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6mo + of subpar gigabit speed, Comcast no help?

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6mo + of subpar gigabit speed, Comcast no help?

I have had 6mo of gbps service, it has never once hit a speed test of 900mbps

usually hits around 400mbps on the local ookla Comcast node

sometimes hits 600mbps on the xfinity test server

 

i tried plugging the wired pc into my modem,  no change

i tried plugging in a Comcast supplied modem, no change 

 

got charged $70 for a visit by a tech where they didn’t fix issue, their test meter said 1gbps - well awesome that’s to a head end server, that’s no use, I should at least be able to traverse to other servers in the colo at 1gbps

 

@comcastcares no help, just ask me same basic questions every time.

can I get some service or a refund on 6mo of gbps service

Expert

Re: 6mo + of subpar gigabit speed, Comcast no help?

The test equipment techs use to check your speed is a handheld computer (similar to a Raspberry Pi) that's running a speed test to http://speedtest.xfinity.com/. Since the tech was able to achieve the proper speeds, it would indicate the problem is with your home network/equipment. If you could give us some details, the community may be able to offer some advice. 



"Keepin' it clean since '09"
I am not a Comcast employee, just a moderator.
Frequent Visitor

Re: 6mo + of subpar gigabit speed, Comcast no help?

Thanks for your interest.

 

I have an Arris SB8200 i own > Unifi USG 3P > Various Unifi Switches > PC with a realtek PCI offboard NIC OR onboard Intel

 

The Arris SB8200 has  channels  1- 31 upstream bonded, with two further channels of 29 and 159 with average SNR ~38db error counts are 0 or low single digits since a reboot last night perfomed by xfinity)

I also tried an official comcast modem.  I hope the communmity can help because i am at a loss.

 

The PC is running Windows 10, currently running on the offboard on the PCI card NIC (i put that in to eliminate the oboard NIC as an issue)

I have tried with all the offloads enabled and disabled - no difference.

I have tried PC plugged straigh into the modem - no difference.

I have tried a comcast modem - no difference.

I have tried difference nics - no difference

I have tried different cables - no difference

the techs replaced all my splitters - no difference

the tech replaced my powered splitter in the basement - no difference

i removed the HD homerun and splitter on the same wall port as the modem - no difference

 

IIRC the engineers test box had it's own cable connection AND he claimed it used difference server than the xfinity speed test we can get to as customers (so they have no resource contention on that server). My assumption this is some sort of caching endpoint close to the head end rather than in the downtown seattle colo.  Also the xfinity  test servers are in some odd locations if you tracert their IP (note the web interface and the actuall test stream seem to come from different servers - the web interface is down in portland, the test stream itself was somewhere north of seattle.

 

As such my dream scenario is for comcast to prove they can get 900MBPs on every test every time over a 30 minute window using a real modem and real computere - not their test device.  Until then i see no evidence this is 'my equipment'.

 

Any help would be appreicated.

Alex

 

Frequent Visitor

Re: 6mo + of subpar gigabit speed, Comcast no help?

I had the tech out, while his gizmo did record a speed of 950mbps first time, over several runs this dropped.

Line was ok.

Then he recalled that the Arris SB8200 doc mention it operating power range for upstream is a narrower band than comcasts acceptable range.

He put a 2db choke/pad to reduce upstream power. (number wen from 40 to 42dBmv; remember bigger number = less signal on that measure).

 

At that point all speed tests connected directly to the modem ran at ~950mbps

Solved.

 

Other observations:

  • Surface book dock 1gbps port can only do about 300mps of real world data transfer.
Expert

Re: 6mo + of subpar gigabit speed, Comcast no help?


@Scyto wrote:

 

He put a 2db choke/pad to reduce upstream power. (number wen from 40 to 42dBmv; remember bigger number = less signal on that measure).

 

As a FWIW, that would be incorrect. Additional overall line resistance / attenuation would actually result in INCREASED / HIGHER upstream power as read by the modem, not lower. But it really doesn't raise what is received at the CMTS. It only makes the power level look prettier at the modem.

 

However additional line attenuation would result in lower DOWNSTREAM power. The up and down power levels work oppositely of each other.