Summary: TCP timeout between hosts

From: Vlade <>
Date: Wed Jul 17 2002 - 12:17:25 EDT
I got a good amount of responses with 2 differing opinions. Some people told
me the connection would be closed after tcp_close_wait_interval which is 4
minutes. This variable defines how long a host  would wait in the TIME_WAIT
state.  This implies that the host which is still up ties to send packets over
the TCP connection to the down host. If it doesn't get any replies it moves
into this TIME_WAIT state for 4 minutes before it closes the socket.

I wasn't clear enough in my original query. I wanted to know if 1 host goes
down hard (power failure,nic failure) for a very long time, like a day, and
both hosts are idle, how long would the socket stay open on the side that was
still alive.

By default, it would theoretically stay up forever. However, when a socket is
created, you could give it the SO_KEEPALIVE option, which would send a
keepalive according to the value  tcp_keepalive_interval which defaults to 2

So in summary if SO_KEEPALIVE is called the answer is 2 hours by default, if
not the socket would stay open indefinitely.

Thanks to

David LaPorte
Jon Andrews
Darren Dunham
Dave Mitchell
Casper Dik

origianl question:

> Lets say 2 Sun Servers have a TCP connection to lets say port 5550. Now one
> the hosts dies, lets say power failure. How long does the other host keep
> socket(connection) open. The RFC for TCP does not have a timeout for this.
> question is what is the default timeout for Solaris 2.6-2.8 servers for
> type of event?
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Received on Wed Jul 17 12:35:55 2002

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