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Cisco Bug: CSCsz11180 - TCP Proxy mis-calculates TCP window causing connectivity problems

Last Modified

Nov 09, 2016

Products (1)

  • Cisco ASA 5500-X Series Firewalls

Known Affected Releases

8.1(2.17) 8.1(2.2)

Description (partial)

In a rare corner-case after upgrading to version 8.1(2)2 or later, certain traffic subjected to an inspection engine on the firewall might intermittently fail. This is caused by a problem introduced where the firewall mis-calculates the size of the TCP window of the TCP endpoints.

For example, when users try to watch a video using Windows Media Player and mms:// (windows media stream) the initial buffering takes long time. Then the video starts for while and then the Media Player will start buffering again and then resume playing. This buffering takes place every couple of secs.

The traffic must be subjected to advanced application inspection on the firewall. For example, the 'inspect rtsp' command will subject RTSP traffic to the inspection.
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