This input reads packets from a DVB-C or an ATSC card from a DOCSIS stream. DOCSIS means Data Over Cable Service Interface Specification. This is the standard used by cable modems. Note that this only provide the downstream traffic since the upstream frequency is not in the supported range of any DVB-C card.

This input DOES NOT decrypt BPI enabled stream. This means that if you are sniffing a DOCSIS network where BPI is enabled, you will not have any usable packet to process. Everything will be encrypted and you will only have scrambled ethernet packet. However if you are only interested in the docsis layer, that will work for you.

DOCSIS 1.0 utilized the initial Baseline Privacy Interface (BPI) specification. BPI was later improved with the release of the Baseline Privacy Interface Plus (BPI+) specification used by DOCSIS 1.1 & 2.0. Most recently, a number of enhancements to the Baseline Privacy Interface were added as part of DOCSIS 3.0, and the specification was renamed “Security” (SEC).

See here for working DVB/ATSC cards and here for a listing of cable ISP and their BPI usage.

For quick step by step guide to start scanning, see this configuration example.

In this mode, the input tune to a given frequency, reads MPEG packets and rebuilds packet from this. It outputs either docsis or ethernet packets. Parameter for this modes :

• eurodocsis

Specifies if the input needs to use the EuroDOCSIS specifications or the normal (US) DOCSIS specifications.
Default : yes

• frequency

Frequency in hertz to tune to. Minimum : 91mHz for docsis and 112mHz for eurodocsis. Maximum : 858mHz.
Default : 440000000 Hz

• modulation

Two modulations are possible according to the standard : QAM64 and QAM256.
Default : QAM256

• adapter

This specifies which adapter to use in /dev/dvb/adapterX.
Default : 0

• frontend

This specifies what frontend to use in /dev/dvb/adapterX/frontendY.
Default : 0

• tuning_timeout

Number of seconds after which the input aborts if no lock was acquired on the given frequency.
Default : 3

• outlayer

Output layer of the input. Can be either docsis, ethernet and atm. Please note that atm is currently not implemented by any match and therefor cannot be used yet.
Default : ethernet

• validate_checksum

Perform checksum validation. Currently, only the DOCSIS header checksum is validated.
Default : yes

In this mode, the input will scan all the frequencies for a valid DOCSIS stream. It will start scanning from the lowest possible frequency up to the highest one. If you specify the parameter startfreq, it will start from this frequency. Once it founds a usable frequency, it will stop scanning and start dumping packets. This mode has same parameters than the normal mode besides frequency. It also has these parameters in addition :

• startfreq

Starting frequency in Hz of the scanning process. Minimum : 91000000Hz for docsis and 112000000Hz for eurodocsis.
Default : 0 (start from lowest)

• frontend_reinit

If this is set to yes, input_docsis will close and reopen the frontend device between each attempt to lock on a frequency. This makes things really slow but it's needed by some buggy drivers.
Default : no

This mode takes the raw MPEG TS stream from a file and will use it as a source. Since MPEG packets don't contain timing information, the starting time will be the ctime (last status change) of the file. Subsequent packet time will be approximated using the number of MPEG packets received and docsis SYNC messages which provide accurate delta values every 10ms.

• file

File to read MPEG TS packets from.
Default : dump.ts

This mode will use multiple cards to tune to all the downstream frequencies. You must have enough cards to handle all the frequencies. To tune, you only need to provide one single frequency and the input will tune to additional ones as they are found. The parameters are the same than mode normal but additional adapters can be specified. Only the needed adapters will be used, not all of them.