I have a VPN set up using a Cisco 851 Series router. We're using IPSEC and we're connecting to a main site using a 6 Mbps symmetrical EtherLoop circuit from NuVox Communications. The main site is the hub for several other endpoints using similar equipment and settings, and those sites aren't having any issues to speak of.
This site is an MRI clinic that does medical imaging. The imaging devices (modalities) send their images to a DICOM Gateway PC on the LAN that processes the images, packages, compresses, etc, and then sends them up to a main server at the main site for distribution to whichever radiologist reads the exams. The problem we're having is that the images are transferring very slowly across the VPN. These are very large images, usually 3 MB apiece, and usually in groups of 100 or more. They're transferring at a rate of about 1-2 images per minute, which is intolerably slow.
Network testing reveals no issues. Ping times to the internet, to the main servers, etc, are nominal. Upload and download speeds to and from the internet are in the high 5 Mbps range, which is good.
One oddity is that lately, when we install a VPN using this equipment, we have to adjust the MTU size on all client PC's inside the LAN that need to talk across the VPN. This is a known issue from what I understand with some Cisco VPNs, and when you adjust it using their Set MTU utility to 1300, everything talks. If you don't set it, you can see the network across the VPN, ping IPs, etc, but you can't join the domain, use remote desktop, or other higher level activities.
Any thoughts?
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