Re: Debugging connection stability - Xfinity Help and Support Forums

Chris134 · ‎03-24-2020

I have been having issues with an unstable connection. I notice this when doing video conferencing for work (I will drop from calls or people will say I am garbled and they can not hear me). I can also notice it in online games with disconnection and lag spikes.

I wanted to document and debug the issue, so I've been pinging various servers. The issue is apparent even if I ping the first destination that appears when I do a tracert to google, so I'm sure the issue is local. However, I just spoke with a comcast tier 2 support agent who told me that ping is unreliable as a debugging tool, and that the servers might be intermittently dropping my packets because their firewalls are trying to prevent denial of services attacks.

So two questions: Is ping really unreliable? I'm hard wired into my cable modem, no router, and I'm seeing stuff like this when I ping the first hop in a tracert or when I ping google:

Reply from 96.120.66.197: bytes=32 time=187ms TTL=255
Request timed out.
Reply from 96.120.66.197: bytes=32 time=8ms TTL=255
Reply from 96.120.66.197: bytes=32 time=78ms TTL=255
Reply from 96.120.66.197: bytes=32 time=102ms TTL=255
Reply from 96.120.66.197: bytes=32 time=23ms TTL=255
Reply from 96.120.66.197: bytes=32 time=125ms TTL=255
Reply from 96.120.66.197: bytes=32 time=64ms TTL=255
Reply from 96.120.66.197: bytes=32 time=253ms TTL=255
Reply from 96.120.66.197: bytes=32 time=78ms TTL=255
Reply from 96.120.66.197: bytes=32 time=264ms TTL=255
Reply from 96.120.66.197: bytes=32 time=27ms TTL=255
Reply from 96.120.66.197: bytes=32 time=317ms TTL=255
Request timed out.
Reply from 96.120.66.197: bytes=32 time=208ms TTL=255
Reply from 96.120.66.197: bytes=32 time=28ms TTL=255
Reply from 96.120.66.197: bytes=32 time=324ms TTL=255
Reply from 96.120.66.197: bytes=32 time=30ms TTL=255
Reply from 96.120.66.197: bytes=32 time=169ms TTL=255
Reply from 96.120.66.197: bytes=32 time=117ms TTL=255
Reply from 96.120.66.197: bytes=32 time=45ms TTL=255
Reply from 96.120.66.197: bytes=32 time=53ms TTL=255
Reply from 96.120.66.197: bytes=32 time=205ms TTL=255
Reply from 96.120.66.197: bytes=32 time=27ms TTL=255
Reply from 96.120.66.197: bytes=32 time=23ms TTL=255
Reply from 96.120.66.197: bytes=32 time=70ms TTL=255
Reply from 96.120.66.197: bytes=32 time=73ms TTL=255
Reply from 96.120.66.197: bytes=32 time=31ms TTL=255
Reply from 96.120.66.197: bytes=32 time=25ms TTL=255
Reply from 96.120.66.197: bytes=32 time=78ms TTL=255
Reply from 96.120.66.197: bytes=32 time=147ms TTL=255
Reply from 96.120.66.197: bytes=32 time=117ms TTL=255
Reply from 96.120.66.197: bytes=32 time=37ms TTL=255
Reply from 96.120.66.197: bytes=32 time=34ms TTL=255
Reply from 96.120.66.197: bytes=32 time=11ms TTL=255
Reply from 96.120.66.197: bytes=32 time=21ms TTL=255
Reply from 96.120.66.197: bytes=32 time=21ms TTL=255
Reply from 96.120.66.197: bytes=32 time=16ms TTL=255
Reply from 96.120.66.197: bytes=32 time=13ms TTL=255
Reply from 96.120.66.197: bytes=32 time=35ms TTL=255
Reply from 96.120.66.197: bytes=32 time=24ms TTL=255
Reply from 96.120.66.197: bytes=32 time=64ms TTL=255
Reply from 96.120.66.197: bytes=32 time=7ms TTL=255
Reply from 96.120.66.197: bytes=32 time=65ms TTL=255
Reply from 96.120.66.197: bytes=32 time=40ms TTL=255
Reply from 96.120.66.197: bytes=32 time=29ms TTL=255
Reply from 96.120.66.197: bytes=32 time=15ms TTL=255
Reply from 96.120.66.197: bytes=32 time=299ms TTL=255
Request timed out.
Reply from 96.120.66.197: bytes=32 time=9ms TTL=255
Reply from 96.120.66.197: bytes=32 time=9ms TTL=255
Reply from 96.120.66.197: bytes=32 time=8ms TTL=255

Second question: If this is not a sign of an unstable connection, can someone recommend other debugging tools I can use to monitor the connection and try to identify the problem I'm having with video and voice conferencing?

natedoggy28 · ‎03-24-2020

I've been having a similar issue but mine is a complete outage. I've been pinging 8.8.8.8 which I believe is Google's DNS, but I see this below. Your latency looks fairly high, though. Maybe i should try pinging cdns01.comcast.net like you are

3/24/2020 6:37:42 PM – Reply from 8.8.8.8: bytes=32 time=26ms TTL=53
3/24/2020 6:37:43 PM – Reply from 8.8.8.8: bytes=32 time=20ms TTL=53
3/24/2020 6:37:44 PM – Reply from 8.8.8.8: bytes=32 time=18ms TTL=53
3/24/2020 6:37:45 PM – Reply from 8.8.8.8: bytes=32 time=20ms TTL=53
3/24/2020 6:37:46 PM – Reply from 8.8.8.8: bytes=32 time=19ms TTL=53
3/24/2020 6:37:50 PM – Request timed out.
3/24/2020 6:37:55 PM – Request timed out.
3/24/2020 6:38:00 PM – Request timed out.
3/24/2020 6:38:05 PM – Request timed out.
3/24/2020 6:38:08 PM – Reply from 73.48.25.240: Destination host unreachable.
3/24/2020 6:38:11 PM – Request timed out.
3/24/2020 6:38:13 PM – Reply from 8.8.8.8: bytes=32 time=121ms TTL=53
3/24/2020 6:38:14 PM – Reply from 8.8.8.8: bytes=32 time=16ms TTL=53
3/24/2020 6:38:15 PM – Reply from 8.8.8.8: bytes=32 time=24ms TTL=53
3/24/2020 6:38:16 PM – Reply from 8.8.8.8: bytes=32 time=23ms TTL=53
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3/24/2020 6:38:18 PM – Reply from 8.8.8.8: bytes=32 time=24ms TTL=53
3/24/2020 6:38:19 PM – Reply from 8.8.8.8: bytes=32 time=21ms TTL=53
3/24/2020 6:38:20 PM – Reply from 8.8.8.8: bytes=32 time=15ms TTL=53
3/24/2020 6:38:21 PM – Reply from 8.8.8.8: bytes=32 time=20ms TTL=53
3/24/2020 6:38:22 PM – Reply from 8.8.8.8: bytes=32 time=21ms TTL=53
3/24/2020 6:38:23 PM – Reply from 8.8.8.8: bytes=32 time=20ms TTL=53
3/24/2020 6:38:24 PM – Reply from 8.8.8.8: bytes=32 time=20ms TTL=53
3/24/2020 6:38:25 PM – Reply from 8.8.8.8: bytes=32 time=19ms TTL=53
3/24/2020 6:38:29 PM – Request timed out.
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3/24/2020 6:39:29 PM – Request timed out.
3/24/2020 6:39:31 PM – Reply from 73.48.25.240: Destination host unreachable.
3/24/2020 6:39:34 PM – Reply from 73.48.25.240: Destination host unreachable.
3/24/2020 6:39:37 PM – Reply from 73.48.25.240: Destination host unreachable.
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3/24/2020 6:39:43 PM – Reply from 73.48.25.240: Destination host unreachable.
3/24/2020 6:39:46 PM – Reply from 73.48.25.240: Destination host unreachable.
3/24/2020 6:39:49 PM – Reply from 73.48.25.240: Destination host unreachable.
3/24/2020 6:39:52 PM – Request timed out.
3/24/2020 6:39:54 PM – Reply from 73.48.25.240: Destination host unreachable.
3/24/2020 6:39:57 PM – Reply from 73.48.25.240: Destination host unreachable.
3/24/2020 6:40:00 PM – Request timed out.
3/24/2020 6:40:02 PM – Reply from 73.48.25.240: Destination host unreachable.
3/24/2020 6:40:05 PM – Reply from 73.48.25.240: Destination host unreachable.
3/24/2020 6:40:08 PM – Reply from 73.48.25.240: Destination host unreachable.
3/24/2020 6:40:11 PM – Request timed out.

natedoggy28 · ‎03-24-2020

Ok, apparently pings to comcast dns servers are a bit higher latency than Google's.

3/24/2020 8:49:43 PM – Pinging 96.120.66.197 with 32 bytes of data:
3/24/2020 8:49:43 PM – Reply from 96.120.66.197: bytes=32 time=48ms TTL=246
3/24/2020 8:49:44 PM – Reply from 96.120.66.197: bytes=32 time=47ms TTL=246
3/24/2020 8:49:45 PM – Reply from 96.120.66.197: bytes=32 time=47ms TTL=246
3/24/2020 8:49:46 PM – Reply from 96.120.66.197: bytes=32 time=46ms TTL=246
3/24/2020 8:49:47 PM – Reply from 96.120.66.197: bytes=32 time=47ms TTL=246
3/24/2020 8:49:48 PM – Reply from 96.120.66.197: bytes=32 time=47ms TTL=246
3/24/2020 8:49:49 PM – Reply from 96.120.66.197: bytes=32 time=47ms TTL=246
3/24/2020 8:49:50 PM – Reply from 96.120.66.197: bytes=32 time=47ms TTL=246
3/24/2020 8:49:51 PM – Reply from 96.120.66.197: bytes=32 time=47ms TTL=246
3/24/2020 8:49:52 PM – Reply from 96.120.66.197: bytes=32 time=48ms TTL=246
3/24/2020 8:49:53 PM – Reply from 96.120.66.197: bytes=32 time=46ms TTL=246
3/24/2020 8:49:54 PM – Reply from 96.120.66.197: bytes=32 time=47ms TTL=246
3/24/2020 8:49:55 PM – Reply from 96.120.66.197: bytes=32 time=48ms TTL=246
3/24/2020 8:49:56 PM – Reply from 96.120.66.197: bytes=32 time=47ms TTL=246
3/24/2020 8:49:57 PM – Reply from 96.120.66.197: bytes=32 time=48ms TTL=246
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3/24/2020 8:50:00 PM – Reply from 96.120.66.197: bytes=32 time=47ms TTL=246
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3/24/2020 8:50:02 PM – Reply from 96.120.66.197: bytes=32 time=47ms TTL=246
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3/24/2020 8:50:04 PM – Reply from 96.120.66.197: bytes=32 time=48ms TTL=246
3/24/2020 8:50:05 PM – Reply from 96.120.66.197: bytes=32 time=47ms TTL=246
3/24/2020 8:50:06 PM – Reply from 96.120.66.197: bytes=32 time=47ms TTL=246
3/24/2020 8:50:07 PM – Reply from 96.120.66.197: bytes=32 time=47ms TTL=246
3/24/2020 8:50:08 PM – Reply from 96.120.66.197: bytes=32 time=46ms TTL=246
3/24/2020 8:50:09 PM – Reply from 96.120.66.197: bytes=32 time=49ms TTL=246
3/24/2020 8:50:10 PM – Reply from 96.120.66.197: bytes=32 time=47ms TTL=246
3/24/2020 8:50:11 PM – Reply from 96.120.66.197: bytes=32 time=46ms TTL=246
3/24/2020 8:50:12 PM – Reply from 96.120.66.197: bytes=32 time=47ms TTL=246
3/24/2020 8:50:13 PM – Reply from 96.120.66.197: bytes=32 time=47ms TTL=246
3/24/2020 8:50:14 PM – Reply from 96.120.66.197: bytes=32 time=47ms TTL=246
3/24/2020 8:50:15 PM – Reply from 96.120.66.197: bytes=32 time=49ms TTL=246
3/24/2020 8:50:16 PM – Reply from 96.120.66.197: bytes=32 time=46ms TTL=246
3/24/2020 8:50:17 PM – Reply from 96.120.66.197: bytes=32 time=46ms TTL=246

Chris134 · ‎03-24-2020

One other difference is that the latency in your case is very stable (when it doesn't drop a packet). My latency is all over the place. I'm at a loss for how to debug my issue if this is not a reliable indicator of connection quality, as the tech said. I've always thought that the ping to my first hop should be stable and not drop packets...

natedoggy28 · ‎03-24-2020

I really don't know why they would say it's not a reliable test. I've been able to exhibit that every time I start seeing these issues in the logs my connection goes completely down. They've replaced the cable in my yard, and the one running into my house, new modem, new splitter, everything. Have you tried logging into the gateway and looking at upstream and downstream channels, specifically the signal to noise ratio and power levels? I'm surprised they didn't ask you that.

3/24/2020 6:37:42 PM – Reply from 8.8.8.8: bytes=32 time=26ms TTL=53
3/24/2020 6:37:43 PM – Reply from 8.8.8.8: bytes=32 time=20ms TTL=53
3/24/2020 6:37:44 PM – Reply from 8.8.8.8: bytes=32 time=18ms TTL=53
3/24/2020 6:37:45 PM – Reply from 8.8.8.8: bytes=32 time=20ms TTL=53
3/24/2020 6:37:46 PM – Reply from 8.8.8.8: bytes=32 time=19ms TTL=53
3/24/2020 6:37:50 PM – Request timed out.
3/24/2020 6:37:55 PM – Request timed out.
3/24/2020 6:38:00 PM – Request timed out.
3/24/2020 6:38:05 PM – Request timed out.
3/24/2020 6:38:08 PM – Reply from 73.48.25.240: Destination host unreachable.
3/24/2020 6:38:11 PM – Request timed out.
3/24/2020 6:38:13 PM – Reply from 8.8.8.8: bytes=32 time=121ms TTL=53
3/24/2020 6:38:14 PM – Reply from 8.8.8.8: bytes=32 time=16ms TTL=53
3/24/2020 6:38:15 PM – Reply from 8.8.8.8: bytes=32 time=24ms TTL=53
3/24/2020 6:38:16 PM – Reply from 8.8.8.8: bytes=32 time=23ms TTL=53
3/24/2020 6:38:17 PM – Reply from 8.8.8.8: bytes=32 time=20ms TTL=53
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3/24/2020 6:38:25 PM – Reply from 8.8.8.8: bytes=32 time=19ms TTL=53
3/24/2020 6:38:29 PM – Request timed out.
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3/24/2020 6:39:29 PM – Request timed out.
3/24/2020 6:39:31 PM – Reply from 73.48.25.240: Destination host unreachable.
3/24/2020 6:39:34 PM – Reply from 73.48.25.240: Destination host unreachable.
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3/24/2020 6:39:46 PM – Reply from 73.48.25.240: Destination host unreachable.
3/24/2020 6:39:49 PM – Reply from 73.48.25.240: Destination host unreachable.
3/24/2020 6:39:52 PM – Request timed out.
3/24/2020 6:39:54 PM – Reply from 73.48.25.240: Destination host unreachable.
3/24/2020 6:39:57 PM – Reply from 73.48.25.240: Destination host unreachable.
3/24/2020 6:40:00 PM – Request timed out.
3/24/2020 6:40:02 PM – Reply from 73.48.25.240: Destination host unreachable.
3/24/2020 6:40:05 PM – Reply from 73.48.25.240: Destination host unreachable.
3/24/2020 6:40:08 PM – Reply from 73.48.25.240: Destination host unreachable.
3/24/2020 6:40:11 PM – Request timed out.

Chris134 · ‎03-24-2020

I have tried logging into the modem and every thing looks fine. I have also replaced the modem, tried multiple computers (all hard wired directly to the modem) and tried replacing the ethernet cable and coaxial cable in my apartment. None of these fixed the problems I am experiencing with voice chat or the packet loss I see in pings.

I don't understand why the customer service agent thought packet loss to the first hop wasn't necessarily a problem, but that's why I'm here - I just want to understand what more reliable test I can run. Can someone from Comcast tell me how I should be testing the stability of the connection?

mbind · ‎03-24-2020

Forcing a provider to accept they have a service problem is hard. The ping to the first-hop _is_ a reasonable measure. Comcast DNS is probably a good idea too, as they are still inside Comcast's network. Pinging any other server outside the Comcast network is not very useful if you want to put the "blame" on someone as there are multiple networks involved.
Saying this, ping is not an exact tool. The first IP hop you ping is an L3 device shared with many other subscribers. Routers and such can and do drop or delay pings to them if necessary; it's low-priority work compared with other activities these machines execute.
Nevertheless, my router pings the first hop every 5sec and logs the result. You may see the occasional (single) packet lost when the situation is good. Similar the variation of the ping time should be low with the occasional outlier.
You may want to use the speedtest tools available, e.g. https://www.speedtest.net/ or Comcast's own https://speedtest.xfinity.com . There seem to be some problem with extremely low upload bandwidth ongoing - and yes, I dropped out of Google meetings as well because of it 😕

mbind · ‎03-24-2020

Well, a word of caution. The troubleshooting guide
https://forums.xfinity.com/t5/Your-Home-Network/Internet-Troubleshooting-Tips/td-p/3310447
will tell you to _not_ ping the CMTS or the DNS servers.
Fair enough, maybe the Comcast email servers are a good alternative. I stay with my statement the server should be on the Comcast network, so the respsonsibility for the results falls squarely into Comcast's field.

Chris134 · ‎03-25-2020

Thanks mbind. Based on this, I changed my tests to ping comcast.com (the example used in the article you linked) as well as 1.1.1.1 and 8.8.8.8. I see the same results on all destinations, and tracert continues to confirm the problem exists between me and the first hop.

617user · ‎03-25-2020

I've noticed instability in my connection too. traceroute shows 96.120.66.197 as my first hop out of my home network too, and surprise surprise - I have lots of latentcy and drops there too. In fact googling that IP is how I found this post.

JHC3 · ‎03-25-2020

So I’ve seen multiple threads with this very issue (including my very own thread), and not one Comcast employee or expert chimes in to explain these issues. What great customer service...

natedoggy28 · ‎03-26-2020

Yes, personally I think right now their network infrastructure can't handle the load. There are too many people reporting this for it to be a coincidence. Nonetheless, I have a technician coming out for the fourth time, tomorrow. I have the same result pinging Google DNS servers vs Comcast, it lines up exactly every time when our Internet drops... the pings time out. Up until I recently posted on these forums, and read other posts, I thought this issue was isolated to just me, but apparently I'm wrong.

JHC3 · ‎03-26-2020

Please report what the tech tells you tomorrow. I’m curious as to what they will tell you. Just weird how my problem, in particular, has been an occurrence for about 4 months now and still no fix.