TCP out-of-order packets.

Brooks Davis brooks at
Wed Jan 12 21:48:16 PST 2005

On Wed, Jan 12, 2005 at 05:07:36PM -0800, Julian Elischer wrote:
> I have a link which is provided by someone else that is 7 x E1s aggregated.
> At leat it looks that way to me when I get to see it. however I have 
> only been able to get
> 60kB.sec across this, despite having a tcp window size of 131072 bytes..
> After investigation it appears that the link is massively re-orderring 
> packets.
> groups of upto 10 packets may appear in random order. (Maybe more, bu tI 
> have seen 10)
> in fact packets are rarely IN order.
> This plays havoc with the tcp sessions.
> I was thinking of writing a hacked up version of NATD that
> instead of doing NAT, just did a pre-sort on packets from each session, 
> so that the receiver would
> see a stream of IN-order packets, with occasional delays.
> firstly, does anyone have any tools to do this already (why build when 
> you can borrow)
> and secondly, does anyone have any experience with this sort of problem?
> I have no control over or access to the link.. all I have is a promise 
> that they will deliver
> 14Mb/Sec. with approc 300mSec. RTT to me but there is no promise about 
> packet order.
> I just get a 100Mb ethernet cable.

Have you tried Andre's TCP reassembly rewrite?  He says he saw
significant improvements in the face of major reordering.

-- Brooks

Any statement of the form "X is the one, true Y" is FALSE.
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