Three major standards exist for Cable Modems! Guess how many we need?
First generation Cable Modems uses various proprietary protocols etc.
making it impossible for the CATV network operators to use multiple vendors Cable Modems
on the same system.
Around 1997 three standards emerged. DAVIC/DVB were first with a European
standard, closely followed by MCSN with a US standard (DOCSIS). IEEE came last with
802.14, and clearly lost the 1st round. IEEE is now trying to leap-frog the two other
standards by focusing on the next generation standards.
DVB/DAVIC
This standard is also known as DVB-RCC and as ETS 300 800. Initially run
by DAVIC, but now the work has moved to DVB. Very few vendors develop for this standard,
but enough that it does play a role. This standard is fighting the EuroDOCSIS standard for
the European market (see below).
This standard is based on fixed cell size (ATM) and includes all the
standard ways of doing quality of service (QoS) that ATM is known for. In that way, the
standard is very well suited to both data i.e. TCP/IP (using AAL5) and telephony as pure
ATM. VoIP to the cable modem may not be the best solution, although technically feasible.
Initially the standard lacked security (encryption), but that was added as
an option in version 1.4.
Open to both internal and external implementations, and also covering
Set-Top Box implementations with an additional out-of-band receive data channel.
Some of the European cable operators joined forces and made a request for
proposals for a EuroModem. The specification is available to the public from EuroCableLabs
for free, and even though it does not seem very big, it does refer to other standards
including ETS 300 800 for the details. A PDF of the specification is available here.
MCNS/DOCSIS
The dominant US standard - even though it has not gone through any
formal/independent standards body yet. This standard is very much driven by the wish of
the large cable operators to have cable modems sold through the retail channel. Initially
the chip manufacturer Broadcom played an important role, by pushing the standard and the
level of chip integration at a very fast pace. As a result, the complexity of the standard
is generally agreed to be much higher than what is strictly required, and is even growing.
Initially the standard did not support QoS which is required for telephony
applications (VoIP) and other applications as well, but this has been added in version
1.1.
Initially open to only external box solutions with Ethernet interface, but
now also allows internal modems and USB modems. Host based processing solutions is still
debated (start 1999).
While originally targeted at the US domestic market, an off-spring named
EuroDOCSIS is being pushed as the solution to the DVB centric European market. EuroDOCSIS
is essentially the same as DOCSIS apart from the physical layer, which is DVB compliant in
EuroDOCSIS.
IEEE
Lost the 1st round of the Cable Modem standards battle. What happens down
the road remains to be seen. It looks like part of the IEEE group is working with Broadcom
and Terayon on the next generation physical layer with increased (30 Mbps) upstream
bitrate. This has also been termed DOCSIS 1.2, even though that does not seem to be
official, and is certainly not approved by the DOCSIS vendor community yet.
The DVB-RCC vs. EuroDOCSIS fight
The battle for the US domestic market is clearly won by the DOCSIS
standard, but the battle for the European market is still going on. It does not seem like
at very fair match, but nevertheless quite interesting. The following somewhat biased
"whitepapers" are among the most visible parts of the fight.
October 1998: Gregers Kronborg who is
Chairman DVB/DAVIC Interoperability Consortium but also co-founder of DVB cable modem
manufacturer COCOM writes this:Comparing
DVB RCC / DAVIC with OpenCable MCNS (PDF file - also available on the DVB website www.dvb.org).
May 1999: Tom Quigley from Broadcom
Corporation presents his "whitepaper" Euro-DOCSIS/DVB-RC Comparison
(PDF file - also available on the CableLabs website www.cablemodem.com) on a EuroDOCSIS promotion tour of some European
countries (Stockholm, Vienna, Paris, Zeist and London).
cable-modems.org
