Visitor
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9 Messages
Intermittent connectivity problem: T-3 Timeout and MDD Timeout
I've been dealing with Xfinity on the phone and online and seem to be dealing with folks who don't understand the issue, so they give me routine try-this and try-that advice. I'm trying to figure out if a tech needs to come out or if there's anything I can do. The issues have come up after Xfinity emailed me to suggest I upgrade my modem to one on their current approved list in order to get the 400 Mbps my plan now provides. I did as suggested and ever since have had problems that get better and worse. Sometimes I get 400+ but other times the speed is down in the single digits and regularly I get T-3 Timeout and MDD Timeout warnings. Had lower high speeds with the prior modem (Netgear C3700) but the problems occur only now with the newer one (Moto MB7621). Here's the Downstream Ch. Data. The high Uncorrected on 21 and 22 happens regularly and I don't know if this is a red flag.
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Accepted Solution
EG
Expert
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111.5K Messages
2 years ago
The upstream power is too high (already out of spec on channel #5). Some of the downstream channels have an impairment as well. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.
In an 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 5-1000 MHz, bi-directional, and no gold colored garbage from Radio Shack, Home Depot, Target, etc. Splitters should be swapped with known to be good / new ones to test.
Also check the coax cable for any damage such as cuts, nicks, abrasions, kinks, sharp bends, etc.
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.
Good luck with it !
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user_7903a5
Visitor
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9 Messages
2 years ago
Here's the Upstream:
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user_7903a5
Visitor
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9 Messages
2 years ago
I get Event Log warnings including:
Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;.....;CM-QOS=1.1;CM-VER=3.0;
and
No Ranging Response received - T3 time-out;.....;CM-QOS=1.0;CM-VER=3.0;
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user_7903a5
Visitor
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9 Messages
2 years ago
Problem was on the pole. The coupling was physically obviously damaged. New coupling and the system is running fine.
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EG
Expert
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111.5K Messages
2 years ago
Glad it got squared away ! For curiosity's sake, would you please post what the signal stats look like now ?
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user_7903a5
Visitor
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9 Messages
2 years ago
Hi EG, here's the "after". Looks much better to me and thanks for your help!
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EG
Expert
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111.5K Messages
2 years ago
Quite welcome ! The downstreams are good ! The upstreams are on the high side. There's not much wiggle room if they drift upward. They may do so when the heat of the Summer season returns. Bottom line. Live with it for a while and see. Hope things hold up for you. Good luck !
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user_7903a5
Visitor
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9 Messages
2 years ago
EG, re "upstreams are on the high side" would putting a splitter in line to bring these down work? Or I could add a short coax between the lightning surge and modem as I used to do (right now its screwed right onto the modem's coax male input). Or am I barking up the wrong tree becasue here there is nothing to be done on the user end about this? Also what's the optimal range for the upstreams? Thanks.
(edited)
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EG
Expert
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111.5K Messages
2 years ago
No. A splitter will make them higher, not lower. The upstream and the downstream power work in opposite ways when it comes to overall line attenuation. You need to remove excess attenuation, not add more. 40 to 45 dB is the sweet spot for the upstream power level.
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user_7903a5
Visitor
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9 Messages
2 years ago
That's quite interesting, EG. I didn't realize a splitter would increase upstreams. I didn't used to have a splitter at the outside junction box, but at this last service call one was added by the tech. I used to have one inside but had removed it when looking to isolate the previous problem (which turned out to be at the pole, not in my place). I have a pretty long single run of maybe 80 feet from the outside junction box to my modem. Would it make sense to remove the outside junction box's splitter, which is acting just as an attenuator, let the higher power feed the long run, and then add the splitter back inside, closer to the modem? Or not add it back at all and run un-attenuated and then check the levels at the modem? What would you try next to optimize the levels?
(edited)
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EG
Expert
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111.5K Messages
2 years ago
Remove any unneeded splitters and see. A clean straight run is best !
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