The primary purpose of DOCSIS was to ensure interoperability between vendors’ equipment.
Different versions provide standards for security, encapsulation, management, QoS, and services.
There are three versions of the DOCSIS specification, as outlined in Table 28.1.
TABLE 2 8 . 1
DOCSIS Specifications
Version Features
DOCSIS 1.0 This was the original specification and provided for standardization
between vendors.
DOCSIS 1.1 This version of DOCSIS is commonly used today and provides basic
quality of service and security functions. This is very important for most
users, and cable networks leverage these features to protect user traffic
in transit from being intercepted. Please note that this does not protect
user machines from attack; the specifications are not firewalls, but rather
a switched emulation over the shared infrastructure. The specification is
backward compatible. DOCSIS 1.1 adds voice and streaming services.
This version also takes steps to prevent theft of service from the provider.
In previous specifications, a user with cable service could remove the filter
in the street and have data service for free.
DOCSIS 2.0 This new standard will provide six times the upstream capacity of DOCSIS 1.0
(three times the capacity of 1.1). The channel is increased to 6.4MHz for greater
capacity and efficiency. It is also backward compatible.
NOTE:DOCSIS specifies the connection between only the CMTS and the cable
modem or cable modem router. The PC, network router(s), and other network
elements are not involved. Readers wanting to study the DOCSIS 2.0 standard
should visit
www.cisco.com/en/US/netsol/ns469/networking_solutions_
event_and_seminar_home.html
, where a number of DOCSIS white papers are
available.