(PMOD) Re: PortMaster Modems Digest V99 #20

Benjamin Saunders (gmc454ci@borg.com)
Wed, 26 May 1999 11:44:47 -0400

Courier 56k V.Everything with latest firmware (july 98)
Dialing a PM4 with com os ver. 3.8.2c2 (using Quad T-1 cards)
Alternately dialing USR TC Netserver I modem 16+ (BRI) X2 only
What causes different trellis coding to be negotiated when connecting under
(nearly) identical line conditions to ther RAS units? I know that the
modems usually measure SNR and use that value to determine signal spacing
granularity, but when this modem connects to our PM4 it fails to negotiate
nonlinear encoding, which prevents the trellis grid from giving lower
amplitude data channels a wider freqency range. The courier will retrain
very often, and eventually disconnect with unable to retrain, although it
will connect to our alternate rack of servers, USR netservers, and can stay
online for days at a time, and also negotiates a 64s-4d nonlinear grid,
whereas on the PM4, it will negotiate a 16s-4d linear grid. Has anyone
else been having problems with customers couriers? Register S27=2 Enables
unencoded (non-trellis coded) modulation in V.32 mode, although my guess is
this will seriously impair connection speed. Register S 34 can be used to
disable most of these features, which I have yet to try. The modem will
identify one bit robbed imparment on calls to either server. I know that
the PM4 supports all of these modes, since my own 56k sportster based 3C886
modem will consistantly use a 64s-4d nonlinear trellis grid. I have
included the link diagnostics to both terminal servers at the end of this
letter. The user is operating under NT4 workstation sp4, so he can hear a
tone every time a retrain and/or nak occurs.

Thanks,

Benjamin Saunders
____________________________
Borg Internet Services
Technical Support Team
Phone: (315) 793-0036
Fax: (315) 793-0213
Email: support@borg.com
-------------->
Mon. thru Fri. 9am - 10pm
Sat. 10am - 3pm
____________________________

Register S34:

=1 Disable 8S-2D trellis encoding.
=2 Disable 16S-4D trellis encoding.
=4 Disable 32S-2D trellis encoding.
=8 Disable 64S-4D trellis encoding.
=16 Disable non-linear coding.
=32 Disable TX level deviation.
=64 Disable Pre-emphasis.
=128 Disable Pre-coding.

NetServer Stats
----------------------------------------
ATI6
-----
USRobotics Courier V.Everything Link Diagnostics...

Chars sent 168268 Chars Received 3086734
Chars lost 0
Octets sent 97545 Octets Received 2763729
Blocks sent 11680 Blocks Received 30584
Blocks resent 0

Retrains Requested 0 Retrains Granted 2
Line Reversals 0 Blers 19
Link Timeouts 0 Link Naks 0

Data Compression V42BIS 2048/32
Equalization Long
Fallback Enabled
Protocol LAPM SREJ 128/15
Speed 45333/26400
Last Call 00:34:46

----------------------------------------
ATI11
-----
USRobotics Courier V.Everything Link Diagnostics...

Modulation x2/V.34+
Carrier Freq ( Hz ) NONE/1920
Symbol Rate 8000/3200
Trellis Code NONE/64S-4D
Nonlinear Encoding NONE/ON
Precoding NONE/ON
Shaping OFF/ON
Preemphasis Index NONE/5
Recv/Xmit Level (-dBm) 28.2/17.1
SNR ( dB ) 41.4
Near Echo Loss ( dB ) 8.9
Far Echo Loss ( dB )
Roundtrip Delay (msec) 7
Timing Offset ( ppm) -1095
Carrier Offset ( ppm) 102
RX Upshifts 3
RX Downshifts 0
TX Speedshifts 0
x2 Status 0000; 0000-0000-0000-0001-0000-0000; 01,00 4039;00
----------------------------------------
ATY11
-----
Freq Level
150 25
300 24
450 23
600 24
750 24
900 24
1050 25
1200 25
1350 26
1500 26
1650 27
1800 28
1950 28
2100 29
2250 29
2400 30
2550 30
2700 30
2850 31
3000 32
3150 33
3300 35
3450 38
3600 43
3750 49

PortMaster 4
----------------------------------------
ATI6
-----
USRobotics Courier V.Everything Link Diagnostics...

Chars sent 42 Chars Received 360
Chars lost 0
Octets sent 42 Octets Received 272
Blocks sent 38 Blocks Received 24
Blocks resent 2

Retrains Requested 0 Retrains Granted 0
Line Reversals 0 Blers 22
Link Timeouts 0 Link Naks 1

Data Compression V42BIS 1024/32
Equalization Long
Fallback Enabled
Protocol LAPM 128/8
Speed 44000/26400
Last Call 00:00:53

Disconnect Reason is DTR dropped
----------------------------------------
ATI11
-----
USRobotics Courier V.Everything Link Diagnostics...

Modulation V.90/V.34+
Carrier Freq ( Hz ) NONE/1920
Symbol Rate 8000/3200
Trellis Code NONE/16S-4D
Nonlinear Encoding NONE/OFF
Precoding NONE/OFF
Shaping OFF/ON
Preemphasis Index NONE/5
Recv/Xmit Level (-dBm) 31.7/17.1
SNR ( dB ) 41.5
Near Echo Loss ( dB ) 8.9
Far Echo Loss ( dB )
Roundtrip Delay (msec) 22
Timing Offset ( ppm) -1059
Carrier Offset ( ppm) 94
RX Upshifts 0
RX Downshifts 0
TX Speedshifts 0
V.90 Status uu,5,12N,12.1,0,1N,0,42.1,28.3
----------------------------------------
ATY11
-----
Freq Level
150 28
300 26
450 26
600 26
750 27
900 27
1050 28
1200 28
1350 29
1500 29
1650 30
1800 30
1950 31
2100 31
2250 32
2400 32
2550 33
2700 33
2850 34
3000 34
3150 35
3300 35
3450 37
3600 40
3750 43
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