Secure Shell
ssh ServerAlive probes Apr 05 2011 03:48PM
Don Tucker (dtucker arlut utexas edu) (2 replies)
Re: ssh ServerAlive probes Apr 06 2011 02:41PM
Christian Grunfeld (christian grunfeld gmail com)
Why cant you put a packet on the link up to the data transfer is
finish? What is your MTU ? that is what MTU is for. Or perhaps your
MTU into time units is bigger than you want to signal !


2011/4/5 Don Tucker <dtucker (at) arlut.utexas (dot) edu [email concealed]>:
> Hello,
> I am working on an application that needs to be able to rapidly detect a
> lost connection between an ssh client and ssh server.  I am using ssh to do
> local and remote port forwarding, and sending data across the forwarded
> ports.  I was originally relying upon the TCPKeepAlive probes, but found
> that I could not consistently detect a lost detection.  Using the
> ServerAliveInterval and ServerAliveCountMax options, however, I am able to
> consistently detect a lost connection.  The problem is, if I am using a
> low-bandwidth connection (cellular modem), and I am pushing a significant
> amount of data across, it seems that this hinders the communication between
> the client and server with the ServerAlive messages.  In other words, when I
> am actually USING the connection, my application can mistakenly detect the
> connection as lost because the ServerAliveInterval x ServerAliveCountMax is
> exceeded without a response from the server.  I was surprised at this
> behavior, since I expected the ServerAlive probes to only start after data
> flow between the client and server machines across that connection had
> ceased, but perhaps I am misunderstanding.  I do not have much leeway as to
> how the server is configured.  Can someone recommend a way to be able to
> both (1) quickly detect a lost connection [which, seems to require the
> interval and countmax be small], but not mistakenly detect the connection as
> lost when it is being used?
> Thank you for any assistance.
> Don

[ reply ]
Re: ssh ServerAlive probes Apr 06 2011 01:32PM
Milind Wakale (milindwakale gmail com)


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