cosmos321
Dauer-User
- 475
Ja danke, habe ich mir auch durchgelesen und werde ich vor dem Totalflash meiner Geräte nochmal probieren!
Der ursprüngliche Beitrag von 13:36 Uhr wurde um 14:14 Uhr ergänzt:
So ich zitiere mal aus dem DD-WRT Forum bzgl. "beacon_interval" und "dtim" :
Noch etwas mehr zu "beacon_interval":
Quelle: KLICK
...und "dtim":
Quelle: KLICK
Ich werde meine Werte jetzt mal auf beacon=200 und dtim=2 stellen. Mal schauen was sich ändert, vor allem in Bezug auf Video- und Audiostreaming, welches ich ja bzgl. meines Mediaservers sehr stark nutze.
Auf alle Fälle an dieser Stelle nochmals ein GROßES DANKESCHÖN an "holliwood" für diesen Wink!
Der ursprüngliche Beitrag von 14:14 Uhr wurde um 14:21 Uhr ergänzt:
EDIT: Falls es jemand ebenfalls testen möchte (wenn er DD-WRT bzw. OpenWRT benutzt), dann einfach folgende Werte in einer Command-Shell absetzen:
mit
können dann die Werte ausgelesen/überprüft werden!
Leider bietet bei mir (Atheros Chipsatz) DD-WRT über das WebIf keine Einstellmöglichkeit an. Bei broadcom-basierten Geräten scheint es aber zu gehen!
Mal so zum Vergleich: Meine Fritz!Box 7240 hat folgende Werte: beacon=100 und dtim=0 ! Bin also mal auf den Unterschied gespannt!
Der ursprüngliche Beitrag von 13:36 Uhr wurde um 14:14 Uhr ergänzt:
So ich zitiere mal aus dem DD-WRT Forum bzgl. "beacon_interval" und "dtim" :
Quelle: KLICK
Noch etwas mehr zu "beacon_interval":
Beacon Interval
Range 1 and 65,535 milliseconds. The default value is 100.
The help file says...
The term beacon signifies a specific data transmission from the wireless access point (AP), which carries the SSID, the channel number and security protocols such as WEP (Wired Equivalent Protection) or WPA (Wi-Fi Protected Access). This transmission does not contain the link layer address of another Wi-Fi device, therefore it can be received by any LAN client.The beacon frame, which is a type of management frame, can be likened with the "heartbeat" of a wireless LAN, enabling stations to establish and maintain communications in an orderly fashion.
What is a Beacon Interval As mentioned above, the beacon interval is a fixed, configurable parameter. Typically, the beacon interval setting is not touched at all in the WLAN network installation phase, but the default value selected by the equipment supplier is used. If the beacon interval is long, maximum capacity in the Access Point is achieved. However, it will the take a long time for WLAN terminals to scan for Access Points in the area and to update RSSI and load information for already found Access Points. This obviously reduces terminal throughput and wastes battery. On the other hand, if the beacon interval in short, passive scanning performed by the WLAN terminals will be faster, but the overall capacity of the Access Point will be reduced.
NOTE There are no special rules for sending beacons, and they must be sent using the mandatory 802.11 carrier sense multiple access / collision avoidance (CSMA/CA) algorithm. If another station is sending a frame when the beacon is to be sent, then the access point (or NIC in an ad hoc network) must wait. As a result, the actual time between beacons may be longer than the beacon interval. Clients, however, compensate for this inaccuracy by utilizing the timestamp found within the beacon packet information.
What is a Beacon?
A typical beacon frame is approximately fifty bytes long, with about half of that being a common frame header and cyclic redundancy checking (CRC) field. As with other frames, the header includes source and destination MAC addresses as well as other information regarding the communications process. The destination address is always set to all ones, which is the broadcast Medium Access Control (MAC) address. This forces all other stations on the applicable channel to receive and process each beacon frame. The CRC field provides error detection capability.
The beacon's frame body resides between the header and the CRC field and constitutes the other half of the beacon frame. Each beacon frame carries the following information in the frame body:
Beacon interval. This represents the amount of time between beacon transmissions. Before a station enters power save mode, the station needs the beacon interval to know when to wake up to receive the beacon (and learn whether there are buffered frames at the access point).
Timestamp. After receiving a beacon frame, a station uses the timestamp value to update its local clock. This process enables synchronization among all stations that are associated with the same access point.
Service Set Identifier (SSID). The SSID identifies a specific wireless LAN. Before associating with a particular wireless LAN, a client must have the same SSID configured as the access point. By default, access points include the SSID in the beacon frame to enable sniffing functions (such as that provided by Windows XP) to identify the SSID and automatically configure the wireless network interface card (NIC) with the proper SSID. DD-Wrt also has an option to disable the SSID from being broadcast in beacon frames to reduce security issues.
Supported rates. Each beacon carries information that describes the rates that the particular wireless LAN supports. For example, a beacon may indicate that only 1, 2, and 5.5Mbps data rates are available. As a result, an 802.11b station would stay within limits and not use 11 Mbps. With this information, stations can use performance metrics to decide which access point to associate with.
Parameter Sets. The beacon includes information about the specific signaling methods (such as frequency hopping spread spectrum, CTS Protection mode and RTS Threshold,direct sequence spread spectrum, etc.). For example, a beacon would include in the appropriate parameter set the channel number that an 802.11b access point is using. Likewise, a beacon belonging to frequency hopping network would indicate hopping pattern and dwell time.
Capability Information. This signifies requirements of stations that wish to belong to the wireless LAN that the beacon represents. For example, this information may indicate that all clients must use wired equivalent privacy (WEP) in order to participate on the network.
Traffic Indication Map (TIM). An access point periodically sends the TIM within a beacon to identify which stations using power saving mode have data frames waiting for them in the access point's buffer. The TIM identifies a station by the association ID that the access point assigned during the association process.
NOTE Today beacon frames also contain a load information that informs WLAN terminals currently connected to a specific Access Point or considering making a handover to that Access Point about the load situation. This information helps the WLANterminals in making correct handover decision, in addition to the information from the comparisons of RSSI readings obtained by scanning, and thus ensures that WLAN traffic is divided more evenly between all Access Points in the area.
TWEAK:
By increasing the beacon interval, you can reduce the number of beacons and associated overhead, but that will likely delay the association and roaming process because stations scanning for available access points may miss the beacons.
You can decrease the beacon interval, which increases the rate of beacons. This will make the association and roaming process very responsive; however, the network will incur additional overhead and throughput will go down.
In addition, stations using power save mode will need to consume more power because they'll need to awaken more often, which reduces power saving mode benefits. In an idle network, beacons dominate all other traffic.
Guide to tweaking: The amount of overhead that the transmissions of beacon frames generate is substantial; however, the beacon serves a variety of functions. For example, each beacon transmission identifies the presence of an access point.
How a beacon interval impacts the client By default, radio NICs passively scan all RF channels and listen for beacons coming from access points in order to find a suitable access point. When a beacon is found, the radio NIC learns a great deal about that particular network. This enables a ranking of access points based on the received signal strength of the beacon, along with capability information regarding the network. The radio NIC can then associate with the most preferable access point. After association, the station continues to scan for other beacons in case the signal from the currently-associated access point become too weak to maintain communications. As the radio NIC receives beacons from the associated access point, the radio NIC updates its local clock to maintain timing synchronization with the access point and other stations. In addition, the radio NIC will abide by any other changes, such as data rate, that the frame body of the beacon indicates. The beacons also support stations implementing power saving mode. With infrastructure networks, the access point will buffer frames destined for sleeping stations and announce which radio NICs have frames waiting through the TIM (DTIMS) that's part of the beacon
Do clients send beacon frames too??... As apposed to beacons sent out by AP's, Clients send out "probe request" frames; It's like an opposite to a beacon, clients use a probe request packets to play there role in the 802.11 WLAN. An 802.11 probe response frame is very similar to a beacon frame, except that probe responses don't carry the TIM info and are only sent in response to a probe request. A client may send a probe request frame to trigger a probe response when the client needs to obtain information from another client on the same WLAN. A client, for instance, will broadcast a probe request when using active scanning to determine which access points are within range for possible association. Some sniffing software (e.g., NetStumbler) tools send probe requests so that access points will respond with desired info.
-Beacons are packets sent by an access point to synchronize a wireless network.
-Normal Traffic Indication Message(TIM)s that are present in every beacon are for signaling the presence of unbuffered unicast data.
Range 1 and 65,535 milliseconds. The default value is 100.
The help file says...
- The Beacon Interval value indicates the frequency interval of the beacon. A beacon is a packet broadcast by the router to synchronize the wireless network. 50 is recommended in poor reception.
The term beacon signifies a specific data transmission from the wireless access point (AP), which carries the SSID, the channel number and security protocols such as WEP (Wired Equivalent Protection) or WPA (Wi-Fi Protected Access). This transmission does not contain the link layer address of another Wi-Fi device, therefore it can be received by any LAN client.The beacon frame, which is a type of management frame, can be likened with the "heartbeat" of a wireless LAN, enabling stations to establish and maintain communications in an orderly fashion.
What is a Beacon Interval As mentioned above, the beacon interval is a fixed, configurable parameter. Typically, the beacon interval setting is not touched at all in the WLAN network installation phase, but the default value selected by the equipment supplier is used. If the beacon interval is long, maximum capacity in the Access Point is achieved. However, it will the take a long time for WLAN terminals to scan for Access Points in the area and to update RSSI and load information for already found Access Points. This obviously reduces terminal throughput and wastes battery. On the other hand, if the beacon interval in short, passive scanning performed by the WLAN terminals will be faster, but the overall capacity of the Access Point will be reduced.
NOTE There are no special rules for sending beacons, and they must be sent using the mandatory 802.11 carrier sense multiple access / collision avoidance (CSMA/CA) algorithm. If another station is sending a frame when the beacon is to be sent, then the access point (or NIC in an ad hoc network) must wait. As a result, the actual time between beacons may be longer than the beacon interval. Clients, however, compensate for this inaccuracy by utilizing the timestamp found within the beacon packet information.
What is a Beacon?
A typical beacon frame is approximately fifty bytes long, with about half of that being a common frame header and cyclic redundancy checking (CRC) field. As with other frames, the header includes source and destination MAC addresses as well as other information regarding the communications process. The destination address is always set to all ones, which is the broadcast Medium Access Control (MAC) address. This forces all other stations on the applicable channel to receive and process each beacon frame. The CRC field provides error detection capability.
The beacon's frame body resides between the header and the CRC field and constitutes the other half of the beacon frame. Each beacon frame carries the following information in the frame body:
Beacon interval. This represents the amount of time between beacon transmissions. Before a station enters power save mode, the station needs the beacon interval to know when to wake up to receive the beacon (and learn whether there are buffered frames at the access point).
Timestamp. After receiving a beacon frame, a station uses the timestamp value to update its local clock. This process enables synchronization among all stations that are associated with the same access point.
Service Set Identifier (SSID). The SSID identifies a specific wireless LAN. Before associating with a particular wireless LAN, a client must have the same SSID configured as the access point. By default, access points include the SSID in the beacon frame to enable sniffing functions (such as that provided by Windows XP) to identify the SSID and automatically configure the wireless network interface card (NIC) with the proper SSID. DD-Wrt also has an option to disable the SSID from being broadcast in beacon frames to reduce security issues.
Supported rates. Each beacon carries information that describes the rates that the particular wireless LAN supports. For example, a beacon may indicate that only 1, 2, and 5.5Mbps data rates are available. As a result, an 802.11b station would stay within limits and not use 11 Mbps. With this information, stations can use performance metrics to decide which access point to associate with.
Parameter Sets. The beacon includes information about the specific signaling methods (such as frequency hopping spread spectrum, CTS Protection mode and RTS Threshold,direct sequence spread spectrum, etc.). For example, a beacon would include in the appropriate parameter set the channel number that an 802.11b access point is using. Likewise, a beacon belonging to frequency hopping network would indicate hopping pattern and dwell time.
Capability Information. This signifies requirements of stations that wish to belong to the wireless LAN that the beacon represents. For example, this information may indicate that all clients must use wired equivalent privacy (WEP) in order to participate on the network.
Traffic Indication Map (TIM). An access point periodically sends the TIM within a beacon to identify which stations using power saving mode have data frames waiting for them in the access point's buffer. The TIM identifies a station by the association ID that the access point assigned during the association process.
NOTE Today beacon frames also contain a load information that informs WLAN terminals currently connected to a specific Access Point or considering making a handover to that Access Point about the load situation. This information helps the WLANterminals in making correct handover decision, in addition to the information from the comparisons of RSSI readings obtained by scanning, and thus ensures that WLAN traffic is divided more evenly between all Access Points in the area.
TWEAK:
By increasing the beacon interval, you can reduce the number of beacons and associated overhead, but that will likely delay the association and roaming process because stations scanning for available access points may miss the beacons.
You can decrease the beacon interval, which increases the rate of beacons. This will make the association and roaming process very responsive; however, the network will incur additional overhead and throughput will go down.
In addition, stations using power save mode will need to consume more power because they'll need to awaken more often, which reduces power saving mode benefits. In an idle network, beacons dominate all other traffic.
Guide to tweaking: The amount of overhead that the transmissions of beacon frames generate is substantial; however, the beacon serves a variety of functions. For example, each beacon transmission identifies the presence of an access point.
How a beacon interval impacts the client By default, radio NICs passively scan all RF channels and listen for beacons coming from access points in order to find a suitable access point. When a beacon is found, the radio NIC learns a great deal about that particular network. This enables a ranking of access points based on the received signal strength of the beacon, along with capability information regarding the network. The radio NIC can then associate with the most preferable access point. After association, the station continues to scan for other beacons in case the signal from the currently-associated access point become too weak to maintain communications. As the radio NIC receives beacons from the associated access point, the radio NIC updates its local clock to maintain timing synchronization with the access point and other stations. In addition, the radio NIC will abide by any other changes, such as data rate, that the frame body of the beacon indicates. The beacons also support stations implementing power saving mode. With infrastructure networks, the access point will buffer frames destined for sleeping stations and announce which radio NICs have frames waiting through the TIM (DTIMS) that's part of the beacon
Do clients send beacon frames too??... As apposed to beacons sent out by AP's, Clients send out "probe request" frames; It's like an opposite to a beacon, clients use a probe request packets to play there role in the 802.11 WLAN. An 802.11 probe response frame is very similar to a beacon frame, except that probe responses don't carry the TIM info and are only sent in response to a probe request. A client may send a probe request frame to trigger a probe response when the client needs to obtain information from another client on the same WLAN. A client, for instance, will broadcast a probe request when using active scanning to determine which access points are within range for possible association. Some sniffing software (e.g., NetStumbler) tools send probe requests so that access points will respond with desired info.
-Beacons are packets sent by an access point to synchronize a wireless network.
-Normal Traffic Indication Message(TIM)s that are present in every beacon are for signaling the presence of unbuffered unicast data.
...und "dtim":
DTIM Interval
The default value is 1.
The help file says...
A Delivery Traffic Indication Message is a kind of Traffic Indication Message(TIM) which informs the clients about the presence of buffered and/or multicast/broadcast data on the access point. It is generated within the periodic beacon at a frequency specified by the DTIM Interval. After a DTIM, the access point will send the multicasted/broadcasted data on the channel following the normal channel access rules (CSMA/CA).
According to the 802.11 standards, a Delivery Traffic Indication Message (DTIM) period value is a number that determines how often a beacon frame includes a Delivery Traffic Indication Message, and this number is included in each beacon frame. A DTIM is included in beacon frames, according to the DTIM period, to indicate to the client devices whether the access point has buffered broadcast and/or multicast data waiting for them. Following a beacon frame that includes a DTIM, the access point will release the buffered broadcast and/or multicast data, if any exists.
Since beacon frames are sent using the mandatory 802.11 carrier sense multiple access/collision detection (CSMA/CD) algorithm, the access point must wait if a client device is sending a frame when the beacon is to be sent. As a result, the actual time between beacons may be longer than the beacon interval. Client devices that awaken from power-save mode may find that they have to wait longer than expected to receive the next beacon frame. Client devices, however, compensate for this inaccuracy by utilizing the time-stamp found within the beacon frame.
The 802.11 standards define a power-save mode for client devices. In power-save mode, a client device may choose to sleep for one or more beacon intervals waking for beacon frames that include DTIMs. When the DTIM period is 2, a client device in power-save mode will awaken to receive every other beacon frame. Upon entering power-save mode, a client device will transmit a notification to the access point, so that the access point will know how to handle unicast traffic destined for the client device. The client device will begin to sleep according to the DTIM period.
-The higher the DTIM period, the longer a client device may sleep and therefore the more power that particular client device may potentially save.
-Client devices in wireless networks may have conflicting requirements for power consumption and communication throughput when in power-save mode. For example, laptops may require relatively high communication throughput and may have low sensitivity to power consumption. Therefore, a relatively low DTIM period, for example 1, may be suitable for laptops . However, cellphones may require relatively low communication throughput and may be operated by batteries of relatively low capacity. Therefore, a relatively high DTIM period, for example 8, may be suitable for cellphones. Further, PDA\Smart phones may require a medium to high communication throughput and may be operated by batteries of relatively low capacity. Therefore, a medium DTIM period, for example a value of 4, may be suitable for these devices.
-Currently, an access point is able to store only a single DTIM period. Consequently, different client devices in power-save mode will all wake up for the same beacon frames according to the DTIM period. Currently, a network manager may need to balance the conflicting requirements for power consumption and communication throughput when in power-save mode of client devices in different wireless networks when configuring the DTIM period of an access point. In the future an access point with support for two or more SSIDs may have SSID-dependent DTIM periods rather than a single DTIM period for all SSIDs. In other words, the network manager may configure the access point with DTIM periods on a per SSID basis. A network manager may consider the requirements of power consumption and communication throughput of client devices in a particular wireless networks when determining which DTIM period to configure for which SSID. A higher DTIM period may increase the potential savings in power consumption but may reduce the communication throughput, and vice versa
The default value is 1.
The help file says...
- Indicates the interval of the Delivery Traffic Indication Message (DTIM). A DTIM field is a countdown field informing clients of the next window for listening to broadcast and multicast messages. When the router has buffered broadcast or multicast messages for associated clients, it sends the next DTIM with a DTIM Interval value. Its clients hear the beacons and awaken to receive the broadcast and multicast messages.
A Delivery Traffic Indication Message is a kind of Traffic Indication Message(TIM) which informs the clients about the presence of buffered and/or multicast/broadcast data on the access point. It is generated within the periodic beacon at a frequency specified by the DTIM Interval. After a DTIM, the access point will send the multicasted/broadcasted data on the channel following the normal channel access rules (CSMA/CA).
According to the 802.11 standards, a Delivery Traffic Indication Message (DTIM) period value is a number that determines how often a beacon frame includes a Delivery Traffic Indication Message, and this number is included in each beacon frame. A DTIM is included in beacon frames, according to the DTIM period, to indicate to the client devices whether the access point has buffered broadcast and/or multicast data waiting for them. Following a beacon frame that includes a DTIM, the access point will release the buffered broadcast and/or multicast data, if any exists.
Since beacon frames are sent using the mandatory 802.11 carrier sense multiple access/collision detection (CSMA/CD) algorithm, the access point must wait if a client device is sending a frame when the beacon is to be sent. As a result, the actual time between beacons may be longer than the beacon interval. Client devices that awaken from power-save mode may find that they have to wait longer than expected to receive the next beacon frame. Client devices, however, compensate for this inaccuracy by utilizing the time-stamp found within the beacon frame.
The 802.11 standards define a power-save mode for client devices. In power-save mode, a client device may choose to sleep for one or more beacon intervals waking for beacon frames that include DTIMs. When the DTIM period is 2, a client device in power-save mode will awaken to receive every other beacon frame. Upon entering power-save mode, a client device will transmit a notification to the access point, so that the access point will know how to handle unicast traffic destined for the client device. The client device will begin to sleep according to the DTIM period.
-The higher the DTIM period, the longer a client device may sleep and therefore the more power that particular client device may potentially save.
-Client devices in wireless networks may have conflicting requirements for power consumption and communication throughput when in power-save mode. For example, laptops may require relatively high communication throughput and may have low sensitivity to power consumption. Therefore, a relatively low DTIM period, for example 1, may be suitable for laptops . However, cellphones may require relatively low communication throughput and may be operated by batteries of relatively low capacity. Therefore, a relatively high DTIM period, for example 8, may be suitable for cellphones. Further, PDA\Smart phones may require a medium to high communication throughput and may be operated by batteries of relatively low capacity. Therefore, a medium DTIM period, for example a value of 4, may be suitable for these devices.
-Currently, an access point is able to store only a single DTIM period. Consequently, different client devices in power-save mode will all wake up for the same beacon frames according to the DTIM period. Currently, a network manager may need to balance the conflicting requirements for power consumption and communication throughput when in power-save mode of client devices in different wireless networks when configuring the DTIM period of an access point. In the future an access point with support for two or more SSIDs may have SSID-dependent DTIM periods rather than a single DTIM period for all SSIDs. In other words, the network manager may configure the access point with DTIM periods on a per SSID basis. A network manager may consider the requirements of power consumption and communication throughput of client devices in a particular wireless networks when determining which DTIM period to configure for which SSID. A higher DTIM period may increase the potential savings in power consumption but may reduce the communication throughput, and vice versa
Ich werde meine Werte jetzt mal auf beacon=200 und dtim=2 stellen. Mal schauen was sich ändert, vor allem in Bezug auf Video- und Audiostreaming, welches ich ja bzgl. meines Mediaservers sehr stark nutze.
Auf alle Fälle an dieser Stelle nochmals ein GROßES DANKESCHÖN an "holliwood" für diesen Wink!
Der ursprüngliche Beitrag von 14:14 Uhr wurde um 14:21 Uhr ergänzt:
EDIT: Falls es jemand ebenfalls testen möchte (wenn er DD-WRT bzw. OpenWRT benutzt), dann einfach folgende Werte in einer Command-Shell absetzen:
Code:
nvram set wl_bcn="200" ;
nvram set wl0_bcn="200" ;
nvram set wl_dtim="2" ;
nvram set wl0_dtim="2" ;
nvram commit ;
Code:
nvram get "variablenname"Leider bietet bei mir (Atheros Chipsatz) DD-WRT über das WebIf keine Einstellmöglichkeit an. Bei broadcom-basierten Geräten scheint es aber zu gehen!
Mal so zum Vergleich: Meine Fritz!Box 7240 hat folgende Werte: beacon=100 und dtim=0 ! Bin also mal auf den Unterschied gespannt!
Zuletzt bearbeitet:
c/wc/ec)314/0/314 5,0%
