<s>
A	O
cable	B-Device
modem	I-Device
is	O
a	O
type	O
of	O
network	B-Protocol
bridge	I-Protocol
that	O
provides	O
bi-directional	O
data	O
communication	O
via	O
radio	O
frequency	O
channels	O
on	O
a	O
hybrid	B-Architecture
fibre-coaxial	I-Architecture
(	O
HFC	O
)	O
,	O
radio	B-Device
frequency	I-Device
over	I-Device
glass	I-Device
(	O
RFoG	B-Device
)	O
and	O
coaxial	O
cable	O
infrastructure	O
.	O
</s>
<s>
Cable	B-Device
modems	I-Device
are	O
primarily	O
used	O
to	O
deliver	O
broadband	B-General_Concept
Internet	O
access	O
in	O
the	O
form	O
of	O
cable	B-Device
Internet	I-Device
,	O
taking	O
advantage	O
of	O
the	O
high	O
bandwidth	B-Algorithm
of	O
a	O
HFC	O
and	O
RFoG	B-Device
network	O
.	O
</s>
<s>
Internet	O
Experiment	O
Note	O
(	O
IEN	O
)	O
96	O
(	O
1979	O
)	O
describes	O
an	O
early	O
RF	O
cable	B-Device
modem	I-Device
system	O
.	O
</s>
<s>
The	O
system	O
uses	O
standard	O
Community	O
Antenna	O
Television	O
(	O
CATV	O
)	O
coaxial	O
cable	O
and	O
microprocessor	O
based	O
Bus	O
Interface	B-Protocol
Units	O
(	O
BIUs	O
)	O
to	O
connect	O
subscriber	O
computers	O
and	O
terminals	O
to	O
the	O
cable	O
.	O
</s>
<s>
The	O
topology	B-Architecture
is	O
dendritic	O
(	O
i.e.	O
</s>
<s>
branched	B-Data_Structure
like	I-Data_Structure
a	I-Data_Structure
tree	I-Data_Structure
)	O
.	O
</s>
<s>
The	O
BIUs	O
contain	O
Radio	O
Frequency	O
(	O
RF	O
)	O
modems	O
which	O
modulate	B-Application
a	O
carrier	O
signal	O
to	O
transmit	O
digital	O
information	O
using	O
1	O
MHz	O
of	O
the	O
available	O
bandwidth	B-Algorithm
in	O
the	O
24	O
MHz	O
frequency	O
range	O
.	O
</s>
<s>
The	O
remainder	O
of	O
the	O
294	O
MHz	O
bandwidth	B-Algorithm
can	O
be	O
used	O
to	O
carry	O
other	O
communication	O
channels	O
,	O
such	O
as	O
off-the-air	O
TV	O
,	O
FM	O
,	O
closed	O
circuit	O
TV	O
,	O
or	O
a	O
voice	O
telephone	B-General_Concept
system	I-General_Concept
,	O
or	O
,	O
other	O
digital	O
channels	O
.	O
</s>
<s>
The	O
IEEE	O
802	O
Committee	O
defined	O
10BROAD36	O
in	O
802.3b-1985	O
as	O
a	O
10	O
Mbit/s	O
IEEE	O
802.3/Ethernet	O
broadband	B-General_Concept
system	O
to	O
run	O
up	O
to	O
over	O
CATV	O
coax	O
network	O
cabling	O
.	O
</s>
<s>
The	O
word	O
broadband	B-General_Concept
as	O
used	O
in	O
the	O
original	O
IEEE	O
802.3	O
specifications	O
implied	O
operation	O
in	O
frequency-division	O
multiplexed	O
(	O
FDM	B-Protocol
)	O
channel	O
bands	O
as	O
opposed	O
to	O
digital	O
baseband	B-Algorithm
square-waveform	O
modulations	B-Application
(	O
also	O
known	O
as	O
line	B-Protocol
coding	I-Protocol
)	O
,	O
which	O
begin	O
near	O
zero	O
Hz	O
and	O
theoretically	O
consume	O
infinite	O
frequency	B-Algorithm
bandwidth	I-Algorithm
.	O
</s>
<s>
In	O
the	O
market	O
10BROAD36	O
equipment	O
was	O
not	O
developed	O
by	O
many	O
vendors	O
nor	O
deployed	O
in	O
many	O
user	O
networks	O
as	O
compared	O
to	O
equipment	O
for	O
IEEE	O
802.3/Ethernet	O
baseband	B-Algorithm
standards	O
such	O
as	O
10BASE5	O
(	O
1983	O
)	O
,	O
10BASE2	O
(	O
1985	O
)	O
,	O
10BASE-T	B-Protocol
(	O
1990	O
)	O
,	O
etc	O
.	O
</s>
<s>
The	O
IEEE	O
802	O
Committee	O
also	O
specified	O
a	O
broadband	B-General_Concept
CATV	O
digital	O
networking	O
standard	O
in	O
1989	O
with	O
802.7-1989	O
.	O
</s>
<s>
Hybrid	O
Networks	O
developed	O
,	O
demonstrated	O
and	O
patented	O
the	O
first	O
high-speed	O
,	O
asymmetrical	O
cable	B-Device
modem	I-Device
system	O
in	O
1990	O
.	O
</s>
<s>
Hybrid	O
's	O
system	O
architecture	O
is	O
used	O
for	O
most	O
cable	B-Device
modem	I-Device
systems	O
today	O
.	O
</s>
<s>
LANcity	O
was	O
an	O
early	O
pioneer	O
in	O
cable	B-Device
modems	I-Device
,	O
developing	O
a	O
proprietary	O
system	O
that	O
was	O
widely	O
deployed	O
in	O
the	O
U.S.	O
LANcity	O
,	O
which	O
was	O
led	O
by	O
the	O
Iranian-American	O
engineer	O
Rouzbeh	O
Yassini	O
,	O
was	O
then	O
acquired	O
by	O
Bay	O
Networks	O
.	O
</s>
<s>
ARRIS	O
continues	O
to	O
make	O
cable	B-Device
modems	I-Device
and	O
cable	B-Device
modem	I-Device
termination	I-Device
system	I-Device
(	O
CMTS	O
)	O
equipment	O
compliant	O
with	O
the	O
DOCSIS	B-Protocol
standard	O
.	O
</s>
<s>
Zenith	O
offered	O
a	O
cable	B-Device
modem	I-Device
technology	O
using	O
its	O
own	O
protocol	O
which	O
it	O
introduced	O
in	O
1993	O
,	O
being	O
one	O
of	O
the	O
first	O
cable	B-Device
modem	I-Device
providers	O
.	O
</s>
<s>
The	O
Zenith	B-Device
Cable	I-Device
Modem	I-Device
technology	O
was	O
used	O
by	O
several	O
cable	O
television	O
systems	O
in	O
the	O
United	O
States	O
and	O
other	O
countries	O
,	O
including	O
Cox	O
Communications	O
San	O
Diego	O
,	O
Knology	O
in	O
the	O
Southeast	O
United	O
States	O
,	O
Ameritech	O
's	O
Americast	O
service	O
(	O
later	O
to	O
be	O
sold	O
off	O
to	O
Wide	O
Open	O
West	O
after	O
the	O
SBC	O
/	O
Ameritech	O
merger	O
)	O
,	O
Cogeco	O
in	O
Hamilton	O
Ontario	O
and	O
Cablevision	O
du	O
Nord	O
de	O
Québec	O
in	O
Val-d	O
'	O
Or	O
.	O
</s>
<s>
Zenith	O
Homeworks	O
used	O
BPSK	O
(	O
Bi-Phase	O
Shift	O
Keyed	O
)	O
modulation	B-Application
to	O
achieve	O
500	O
Kbit/sec	O
in	O
600kHz	O
,	O
or	O
4	O
Mbit/sec	O
in	O
6MHz	O
.	O
</s>
<s>
Com21	B-Device
was	O
another	O
early	O
pioneer	O
in	O
cable	B-Device
modems	I-Device
,	O
and	O
quite	O
successful	O
until	O
proprietary	O
systems	O
were	O
made	O
obsolete	O
by	O
the	O
DOCSIS	B-Protocol
standardization	O
.	O
</s>
<s>
The	O
Com21	B-Device
system	O
used	O
a	O
ComController	O
as	O
central	O
bridge	O
in	O
CATV	O
network	O
head-ends	O
,	O
the	O
ComPort	O
cable	B-Device
modem	I-Device
in	O
various	O
models	O
and	O
the	O
NMAPS	O
management	O
system	O
using	O
HP	B-Application
OpenView	I-Application
as	O
platform	O
.	O
</s>
<s>
The	O
remaining	O
slots	O
could	O
be	O
used	O
for	O
upstream	O
receivers	O
(	O
2	O
per	O
card	O
)	O
,	O
dual	O
Ethernet	B-Protocol
10BaseT	I-Protocol
and	O
later	O
also	O
Fast-Ethernet	O
and	O
ATM	O
interfaces	O
.	O
</s>
<s>
The	O
ATM	O
interface	B-Protocol
became	O
the	O
most	O
popular	O
,	O
as	O
it	O
supported	O
the	O
increasing	O
bandwidth	B-Algorithm
demands	O
and	O
also	O
supported	O
VLANs	B-General_Concept
.	O
</s>
<s>
Com21	B-Device
developed	O
a	O
DOCSIS	B-Protocol
modem	O
,	O
but	O
the	O
company	O
filed	O
for	O
bankruptcy	O
in	O
2003	O
and	O
closed	O
.	O
</s>
<s>
The	O
DOCSIS	B-Protocol
CMTS	O
assets	O
of	O
COM21	B-Device
were	O
acquired	O
by	O
ARRIS	O
.	O
</s>
<s>
CDLP	B-Device
was	O
a	O
proprietary	O
system	O
manufactured	O
by	O
Motorola	O
.	O
</s>
<s>
CDLP	B-Device
customer	O
premises	O
equipment	O
(	O
CPE	O
)	O
was	O
capable	O
of	O
both	O
PSTN	O
(	O
telephone	O
network	O
)	O
and	O
radio	O
frequency	O
(	O
cable	B-Protocol
network	I-Protocol
)	O
return	O
paths	O
.	O
</s>
<s>
Cable	B-Device
modems	I-Device
that	O
used	O
the	O
RF	O
cable	B-Protocol
network	I-Protocol
for	O
the	O
return	O
path	O
were	O
considered	O
'	O
two-way	O
cable	O
 '	O
,	O
and	O
were	O
better	O
able	O
to	O
compete	O
with	O
the	O
bi-directional	O
digital	O
subscriber	O
line	O
(	O
DSL	O
)	O
service	O
.	O
</s>
<s>
The	O
standard	O
is	O
in	O
little	O
use	O
now	O
as	O
new	O
providers	O
use	O
,	O
and	O
existing	O
providers	O
having	O
changed	O
to	O
,	O
the	O
DOCSIS	B-Protocol
standard	O
.	O
</s>
<s>
The	O
Motorola	O
CDLP	B-Device
proprietary	O
CyberSURFR	O
is	O
an	O
example	O
of	O
a	O
device	O
that	O
was	O
built	O
to	O
the	O
CDLP	B-Device
standard	O
,	O
capable	O
of	O
a	O
peak	O
10	O
Mbit/s	O
downstream	O
and	O
1.532	O
Mbit/s	O
upstream	O
.	O
</s>
<s>
CDLP	B-Device
supported	O
a	O
maximum	O
downstream	O
bandwidth	B-Algorithm
of	O
30	O
Mbit/s	O
which	O
could	O
be	O
reached	O
by	O
using	O
several	O
cable	B-Device
modems	I-Device
.	O
</s>
<s>
The	O
Australian	O
ISP	O
BigPond	O
employed	O
this	O
system	O
when	O
it	O
started	O
cable	B-Device
modem	I-Device
tests	O
in	O
1996	O
.	O
</s>
<s>
For	O
a	O
number	O
of	O
years	O
cable	B-Device
Internet	I-Device
access	I-Device
was	O
only	O
available	O
in	O
Sydney	O
,	O
Melbourne	O
and	O
Brisbane	O
via	O
CDLP	B-Device
.	O
</s>
<s>
This	O
network	O
ran	O
parallel	O
to	O
the	O
newer	O
DOCSIS	B-Protocol
system	O
for	O
several	O
years	O
.	O
</s>
<s>
In	O
2004	O
,	O
the	O
CDLP	B-Device
network	O
was	O
terminated	O
and	O
replaced	O
by	O
DOCSIS	B-Protocol
.	O
</s>
<s>
CDLP	B-Device
has	O
been	O
also	O
rolled	O
out	O
at	O
the	O
French	O
cable	O
operator	O
Numericable	O
before	O
upgrading	O
its	O
IP	O
broadband	B-General_Concept
network	O
using	O
DOCSIS	B-Protocol
.	O
</s>
<s>
Digital	B-Application
Video	I-Application
Broadcasting	I-Application
(	O
DVB	B-Application
)	O
and	O
Digital	O
Audio	O
Visual	O
Council	O
(	O
DAVIC	O
)	O
are	O
European-formed	O
organizations	O
that	O
developed	O
some	O
cable	B-Device
modem	I-Device
standards	O
.	O
</s>
<s>
However	O
,	O
these	O
standards	O
have	O
not	O
been	O
as	O
widely	O
adopted	O
as	O
DOCSIS	B-Protocol
.	O
</s>
<s>
In	O
the	O
mid-1990s	O
the	O
IEEE	O
802	O
committee	O
formed	O
a	O
subcommittee	O
(	O
802.14	O
)	O
to	O
develop	O
a	O
standard	O
for	O
cable	B-Device
modem	I-Device
systems	O
.	O
</s>
<s>
However	O
,	O
the	O
802.14	O
working	O
group	O
was	O
disbanded	O
when	O
North	O
American	O
multi	O
system	O
operators	O
(	O
MSOs	O
)	O
instead	O
backed	O
the	O
then-fledgling	O
DOCSIS	B-Protocol
1.0	I-Protocol
specification	O
,	O
which	O
generally	O
used	O
best-effort	O
service	O
and	O
was	O
IP-based	B-Protocol
(	O
with	O
extension	O
codepoints	O
to	O
support	O
ATM	O
for	O
QoS	O
in	O
the	O
future	O
)	O
.	O
</s>
<s>
MSOs	O
were	O
interested	O
in	O
quickly	O
deploying	O
service	O
to	O
compete	O
for	O
broadband	B-General_Concept
Internet	O
access	O
customers	O
instead	O
of	O
waiting	O
on	O
the	O
slower	O
,	O
iterative	O
,	O
and	O
deliberative	O
processes	O
of	O
standards	O
development	O
committees	O
.	O
</s>
<s>
Albert	O
A	O
.	O
Azzam	O
was	O
Secretary	O
of	O
the	O
IEEE	O
802.14	O
Working	O
Group	O
,	O
and	O
his	O
book	O
,	O
High-Speed	O
Cable	B-Device
Modems	I-Device
,	O
describes	O
many	O
of	O
the	O
proposals	O
submitted	O
to	O
802.14	O
.	O
</s>
<s>
Although	O
the	O
Internet	O
Engineering	O
Task	O
Force	O
(	O
IETF	O
)	O
generally	O
does	O
not	O
generate	O
complete	O
cable	B-Device
modem	I-Device
standards	O
,	O
the	O
IETF	O
chartered	O
Working	O
Groups	O
(	O
WGs	O
)	O
that	O
produced	O
various	O
standards	O
related	O
to	O
cable	B-Device
modem	I-Device
technologies	O
(	O
including	O
802.14	O
,	O
DOCSIS	B-Protocol
,	O
PacketCable	B-Device
,	O
and	O
others	O
)	O
.	O
</s>
<s>
In	O
particular	O
,	O
the	O
IETF	O
WGs	O
on	O
IP	O
over	O
Cable	O
Data	O
Network	O
(	O
IPCDN	O
)	O
and	O
IP	O
over	O
Digital	B-Application
Video	I-Application
Broadcasting	I-Application
(	O
DVB	B-Application
)	O
produced	O
some	O
standards	O
applicable	O
to	O
cable	B-Device
modem	I-Device
systems	O
,	O
primarily	O
in	O
the	O
areas	O
of	O
Simple	B-Protocol
Network	I-Protocol
Management	I-Protocol
Protocol	I-Protocol
(	O
SNMP	B-Protocol
)	O
Management	O
Information	O
Bases	O
(	O
MIBs	O
)	O
for	O
cable	B-Device
modems	I-Device
and	O
other	O
networking	O
equipment	O
that	O
operates	O
over	O
CATV	O
networks	O
.	O
</s>
<s>
In	O
the	O
late	O
1990s	O
,	O
a	O
consortium	O
of	O
US	O
cable	O
operators	O
,	O
known	O
as	O
"	O
MCNS	O
"	O
formed	O
to	O
quickly	O
develop	O
an	O
open	O
and	O
interoperable	O
cable	B-Device
modem	I-Device
specification	O
.	O
</s>
<s>
The	O
group	O
essentially	O
combined	O
technologies	O
from	O
the	O
two	O
dominant	O
proprietary	O
systems	O
at	O
the	O
time	O
,	O
taking	O
the	O
physical	B-Application
layer	I-Application
from	O
the	O
Motorola	O
CDLP	B-Device
system	O
and	O
the	O
MAC	B-Protocol
layer	I-Protocol
from	O
the	O
LANcity	O
system	O
.	O
</s>
<s>
When	O
the	O
initial	O
specification	O
had	O
been	O
drafted	O
,	O
the	O
MCNS	O
consortium	O
handed	O
over	O
control	O
of	O
it	O
to	O
CableLabs	O
which	O
maintained	O
the	O
specification	O
,	O
promoted	O
it	O
in	O
various	O
standards	O
organizations	O
(	O
notably	O
SCTE	O
and	O
ITU	O
)	O
,	O
developed	O
a	O
certification	O
testing	O
program	O
for	O
cable	B-Device
modem	I-Device
equipment	O
,	O
and	O
has	O
since	O
drafted	O
multiple	O
extensions	O
to	O
the	O
original	O
specification	O
.	O
</s>
<s>
While	O
deployed	O
DOCSIS	B-Protocol
RFI	I-Protocol
1.0	I-Protocol
equipment	O
generally	O
only	O
supports	O
best	O
efforts	O
service	O
,	O
the	O
DOCSIS	B-Protocol
RFI	I-Protocol
1.0	I-Protocol
Interim-01	O
document	O
discussed	O
QoS	O
extensions	O
and	O
mechanisms	O
using	O
IntServ	O
,	O
RSVP	B-Protocol
,	O
RTP	B-Protocol
,	O
and	O
Synchronous	O
Transfer	O
Mode	O
(	O
STM	O
)	O
telephony	O
(	O
as	O
opposed	O
to	O
ATM	O
)	O
.	O
</s>
<s>
DOCSIS	B-Protocol
RFI	I-Protocol
1.1	I-Protocol
later	O
added	O
more	O
robust	O
and	O
standardized	O
QoS	O
mechanisms	O
to	O
DOCSIS	B-Protocol
.	O
</s>
<s>
DOCSIS	B-Protocol
2.0	I-Protocol
added	O
support	O
for	O
S-CDMA	O
PHY	O
,	O
while	O
DOCSIS	B-Protocol
3.0	I-Protocol
added	O
IPv6	B-Protocol
support	O
and	O
channel	B-Architecture
bonding	I-Architecture
to	O
allow	O
a	O
single	O
cable	B-Device
modem	I-Device
to	O
use	O
concurrently	O
more	O
than	O
one	O
upstream	O
channel	O
and	O
more	O
than	O
one	O
downstream	O
channel	O
in	O
parallel	O
.	O
</s>
<s>
Virtually	O
all	O
cable	B-Device
modems	I-Device
operating	O
in	O
the	O
field	O
today	O
are	O
compliant	O
with	O
one	O
of	O
the	O
DOCSIS	B-Protocol
versions	O
.	O
</s>
<s>
Because	O
of	O
the	O
differences	O
in	O
the	O
European	O
PAL	B-Language
and	O
USA	O
's	O
NTSC	O
systems	O
two	O
main	O
versions	O
of	O
DOCSIS	B-Protocol
exist	O
,	O
DOCSIS	B-Protocol
and	O
EuroDOCSIS	B-Protocol
.	O
</s>
<s>
A	O
third	O
variant	O
of	O
DOCSIS	B-Protocol
was	O
developed	O
in	O
Japan	O
and	O
has	O
seen	O
limited	O
deployment	O
in	O
that	O
country	O
.	O
</s>
<s>
Although	O
interoperability	O
"	O
was	O
the	O
whole	O
point	O
of	O
the	O
DOCSIS	B-Protocol
project	O
,	O
"	O
most	O
cable	O
operators	O
only	O
approve	O
a	O
very	O
restricted	O
list	O
of	O
cable	B-Device
modems	I-Device
on	O
their	O
network	O
,	O
identifying	O
the	O
'	O
allowed	O
 '	O
modems	O
by	O
their	O
brand	O
,	O
models	O
,	O
sometimes	O
firmware	O
version	O
and	O
occasionally	O
going	O
as	O
far	O
as	O
imposing	O
a	O
hardware	O
version	O
of	O
the	O
modem	O
,	O
instead	O
of	O
simply	O
allowing	O
a	O
supported	O
DOCSIS	B-Protocol
version	O
.	O
</s>
<s>
In	O
2017	O
,	O
Multimedia	O
over	O
Coax	O
Alliance	O
introduced	O
MoCA	O
Access	O
specification	O
,	O
based	O
on	O
the	O
MoCA	O
2.5	O
standard	O
,	O
suitable	O
for	O
addressing	O
broadband	B-General_Concept
network	O
access	O
in-building	O
using	O
coaxial	O
cabling	O
.	O
</s>
<s>
With	O
the	O
development	O
of	O
voice	B-Application
over	I-Application
Internet	I-Application
Protocol	I-Application
(	O
VoIP	B-Application
)	O
telephony	O
,	O
analog	B-Protocol
telephone	I-Protocol
adapters	I-Protocol
(	O
ATA	O
)	O
have	O
been	O
incorporated	O
into	O
many	O
cable	B-Device
modems	I-Device
for	O
providing	O
telephone	O
service	O
.	O
</s>
<s>
Many	O
cable	O
TV	O
service	O
providers	O
also	O
offer	O
VoIP-based	O
telephone	O
service	O
via	O
the	O
cable	O
infrastructure	O
(	O
PacketCable	B-Device
)	O
.	O
</s>
<s>
Some	O
high-speed	O
Internet	O
customers	O
may	O
use	O
VoIP	B-Application
telephony	I-Application
by	O
subscribing	O
to	O
a	O
third-party	O
service	O
,	O
such	O
as	O
Vonage	O
,	O
MagicJack+	B-Protocol
and	O
NetTALK	B-Algorithm
.	O
</s>
<s>
In	O
network	B-Architecture
topology	I-Architecture
,	O
a	O
cable	B-Device
modem	I-Device
is	O
a	O
network	B-Protocol
bridge	I-Protocol
that	O
conforms	O
to	O
IEEE	O
802.1D	O
for	O
Ethernet	O
networking	O
(	O
with	O
some	O
modifications	O
)	O
.	O
</s>
<s>
The	O
cable	B-Device
modem	I-Device
bridges	O
Ethernet	O
frames	O
between	O
a	O
customer	O
LAN	B-General_Concept
and	O
the	O
coax	O
network	O
.	O
</s>
<s>
Technically	O
,	O
it	O
is	O
a	O
modem	O
because	O
it	O
must	O
modulate	B-Application
data	O
to	O
transmit	O
it	O
over	O
the	O
cable	B-Protocol
network	I-Protocol
,	O
and	O
it	O
must	O
demodulate	O
data	O
from	O
the	O
cable	B-Protocol
network	I-Protocol
to	O
receive	O
it	O
.	O
</s>
<s>
With	O
respect	O
to	O
the	O
OSI	O
model	O
of	O
network	B-Architecture
design	I-Architecture
,	O
a	O
cable	B-Device
modem	I-Device
is	O
both	O
physical	B-Application
layer	I-Application
(	O
layer	B-Application
1	I-Application
)	O
device	O
and	O
a	O
data	B-Protocol
link	I-Protocol
layer	I-Protocol
(	O
layer	B-Protocol
2	I-Protocol
)	O
forwarder	O
.	O
</s>
<s>
As	O
an	O
IP	O
addressable	O
network	O
node	O
,	O
cable	B-Device
modems	I-Device
support	O
functionality	O
at	O
other	O
layers	O
.	O
</s>
<s>
Layer	B-Application
1	I-Application
is	O
implemented	O
in	O
the	O
Ethernet	B-Protocol
PHY	I-Protocol
on	O
its	O
LAN	B-General_Concept
interface	B-Protocol
,	O
and	O
a	O
DOCSIS	B-Protocol
defined	O
cable-specific	O
PHY	O
on	O
its	O
HFC	O
cable	O
interface	B-Protocol
.	O
</s>
<s>
The	O
term	O
cable	B-Device
modem	I-Device
refers	O
to	O
this	O
cable-specific	O
PHY	O
.	O
</s>
<s>
The	O
Network	B-Application
Layer	I-Application
(	O
Layer	B-Application
3	I-Application
)	O
is	O
implemented	O
as	O
an	O
IP	O
host	O
in	O
that	O
it	O
has	O
its	O
own	O
IP	B-Protocol
address	I-Protocol
used	O
by	O
the	O
network	O
operator	O
to	O
maintain	O
the	O
device	O
.	O
</s>
<s>
In	O
the	O
transport	B-Architecture
layer	I-Architecture
(	O
layer	B-Architecture
4	I-Architecture
)	O
the	O
cable	B-Device
modem	I-Device
supports	O
UDP	B-Protocol
in	O
association	O
with	O
its	O
own	O
IP	B-Protocol
address	I-Protocol
,	O
and	O
it	O
supports	O
filtering	O
based	O
on	O
TCP	B-Protocol
and	I-Protocol
UDP	I-Protocol
port	I-Protocol
numbers	O
to	O
,	O
for	O
example	O
,	O
block	O
forwarding	O
of	O
NetBIOS	B-Protocol
traffic	O
out	O
of	O
the	O
customer	O
's	O
LAN	B-General_Concept
.	O
</s>
<s>
In	O
the	O
Application	B-Application
Layer	I-Application
(	O
Layer	O
7	O
)	O
,	O
the	O
cable	B-Device
modem	I-Device
supports	O
certain	O
protocols	O
that	O
are	O
used	O
for	O
management	O
and	O
maintenance	O
,	O
notably	O
Dynamic	B-Protocol
Host	I-Protocol
Configuration	I-Protocol
Protocol	I-Protocol
(	O
DHCP	B-Protocol
)	O
,	O
SNMP	B-Protocol
,	O
and	O
TFTP	B-Device
.	O
</s>
<s>
Some	O
cable	B-Device
modems	I-Device
may	O
incorporate	O
a	O
router	B-Protocol
and	O
a	O
DHCP	B-Protocol
server	I-Protocol
to	O
provide	O
the	O
LAN	B-General_Concept
with	O
IP	O
network	O
addressing	O
.	O
</s>
<s>
From	O
a	O
data	O
forwarding	O
and	O
network	B-Architecture
topology	I-Architecture
perspective	O
,	O
this	O
router	B-Protocol
functionality	O
is	O
typically	O
kept	O
distinct	O
from	O
the	O
cable	B-Device
modem	I-Device
functionality	O
(	O
at	O
least	O
logically	O
)	O
even	O
though	O
the	O
two	O
may	O
share	O
a	O
single	O
enclosure	O
and	O
appear	O
as	O
one	O
unit	O
,	O
sometimes	O
called	O
a	O
residential	B-Application
gateway	I-Application
.	O
</s>
<s>
So	O
,	O
the	O
cable	B-Device
modem	I-Device
function	O
will	O
have	O
its	O
own	O
IP	B-Protocol
address	I-Protocol
and	O
MAC	O
address	O
as	O
will	O
the	O
router	B-Protocol
.	O
</s>
<s>
Cable	B-Device
modems	I-Device
can	O
have	O
a	O
problem	O
known	O
in	O
industry	O
jargon	O
as	O
"	O
flap	O
"	O
or	O
"	O
flapping	O
"	O
.	O
</s>
<s>
In	O
January	O
2020	O
,	O
a	O
vulnerability	O
affecting	O
cable	B-Device
modems	I-Device
using	O
Broadcom	O
chipsets	O
was	O
disclosed	O
and	O
named	O
Cable	B-Language
Haunt	I-Language
.	O
</s>
<s>
Exploits	O
are	O
possible	O
because	O
of	O
the	O
use	O
of	O
default	O
credentials	O
in	O
the	O
spectrum	O
analyzer	O
component	O
of	O
the	O
modem	O
(	O
mostly	O
used	O
for	O
debugging	O
purposes	O
)	O
accessible	O
through	O
a	O
network	B-Protocol
port	I-Protocol
which	O
is	O
open	O
by	O
default	O
in	O
the	O
vulnerable	O
models	O
.	O
</s>
