this was the main reason i got away from comcast. the guy that comes out
to fix a problem is lower than level 1 support. he is somewhere between
a supermarket sacker and and parking lot shopping cart retriever. they
hook up their little box to your connection in the house, look at the
signal. then do the same test outside your house and then do the same
thing at the pedestal in your backyard somewhere. with those 3 values he
comes up with 'the problem is the wiring in your house' or 'you have a
bad modem'. at this point he would swap out the modem and then do one
test in your house and say its working fine and leave. of course this
has not solved anything. or.... he comes up with the next thing... the
problem is on the pole and i have to call for a lineman to come out.
mind you... you have already waited 3-4 days for this first service
call. it will be 3-4 more days for the lineman to come out. the lineman
goes to the amplifier up on the pole and says its overheating and tweaks
it a bit. then things seem to work fine for awhile until the weather
changes and then you go down again.
i went with at&t first with adsl and then with uVerse when it came to my
area. did it for one reason and one reason only. when you call for tech
support and they have to come out, they come out the next day (except
sunday). they fix it right then. if your a pair from the pedestal is
bad, he hooks you up to another pair in the pedestal. always a fix that
can be done and it is done. i am quite happy with 12meg downstream, i
would be even happier if it were cheaper for 6meg downstream. 125meg
down, take a look at what you are using and i bet you have a ton of
bandwidth unused. i think when i looked at walmart's vudu video
streaming, they require 3meg down for standard def, 6meg down for high
def and 10meg down for super high def. so my 12meg is just fine for most
things. i think most people think the faster their speed the better.
however, they charge you more and more for the faster speed and try to
convince you that it is absolutely necessary to be able to watch tv and
surf the internet at the same time.
back in the day i had a bonded isdn line to my house. this was when that
was as almost not heard of. problem back then was that isdn did not give
a line level signal on the line when tested and other repair techs would
swap out someone's bad line for your nice clean line. when they
installed them back then they had to red tag the line all the way back
to the central office so that no one touched it. was a great plan.
now-a-days they are a bit more careful as almost everyone has adsl or
uVerse on the phone lines and they have a few people out there with a
real pots line.
73...bruce
On 3/31/2016 8:40 AM, Bill Crowell via BVARC wrote:
Hi All,
I’m writing this note in the hope that it will help other hams not
have to waste hours with the level 1 support people over this issue.
Yesterday, my connection was dropping more than usual. I was losing
data. And, for those who don’t know me, I’m very competent in the ways
of networking.
We all go to some site like speedtest.net to see what our speed is. I
have the Xfinity BLAST service that gives me up to 125Mbps downstream.
That doesn’t tell the whole story. The upstream speed and reliability
are just as important. This is because the protocols used for most
traffic are TCP and the link layer is wanting an ACK packet (among
others.) If the ACK packet is not received, the link retries. And,
when things get bad, the entire channel is spending all of its time
thrashing.
To test link integrity, I started running a ping to my server in
Dallas. You can do this on Mac or Linux rather easily. Windows ping
gives you only 4 pings by default. I’m sure that someone who is a
Windows person will give the appropriate syntax for a continuous ping.
You can ping a DNS server at 4.2.2.1.
So, start a ping to a target computer somewhere. THEN do the speed
test. If you see “request timed out”, you’re having an upstream issue.
Now to my equipment. I’m running a Motorola 6141 cable modem. This has
been the very best modem for a long time. I don’t pay Comcast for
their piece of junk. The modem connects to a Juniper SSG5 firewall and
then to my network. This is a DOCSIS 3.0 modem. What this means is
that it gets configuration settings from Comcast. These settings
include which channels to bond for the downstream and upstream
connections._What I had not realized is that the network sets the
TRANSMIT power levels of the modem._
During the protocol negotiation and then periodically, the ISP’s gear
will tell the modem to increase or decrease power. If the receive
signal strength is too low, Comcast will tell my modem to “QRO old man”.
You can see the RF side on the Signal page of the modem. This is the
Motorola:
I’ve got one, measly channel and the modem is just below it’s absolute
maximum power of 57dBmV!!!! Yesterday, it was at 57 dBmV all day. This
is when packets are definitely lost.
The downstream channels are all fine at 0 dBmV – parity.
Now, how to correct this. Ideally, Comcast would deal with the RF link
between the modem and their gear. They’re sending someone next week.
They’ll likely say that the splitter should be removed, but then I
have to choose between TV and Internet. You know the drill.
For those of you not paying attention, the whole system is digital and
this issue manifests itself with the digital TV as well.
What is needed is to even out the TX/RX levels. I’m not expecting the
$15/hour tech to understand this. So, I’m getting an amplifier
designed for this purpose. The key here is “active return”. That’s the
part where the amp boosts the upstream signal from the cable modem.
The splitter is being replaced with this:
https://www.amazon.com/gp/product/B003T2SLIO/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
I’m expecting the TX power to be a more reasonable 30-40 dBmV and the
problems to disappear.
73!
Bill
Bill Crowell, N4HPG
Pearland, TX
Text messaging one-handed since 1982
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Bruce Paige, KK5DO
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