bk_856er
join:2007-06-08
Palo Alto, CA
| [General] interpreting Zyxel diagnostic numbers
My Earthlink DSL + LPV (Covad) is giving me fits recently. Modem is in bridge mode with a Netgear FR114P router. High latency, stalls, poor throughput, etc. Power cycling the modem sometimes helps for a short while, but not always.
Can anyone help me make sense of the diagnostic numbers shown below?
I'd appreciate it!
Thanks.
Bob
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noise margin upstream: 10 db
output power downstream: 16 db
attenuation upstream: 38 db
noise margin downstream: 6 db
output power upstream: 11 db
attenuation downstream: 63 db
System Name:
ZyNOS F/W Version: V3.40(AHC.0) | 11/16/2005
DSL FW Version:TI AR7 05.00.03.e6
Standard:Multi-Mode
System up Time: 0:18:45
CPU Load: 0.24%
WAN Port Statistics:
Link Status: Up
Upstream Speed: 798 kbps
Downstream Speed: 2881 kbps
Node-LinkStatusTxPktsRxPktsErrorsTx B/sRx B/sUp Time
1-1483 Up 498 475 0 0 0 0:01:28
LAN Port Statistics:
Interface: Status TxPkts RxPkts Collisions
Ethernet 100M/Full Duplex 4240 3867 0 |
|
Doctor Olds
I Need A Remedy For What's Ailing Me.
Premium,VIP
join:2001-04-19
1970 442 W30
clubs:
| said by bk_856er  :noise margin upstream: 10 db output power downstream: 16 db attenuation upstream: 38 db noise margin downstream: 6 dboutput power upstream: 11 db attenuation downstream: 63 db
Upstream Speed: 798 kbps
Downstream Speed: 2881 kbps
Your line is not syncing at the correct level (I assume it is set for 3.0 or above) but it shows a Downstream Speed of 2881 kbps instead of the correct 3008 kbps value the port is set for with 3.0 Service. That means the line is running at above maximum capacity and leaves no room for any variations in the signal so it drops when the signal varies (which is normal for both as the signal will vary and when over capacity it will drop when the signal changes due to no spare room for variation).
Plus the 63 dB Downstream Attenuation is indication of either a very long line or possible inside wiring issues along with the too low value of 6 db on the Noise Margin Downstream that indicates similar problems with the either the line distance or inside wiring.
How do I check modem statistics/event logs? What do the numbers mean?
Although what is monitored and the exact name may be different depending on manufacturer, the overall information is pretty much the same. Below are some of the common terms and measurements used to judge line quality. Remember these are not hard numbers but simply a generalization of line statistics: SN Margin (AKA Signal to Noise Margin or Signal to Noise Ratio)Relative strength of the DSL signal to Noise ratio. 6dB is generally the lowest dB manufactures specify in order for the modem to be able to synch. In some instances interleaving can help raise the noise margin to an acceptable level. Generally speaking, as overall bandwidth increases, your signal to noise ratio decreases. So a customer that upgrades from 1.5 to 6.0 service will typically see a corresponding decrease in the signal to noise ratio. The higher the number the better for this measurement.  6dB or below is bad and will experience no synch or intermittent synch problems7dB-10dB is fair but does not leave much room for variances in conditions 11dB-20dB is good with no synch problems 20dB-28dB is excellent 29dB or above is outstanding Line AttenuationMeasure of how much the signal has degraded between the DSLAM and the modem. Maximum signal loss recommendation is usually about 60dB. One of the biggest factors affecting line attenuation is distance from the DSLAM. Generally speaking, bigger distances mean higher attenuation. The lower the dB the better for this measurement. 20dB and below is outstanding 20dB-30dB is excellent 30dB-40dB is very good 40dB-50dB is good 50dB-60dB is poor and may experience connectivity issues 60dB or above is bad and will experience connectivity issues
»EarthLink DSL FAQ »How do I test at my NID? What does it look like?
Regards,
Doctor Olds
--
What’s the point of owning a supercar if you can’t scare yourself stupid from time to time? |
|
bk_856er
join:2007-06-08
Palo Alto, CA
| Doctor Olds, that is enormously helpful. Thank you! I now have something to work with. I will investigate as suggested and report back on my findings.
On the apparent incorrect syncing issue, do I need to contact a technical person at earthlink to resolve that?
Bob |
|
Doctor Olds
I Need A Remedy For What's Ailing Me.
Premium,VIP
join:2001-04-19
1970 442 W30
clubs:
| said by bk_856er :On the apparent incorrect syncing issue, do I need to contact a technical person at earthlink to resolve that? Not until after you test at the NID and get some new outside figures to compare inside figures with. The incorrect sync is due to the line not currently being able to support 3.0 Sync so the DSL Modem connects as fast as it can which is the lower speed of 2881 kbps. So no you don't call EL yet. Test out at the NID instead.
If you do contact EL now (before testing at NID) they will see the incorrect lower sync based on your complaint and their only fix (since we do not know if you have wiring issues to clean up or not yet) is to just lower your sync rate speed to 1.5 Mbps in order to get the SNR value to increase above 6.0 dB so the line will become stable. For a line to be stable at 1.5 Mbps the SNR needs to be a minimum of 8 dB to 10 dB or higher. To have that same line stable at 3.0 Mbps the SNR needs to be a minimum of 10 dB to 12 dB or higher and for a 6.0 Mbps the SNR needs to be a minimum of 12 dB to 14 dB or higher.
Like I posted earlier:
You really need to test at the NID and post the stats as seen with the modem there.
Regards,
Doctor Olds
--
What’s the point of owning a supercar if you can’t scare yourself stupid from time to time? |
|
bk_856er
join:2007-06-08
Palo Alto, CA
| These are the new Zyxel diagnostic numbers with the modem connected at the NID. There is no improvement, so as I understand it the problem is not on my end. Is it normal for the Downstream Speed rate to go up, from 2882 to 3310?
What is the recommended course of action from here?
Thanks!!
Bob
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noise margin upstream: 10 db
output power downstream: 17 db
attenuation upstream: 38 db
noise margin downstream: 2 db
output power upstream: 11 db
attenuation downstream: 63 db
System up Time: 0:16:12
CPU Load: 0.25%
WAN Port Statistics:
Link Status: Up
Upstream Speed: 798 kbps
Downstream Speed: 3310 kbps
Node-Link Status TxPkts RxPkts Errors Tx B/s Rx B/s Up Time
1-PPPoE Up 552 548 0 0 0 0:06:55
LAN Port Statistics:
Interface: Status TxPkts RxPkts Collisions
Ethernet 100M/Full Duplex 1474 1667 0 |
|
Doctor Olds
I Need A Remedy For What's Ailing Me.
Premium,VIP
join:2001-04-19
1970 442 W30
clubs:
| They have your line running higher than 3.0 as the maximum sync is 3008 on a 3.0 Line. That will cause the problems you are seeing as too much signal is lost at your distance. When they turn the sync rate down the other numbers should improve (except Upstream/Downstream Attenuation which is based on distance).
Since the Downstream Attenuation did not change, that means you are on a very long line too far from the CO to get the Full Sync rate of the "up to" 8 Mbps plan. You might want to try asking the Techs in the Covad Direct Forum what they think the best rate your line can handle would be.
Regards,
Doctor Olds
--
What’s the point of owning a supercar if you can’t scare yourself stupid from time to time? |
|
bk_856er
join:2007-06-08
Palo Alto, CA | Thanks again.
I got my circuit number from the techs at the Covad Direct Forum and I have an inquiry in for their input.
According to the tools here my CO distance is 11,960ft to PLALCA12.
Bob |
|
Doctor Olds
I Need A Remedy For What's Ailing Me.
Premium,VIP
join:2001-04-19
1970 442 W30
clubs:
| Let us know what they end up suggesting as your line Attenuation on the Downstream is very high which usually points to distance as the issue. You may need to ask them to set you at 3008 Kbps and see if that is stable or not. It that is not stable, then they can try Safe Mode to stabilize your line.
»EarthLink DSL FAQ »What is Safe Mode?
Regards,
Doctor Olds
--
What’s the point of owning a supercar if you can’t scare yourself stupid from time to time? |
|
bk_856er
join:2007-06-08
Palo Alto, CA
| This is the reply from Covad:
"AT&T's estimated loop distance was 14,069ft which is too far for 6.0 service. You will have to call into tech support to have a loop test ran on your line for an accurate distance.
I lowered your speed to 3.0/384, check your margins inside the modem again to see if it is better.
After working with tech support and you find out that your loop length is longer than 10,000ft, a downgrade in service will be needed. If your loop is under 10k, you will probably need a technician to check your lines."
I ran the modem diagnostics again at the NID after the speeds were lowered and the results were unchanged for the problematic downstream numbers:
noise margin upstream: 25 db
output power downstream: 16 db
attenuation upstream: 38 db
noise margin downstream: 4 db
output power upstream: 11 db
attenuation downstream: 63 db
Upstream Speed: 383 kbps
Downstream Speed: 3002 kbps
I will try and get in touch with Earthlink (they are the correct party?) and try to have a loop test and line check performed. Anything else I should be doing?
This forum is really a terrific resource.
Thanks!
Bob |
|
Doctor Olds
I Need A Remedy For What's Ailing Me.
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join:2001-04-19
1970 442 W30
clubs:
1 edit | That explains the high Downstream Attenuation value of 63 dB and Yes, Earthlink has to be contacted and you have to get them to order the testing to be done to see if it is line length or other issue with the line like bridge taps.
I suggest trying the newest EL Tech ELNK_Stacey that works here in the Forums:
»EarthLink DSL FAQ » Who are the Official Earthlink Techs that Post Here?
Regards,
Doctor Olds
--
What’s the point of owning a supercar if you can’t scare yourself stupid from time to time? |
|
Bill_MI
Bill In Michigan
Premium,MVM
join:2001-01-03
Royal Oak, MI
 ·Comcast
1 edit | reply to bk_856er
Hi Bob,
I see the numbers but how well does it stay online at the reduced speed?
Doc, that'll probably be in ADSL2 mode, agree?
Old common sense says 4db noise margin will be problematic but the ZyXEL modems Earthlink's been supplying sounds like a sweet modem and may run well. Can you also confirm you have a ZyXEL P-660?
Thanks  |
|
bk_856er
join:2007-06-08
Palo Alto, CA
| Yes, I am using the ZyXel P-660R-ELNK modem that I received when I upgraded to the "DSL/phone" package about a year ago.
So far the behavior is no better with the recently reduced speeds (occasional loss of sync, partially loaded web pages, stalls, high latency, etc.).
The 4db noise margin is typical, but it fluctuates between -1db (yes, minus one) up to 4-6db.
Bob |
|
Doctor Olds
I Need A Remedy For What's Ailing Me.
Premium,VIP
join:2001-04-19
1970 442 W30
clubs:
| reply to Bill_MI
said by Bill_MI :Doc, that'll probably be in ADSL2 mode, agree? Yes it is ADSL2+ with the DSL And Home Phone bundle. 
--
What’s the point of owning a supercar if you can’t scare yourself stupid from time to time? |
|
Bill_MI
Bill In Michigan
Premium,MVM
join:2001-01-03
Royal Oak, MI
·Comcast
| reply to bk_856er
Thanks, Bob & Doc. Looks like the limit of ADSL2+ giving any benefit as it's behaving similar to ADSL.
Bob, those observations are of great interest as ADSL2+ builds forum members with a better feel for the numbers. I'm a numbers guy (and have a comparable line ). |
|
bk_856er
join:2007-06-08
Palo Alto, CA
| I'm glad that the info is useful. Unfortunatley I normally have the modem in bridge mode and I never thought to collect a set of benchmark diagnostic data when things were working well (for about a year I think). Out of the blue last week everything went haywire. The ZyXel stays connected, but throughput is essentially zero. Hopefully it can be restored with minimal pain. Phone service has not been impacted at all. I'll update as things progress...
Bob |
|
Bill_MI
Bill In Michigan
Premium,MVM
join:2001-01-03
Royal Oak, MI
·Comcast
| Bob, looking at your stats it's hard to believe it was working at much higher speed. However, there's always the possibility extra wiring was added out in the telco domain somewhere.
The extra data helps know what's going on - but does nothing to get it fixed. I can attest to that first hand. Storm damage caused me to loose a line with 9 db less attenuation a few years ago and I have a snowball's chance in hell of ever getting it back unless I bribe a phone tech or something.  |
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bk_856er
join:2007-06-08
Palo Alto, CA
| Yeah, knowledge is power, right?
I enlisted my young son to sniff out the house with his home made AM radio. It's amazing what gives off RF. Dimmers are a major source, as are fluorescent lights, transformer "bricks" and laser printers. Just for fun I relocated the modem + lines and unplugged all non-essential devices....no improvement.
It's now in the hands of ELNK_Stacey...
Bob |
|
bk_856er
join:2007-06-08
Palo Alto, CA
| It took me a couple of hours to get a few successful speed tests tonight, but these are the numbers:
»/testhistory/1463341/7eaa5
Downstream margin was about 4-6db...notice the very low throughput. The line is presently totally unreliable and unuseable. Marital tension is growing.
Uploads are consistently fine and unchanged even after Covad lowered the speed from 798 to 383 kbps.
BK |
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bk_856er
join:2007-06-08
Palo Alto, CA | New tidbit from the helpful folks at the Covad Direct forum...
"The service brand is: LPVA-IP TeleSurfer BIA 1.5/384"
Bob |
|
bk_856er
join:2007-06-08
Palo Alto, CA
| This just in!
While I was typing the last message an IM came in from the tech at the Covad Direct forum and my modem-indicated speeds decreased to match my service brand.
Voila! My connection is stable again and speed tests show that I'm back on track.
See here: »/testhistory/1463341/7eaa5
Proof positive that too high a setting on a long line is bad juju. Just like the good doctor explained.
I'll update as needed....
noise margin upstream: 24 db
output power downstream: 16 db
attenuation upstream: 38 db
noise margin downstream: 14 db
output power upstream: 11 db
attenuation downstream: 62 db
Upstream Speed: 383 kbps
Downstream Speed: 1532 kbps |
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