Discussion:
tcp keepalive timer
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sangeeta chowdhary
2013-12-12 06:17:09 UTC
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Hi,

I have one question related to TCP keepalive timer. If keepalive timer expires, then we send a probe packet, and client respond with ack. I want to know where this ACK is processed.

When we get ack for probe packet, we reset the timer. Where resetting of timer has been done?

When we get ACK for probe packet, do we increase the congestion window?
Looking forward to your response.

Regards,
Sangeeta
Rick Jones
2013-12-12 18:13:55 UTC
Permalink
Post by sangeeta chowdhary
I have one question related to TCP keepalive timer. If keepalive
timer expires, then we send a probe packet, and client respond with
ack. I want to know where this ACK is processed.
Somewhere in the TCP code - where exactly will depend on the specific
stack (Linux, BSD, HP-UX, AIX, Solaris, etc etc).
Post by sangeeta chowdhary
When we get ack for probe packet, we reset the timer. Where
resetting of timer has been done?
Same as above.
Post by sangeeta chowdhary
When we get ACK for probe packet, do we increase the congestion window?
Looking forward to your response.
The keepalive probe is not actual (current) data.

rick jones
--
oxymoron n, commuter in a gas-guzzling luxury SUV with an American flag
these opinions are mine, all mine; HP might not want them anyway... :)
feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...
sangeeta chowdhary
2013-12-16 05:33:01 UTC
Permalink
Post by Rick Jones
Post by sangeeta chowdhary
I have one question related to TCP keepalive timer. If keepalive
timer expires, then we send a probe packet, and client respond with
ack. I want to know where this ACK is processed.
Somewhere in the TCP code - where exactly will depend on the specific
stack (Linux, BSD, HP-UX, AIX, Solaris, etc etc).
Somewhere means where in Linux, I tried to find in tcp_ack(), but I didn't see anything related to Keepalive Probe packet ACK.
Post by Rick Jones
Post by sangeeta chowdhary
When we get ack for probe packet, we reset the timer. Where
resetting of timer has been done?
Same as above.
Post by sangeeta chowdhary
When we get ACK for probe packet, do we increase the congestion window?
Looking forward to your response.
The keepalive probe is not actual (current) data.
rick jones
--
oxymoron n, commuter in a gas-guzzling luxury SUV with an American flag
these opinions are mine, all mine; HP might not want them anyway... :)
feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...
Jorgen Grahn
2013-12-16 09:56:06 UTC
Permalink
Post by sangeeta chowdhary
Post by Rick Jones
Post by sangeeta chowdhary
I have one question related to TCP keepalive timer. If keepalive
timer expires, then we send a probe packet, and client respond with
ack. I want to know where this ACK is processed.
Somewhere in the TCP code - where exactly will depend on the specific
stack (Linux, BSD, HP-UX, AIX, Solaris, etc etc).
Somewhere means where in Linux, I tried to find in tcp_ack(),
but I didn't see anything related
to Keepalive Probe packet ACK.
There are some sysctls in Linux where you can tune this, e.g.
tcp_keepalive_intvl. Trace the usage of that one through the kernel,
and I suspect you will find the code which is responsible for the
feature.

/Jorgen
--
// Jorgen Grahn <grahn@ Oo o. . .
\X/ snipabacken.se> O o .
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