Cisco ASA: VPN behaviour when packet loss is high on WAN

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Hi,

In our site-to-site VPN setup between two ASA's we see the following
effect: On the internet route from Office A to Office B in another
country we notice that one of the provider routers in between has 70%
packet loss or more. In this situation the ASA then drops TCP sessions
over VPN, i.e. after a telnet login one gets kicked out after a few
seconds or minutes.

Previously we had that VPN connection made with a Sonicwall and then
only the network troughput or response time went slow.

Is there a way to control this behaviour?

Thanks in advance.

Regards,
Bernd


Re: Cisco ASA: VPN behaviour when packet loss is high on WAN
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I wonder if your packets are being dropped as being too large?
Are you using path MTU detection? Have you tried using the
tcp mss adjust feature?

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It could be that the previous connection used a different encapsulation
that was just shorter enough to not be a problem on the link.

For example, if you have isakmp nat-traversal turned on now,
that probably wasn't present on your prior sonic wall, and so you
might now have a UDP layer encapsulating an ESP layer encapsulating
the payload TCP or UDP layer -- overhead build-up!

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