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telcodad
Premium
join:2011-09-16
Lincroft, NJ
kudos:17
reply to SallyWingles

Re: [Connectivity] Net Drops Constantly

said by SallyWingles:

Location - Barnegat, NJ
Issue - Constant Connection Drops every few minutes. Mainly noticed while online gaming, viewing movies from service, private network chats, and also Skype.

Cisco DPC3008 DOCSIS 3.0 Cable Modem (Rev 1.0) Bootloader Revision 2.3.1_r3 - d3000-v302r125532-120517a-L2VPN-CMCST.bin - Firmware build date May 17 11:31:04 2012
:
I recently received this modem as the old modem from Comcast was not allowing full speeds. The modems "online light" is always flashing Amber, and I was told by phone tech, this was normal. They said all looks fine on their end. My signals to them are just fine. They suggest it is a router issue.
:
Does anyone have any suggestions or ideas as to why this is happening? Here are the details you may require.
:
Now, we did flood here with Superstorm Sandy. I had to remove all of the insulation under my house, replacing it this weekend. I do run cat cables under the house. I had someone look at the wires, and they said they looked okay. HOWEVER, this problem started a month or two before the storm hit.
I would rather try to make sure there are no KNOWN issues first, then try replacing cat cables, router, and modem last.

If anyone can help shed some light on this I would greatly appreciate your help. Ideas, suggestions, tips, tools, links you name it I'm looking for it!

My Modems Info:

Model: Cisco DPC3008
Vendor: Cisco
Hardware Revision: 1.0
MAC Address: bc:c8:10:2d:de:24
Bootloader Revision: 2.3.1_R3
Current Software Revision: d3000-v302r125532-120517a-L2VPN-CMCST
Firmware Name: d3000-v302r125532-120517a-L2VPN-CMCST.bin
Firmware Build Time: May 17 11:31:04 2012
Cable Modem Status: Operational

Cable Modem State
DOCSIS Downstream Scanning: Completed
DOCSIS Ranging: Completed
DOCSIS DHCP: Completed
DOCSIS TFTP: Completed
DOCSIS Data Reg Complete: Completed
DOCSIS Privacy: Enabled

Downstream Channels
Power Level: Signal to Noise Ratio:
Channel 1: 0.7 dBmV 39.6 dB
Channel 2: 1.1 dBmV 39.5 dB
Channel 3: 1.3 dBmV 39.6 dB
Channel 4: 1.4 dBmV 39.6 dB
Channel 5: 0.9 dBmV 39.4 dB
Channel 6: 0.7 dBmV 39.4 dB
Channel 7: 0.3 dBmV 39.2 dB
Channel 8: 0.2 dBmV 39.5 dB

Upstream Channels
Power Level:
Channel 1: 50.5 dBmV
Channel 2: 49.8 dBmV
Channel 3: 51.0 dBmV
Channel 4: 0.0 dBmV

Well, while your modem downstream power levels and SNRs look fine, the upstream levels are very high. They should not exceed +50 dBmV for a D3 modem with multiple, bonded upstream channels.

Your problem sounds similar to another poster's who also had high upstream levels: »[Connectivity] Motorolla Surfboard SB5100 keeps resetting

You might want to check the condition of all cables/connectors and splitters that lead up to your modem. The modem should be connected to one output of a high-quality 2-way splitter (or maybe the -3.5dB output of a high-quality, unbalanced, 3-way one) connected to the cable as it first comes into your home. See: » Do I need to get an amplifer and active return? and »4 TVs & modem...how to run

A poor-quality splitter can have higher loss in the 5-42 MHz return (upstream) path, so replacing one with a high-quality one could help reduce those high upstream power levels. See: »Re: [Connectivity] Recommended splitter

SallyWingles

join:2012-12-13
Waretown, NJ
My TV started acting up, pixels, stuttering, going very fast, and then slow. I called Comcast, to tell them my upstream info, along with what I've mentioned above and they are sending someone out this Sunday. I will use this information when the tech arrives. I am thinking there is damage from the flooding we had with Superstorm Sandy.

Please feel free to offer anymore advice or tips because I really hope to see positive results when the tech is done.


gar187er
I do this for a living

join:2006-06-24
Dover, DE
kudos:5
reply to telcodad
50 is fine.


telcodad
Premium
join:2011-09-16
Lincroft, NJ
kudos:17

1 recommendation

said by gar187er:

50 is fine.

Oh geez, we're not going to start another debate about what the maximum recommended upstream power level should be, are we? »Re: I think my signals are a little out of wack


NetFixer
Bah Humbug
Premium
join:2004-06-24
The Boro
Reviews:
·Vonage
·Comcast Business..
·Cingular Wireless
said by telcodad:

said by gar187er:

50 is fine.

Oh geez, we're not going to start another debate about what the maximum recommended upstream power level should be, are we? »Re: I think my signals are a little out of wack

I don't know, are we?

said by telcodad:

Well, while your modem downstream power levels and SNRs look fine, the upstream levels are very high.

Personally, I would have used the term "marginally high" or "potentially high", not "very high". Especially since the values shown in a typical cable modem's line stat page are not necessarily accurate.
--
We can never have enough of nature.
We need to witness our own limits transgressed, and some life pasturing freely where we never wander.


telcodad
Premium
join:2011-09-16
Lincroft, NJ
kudos:17
said by NetFixer:

said by telcodad:

said by gar187er:

50 is fine.

Oh geez, we're not going to start another debate about what the maximum recommended upstream power level should be, are we? »Re: I think my signals are a little out of wack

I don't know, are we?

said by ExoticFish:

I would agree that 50-51 is too high. At 50 I had issues.

Well, it's starting to look that way!

said by NetFixer:

said by telcodad:

Well, while your modem downstream power levels and SNRs look fine, the upstream levels are very high.

Personally, I would have used the term "marginally high" or "potentially high", not "very high". Especially since the values shown in a typical cable modem's line stat page are not necessarily accurate.

While I'll agree that "very high" might have been a little too much, if some people are saying that they have had issues when their upstream levels hit 50 dBmV, then it is more than just "marginal." You also have to allow for a few dB of "headroom," given the normal, daily fluctuations most HFC systems experience.


owlyn
Premium,MVM
join:2004-06-05
Newtown, PA
reply to NetFixer
I've lost bonding at 50.25 (50 was the highest working level). At 53, I get disconnected.


NetFixer
Bah Humbug
Premium
join:2004-06-24
The Boro
Reviews:
·Vonage
·Comcast Business..
·Cingular Wireless
reply to telcodad
said by telcodad:

While I'll agree that "very high" might have been a little too much, if some people are saying that they have had issues when their upstream levels hit 50 dBmV, then it is more than just "marginal." You also have to allow for a few dB of "headroom," given the normal, daily fluctuations most HFC systems experience.

I have stress tested my current SB6121 by moving it from its normal -3.5 db splitter leg to a -7 db splitter leg. When on the -3.5 db leg, my upstream levels read ~-45-48 dBmV. When on the -7 db leg, my upstream levels read ~-49-52 dBmV. I have left it on the -7 db leg (with at least one upstream channel at the -52 dBmV level) for multiple days, and my connection remained solid.

I have also tested my old (backup) D-Link DCM202 modem in a similar fashion, and its upstream level readings consistently read ~ 3 dBmV lower on either splitter leg than my SB6121. So, if my old D-Link had started failing at the -50 dBmV reading, would it really have failed at -50 dBmV, or would it have failed at -53 dBmV, or perhaps both of my cable modems are so far off in their readings that it would have actually failed at -55 dBmV ?

Cable modems are not expensive cable line testers, and their line level readings are not to be taken seriously. At best, the day to day readings on the same cable modem on the same connection, are good as a relative measure of conditions on a day to day basis for that specific modem on that specific connection. Those readings bear no real or reliable relationship to actual values measured with a high quality tester.
--
We can never have enough of nature.
We need to witness our own limits transgressed, and some life pasturing freely where we never wander.


telcodad
Premium
join:2011-09-16
Lincroft, NJ
kudos:17

2 edits
Given the variations in the architectures of and equipment used in the various HFC systems Comcast has cobbled together over the years, I would think it is also possible that in some systems (like yours), upstream power levels of 51 dBmV or slightly more may not be a problem, while in other systems (like in ExoticFish See Profile's and owlyn See Profile's), levels that high do cause issues.

The differences between different brands/models of modems can also enable some of them to perform OK at >50 dBmV levels.

Like they say - YMMV.

EDIT: Looks like the upstream power limit is determined by the modem and, as some posters have stated before, the number of upstream channels. From page 3 of the data sheet for the Moto SB6121 (»www.motorola.com/staticfiles/Sup ··· heet.pdf ):
Upstream Operating Level Range Level range per channel:

(Multiple Transmit Channel mode disabled, or only Multiple Transmit Channel mode enabled with one channel in the TCS)
TDMA
Pmin to +57 dBmV (32 QAM, 64 QAM)
Pmin to +58 dBmV (8 QAM, 16 QAM)
Pmin to +61 dBmV (QPSK)

Level range per channel (two channels in the TCS)
TDMA
Pmin to +54 dBmV (32 QAM, 64 QAM)
Pmin to +55 dBmV (8 QAM, 16 QAM)
Pmin to +58 dBmV (QPSK)

Level range per channel (three or four channels in the TCS)
TDMA
Pmin to +51 dBmV (32 QAM, 64 QAM)
Pmin to +52 dBmV (8 QAM, 16 QAM)
Pmin to +55 dBmV (QPSK)


EG
The wings of love
Premium
join:2006-11-18
Union, NJ
kudos:10
reply to NetFixer
said by NetFixer:

Cable modems are not expensive cable line testers, and their line level readings are not to be taken seriously.

Yes !!Exactly !! Perhaps that is why some posters should not constantly and automatically say that "50 dB is fine" ?