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Speed "Issue" And "No Ranging Response Received - T3 Time-Out"?

Frequent Visitor

Speed "Issue" And "No Ranging Response Received - T3 Time-Out"?

About 12 months ago, we bought this Motorola SB6120 SURFboard (instead of renting it from Comcast). We hooked it up and it works since then.

 

Recently, I felt that the connection is slower than usual. So, I ran some speed test. For the Performance Plan w/ a DOCSIS 3 Modem, I would say the speed on paper is alright (20.41/3.24Mbps at http://www.speedtest.net/ OR 17.19/2.76Mbps at http://speedtest.comcast.net/). But the thing is that the download speed is so non-uniform. During the test, I can see that the speed is generally at about 5Mbps; but then with a few burst of 700Mbps to "increase" the average. I know some one with the same Comcast Performance plan, but their 20Mbps is steady.

 

For that reason, I decided to go to http://192.168.100.1 and check out the log. It has a bunch of "No Ranging Response Received - T3 Time-Out" and "critical" logs. I have no idea what they mean...

 

So, my questions are:

1. Is the speed normal? Even with that sort of non-uniformity?

2. Is my modem okay? Is it failing?

3. Are these two things related?

 

I haven't called Comcast yet, because I know their tech likes to blame it on the modem. So, just wanna get some advice from here before calling in.

Frequent Visitor

Re: Speed "Issue" And "No Ranging Response Received - T3 Time-Out&quot

New Poster

Re: Speed "Issue" And "No Ranging Response Received - T3 Time-Out&

No rng-rsp can either mean an upstream or downstream issue. The modem sends an RNG-REQ and the cmts responds with an RNG-RSP. Either the cmts is not seeing your modems request, or the cmts is sending the response and it is getting corrupted along the way, resulting in a T3 timeout as the modem thinks it is not receiving it. Based on your info of fluctuating DL speeds, i would suspect you have a downstream issue. go back into the modem GUI page and look at the downstream information. You should see your downstream frequencies in the 560mHz -590mHz range or so. The MER ( or may be listed as SNR ) should be 38 or 39.

Your downstream receive should be close to zero ideally, but is more than likely between zero and -10. If it is closer to -15 you need to have that improved. Check all your cable connectors at the wall plate and back of your modem and make sure they are as tight as you can get them with your fingers. Connectors are everything in cable and loose ones can certainly degrade your MER and Transmit power. It won't grossly affect your receive power though unless it super loose. See what you can find, but if all you see poor MER and downstream receive, you will probably need a trouble call to have your drop and tap levels investigated.

Expert

Re: Speed "Issue" And "No Ranging Response Received - T3 Time-Out&quot

Please give us more information:

1) Please connect your computer directly to the modem via Ethernet ( no router, no wireless, no USB )
2) Run ShaperProbe and post your results. (It works with Win 7)
3) Post your upstream and downstream signal levels (click the link.) We are interested in your power levels (dBmV) and your Signal to Noise Ratio (SNR).
4) Let us know to what speed tier you subscribe.
5) Post the make a model of your modem.
6) Post your modem's error logs.


I am not a Comcast employee, just a moderator. Pls observe Wheaton's Law.
Frequent Visitor

Re: Speed "Issue" And "No Ranging Response Received - T3 Time-Out&

RE: i-am-nerdburg

 

2. ShaperProbe Result (Is this what you looking for or there is a log somewhere?):

DiffProbe release. January 2012. Build 1008.
Shaper Detection Module.

Connected to server 74.63.50.40.

Estimating capacity:
Upstream: 4222 Kbps.
Downstream: 22705 Kbps.

The measurement will take upto 2.5 minutes. Please wait.

Checking for traffic shapers:

Upstream: Burst size: 4354-4422 KB;
Shaping rate: 2128 Kbps.

Downstream: Burst size: 9590-10097 KB;
Shaping rate: 12768 Kbps.

For more information, visit: http://www.cc.gatech.edu/~partha/diffprobe

3. Signal Info: https://dl.dropbox.com/s/j3e69d7aakaquoj/UpDown.jpg

4. Speed Tier: Performance w/ Powerboost

5. Model Model: Motorola SB6120 SURFboard

6. Error Log: https://dl.dropbox.com/s/s95dgiygf5jwzz8/Log.jpg

Frequent Visitor

Re: Speed "Issue" And "No Ranging Response Received - T3 Time-Out&

RE: mangrovejack

 

https://dl.dropbox.com/s/j3e69d7aakaquoj/UpDown.jpg

 

One of the four channels is out that frequency range (at 555 MHz).

All SNRs are around 36-37, which is a bit lower than your number.

Is Downstream Receive same as Downstream Power Level? My Downstream Power Levels are either 0 or -1 dBmV.

 

So, what do you think?

Expert

Re: Speed "Issue" And "No Ranging Response Received - T3 Time-Out&

At the time you ran the speed test ShaperProbe reported that you have a sustained speed of 12/2 and burst speeds of 22/4 - so your speeds were right on the money. Your signal levels/SNR is just about perfect. The only tell I see are those T4 timeouts in your error log that are causing the modem to reboot. This suggest an intermittent signal problem.

 

What you'll want to do from here is to check your levels when you feel things are not performing correctly. Use ShaperProbe instead of the Flash-based speed test as well. IF you see significant fluctuations, you'll want to call for a tech.


I am not a Comcast employee, just a moderator. Pls observe Wheaton's Law.
Expert

Re: Speed "Issue" And "No Ranging Response Received - T3 Time-Out&


chius0313 wrote:
One of the four channels is out that frequency range (at 555 MHz).

All SNRs are around 36-37, which is a bit lower than your number.

Is Downstream Receive same as Downstream Power Level? My Downstream Power Levels are either 0 or -1 dBmV.

 


It's fine. Nothing to worry about there.


I am not a Comcast employee, just a moderator. Pls observe Wheaton's Law.
Diamond Problem Solver

Re: Speed "Issue" And "No Ranging Response Received - T3 Time-Out&


mangrovejack wrote:

 

The MER ( or may be listed as SNR ) should be 38 or 39.

 

That's a bit of a stretch in my experience. We more typically see 34-35 dB here without issue.


Your downstream receive should be close to zero ideally, but is more than likely between zero and -10. If it is closer to -15 you need to have that improved. investigated.

 

This is actually tighter now in most upgraded to DOCSIS 3 systems. -7 to +7 is now the desired range with -10 to + 10 being the outer fringe.

 

I think that the uSNR deserves a mention here as well and needs to also be taken into consideration.


 

Diamond Problem Solver

Re: Speed "Issue" And "No Ranging Response Received - T3 Time-Out&


i-am-nerdburg wrote:

chius0313 wrote:
One of the four channels is out that frequency range (at 555 MHz).

All SNRs are around 36-37, which is a bit lower than your number.

Is Downstream Receive same as Downstream Power Level? My Downstream Power Levels are either 0 or -1 dBmV.

 


It's fine. Nothing to worry about there.


Agreed.

New Poster

Re: Speed "Issue" And "No Ranging Response Received - T3 Time-Out&

It is fine. When i replied to your post I thought I was on a local forum and gave you the frequency range of our system. The levels arnd SNR are fine. One thing that concerns me is the first channel has a 36 MER vs the 37's of the other 3, and also has the highest corrected codewords. Your internet and vod carriers are bundled together into a narrowcast package and are combined with the broadcast tv channels and transported to your node and onto your house. If the last broadcast channel and first internet channel are not combined with the same levels it can lead to degraded MER and BER issues. There is no way for you to tell this by yourself. You would have to have a techician check. Assuming this is fine, it is also possible that there is some off air ingress @ 555mHz that is slightly degrading that channel only.

Diamond Problem Solver

Re: Speed "Issue" And "No Ranging Response Received - T3 Time-Out&


mangrovejack wrote:

 

One thing that concerns me is the first channel has a 36 MER vs the 37's of the other 3, and also has the highest corrected codewords. 

 


A single dB variance is nothing. Neither is that slight increase in corrected codewords. Can the accuracy of a modem's measuring mechanism compare to that of an SLM ?

New Poster

Re: Speed "Issue" And "No Ranging Response Received - T3 Time-Out&

No, the modem diagnostic is not as accurate as the meter. I was stating that if i was at the TC, that is what I would be checking for. The single dB of difference between 36 and 37 is not a panic by any means, but what if the MER at the node @ 555mHz is 39 and 36 @ the modem. Still think there is nothing of concern? It is just information for the customer to prompt a service tech to check should they feel their service quality needs a trouble call in the future. In our system we have 38.7 MER on chsi carriers routinely at the node. On its own, a 36 MER is perfectly fine for that channel unless the bits are failing. I don't care what the SNR says it is if the bits aren't making it. That screenshot from the GUI leads me to want to check the BER for the narrowcast, that's all I was saying.

Diamond Problem Solver

Re: Speed "Issue" And "No Ranging Response Received - T3 Time-Out&

Fair enough..

Frequent Visitor

Re: Speed "Issue" And "No Ranging Response Received - T3 Time-Out&

mangrovejack, i-am-nerdburg, and EG, thanks for your input. You guys are quick, knowledgable, and helpful. Thanks Smiley Happy
Diamond Problem Solver
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Re: Speed "Issue" And "No Ranging Response Received - T3 Time-Out&

Diamond Problem Solver

Re: Speed "Issue" And "No Ranging Response Received - T3 Time-Out&

Year and a half old thread closed.