The term cable Internet access (or simply cable) refers to the delivery of
broadband Internet service over the CATV infrastructure.
Broadband Cable should not be confused with older
LAN systems such as 10base2 or 10base5 that used coaxial cables — and especially
not with 10broad36, which actually utilized the same sort of cable as CATV
Cable modem for broadband internet access
Cable modems are primarily used to deliver broadband Internet access, taking
advantage of unused bandwidth on a cable television network.
Along with digital subscriber line technology, cable modems ushered in the age
of broadband Internet access in developed countries. Prior to the availability
of such systems, Internet access involved slow dial-up access over a public
switched telephone network.
Users in a neighborhood share the available bandwidth provided by a single
coaxial cable line. Therefore, connection speed can vary depending on how many
people are using the service at the same time.
Often the idea of a shared line is seen as a weak point of cable Internet
access. From a technical point of view, all networks, including DSL services,
are sharing a fixed amount of bandwidth between a multitude of users — but
because cable networks tend to be spread over larger areas than DSL services,
more care must be taken to ensure good network performance.
A more significant weakness of cable networks using a shared line is the risk of
loss of privacy, especially considering the availability of hacking tools for
cable modems. This issue is addressed by encryption and other privacy features
specified in the DOCSIS (Data Over Cable Service Interface Specification)
standard used by most cable modems.
Cable Modems and VoIP
With the advent of Voice over IP telephony, cable modems can also
be used to provide telephone service. Many people who have cable modems have
opted to eliminate their Plain Old Telephone Service (POTS). Because most
telephone companies do not offer naked DSL, DSL service without a POTS (Plain
Old Telephone Service) line, many VoIP users prefer cable modems.
VoIP and other new data services that require broadband Internet access are
driving demand for increased bandwidth delivery via cable modems. As of 2005,
several national cable systems in the United States have announced plans to
upgrade their networks to meet this demand.
Confusing Usage of "Broadband"
While many lower rate forms of data transmission,
such as analog modems above 600 bit/s, are broadband, broadband has been more
closely associated with higher data rate forms of broadband data transmission
such as T-carrier and Digital Subscriber Lines. Therefore, the word "broadband"
has also come to mean a relatively high rate, while the term "narrowband" is
used to mean a relatively low rate. It is now quite common to hear a broadband
method such as a 9600 bit/s modem described as "narrowband", while a high rate
narrowband method such as 10BASE-T is described as "broadband". The
International Telecommunication Union Standardization Sector (ITU-T)
recommendation I.113 has defined broadband as a transmission capacity that is
faster than primary rate ISDN, at 1.5 to 2 Mbit/s. However speeds of 256 kbit/s
and greater are commonly marketed as "broadband" and this convention is held to
by policy makers and ISPs alike. See Broadband Internet access. Note: The term
"narrowband" is also used to mean the opposite of "wideband" instead of the
opposite of "broadband".