C-Through: Part-time Optics in Data centers

Aditi Bose, Sarah Alsulaiman

Evaluation Joke

– Didn’t construct a real such data center- Simulation on electrical switching data center and on only 16

servers & 2 Ethernet switches.– They omit implementation details.– Network management overhead huge for big data centers.

Effective use of optical Network

– Estimate cross-rack traffic demand– Configure the optical circuit– Configure ToR switch to demultiplex traffic into correct path

– Method used increases configuration complexity

Application Requirements..?

– Topology aware – Doesn’t sound very practical– Increases complexity of applications.

– Communication Requirements– Traffic pattern

– Not useful for apps with small sized data units(e.g. Hadoop)– Frequency of synchronization

– Suitable for apps with loose or no synchronization.

New Protocols!

– Why Still use TCP– High app latencies.

– Wouldn’t newer protocols be more appropriate(e.g. DCTCP)?

Fault Tolerance

– What if fiber is cut?– How it affects network?

Limitations of Optical circuit switch

– Need to reconfigure faster– Catch short, bursty flows.

Cost ?

– Practical today?– Heat dissipation

Overcrowding

– Retains complete packet switch network.

Handling Latency Sensitive Applications

– Traffic de-multiplexing only based on Destination Rack & not on latency – sensitivity of applications.

– Applications studied are not sensitive to latency.