Intermittently our speeds drops significantly on our Comcast modem and I have isolated it to our Exchange server. Typically we have speeds of 125 Mbps for DS and 25 Mbps for US. Latency is usually around 15-20 ms. But then we will drop to 80 for DS and our US might drip below 1 Mbps with latency going up to 50-125 ms. If I disconnect the Exchange server from the network it goes right back to the typical speeds. I have our Exchange server connected to a switch for both the Static IP card and the internal network card. I have the modem plugged into the switch also. If I unplug the modem from the switch it will resume regular speeds but we don't have active sync working on our phones. We have about 40 users VPN in for mail and a legacy application that we use for property management. If I restart our Exchange server speeds tend to resume to normal levels.