What is a LAN network?

We explain what a LAN network is and the types of networks that exist. In addition, what is and how a router works. What is the Internet?

1. What is a LAN network?

It is known as LAN (acronym for  Local Area Network , which translates Local Area Network) to a computer network whose scope is limited to a reduced physical space , such as a house, an apartment or at most a building.

Through a LAN network,  resources can be shared between several computers and computing devices (such as cell phones, tablets, etc.), such as peripherals (printers, projectors, etc.), information stored on the server (or on connected computers) and even Internet access points, despite being in rooms or even different floors.

These types of networks are common and everyday use in businesses, companies and homes , and can present a different network topology according to the specific needs of the network, such as:

• Network and bus , in which the same cable (or  backbone ) connects to computers and allows the transmission of data in a straight line, making it simple but susceptible to cable damage or traffic disruption.
• Star network , in which all computers connect to a central server that manages network resources and allocates them as requested.
• Ring network , in which all computers are connected to their neighbors through a unidirectional transmission, which interrupts the network from having a fault at some level of it.
• Mixed network , combine two or more models of the above.

2. Types of networks

Computer networks are usually classified based on their physical or geographic reach, which generally reflects their power or volume of data . In that sense, we can talk about:

• LAN Networks  ( Local  Area  Network ) . Local area networks that cover specific and specific sites of little scope, such as a house, an office, at most some floors within a building. They are usual in business, schools, companies , etc.
• MAN Networks  ( Metropolitan Area  Network ) . Metropolitan area networks, that is, of a scope that is superior to the local but not international. A perfect example of these are the networks of university campuses, or bureaucratic management between various State agencies , each with their headquarters in various parts of the city . 
• WAN networks   ( Wide Area  Network ) . Wide area networks that cross vast regions of the geography, being able to be national or international, such as the Internet itself. 

3. What is a router?

Router  or router is called  a device that allows the interconnection of subnets , managing the way in which data packets are routed from one to another. This means that the router, as its name implies, gets sent packets a suitable path, analyzing its source and destination information. This function is carried out through two simultaneous processes:

• Package forwarding . The router receives packets and sends them back to the appropriate exit point as determined by the routing table, an electronic document that contains the routes to the different nodes of the network.
• Package routing . Using routing algorithms, it determines the route that packets must follow as they flow from a sender to a receiver.

4. Internet

The Internet is called a Wan network  composed of a specialized set of interconnected computer networks through the TCP / IP family of protocols , thus achieving a global and massive reach.

This network dates from the mid-twentieth century, when ARPANET was established, a precursor that encompassed only three American universities in the state of California, but has since grown steeply to become the network of networks, the most important known.

Among its services, the best known (so much so that they are confused as one thing) is the World Wide Web ( WWW ): a set of protocols that allow remote consultation of hypertexts and thus share tons of remote information. This service was created in 1990, and it is not the only one that the Internet is currently able to sustain.

Building a network

There are ways to classify a network. The main classification criterion is considered to be the method of administration. That is, depending on how the network is organized and how it is managed, it can be classified as a local, distributed, urban or global network. It manages the network or its segment the network administrator . In the case of complex networks, their rights and responsibilities are strictly allocated, documentation and logging of the actions of the team of administrators are kept.

Computers can be connected to each other using various access media: copper conductors ( twisted pair ), optical conductors ( optical cables ) and through a radio channel (wireless technologies). Wired, optical communications are established via Ethernet and other means. A separate local area network can be connected to other local area networks through gateways, and also be part of a global computer network (for example, the Internet ) or have a connection to it.

Most often, local networks are built on Ethernet technologies . It should be noted that the Frame Relay and Token ring protocols were previously used , which today are less common, they can be seen only in specialized laboratories, educational institutions and services. To build a simple local area network, routers , switches , wireless access points, wireless routers, modems, and network adapters are used. Less commonly used are media converters (converters), signal amplifiers (repeaters of various kinds) and special antennas.

Routing in local networks is used primitive, if it is needed at all. Most often it is static or dynamic routing (based on the RIP protocol ).

Sometimes workgroups are organized on a local network  – a formal unification of several computers into a group with a single name.

Network administrator  – a person responsible for the operation of a local network or part of it. His responsibilities include providing and monitoring physical communications, setting up active equipment, setting up general access and a predefined range of programs that ensure stable network operation.

Technologies of local area networks, as a rule, implement the functions of only two lower layers of the OSI model  – physical and channel. The functionality of these layers is sufficient to deliver frames within the standard topologies that LAN supports: star, bus, ring, and tree. However, this does not mean that computers connected to a local network do not support protocols of levels located above the channel level. These protocols are also installed and run on local network nodes, but the functions they perform are not related to LAN technology.

Addressing (Network)

In local networks based on the IPv4 protocol , special addresses assigned by the IANA ( RFC 1918 and RFC 1597 standards ) can be used :

• 10.0.0.0-10.255.255.255;
• 172.16.0.0-172.31.255.255;
• 192.168.0.0—192.168.255.255.

Such addresses are called private , internal , local, or “gray” ; these addresses are not accessible from the Internet. The need to use such addresses arose due to the fact that the development of the IP protocol did not envisage such a wide distribution, and gradually there were not enough addresses. To solve this problem, the IPv6 protocol was developed , but it is still not very popular. In various non-overlapping local networks, addresses can be repeated, and this is not a problem, since access to other networks occurs using technologies that replace or hide the address of an internal network node outside of it – NAT or proxymake it possible to connect a LAN to a wide area network (WAN). To ensure the connection of local networks with global networks, routers are used (in the role of gateways and firewalls ).

An IP address conflict is a common situation in a network in which two or more computers with the same IP addresses end up on the same IP subnet. To prevent such situations and to ease the work of network administrators, DHCP is used , which allows computers to automatically obtain the IP address and other parameters required to operate on a TCP / IP network .

LAN and VPN Network

Communication with a remote local area network connected to the global network from home / business trip / remote office is often realized via VPN . This establishes a VPN connection to the border router.

The following method of organizing remote access to a local network is especially popular:

1. A connection is provided externally to the router, for example via PPPoE , PPTP or L2TP (PPTP + IPSec).
2. Since these protocols use PPP , it is possible to assign an IP address to the subscriber. A free (unoccupied) IP address is assigned from the local network.
3. The router (VPN, Dial-in server) adds a proxyarp  – an entry on the local network card for the IP address that it gave out to the VPN client. After that, if local computers try to access the issued address directly, then after an ARP request they will receive the MAC address of the server’s local network card, and the traffic will go to the server, and then to the VPN tunnel.

Differences between VLAN and VPN

Differences between VLAN and VPN: The goal is the same – the methods are different.

Historically, telecommunication technologies and local networks have evolved in their own independent ways. Therefore, the same problem of creating virtual connections (virtual networks) was actually solved in fundamentally different ways. Therefore (with some degree of convention), two ways can be distinguished:

• Local . It is built on the basis of switched What is Ethernet using virtual networks (VLAN setting Debian D-Link). The division occurs at the level of the switch, which has the ability to allocate one or more users at the data link level into a group according to some criteria (port or MAC address). That is, if there are several switches in the local network with support for the 802.1q standard, you can build a VLAN between them. Applies to LAN only .
• Telecommunication . It involves the creation of virtual channels (tunnels) “on top” of the transport protocol (usually IP or Ethernet). The client node, using its credentials, establishes a point-to-point connection with the access server, and through this newly formed channel it transmits / receives data. In this case, both the authorization procedure and information exchange can be encrypted in whole or in part (only the authorization header and password). Used in WAN for communication between public IPs, can be used in LAN.