After the tutorial I made, there were many questions and questions about the wireless network. Let's illustrate things.
The wireless network is nothing more than a similar network to network with cables using HUB, only without wires. There are people who can criticize me saying that this is not true, however, this is true.
The wireless network can be intercepted as well as a package that runs through HUB can be intercepted by any computer connected to the network because the hub simply serves to forward the packets to all computers on the network, and wireless network makes it by air, not targeting just the packages respectively for their fate, since scarcely knows where they are, because they are being sent by a radio frequency bands ranging from 2.4 GHz and / or 5.4 Ghz.
Various patterns, among them the common ones are:
802.11aWorks with 5.4 GHz speed of up to 54 Mbps. It was one of the standards used by fewer countries that have not allowed the use of the radio band at 5.4 GHz, and long after the 802.11be/ou of today, there are still places like the United States, which still is not allowed use components in the range of 5.47 to 5.725 GHz.
802.11bUses the frequency of 2.4 GHz with connection speeds of up to 11 Mbps. One of the first standards to be introduced and which was widely used early on not only for home connections, but also for Internet radio site, with operators who install antennas with amplifiers for receiving and sending special radio signal from the antenna (in a visible area) of the ISP. The major disadvantage of this pattern is that the frequency of 2.4 GHz is widely used by cordless phones, cellular phones, microwave, as well as base stations nearby can interfere and end up affecting the efficiency of the wireless network.
802.11gWith improvements, this pattern works on the same frequency, but gets up to 54 Mbps speed. The improvements were in error detection, signal loss, as well as check for mirroring the signal as interference from walls that can reflect the signal (due to some metal part), among others, best known today.
802.11nA new standard initiated by Intel and other companies like Apple, for maximixar use of the band at 2.4 GHz and 5.4 GHz to get the maximum speed possible with multiple antennas instead of only 1 previous standards, with simultaneous connections rather than only a single connection to the theoretical speed of up to 150 Mbps. Best Access Point and / or routers in this pattern with at least 2 or 3 antennas so that there is capacity for simultaneous connections without interference from one channel and another simultaneously. Having had much time to become a standard in the market, Apple released a lot of equipment called "draft n" or "draft" 802.11n, and then, who bought equipment this season, may have difficulties in using the network with its 150 Mbps offered. The first standards offered 4 simultaneous connections reaching the incredible 600 Mbps, but it should install the wireless network card with 4 antennas, each for each separate channel, with an unnecessary waste of electricity, especially in notebooks. Who bought versions "draft", can connect to networks typically a / b / g.
Access PointDevice used to spread the wireless network. In an infrastructure wireless network in a company, he is responsible to receive the signal from another nearby AP by increasing the gain to establish a reliable link between them, keeping customers connected as if in a single network (and is a single network with one SSID and BSSID).
SSIDIdentifiers of Wireless Networks Through him we can see the names of the networks in the program manager of wireless networks. There is a BSSID associated with this name, which is a form of address as a MAC address type, but only to identify if there are two or more networks with the same name.
Ad-Hoc
Contrary to what many think, you can create a network point to point as quickly as sending a file via Bluetooth to a cell to another. In Bluetooth, you check the name of another person's cell, depending on the case has to make the pairing even putting in an access code and the other. The wireless network also, you create a wireless network, branded as Ad-Hoc and puts an SSID of your choice. When you save your changes, on the other computer, just search the net, and this, if the wireless network adapters are working, will appear as if by magic. Simply enter the network, and if you have not configured any IP address or on a computer or another, wait 2 minutes at most to have Windows automatically assign a private address. By assigning this automatic address that will be similar to "169.254.3.69", you can use the "My Network places" to go through the other computer to share files (where there are shared folders and permissions in the firewall for this, which usually for safety, are not enabled by default in Windows XP for example).
Type Ad Hoc Networks - Point to Point
InfrastructureIs the wireless network consists of routers, Access Point (AP) and other network devices. In some places in large companies, installing a wireless network throughout the building, is the same as saying: "Installing a wireless network on each floor," since the wireless signal has trouble going through places like concrete ( as the floor or ceiling) or places with metal parts.
The solution is to place an AP on each floor, and link them through a cable or backbone network with sufficient bandwidth to support all the AP with the number of users of the entire floor of the building.
Each AP can support on average 60 users connected, which may vary for more or less depending on the type purchased as well as the AP frequency for which he works. A building with 10 floors, there may be up to 600 users connected to, say, 54 Mbps, which would total a total of 31 Gbps. Absurd? Maybe not, or maybe yes, but there is also the issue of AP that support 60 users with the minimum speed, which is 1 Mbps or less, which would have 600 Mbps connection to all the infrastructure, so in this case a 1 Gbps connection between the AP of the building, it is inevitable that there be no bottlenecks in the wired network (if wired in, what would the wireless then?).
Security in WirelessSecurity is a complicated issue until there are now several programs that discover passwords, such as aircrack-ng, which is even a Linux distribution which can be used in a Live CD to boot the machine just for search tasks and networks their passwords. There are several tools in this kit, wireless networks, such as, eg, an application that simulates the disconnection of the AP to the client, and how the data are trafficked through the air, as if on a hub, where all the computers on the network listen each other, the wireless network is the same, then the client reconnects to the AP, carries the authentication password with the SSID, and the latter being unprotected, aircrack-ng shows the results in hexadecimal characters.
There omidirecionais antennas and directional antennas. With the omi-directional antenna (that came with the AP or router by default), sends to all angles without having a correct direction, but she has an oval shape as a disc, and it is important to always leave the antenna AP standing of computers and satellite lines (lying) to the frequencies intersect in the air and one can listen to each other.
Practical example of a wireless network with omi-directional antenna (for all sides horizontally, but vertically flattened).
Directional antennas, make all the wifi signal strength is directed to one place, then you can place the antenna on top of your desk and target only the place where you want to receive the wireless signal, and no neighbor will have access since the signal is not spread by any party.
