We have an ASA 5510 talking to a client's Nortel device. We are sending data over a VPN connection between the two devices 24/7. Twice a day the tunnel stops sending data, and you can no longer ping over the tunnel. The tunnel is still up during this time, and my syslog shows no timeouts in ISAKMP or IPSec during this time. I issue the clear crypto ips sa peer command and the tunnel drops and re-establishes. After doing this, pings are immediately successful. Both the client tech and I have reconfigured everything on both sides making sure that we are matching exactly. We are also both using the host address, not network on one side host on the other (which I know can cause issues). Has anyone run across this? Any ideas on what to do to fix it?