NANOG Meeting Presentation Abstract

Hashing on broken assumptions
Meeting:	NANOG70
Date / Time:	2017-06-06 4:15pm - 4:45pm
Room:	Regency Ballroom
Presenters:	Speakers: Lorenzo Saino, Fastly Lorenzo Saino is a software engineer at Fastly, where he works on network systems and load balancing problems. Prior to that, he was a PhD student at University College London. His thesis investigated design issues in networked caching systems and he was awarded the Fabrizio Lombardi prize in 2016 for his research.
Abstract:	Widely used techniques such ECMP and LAG rely on hardware-based hashing performed on a packet five-tuple to uniformly spread traffic over different links while ensuring that packets belonging to the same flow take the same path to avoid packet reordering. These techniques operate under the assumption that the underlying hashing algorithm is correctly implemented and configured and uniformly spread traffic. But is it really the case? This talk gathers years of operational experience from the perspective of a CDN on hashing in the wild gone horribly wrong - from hardware limitations, to buggy software across both switches and middleboxes. Understanding these broken assumptions is critical when scaling load balancing functions at the network layer, as well as operating anycast networks.
Files:	Hashing on broken assumptions(PDF) Hashing on broken assumptions
Sponsors:	None.

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