A problem on TCP in High RTT Environment.

[Steven Hartland]

----- Original Message ----- 
From: "John-Mark Gurney" <jmg at funkthat.com>


> Niu Zhixiong wrote this message on Sun, Aug 10, 2014 at 10:50 +0800:
>> I am sorry that I upload a WRONG SCTP capture. But, the throughput is 
>> same.
>> SCTP is double than TCP, about 18Mbps.
>> ???
>>  sctp_2.pcapng.gz
>> <https://docs.google.com/file/d/0By8sTL79ob4tMlh4WDlTSndHX0k/edit?usp=drive_web>
>> ???
>
> Ok, the owin graph is very interesting...  We do have a full 2MB 
> window
> on the receiver side, but for some reason, we only ever have just 
> under
> 6k outstanding on the connection...
>
> So, it looks like we send for a short period of time, and then stop
> sending...  Do you have LRO enabled?  I think it might be related to:
> https://svnweb.freebsd.org/changeset/base/r256920
>
> As I'm seeing >100ms gaps where the sender doesn't send any data, and
> as soon as more than one ack comes in, the next segment goes out... 
> If
> we only receive a single ack, then we wait for a timeout before 
> sending
> the next segment..
>
> Can you try to disable LRO on the receiving host?
>
> ifconfig <iface> -lro
>
> And see if that helps... If it does...  Applying the patch, or 
> compiling
> a more recent kernel from stable/10 that is after r257367 as that is 
> was
> the date that the change was merged...

r257367 was in 10.0-RELEASE