Re: TCP and reordering

On 11/27/2012 01:32 AM, Saku Ytti wrote:

Today due to fast retransmit performance on links which cause
reordering is appalling.

Is it too esoteric situation to handle gracefully? Couldn't we
maintain 'reorder' counter in socket, which is increment when we get
two copies of same packet after duplicate ack, if this counter is
sufficiently high in relation to packet loss, we could start delaying
duplicate acks as we'd expect to receive the sequence very soon.

Packet reordering is supposed to be the exception, not the rule.  Links 
which habitually/constantly introduce reordering are, in my opinion, 
broken.  Optimizing for them would be optimizing an error case.

That said, there is net.ipv4.tcp_reordering which you can increase from 
the default of three to desensitize TCP to such broken links.  That will 
though be on the sending rather than receiving side.

rick jones