Juha Heinanen wrote:
i did some tcp tests using nokia N80 phone and it turned out that if
there was no other activity, it kept on sending 4 byte tcp messages
every 20 minutes, which wireshark reported as "continuation" messages.
they wre enough to keep linux iptables nat binding open. i have been
told that it is possible to configure the keepalive interval in N80
using some special means.
> I think there was a discussion on sip-implementors discussing this topic
> and the conclusion was, that this is different an every OS and often not
> configurable (or least only per system, not per application/connection).
> Thus it is to unreliable.
my understanding is tcp keepalive options are supported in linux are
they are configurable per tcp session.
Some references:
http://libkeepalive.sourceforge.net/docs/TCP-Keepalive-HOWTO discusses
keep-alive in general
I have not found an authoritative documentation about the "per TCP
connection" settings, but I looks like it is done with socket options:
from kernel's (2.6) include/linux/tcp.h
/* TCP socket options */
#define TCP_KEEPIDLE 4 /* Start keeplives after this
period */
#define TCP_KEEPINTVL 5 /* Interval between keepalives */
#define TCP_KEEPCNT 6 /* Number of keepalives before
death */
regards
klaus
--
Klaus Darilion
nic.at
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