Subject: Re: [PATCH] CUBIC v2.3 with new improved slow start

From: Rick Jones <[email-masked]>
Date: Wed, 29 Oct 2008 16:53:25 -0700

Stephen Hemminger wrote:
> On Wed, 29 Oct 2008 19:14:03 -0400
> "Injong Rhee" <[email-masked]> wrote:
> 
> 
>>>This looks like a good optimization, it obviously needs more testing
>>>because Linux always seems to find new broken hardware.  The areas
>>>that need to be tested should include:
>>> * MacOs has a broken version of delayed ack that might cause
>>>   HyStart to radically underestimate.
>>
>>We tested with FreeBSD. I presume that it covers MacOS. We will look into 
>>that.
> 
> 
> No Darwin added some stupid code that holds off acks for up to 2 seconds.

Is this Apple's reimplementation of the ACK avoidance heuristics in OSX 
they used to have in previous versions of MacOS with the Mentat TCP/IP 
stack?

FWIW, HP-UX and Solaris also have ACK avoidance heursistics - they have 
a Mentat history - although both should be pretty good and neither 
should hold-off ACKs for two seconds...

rick jones