[ale] Slightly OT: Reasonable Latency with Comcast Business

Thu Nov 14 11:52:55 EST 2024

You may also find it helpful to have something specific to check for DNS
resolution.  In some systems/cases the failure to resolve an FQDN used as
part of the check will show up as a generic "no/lost connection".  Provided
the system has the capability a set of hosts to test to could be something
like localhost, the LAN default gateway, the modem's default gateway, the
FQDN the system uses by default for testing, and a well known IPv4 endpoint
like Google's 8.8.8.8.

On Thu, Nov 14, 2024 at 11:25 AM Derek Atkins via Ale <ale at ale.org> wrote:

> What concerns me is the "empty" part of your graph..  At the 45ms peak,
> there appears to be a section of "no response".  Note that depending on
> the service being used, it's possible that the service is down.
>
> FWIW, I run mrtg to monitor my network -- I run pings to several different
> places to test latency across my uplink.  Specifically, one place I ping
> is my 1st-hop upstream router.  If that router goes down or doesn't
> respond, it is 100% correlated to my connection being down for everything.
>
> Of course, YMMV.
>
> -derek
>
> On Thu, November 14, 2024 11:08 am, Neal Rhodes via Ale wrote:
> > Thanks for the reply.
> >
> > I just got off the phone with Comcast.   To my delight it only took 12
> > minutes total.
> >
> > Their criteria is, they don't get concerned until:
> >
> >       * Packets get lost;
> >       * Latency exceeds 100ms.
> >
> > To which I can only say, wow.
> >
> > Comcast tech also says I should reboot their router.  (uptime over 140
> > days.)
> >
> > My bet is the Ubiquiti router has much tighter assumptions.    Next I
> > need to ask them precisely what their criteria is for concluding
> > disconnection.
> >
> > regards,
> >
> > Neal
> >
> > On 2024-11-14 10:56, Derek Atkins wrote:
> >
> >> 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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> > Ale at ale.org
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> >
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>
> --
>        Derek Atkins                 617-623-3745
>        derek at ihtfp.com             www.ihtfp.com
>        Computer and Internet Security Consultant
>
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