Re: [lwip-users] Questions about LwIP KEEPALIVE...

[Kieran Mansley]

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