Digitel - High number of TX errors

Digitel - High number of TX errors
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bbplumber @ 14th Jan 01:38PM:
Digitel - High number of TX errors

Hi all,

I've been asked to provide some remote support for a sister-in-law's DSL line. She's been having very poor performance on her circuit. When using voip applications she repeatedly gets cut off, slow web browsing in some cases, etc.

Not being a DSL guru myself, I saw something on her interface stats that surprised me:

On the WAN facing interface I saw a large # of Transmission errors. It was on the order of 95,000 errors vs 287,000 TX packets. No errors on the RX side

Anyone know what a Transmission error is? What is the cause of that? The only thing I could think of is this may occur when trying to send more traffic then the service profile is set to? Otherwise, if the modem knows something is bad or in error, why would it send out a bad cell?

She has some kind of prolink DSL modem, if that helps.
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sashwa @ 14th Jan 03:16PM:
Re: Digitel - High number of TX errors

How about some more info - Her ISP, what model modem, router, voip applications, etc.
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bbplumber @ 16th Jan 11:28AM:
Re: Digitel - High number of TX errors

ISP: Digitel Philippines (out of Bulacan)
Modem: Prolink Hurricane 9200AR
Using that as router + WRT-54g (issue appears whether router is there or not)
VOIP applications: SKYPE, MagicJack, Ichat
Experiences Stalls, freezes, etc when using safari or firefox, long delays when waiting to contact server.

When I do a traceroute from her PC, I see large latency to the first router, and a large amount of jitter.


traceroute to www.cnn.com (157.166.226.25), 64 hops max, 40 byte packets
 1  www.cnn.com (157.166.226.25)  1.958 ms  1.878 ms  1.785 ms
 2  dsldevice.domain.name (192.168.1.1)  3.191 ms  2.875 ms  3.013 ms
 3  124.217.52.1 (124.217.52.1)  404.889 ms  718.402 ms  715.541 ms


traceroute to www.l.google.com (74.125.95.104), 64 hops max, 40 byte packets
 1  iw-in-f104.google.com (74.125.95.104)  2.589 ms  1.841 ms  1.851 ms
 2  dsldevice.domain.name (192.168.1.1)  3.348 ms  2.946 ms  2.820 ms
 3  124.217.52.1 (124.217.52.1)  252.796 ms  71.483 ms  95.817 ms

When pinging, I don't seem to be experiencing any packet loss.


PING 124.217.52.1 (124.217.52.1): 56 data bytes
64 bytes from 124.217.52.1: icmp_seq=0 ttl=253 time=66.527 ms
64 bytes from 124.217.52.1: icmp_seq=1 ttl=253 time=261.887 ms
64 bytes from 124.217.52.1: icmp_seq=2 ttl=253 time=159.540 ms
64 bytes from 124.217.52.1: icmp_seq=3 ttl=253 time=627.747 ms
64 bytes from 124.217.52.1: icmp_seq=4 ttl=253 time=446.558 ms
64 bytes from 124.217.52.1: icmp_seq=5 ttl=253 time=391.545 ms
64 bytes from 124.217.52.1: icmp_seq=6 ttl=253 time=338.709 ms
64 bytes from 124.217.52.1: icmp_seq=7 ttl=253 time=209.700 ms
64 bytes from 124.217.52.1: icmp_seq=8 ttl=253 time=90.344 ms
64 bytes from 124.217.52.1: icmp_seq=9 ttl=253 time=52.011 ms
64 bytes from 124.217.52.1: icmp_seq=10 ttl=253 time=54.467 ms

Anyway, when looking at the stats on her modem, the large # of TX Errors. What's the cause of a TX error?


Interface 		Tx pkt 		Tx err 		Tx drop
eth0 			278474 	        0 		0
8_35	 		167874 	        59355 	        0
1_39 			1 		0 		0


 
 						Downstream		Upstream
SNR Margin (dB)       				28.8		39.5
Attenuation (dB) 	        		   9.5		6.0
Output Power (dBm) 				-1.0		6.0
Attainable Rate (Kbps) 				22120		116
Rate (Kbps) 					128		64
K (number of bytes in DMT frame) 		3		2
R (number of check bytes in RS code word) 	14		0
S (RS code word size in DMT frame) 		0.50		0.88
D (interleaver depth) 				1		1
Delay (msec) 					0.12		0.22
FEC 						3		0
CRC 						2		2
Total ES 					2		3
Total SES 					0		0
Total UAS 					0		0

Again, that TX error is what worries me. My question though, is this the typical behavior when trying to send out too much traffic or is it indicitive of some other issue?

I know her B/W profile is a bit low on the upstream but it should be sufficient for ichat (40Kbps), Skype (24Kbps on the lowest codec) and when websurfing, there shouldn't be stalls on the downstream (I'm guessing upstream acks are getting delayed or dropped).

I've made the recommendation that she works with her ISP to upgrade her service. At my last communication she stated that the ISP wasn't letting her upgrade until she lived out her current contract.(I'll say that I'm amused that they don't want to take more money from her but, then again, I'm not surprised with the business practices.)

Anyway, any bit of help would be appreciated. Just want to make sure I'm not chasing a red herring here.

Thanks

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bbplumber @ 20th Jan 01:43PM:
Re: Digitel - High number of TX errors

Sashwa,

Was the info I provided sufficient?

Just trying to learn what a TX error is on a DSL line.

In the DSL spec, is there a mechanism where the receiving equipment tells the sender that it's sending garbage?

I would figure that if a modem knew it was going to transmit an error it probably wouldn't transmit it in the first place. In my past experience, I've seen queueing errors when a buffer was overflown, but in this case I see no TX drops, which is typically where such errors would be reflected.

Anyway, just looking for some DSL knowledge.

Thanks,

Chris
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sashwa @ 20th Jan 03:13PM:
Re: Digitel - High number of TX errors

I think so but I'm not sure. This is a slow forum so it may take a while before someone comes around with help.

I'll check around to see if there might be a better forum to help you out.

Do you have access to her computer or are you here in CA? What is her OS?
--
TH ~ NE ~ EPN ~ NC ~ TD
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bbplumber @ 21st Jan 11:42AM:
Re: Digitel - High number of TX errors

I use logmein to get into it. She's running OSX 10.5.6

I seriously doubt the issue is with her PC though. The extreme variability in that first hop is what concerns me most.

Her provider is running 1483. I forgot to check how big of a subnet they have her on though. No idea what they are using for the DSLAM.

Thanks
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sashwa @ 21st Jan 03:05PM:
Re: Digitel - High number of TX errors

I did some checking around for you and this is what I was told:

They need a tech to fix their DSL line. FEC errors are from interfernce local to them either from the lines missing insulation (bare wires) local AM Radio, Ham Radio, and similar transmitters.

»en.wikipedia.org/wiki/ADSL quote:

During initial training, the ADSL modem tests which of the available channels have an acceptable signal-to-noise ratio. The distance from the telephone exchange, noise on the copper wire, or interference from AM radio stations may introduce errors on some frequencies. By keeping the channels small, a high error rate on one frequency thus need not render the line unusable: the channel will not be used, merely resulting in reduced throughput on an otherwise functional ADSL connection.

This image shows common DSL interferers:

[att=1]

--
TH ~ NE ~ EPN ~ NC ~ TD

bbplumber @ 22nd Jan 09:51AM:
Re: Digitel - High number of TX errors

That's some good info. I didn't know DSL has several channels that it scans through to determine what's the best ones.

I'll check on where the filter is placed and where the modem is in relation to it as well as some of the other noise sources. I wouldn't be surprised if poor quality extensions are used on some of the other phones as well as if it's located close to florescent lighting.

Looking at this page, »gmckinney.blogspot.com/2008/05/a···ats.html it indicates that her levels are pretty good. I'm guessing it may be something that's intermittently causing issues.

thanks for the help, that gives me alot more to go on in troubleshooting this issue.
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demoniacs @ 30th Jan 11:55PM:
Re: Digitel - High number of TX errors

tx errors are packets not transmitted correctly but should be corrected by interleaving if their isp has that which i think they have since they dont have and dropped packets. or it could be that not enough bandwith for the application.
--
Study hard. Play harder. Girls hardest!
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anon @ 31st Jan 02:00AM:
Re: Digitel - High number of TX errors

Simple - the landline or copper line is bad - either too far than allowed, or dirty like too many splices, moisture inside the pair, etc. if in cavite, better send a complaint letter to Digitel cc: NTC Manila.

Good luck.
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