For several nights, starting at 5 or 6 PM, I have had very high (10+%) packet loss when using winMTR to ping to any host. I've check my router traffic log and the peak usage is very low (only a couple Mbps), and yet I still get quite bad packet loss. Anything I can do to fix this?
Ping your router. If that has packet loss, check your media (wifi? Hard wired?).
If possible, use a CAT5e or CAT6 ethernet cable to connect your rig to the router. That eliminates wifi radios and interference.
Ping/ICMP traffic is low priority. Devices (routers, hosts, etc) will reply to ping/ICMP *if* they aren't busy and *if* sufficient WAN bandwidth exists. Pinging anything past your router is not helpful until you know your LAN is not dropping traffic.
I'm already connected via ethernet. The WinMTR output includes a ping to my router which has 0% packet loss. It could be the case that the ICMP traffic is getting dropped first, but I did start using it to check packet loss as a result of noticing issues with other applications, and at other times of day I get near 0% loss with pings.
Okay, so the packet loss issue is not on your local network. Let's get the next router hop on your WAN:
(188.8.131.52 is a UUnet Domain Name Server)
tracert (traceroute) will list each router and three ping/icmp round trip time to reach UUdns1. The router list should include your local router (ex: 192.168.1.1), your Comcast cable modem WAN IP (ex: 24.x.y.z), and the first Comcast backbone router past your cable modem. Asterisks are ping/icmp timeout.
First hop 192.168.1.1. 12 21 28
Second hop 184.108.40.206 15 11 34
Third hop 220.127.116.11 31 43 * (one pretend packet lost)
I recommend pinging your gateway LAN IP, WAN IP and the Comcast backbone router (3rd hop).