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SV: [lwip-users] TCP problem

From: Jan Wester
Subject: SV: [lwip-users] TCP problem
Date: Wed, 21 Oct 2009 09:10:15 +0200

It works by setting MSS = 2*WND (the threshold is higher), but it still
decrease the window size and that is wrong, I have also compare it with a
windows machine

Setting the threshold = 0, will not turn off the behavior

Med vänliga hälsningar/Best Regards
Jan Wester

WHI Konsult AB
Scheelegatan 11, SE-112 28 Stockholm
+46 8 449 05 30
+46 705 36 77 22

-----Ursprungligt meddelande-----
Från: address@hidden
[mailto:address@hidden För Simon Goldschmidt
Skickat: den 21 oktober 2009 07:28
Till: Mailing list for lwIP users
Ämne: RE: [lwip-users] TCP problem

> Is it worth adding a check like other checks that are in lwip_init?

Up to 1.3.0, it seems to have been working with WND == MSS. And although
this is not a good idea regarding performance, there are applications where
it makes sense, e.g. if your system is too slow to receive two segments in a
row without a big gap in between. So adding a check including #error might
be annoying in this case.

However, I a) don't know if other TCP stacks handle this well (problems with
remote peers may arise) and b) I guess WND < MSS might not work at all, so
at least checking this in lwip_init might be a good idea.

After all, I'm still not sure that the change in behaviour seen from 1.3.0
to 1.3.1 (can be seen quite good in Jan's wireshark dump) is OK (unless it
can be turned off by setting the window update threshold to zero).


> Bill
> >Alain Mouette wrote:
> >> May I suggest that a comment about this be added in the config file.
> >>
> >> A special page on the wiki about configuring the many buffers in LWIP
> >> would be awsome too... This is a very obscure area in lwip config :(
> >>
> >
> >Please have a look at opt.h (and it's in there for a while now):
> >
> >/**
> > * TCP_WND: The size of a TCP window.  This must be at least
> > * (2 * TCP_MSS) for things to work well
> > */
> >#ifndef TCP_WND
> >#define TCP_WND                         2048
> >#endif
> _______________________________________________
> lwip-users mailing list
> address@hidden
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