Negative US Margin

Rocky5 · Post by **Rocky5** » Mon Aug 11, 2008 9:33 pm

I have the MTNL MT882 router.
The following is the status on my router:-
Modem Status

Connection Status Connected
Us Rate (Kbps) 262
Ds Rate (Kbps) 2042
US Margin -5
DS Margin 31
Trained Modulation ADSL_2plus_AnxM
LOS Errors 0
DS Line Attenuation 26
US Line Attenuation 10
Peak Cell Rate 617 cells per sec
CRC Rx Fast 0
CRC Tx Fast 2
CRC Rx Interleaved 0
CRC Tx Interleaved 0
Path Mode Interleaved
DSL Statistics

Near End F4 Loop Back Count 0
Near End F5 Loop Back Count 0

Recently the US Margin has become negative while earlier it was positive. Should this be a cause of concern? Can this be the result of poor quality wires? My download speeds don't seem to be affected.

Also, how can I check the SNR Margin on my router?

Post by **mstombs** » Mon Aug 11, 2008 10:15 pm

Which firmware and which DSP version are you currently running?

Negative US margin may just be a standards communication issue, the US margin has to be reported by the ISP end.

What speeds are you expected to get with your ISP package? Annex M is usually used to get high upstream bandwidth - usually at least 1Mbps - more frequency slots are dedicated to upstream.

Rocky5 · Post by **Rocky5** » Tue Aug 12, 2008 10:38 am

I am using the MTNL MT882 router about which we have discussed before. I am using the default firmware.
I am expected to get 2mbps download and 256Kbps upload.
I also read in some forum that a DS Margin of 31 is a bit on the higher side.
Also can I check the SNR on my router?

Post by **mstombs** » Tue Aug 12, 2008 10:28 pm

Well, your MTNL code, still on my test box has these reports

Code: Select all

# cat /proc/avalanche/avsar_modem_stats

AR7 DSL Modem Statistics:
--------------------------------
[DSL Modem Stats]
        US Connection Rate:     0       DS Connection Rate:     0
        DS Line Attenuation:    0.0     DS Margin:              0.0
        US Line Attenuation:    0.0     US Margin:              0.0
        US Payload :            0       DS Payload:             0
        US Superframe Cnt :     0       DS Superframe Cnt:      0
        US Transmit Power :     0       DS Transmit Power:      0
        LOS errors:             0       SEF errors:             0
        Errored Seconds:        0       Severely Err Secs:      0
        Frame mode:             0       Max Frame mode:         0
        Trained Path:           0       US Peak Cell Rate:      0
        Trained Mode:           0       Selected Mode:          65535
        ATUC Vendor Code:       FFFFFFFF        ATUC Revision:  0
        Hybrid Selected:        0       Trellis:                1
        Showtime Count:         0       DS Max Attainable Bit Rate: 4294967264 kbps
        BitSwap:                1       US Max Attainable Bit Rate:     n/a
        Annex:                  Unknown psd_mask_qualifier: 0x0000
        Power Management Status: L0     DS HLINSC: 0
        US ACTPSD:              0       DS ACTPSD: 0
        Total init. errors:     0       Total init. timeouts: 0
        Showtime init. errors:  0       Showtime init. timeouts: 0
        Last showtime init. errors: 0   Last showtime init. timeouts: 0
        ATUC ghsVid:  80 84 25 a2 fe 56 7b d2
        T1413Vid: 00 00         T1413Rev: 00            VendorRev: 00
        ATUR ghsVid:  b5 00 54 53 54 43 00 00
        T1413Vid: 00 00 T1413Rev: 00    VendorRev: 00

Code: Select all

# cat /proc/avalanche/avsar_ver
ATM Driver version:[7.02.01.00]
DSL HAL version: [7.02.01.00]
DSP Datapump version: [7.02.03.00] Annex A
SAR HAL version: [01.07.2c]
PDSP Firmware version:[0.54]
Chipset ID: [7300/7300A]

The raw SNR can be plotted with tools such as RouterStats logger, but I'm not sure if telnet via CLI prompt will work. The margin is the best guide, a large margin is not an issue when you have a capped service, if uncapped the margin will fall to the target as the speed rises.

Rocky5 · Post by **Rocky5** » Wed Aug 13, 2008 10:13 pm

thats the info I was looking for. I will try router stats and see if it works.