Differences between modem and router. what are they used for

In the world of networks, two are the sections that most often ring among users, but we really know what the differences are between modem and router. Well here we will see what each one is used for, how it works in a basic way and what we often call a 4G modem or Wi-Fi router.

Index of contents

What is a modem and where does it work?

Let's start first with the oldest gadget, one that ushered in the era of data exchange between computers and the rise of the Internet as we know it today, the modem.

The modem gets its name from the union of the words MOdulator / DEModulator. It is a device capable of converting digital signals to analog, a process called " modulation ", and is also capable of converting analog signals to digital, whose process is called " demodulation ".

A modem works in the first layer or physical layer of the OSI model, since it is a device that is simply dedicated to converting the signals that arrive or send it to the network. It translates them so that teams operating at the upper link and network layers can receive, switch and route the data to the appropriate place.

Although it is true that currently there are also modems of various types, their expansion took place in the era of the analog Internet when the network of networks operated through telephone installation. The real modems were devices only dedicated to converting the analog signal (waves) that came through the RJ11 cable to our home into a digital signal (zeros and ones) that our computer could “understand”.

The content of the message sent to the network is emitted through a carrier signal, modified in some way (frequency or phase) by the modulating signal so that it is unique compared to other signals that exist in the medium, cable or air. This is done by the modem. At the other end, there will be another modem that does the opposite process and demodulates the signal and extracts the data from the carrier. This is how an analog signal works.

Modem: what it is, how it works and a bit of history

4G modem and fiber modem

Something similar occurs with the rest of the Internet connections, although from the ADSL start-up instead of having an analog signal, we have a digital one, so the presence of a modem would not be necessary, making the router itself work.

But where we still need to perform a signal transformation is in the optical fiber and the wireless network.

• In the first case we speak of the fiber optic network as FTTH (Fiber To The Home), which reaches our home and must be converted from an optical signal (light pulses) to an electrical signal (ones and zeros) by a device called ONT, so that the router can then use it. When this function is integrated by a router, it is called a fiber modem / router. The same is true for signals from the mobile GSM network or LTE 4G and now 5G. These travel through the medium in the form of waves, and we must convert them to electrical signals using a modem.

So what do we use a router for?

Now it is time to define the other device involved to know the differences between modem and router.

A router or router works at layer 3 of the OSI model, that is, the network layer, which is in charge of identifying the packet routing and therefore joining between two or more networks. By this definition we will already have an idea of ​​what the router does, being the device that is capable of interconnecting the equipment or clients of an internal network to a data network.

The router is capable of creating an internal or private network in which one or more devices are connected to it with a perfectly defined topology. In it, each computer is identified by means of an IP address associated with its MAC address that the router itself assigns through DHCP or in a fixed manner, if we so wish.

This LAN network is isolated from the public network by an external IP address that the provider assigns to the router itself. So it will be this device that "decides" to let pass or not the packets that circulate through the network and that is that they are destined to some node of its internal network. This is done by temporarily storing the received packets or frames in a buffer, in which the source and destination information placed in the TCP header of the packet is processed. It has a routing table that stores the shortest path to send those packets. The process is carried out with the following logical architecture:

• Input and output ports: these ports are logical, and are responsible for connecting the network layer with the two lower layers of data link with the IP protocol and others, and the physics of the modem. Ports are assigned to different applications or roles, for example, Web, Print, VPN, P2P, etc. Switching input: Connects the input and output ports of the router. Routing processor: works with IP protocols and forwarding tables, managing routing within the internal network.

The Wi-Fi router and more functions in the OSI layers

Today, routers not only perform work at the network layer, but they are practically computers, with hardware consisting of a processor, memory and even a graphical interface with utilities.

One of them is Wi-Fi connectivity, they are capable of expanding the wired physical network to a wireless network. It not only allows connecting nodes by cables through RJ45 ports, but also by electromagnetic waves, normally at 2.4 or 5 GHz according to the IEEE 802.11 standard used. This network continues to be part of the LAN, with the nodes perfectly connected to each other regardless of their nature.

In addition to the Wi-Fi function, it has already been commented that many routers integrate the modem inside to do it all through a single computer, thus working in the first three OSI layers.

It also works at the highest OSI layer, the application layer, thanks to the internal utilities of its firmware, such as the ability to create VPN networks, print servers or even a file server via FTP or Samba. Being own functions of applications located in the application layer and presentation of information to the user that we install on servers under an operating system.

Conclusions on differences between modem and router

As we have seen, the differences between modem and router are very clear and patent just knowing a little what the layers of the OSI model consist of, that's why we leave a complete article explaining what this consists of.

Two, three or even four devices currently coexist on the routers, acting as a modem, router, switch or switch and even as a server for shared data applications or personal VPN networks. One of the devices that have marked a milestone in the era of networks and available to any user regardless of those provided by network providers that are fairly basic routers.

We leave you now with some tutorials related to networks:

If you have any questions about it or want to make any clarification on the subject, leave it to us in the comments.