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CSS sends TCP RST after HTTP POST

Hi everyone, I'm hoping you can solve a little mystery for us!

We have a web application that is making heavy use of AJAX.  The client browser is IE6 (due to customer requirements) and the web server is IIS6 (customer requirement) with a failover pair of CSS11501 (ver 08.20.5.01) providing L5 load balancing in bridge mode.

There is a particular page that, on initial load, makes a large number of AJAX requests – some of which return tiny amounts of data, some return tens of K.  If after this initial page load we toggle a setting on the page a number of times we get an error on the client.  Toggling the setting triggers an AJAX request – a simple POST containing the data “isVisible=true” or “isVisible=false”.

The first time we send the request is always fine. The second request will work fine if the two TCP connections opened to the server for the initial page load are still open, but will fail if a new connection has to be opened for this request.

This always seems to be triggered by the second POST request on a single connection, regardless of the values in it. We have proven this by toggling the setting successfully multiple times if we wait for existing connections to close.

From packet traces what we see is the initial POSTs on each connection are passed through to the server and HTTP 200 OK responses are received by the client.  When a second POST occurs on an open connection the CSS11501 immediately sends a TCP RST and the POST is not passed through to the server.

We cannot see anything in the packet traces either in front or behind the CSS that requests the connection to be closed (No FIN packets). Any ideas?

Thanks in advance,

Zac

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CSS sends TCP RST after HTTP POST

Hi Zac,

Please copy&paste the relevant configuration.  You mentioned some captures, were those captures taken simultaneously in the front and back side of the CSS?

If not, could you please gather these simultaneous traces and send it?

Cesar R.

--------------------- Cesar R ANS Team
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