i mean, i read on adelphia.com that they provide a cable modem and a NIC, i have a NIC and a router already. cant i just plug the cable internet into the router? or does the cable modem convert from coax to cat5? dont some cable/DSL routers have that built in?
do i need a cable modem if i have a router and a nic
- Thread starter aUt0eXebat
- Start date
You won't need the nic. You will need the cable modem, unless your router has a built in cable modem that is compatible with the cable co.'s network.
ok, so the cable modem also serves as a nic? so i can connect to the other pc's as well?
No, the Cable modem is what is called a "bridge" it converts from one type of communication to another (in this case what ever the cable company is using [i.e. ATM or whatever] to ethernet).
Ethernet is what your NIC uses. You need the cable modem from the cable company unless your router has a built in cable modem that uses that same type of communication as that cable company does.
No, the Cable modem is what is called a "bridge" it converts from one type of communication to another (in this case what ever the cable company is using [i.e. ATM or whatever] to ethernet).
Ethernet is what your NIC uses. You need the cable modem from the cable company unless your router has a built in cable modem that uses that same type of communication as that cable company does.
<< ok, so the cable modem also serves as a nic? so i can connect to the other pc's as well? >>
Given a standard definition of a Network Interface Card(NIC), no a Cable Modem doesn't contain a NIC.
Simple schematic for multiple PC's to a Cable modem -
PC's to Switch(maybe included in the router or standalone) to router to cable modem to Internet.
- Oct 25, 1999
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The connection is:
Cable -Cable Modem ? Cable/DSL Router ? NIC (in computer).
Cisco makes DSL modems with a Router in one box. I don?t remember Cable Modem with Router in one box. But the Internet is big - Search.
Hub, Switch, Router, DHCP, LAN, WAN, NAT, etc
Cable -Cable Modem ? Cable/DSL Router ? NIC (in computer).
Cisco makes DSL modems with a Router in one box. I don?t remember Cable Modem with Router in one box. But the Internet is big - Search.
Hub, Switch, Router, DHCP, LAN, WAN, NAT, etc
<< ok, so the cable modem also serves as a nic? so i can connect to the other pc's as well?
No, the Cable modem is what is called a "bridge" it converts from one type of communication to another (in this case what ever the cable company is using [i.e. ATM or whatever] to ethernet).
Ethernet is what your NIC uses. You need the cable modem from the cable company unless your router has a built in cable modem that uses that same type of communication as that cable company does. >>
Bridge or a router depending on how it works.
quote:
<< the Cable modem is what is called a "bridge" it converts from one type of communication to another (in this case what ever the cable company is using [i.e. ATM or whatever] to ethernet). >>
Definitions:
BRIDGE
a product that connects a local area network (LAN) to another local area network that uses the same protocol
GATEWAY
a network point that acts as an entrance to another network [using a different protocol].
MODEM
modulates outgoing digital signals from a computer or other digital device to analog signals for a conventional copper twisted pair telephone line and demodulates the incoming analog signal and converts it to a digital signal for the digital device.
So wouldn't the Cable modem be...a modem (converting the BROADband [analog] signal from the ISP to the BASEband [digital] signal used in Ethernet comm?
So the most basic diagram would be:
<-->(Cable)<-->(Modem)<-->(NIC)<-->[COMPUTER]
The Sarge
USAF Tech Controller (3C2X1)
<< the Cable modem is what is called a "bridge" it converts from one type of communication to another (in this case what ever the cable company is using [i.e. ATM or whatever] to ethernet). >>
Definitions:
BRIDGE
a product that connects a local area network (LAN) to another local area network that uses the same protocol
GATEWAY
a network point that acts as an entrance to another network [using a different protocol].
MODEM
modulates outgoing digital signals from a computer or other digital device to analog signals for a conventional copper twisted pair telephone line and demodulates the incoming analog signal and converts it to a digital signal for the digital device.
So wouldn't the Cable modem be...a modem (converting the BROADband [analog] signal from the ISP to the BASEband [digital] signal used in Ethernet comm?
So the most basic diagram would be:
<-->(Cable)<-->(Modem)<-->(NIC)<-->[COMPUTER]
The Sarge
USAF Tech Controller (3C2X1)
A cable modem really isn't a modem. It does not MODulate/DEmodulate anything as the signal is digital to begin with.
As far a networking goes it can be a bridge or a router depending on provider.
As far a networking goes it can be a bridge or a router depending on provider.
Quote from here:
The fact that the word "modem" is used to describe this device can be a little misleading only in that it conjures up images of a typical telephone dial-up modem. Yes, it is a modem in the true sense of the word since it MOdulates and DEModulates signals. But the similarity ends there because cable modems are practically an order of magnitude more complicated than their telephone counterparts. Cable modems can be part modem, part tuner, part encryption/decryption device, part bridge, part router, part network interface card, part SNMP agent, and part Ethernet hub. Typically, a cable modem sends and receives data in two slightly different fashions. In the downstream direction, the digital data is modulated and then placed on a typical 6 MHz television channel, somewhere between 50 MHz and 750 MHz. Currently, 64 QAM is the preffered downstream modulation technique, offering up to 27 Mbps per 6 MHz channel. This signal can be placed in a 6 MHz channel adjacent to TV signals on either side without disturbing the cable television video signals.
The upstream channel is more tricky. Typically, in a two-way activated cable network, the upstream (also known as the reverse path) is transmitted between 5 and 42 MHz.
This tends to be a noisy environment, with RF interference and impulse noise. Additionally, interference is easily introduced in the home, due to loose connectors or poor cabling. Since cable networks are tree and branch networks, all this noise gets added together as the signals travel upstream, combining and increasing. Due to this problem, most manufacturers use QPSK or a similar modulation scheme in the upstream direction, because QPSK is more robust scheme than higher order modulation techniques in a noisy environment. The drawback is that QPSK is "slower" than QAM.
My Take:
Boy, that's a lot of techno babble!
When you subscribe to cable internet access, the ISP is actually assigning you your very own CATV channel. Kinda. There are not enough "channels" in the CATV range for everyone. I am sure there are "neighborhood" multiplexers. Any Cable ISP employees out there to clarify?
The Sarge
USAF Tech Controller
Edited: Oops! 27Mbps per 6MHz channel...boy it would be nice to have my own individual CATV channel...they probably share the "analog bandwidth" of each channel (or use the extra for buffer) between users (1.5Mbps max?)
The fact that the word "modem" is used to describe this device can be a little misleading only in that it conjures up images of a typical telephone dial-up modem. Yes, it is a modem in the true sense of the word since it MOdulates and DEModulates signals. But the similarity ends there because cable modems are practically an order of magnitude more complicated than their telephone counterparts. Cable modems can be part modem, part tuner, part encryption/decryption device, part bridge, part router, part network interface card, part SNMP agent, and part Ethernet hub. Typically, a cable modem sends and receives data in two slightly different fashions. In the downstream direction, the digital data is modulated and then placed on a typical 6 MHz television channel, somewhere between 50 MHz and 750 MHz. Currently, 64 QAM is the preffered downstream modulation technique, offering up to 27 Mbps per 6 MHz channel. This signal can be placed in a 6 MHz channel adjacent to TV signals on either side without disturbing the cable television video signals.
The upstream channel is more tricky. Typically, in a two-way activated cable network, the upstream (also known as the reverse path) is transmitted between 5 and 42 MHz.
This tends to be a noisy environment, with RF interference and impulse noise. Additionally, interference is easily introduced in the home, due to loose connectors or poor cabling. Since cable networks are tree and branch networks, all this noise gets added together as the signals travel upstream, combining and increasing. Due to this problem, most manufacturers use QPSK or a similar modulation scheme in the upstream direction, because QPSK is more robust scheme than higher order modulation techniques in a noisy environment. The drawback is that QPSK is "slower" than QAM.
My Take:
Boy, that's a lot of techno babble!
When you subscribe to cable internet access, the ISP is actually assigning you your very own CATV channel. Kinda. There are not enough "channels" in the CATV range for everyone. I am sure there are "neighborhood" multiplexers. Any Cable ISP employees out there to clarify?
The Sarge
USAF Tech Controller
Edited: Oops! 27Mbps per 6MHz channel...boy it would be nice to have my own individual CATV channel...they probably share the "analog bandwidth" of each channel (or use the extra for buffer) between users (1.5Mbps max?)
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Modulation and Demodulation is a general term.
For example, every cordless telephone Modulate our voice to the carrier signal (900MHz, or 2.4GHz) between the handset and the base, and Demodulate the voice of the person that talk to us. Yet, we don?t call a cordless Tel. a Modem, since we use the term Modem for the gizmo that connect us through the Tel. to the ISP.
Cable or DSL modems are modem in the sense that the Internet info rides on a signal that has to be demodulate for the Ethernet band.
For example, every cordless telephone Modulate our voice to the carrier signal (900MHz, or 2.4GHz) between the handset and the base, and Demodulate the voice of the person that talk to us. Yet, we don?t call a cordless Tel. a Modem, since we use the term Modem for the gizmo that connect us through the Tel. to the ISP.
Cable or DSL modems are modem in the sense that the Internet info rides on a signal that has to be demodulate for the Ethernet band.
The Sarge looks over the dead horse, and says "Heck, I need the exercise!"
That is correct. "Frequency Modulation" is placing an analog signal on a carrier frequency. (just like the cordless phone)
Cordless phones, even the "digital" ones, do not modulate an analog signal into a digital signal for transmission.
Modems convert analog data into digital data and vice versa. Hence, the reason we cannot really call a cordless phone a modem.
<< Cable or DSL modems are modem in the sense that the Internet info rides on a signal that has to be demodulate for the Ethernet band. >>
Everything coming out of your wall through that RG-59? cable is analog. RG-59 has the designation 10BROAD36. 10Mbps, Broadband (analog), 3600m max length. Ethernet cable, desgnated RJ-45, RJ-8, or RJ-58, etc., is Baseband medium. Fully digitial. No "band" or "frequency" at all. (100Mhz rating of some cable is the max clockspeed of the digital signal, not a carrier frequency).
The Sarge looks at the dead, beaten horse and wonders why splitting hairs is so important. It's isn't.
I guess I am venting my frustration on those who misuse terminology. I've done it. Everyone does it. It just seems, these days, everyone gives out advice and most of the uneducated still take it without question.
This not directed to JackMDS, spidey07, or MJT2k. It is mainly directed to a certain Circuit City staff I ran into today. Story will be posted to the relevant board shortly.
I can't keep count of the people who think the cable coming out of the wall is digital and that $300 cable modem is a RG-58 to RJ45 "converter". Maybe I am just waaaaay wrong. It's been known to happen.
The Sarge
USAF Tech Controller
That is correct. "Frequency Modulation" is placing an analog signal on a carrier frequency. (just like the cordless phone)
Cordless phones, even the "digital" ones, do not modulate an analog signal into a digital signal for transmission.
Modems convert analog data into digital data and vice versa. Hence, the reason we cannot really call a cordless phone a modem.
<< Cable or DSL modems are modem in the sense that the Internet info rides on a signal that has to be demodulate for the Ethernet band. >>
Everything coming out of your wall through that RG-59? cable is analog. RG-59 has the designation 10BROAD36. 10Mbps, Broadband (analog), 3600m max length. Ethernet cable, desgnated RJ-45, RJ-8, or RJ-58, etc., is Baseband medium. Fully digitial. No "band" or "frequency" at all. (100Mhz rating of some cable is the max clockspeed of the digital signal, not a carrier frequency).
The Sarge looks at the dead, beaten horse and wonders why splitting hairs is so important. It's isn't.
I guess I am venting my frustration on those who misuse terminology. I've done it. Everyone does it. It just seems, these days, everyone gives out advice and most of the uneducated still take it without question.
This not directed to JackMDS, spidey07, or MJT2k. It is mainly directed to a certain Circuit City staff I ran into today. Story will be posted to the relevant board shortly.
I can't keep count of the people who think the cable coming out of the wall is digital and that $300 cable modem is a RG-58 to RJ45 "converter". Maybe I am just waaaaay wrong. It's been known to happen.
The Sarge
USAF Tech Controller
- Oct 25, 1999
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Digital (like Digital Phone) does not preclude Modulation. Audio is still 20HZ-20KHz, digital or not.
Digital transmission relates to the change (hopping) in carrier frequency (the modulated wave), not to the original info, whether it is audio or 0 and 1 or any thing else.
Click here:
How Cable Modems Work
A Qoute form the above Link:
Modulator
In cable modems that use the cable system for upstream traffic, a modulator is used to convert the digital computer network data into radio-frequency signals for transmission. This component is sometimes called a burst modulator, because of the irregular nature of most traffic between a user and the Internet, and consists of three parts:
a section to insert information used for error correction on the receiving end
a QAM modulator
a digital to analog (D/A) converter
Demodulator
The most common demodulators have four functions. A quadrature amplitude modulation (QAM) demodulator takes a radio-frequency signal that has had information encoded in it by varying both the amplitude and phase of the wave, and turns it into a simple signal that can be processed by the analog to digital (A/D) converter. The A/D converter takes the signal, which varies in voltage, and turns it into a series of digital 1s and 0s. An error correction module then checks the received information against a known standard, so that problems in transmission can be found and fixed. In most cases, the network frames, or groups of data, are in MPEG format, so an MPEG synchronizer is used to make sure the data groups stay in line and in order.
Digital transmission relates to the change (hopping) in carrier frequency (the modulated wave), not to the original info, whether it is audio or 0 and 1 or any thing else.
Click here:
How Cable Modems Work
A Qoute form the above Link:
Modulator
In cable modems that use the cable system for upstream traffic, a modulator is used to convert the digital computer network data into radio-frequency signals for transmission. This component is sometimes called a burst modulator, because of the irregular nature of most traffic between a user and the Internet, and consists of three parts:
a section to insert information used for error correction on the receiving end
a QAM modulator
a digital to analog (D/A) converter
Demodulator
The most common demodulators have four functions. A quadrature amplitude modulation (QAM) demodulator takes a radio-frequency signal that has had information encoded in it by varying both the amplitude and phase of the wave, and turns it into a simple signal that can be processed by the analog to digital (A/D) converter. The A/D converter takes the signal, which varies in voltage, and turns it into a series of digital 1s and 0s. An error correction module then checks the received information against a known standard, so that problems in transmission can be found and fixed. In most cases, the network frames, or groups of data, are in MPEG format, so an MPEG synchronizer is used to make sure the data groups stay in line and in order.
SgtBuddy, Why isn't a cable modem a "bridge"?
Yes, I will admit I choose the "bridge" too quickly over "gateway" but a "gateway" only gets you to another type of transfer protocol (i.e. ATM). The "bridge" is there you just seem to be over looking it. Most, if not all, devices on the Internet connect via Ethernet to a "bridge" then to a "gateway", don't they? At least this is what I learned in school, I would post a link to provide a reference to it but it was not an "actual" class, it was a seminare taught buy a 20+ years network tech.
Yes, I will admit I choose the "bridge" too quickly over "gateway" but a "gateway" only gets you to another type of transfer protocol (i.e. ATM). The "bridge" is there you just seem to be over looking it. Most, if not all, devices on the Internet connect via Ethernet to a "bridge" then to a "gateway", don't they? At least this is what I learned in school, I would post a link to provide a reference to it but it was not an "actual" class, it was a seminare taught buy a 20+ years network tech.
Kudos JackMDS. You proved my point. A cable modem is a modem.
Not a Bridge (Connecting two LAN segments together)
Not a Gateway (Connecting two LANS of different protocols together)
Modems take an analog signal and "convert" it to digital and vice versa.
Hairs are getting kinda thin, don't think they can take any more splitting.
heh
The Sarge, always looking for a argument
PS: I could just be very misguided. I am not a total subject matter expert in this field. Most of the stuff I quote is off reliable web sources. I hope, one day, to have letters like CCIE and MSCE proceeding my name.
Not a Bridge (Connecting two LAN segments together)
Not a Gateway (Connecting two LANS of different protocols together)
Modems take an analog signal and "convert" it to digital and vice versa.
Hairs are getting kinda thin, don't think they can take any more splitting.
heh
The Sarge, always looking for a argument
PS: I could just be very misguided. I am not a total subject matter expert in this field. Most of the stuff I quote is off reliable web sources. I hope, one day, to have letters like CCIE and MSCE proceeding my name.
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