[e2e] TCP implementations in various OS's

Detlef Bosau detlef.bosau at web.de
Wed May 12 11:55:54 PDT 2010

rick jones wrote:
> On May 12, 2010, at 2:30 AM, Detlef Bosau wrote:
> I'm arriving late to the discussion - perhaps data centers and LANs 
> were not included in your set of terrestrial TCP sessions and I'm but 
> providing fodder for "TCP as the one true protocol is bad" school of 
> thought, but it has been my experience thusfar that over a 10 Gbit/s 
> Ethernet LAN, TCP needs 128KB or more of window to achieve reasonable 
> throughput.

Is this due to the link lenghts or due to huge interface buffers?

>   Get much more than 1 ms of delay in the LAN or data center and even 
> that is insufficient.

I left out the consideration, that we have to take into account the 
number of active flows.

Using VJCC, any flow has a minimum window of 1 MSS. Actually, even 1 MSS 
may not fit on a small link. Hence, we have to provide a certain minimum 
of queueing memory to make the system work with the actual number of 
flows being active.

May this be the reason for the delays you mentioned?

Actually, I don't mind reasonable window scaling when there are sound 
reasons for it. Perhaps, the general term "misbehaved" is too strict and 
we should better encourage a reasonable usage of window scaling. 
Unfortunately, I read several discussions on this matter where window 
scaling was used or encouraged quite carelessly.
> rick jones
> Wisdom teeth are impacted, people are affected by the effects of events

Lucky me, I've only two wisdom teeth left ;-)


Detlef Bosau            Galileistraße 30        70565 Stuttgart
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