I have a VPN tunnel connected from a Cisco 871 back to the office connecting to a Juniper SSG550. The tunnel is used for both data and VOIP. I have noticed that every minute there is a significant amount (possibly 100%) of packet loss for 2-3 seconds. This is most obvious when I am on my Cisco VOIP phone, as when the packet loss starts occurring, the call goes garbled for a couple of seconds.f
I have connected a network analyzer and noticed that there are several SPI packets that are being sent/received every one minute which is coinciding with the brief outage.