I have had the pleasure of using Pingplotter a short time and what a great tool. Intermittently for a few months now I have been suffering between 5-11% packet loss from Comcast. Comcast keeps telling me to do the usual recycle the model and remove my router and they send out the tech people. The problem disappears for a while and the comes back again. I've used Pingplotter to sample the data in hopes of isolating the problem for Comcast. I'm confused though because it looks like the packet loss occurs everywhere!

What do I tell Comcast with a result like this? I see the Hop 11 and 12 problem but not sure what to make of when there are problems everywhere.

Any help in interpreting this would be most appreciated.

Thanks!

Birdman

Here's more information.

Thanks again,

Birdman <img src="/forums/images/graemlins/grin.gif" alt="" />

Hi, Birdman.

That's pretty bad.

Hop 1 is losing packets - about 20% of them during the period you selected for this screenshot.

Because all packets being sent out have to travel through this hop, all other hops are showing packet loss as well.

The best way of figuring out the source of problems like this is to look at the final destination (www.comcast.net in this case) and identifying the problem (bad packet loss and erratic latency - the latency is pretty bad too). Then, look back to the first hop that exhibits these same symptoms. That's the *source* of the problem.

In your case, this is very easy to identify - hop 1.

I don't know if hop 1 is your cable modem or something inside the Comcast network, but because that's the first hop that shows up in our trace route, that's the closest target, we know that the problem occurs either *at* that hop, or between that hop and your computer. Just to add some "theory" to this: if hop 1 showed as good and hop 2 showed bad, then we'd know the problem we between hop 1 and hop 2 (inclusive).

So, we know the problem is between your computer and hop 1 - including hop 1 as the potential problem.

Based on the IP Address at hop 1, I'm *guessing* this is your cable modem, but I could be wrong - it could be a router inside your network, or it could even be inside Comcast itself.

If possible, you want to understand the network between you and hop 1 so you can talk to Comcast about it after you've eliminated everything under your control.

Example: If hop 1 is a router and hop 2 is your cable modem, then the problem is actually with the router, or a cable - not the cable modem. If this is the case, then Comcast can't do a lot to help since it would be a problem with your equipment.

If, though, your network is like most, then hop 1 is going to be the cable modem. Make sure the ethernet cable between your computer and the cable modem isn't the problem. If you have more than one computer, try running PingPlotter from the other computer to elminiate your computer from the possible problem pool.

If you have a router, hub, or hardware firewall on your network, try elminating that.

Once you're sure the problem isn't with any of your equipment, then you know the problem lies somewhere between your equipment and hop 1. Call in Comcast to help solve the problem now. Send them your PingPlotter graph. Tell them your symptoms. Tell them all the troubleshooting you've already done on your local network.

If you want to respond back here with your network topology between you and hop 1, then we can help identify sources of problems - or you may be able to do this yourself.

Because you know that the problem is between you and hop 1, you want to find a target to trace to that is as close to hop 1 as you can. Often, your mail server is a good option for this. If you can keep the packets inside the local Comcast network, then an uneducated tech can't say "It's a problem with the internet". This is just an optional step you can do to remove one back-and-forth with a technician.

Feel free to post back here with any questions.

Good luck!

- Pete

Hi Pete,

Thanks for the prompt and detailed reply. You the man!

I'm learning about all of this connectivity stuff for the first time so bear with me. I looked into my first hop, 10.xxx.xxx.xxx, and according to this

http://www.faqs.org/rfcs/rfc1918.html

web page the 10 IP's are for private usage like 192.168.xxx.xxx. Perhaps most knew this, but it was news to me. I checked my cable modem (a SB4220) and the closest thing I found to a 10.xxx.xxx.xxx IP address was a "HFC IP Address with a 10.xxx.xxx.xxx. address. This was not the same one that's in Hop 1 of my pingplotter diagram, though.

I also checked forums and perhaps it might be a "CTMS", whatever that is. Someone posted this on broadbandreports.com when someone was trying to their HFC IP Address.

"It was the IP address of the CMTS. The reason it now times out is Comcast has set it to ignore ICMP, which is quite common. Your modem's IP will never show in a traceroute since it functions as a transparent bridge."

Anyway, about my config ... I do have a router, but I eliminated that from the system and used my desktop to ping without the router. Removing the laptop/router does not seem to make a difference regarding packet loss. I do notice, however, that my average pings from the laptop are in the 20s while average pings from my desktop are in the 70s to the same place. Not sure what to make of that either.

Tonight, my pingplotter results appear this way (much shorter time):

So here's another image. Not as bad as the first two but still not very good.

I must admit I'm overwhelmed by all the information, but it still does appear that the first hop is the predominant problem. I'm still trying to get handle on what to do with this information. I have to be very well prepared for that front-line Comcast rep who wil be fixated on telling me to recycle my cable modem and not much else.

I hope this information helps you further. Thanks for the assistance, Pete!

Birdman

This should be investigated. Set up your laptop running PingPlotter and see if it shows similar packet loss and huge latency numbers. If you see different results from two computers running from the same LAN, then that could help you track down the culprit - maybe your computer, or maybe it's a problem with the router and/or cable modem treating different computers differently.

As for reporting to your ISP. Keep a log of problems you run in to (not bad PingPlotter data, but real-life problems). If you have a few real problems, report it to tech support. When they suggest that you reboot, ask them "Is it normal to have to reboot the cable modem every 30 minutes?" Generally, being firm but polite gets you a significant distance. If you don't get the answers you need, ask to talk to their manager. Having real data makes a big difference here. Correlate your real-life problem (timeing out browser, disconnected game, slow page loading, etc) with PingPlotter data and offer to email that to them. Be persistent. Thousands before you have had success getting their problems solved, so just don't give up and you will too. <img src="/forums/images/graemlins/smile.gif" alt="" />

- Pete

Thanks, Pete! I contacted Comcast and was fortunate to speak with a customer service rep who seemed interested in my problem. The pingplotter data had a lot to do with convincing him that the problem was Comcast's and not my own. He gave me his direct email and phone number.

Comcast is (again!) sending out an "inside" tech to check out my computer for the obvious problems like cycling the cable modem and removing the router. Once the inside tech finds that there's nothing wrong on my end, then he calls for a "outside" line tech to come and visit. That won't be for at least a week. Unfortunately Comcast does not allow customers to go straight to the outside tech because I'm guessing they are most expensive. So on Monday I have to go through the charade of having them look at my computer and telling me what I already know.

The process is slow yes... but it is moving. My packet loss peaked out at 25% a few days ago. Today is a relatively light day of only 12% packet loss.

Thanks again for the assistance.. <img src="/forums/images/graemlins/grin.gif" alt="" />

Birdman