[Cake] CAKE upstreaming - testers wanted, ACK filtering rescuers needed

Jonathan Morton chromatix99 at gmail.com
Thu Apr 26 03:26:12 EDT 2018

> Genuine question:  I have a superpacket circa 64K, this is a lump of data in a tcp flow.  I have another small VOIP packet, it’s latency sensitive.  If I split the super packet into individual 1.5K packets as they would be on the wire, I can insert my VOIP packet at suitable place in time such that jitter targets are not exceeded.  If I don’t split the super packet, surely I have to wait till the end of the superpacket’s queue (for want of a better word) and possibly exceed my latency target.  That looks to me like ‘GSO/TSO’ is potentially bad for interflow latencies.

> What don’t I understand here?

You have it exactly right.  For some reason, Eric is failing to consider the general case of flow-isolating queues at low link rates, and only considering high-rate FIFOs.

More to the point, at 64Kbps a maximal GSO packet can take 8 seconds to clear, while an MTU packet takes less than a quarter second!

 - Jonathan Morton

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