DOCSIS provides great variety in options available at Open Systems Interconnection (OSI) layers 1 and 2, the Physical (PHY) and Media Access Control (MAC) layers.
Physical layer
Channel Width: DOCSIS 1.0/1.1 specified channel widths between 200 kHz and 3.2 MHz. DOCSIS 2.0 specifies 6.4 MHz, but is backward compatible to the earlier, narrower channel widths.
Modulation: DOCSIS 1.0/1.1/2.0 specifies that 64-level or 256-level QAM (64-QAM or 256-QAM) be used for modulation of downstream data, and QPSK or 16-level QAM (16-QAM) be used for upstream modulation. DOCSIS 2.0 specifies 32-QAM, 64-QAM and 128-QAM also be available for upstream use.
MAC layer
DOCSIS employs a mixture of deterministic access methods, specifically TDMA for DOCSIS 1.0/1.1 and both TDMA and S-CDMA for DOCSIS 2.0, with a limited use of contention for bandwidth requests. In contrast to the pure contention-based MAC CSMA/CD employed in older Ethernet systems (there is no contention in switched Ethernet), DOCSIS systems experience few collisions. For DOCSIS 1.1 and above the MAC layer also includes extensive Quality of Service (QoS) features that help to efficiently support applications, for example Voice over IP, that have specific traffic requirements, such as low latency.
Throughput
All of these features combined enable a total upstream throughput of 30.72 Mbit/s per channel (although the upstream speed in DOCSIS 1.0 and 1.1 is limited to 10.24 Mbit/s). All three versions of the DOCSIS standard support a downstream throughput of up to 42.88 Mbit/s per channel with 256-QAM (owing to 8 MHz channel width, the EuroDOCSIS standard supports downstream throughput of up to 55.62 Mbit/s per channel).
DOCSIS 3.0 features management over IPv6 and channel bonding, which enables multiple downstream and upstream channels to be used together at the same time by a single subscriber.
The new ‘DOCSIS 2.0 + IPv6′ standard also supports IPv6, which may on the cable modem side only require a firmware upgrade
source: wikipedia.org