1 GB plan very slow

@paperrhino Thank you for your post! I would like to look over your signal from our end to see if we can spot anything out of the ordinary. Can I get you to go into Direct Messaging (little chat icon) and compose a new message to "Xfinity Support" with your full name and address? 

@paperrhino 

The upstream power is too high / out of spec. Some of the downstream channels are borked / not locking as well.  That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.

In an effort to try to obtain better connectivity / more wiggle room, check to see if there are there any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1000 MHz, bi-directional, and no gold colored garbage from Radio Shack, Home Depot, Target, etc. Splitters should be swapped with known to be good / new ones to test.

Also check the coax cable for any damage such as cuts, nicks, kinks, sharp bends, etc.

If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two-way splitter connected directly off of the drop from the street / pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.

Good luck with it !

Please report back. You may want to consider getting a tech out to investigate this.

Bear in mind that if the premises facing techs can not find or fix a problem at your home, it is they who are responsible for escalating it to their line / network / maintenance dept. techs. The problem may lie beyond your home in the local neighborhood infrastructure somewhere but it is their S.O.P. to start at the home.

@XfinityJeniece OK, I've now got a straight line between the street and the cable modem now. There is nothing inline any more. No signal booster and no splitters (unless there is one buried behind concrete somewhere.

The values reported by the modem have changed significantly, as I would expect.

But the speed test results have not changed. To a large extent since posting the reply yesterday they are significantly worse. My 24 hour average right now is a mere 56 Mbps. I changed the connection only about 10 minutes ago so this worse performance is not a result of any changes I've made to the connections. It's been ongoing 9:00 pm last night.

Here's the chart for the last 24 hours. I restarted the modem at around 4:00 pm (I didn't see your message right away) which is right around that first dip in the graph.

Things to notice. The scale is different. The first graph's Y scale is between 0 Mbps and 800 Mbps. The past day's scale has been between 0 Mbps and 200 Mbps. In the past 24 hours I've not even seen a spike above 200 Mbps. For most of today the speed has been in the 20 Mbps range.

My speeds have not been this bad since I've started monitoring it.

And again, I didn't touch anything between 4:00 pm yesterday when I restarted the modem and about 2:45 today when I was able to take all the stuff out of the path between the cable modem and the street. As far as I can tell, except for the changes in the signals shown in the modem, nothing has changed. 

Here's the result of the last three speed tests run from my OPNsense box plugged directly into the cable modem.

$ speedtest

   Speedtest by Ookla

     Server: Aerux Broadband - Denver, CO (id = 14861)
        ISP: Comcast Cable
    Latency:     9.59 ms   (2.71 ms jitter)
   Download:    59.33 Mbps (data used: 102.9 MB)                               
     Upload:    41.58 Mbps (data used: 52.0 MB)                               
Packet Loss: Not available.
 Result URL: https://www.speedtest.net/result/c/2faf912e-b849-4670-881c-1e902b9f7ac0
$ speedtest

   Speedtest by Ookla

     Server: Whitesky Communications LLC - Denver, CO (id = 23628)
        ISP: Comcast Cable
    Latency:     9.20 ms   (3.40 ms jitter)
   Download:    72.73 Mbps (data used: 107.3 MB)                               
     Upload:    41.41 Mbps (data used: 60.2 MB)                               
Packet Loss:     0.0%
 Result URL: https://www.speedtest.net/result/c/c2e9cdef-4bac-4b96-9d26-267591d22a2c
$ speedtest

   Speedtest by Ookla

     Server: Aerux Broadband - Denver, CO (id = 14861)
        ISP: Comcast Cable
    Latency:     9.70 ms   (2.17 ms jitter)
   Download:    57.27 Mbps (data used: 93.6 MB)                               
     Upload:    41.55 Mbps (data used: 21.4 MB)                               
Packet Loss: Not available.
 Result URL: https://www.speedtest.net/result/c/8707ddc4-95ec-4845-9802-880dc83540c5

Glad you got it sorted out ! Now closing your *marked solved* thread.