Live Communication Server problem within VPN

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Sep 15th, 2008
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We are using Microsoft Live Communication Server and have users who log in via Cisco VPN and have problems with maintaining IM sessions with other LCS users. Within the ASA 5520 I have disabled SIP inspection. Users intermittently lose connections within their LCS sessions via VPN. Most of the users have Cisco client 4.6.x, some have 4.8.x. All other applications work ok within the VPN session. Has anyone else experienced this issue with Microsoft LCS? Are there any other config parameters that should be set within VPN?

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singhsaju Mon, 09/15/2008 - 12:56
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This could be a fragmentation issue . IPsec adds its own header to normal application data packets and

this could lead to packet size more than 1500 bytes.

Check out following links to adjust TCP MSS value on ASA:



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mellowgb59 Thu, 10/09/2008 - 17:55
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The MSS size would affect all users. I am not having this issue with all users. I was wondering if anyone else has experienced this. If you have any other ideas please let me know.


mellowgb59 Thu, 10/09/2008 - 17:53
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No solution yet. I am still working on this issue.


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