1. Jennifer Rexford Fall 2010 (TTh 1:30-2:50 in COS 302) COS 561: Advanced Computer Networks http://www.cs.princeton.edu/courses/archive/fall10/cos561/ Energy Efficient Networking

2. IT Energy Consumption IT consumes a lot of energy –Approximately 2.5% of worldwide energy use –As much as the airline industry, and growing –Expected to grow by 30% by 2014 Data centers –Electricity costs of $4.5B in the U.S. in 2006 –More $ on power and cooling than on hardware Networking –One third of the total IT energy use –Around 10-20% of data-center energy use –Largest energy consumer is the access equipment 2

3. Ways to Save Energy Energy proportionality –Energy use should be proportional with load –Yet, most equipment operates at least efficient regime –http://research.google.com/pubs/pub33387.html Maximizing utilization –Best energy savings is the equipment you never buy –Use the available resources as effectively as possible –… rather than buying and deploying more Selectively powering down –Shut down equipment during periods of lower demand –But, reliability concerns … and slow powering up 3

4. Main Sources of Energy Use 4 data centers networking equipment consumer devices What’s a networking researcher to do?

5. Network’s Role in Energy Efficiency Reduce energy in other sectors –E.g., video-conferencing as alternative to travel Maximize efficiency of smart grid –Real-time measurement and coordination –Protect the smart grid from cyber attacks Reduce energy on end hosts Reduce energy of the network itself 5

6. Line cards draw ~ 100W 200-400 W Networks High energy consumption –Packet-level operations –High-speed data-plane memory Not energy proportional Often over-provisioned –Avoid queuing delay on the links –Handle time-of-day traffic changes –Handle a diverse mix of workloads –Have enough capacity left after failures Bad at handling churn –Routing convergence on powering up/down equipment 6

7. Research on Network Energy Measurement of router energy consumption –Quantifying the energy of line card, switches, … –Understanding relationship to features, load, etc. Selectively powering down capacity –Turning off links, or tuning to lower capacity  E.g., variable speed Ethernet, or bundled links –Optimization problem to identify links to shut down Reducing disruptions when powering down –Reducing capacity of a link rather than shutting down –Techniques for reducing convergence delay –Router grafting and virtual router migration 7

8. Research on Reducing Host Energy In-network proxies –End hosts cannot easily go into “low power” mode –Due to “chatty” services that require periodic traffic –Could have a proxy handle these functions for the host Virtual machine migration –Migrate a virtual machine from one server to another –Support fast transfer of virtual machine state –Allow the VM to retain its address when it moves Better server load balancing –Distribute client requests to data centers and servers –Based on server capacity and electricity prices –Using DNS, HTTP redirection, front-end load balancer… 8