1.Background of Wi-Fi
1.1. Introduction
Its name comes from the Wi-Fi trademark. It is a mechanism for connecting electronic devices wirelessly. Wi-Fi enabled devices, such as a personal computer, video game console, smartphone, or digital audio player, can connect to the Internet through a wireless network access point.
Wi-Fi is a brand of the Wi-Fi Alliance, the commercial organization that adopts, tests and certifies that the equipment complies with the 802.11 standards related to wireless local area networks.
1.2 History
The history of the origin and development of this wireless technology dates back to the year 1880 when Alexander Graham Bell and Charles Summer Tainter invented the photophone, the first device for transmitting sound through light without using cables, just 8 years later the German physicist Rudolf Hertz used radio waves to make the first wireless communication.
In 1971 a group of American researchers designed the first wireless local area network baptizing it with the name of ALOHAnet, this first WLAN used radio waves to communicate with various computers located on the different islands of Hawaii.
The foundations of current Wi-Fi date back to 1985 when the United States Communications Commission established the characteristics that a wireless network had to have by assigning the frequencies in which this technology works known as ISM bands (Industrial, Scientific, Medical) destined to the use in wireless networks in the industrial, scientific and medical fields.
In 1991 the North American companies AT&T and NCR developed the bases of the 802.11 standard that establishes the regulations in wireless communication, at this time the transmission speeds were really low in the order of 5 Mb / s until in 1993 the Engineer Jhon O'Sullivan developed a technology for the astrophysical sector that was implemented in wireless networks, allowing efficient transmission speeds to be achieved.
In 1997 the 802.11 standard was launched by the IEEE (Institute of Electrical and Electronic Engineers). Later in 1999 several companies such as the Finnish Nokia at that time a leading manufacturer of mobile phones and the American Symbol Technologies, specialist in the development of wireless solutions or the specialist in semiconductor manufacturing Intersil, among others, created the non-profit association WECA with The purpose of promoting the development of electronic devices that are compatible with the IEEE 802.11 standard, later in 2003 it was renamed the Wi-Fi Alliance.
1.3. The real name of Wi-Fi
In 2000, just one year after its formation, what was still called WECA accepted the IEEE 802.11b standard as a standard. The name was very uncommercial so the association hires the advertising company Interbrand to create a name that is much easier to remember, something short and simple. The proposals are several: "Prozac", "Compaq", "Oneworld", "Imation" and, obviously, "Wi-fi" short for Wíreles Fidelity.
Wi-Fi (802.11) was created to replace the physical and MAC layers of Ethernet (802.3).
In other words, Wi-Fi and Ethernet are the same networks that differ in the way the computer or terminal accesses the network, Ethernet through cable and Wi-Fi through electromagnetic waves. This feature makes them compatible.
It is important to note that Wi-Fi is not a brand, it is the name of a standard. This means that all computers with the Wi-Fi seal can work together regardless of the manufacturer that created the network or the computer. So if in an office we have computers of different brands but all of them have Wi-Fi, we can connect them with each other without problems.
Currently Wifi is, above all, known as a tool to access the Internet but the truth is that it was designed as a local wireless network, to connect several devices to each other at a short distance. This utility should not be forgotten, because although it is less widely used, it can provide the user with many facilities and possibilities.
1.4. The most popular Wi Fi
The original standard is 802.11, it has evolved and now the range and speed possibilities are various. Always talking about Wifi, some variants are these:
- IEEE 802.11b and IEEE 802.11g, both have a 2.4 GHz band, the first reaches a speed of 11 Mbps and the second of 54 Mbps. They are the most widespread standards which gives them great international acceptance.
- IEEE 802.11a, better known as Wifi5 because its band is 5 GHz, having a higher frequency than the previous standard also has a shorter range, approximately 10% less. On the other hand, being a fairly new system there are still no other technologies that use it, so the Internet connection from the computer is very clean and without interference.
- IEEE 802.11n, it works also at 2.4 GHz but the speed is much higher than its predecessors, 108Mbps.
1.5.Types of wireless networks.
The types of wireless networks depend on their range and the type of electromagnetic wave used. Depending on their size, we find the following networks, from smallest to largest range:
- WPAN (Wireless Personal Area Network): This type of network is used with technologies such as HomeRF, Bluetooth, ZigBee and RFID . It is a personal network with little reach, the technologies that use it can connect mobile phones in the house and computers through a central device. It is also used in the home as it needs secure communications with low data transmission rates and low consumption.
- WLAN (Wireless Local Area Network): In local area networks we can find wireless technologies based on HiperLAN (High Performance Radio LAN), or technologies based on Wi-Fi (Wireless-Fidelity).
- WMAN (Wireless Metropolitan Area Network, Wireless MAN): The most popular technology used by this network is WiMax (Worldwide Interoperability for Microwave Access), a wireless communication standard based on the IEEE 802.16 standard. It is very similar to Wi-Fi , but it has more coverage and bandwidth. Another example is LMDS (Local Multipoint Distribution Service).
- WWAN (Wireless Wide Area Network, Wireless WAN): It is the network used for second and third generation mobile phones (UMTS) and for GPRS (digital technology) mobile phones.
1.6 The possible wave types are:
- Radio waves: They are omnidirectional, it does not need parabolic and it is not sensitive to climatic changes such as rain. There are several types of band, it can be transmitted with a frequency of 3 to 30 Hz and a maximum of 300 to 3000 MHz.
- Terrestrial microwaves: The parabolic antennas send the information, it reaches kilometers but the transmitter and receiver must be perfectly aligned. Their frequency is from 1 to 300 Ghz.
- Satellite microwave: The information is forwarded from a satellite, it is one of the most flexible waves but it is easy to be interfered with.
- Infrared: They must be directly aligned, do not go through walls and have a frequency of 300 GHz to 384 THz.
1.7. Advantages and disadvantages of wireless networks
The main advantage is practically a no-brainer, mobility. But it implies more than the simple fact of being able to access the Internet from the sofa or the desk are complications.
Historic buildings that do not allow the installation of cable or places that are too wide such as industrial warehouses where wiring is unfeasible, are a good example of how this type of network can be made essential.
On the other hand, access to the network is simultaneous and fast. At a technical level, it must be said that the relocation of terminals is simple and, consequently, their installation is fast. The main disadvantage is the loss of transmission speed with respect to the cable and possible interferences in space.
In addition, being an open network it can cause security problems, although more and more users have information and protection mechanisms such as the traditional and efficient password. In the 90s, even the health of this network was doubted, a theory that has been refuted today.
So far we have talked about the advantages and disadvantages of wireless networks at the local level. The disadvantages arise when comparing the capacity of the cable with that of LAN (popularly Wi-Fi). But as we pointed out before, there are more types of wireless networks, some of them with large ranges that make kilometer connections possible.
In this case there is no possible comparison with the cable, they are pioneers and have opened up great possibilities. A clear example is found in the great evolution of mobile phones in recent years or in the possibilities of satellites.
Each type of wireless network has its own capabilities and limitations that make it tailored to the needs of the user. Undoubtedly, it is a technology still with deficiencies that will be corrected in its evolutionary process, still leaving us with great surprises.
2. Wifi networks
A Wi-Fi network is a data communications network and, therefore, allows you to connect servers, PCs, printers, etc., with the particularity of reaching it without the need for cabling.
In a purist way, it is worth saying that the acronym Wi-Fi (Wireless Fidelity) is used to identify products that incorporate any variety of wireless technology from the IEEE 802.11 standards, which allow the creation of known wireless local area networks such as WLAN4, and that they are fully compatible with those of any other manufacturer that uses these standards.
The general operating characteristics of a Wi-Fi network are the same as those of a wired network. The peculiarity is that Wi-Fi uses the air as the transmission medium.
The basic components of a Wi-Fi network are:
- The access point (AP): is the junction between the wired networks and the Wi-Fi network, or between various areas covered by Wi-Fi networks, which then acts as a repeater of the signal between these areas (cells). or more antennas connected to the access point A Wi-Fi terminal. This can be in the form of an external Wi-Fi device, which is installed on the user's PC, or it can be already integrated, as is usually the case with laptops. Additionally, you can find other terminals with communication capacity, such as electronic agendas (PDAs) and mobile phones, which have accessories (internal or external) to connect to Wi-Fi networks.
2.1. Wi-Fi network architecture
Wireless networks were originally conceived for the creation of corporate local area networks. The architecture of these is, therefore, quite simple. Over time, however, its use has evolved towards wide area networks, mainly in urban centers. This is due to the fact that the architecture, despite being simple, is very easily scalable.
2.1.1. Elements of a Wi-Fi network
The elements that make up a Wi-Fi network are the following:
- Access point (AP): It is the device that manages the transmitted information and makes it reach its destination. Likewise, it provides the link between the Wi-Fi network and the fixed network. Antenna: Antennas are the elements that send signals into the air in the form of electromagnetic waves that contain the information directed at the target device; and at the same time, they capture from the air the signals from which the information that comes from another device will be extracted. Each type of antenna has geometric properties that make it direct electromagnetic energy in certain directions in space.
Omnidirectional antennas emit in all directions while sectorial antennas or others of more directional still, such as parabolic antennas, progressively reduce the angular sector towards which they emit. By concentrating the energy sent (or captured), communications between antennas of greater distance can be obtained.
- External Wi-Fi device: The Wi-Fi card is a local area network card (CHAL) that complies with Wi-Fi certification and therefore allows the connection of a user terminal in an 802.11 network. There are different cards for each sub-standard (a, b or gr), but there are also mixed cards. These external devices can connect to PCI or PCMCIA slots or USB ports.
The main differences between this type of card and a conventional Ethernet card are the data encryption, the Wi-Fi network identifier (ESSID), the channel and the speed setting.
- User antenna and pigtail connector: The user antenna provides the necessary coverage to a user to access the Wi-Fi network. The pigtail connector is a type of cable that connects and adapts the user's Wi-Fi card and antenna.
Typology of a WiFi network
2.1.2. Topology of a Wi-Fi network
In Wi-Fi networks we can find two types of topologies:
Networks without infrastructure.
Wi-Fi networks without infrastructure do not need a fixed system that interconnects some elements of the architecture. They are networks that have not had significant commercial success. The most common examples that we can find are ad hoc nets, (or Peer-to-Peer) and fished / threshed nets or MESH, in English.
The former consist of a group of terminals that each communicate directly with the others through radio signals without using any access point. The terminals of this Wi-Fi network that want to communicate with each other have to use the same radio channel and configure a specific Wi-Fi identifier (named ESSI) in ad hoc mode.
Instead, MESH-type networks use access points that work with different frequency channels. On the one hand, they offer coverage to portable terminals, and on the other, they communicate with each other forming a fished / threshed net that allows them to cover large areas without the need for prior wiring.
Network in infrastructure mode.
An infrastructure mode network works using access points. It is more efficient than the ad hoc network, since this mode manages and transports each packet of information at its destination, improving the speed of the whole. In this operating mode, the network card is automatically configured to use the same radio channel used by the closest access point on the network. In an infrastructure mode network, access points can work as an interconnection between two networks. In this topology, there are two possibilities: the first is for the access point to act as an interconnection between the Wi-Fi network and another network over cables, such as a local area network, ADSL access, etc.The second scenario consists of the access point acting as an interconnection between two access points that give Wi-Fi access to users located in different areas.
2.1.3. Technological limitations of the 802.11 family (WI-FI)
Regardless of the frequency band in which they work, all the standards in the 802.11 subfamily share some limitations. These limitations are five:
- Range: Although commercially we typically speak of a range of up to 100 meters, this data depends, firstly, on the location and the presence of obstacles in the way between the access point and the terminal, and secondly, on weather conditions and interference. Band width: Nominally, the different standards can achieve, physically (that is, in the air channel, discounting any inefficiencies that the higher protocols may introduce), the speeds mentioned and presented by each sub-standards. However, due to the effect of the protocols necessary to transport user information on the air channel in order to use more robust encodings in the face of interference and / or errors, the useful speed is much lower. Quality of service: Not all traffic is equally important from the point of view of each user. Thus, it can be considered that a VoIP call should have priority over a file transfer. The most widespread Wi-Fi protocols, such as now b and g, do not include any mechanism to prioritize one type of traffic over another, which is very detrimental when traffic flows with very different requirements, such as voice and data, are mixed. Security:In the beginning, Wi-Fi networks did not have very sophisticated security mechanisms, since the emphasis was on how to transmit data over the air, which was a more urgent technological challenge. With the success of this technology, however, and the publication of the weaknesses of the original security mechanisms, it became necessary to introduce improvements in this aspect. Mobility:Wi-Fi networks are popularly considered to be mobile, since you don't have to connect from a fixed location to access the services it offers us. Strictly speaking, that is considered roaming, and not mobility. In fact, it is not possible to use a Wi-Fi network from a moving vehicle at normal speed, for physical reasons associated with speed. Furthermore, even when we move at low speed (walking), due to the limited coverage range of an access point, we quickly have to establish a connection with another access point, which means "jumping" from one to the other.
3. Protocols
The ' IEEE 802.11' standard defines the use of the two lower levels of the OSI architecture (physical and data link layers), specifying their performance standards in a WLAN. The 802.x branch protocols define the technology of local area networks and metropolitan area networks.
802.11 legacy
The original version of the IEEE (Institute of Electrical and Electronics Engineers) 802.11 standard published in 1997 specifies two theoretical transmission rates of 1 and 2 megabits per second (Mbit / s) that are transmitted by infrared (IR) signals. IR is still part of the standard, although there are no implementations available.
The original standard also defines the CSMA / CA (Carrier Sense Multiple Access Avoiding Collision) protocol as an access method. An important part of the theoretical transmission speed is used in the needs of this coding to improve the quality of the transmission under different environmental conditions, which resulted in interoperability difficulties between equipment of different brands. These and other weaknesses were corrected in the 802.11b standard, which was the first of this family to achieve wide acceptance among consumers.
802.11a
The 802.11a revision was approved in 1999. The 802.11a standard uses the same set of base protocols as the original standard, operates in the 5 GHz band and uses 52 orthogonal frequency-division multiplexing (OFDM) subcarriers with a maximum speed of 54 Mbit / s, which makes it a practical standard for wireless networks with actual speeds of approximately 20 Mbit / s. The data rate is reduced to 48, 36, 24, 18, 12, 9 or 6 Mbit / s if necessary. 802.11a has 12 channels without a lapel, 8 for wireless and 4 for point-to-point connections. It cannot interoperate with 802.11b standard equipment, unless you have equipment that implements both standards.
802.11b
The 802.11b revision of the original standard was ratified in 1999. 802.11b has a maximum transmission speed of 11 Mbps and uses the same access method defined in the original CSMA / CA standard. The 802.11b standard works in the 2.4 GHz band. Due to the space occupied by the coding of the CSMA / CA protocol, in practice, the maximum transmission speed with this standard is approximately 5.9 Mbit / s over TCP. and 7.1 Mbit / s over UDP.
802.11e
The IEEE 802.11e specification offers a wireless standard that allows interoperation between public, business and residential user environments, with the added ability to meet the needs of each industry. Unlike other wireless connectivity initiatives, this can be considered as one of the first wireless standards to work in home and business environments. The specification adds, with respect to the 802.11b and 802.11a standards, QoS features and multimedia support, while maintaining compatibility with them. These capabilities are essential for home networks and for operators and service providers to build advanced offerings. The document that establishes the QoS guidelines, approved last November,defines the first indications about what the specification will be like that will appear at the end of 2001. It also includes error correction (FEC) and covers the audio and video adaptation interfaces in order to improve the control and integration in layers of those mechanisms who are in charge of managing lower-ranking networks. The centralized management system integrated into QoS avoids collisions and bottlenecks, improving the ability to deliver time-critical loads. These guidelines have not yet been approved. With the 802.11 standard, IEEE 802.11 technology supports real-time traffic in all kinds of environments and situations. Real-time applications are now a reality because of the Quality of Service (QoS) guarantees provided by 802.11e. The goal of the new 802 standard.11e is to introduce new mechanisms at the MAC layer level to support services that require Quality of Service guarantees. To meet its objective IEEE 802.11e introduces a new element called Hybrid Coordination Function (HCF) with two types of access:
(EDCA) Enhanced Distributed Channel Access, equivalent to DCF.
(HCCA) HCF Controlled Access, equivalent to PCF.
In this new standard, four categories of access to the medium are defined (ordered from least to most priority).
- Background (AC_BK) Best Effort (AC_BE) Video (AC_VI) Voice (AC_VO)
To achieve traffic differentiation, different media access times and different sizes of the contention window are defined for each of the categories.
802.11g
In June 2003, a third modulation standard was ratified: 802.11g, which is the evolution of 802.11b. This uses the 2.4 Ghz band (like 802.11b) but operates at a theoretical maximum speed of 54 Mbit / s, which on average is 22.0 Mbit / s of real transfer speed, similar to that of the 802.11a standard. It is compatible with the b standard and uses the same frequencies. A good part of the design process for the new standard was taken by making both models compatible. However, in networks under the g standard, the presence of nodes under the b standard significantly reduces the transmission speed.
The equipment that works under the 802.11g standard reached the market very quickly, even before its ratification, which was given approx. on June 20, 2003. This was partly due to the fact that to build equipment under this new standard, those already designed for the b standard could be adapted.
Currently equipment with this specification is sold, with powers of up to half a watt, which allows communications of more than 50 km with parabolic antennas or appropriate radio equipment.
There is a variant called 802.11g + capable of reaching 108Mbps transfer rate. Generally, it only works on computers from the same manufacturer as it uses proprietary protocols.
802.11g and 802.11b interaction.
802.11g has the advantage of being able to coexist with the 802.11a and 802.11b standards, this because it can operate with RF DSSS and OFDM technologies. However, if it is used to implement users that work with the 802.11b standard, the performance of the wireless cell will be affected by them, allowing only a transmission speed of 22 Mbps. This degradation is due to the fact that 802.11b clients do not comprise OFDM.
Assuming that you have an access point that works with 802.11g, and a client with 802.11b and another 802.11g are currently connected, as the 802.11b client does not understand the OFDM sending mechanisms, which is used by 802.11g, collisions will occur, which will cause the information to be forwarded, further degrading our bandwidth.
Assuming the 802.11b client is not currently connected, the Access Point sends frames that provide information about the Access Point and the wireless cell. Without the 802.11b client, the frames would display the following information:
NON_ERP present: no
Use Protection: no
ERP (Extended Rate Physical), this refers to devices that use extended data transfer rates, in other words, NON_ERP refers to 802.11b. If they were ERP, they would support the high transfer rates that 802.11g supports.
When an 802.11b client associates with the AP (Access Point), the latter alerts the rest of the network about the presence of a NON_ERP client. Changing their frames as follows:
NON_ERP present: yes
Use Protection: yes
Now that the wireless cell knows about the 802.11b client, the way information is sent within the cell changes. Now when an 802.11g client wants to send a frame, it must first warn the 802.11b client by sending it an RTS (Request to Send) message at 802.11b speed so that the 802.11b client can understand it. The RTS message is sent in unicast form. The 802.11b receiver responds with a CTS (Clear to Send) message.
Now that the channel is free to send, the 802.11g client sends its information at speeds according to its standard. The 802.11b client perceives the information sent by the 802.11g client as noise.
The intervention of an 802.11b client in an 802.11g type network is not limited only to the cell of the Access Point in which it is connected, if it is working in an environment with multiple APs in Roaming, the APs in the If the 802.11b client is not connected, frames with the following information will be transmitted between them:
NON_ERP present: no
Use Protection: yes
The previous frame tells them that there is a NON_ERP client connected to one of the APs, however, having Roaming enabled, it is possible that this 802.11b client connects to any of them at any time, so they must use the mechanisms of security throughout the wireless network, thus degrading the performance of the entire cell. This is why clients should preferably connect using the 802.11g standard. Wi-Fi (802.11b / g)
802.11h
The 802.11h specification is a modification on the 802.11 standard for WLAN developed by IEEE (IEEE 802) LAN / MAN Standards Committee Working Group 11 and released in October 2003. 802.11h attempts to solve problems derived from the coexistence of 802.11 networks with Radar or Satellite systems.
The development of 802.11h follows some recommendations made by the ITU that were mainly motivated by the requirements that the European Radiocommunication Office (ERO) considered convenient to minimize the impact of opening the 5 GHz band, generally used by military systems, to ISM applications (ECC / DEC / (04) 08).
In order to respect these requirements, 802.11h provides 802.11a networks with the ability to dynamically manage both frequency and transmission power.
Dynamic Frequency Selection and Transmitter Power Control
DFS (Dynamic Frequency Selection) is a functionality required by WLANs operating in the 5GHz band in order to avoid co-channel interference with radar systems and to ensure uniform use of available channels.
TPC (Transmitter Power Control) is a functionality required by WLANs that operate in the 5GHz band to ensure that the transmitted power limitations that may exist for different channels in a given region are respected, so that interference with systems is minimized. satellite.
802.11i
It is intended to overcome the current vulnerability in security for encryption and authentication protocols. The standard encompasses the 802.1x, TKIP (Integral - Secure - Temporary Key Protocol), and AES (Advanced Encryption Standard) protocols. It is implemented in WPA2.
802.11n
In January 2004, the IEEE announced the formation of an 802.11 (Tgn) working group to develop a new revision of the 802.11 standard. The actual transmission speed could be as high as 600 Mbps (which means that the theoretical transmission speeds would be even higher), and should be up to 10 times faster than a network under the 802.11a and 802.11g standards, and about 40 times faster faster than a network under the 802.11b standard. It is also expected that the scope of operation of the networks will be greater with this new standard thanks to MIMO technology.Multiple Input - Multiple Output, which allows to use several channels at the same time to send and receive data thanks to the incorporation of several antennas (3). There are also other alternative proposals that may be considered. The standard has already been written and has been in place since 2008. In early 2007 the second draft of the standard was approved. Previously, there were devices ahead of the protocol and unofficially offering this standard (with the promise of updates to meet the standard when the final one was implemented). It has suffered a series of delays and the last one takes it until November 2009. Project 7.0 having been approved in January 2009 and is on the right track to meet the designated dates. oneUnlike the other versions of Wi-Fi, 802.11n can work in two frequency bands: 2.4 GHz (which uses 802.11b and 802.11g) and 5 GHz (which uses 802.11a). As a result, 802.11n is compatible with devices based on all previous Wi-Fi editions. In addition, it is useful that it works in the 5 GHz band, since it is less congested and in 802.11n it allows to achieve a higher performance.
The 802.11n standard was ratified by the IEEE organization on September 11, 2009 with a speed of 600 Mbps in physical layer. 2 3
Currently most products are of the b or g specification, however the 802.11n standard has already been ratified, which raises the theoretical limit to 600 Mbps. Currently there are already several products that meet the N standard with a maximum of 600 Mbps (80-100 stable).
The 802.11n standard makes simultaneous use of both bands, 2.4 Ghz and 5 Ghz. Networks that work under the 802.11b and 802.11g standards, after the recent ratification of the standard, began to be manufactured in a massive way and is the subject of promotions by the different ISPs, so that the massification of said technology seems to be in road. All versions of 802.11xx, provide the advantage of being compatible with each other, so that the user will not need anything more than their integrated Wi-Fi adapter, to be able to connect to the network.
Undoubtedly this is the main advantage that differentiates Wi-Fi from other proprietary technologies, such as LTE, UMTS and Wimax, the three mentioned technologies are only accessible to users by subscribing to the services of an operator that is authorized to use the radio spectrum., through a national concession.
Most of the manufacturers already incorporate 802.11n Wi-Fi equipment into their production lines, for this reason the ADSL offer is usually accompanied by 802.11n Wi-Fi, as a novelty in the home user market.
It is known that the future replacement standard for 802.11n will be 802.11ac with transfer rates above 1 Gb / s.
‣ The ISM (Industrial, Scientific and Medical) bands allow the use of the 2.4-2.5 GHz, 5.8 GHz portions, and many other frequencies (not used in Wi-Fi).
‣ The UNII (Unlicensed National Information Infrastructure) bands allow unlicensed use of other portions of the 5 GHz spectrum.
Most commercial wireless devices (cell phones, television, radio, etc.) use licensed radio frequencies. Large organizations pay high royalties for the right to use these frequencies.
WiFi uses portions of the spectrum that do not require a license.
MAC layer:
802.11-based WiFi uses CSMA-Carrier Sense Multiple Access- to avoid transmission collisions. Before a node can transmit, it must listen on the channel for possible transmissions from other radios. The node can only transmit when the channel is idle.
Other technologies (such as WiMAX, Nstreme, and AirMAX), instead use TDMA-Time Division Multiple Access- (Time Division Multiple Access). TDMA divides access to a given channel into multiple time slots, and assigns time slots to each node on the network. Each node transmits only in its time slot and in this way collisions are avoided.
Layer one
TCP / IP protocol stack
| 5 | Application |
|
| 4 | Transport |
|
| 3 | Internet |
|
| two | Data link |
|
| one | Physical |
WiFi devices must choose certain parameters before they can establish communication. These parameters must be properly configured in order to establish connectivity “at the layer one level”.
The physical layer in an Ethernet network is a cable. To establish the same level of connectivity in WiFi, certain parameters must be agreed. Obviously, all devices must share the same channel, or they could not even "hear" each other. The radio's operating mode must be chosen properly so that communication can take place. The name of the network (also called ESSID) must be the same for all the devices to be communicated. Any security mechanism must also be properly configured.
Channels in 802.11 (WiFi)
WiFi devices must use the same channel in order to communicate. They send and receive on the same channel, so only one device can transmit at any given time. This mode of transmission is called halfduplex.
In half-duplex communications only one device can be transmitting at any one time. This is not the case in Ethernet networks, where there may be the ability to transmit and receive simultaneously in what is known as full duplex for certain hardware configurations. As we will see, this becomes a very important aspect in long distance wireless networks.
Wi-Fi channels
Channels without overlap: 1, 6, 11
Channels without overlap
The channels are separated every 5 MHz, but the 802.11 signals occupy 22 MHz. To avoid interferences, channels should be chosen that do not overlap, that is, the respective signals do not overlap in any part of the spectrum.
4. Wi-fi security
One of the problems that wi-fi technology currently faces is the progressive saturation of the radioelectric spectrum, due to the overcrowding of users, this especially affects long distance connections (greater than 100 meters). In reality, the Wi-Fi standard is designed to connect computers to the network at short distances, any use of greater range is exposed to an excessive risk of interference.
A very high percentage of networks are installed without taking security into account, thus turning their networks into open networks (or completely vulnerable to the attempt to access them by third parties), without protecting the information that circulates through them. In fact, the default configuration of many Wi-Fi devices is very insecure (routers, for example) since the device's key can be known from the device identifier; and therefore accessing and controlling the device can be achieved in just a few seconds.
Unauthorized access to a Wi-Fi device is very dangerous for the owner for several reasons. The most obvious is that they can use the connection. But also, by accessing the Wi-Fi, you can monitor and record all the information transmitted through it (including personal information, passwords….). The way to make it safe is to follow some tips:
- Frequent changes of the access password, using different characters, lowercase, uppercase and numbers. The default SSID (network name) must be modified. Perform the deactivation of the broadcasting SSID and DHCP. Configure the devices connected with their IP (indicate specifically which devices are authorized to connect) Use encryption: WPA2 Filter connected devices by MAC address Turn off Wi-Fi if you are not going to use it, the last recommendation is common sense: if you are not going to connect to your network through a Wi-Fi connection, disable that functionality on your router. A wired network is more secure, faster, and more reliable than a wireless one. And if you are going to be away from home for a long period, turn off the router. We still have no news of anyone successfully hacking into a powered down router.
There are several alternatives to guarantee the security of these networks. The most common are the use of data encryption protocols for Wi-Fi standards such as WEP, WPA, or WPA2 that are responsible for encoding the transmitted information to protect its confidentiality, provided by the wireless devices themselves. Most forms of are as follows:
- IPSEC (IP tunnels) in the case of VPNs and the IEEE 802.1X set of standards, which allows user authentication and authorization. MAC filtering, so that only authorized devices are allowed access to the network. It is the most recommended if it is only going to be used with the same computers, and if there are few. Hiding the access point: the access point (router) can be hidden so that it is invisible to other users.
There are also keys (passwords) of the following types:
- WEP encrypts the data on your network so that only the intended recipient can access it. 64-bit and 128-bit encryption are two levels of WEP security. WEP encrypts data using an encryption "key" before sending it over the air. This type of encryption is not recommended due to the great vulnerabilities it presents and that any cracker can get the key, even if it is well configured and the key used is complex. WPA: presents improvements such as dynamic generation of the access key. Keys are entered as alphanumeric digits. The security protocol called WPA2(11i standard), which is an improvement relative to WPA. In principle it is the safest security protocol for Wi-Fi at the moment. However they require compatible hardware and software, as the old ones are not.
The security of a Wi-Fi network can be tested by means of a Wi-Fi audit, however, there is no totally reliable alternative, since all of them are susceptible to being compromised.
Let's take a closer look at the security level of the encryption methods used by today's Wi-Fi solutions.
RIP WEP
WEP (Wired Equivalent Privacy) was the first encryption protocol introduced in the first IEEE 802.11 standard back in 1999. It is based on the RC4 encryption algorithm, with a secret key of 40 or 104 bits, combined with an Initialization Vector (IV) of 24 bits to encrypt the text message M and its checksum - the ICV (Integrity Check Value). The encrypted message C was determined using the following formula:
C = +
Where - is a concatenation operator and + is an XOR operator. Clearly, the initialization vector is the key to WEP security, so to maintain a decent level of security and minimize broadcasting, the IV must be applied to each packet, so that subsequent packets are encrypted with different keys. Unfortunately for WEP security, the IV is transmitted in plain text, and the 802.11 standard does not force the increase of the IV, leaving this security measure as a possible option for a particular wireless terminal (access point or wireless card).
| Date | Description |
| September 1995 | Potential RC4 vulnerability (Wagner) |
| October 2000 | First post on WEP weaknesses: Insecure for any key size; WEP encapsulation analysis (Walker) |
| May 2001 | Attack against WEP / WEP2 by Arbaugh |
| July 2001 | CRC bit flipping attack - Intercepting Mobile Communications: The Insecurity of 802.11 (Borisov, Goldberg, Wagner) |
| August 2001 | FMS attacks - Weaknesses in RC4's programming algorithm (Fluhrer, Mantin, Shamir) |
| August 2001 | AirSnort Post |
| February 2002 | FMS attacks optimized by h1kari |
| August 2004 | KoreK Attacks (Unique IVs) - Chopchop and Chopper Post |
| July / August 2004 | Publication of Aircrack (Devine) and WepLab (Sánchez), putting KoreK attacks into practice. |
LEARN HOW TO USE SECURITY AUDIT TOOLS
In his "The Art of War", the sage Sun Tzu said that to win you have to know your enemy and know yourself. It is a principle that also applies to the art of computer security: to prevent someone from overcoming your network defenses, you have to know what tools are used to hack WiFi networks…
pulWiFi is a powerful auditing tool for Android - Pull WiFi
The only way to know if your security settings are strong is to use them against your WiFi network and see if you can get in.
SOME TOOLS FOR SECURITY AUDIT ARE:
- Network Inventory Advisor. Search remotely for data on CPU, memory, system, peripheral devices, or other hardware details. Spanish Steganos Online Shield VPN. Free VPN connection. Anti hacker protection, access to blocked content and maximum anonymity on the web and social networks. Spanish Aircrack 1.2. Find out the WEP / WPA key of any WiFi network. English. Wifislax 4.3. The LiveCD distro for auditing WiFi networks. Spanish SWifi Keygen 0.6.2. Is the key of your WiFi network secure? Spanish. WPAMagickey for Windows 0.2.1. Calculate the key of WiFi networks protected by WPA. Spanish. WiFi password revealer 1.0.0.4.Recover your WiFi password in case of loss. English. Wifiway 3.4. The LiveCD for auditing wireless networks. Spanish. Beini 1.2.5. Recover WEP and WPA keys with this mini-distro. Spanish. CommView for WiFi 6.3. Capture packets from wireless connections. Spanish. Xiaopan OS 0.4.7.2. Audit and recover WPA and WEP WiFi keys. Spanish. AirSnare 1.5. The WiFi Intruder Detector. English.
BIBLIOGRAPHY
- http://www.portalprogramas.com/milbits/informatica/consejos-para-seguridad-en-redes-wi-fi.htmlhttp://www.ibersystems.es/blogredesinalambricas/consejos-para-estar-mas-seguro- en-una-red-wifi-gratis / http: //articulos.softonic.com/wifi-consejos-seguridadhttp: //www.pdaexpertos.com/Tutoriales/Comunicaciones/Seguridad_en_redes_inalambricas_WiFi.shtmlhttp: //www.softonic.com/ windows / auditoriahttp: //www.quees.info/que-es-wifi.htmlhttp: //www.maestrosdelweb.com/evolucion-de-las-redes-inalambricas
