1. Energy Aware Network Operations Authors: Priya Mahadevan, Puneet Sharma, Sujata Banerjee, Parthasarathy Ranganathan HP Labs IEEE Global Internet Symposium (April 2009) Speaker: Sookhyun Yang

2. Introduction 2 This paper analyzes three energy-saving schemes to configure a switch in a data center network with link redundancy. [Data center network topology]

3. Energy Saving in a Switch Linear power model – Power consumed by each switch depends on Number of active ports Line capacity of a port How can we control a switch for saving energy? – Disable a switch port – Dynamically adapt a port’s link capacity based on its load – Turn off a line-card that have no active ports – Power off a switch that is not being used 3 [A switch with line-cards] Line-card port

4. Three Energy Saving Schemes Centralized approach LSA (Link State Adaptation) – Adapts a port’s link capacity (disabled, 10Mbps, 100Mbps, and 1Gbps) according to link utilization. NTC (Network Traffic Consolidation) – Consolidates traffic into fewer links (and switches). – Disables unused links (and switches). SLC (Server Load Consolidation) – Migrates jobs for minimizing the number of servers being used. – Applies NTC schemes. 4 [Data center network topology]

5. Variations of the Three Schemes SL (Service Level) Awareness – Adds a constraint to ensure that a link’s utilization never exceeds a certain threshold. – Ensures that at least one redundant link exists. SL awareness policy is combined with each of the three schemes. 5

6. Simulation Set-up: Workload Simulation based on workload of observed traffic 292 web-servers for 5days in April 2008 System configuration of 292 web-severs – Quad-core processors, two 1Gbps network cards – Different RAM sizes: 193 servers have 4 GB RAM, 69 servers have 8GB RAM, and 30 servers have 16GB RAM. Observed results – Workload is memory-sensitive 130 servers use 90% or greater amount of memory, 64 servers use less than 40%. – Both network bandwidth and CPU of all servers are utilized at most 10%. 6

7. 7 [Data center network topology] 292 web servers 26 rack switches (48 ports per switch) Simulation Set-up: Network Topology 2 tier-2 switch (6 line card per switch, 24 ports per line card)

8. Simulation: How to Compute Power Consumption 8 Line-card with no active ports Line speed Power consumption Perfect knowledge of an oracle – Link utilization – Job’s traffic specification – Network topology

9. LSA (Link State Adaptation) Link characteristics from 5-day measurement – 90% of links (light traffic) can be set 10 or 100Mbps. – Less than 5% of links (heavy traffic) need to be set 1Gbps. LSA’s distribution of link speeds between rack and tier-2 switches 9

10. LSA vs. SL-aware LSA 10

11. Simulation Results 11 LSA (Link state adaptation) NTC (Network traffic consolidation) SLC (Server load consolidation)

12. Deployment Issues Track traffic workload – Adapt link capacity based on link utilization statistics – Predict incoming/outgoing traffic Transition time for adapting link-speeds is between 1-3 seconds, which can affect network performance. – Buffer or ensure the existence of back-up paths 12

13. Q&A Thank you! 13