Ahh, also, check your network adapter's MTU settings. You may have too much packet fragmentation (especially if you use PPPoE DSL).How to optimize VPN performance with your network.
Determining the maximum packet size that can traverse the tunnel:
Connect with the MUVPN client and do a ping test to a server on the other side of the MUVPN or BOVPN tunnel.
Example. Your Exchange or Terminal server is 192.168.10.5
C:\ping –l 1500 –f 192.168.10.5
Pinging 192.168.10.5 with 1500 bytes of data:
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Ping statistics for 192.168.10.5:
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms
This means the packet is fragmenting and is rejected since the –f (do not fragment is set) as most PC’s are set to 1500 MTU by default.
Reduce the size in the ping command until you get good reply pings.
C:\ping –l 1350 –f 192.168.10.5
Pinging 192.168.10.5 with 1350 bytes of data:
Reply from 192.168.10.5: bytes=1350 time=109ms TTL=52
Reply from 192.168.10.5: bytes=1350 time=32ms TTL=52
Reply from 192.168.10.5: bytes=1350 time=235ms TTL=52
Reply from 192.168.10.5: bytes=1350 time=141ms TTL=52
Ping statistics for 192.168.10.5:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 32ms, Maximum = 235ms, Average = 129ms
Once you have determined the maximum packet size, subtract 10 from this value, to allow for some additional overhead. Use this value for the MaxMTU string.
Caution: The following steps demonstrate how to manually adjust the MTU setting in your Windows registry. Using the Registry Editor incorrectly can lead to serious problems in Microsoft Windows and Windows applications. WatchGuard assumes no responsibility for mistakes or errors that result of incorrectly using the Registry Editor.
How to change the MTU on Windows NT, 2000, and XP (As an alternative, Dr. TCP can be downloaded from dslreports.com)
1. Click on Start => Run.
2. Type: regedit and click OK.
3. Find HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip
4. Click the Parameters folder.
5. Click Edit => New => String Value.
Type MaxMTU and hit the "Enter" key twice. In the dialog box that appears, type 1450.
6. Click the OK button.
7. Exit Regedit and restart your computer.
