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Very slow wired network download speed

Frequent Visitor

Very slow wired network download speed

Hello,

 

Lately my download speeds have dropped significantly (averaging between 2 to 4 mbps).  My upload speeds appear normal (betwen 10 to 15 mbps).  I recently reset my computer and upon reset, the download speeds were initially above 200mbps (where it should be).  When I checked the next day, they had reverted to the 2 to 4 mbps range.  Wifi works fine... it is only on the wired network in which my computer is connected.  

 

I have tried a new CAT6 network cable (also a CAT5).  Any help would be greatly appreciated.  I have tried the standard reset the model and etc (which I'm why I 'm posting here, trying to avoid spending 2 hours on phone with tech support going through all the motions).  

 

My network info below.  Thanks!

 

Cable Modem

HW Version:1.0
Vendor:Scientific-Atlanta, Inc.
BOOT Version:3.4.22.4
Core Version:3.12.14
Model:DPC3941T
Product Type:XB3
Flash Part:128 MB
Download Version:DPC3941_2.6p6s2_PROD_sey
Serial Number:283060959
Downstream
Channel Bonding Value
Index
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Lock Status
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Frequency
615 MHz
591 MHz
597 MHz
603 MHz
609 MHz
621 MHz
627 MHz
633 MHz
639 MHz
645 MHz
651 MHz
657 MHz
663 MHz
669 MHz
675 MHz
681 MHz
SNR
40.366 dB
38.983 dB
38.983 dB
38.983 dB
38.983 dB
38.983 dB
38.983 dB
38.983 dB
38.983 dB
38.983 dB
38.983 dB
38.983 dB
38.983 dB
38.983 dB
38.983 dB
38.605 dB
Power Level
-2.400 dBmV
-2.200 dBmV
-1.800 dBmV
-1.800 dBmV
-2.000 dBmV
-2.700 dBmV
-2.700 dBmV
-3.000 dBmV
-3.200 dBmV
-3.100 dBmV
-3.000 dBmV
-3.000 dBmV
-2.900 dBmV
-3.200 dBmV
-3.500 dBmV
-3.900 dBmV
Modulation
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
Upstream
Channel Bonding Value
Index
1
2
3
4
Lock Status
Locked
Locked
Locked
Locked
Frequency
36 MHz
23 MHz
17 MHz
30 MHz
Symbol Rate
5120 KSym/sec
5120 KSym/sec
5120 KSym/sec
5120 KSym/sec
Power Level
51.500 dBmV
50.000 dBmV
50.000 dBmV
51.500 dBmV
Modulation
64 QAM
64 QAM
64 QAM
64 QAM
Channel Type  
Diamond Problem Solver

Re: Very slow wired network download speed

The upstream power is borderline / too high and may be intermittently fluctuating even higher out of spec. That can cause random disconnects, spontaneous re-booting of the modem, and speed and latency problems.

In a self troubleshooting effort to try to obtain better connectivity / more wiggle room, check to see if there are there any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1002 MHz, bi-directional, and no gold colored garbage types like GE, RadioShack, RCA, Philips, Leviton, Magnavox, and Rocketfish from big box stores like Home Depot, Lowes, Target, Wal-Mart etc. Splitters should be swapped with known to be good / new ones to test.

If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two way splitter connected directly off of the drop from the street/pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed, and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.
Frequent Visitor

Re: Very slow wired network download speed

I just tried plugging the cat cable into a different ethernet output jack on the cable modem... and sure enough, my speed returned to normal.  Prior to doing this I ran a test on speedtest.net and it was about 2mbps.  After doing this, it was registering about 190mbps.  I tried the other ethernet jack, and normal results as well.  It just appears the 1st one I was using is getting the poor results.  Does this means the problem is with my cable modem?  

 

That said, I looked at my stats, and my upstream powerlevel is still at 50.  I don't have any splitters.  It goes from wall to modem to computer.  Modem has two outputs.  First to the computer, second is to the playstation in living room.  Does this mean there should still be concern?  Should I call comcast to send a tech out, or switch out my modem first?  Any other suggestions?

 

Upstream
Channel Bonding Value
Index
1
2
3
4
Lock Status
Locked
Locked
Locked
Locked
Frequency
36 MHz
23 MHz
17 MHz
30 MHz
Symbol Rate
5120 KSym/sec
5120 KSym/sec
5120 KSym/sec
5120 KSym/sec
Power Level
50.000 dBmV
50.000 dBmV
50.000 dBmV
50.000 dBmV
Modulation
64 QAM
64 QAM
64 QAM
64 QAM
Channel Type        
Diamond Problem Solver

Re: Very slow wired network download speed

Good to hear but the high upstream power still needs to be addressed. It's a problem just waiting to happen. Try the tips. Good luck !

Frequent Visitor

Re: Very slow wired network download speed

Sure enough - my internet has slowed to 2 to 4 mbps download speeds.  This makes it impossible to watch streaming, and very frustrating to browse the internet.  Note, both services are on a WIRED connection, direct from cable modem.  I have no splitters.  What's more frustrating, I called comcast a few weeks ago, and the tech insisted they were doing upgrades in my area and that is what was causing the slow speeds.  It seems he was no giving me correct information.  

 

How do I go about addressing the upstream power?  I am not optimistic about calling comcast again just to get the run around...

Frequent Visitor

Very slow wired network download speed Round 2

Hello,

 

I posted about 2 months ago regarding a very slow donwload speed.  I fixed the problem by plugging my wired connection into a different port on the cable modem.  That worked, until a few weeks ago.  My upsteam power levels are 50 dbmv, and on the last post, that was identified to be a problem that would cause my issue to come back.  Sure enough, I'm back.  I've called comcast once, but the rep insisted my issue was currently being worked on and would be fixed that night.  It wasn't.  I'd much rather not deal with calling them again.  Anyone experience this before?  FYI, when my download speeds are normal, I average around 210 mbps.  Now, I'm reaching 2 to 4 mbps.  

 

Thanks for any help you can provide.

 

Previous thread here: http://forums.xfinity.com/t5/Your-Home-Network/Very-slow-wired-network-download-speed/td-p/2933460

 

 

Official Employee

Re: Very slow wired network download speed

 

Hello drewguitar, I ran some tests on your lines coming from the pole and the lines in your neighborhood. I show that the signal coming from the plant is excellent, on the other hand the signal coming from the pole outside is not up to par. I can send a signal to try and correct the noise issue in your line, but a tech may be needed. In order to send the signal I will need to verify your account, can you please send me a private message with your full address, account number, and the name on the account by clicking my name (ComcastAmir) and then clicking "private message me"?

Diamond Problem Solver
Moved:

Re: Very slow wired network download speed