msgid "" msgstr "" "Project-Id-Version: English (cnp3-ebook)\n" "Report-Msgid-Bugs-To: \n" "POT-Creation-Date: 2026-04-19 00:54+0200\n" "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n" "Last-Translator: FULL NAME \n" "Language-Team: English \n" "Language: en\n" "MIME-Version: 1.0\n" "Content-Type: text/plain; charset=UTF-8\n" "Content-Transfer-Encoding: 8bit\n" "Plural-Forms: nplurals=2; plural=n != 1;\n" "X-Generator: Weblate 5.14.3\n" #: ../../protocols/wifi.rst:5 #, read-only msgid "802.11 wireless networks" msgstr "802.11 wireless networks" #: ../../protocols/wifi.rst:7 #, read-only msgid "" "The radio spectrum is a limited resource that must be shared by everyone. " "During most of the twentieth century, governments and international " "organizations have regulated most of the radio spectrum. This regulation " "controls the utilization of the radio spectrum, in order to prevent " "interference among different users. A company that wants to use a frequency " "range in a given region must apply for a license from the regulator. Most " "regulators charge a fee for the utilization of the radio spectrum and some " "governments have encouraged competition among companies bidding for the same " "frequency to increase the license fees." msgstr "" "The radio spectrum is a limited resource that must be shared by everyone. " "During most of the twentieth century, governments and international " "organizations have regulated most of the radio spectrum. This regulation " "controls the utilization of the radio spectrum, in order to prevent " "interference among different users. A company that wants to use a frequency " "range in a given region must apply for a license from the regulator. Most " "regulators charge a fee for the utilization of the radio spectrum and some " "governments have encouraged competition among companies bidding for the same " "frequency to increase the license fees." #: ../../protocols/wifi.rst:9 #, read-only msgid "" "In the 1970s, after the first experiments with ALOHANet, interest in " "wireless networks grew. Many experiments were done on and outside the " "ARPANet. One of these experiments was the `first mobile phone `_ , which was " "developed and tested in 1973. This experimental mobile phone was the " "starting point for the first generation analog mobile phones. Given the " "growing demand for mobile phones, it was clear that the analog mobile phone " "technology was not sufficient to support a large number of users. To " "support more users and new services, researchers in several countries worked " "on the development of digital mobile telephones. In 1987, several European " "countries decided to develop the standards for a common cellular telephone " "system across Europe : the `Global System for Mobile Communications` (GSM). " "Since then, the standards have evolved and more than three billion users are " "connected to GSM networks today." msgstr "" "In the 1970s, after the first experiments with ALOHANet, interest in " "wireless networks grew. Many experiments were done on and outside the " "ARPANet. One of these experiments was the `first mobile phone `_ , which was " "developed and tested in 1973. This experimental mobile phone was the " "starting point for the first generation analog mobile phones. Given the " "growing demand for mobile phones, it was clear that the analog mobile phone " "technology was not sufficient to support a large number of users. To " "support more users and new services, researchers in several countries worked " "on the development of digital mobile telephones. In 1987, several European " "countries decided to develop the standards for a common cellular telephone " "system across Europe : the `Global System for Mobile Communications` (GSM). " "Since then, the standards have evolved and more than three billion users are " "connected to GSM networks today." #: ../../protocols/wifi.rst:13 #, read-only msgid "" "While most of the frequency ranges of the radio spectrum are reserved for " "specific applications and require a special license, there are a few " "exceptions. These exceptions are known as the `Industrial, Scientific and " "Medical `_ (ISM) radio bands. These " "bands can be used for industrial, scientific and medical applications " "without requiring a license from the regulator. For example, some radio-" "controlled models use the 27 MHz ISM band and some cordless telephones " "operate in the 915 MHz ISM. In 1985, the 2.400-2.500 GHz band was added to " "the list of ISM bands. This frequency range corresponds to the frequencies " "that are emitted by microwave ovens. Sharing this band with licensed " "applications would have likely caused interference, given the large number " "of microwave ovens that are used. Despite the risk of interference with " "microwave ovens, the opening of the 2.400-2.500 GHz allowed the networking " "industry to develop several wireless network techniques to allow computers " "to exchange data without using cables. In this section, we discuss in more " "detail the most popular one, i.e. the WiFi [IEEE802.11]_ family of wireless " "networks. Other wireless networking techniques such as `BlueTooth `_ or `HiperLAN `_ use the same frequency range." msgstr "" "While most of the frequency ranges of the radio spectrum are reserved for " "specific applications and require a special license, there are a few " "exceptions. These exceptions are known as the `Industrial, Scientific and " "Medical `_ (ISM) radio bands. These " "bands can be used for industrial, scientific and medical applications " "without requiring a license from the regulator. For example, some radio-" "controlled models use the 27 MHz ISM band and some cordless telephones " "operate in the 915 MHz ISM. In 1985, the 2.400-2.500 GHz band was added to " "the list of ISM bands. This frequency range corresponds to the frequencies " "that are emitted by microwave ovens. Sharing this band with licensed " "applications would have likely caused interference, given the large number " "of microwave ovens that are used. Despite the risk of interference with " "microwave ovens, the opening of the 2.400-2.500 GHz allowed the networking " "industry to develop several wireless network techniques to allow computers " "to exchange data without using cables. In this section, we discuss in more " "detail the most popular one, i.e. the WiFi [IEEE802.11]_ family of wireless " "networks. Other wireless networking techniques such as `BlueTooth `_ or `HiperLAN `_ use the same frequency range." #: ../../protocols/wifi.rst:15 #, read-only msgid "" "Today, WiFi is a very popular wireless networking technology. There are more " "than several hundreds of millions of WiFi devices. The development of this " "technology started in the late 1980s with the `WaveLAN `_ proprietary wireless network. WaveLAN " "operated at 2 Mbps and used different frequency bands in different regions " "of the world. In the early 1990s, the IEEE_ created the `802.11 working " "group `_ to standardize a family of wireless " "network technologies. This working group was very prolific and produced " "several wireless networking standards that use different frequency ranges " "and different physical layers. The table below provides a summary of the " "main 802.11 standards." msgstr "" "Today, WiFi is a very popular wireless networking technology. There are more " "than several hundreds of millions of WiFi devices. The development of this " "technology started in the late 1980s with the `WaveLAN `_ proprietary wireless network. WaveLAN " "operated at 2 Mbps and used different frequency bands in different regions " "of the world. In the early 1990s, the IEEE_ created the `802.11 working " "group `_ to standardize a family of wireless " "network technologies. This working group was very prolific and produced " "several wireless networking standards that use different frequency ranges " "and different physical layers. The table below provides a summary of the " "main 802.11 standards." #: ../../protocols/wifi.rst:19 #, read-only msgid "Standard" msgstr "Standard" #: ../../protocols/wifi.rst:19 #, read-only msgid "Frequency" msgstr "Frequency" #: ../../protocols/wifi.rst:19 #, read-only msgid "Typical throughput" msgstr "Typical throughput" #: ../../protocols/wifi.rst:19 #, read-only msgid "Max bandwidth" msgstr "Max bandwidth" #: ../../protocols/wifi.rst:19 #, read-only msgid "Range (m) indoor/outdoor" msgstr "Range (m) indoor/outdoor" #: ../../protocols/wifi.rst:22 #, read-only msgid "802.11" msgstr "802.11" #: ../../protocols/wifi.rst:22 #: ../../protocols/wifi.rst:24 #: ../../protocols/wifi.rst:25 #, read-only msgid "2.4 GHz" msgstr "2.4 GHz" #: ../../protocols/wifi.rst:22 #, read-only msgid "0.9 Mbps" msgstr "0.9 Mbps" #: ../../protocols/wifi.rst:22 #, read-only msgid "2 Mbps" msgstr "2 Mbps" #: ../../protocols/wifi.rst:22 #, read-only msgid "20/100" msgstr "20/100" #: ../../protocols/wifi.rst:23 #, read-only msgid "802.11a" msgstr "802.11a" #: ../../protocols/wifi.rst:23 #, read-only msgid "5 GHz" msgstr "5 GHz" #: ../../protocols/wifi.rst:23 #, read-only msgid "23 Mbps" msgstr "23 Mbps" #: ../../protocols/wifi.rst:23 #: ../../protocols/wifi.rst:25 #, read-only msgid "54 Mbps" msgstr "54 Mbps" #: ../../protocols/wifi.rst:23 #, read-only msgid "35/120" msgstr "35/120" #: ../../protocols/wifi.rst:24 #, read-only msgid "802.11b" msgstr "802.11b" #: ../../protocols/wifi.rst:24 #, read-only msgid "4.3 Mbps" msgstr "4.3 Mbps" #: ../../protocols/wifi.rst:24 #, read-only msgid "11 Mbps" msgstr "11 Mbps" #: ../../protocols/wifi.rst:24 #: ../../protocols/wifi.rst:25 #, read-only msgid "38/140" msgstr "38/140" #: ../../protocols/wifi.rst:25 #, read-only msgid "802.11g" msgstr "802.11g" #: ../../protocols/wifi.rst:25 #, read-only msgid "19 Mbps" msgstr "19 Mbps" #: ../../protocols/wifi.rst:26 #, read-only msgid "802.11n" msgstr "802.11n" #: ../../protocols/wifi.rst:26 #, read-only msgid "2.4/5 GHz" msgstr "2.4/5 GHz" #: ../../protocols/wifi.rst:26 #, read-only msgid "74 Mbps" msgstr "74 Mbps" #: ../../protocols/wifi.rst:26 #, read-only msgid "150 Mbps" msgstr "150 Mbps" #: ../../protocols/wifi.rst:26 #, read-only msgid "70/250" msgstr "70/250" #: ../../protocols/wifi.rst:29 #, read-only msgid "" "When developing its family of standards, the `IEEE 802.11 working group " "`_ took a similar approach as the `IEEE 802.3 " "working group `_ that developed various types of " "physical layers for Ethernet networks. 802.11 networks use the CSMA/CA " "Medium Access Control technique described earlier and they all assume the " "same architecture and use the same frame format." msgstr "" "When developing its family of standards, the `IEEE 802.11 working group " "`_ took a similar approach as the `IEEE 802.3 " "working group `_ that developed various types of " "physical layers for Ethernet networks. 802.11 networks use the CSMA/CA " "Medium Access Control technique described earlier and they all assume the " "same architecture and use the same frame format." #: ../../protocols/wifi.rst:35 #, read-only msgid "" "The architecture of WiFi networks is slightly different from the Local Area " "Networks that we have discussed until now. There are, in practice, two main " "types of WiFi networks : `independent` or `adhoc` networks and " "`infrastructure` networks [#fBSS]_. An `independent` or `adhoc` network is " "composed of a set of devices that communicate with each other. These devices " "play the same role and the `adhoc` network is usually not connected to the " "global Internet. `Adhoc` networks are used when for example a few laptops " "need to exchange information or to connect a computer with a WiFi printer." msgstr "" "The architecture of WiFi networks is slightly different from the Local Area " "Networks that we have discussed until now. There are, in practice, two main " "types of WiFi networks : `independent` or `adhoc` networks and " "`infrastructure` networks [#fBSS]_. An `independent` or `adhoc` network is " "composed of a set of devices that communicate with each other. These devices " "play the same role and the `adhoc` network is usually not connected to the " "global Internet. `Adhoc` networks are used when for example a few laptops " "need to exchange information or to connect a computer with a WiFi printer." #: ../../protocols/wifi.rst:42 #, read-only msgid "An 802.11 independent or adhoc network" msgstr "An 802.11 independent or adhoc network" #: ../../protocols/wifi.rst:47 #, read-only msgid "" "Most WiFi networks are `infrastructure` networks. An `infrastructure` " "network contains one or more `access points` that are attached to a fixed " "Local Area Network (usually an Ethernet network) that is connected to other " "networks such as the Internet. The figure below shows such a network with " "two access points and four WiFi devices. Each WiFi device is associated to " "one access point and uses this access point as a relay to exchange frames " "with the devices that are associated to another access point or reachable " "through the LAN." msgstr "" "Most WiFi networks are `infrastructure` networks. An `infrastructure` " "network contains one or more `access points` that are attached to a fixed " "Local Area Network (usually an Ethernet network) that is connected to other " "networks such as the Internet. The figure below shows such a network with " "two access points and four WiFi devices. Each WiFi device is associated to " "one access point and uses this access point as a relay to exchange frames " "with the devices that are associated to another access point or reachable " "through the LAN." #: ../../protocols/wifi.rst:54 #, read-only msgid "An 802.11 infrastructure network" msgstr "An 802.11 infrastructure network" #: ../../protocols/wifi.rst:56 #, read-only msgid "" "An 802.11 access point is a relay that operates in the datalink layer like " "switches. The figure below represents the layers of the reference model that " "are involved when a WiFi host communicates with a host attached to an " "Ethernet network through an access point." msgstr "" "An 802.11 access point is a relay that operates in the datalink layer like " "switches. The figure below represents the layers of the reference model that " "are involved when a WiFi host communicates with a host attached to an " "Ethernet network through an access point." #: ../../protocols/wifi.rst:93 #, read-only msgid "" "802.11 devices exchange variable length frames, which have a slightly " "different structure than the simple frame format used in Ethernet LANs. We " "review the key parts of the 802.11 frames. Additional details may be found " "in [IEEE802.11]_ and [Gast2002]_ . An 802.11 frame contains a fixed length " "header, a variable length payload that may contain up 2324 bytes of user " "data and a 32 bits CRC. Although the payload can contain up to 2324 bytes, " "most 802.11 deployments use a maximum payload size of 1500 bytes as they are " "used in `infrastructure` networks attached to Ethernet LANs. An 802.11 data " "frame is shown below." msgstr "" "802.11 devices exchange variable length frames, which have a slightly " "different structure than the simple frame format used in Ethernet LANs. We " "review the key parts of the 802.11 frames. Additional details may be found " "in [IEEE802.11]_ and [Gast2002]_ . An 802.11 frame contains a fixed length " "header, a variable length payload that may contain up 2324 bytes of user " "data and a 32 bits CRC. Although the payload can contain up to 2324 bytes, " "most 802.11 deployments use a maximum payload size of 1500 bytes as they are " "used in `infrastructure` networks attached to Ethernet LANs. An 802.11 data " "frame is shown below." #: ../../protocols/wifi.rst:99 #, read-only msgid "802.11 data frame format" msgstr "802.11 data frame format" #: ../../protocols/wifi.rst:102 #, read-only msgid "" "The first part of the 802.11 header is the 16 bit `Frame Control` field. " "This field contains flags that indicate the type of frame " "(data frame, RTS/CTS, acknowledgment, management frames, etc), whether the " "frame is sent to or from a fixed LAN, etc [IEEE802.11]_. The `Duration` is a " "16 bit field that is used to reserve the transmission channel. In data " "frames, the `Duration` field is usually set to the time required to transmit " "one acknowledgment frame after a SIFS delay. Note that the `Duration` field " "must be set to zero in multicast and broadcast frames. As these frames are " "not acknowledged, there is no need to reserve the transmission channel after " "their transmission. The `Sequence control` field contains a 12 bits sequence " "number that is incremented for each data frame and a 4 bits fragment number." msgstr "" "The first part of the 802.11 header is the 16 bit `Frame Control` field. " "This field contains flags that indicate the type of frame " "(data frame, RTS/CTS, acknowledgment, management frames, etc), whether the " "frame is sent to or from a fixed LAN, etc [IEEE802.11]_. The `Duration` is a " "16 bit field that is used to reserve the transmission channel. In data " "frames, the `Duration` field is usually set to the time required to transmit " "one acknowledgment frame after a SIFS delay. Note that the `Duration` field " "must be set to zero in multicast and broadcast frames. As these frames are " "not acknowledged, there is no need to reserve the transmission channel after " "their transmission. The `Sequence control` field contains a 12 bits sequence " "number that is incremented for each data frame and a 4 bits fragment number." #: ../../protocols/wifi.rst:105 #, read-only msgid "" "The astute reader may have noticed that the 802.11 data frames contain three " "48-bits address fields [#f4addresses]_ . This is surprising compared to " "other protocols in the network and datalink layers whose headers only " "contain a source and a destination address. The need for a third address in " "the 802.11 header comes from the `infrastructure` networks. In such a " "network, frames are usually exchanged between routers and servers attached " "to the LAN and WiFi devices attached to one of the access points. The role " "of the three address fields is specified by bit flags in the `Frame Control` " "field." msgstr "" "The astute reader may have noticed that the 802.11 data frames contain three " "48-bits address fields [#f4addresses]_ . This is surprising compared to " "other protocols in the network and datalink layers whose headers only " "contain a source and a destination address. The need for a third address in " "the 802.11 header comes from the `infrastructure` networks. In such a " "network, frames are usually exchanged between routers and servers attached " "to the LAN and WiFi devices attached to one of the access points. The role " "of the three address fields is specified by bit flags in the `Frame Control` " "field." #: ../../protocols/wifi.rst:107 #, read-only msgid "" "When a frame is sent from a WiFi device to a server attached to the same LAN " "as the access point, the first address of the frame is set to the MAC " "address of the access point, the second address is set to the MAC address of " "the source WiFi device and the third address is the address of the final " "destination on the LAN. When the server replies, it sends an Ethernet frame " "whose source address is its MAC address and the destination address is the " "MAC address of the WiFi device. This frame is captured by the access point " "that converts the Ethernet header into an 802.11 frame header. The 802.11 " "frame sent by the access point contains three addresses : the first address " "is the MAC address of the destination WiFi device, the second address is the " "MAC address of the access point and the third address the MAC address of the " "server that sent the frame." msgstr "" "When a frame is sent from a WiFi device to a server attached to the same LAN " "as the access point, the first address of the frame is set to the MAC " "address of the access point, the second address is set to the MAC address of " "the source WiFi device and the third address is the address of the final " "destination on the LAN. When the server replies, it sends an Ethernet frame " "whose source address is its MAC address and the destination address is the " "MAC address of the WiFi device. This frame is captured by the access point " "that converts the Ethernet header into an 802.11 frame header. The 802.11 " "frame sent by the access point contains three addresses : the first address " "is the MAC address of the destination WiFi device, the second address is the " "MAC address of the access point and the third address the MAC address of the " "server that sent the frame." #: ../../protocols/wifi.rst:109 #, read-only msgid "" "802.11 control frames are simpler than data frames. They contain a `Frame " "Control`, a `Duration` field and one or two addresses. The acknowledgment " "frames are very small. They only contain the address of the destination of " "the acknowledgment. There is no source address and no `Sequence Control` " "field in the acknowledgment frames. This is because the acknowledgment frame " "can easily be associated to the previous frame that it acknowledges. Indeed, " "each unicast data frame contains a `Duration` field that is used to reserve " "the transmission channel to ensure that no collision will affect the " "acknowledgment frame. The `Sequence Control` field is mainly used by the " "receiver to remove duplicate frames. Duplicate frames are detected as " "follows. Each data frame contains a 12 bits sequence number in the `Sequence " "Control` field and the `Frame Control` field contains the `Retry` bit flag " "that is set when a frame is transmitted. Each 802.11 receiver stores the " "most recent sequence number received from each source address in frames " "whose `Retry` bit is reset. Upon reception of a frame with the `Retry` bit " "set, the receiver verifies its sequence number to determine whether it is a " "duplicated frame or not." msgstr "" "802.11 control frames are simpler than data frames. They contain a `Frame " "Control`, a `Duration` field and one or two addresses. The acknowledgment " "frames are very small. They only contain the address of the destination of " "the acknowledgment. There is no source address and no `Sequence Control` " "field in the acknowledgment frames. This is because the acknowledgment frame " "can easily be associated to the previous frame that it acknowledges. Indeed, " "each unicast data frame contains a `Duration` field that is used to reserve " "the transmission channel to ensure that no collision will affect the " "acknowledgment frame. The `Sequence Control` field is mainly used by the " "receiver to remove duplicate frames. Duplicate frames are detected as " "follows. Each data frame contains a 12 bits sequence number in the `Sequence " "Control` field and the `Frame Control` field contains the `Retry` bit flag " "that is set when a frame is transmitted. Each 802.11 receiver stores the " "most recent sequence number received from each source address in frames " "whose `Retry` bit is reset. Upon reception of a frame with the `Retry` bit " "set, the receiver verifies its sequence number to determine whether it is a " "duplicated frame or not." #: ../../protocols/wifi.rst:115 #, read-only msgid "IEEE 802.11 ACK and CTS frames" msgstr "IEEE 802.11 ACK and CTS frames" #: ../../protocols/wifi.rst:120 #, read-only msgid "" "802.11 RTS/CTS frames are used to reserve the transmission channel, in order " "to transmit one data frame and its acknowledgment. The RTS frames contain a " "`Duration` and the transmitter and receiver addresses. The `Duration` field " "of the RTS frame indicates the duration of the entire reservation (i.e. the " "time required to transmit the CTS, the data frame, the acknowledgments and " "the required SIFS delays). The CTS frame has the same format as the " "acknowledgment frame." msgstr "" "802.11 RTS/CTS frames are used to reserve the transmission channel, in order " "to transmit one data frame and its acknowledgment. The RTS frames contain a " "`Duration` and the transmitter and receiver addresses. The `Duration` field " "of the RTS frame indicates the duration of the entire reservation (i.e. the " "time required to transmit the CTS, the data frame, the acknowledgments and " "the required SIFS delays). The CTS frame has the same format as the " "acknowledgment frame." #: ../../protocols/wifi.rst:126 #, read-only msgid "IEEE 802.11 RTS frame format" msgstr "IEEE 802.11 RTS frame format" #: ../../protocols/wifi.rst:129 #, read-only msgid "The 802.11 service" msgstr "The 802.11 service" #: ../../protocols/wifi.rst:131 #, read-only msgid "" "Despite the utilization of acknowledgments, the 802.11 layer only provides " "an unreliable connectionless service like Ethernet networks that do not use " "acknowledgments. The 802.11 acknowledgments are used to minimize the " "probability of frame duplication. They do not guarantee that all frames will " "be correctly received by their recipients. Like Ethernet, 802.11 networks " "provide a high probability of successful delivery of the frames, not a " "guarantee. Furthermore, it should be noted that 802.11 networks do not use " "acknowledgments for multicast and broadcast frames. This implies that in " "practice such frames are more likely to suffer from transmission errors than " "unicast frames." msgstr "" "Despite the utilization of acknowledgments, the 802.11 layer only provides " "an unreliable connectionless service like Ethernet networks that do not use " "acknowledgments. The 802.11 acknowledgments are used to minimize the " "probability of frame duplication. They do not guarantee that all frames will " "be correctly received by their recipients. Like Ethernet, 802.11 networks " "provide a high probability of successful delivery of the frames, not a " "guarantee. Furthermore, it should be noted that 802.11 networks do not use " "acknowledgments for multicast and broadcast frames. This implies that in " "practice such frames are more likely to suffer from transmission errors than " "unicast frames." #: ../../protocols/wifi.rst:135 #, read-only msgid "" "In addition to the data and control frames that we have briefly described " "above, 802.11 networks use several types of management frames. These " "management frames are used for various purposes. We briefly describe some of " "these frames below. A detailed discussion may be found in [IEEE802.11]_ and " "[Gast2002]_." msgstr "" "In addition to the data and control frames that we have briefly described " "above, 802.11 networks use several types of management frames. These " "management frames are used for various purposes. We briefly describe some of " "these frames below. A detailed discussion may be found in [IEEE802.11]_ and " "[Gast2002]_." #: ../../protocols/wifi.rst:141 #, read-only msgid "" "A first type of management frames are the `beacon` frames. These frames are " "broadcasted regularly by access points. Each `beacon frame` contains " "information about the capabilities of the access point " "(e.g. the supported 802.11 transmission rates) and a `Service Set Identity` " "(SSID). The SSID is a null-terminated ASCII string that can contain up to 32 " "characters. An access point may support several SSIDs and announce them in " "beacon frames. An access point may also choose to remain silent and not " "advertise beacon frames. In this case, WiFi stations may send `Probe request`" " frames to force the available access points to return a `Probe response` " "frame." msgstr "" "A first type of management frames are the `beacon` frames. These frames are " "broadcasted regularly by access points. Each `beacon frame` contains " "information about the capabilities of the access point " "(e.g. the supported 802.11 transmission rates) and a `Service Set Identity` " "(SSID). The SSID is a null-terminated ASCII string that can contain up to 32 " "characters. An access point may support several SSIDs and announce them in " "beacon frames. An access point may also choose to remain silent and not " "advertise beacon frames. In this case, WiFi stations may send `Probe request`" " frames to force the available access points to return a `Probe response` " "frame." #: ../../protocols/wifi.rst:144 #, read-only msgid "IP over 802.11" msgstr "IP over 802.11" #: ../../protocols/wifi.rst:146 #, read-only msgid "" "Two types of encapsulation schemes were defined to support IP in Ethernet " "networks : the original encapsulation scheme, built above the Ethernet DIX " "format is defined in :rfc:`894` and a second encapsulation :rfc:`1042` " "scheme, built above the LLC/SNAP protocol [IEEE802.2]_. In 802.11 networks, " "the situation is simpler and only the :rfc:`1042` encapsulation is used. In " "practice, this encapsulation adds 6 bytes to the 802.11 header. The first " "four bytes correspond to the LLC/SNAP header. They are followed by the two " "bytes Ethernet Type field (`0x800` for IP and `0x806` for ARP). The figure " "below shows an IP packet encapsulated in an 802.11 frame." msgstr "" "Two types of encapsulation schemes were defined to support IP in Ethernet " "networks : the original encapsulation scheme, built above the Ethernet DIX " "format is defined in :rfc:`894` and a second encapsulation :rfc:`1042` " "scheme, built above the LLC/SNAP protocol [IEEE802.2]_. In 802.11 networks, " "the situation is simpler and only the :rfc:`1042` encapsulation is used. In " "practice, this encapsulation adds 6 bytes to the 802.11 header. The first " "four bytes correspond to the LLC/SNAP header. They are followed by the two " "bytes Ethernet Type field (`0x800` for IP and `0x806` for ARP). The figure " "below shows an IP packet encapsulated in an 802.11 frame." #: ../../protocols/wifi.rst:152 #, read-only msgid "IP over IEEE 802.11" msgstr "IP over IEEE 802.11" #: ../../protocols/wifi.rst:154 #, read-only msgid "" "The second important utilization of the management frames is to allow a WiFi " "station to be associated with an access point. When a WiFi station starts, " "it listens to beacon frames to find the available SSIDs. To be allowed to " "send and receive frames via an access point, a WiFi station must be " "associated to this access point. If the access point does not use any " "security mechanism to secure the wireless transmission, the WiFi station " "simply sends an `Association request` frame to its preferred access point " "(usually the access point that it receives with the strongest radio signal). " "This frame contains some parameters chosen by the WiFi station and the SSID " "that it requests to join. The access point replies with an `Association " "response frame` if it accepts the WiFI station." msgstr "" "The second important utilization of the management frames is to allow a WiFi " "station to be associated with an access point. When a WiFi station starts, " "it listens to beacon frames to find the available SSIDs. To be allowed to " "send and receive frames via an access point, a WiFi station must be " "associated to this access point. If the access point does not use any " "security mechanism to secure the wireless transmission, the WiFi station " "simply sends an `Association request` frame to its preferred access point " "(usually the access point that it receives with the strongest radio signal). " "This frame contains some parameters chosen by the WiFi station and the SSID " "that it requests to join. The access point replies with an `Association " "response frame` if it accepts the WiFI station." #: ../../protocols/wifi.rst:157 #, read-only msgid "Footnotes" msgstr "Footnotes" #: ../../protocols/wifi.rst:158 #, read-only msgid "" "The 802.11 working group defined the `basic service set (BSS)` as a group of " "devices that communicate with each other. We continue to use `network` when " "referring to a set of devices that communicate." msgstr "" "The 802.11 working group defined the `basic service set (BSS)` as a group of " "devices that communicate with each other. We continue to use `network` when " "referring to a set of devices that communicate." #: ../../protocols/wifi.rst:160 #, read-only msgid "" "In fact, the [IEEE802.11]_ frame format contains a fourth optional address " "field. This fourth address is only used when an 802.11 wireless network is " "used to interconnect bridges attached to two classical LAN networks." msgstr "" "In fact, the [IEEE802.11]_ frame format contains a fourth optional address " "field. This fourth address is only used when an 802.11 wireless network is " "used to interconnect bridges attached to two classical LAN networks."