[ale] Slightly OT: Reasonable Latency with Comcast Business

[Derek Atkins]

Hi Neal,

I ditto what James says (and was going to say the same thing).  Take a
laptop that you KNOW can handle 1Gb, to be sure it's not a laptop
limitation, and then plug into the router to be sure you can show the
issue from their CPE.  Showing it from the Ubiquiti equipment is not
sufficient.

Also, it helps if you can have a tech on the phone while the problem is
occurring.  I used to have Comcast Biz and would lose network every time
there was a neighborhood power outage.  It took a 3hr outage during the
day and me calling just as the outage stopped for them to find the node
with the bad battery.

So back to your issue.  It looks like it could be a network drop, a DHCP
renew that takes too long, or possibly even an upstream issue with
Comcast.

Expect to spend time trying to reproduce it, especially if it's something
that isn't reliably reproducible.  You might also want to look at
potential buffer bloat, and also explore the possibility of NAT Table
overload.

Having said that, the RTT you see (17ms) is reasonable for a cablemodem
plant.

-derek

On Thu, November 14, 2024 10:41 am, James Taylor via Ale wrote:
> My experience with Comcast Business says that the you need to spend time
> in the furnace room.
> They are going to test from their router and if you don't show the problem
> there, they are unlikely (i.e. - never) to look further.
> -jt
>
> James Taylor
> 678-697-9420
> james.taylor at eastcobbgroup.com
>
>>>> Neal Rhodes via Ale <ale at ale.org> 11/14/2024, 10:36 AM >>>
> This feels like a classic three party finger pointing exercise, and I'm
> doing a bit of research before we jump in.
>
> A couple of years ago, our church put in a sophisticated (at least by MY
> Measure) Ubiquity Unifi Mesh network, mostly to support security camera
> for the community pre-school.
>
> The core is a UDM Pro router, feeding all Ubiquiti stuff.
>
> And it has run totally steady.
>
> Here's the rub: Now that the "Last Guy That Touched it" moved to
> Florida, I'm getting multiple alerts per day to the effect of:
>
> * Your primary internet Comcast Business was disconnected and has been
> restored multiple times in last 24h. If this persists, please try
> restarting your ISP Modem.
> * Primary internet is experiencing high latency. Please restart the
> modem or contact the ISP if this persists.
>
> Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaand, nobody complains. Occasionally,
> I will see Zoom meetings from home where the church participants go
> really fuzzy and blocky, like Zoom has downshifted their resolution.
>
> Apparently it measures ping time to Ping.UI.Com to decide this.
>
> The Unifi Console reports the Comcast Business router as providing
> typical 14ms latency. With the occasional spike to 45ms.
>
> When I ping that address from my Uverse internet from home, I'm seeing
> consistently results from 7ms to 10ms.
>
> I don't know whether to ask Ubiquiti about raising their thresholds, or
> Nag Comcast about their performance. I guess I could ask Ubiquiti
> precisely what does "Internet Disconnected" mean?
>
> My personal experience with Business Comcast in the past has been.......
> not impressive. Usually, a service call just makes it worse. Is
> Comcast going to take my report from Ubiquiti seriously? Or tell me to
> pound sand? What additional evidence need I present?
>
> Yes, I could spend a quality hour in the furnace room, with a notebook
> connected to the LAN side of the Comcast router, (the only way I can
> talk to it) and see what I can see.
>
> I suppose I could just call Comcast, and give up another hour of my life
> to try and talk to someone with a clue.
>
> regards,
>
> Neal
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-- 
       Derek Atkins                 617-623-3745
       derek at ihtfp.com             www.ihtfp.com
       Computer and Internet Security Consultant