RoanokeCoxUser
@cox.net
|  [VA] Roanoke - Intermittent drop / resync
Long post, apologies in advance...
For a very long time, I've dealt with intermittent drops of modem sync, but lately the other users in the house (one in particular) have gotten more irritable when it happens.
Anyway, the setup is as follows:
Scientific Atlanta Webstar DPC2100R2 connected to a Linksys BEFSX41 router with most recent firmware. Initial support contact basically has said "we won't talk to you to troubleshoot further if you don't remove the router". I am not keen on taking down the router for an unknown period of time since I have the XP firewall turned OFF (prefer hardware solutions over software). However, I'll try to get around to testing the situation without the router over the next few days. It's been a problem for over a year and across two modems (other one was a Toshiba PCX2200), so a few more days of soliciting advice won't hurt.
Anyway, the cabling coming in is RG-6. It goes into a 2-way splitter with one leg going to the modem (and/or another splitter, more on that in a minute), then the other leg goes into a 4-way splitter which goes out to the other TVs in the house. The cable going from the first splitter to the modem (or second split for TV in the same room as the modem) is RG6 and the connecting link between the initial 2-way and the 4-way is RG-6, but only 2 of the 4 runs to the other household TVs are RG-6. The other 2 runs are RG-59, and they are semi-long runs. I haven't measured exactly, but I'd say they are at least 25 foot runs. These are going to TV sets though.
TV Symptom - On the upper channels (60+) some channels have visible noise (ingress?). Not sure. I'm exhausted from work and lack of sleep, so I'll follow up more on that tomorrow.
Question 1) Should I replace the 4-way and the 2 RG-59 links? The 4-way is at least 5 years old and the cables probably older.
Back to the modem issue... When the problem happens, the cable light stays lit for a bit, then it drops and the modem goes through its' resync process. While this is going on, LAN port traffic on the router is fully functional. WAN Link/Act light will blink showing attempted activity and the PC light on the modem is flashing as well. All ethernet cabling is Cat5e or Cat6.
Modem will eventually recover and connection will be restored on its' own. No power cycling of the modem or the router takes place. This happens within a few seconds to a couple of minutes.
Back to the splitter in the room with the modem. I took it out of the picture last night. The initial 2-way splitter down in the basement was replaced this evening. Here is the (minimal) diagnostics that Cox allows me to have with this modem as it is at this moment in time (normal connectivity):
Name
WebSTAR DPC2100R2
Modem Serial Number
xxxxxxxxx
Cable Modem MAC Address
XX:XX:XX:XX:XX:XX
Hardware Version
2.1
Software Version
v2.0.2r1256-060303
Receive Power Level
-1.9 dBmV
Transmit Power Level
43.3 dBmV
Cable Modem Status
Operational
That's all I can get at. I can't get SNR rates and other good stuff. Not sure why. Some of us who understand these things might find them helpful 
From what I have been reading up on, the Receive power level is golden. When I contacted support the first time, with the splitter here in the room in the circuit and the original splitter in the basement, that figure was around -4.8dB. When I took the splitter here in the room off, last night the values were around -3.0dB. I would guess if I put the splitter back on so I can have TV in ths room, I'd be in the -3 to -4.5 range, which from my understanding is still plenty good. Correct me if I'm wrong...
As for the Transmit level, I've seen 48-49dB here and there. I'm lower now because of having a splitter out of the mix.
So, fundamentally, I'm not feeling that the problem will just magically go away by removing the router out of the picture. I could be wrong, but it's just a gut feeling. I think this is a node issue and is one of those "works fine when the technician is looking right at it" issues...
I've had 2 or 3 drops tonight since about 9PM. Some nights it is worse than that. It is not just isolated to nights, but that's when it is noticed more by me.
One other little tidbit of info. I was just recently shuffled into a new IP address block. I used to be in the 68.x.x.x range, now in the 24.x.x.x range and IPv6 translation via Teredo has also kicked in. Cool, but the problem was happening with straight IPv4... Just one of those "hey, isn't that neat" things...
Any thoughts? I'm going to get the router out of the mix probably Saturday or Sunday...
Thanks much, and again, sorry for the length...  |
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daveinpoway
join:2006-07-03
Poway, CA
| Obviously, either turn on the Windows XP firewall or (better yet) download and turn on a 2-way software firewall (such as the free version of Zone Alarm) before taking the router out of the circuit. Many security experts recommend using both a hardware and a software firewall. The 2-way aspect is important (note that the built-in Windows XP firewall is only one-way), since a 2-way firewall can detect if something that might have gotten in (despite your best efforts) is trying to call out to the "mothership".
Nothing connected to the output of the modem (whether it's a router or anything else) can cause the modem to reset, so, if this is happening, something else is wrong (perhaps a bad modem or a noisy input signal; impossible to know from a distance). |
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CoxTech1
VIP
join:2002-04-25
Chesapeake, VA
| reply to RoanokeCoxUser
If you regsiter here on the forums you could PM me your cable modem MAC address and I'll be happy to see how the modem looks from our end.
As far as your wiring configuration goes, I would suggest replacing any RG-59 if you know you have it with RG-6. It will carry signal better over longer distances. 4-Way splitters cause lots of signal loss but if the modem intermittenly loses sync connected off of the 1st splitter there may be a bigger signal problem closer to the source. |
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RoanokeCoxUser
@cox.net
| said by CoxTech1  :If you regsiter here on the forums you could PM me your cable modem MAC address and I'll be happy to see how the modem looks from our end. I sent you a message a little while ago as a registered user.
said by CoxTech1 :As far as your wiring configuration goes, I would suggest replacing any RG-59 if you know you have it with RG-6. It will carry signal better over longer distances. 4-Way splitters cause lots of signal loss but if the modem intermittenly loses sync connected off of the 1st splitter there may be a bigger signal problem closer to the source. What do you mean by "closer to the source"? External wiring, or internal still? |
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BinRoanoke
join:2008-06-19
Roanoke, VA
| reply to CoxTech1
said by CoxTech1 :If you regsiter here on the forums you could PM me your cable modem MAC address and I'll be happy to see how the modem looks from our end. Well, that's wacky. Apparently the forum software won't tag an anon user in the "last" column as a reply... :shrug:
Anyway, I sent you a message.
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BinRoanoke
join:2008-06-19
Roanoke, VA
| reply to RoanokeCoxUser
Well, to update on the situation, the tests showed some T3 timeouts that they can only see from their side, but those have cleared up over the past day. The down side of that is I still got a few drops last night.
The SNR was reported as 37.1, which is above the acceptable level of 30.
Plans for tonight are to check for video problems on the higher channels on my TV. If they are OK, then that says the 4-way splitter and/or the cable runs from the 4-way have some problems. If signal problems are present, then that, at least to me, suggests issues further up the line, which would be either the drop itself or some sort of issue with the line on the pole (external wiring).
One other thing I need to try to do is do a neighborhood walk and see if I can find any other people in the neighborhood who have HSI and see if they are having issues or not. |
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CoxTech1
VIP
join:2002-04-25
Chesapeake, VA | Actually, I stand corrected on SNR. Our current minimum acceptable level is now 35. |
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BinRoanoke
join:2008-06-19
Roanoke, VA
| said by CoxTech1 :Actually, I stand corrected on SNR. Our current minimum acceptable level is now 35. Hmmm... That puts me close to the edge. Is it 3dB for a doubling of strength? I'm rusty on that.
I think I like the idea of dropping the 4-way out of the picture to check for backfeeding. I don't have a terminator, but I would think that an open port would have less interference than a bum 4-way with the associated cabling.
Also, would electrical interference sources / lighting be of any concern? Any capability of testing SNR like up to the filter (or whatever it is) on the line on the pole? |
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CoxTech1
VIP
join:2002-04-25
Chesapeake, VA | The SNR on your modem should be just fine. I can't recall ever seeing one above 39 although I'm sure it's happened before. |
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BinRoanoke
join:2008-06-19
Roanoke, VA
| said by CoxTech1 :The SNR on your modem should be just fine. I can't recall ever seeing one above 39 although I'm sure it's happened before. Update on this situation:
I pulled the 4-way splitter out of the mix last night. It did not make any difference to the SNR.
A rep I chatted with last night indicated that they saw very frequent power cycling of the modem going on, as in a claimed 40-50 an hour (?!?!?!?!). I am not unplugging the thing every 90 seconds, so don't know if that was a misread of the stats or if it was / is really happening.
To attempt to address the power issue, I replaced the power brick going to the modem *AND* have moved that power source onto a UPS, thus providing a conditioned power source as well. As I mentioned I had a Toshiba modem before the Scientific Atlanta modem. The power specs were the same, so I had still been using the brick from the Toshiba modem. Perhaps that brick was going bad or the connector didn't make a real good fit.
Anyway, Receive power levels got as high as -1.0 last night without the splitter in that room being involved. When I added the splitter, I went back to the -4.0 to -4.5 range. Interestingly enough, when I connected the cable going to the TV in the room, that instantly caused a 0.5 to 0.7 drop in the Receive power levels, meaning it went to -4.5 to -5.0. Checking into the cables that are connected to that splitter, they are tri-shield RG-6 and not quad-shield.
So, the lingering cabling question is if there would be any benefit to bumping those up to quad-shield?
I'm also investigating putting a Directional Coupler in the room instead of a splitter. Debating between 4, 6, and 9dB for the tap. No signal degradation seen on my TV set on the upper channels. If I get the DC, I'd run my TV off of the tap and put the modem on the low-loss out port so that I reduce the amount of loss going to it. This morning the Receive power level was creeping towards -6.0 and the Transmit power was around 49. I'd like to keep the Receive down in the -4 to -5 range (if possible) and the Transmit in the 43 to 47 range...
Opinions?
CoxTech1 said they were off until Monday...so anyone else feel free to jump in if you have any thoughts on the issue.
Thanks! |
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CoxTOC1
join:2007-05-15
Newport News, VA | If you want to shoot a PM to me with your MAC address (And if possible a brief summary of what other techs have done/told you) I'll take a look at it. |
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BinRoanoke
join:2008-06-19
Roanoke, VA
| said by CoxTOC1 :If you want to shoot a PM to me with your MAC address (And if possible a brief summary of what other techs have done/told you) I'll take a look at it. Sent message just a minute ago... |
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daveinpoway
join:2006-07-03
Poway, CA
| reply to CoxTech1
I seem to recall reading someplace (can't recall just where right now) that a cable modem does not directly measure the downstream S/N ratio, but it calculates this ratio based on the amount of error correction it needs to do. Do you know if this is correct?
If it is true, then it would seem reasonable that different model modems might report a slightly different S/N ratio value, depending on how they do the calculation. I know that my DLink DCM-202 always reports a S/N ratio that is a few dB less than my Motorola SB5120 shows. The DLink is showing between 33 and 34 dB, which is less that your stated minimum of 35, but I assume this is sufficient, since a tech was just here a few days ago and measured everything (his meter is probably more accurate than the modem's reading). |
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BinRoanoke
join:2008-06-19
Roanoke, VA
| reply to RoanokeCoxUser
Update on the situation:
Service call scheduled for Monday. Have been told that the node-wide statistics for Transmit Power is a bit on the high side (49). For the past 12-18 hours, Transmit power has been 50-52. Had 2 resets back to back about 30 minutes ago. Tried to get in touch with support and got a very, very, very inexperienced 1st level person who did not understand that I did not want them to do any troubleshooting at all, only tell me what the modem logs said. They finally gave me 2 lines, one of which I believe was an unrecognized OID and wanted to do the ole' "get the router out of the way and mess around with your network connection in the OS", which I did not do... The rep said that their supervisor told them to tell me to just wait until Monday...
If the people over in the Glendale, AZ, thread are running into these types of "support reps" on a regular basis, it is no wonder they are frustrated. The person I chatted with seems like a typical "after-hours" script reader, perhaps even a 3rd party support vendor. Even when I said that all I wanted them to do was to tell me what the log said, that request was not listened to and they still wanted to go down the path of "fixing it" by a cookie-cutter response.
To the two reps in this forum, what I'm saying does not apply to you. Both of you have been great!!! However, as the general population starts getting more and more tech saavy, the "warm body and a script" approach to tech support is not going to be acceptable. The level of customer service will become more and more of a consideration for customers when they decide who they want to send money to every month. Obviously it depends on if there is choice available.
I'm not planning on going this route, but as an example, there is a choice here. This house is only about 0.5 - 1.0 miles from a Verizon CO. That CO has a digital MUX built into the switch, which is why I always used to get very good V.90 rates (usually 48,000 or 49,333). DSL is available through that CO.
Just some thoughts for any higher-up that may read through these forums from time to time... Increase the quality of support. It will keep more customers happy, and happy customers mean more income, both for the company and (usually) for you as well. |
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BinRoanoke
join:2008-06-19
Roanoke, VA
| reply to RoanokeCoxUser
Update:
Service call happened last week. Modem was replaced as well as the line from the tap to the grounding block and the grounding block itself. Service has been fine for the past week. Signal levels are -1.0 to -3.0 Receive / 44 to 46 Transmit.
Still contemplating getting a Directional Coupler for the room with the modem in it. That will give another 1 or 2dB of signal, but things are fine as they are for now... |
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Putter5
@rogers.com
| reply to RoanokeCoxUser
I'm having the exact same problem problem with the exact same modem (and though I had shrugged off the channels being fuzzy, now that I mention it my low-number channels are not right).
Is replacing the line and the grounding block something I could do myself or should I have a technician do it?
Thanks. |
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CoxTOC1
join:2007-05-15
Newport News, VA | You should have a technician do it! I would hate to see you mess something up and take out you entire neighborhoods services by accident! |
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Putter5
@rogers.com | That was fast...
I didn't know it was that kind of deal.
Is there any chance it's just the modem?
Thanks for the fast reply. |
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CoxTOC1
join:2007-05-15
Newport News, VA | If you register and PM one of the techs here we'll be happy to look into it. But if you're seeing fuzzy channels it's most likely a ingress/wiring issue. |
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