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US bonding


I am using DOCSIS 3.0 CMTS, some modems are showing 2 US ,some only one.
Is there any problem with modems showing only one US? pls suggest

Aero#show cable modem fc4a.e91a.8bdd phy
MAC Address US IF DS IF Sid USPwr(dB) USSNR Timing MicroReflec DSPwr DSSNR Mode
TX RX (dB) Offset (dBc) (dB) (dB)
fc4a.e91a.8bdd 3/0.1/0 0/1/3 150 - 0.7 31.9 - - - - tdma

Aero#show cable modem fc4a.e912.7d14 phy
MAC Address US IF DS IF Sid USPwr(dB) USSNR Timing MicroReflec DSPwr DSSNR Mode
TX RX (dB) Offset (dBc) (dB) (dB)
fc4a.e912.7d14 3/0.0/0 0/1/3 8073 - 0.2 30.7 - - - - tdma
fc4a.e912.7d14 3/0.1/0 - 8073 - 0.7 31.9 - - - - tdma

Too much attenuation

This behavior may occur if the modem is unable to range on more than one upstream. Normally this happens if the modem is already at max transmit level on one channel and thus doesn't have enough power to bring up a second. Verify this by checking power transmit levels on the modem.

Could be the TX power

Could be the TX power difference between the US channels. I believe the spec says the upstream channels transmit power needs to be less than 12dB apart. If this is a lab environment, it's probably not the issue. But if this is a real world plant and the US channels are far enough away from each other, I could see where they would get to be more than 12dB apart.

Maybe stupid question

when cable modem is registered in wideband mode (ie. 4x4) is it transmitting with diffrent TX power on each upstream channel?

It is possible for different

It is possible for different channels to have different TX powers, it depends on the noise floor. Here is an example of a CM in a live plant. Since a live plant has more noise, the noise floor is higher with more of a tilt.

Upstream Channel : US0 US1
Upstream SNR (dB) : 33.97 32.30
Reported Transmit Power (dBmV) : 53.50 50.00

US0 - 30MHz
US1 - 23MHz

Here is an example from a lab CMTS, it's just a diplex filter and splitters/attenuation. My noise floor is very low and hardly any tilt. I'm testing 4 US channel bonding now in the lab.

Upstream Channel : US0 US1 US2 US3
Upstream SNR (dB) : 36.12 36.12 36.12 36.12
Reported Transmit Power (dBmV) : 45.25 45.25 45.25 45.25

US0 - 29.4 MHz
US1 - 26.1 MHz
US2 - 22.8 MHz
US3 - 19.5 MHz

Is it possible to check TX

Is it possible to check TX power via SNMP from modem? I know docsIfCmStatusTxPower - but it shows only TX of primary US. What about other channels?

Yes, you have to use DOCS-IF3

Yes, you have to use DOCS-IF3-MIBS for DOCSIS 3.0 specific SNMP information. Try using docsIf3CmStatusUsTxPower(

SNMPv2-SMI::enterprises.4491. = INTEGER: 457
SNMPv2-SMI::enterprises.4491. = INTEGER: 502

Cisco and Casa (maybe also

Cisco and Casa (maybe also others) have a "show cable modem remote-query " command. With it you can read values from CM over your CMTS.



is it possible to restrict modem come online if modem can't lock onto all US cannels in bondig group?

Not sure. Maybe you can

Not sure. Maybe you can increase power tolerance on your CMTS. Then your CM goes into US bonding even with a bad signal. Finally it has a bad SNR but is running in US bonding.
I would prefer that my customers stay online .

it is difficult to monitor

it is difficult to monitor this situation because uBR shows "C6/0/0/UB" but modem is locked only on US1

Why would the CM not be able

Why would the CM not be able to lock all the channels ?

One example I can think of is a mix of DOCSIS and EuroDOCSIS modems on the same plant :
* DOCSIS (6MHz) downstream
* Some upstreams below 42MHz, plus some above 42MHz.

In this case you want the DOCSIS modems only to use channels < 42MHz, whereas EuroDOCSIS modems can use all channels.

This can be implemented by using attribute masks on the bonding groups, plus adding the mask to the config file for DOCSIS modems

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