-scale computer) is the nexus from which all the services flow. It is often housed in a nondescript warehouse-sized building bearing no indication of what lies inside. Amidst the whirring fans and refrigerator-sized computer racks is a tapestry of electrical cables and fiber optics weaving everything together-the data-center network. This paper provides a "guided tour" through the principles and central ideas surrounding the network at the heart of a data center-the modern-day loom that weaves the digital fabric of the Internet. Large-scale parallel computers are grounded in HPC (highperformance computing) where kilo-processor systems were available 15 years ago. HPC systems rely on fast (lowlatency) and efficient interconnection networks capable of providing both high bandwidth and efficient messaging for fine-grained (for example, cache-line size) communication. This zealous attention to performance and low latency migrated to financial enterprise systems where a fraction of a micro-second can make a difference in the value of a transaction.