Настройка модема на хорошей линии.

[Peter Stoliarov]

Добрый день!
Недавно провели новую линию, и хотелось бы получить рекомендации по настройке модема для оптимальной работы в этих условиях.
Например, несколько смущает большое количество forced fallbacks. СтОит ли с ними бороться и, если да, то как (в смысле, запрещать их вообще или зажимать скорость)?
В "дополнительных параметрах связи" у меня S17=48

Статистика прилагается:
Time Online.................. 00:19:51
Termination Reason........... LOCAL REQUEST
Tx Rate (Last/Init/Min/Max).. 31200/28800/28800/31200 bps
Rx Rate (Last/Init/Min/Max).. 54667/53333/52000/54667 bps
Modulation................... V.90
Protocol/Compression......... LAP-M/V.42bis
Line Quality................. 26
Tx/Power Drop/Rx Level....... 15/2/13
SNR Last/Min/Max............. 43/43/43
Highest Rx/Tx State.......... 67/87
EQM Sum...................... 0069
RBS Pattern.................. 00
Rate Drop.................... 2
Digital Loss................. 235F
Retrains Issued/Granted/Auto. 0/0/0
Renegs Issued/Granted........ 11/0
FForwards/FBacks/FEQM/Denied. 4/7/0/0
Forced FB/FB after FF/MaxREJ. 7/2/10
Last dialed number........... T785-4379
V90 9481834246E0

Rockwell Diagnostics/W32, version 1.2.0.1, compiled at Mar 13 2002 17:38:01
(c) 2000 Stanislav V. Mekhanoshin (rampitec@tu.spb.ru, 2:5030/172.9@fidonet)
----------------------------------------------------------------------------
Connection time : 00:19:51
Handshake Time/Retries : 23 sec/0
TX Rate (Last/Init/Min/Max) : 31200/28800/28800/31200
RX Rate (Last/Init/Min/Max) : 54667/53333/52000/54667
Modulation/Protocol/Compression : V.90/LAPM/V.42bis
TX Symbol rate : 3200
Signal Level (TX/Power Drop), -dB : 15/2
RX Signal Level (Last/Min/Max), -dB : 12/12/12
Band Edge Lower/Upper, Hz : 150/3825
Round trip delay, ms : 11.000
EQM Value (Last/Min/Max/Negative) : 26/17/61/0
EQM Samples Running Sum : 0069
EQM Last 10 Readings : 25 26 25 24 28 26 26 26 25 28
SNR Ratio (Last/Min/Max), dB : 46/46/46
TX Non-linear Encoding : OFF
TX Precoding : OFF
TX/RX Constellation Shaping : OFF/OFF
TX Trellis Encoding : 16 state
TX Pre-emphasis : 0
TX/RX state (Max TX/RX, Last TX/RX) : 87H/67H, 87H/65H
Error Correction Status : SABME:T UA:R XID:T,R SYNC
Dual PCM/120 Hz detection : No/No
Energy at 3750Hz/Average Energy : 5299/3552
RBS Pattern/Alternating RBS Pattern : 00/00
V.90 Digital Pad/A-law/HighPowerSrv : 1dB/Yes/No
Retrains (Issued/Granted/Fast) : 0/0/6
Renegs (Issued/Granted) : 5/0
Retrans per frame/Frames rejected : 1/3
Total number of REJ sent/received : 255 or more/14
Last Retrain/Reneg reason : Fall-back due to high EQM
Last Retrain/Reneg requested : Local Fast Retrain
Minutes Since Last Retrain/Reneg : 4
Disconnect reason : LOCAL REQUEST
Remote Manufacturer/Licensee Code : Conexant/Conexant
Remote Manufacturer's Product Caps : K56Flex, V.90
Remote V.8bis caps (type) : Digital (Server)
Remote V.8bis caps (K56Flex mode) : K56Flex prototype mode not supported
Remote V.8bis caps (K56Flex version): 1.1
Remote K56Flex RAM version supported: 70
Remote Coding used/forced by server : A-law/Yes
Remote controller version number : 0
Remote supports symbol rate (1,2,5) : 2743:ON 2800:ON 3429:ON 3429-TX:ON
Remote supports symbol rate (3,4) : 3000-L:ON 3000-H:ON 3200-L:ON 3200-H:ON
Remote power drop support : ON
Remote max symbol rate difference : 0 steps
Remote is a CME modem : No
Remote supports V.34bis : Yes
Remote frequency source : Internal
Remote is ITU/K56Flex neg/High IMD : Yes/Yes/No
V.8 bis CRe detected/early : Yes/No
CRe/CRd/CL/MS/ACK/NAK received : Yes/No/Yes/No/Yes/No
V.8bis success/V.8bis neg started : Yes/Yes

Unimodem Diagnostics/W32, version 1.1.0.0, compiled at Mar 14 2002 18:01:05
(c) 2000 Stanislav V. Mekhanoshin (rampitec@tu.spb.ru, 2:5030/172.9@fidonet)
----------------------------------------------------------------------------
Multi-media mode : Data Only
DTE-DCE interface mode : Async data
TX/RX signal power level, -dBm : 17/13
Estimated noise level, -dBm : 56
TX/RX Negotiation : V.34/V.90 Issue 1 (asymmetric)
TX/RX Symbol Rate : 3200/8000
TX/RX Carrier frequency, Hz : 1829/0
TX data rate (Last/Init) : 31200/28800
RX data rate (Last/Init) : 54666/53333
Temporary carrier loss count : 0
Carrier Rate Re-neg count : 11
Retrains Requested/Granted : 0/0
Protocol/Compression : V.42 LAPM/V.42bis
Error control frame size, bytes: 128
Error control timeouts in TX : 8
Error control NAKs received : 14
Compression dict. size, bytes : 2048
TX/RX flow control : V.24 ckt 106/133 / V.24 ckt 106/133
TX/RX chars sent : 588942/2464382
TX/RX chars lost (data overrun): 0/0
TX/RX I-Frame count : 6866/22907
TX/RX I-Frame error count : 14/259
Termination Cause : cct108 turned Off

[Technical Support]

Большое количество forced fallbacks - следствие, с которым бороться не нужно. Причина же - в слабой загрузке модема на приём ("простоях"), во время которых он "заползал" вверх, выше оптимальной скорости. С этим нужно бороться путём установки S202.3=1.

Попробуйте такую строку инициализации:

S91=18 S210.7=1 S202.3=1 S55.4=1 S17=48
_________________
Inpro
Technical Support

[Peter Stoliarov]

Вот результат:

Time Online.................. 00:07:25
Termination Reason........... LOCAL REQUEST
Tx Rate (Last/Init/Min/Max).. 28800/28800/28800/28800 bps
Rx Rate (Last/Init/Min/Max).. 53333/50667/50667/56000 bps
Modulation................... V.90
Protocol/Compression......... LAP-M/V.42bis
Line Quality................. 22
Tx/Power Drop/Rx Level....... 18/0/13
SNR Last/Min/Max............. 43/43/43
Highest Rx/Tx State.......... 67/87
EQM Sum...................... 0076
RBS Pattern.................. 00
Rate Drop.................... 2
Digital Loss................. 235F
Retrains Issued/Granted/Auto. 0/0/0
Renegs Issued/Granted........ 7/0
FForwards/FBacks/FEQM/Denied. 3/4/0/0
Forced FB/FB after FF/MaxREJ. 3/1/8
Last dialed number........... T785-4379
V90 9481834246E0

Rockwell Diagnostics/W32, version 1.2.0.1, compiled at Mar 13 2002 17:38:01
(c) 2000 Stanislav V. Mekhanoshin (rampitec@tu.spb.ru, 2:5030/172.9@fidonet)
----------------------------------------------------------------------------
Connection time : 00:07:25
Handshake Time/Retries : 23 sec/0
TX Rate (Last/Init/Min/Max) : 28800/28800/28800/28800
RX Rate (Last/Init/Min/Max) : 53333/50667/50667/56000
Modulation/Protocol/Compression : V.90/LAPM/V.42bis
TX Symbol rate : 3200
Signal Level (TX/Power Drop), -dB : 18/0
RX Signal Level (Last/Min/Max), -dB : 12/12/12
Band Edge Lower/Upper, Hz : 150/3825
Round trip delay, ms : 11.938
EQM Value (Last/Min/Max/Negative) : 22/14/79/0
EQM Samples Running Sum : 0076
EQM Last 10 Readings : 24 27 22 24 24 22 20 26 22 24
SNR Ratio (Last/Min/Max), dB : 46/46/46
TX Non-linear Encoding : OFF
TX Precoding : OFF
TX/RX Constellation Shaping : OFF/OFF
TX Trellis Encoding : 16 state
TX Pre-emphasis : 0
TX/RX state (Max TX/RX, Last TX/RX) : 87H/67H, 87H/65H
Error Correction Status : SABME:T UA:R XID:T,R SYNC
Dual PCM/120 Hz detection : No/No
Energy at 3750Hz/Average Energy : 5277/3548
RBS Pattern/Alternating RBS Pattern : 00/00
V.90 Digital Pad/A-law/HighPowerSrv : 1dB/Yes/No
Retrains (Issued/Granted/Fast) : 0/0/3
Renegs (Issued/Granted) : 4/0
Retrans per frame/Frames rejected : 1/107
Total number of REJ sent/received : 107/8
Last Retrain/Reneg reason : Fall-back due to high EQM
Last Retrain/Reneg requested : Local Fast Retrain
Minutes Since Last Retrain/Reneg : 0
Disconnect reason : LOCAL REQUEST
Remote Manufacturer/Licensee Code : Conexant/Conexant
Remote Manufacturer's Product Caps : K56Flex, V.90
Remote V.8bis caps (type) : Digital (Server)
Remote V.8bis caps (K56Flex mode) : K56Flex prototype mode not supported
Remote V.8bis caps (K56Flex version): 1.1
Remote K56Flex RAM version supported: 70
Remote Coding used/forced by server : A-law/Yes
Remote controller version number : 0
Remote supports symbol rate (1,2,5) : 2743:ON 2800:ON 3429:ON 3429-TX:ON
Remote supports symbol rate (3,4) : 3000-L:ON 3000-H:ON 3200-L:ON 3200-H:ON
Remote power drop support : ON
Remote max symbol rate difference : 0 steps
Remote is a CME modem : No
Remote supports V.34bis : Yes
Remote frequency source : Internal
Remote is ITU/K56Flex neg/High IMD : Yes/Yes/No
V.8 bis CRe detected/early : Yes/No
CRe/CRd/CL/MS/ACK/NAK received : Yes/No/Yes/No/Yes/No
V.8bis success/V.8bis neg started : Yes/Yes

Unimodem Diagnostics/W32, version 1.1.0.0, compiled at Mar 14 2002 18:01:05
(c) 2000 Stanislav V. Mekhanoshin (rampitec@tu.spb.ru, 2:5030/172.9@fidonet)
----------------------------------------------------------------------------
Diag Command Specification rev.: 1.0
Call Setup Result code : Data Answering signal detected
Multi-media mode : Data Only
DTE-DCE interface mode : Async data
TX/RX signal power level, -dBm : 18/13
Estimated noise level, -dBm : 56
TX/RX Negotiation : V.34/V.90 Issue 1 (asymmetric)
TX/RX Symbol Rate : 3200/8000
TX/RX Carrier frequency, Hz : 1829/0
TX data rate (Last/Init) : 28800/28800
RX data rate (Last/Init) : 53333/50666
Temporary carrier loss count : 0
Carrier Rate Re-neg count : 7
Retrains Requested/Granted : 0/0
Protocol/Compression : V.42 LAPM/V.42bis
Error control frame size, bytes: 128
Error control timeouts in TX : 4
Error control NAKs received : 8
Compression dict. size, bytes : 2048
TX/RX flow control : V.24 ckt 106/133 / V.24 ckt 106/133
TX/RX chars sent : 437197/1802009
TX/RX chars lost (data overrun): 0/0
TX/RX I-Frame count : 4528/14529
TX/RX I-Frame error count : 8/107
Termination Cause : cct108 turned Off

[Technical Support]

Вполне достойно и даже вызывает зависть (всем бы такие АТС)

Можно дополнительно ограничить скорость приёма до 54667 бит/с. Для этого в конец строки инициализации допишите команду:

+MS=,,,54667
_________________
Inpro
Technical Support

[Peter Stoliarov]

[Technical Support]

Редко, но бывают изменения к лучшему После ДШ АТС кажется, что "Интернет летает" ...
_________________
Inpro
Technical Support