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Re: [lwip-users] Questions about LwIP KEEPALIVE...
From: |
Kieran Mansley |
Subject: |
Re: [lwip-users] Questions about LwIP KEEPALIVE... |
Date: |
Thu, 15 Feb 2007 15:34:31 +0000 |
On Thu, 2007-02-15 at 16:17 +0100, Frédéric BERNON wrote:
> So, if I dont do any mistake, if a router between my lwip devices
> crashs, the connection will detect it in... 39375*200 ms = 7875 sec =
> 131.25 min !?!?!
>
> I suppose I do a mistake somewhere, or I don't understand (because
> more than 2 hours - by default - to detect a connection failure seems
> to be very very long)...
I think you've read it right. To comply with the TCP RFCs a stack MUST
default to a TCP keepalive timeout of no less that 2 hours. See
http://www.freesoft.org/CIE/RFC/1122/114.htm
If you were to send any data you'd find out sooner of course - TCP
keepalive is really only of use for connections that are idle (or I
suppose uni-directional).
The algorithm is quite conservative on the side of not closing
connections until it's really sure they are dead.
Kieran