What is the difference between a Router and a Modem???

Routers and modems are two of the most common computer peripherals, yet many people don’t know the function of each one. While the two devices may look similar, they each serve a difference purpose. Fortunately, the functions of the two devices are pretty easy to understand.

Modem:

cisco_cable_modem

A modem is a device that provides access to the Internet.

The modem connects to your ISP, which typically provides either cable or DSL Internet service. Cable modems have a coaxial (or “coax”) connection, which is the same type of connector found on a TV or cable box. This connects to a cable port on the wall. DSL modems have a telephone connector, also called an RJ-11 jack, which connects to a telephone socket on the wall.

By connecting your modem to your router (instead of directly to a computer), all devices connected to the router can access the modem, and therefore, the Internet. The router provides a local IP address to each connected device, but they will all have the same external IP address, which is assigned by your ISP.

To summarize, the device connection order is outlined below:

  • PC or wireless device.

  • Router.

  • Modem.

  • ISP.

  • Internet.

While the router and modem are usually separate entities, in some cases, the modem and router may be combined into a single device. This type of hybrid device is sometimes offered by ISPs to simplify the setup process.

Modem (Modulator Demodulator) is a device that transmits a digital signal over an analog carrier. Its main purpose is modulation of an Analog Signal -> Digital Signal and vice-versa,

A router is a device that is used to connect networks with different subnets.

Now depending upon your own knowledge, you might/might not understand this, but the above two sentences sum up all of the story.

Gong with the ‘might not’ case, here is the full story.

Do you recall (regarding if you are old enough) that the only way to connect to the Internet was using a device installed into the bare-bone of your desktop? You had to connect a telephone wire to it and whenever you ‘dialed’ to the internet, it would make very annoying noises.

That device was a MODEM.

Everything that has a microprocessor in it is in fact digital. Hence when we want to access the internet, or any data in the globe we need to go digital. But since digital signals and analog signals are extremely different in nature, there has to exist a sort of a media converter.

I have to point out that media converter is actually a very incorrect term. I just used it so the purpose of the modem could be clarified. A modem is not a media converter. It is a modulation device, hence referred to as MODEM.

Regarding what is Modulation, it is a process by which a digital signal is super-imposed upon an analog carrier. This is done so that the digital signal would make it to the other side with minimal degradation.

A question arises that why just don’t we shove the digital signal into the wire and pray that it gets where it want to go? If you plan on living under 100 meters from the telephone exchange, then yes, why not…

Since this is evidently not possible, and hence also the reason why modulation is required. Modulation makes it possible for the digital signal to go further.

Now that we have a modulated signal, how do we extract the digital signal from the modulated one? We use a demodulator.

Since internet communication is a very to and fro communication, we need a Modulator and a Demodulator incorporated into the same device so we can establish a proper and prolonged connection, hence MODEM.

Router: 

netgear_router

A router is a small box that allows multiple computers to join the same network.

While early routers provided several Ethernet ports for wired connections, most modern routers offer wireless connectivity as well. These “wireless routers” often have one or two moveable antennas on the sides, though some models house the antennas inside the enclosure. Wireless routers allow multiple computers and other devices, such as smartphones and tablets, to join the same network.

While connecting to a router provides access to a local network (LAN), it does not necessarily provide access to the Internet. In order for devices on the network to connect to the Internet, the router must be connected to a modem. Therefore, most routers have a specific Ethernet port that is designed to connect to the Ethernet port of a cable or DSL modem.

Regarding what is a ROUTER, as I mentioned earlier, it is used to connect different subnets.

Example:

IP Address: 192.168.1.0

Subnet Mask: 255.255.255.0

IP Address: 192.168.2.0

Subnet Mask: 255.255.255.0

In the above mentioned example, you don’t need to know much other than both IP Addresses are different. How different other than a difference of a 1 and a 2 in both IP Addresses, you ask?

Both are on different subnets, as defined by the Subnet Mask.

The IP Address 192.168.1.0 is the network ID. This subnet (according to the subnet mask 255.255.255.0) can support up to 254 hosts, ranging from 192.168.1.1 -> 192.168.1.254.

The IP Address 192.168.2.0 is the network ID. This subnet (according to the subnet mask 255.255.255.0) can support up to 254 hosts, ranging from 192.168.2.1 -> 192.168.2.254.

For any device on the 192.168.1.0 network to successfully establish communication with a device on a 192.168.2.0 network would need a ROUTER.

ROUTERS and MODEMS are also used concurrently. If you have two offices in different cities, you would use the MODEMS (one in every office) to create a link to the two offices and the communication inside the building/office would be taken care by the ROUTERS. The modems connect to the ISP and since the ISPs are connected, they form a link to both the modems, hence linking both offices.

It is a much simpler idea and a cost effective solution than laying a cable from one corner of the country to the other. Unless if you really want to…

In Short:

MODEM:

A modem is what is used to create a point to point link with your Internet Service provider over telephone lines to attain a Public (Internet Protocol) necessary to connect to internet. It modulates and demodulates the signal from pc over copper to your ISP. Modem works in layer2 of OSI Model i.e. DATA LINK LAYER and data is carried in form of frames. It has only 2 ports one for connecting to ISP (xDsl) other for connecting a computers or router. Only one Pc can connect to internet using only a modem, for further increasing the users routers came into picture that we all know these days as Wi-Fi Routers.

ROUTER:

A router works in Layer3 of the OSI model. Transmission form is packets(includes source Ip and destination Ip)In simple terms ,  and not going much deeper ,in home networks it used to increase the number of users connecting to internet which was not possible in case of modem. It performs NATTING (not explain in deep)which enables multiple users in Local Area Network (Home users, phones, laptops) to connect to internet using single Ip over Wi-Fi or even extra ports provided.

As NATTING is a feature of router and can be enabled in most of the modems these days so you will hear the term Router more often these days.

Concluding, The Router in our homes are performing both the functions of a ROUTER and a MODEM that is why most Users cannot differentiate.

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Information Brought To You By Biovolt Corporation.

 

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