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Beginner

sh dsl int atm 0 - command interpretation

Trying to understand what this command is telling me and am I looking at the DS/US correctly?


DS - Downstream = DSL/ATM's Receiver's TX

US - Upstream = DSL/ATM's Receiver's RX

What's throwing me is there's output power and attenuation readings on both sides (DS and US).   I'd think that Output power readings would only be on the TX.  Attenuation is typically a "difference" between 2 variables.   Readings after - readings before = attenuation.   If this is the case, what is the Cisco using for before and after readings?   Are both the DS and US readings, read by the Cisco interface or are there readings from a remote end (as in FDL w/CSUs).

sh dsl int atm 0

                ATU-R (DS)                      ATU-C (US)
Modem Status:    Showtime (DMTDSL_SHOWTIME)
DSL Mode:        ITU G.992.1 (G.DMT)
ITU STD NUM:     0x01                            0x01
Vendor ID:       'ALCB'                          'ALCB'
Vendor Specific: 0x0000                          0x0000
Vendor Country:  0x00                            0x0F
Capacity Used:   20%                             86%
Noise Margin:    23.5 dB                          8.0 dB
Output Power:    20.0 dBm                        10.5 dBm
Attenuation:     17.5 dB                         12.0 dB
Defect Status:   None                            None
Last Fail Code:  None
Selftest Result: 0x00
Subfunction:     0x15
Interrupts:      723 (1 spurious)
Activations:     12
Init FW:         embedded
Operartion FW:   embedded
SW Version:      3.9.220
FW Version:      0x1A04

                 Interleave             Fast    Interleave              Fast
Speed (kbps):             0              864             0               160
Reed-Solomon EC:          0                0             0                 0
CRC Errors:               0                0             0                 0
Header Errors:            0                0             0                 0
Bit Errors:               0                0
BER Valid sec:            0                0
BER Invalid sec:          0                0

LOM Monitoring : Disabled

DMT Bits Per Bin
00: 0 0 0 0 0 0 0 2 2 2 0 0 0 0 0 0
10: 2 4 4 4 4 4 4 4 4 4 5 4 4 4 0 0
20: 0 0 0 0 0 0 0 0 0 0 0 0 2 2 2 2
30: 2 3 3 3 4 4 4 4 4 4 4 4 4 4 4 4
40: 4 4 4 4 4 2 4 3 3 2 2 2 2 2 2 2
50: 2 2 2 0 0 0 0 0 0 0 0 0 0 0 0 0
60: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
70: 0 0 0 0 0 0 2 2 2 2 2 2 2 2 2 2
80: 2 2 2 2 2 2 2 2 2 2 2 2 2 0 0 0
90: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
A0: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
B0: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 2
C0: 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
D0: 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
E0: 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
F0: 2 2 2 2 2 2 2 2 2 2 2 2 2 0 0 0

Training log buffer capability is not enabled yet.

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8 REPLIES 8
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Hall of Fame Master

Re: sh dsl int atm 0 - command interpretation

The attenuation values are per ADSL standard, nothing particular to Cisco. Not surprisingly, the "before" and "after" is referred to the copper pair and splices separating router from DSLAM:

And yes the remote measurement values are received over a maintenance communication channel, again part of ADLS standard.

Highlighted
Beginner

Re: sh dsl int atm 0 - command interpretation

Thanks.  So which is the "remote" measurement, the ATU-R (DS)? 

In regard to "attenutation", what is this a "difference" of?  Am I correct in that "attenutation" isn't the RX level?

                ATU-R (DS)                      ATU-C (US)
Noise Margin:    23.5 dB                          8.0 dB
Output Power:    20.0 dBm                        10.5 dBm
Attenuation:     17.5 dB                         12.0 dB

Highlighted
Hall of Fame Master

Re: sh dsl int atm 0 - command interpretation

http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci211613,00.html

Please remember to rate useful posts clicking on the stars below.

Highlighted
Beginner

Re: sh dsl int atm 0 - command interpretation

Sorry - I'm not seeing the answer for what I'm looking for.

1. Is the "remote" measurement, the ATU-R (DS)?

2. The link you sent has the formula:

     Ps is the signal power at the transmitting end (source) of a communications circuit and

     Pd is the signal power at the receiving end (destination), then Ps > Pd.

     The power attenuation Ap in decibels is given by the formula: Ap = 10 log10(Ps/Pd)

     What values below represent Ps and Pd?  I'd think that Ps would be the Output Power, but does Cisco give the RX power? 

                ATU-R (DS)                      ATU-C (US)
     Noise Margin:    23.5 dB                          8.0 dB
     Output Power:    20.0 dBm                        10.5 dBm
     Attenuation:     17.5 dB                         12.0 dB

Assuming my math is right, if I use Output power ast Ps, Pd would have to be .356 and .663 respectively solving for the Attenuation values which seems very low.

Highlighted
Hall of Fame Master

Re: sh dsl int atm 0 - command interpretation

1.  R = Remote. as you can see by downlink speed.

2. http://en.wikipedia.org/wiki/Decibel

For DS:

Ps = 20   dBm = 10 log(20  /10) = 100    mW

Pr =  2.5 dBm = 10 log( 2.5/10) =   1.77 mW


For US:

Ps = 10.5 dBm = 10 log(10.5/10) = 11.22 mW

Pr = -1.5 dBm = 10 log(-1.5/10) =   .70 mW


Please remember to rate useful posts clicking on the stars below.

Highlighted
Beginner

Re: sh dsl int atm 0 - command interpretation

Maybe I'm making this more complicated that it needs to be.   If I'm troubleshooting,

ATU-R (DS) is stats from the remote end (the DSLAM)?

ATU-C (US) is stats from the Cisco ATM interface?

Output power = TX power

Attenuation = High value means I have a low RX level, Low attenuation means I have a high RX level.

Highlighted
Hall of Fame Master

Re: sh dsl int atm 0 - command interpretation

ATU-R (DS) is stats from the remote end (the DSLAM)?

ATU-C (US) is stats from the Cisco ATM interface?

Yes as mentioned three times already.


Output power = TX power

Yes evidently

Attenuation = High value means I have a low RX level, Low attenuation means I have a high RX level.

Yes evidently.

Note the values you posted are absolutely normal. If you are not happy with the speeds you got, talk to your ISP or switch to another one.

I noticed you have not rated any useful post yet - I invite you to do so in appreciation of freely given contribution by Professional Network Engineers.

Highlighted
Hall of Fame Expert

Re: sh dsl int atm 0 - command interpretation

Hello Klwilson,

these are some common DSL terms you should be aware of:

ATU-R  = CPE terminal equipment modem at your  home

ATU-C = modem at Central office.

modern DSL uses DMT modulation.

To explain it in a few words:

there are 256 tones:  carriers each of them can be modulated in a different way.

the carriers are spaced in frequency using roughly 1 Mhz of bandwidth.

low frequencies are not used to allow for PSTN legacy analog voice signals.

There is then a safety ring of unused tons.

First N tones (as frequency increases) are used by ATU-R to transmit to central office.

This is the upstream user  to CO direction.

Again there is a safety band not used.

There is also a pilot tone used to perform negotiations and to exchange informations with other side.

M upper tones are used by CO to send data in the downstream direction

M > N and these tones usually can be modulated with more bits per tone.

the end result is that DS speed is usually greater then upstream streams.

Measures are performed by cooperation of the two modems on the pilot tones:

remote end can tell what the power level is for each tone over these maintanance channels.

By  knowing the power used by each tone the attenuation level per tone can be calculated.

if a noise margin cannot be guaranteed at a given tone less bits per tone has to be used.

There is a great computational complexity under the DMT: a DSL frame is mapped to the bits of  the tones used in that direction and then it is reassembled at remote end.

It is a complex frequency division multiplexing.

traffic in different directions travel modulated at different frequencies but using  multiple carriers modulated with only few bits each.

the sh dsl int atm x

presents a lot of information including the bits used per tone.

see also for an introduction to current DSL

http://www.broadband-forum.org/downloads/About_DSL.pdf

Hope to help

Giuseppe