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Midlothian, VA

[Speed] 30 Minutes of High Latency & Packet Loss Every 6 Hours

I have a problem that is driving me crazy which started around the second week of December. No changes to any hardware or software; it just came out of nowhere. Every 6 hours, my internet throughput slows to a crawl for 30 minutes and then everything clears up until it happens again 5 1/2 hours later.

I am running Ping Plotter and I can see (well at least I could until yesterday when my Comcast gateway stopped responding to pings) high latency and packet loss starting at my gateway node and the next node up, and extending all the way to the Comcast backbone node.

I have captured modem logs and upstream/downstream stats, run PingPlotter, and even used my Netgear Firewall router to capture packets from the WAN side. I have directed connected my PC to the cable mode and nothing changed, except that I get an IPv6 address.

I have had Comcast techs out to the house three times now and they say everything looks fine. The third time they sent two techs out and one said he detected some packet loss, so he was putting terminators on the unterminated connections at the pedestal. He also said they would submit a PMR, whatever that is. That was a week ago and nothing has improved.

I run Networx to monitor my network activity and do not see any bursts of network activity during or preceding the every 6 hour slowdowns. I was kind of surprised when I used Wireshark to look at my router's packet captures. There is what appears to be a constant stream of ARP packets from Comcast IP gateway node addresses that are not on my area's network. The source addresses are listed as Cadant_31:8a:41.

I could really use some help here since my internet is pretty much unusable for 30 minutes out of every 6 hour period. I have posted this problem on the xfinity.net forums and not gotten even one response.