Sharing is Caring In Datacenter NetworksA cloud computing discussion led by Justine

Techniques we learned today

• Random can work “pretty well” (VLB/ECMP) to avoid collisions in DC networks.

• For bulk computing applications like Dryad and MR, optimizing transfers rather than flows makes jobs run much faster.

• Using a centralized controller – To schedule (Orchestra)– To route and reroute (Hedera)…can improve performance.

But let’s be careful about when they’re useful…

• Bulk computing frameworks – Flows are large– Flows come in batches - transfers– Can typically modify endpoints

• Front-end/Web Services– Flows are small– Flows arise on-demand–Want flows to complete as quickly as

possible

But let’s be careful about when they’re useful…

• And what about multi-tenant environments, e.g. EC2?– Traffic patterns are varied– Fairness very important– Limited or no ability to change end-host

stack

What’s missing from the centralized schedulers in Hedera and Orchestra?

None of these papers focused on network topology – is topology even relevant?

ECMP/VLB Hedera Orchestra

Bulk Transfer Completion Time

Long Flow Completion Time

Short Flow Completion Time

Fairness

Complexity in Network

Modification to End-Hosts

Obligatory WIN/LOSE Table