When studying for my Cisco ISCW exam, I wanted to get somewhat more in-depth information on the different DSL-techniques.

First of all, there are different DSL techniques, ranging from IDSL (providing 144/144kbps) over the popular ADSL (somewhere around 1/10Mbps up/down) up to the newer VDSL variants (around 50Mbps). Within each technique, there are different modulation schemes.

I decided to explore what my Alcatel SpeedTouch modem (now Thomson) had to tell me; here is the report.

My Alcatel Speedtouch is manageble via regular telnet. Just pressing enter at the “User :” prompt gets you into the console. The things you can do and see are rather limited, until you go into some kind of “debug” mode:

=>td prompt

========================DISCLAIMER=========================
 Access to expert mode is intended for qualified personnel
 only. Press ENTER to return to user mode.
=====================END=OF=DISCLAIMER=====================

'SpeedTouch (00-90-D0-xx-xx-xx)'
Password : **********

Switched to 'Trace & Debug' prompt.

Return to Normal mode by typing 

>

The password is the decimal representation of the CRC value of the ‘SpeedTouch (00-90-D0-xx-xx-xx)’ string (excluding the quotes). The CRC is of order 32, uses polynomial 0x5C22DB93, direct, non-reversed bytes and has both an initial and a final XOR with 0xFFFFFFFF. This page has a generic CRC calculator in JavaScript you can use to get your password, or you can use the Digest::CRC perl module like this.

Once in the debug mode, a lot more commands are available:

>help

Following topics are available :

dbg         err         xapi        guard       rip
ni          etha        atm         atm         eth
llc         atmf        iwu         sock        ipoa
ipoa        tcp         pptp        config      system
softwa      phoneb      adsl        nat         cip
ppp         bridge      dns         dhcp        dhcpc
tftp        sachem      eoc         aoc         hs
mlit        msit        golden      tdsl

>

By just looking around, I found the following useful information:

>sachem
sachem>get_opmode
Lite mode is not set
DMT mode is set
sachem>

Which indicates that the used modulation is G.922.1

Since the modem only sees one end of the line, it can only tell about half of the line parameters; unless you activate “golden mode”:

>tdsl
tdsl>help

Following commands are available for ADSL ANT :
lineState
leds
ripData
customConfig
staticConfig
powerConfig
vendor
shutdownCond

Test facilities:
activate
deactivate
restAccept
restart
tuneUSPowerCutBack <0-64>
setOperMode <multi/lite/ansi>
allowedOperMode
setPermissions <alcatel/compliancy>
permissions

golden <on/off>

potsTest <seconds>
tdsl>golden on
tdsl>

This will cause the DSL-line to re-sync, but will show the parameters from the DSLAM-end as well:

>golden
golden>help
Golden debug commands
---------------------
{} mandatory, [] optional parameters.
modem_variant                      : Get the modem golden start state.
modem_state                        : Get the modem state.
configuration                      : Get the configuration data.
identification                     : Get the identification data.
common_settings                    : Get the common settings data.
operational_data [init]            : Get the operational data.
channel_data                       : Get the channel data.
operational_channel [init]         : Get the operational channel data.
carrier_data [init]                : Get the carrier data.
initialization_error               : Get the initialization error.
start_traffic                      : Start traffic measurement.
stop_traffic                       : Stop traffic measurement.
endian_stream                      : Toggle endian mode of the golden streaming mode.
golden>modem_variant

The modem is POTS G.DMT.

Receive  channel first carrier = 38
Receive  channel last  carrier = 255
Tramsmit channel first carrier = 7
Transmit channel last  carrier = 29

golden>modem_state

The modem is in SHOWTIME_L0.
golden>configuration

Configuration report
--------------------

ATUC
====
Minimum noise margin downstream                : 0
Minimum noise margin upstream                  : 0
Max. additional noise margin downstream        : 31
Max. additional noise margin upstream          : 31
Target noise margin downstream                 : 6
Target noise margin upstream                   : 6
Max. PSD downstream                            : -40
Rate adaptivity mode downstream                : 2
Rate adaptivity mode upstream                  : 2
Interleaf min bit rate downstream              : 0
Interleaf min bit rate upstream                : 0
Interleaf planned bit rate downstream          : 0
Interleaf planned bit rate upstream            : 0
Interleaf max bit rate downstream              : 0
Interleaf max bit rate upstream                : 0
Interleaf max delay downstream                 : 16
Interleaf max delay upstream                   : 16
Fast min bit rate downstream                   : 288
Fast min bit rate upstream                     : 96
Fast planned bit rate downstream               : 4640
Fast planned bit rate upstream                 : 512
Fast max bit rate downstream                   : 4640
Fast max bit rate upstream                     : 512

Carrier Mask (x=masked, o is not masked)

Carrier   0 :  o  o  o  o  o  o  o  o  o  o
Carrier  10 :  o  o  o  o  o  o  o  o  o  o
Carrier  20 :  o  o  o  o  o  o  o  o  o  o
Carrier  30 :  o  o  o  o  o  o  o  o  o  o
Carrier  40 :  o  o  o  o  o  o  o  o  o  o
Carrier  50 :  o  o  o  o  o  o  o  o  o  o
Carrier  60 :  o  o  o  o  o  o  o  o  o  o
Carrier  70 :  o  o  o  o  o  o  o  o  o  o
Carrier  80 :  o  o  o  o  o  o  o  o  o  o
Carrier  90 :  o  o  o  o  o  o  o  o  o  o
Carrier 100 :  o  o  o  o  o  o  o  o  o  o
Carrier 110 :  o  o  o  o  o  o  o  o  o  o
Carrier 120 :  o  o  o  o  o  o  o  o  o  o
Carrier 130 :  o  o  o  o  o  o  o  o  o  o
Carrier 140 :  o  o  o  o  o  o  o  o  o  o
Carrier 150 :  o  o  o  o  o  o  o  o  o  o
Carrier 160 :  o  o  o  o  o  o  o  o  o  o
Carrier 170 :  o  o  o  o  o  o  o  o  o  o
Carrier 180 :  o  o  o  o  o  o  o  o  o  o
Carrier 190 :  o  o  o  o  o  o  o  o  o  o
Carrier 200 :  o  o  o  o  o  o  o  o  o  o
Carrier 210 :  o  o  o  o  o  o  o  o  o  o
Carrier 220 :  o  o  o  o  o  o  o  o  o  o
Carrier 230 :  o  o  o  o  o  o  o  o  o  o
Carrier 240 :  o  o  o  o  o  o  o  o  o  o
Carrier 250 :  o  o  o  o  o  o

Near end M3 configurationData
=============================
US power cutback                               : 0

Near end POTS overlay Operation modes          : 11
Near end POTS overlay permissions 0            : 12353
Near end POTS overlay permissions 1            : 12359
Near end POTS overlay permissions 2            : 12288
Near end POTS overlay permissions 3            : 12377
Near end POTS overlay permissions 4            : 4096
Near end POTS overlay permissions 5            : 4096
Near end POTS overlay permissions 6            : 4096
Near end POTS overlay permissions 7            : 4096

Near end ISDN overlay Operation modes          : 0
Near end ISDN overlay permissions 0            : 0
Near end ISDN overlay permissions 1            : 0
Near end ISDN overlay permissions 2            : 0
Near end ISDN overlay permissions 3            : 0
Near end ISDN overlay permissions 4            : 0
Near end ISDN overlay permissions 5            : 0
Near end ISDN overlay permissions 6            : 0
Near end ISDN overlay permissions 7            : 0

golden>identification

only available in ANSI-mode, use M3Identification !

Identification report : near end
----------------------------------
VendorId                           : 0xffffffff
VersionNumber                      : 0xffffffff

Identification report : far end
---------------------------------
VendorId                           : 0xffffffff
VersionNumber                      : 0xffffffff

golden>common_settings
Common settings report : near end
---------------------------------
Trellis coding                               : active
Echo cancelling                              : not active
Framing mode                                 : Minimum Overhead Framing
Maximum number supported Tx bits per carrier : 13

Common settings report : far end
---------------------------------
Trellis coding                               : active
Echo cancelling                              : not active
Framing mode                                 : Minimum Overhead Framing
Maximum number supported Tx bits per carrier : 14

golden>operational_data

Operational data report : near end (Downstream)
-----------------------------------------------
Attainable line rate      :  6684 kbit/sec
Attainable Atm rate       :  6208 kbit/sec
Used line rate            :  5112 kbit/sec
Fast used Atm rate        :  4640 kbit/sec
Interleaved used Atm rate :     0 kbits/sec
Rel. capacity occupation  :    76
Noise Margin              :     8 dB
Line attenuation          :    39 dB
Output Power              :    19 dBm

Operational data report : far end (Upstream)
--------------------------------------------
Attainable line rate      :  1112 kbit/sec
Attainable Atm rate       :   992 kbit/sec
Used line rate            :   608 kbit/sec
Fast used Atm rate        :   512 kbit/sec
Interleaved used Atm rate :     0 kbits/sec
Rel. capacity occupation  :    55
Noise Margin              :    21 dB
Line attenuation          :    17 dB
Output Power              :    12 dBm

golden>channel_data

Channel report : near end (Downstream)
--------------------------------------
1) SNR (dB)
Carrier  38 : 44.4 43.5
Carrier  40 : 42.9 43.4 42.9 43.1 43.4 42.5 42.9 42.3 42.9 43.4
Carrier  50 : 43.4 43.1 43.6 43.3 43.2 43.3 42.7 43.4 43.5 43.6
Carrier  60 : 43.8 43.2 43.3 42.7 43.3 41.4 42.1 41.4 42.1 41.9
Carrier  70 : 42.1 41.6 41.1 40.9 41.3 40.8 40.8 40.4 40.7 39.9
Carrier  80 : 40.2 39.6 40.3 40.1 39.6 39.2 39.5 39.1 39.6 39.2
Carrier  90 : 39.2 39.6 39.4 38.6 38.8 38.1 39.4 38.7 38.4 38.8
Carrier 100 : 38.2 38.1 38.8 38.8 38.1 37.4 38.3 37.4 38.2 38.1
Carrier 110 : 37.9 37.3 37.8 37.6 37.9 38.1 37.9 38.0 37.9 37.2
Carrier 120 : 37.5 37.9 37.7 37.8 37.7 37.4 37.6 37.8 37.5 37.0
Carrier 130 : 37.6 37.5 37.1 36.9 37.0 37.4 36.9 36.9 36.6 36.1
Carrier 140 : 36.1 36.8 36.3 36.0 30.1 36.3 35.9 35.8 35.6 35.6
Carrier 150 : 32.9 35.3 35.9 35.6 35.1 35.9 35.9 35.4 34.9 34.8
Carrier 160 : 34.3 34.4 34.5 34.5 34.8 34.3 34.0 34.1 33.9 33.9
Carrier 170 : 34.1 33.8 33.4 33.4 33.7 33.3 33.5 33.1 32.9 33.1
Carrier 180 : 32.9 32.9 32.6 32.4 32.9 32.8 31.9 32.1 32.3 32.1
Carrier 190 : 31.6 31.6 31.4 31.3 30.6 30.8 31.1 30.9 31.2 30.6
Carrier 200 : 31.0 30.6 31.1 30.2 30.1 30.3 30.3 30.1 29.3 29.3
Carrier 210 : 29.3 29.1 28.2 27.9 22.9 1.3 23.6 27.9 27.9 28.0
Carrier 220 : 27.8 28.3 28.4 27.7 27.8 27.3 26.8 26.6 27.1 26.6
Carrier 230 : 26.6 26.6 26.4 26.2 26.0 26.2 25.2 24.8 25.0 24.4
Carrier 240 : 24.4 23.8 23.4 23.1 22.2 22.0 21.8 20.8 20.4 19.2
Carrier 250 : 17.7 16.8 16.1 14.2 13.0 11.6

2) Line Attenuation (db)
Carrier  38 : 32.4 32.0
Carrier  40 : 31.8 31.7 31.7 31.7 31.7 31.7 31.8 32.0 32.4 32.7
Carrier  50 : 32.9 33.2 33.4 33.7 34.0 34.3 34.7 34.8 35.0 35.2
Carrier  60 : 35.4 35.7 35.9 36.2 36.4 36.4 36.7 36.8 37.0 37.2
Carrier  70 : 37.3 37.5 37.7 37.8 38.0 38.2 38.4 38.7 38.7 38.9
Carrier  80 : 39.2 39.4 39.4 39.5 39.8 40.0 40.2 40.3 40.5 40.7
Carrier  90 : 40.8 41.0 41.2 41.4 41.7 41.9 41.9 42.2 42.4 42.6
Carrier 100 : 42.9 43.0 43.2 43.3 43.5 43.9 44.1 44.3 44.5 44.7
Carrier 110 : 45.0 45.2 45.5 45.6 45.7 46.0 46.2 46.3 46.7 46.9
Carrier 120 : 47.1 47.3 47.5 47.7 48.0 48.2 48.5 48.6 48.9 49.0
Carrier 130 : 49.2 49.3 49.7 49.9 50.1 50.3 50.5 50.7 51.0 51.2
Carrier 140 : 51.5 51.6 51.7 52.0 52.2 52.3 52.7 52.9 53.1 53.3
Carrier 150 : 53.5 53.7 54.0 54.2 54.5 54.5 54.7 54.9 55.2 55.3
Carrier 160 : 55.5 55.7 56.1 56.1 56.3 56.5 56.7 57.0 57.2 57.5
Carrier 170 : 57.6 57.7 57.9 58.2 58.3 58.5 58.7 59.1 59.3 59.5
Carrier 180 : 59.7 60.0 60.2 60.5 60.5 60.8 61.0 61.3 61.4 61.6
Carrier 190 : 61.8 62.0 62.2 62.3 62.5 62.8 63.0 63.3 63.3 63.5
Carrier 200 : 63.7 63.8 64.0 64.3 64.4 64.6 64.8 65.2 65.3 65.5
Carrier 210 : 65.5 65.8 66.3 66.3 66.5 66.5 66.8 67.1 67.3 67.4
Carrier 220 : 67.8 67.8 68.0 68.2 68.3 68.5 68.8 69.0 69.3 69.5
Carrier 230 : 69.5 69.8 70.0 70.4 70.6 70.6 71.2 71.5 71.8 72.5
Carrier 240 : 72.5 73.3 73.8 74.3 75.0 75.5 75.8 77.0 77.5 78.7
Carrier 250 : 79.8 80.4 81.1 82.2 82.8 83.6

Channel report : far end (Upstream)
-----------------------------------
1) SNR (dB)
Carrier   7 : 50.7 54.5 55.3
Carrier  10 : 54.5 53.6 52.9 52.8 52.8 52.5 52.0 52.1 51.7 51.2
Carrier  20 : 50.1 50.0 49.6 49.4 48.7 47.8 47.4 47.1 46.3 44.7
2) Line Attenuation (db)
Carrier   7 : 17.3 11.5 8.8
Carrier  10 : 8.2 8.6 9.3 10.0 10.6 11.2 11.8 12.4 12.9 13.6
Carrier  20 : 14.2 15.0 15.8 16.7 17.6 18.6 19.6 20.9 22.4 24.9
golden>carrier_data

Carrier report :  near end (Downstream)
---------------------------------------
1) Allocated bits
Carrier  38 :  2   2
Carrier  40 :  4   4   5   6   6   6   7   7   7   8
Carrier  50 :  8   8   8   8   8   9   9   9   9   9
Carrier  60 :  9   9   2   9   8   8   8   8   8   8
Carrier  70 :  8   8   8   8   8   8   8   8   8   8
Carrier  80 :  8   8   8   8   8   8   8   8   8   8
Carrier  90 :  8   8   7   7   7   7   7   7   7   7
Carrier 100 :  7   7   7   7   7   7   7   7   7   7
Carrier 110 :  7   7   7   7   7   7   7   7   7   7
Carrier 120 :  7   7   7   7   7   7   7   7   7   7
Carrier 130 :  7   7   7   7   7   7   7   7   7   7
Carrier 140 :  7   7   7   7   4   7   7   7   6   6
Carrier 150 :  5   6   6   6   6   6   6   6   6   6
Carrier 160 :  6   6   6   6   6   6   6   6   6   6
Carrier 170 :  6   6   6   6   6   6   6   6   6   6
Carrier 180 :  6   6   6   6   6   5   5   5   5   5
Carrier 190 :  5   5   5   5   5   5   5   5   5   5
Carrier 200 :  5   5   5   5   5   5   5   5   5   5
Carrier 210 :  5   4   4   4   3   0   4   4   4   4
Carrier 220 :  4   4   4   4   4   4   4   4   4   4
Carrier 230 :  4   4   4   4   4   4   4   3   4   4
Carrier 240 :  3   3   3   3   2   2   2   2   2   2
Carrier 250 :  2   0   0   0   0   0

2) Noise margin (dB)
Carrier  38 : 12.1  11.4
Carrier  40 : 12.3  12.4  11.6  12.4  11.7  11.8  11.7  12.5  12.3  12.4
Carrier  50 : 12.0  12.6  12.2  11.8  12.1  12.4  12.6  11.7  12.3  12.4
Carrier  60 : 12.3  12.3  34.3  12.2  12.0  12.3  12.1  12.2  12.8  12.1
Carrier  70 : 11.9  12.7  12.4  12.2  12.2  12.1  12.0  12.8  12.5  12.5
Carrier  80 : 12.3  12.1  12.1  11.9  11.9  12.6  12.8  12.7  12.7  12.6
Carrier  90 : 12.5  12.6  12.5  12.2  12.1  12.2  12.0  12.6  12.1  11.9
Carrier 100 : 11.8  11.8  11.9  12.4  12.2  12.1  12.0  12.0  11.9  12.4
Carrier 110 : 12.3  12.1  12.3  12.3  12.4  12.4  12.4  12.1  12.4  12.5
Carrier 120 : 12.4  12.2  12.2  12.3  12.1  11.9  11.8  11.6  12.1  12.7
Carrier 130 : 11.9  12.1  11.9  11.6  11.9  12.0  11.8  12.7  12.1  12.1
Carrier 140 : 12.4  12.3  12.4  12.4  11.8  11.8  11.8  11.6  12.4  11.9
Carrier 150 : 11.6  12.4  11.8  12.2  12.1  11.9  11.9  11.7  12.3  12.4
Carrier 160 : 12.3  12.8  12.3  12.3  12.1  11.9  12.5  12.3  12.1  12.4
Carrier 170 : 12.4  12.2  11.7  12.7  11.9  11.6  12.8  12.9  12.8  12.0
Carrier 180 : 11.8  11.7  12.6  12.5  12.4  12.2  12.1  12.0  12.9  12.4
Carrier 190 : 12.3  12.2  11.9  12.5  12.3  12.4  11.6  11.9  12.1  12.0
Carrier 200 : 11.6  11.8  11.6  12.4  12.4  12.3  12.2  12.1  12.1  11.6
Carrier 210 : 12.3  12.3  11.6  11.3  8.3  0.0  7.6  11.3  12.0  11.4
Carrier 220 : 12.6  12.4  12.3  12.4  12.2  12.2  11.9  11.9  12.5  12.4
Carrier 230 : 11.9  11.8  11.6  12.3  12.1  11.7  11.6  12.8  12.3  12.2
Carrier 240 : 11.5  12.3  12.0  12.5  13.4  12.7  12.3  11.7  11.9  11.5
Carrier 250 : 11.6  15.7  13.8  11.5  0.0  0.0

3) Gains
Carrier  38 : 1.1  0.7
Carrier  40 : 1.3  0.9  0.9  1.2  0.9  0.8  1.1  1.1  0.9  1.2
Carrier  50 : 1.1  1.1  0.9  0.8  0.8  1.2  1.2  1.1  1.1  1.1
Carrier  60 : 1.1  1.1  0.9  1.1  0.9  0.9  0.8  0.8  0.9  0.8
Carrier  70 : 0.8  0.9  0.9  0.9  0.9  0.9  0.9  1.1  1.1  1.1
Carrier  80 : 1.1  1.1  1.1  1.1  1.1  1.2  1.2  1.2  1.2  1.2
Carrier  90 : 1.2  1.2  0.8  0.8  0.8  0.8  0.8  0.8  0.8  0.8
Carrier 100 : 0.8  0.8  0.8  0.9  0.9  0.9  0.9  0.9  0.9  0.9
Carrier 110 : 0.9  0.9  0.9  0.9  0.9  0.9  0.9  0.9  0.9  0.9
Carrier 120 : 0.9  0.9  0.9  0.9  0.9  0.9  0.9  0.9  0.9  1.1
Carrier 130 : 0.9  0.9  0.9  0.9  0.9  0.9  0.9  1.1  1.1  1.1
Carrier 140 : 1.2  1.1  1.1  1.2  1.2  1.1  1.1  1.1  0.8  0.8
Carrier 150 : 0.8  0.9  0.8  0.8  0.8  0.8  0.8  0.8  0.9  0.9
Carrier 160 : 0.9  0.9  0.9  0.9  0.9  0.9  1.1  1.1  1.1  1.1
Carrier 170 : 1.1  1.1  1.1  1.2  1.1  1.1  1.2  1.2  1.2  1.1
Carrier 180 : 1.1  1.1  1.2  1.2  1.2  0.8  0.8  0.8  0.9  0.9
Carrier 190 : 0.9  0.9  0.9  1.1  1.1  1.1  0.9  0.9  0.9  0.9
Carrier 200 : 0.9  0.9  0.9  1.1  1.1  1.1  1.1  1.1  1.1  1.1
Carrier 210 : 1.2  0.8  0.8  0.9  1.1  0.0  1.2  0.9  0.9  0.8
Carrier 220 : 0.9  0.9  0.9  0.9  0.9  0.9  0.9  0.9  1.1  1.1
Carrier 230 : 1.1  1.1  1.1  1.2  1.2  1.2  1.2  1.1  1.3  1.3
Carrier 240 : 0.9  1.1  1.1  1.2  0.7  0.7  0.7  0.7  0.8  0.9
Carrier 250 : 1.2  0.9  0.9  0.9  0.0  0.0

Carrier report : far end (Upstream)
------------------------------------
1) Allocated bits
Carrier   7 :  5   6   6
Carrier  10 :  7   7   7   8   8   8   8   8   8   7
Carrier  20 :  7   7   7   6   6   6   6   5   5   4
2) Noise margin (dB)
Carrier   7 : 23.5  20.9  22.3
Carrier  10 : 23.4  23.2  23.4  22.0  22.1  21.3  21.3  21.2  22.0  23.1
Carrier  20 : 22.6  23.0  22.1  22.5  23.6  22.4  21.5  22.6  23.1  22.8
3) Gains
Carrier   7 : 1.2  0.9  0.9
Carrier  10 : 1.1  0.9  0.9  1.1  1.1  0.9  0.9  0.9  1.1  0.9
Carrier  20 : 0.9  1.1  1.1  0.8  1.1  1.1  1.1  0.9  1.1  0.8
golden>initialization_error

No error occured !
golden>

Here are some graphical representations of the above data. This simple perl script is used to convert the “Carrier xxx : xx xx xx” lines into a format usable by gnuplot; this gnuplot-script turns that data into the graphs.

These graphs clearly show the behavior of a DMT modem: it allocates much bits (up to 9 per carrier) on carriers with a good SNR; carriers with bad SNR values get a lot less bits allocated to them.

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