KR20090048159A - Method for managing a direct link between stations - Google Patents

Abstract

Direct Link Setup (DLS) Provides a method of managing a direct link that can prevent the DLS link from being released if necessary, even when no data frame is transmitted through the link. According to an embodiment of the present invention, a direct link having a DLS link inactive timer is set between a first station and a second station, and the first station does not include data. That is, the method includes transmitting a NULL data frame (TUN) or Tunneled DLS (TDLS) Keep Alive Management Frame to the second wireless station, wherein the NULL data frame or Tunneled DLS (TDLS) Keep Alive Management Frame is a timeout value of the inactivity timer. It performs a function of preventing the release of the direct link even if there is no transmission of the frame between the first radio station and the second radio station through the direct link during the time of. According to this embodiment of the present invention, when the wireless station that has set up the DLS link is inevitably unable to transmit a data frame through the DLS link, it is possible to prevent the DLS link from being released.

Description

Method for managing a direct link between stations

The present invention relates to a wireless local access network (WLAN), and more particularly, to a method of managing a direct link established between stations (STAs).

Communication in a network in accordance with the IEEE 802.11 standard is assumed to occur within an area called a Basic Service Set (BSS). The boundary is somewhat unclear because the BSS region may vary depending on the propagation characteristics of the wireless medium. These BSSs can be classified into two basic types: Independent BSS (IBSS) and Infrastructure BSS (Infrastructured BSS). The former is distributed as forming a self-contained network. A BSS that does not allow access to a distribution system (DS). The latter includes one or more access points and distributed systems, and generally refers to a BSS for which an access point is used in all communication processes including communication between radio stations. Say.

According to the conventional WLAN standard, in general, the infrastructure BSS does not allow the direct transmission of data between radio stations, but requires transmission of data through an AP. However, the new WLA standard stipulates the Direct Link Setup (DLS) procedure for direct communication between stations with a Quality of Service (QoS). According to this, the QSTA establishes a direct link with the peer QSTA by transmitting and receiving a DLS request frame and a DLS response frame through the legacy AP (QAP) or the legacy AP. If the direct link is established, the QSTA can directly transmit data to the counterpart QSTA using the DLS path without passing through the AP.

When the direct link is established according to the DLS procedure, the QSTA may transmit data using the established direct link, but may also transmit data through QAP as in the prior art. That is, even when the direct link is established, transmission of data using the AP is also allowed. For example, QSTA may use a transmission opportunity (TXOP), etc., if necessary, for data transmission. In this way, even if a direct link is established between two QSTAs, the QSTA can transmit data to the counterpart QSTA using the direct link (DLS path) or via an access point (AP path).

In order to establish a direct link, a first QSTA, which is a station to establish a direct link, first sends a message requesting a direct link setup (DLS) with a second QSTA, that is, a counterpart station, that is, a DLS request frame. When the second QSTA transmits a DLS Response frame including information for accepting the request to the first QSTA, a direct link is established between the first QSTA and the second QSTA. In addition, the established direct link includes a message including a DLS release request transmitted between the first QSTA or the second QSTA, terminated based on the channel environment, or the direct link is inactive due to DLS timeout. May be in a state.

The DLS timeout refers to releasing an established direct link when there is no exchange of frames on the direct link between QSTA peers for a predetermined time set, that is, a DLS Timeout Value. The DLS timeout value is included in the DLS timeout value field of the DLS request frame. Typically, the DLS timeout value field contains a time in seconds. If there is no exchange of frames through the direct link between QSTAs during the time, the direct link is released. If 0 is included in the DLS timeout value field, this indicates that the direct link is never released based on the timeout.

The reason for having such a DLS timeout value field in a DLS request frame is to efficiently use limited channel resources. That is, when there is no frame exchange for a certain time between the QSTAs that set up the direct link, it is assumed that there is no data to be exchanged any more and releases the direct link, so that other QSTAs can be used by the radio resource.

However, according to the procedure of managing the direct link in the current WLAN, unlike the above purpose of having a DLS timeout value field, even if the QSTA inevitably cannot transmit a frame through the direct link during the set time, DLS deactivation is inactive. The expiration of the Inactive Timer may cause the direct link to become inactive. In this case, even though it is necessary to keep the established direct link, it is mistaken as a QSTA peer failure by timeout. For example, the situation of QSTA has changed and a longer timeout time has to be set or another procedure. This may occur due to unavoidable circumstances in which frames cannot be exchanged through the direct link during the specified timeout period.

Accordingly, an object of the present invention is to provide a method for managing a direct link that can prevent the direct link from being released due to the expiration of a DLS inactive timer even though the established direct link must be maintained. will be.

Another object of the present invention is to provide a direct link management method capable of updating a DLS timeout value of a direct link set between QSTAs without transmitting a DLS request frame.

Another problem to be solved by the present invention is to effectively stop the operation of the DLS inactivity timer of the direct link set between QSTA, even if there is no exchange of frames over the direct link within the timeout time set by the DLS request frame. It is to provide a method for managing a direct link that can prevent the direct link from being released.

According to an aspect of the present invention, there is provided a method for managing a direct link between radio stations, using a direct link having a direct link setup (DLS) inactive timer. Station) and a second radio station, wherein the first radio station transmits a data frame that does not contain data to the second radio station, wherein the data frame that does not contain data includes an inactivity timer. It performs a function of preventing the release of the direct link even if there is no transmission of the frame between the first radio station and the second radio station through the direct link during the timeout value.

According to another aspect of the present invention, there is provided a method for managing a direct link between radio stations. The method includes managing a direct link having a direct link setup (DLS) inactive timer. Station) and a second station, wherein the first station transmits a direct link maintenance frame to the second station, wherein the direct link maintenance frame is used for a timeout value of the inactivity timer. It performs a function of preventing the release of the direct link even if there is no transmission of the frame between the first radio station and the second radio station through the direct link.

According to an aspect of the embodiments, the data frame or the direct link maintenance frame that does not contain the data is transmitted over the direct link or access point to which the first radio station and the second radio station are coupled together. Can be sent via According to another aspect of the embodiments, the first radio station may transmit the data frame or the direct link maintenance frame not including the data in the power saving mode. The inactivity timer may also be automatically set to a timeout value stored in the first and second radio stations.

According to the present invention, although the established direct link must be maintained, when the data cannot be transmitted using the DLS path due to the transmission of data using the AP path or the power saving mode, the DLS inactivity timer ( It is possible to prevent the direct link from being released due to the expiration of an Inactive Timer. According to the present invention, the DLS timeout value of the direct link set between QSTAs can be reset or updated without transmitting the DLS request frame. In addition, according to the present invention, by using the NULL data frame or Tunneled Direct Link Setup (TDLS) Keep Alive management frame effectively stops the operation of the DLS inactivity timer of the direct link set between the QSTA, the predetermined preset by the DLS request frame Even if there is no exchange of frames through the direct link within the timeout time, the direct link can be prevented from being released.

According to the current management procedure of a direct link in a wireless LAN, a DLS procedure is specified for direct communication between QSTAs. Only supported However, since direct communication between QSTAs is required even if the legacy AP is not QAP, it is necessary to make DLS service between multiple QSTAs connected to the same AP regardless of whether the AP supports QoS function. There is.

This new DLS service is called TDLS (Tunneled DLS) service. In the TDLS service, a QSTA connected to a legacy AP also establishes a direct link with each other, and can transmit and receive data. In TDLS, all management frames transmitted through the AP are encapsulated in the form of data frames and transmitted to the counterpart QSTA. In other words, in the TDLS, the legacy AP only relays the communication between the QSTAs and does not participate in the procedure of establishing, managing, or releasing a direct link. Therefore, the present invention described below may be applied to a case of TDLS set up not only between QSTAs connected to the QAP but also between QSTAs connected to the legacy AP, and may be particularly useful in TDLS.

In DLS or TDLS services, QSTA is any device that includes Medium Access Control and the Physical Layer interface to the wireless medium that conforms to the IEEE 802.11 standard, and supports DLS. QSTA is a non-access station, a non-AP station, each of which is a wireless transmit / receive unit (WTRU), a user equipment (UE), a mobile station (MS), or a mobile subscriber unit. (Mobile Subscriber Unit) or the like. The AP is a functional entity that has a radio station function and that provides access to distributed services via a wireless medium for an associated station. The AP may be a QAP or a legacy AP that can directly support establishing a direct link between wireless stations. Such an AP may be called a central controller, a base station (BS), a node B, or a site controller.

However, a QSTA that has established a direct link with another QSTA may temporarily stop the direct link while continuously setting the direct link due to an internal factor or an external factor, and thus may not transmit a frame. Temporarily stopping the link here is a direct link, for example, because QSTA enters Power Save Mode to conserve power or is in a mode where service that meets quality of service (QoS) is not available. This may include disabling or not using. As such, when the QSTA enters the power save mode or the like, the exchange of frames through the direct path may not occur within the preset timeout value.

The QSTA may exchange frames using an AP path rather than a DLS path, even if a direct link is established. That is, the QSTA may select a link having a better link quality among the DLS path and the AP path based on the measured and / or obtained link quality, and then transmit a frame using the selected link. For example, the AP path may be determined to have a better link state, and thus, the frame may be transmitted using the AP path rather than the direct link. In such a case, the exchange of the frame through the direct link may not occur within a preset timeout value. have.

In the case of the conventional method, all of these cases are cases in which there is no exchange of frames through the direct link within a predetermined timeout value, which can be mistaken for peer failure. If one of the QSTAs determines that the peer is dropped, the established direct link is released. However, since the release of the direct link is contrary to the intention of the peer STA that set the direct link, it is necessary to prevent the direct link from being automatically released.

As one method of preventing the direct link from being released against the intention of the peer STA, a method of updating the timeout value by transmitting a DLS setup request frame again before timeout of the DLS inactivity timer may be considered. However, according to the radio network management procedure in TDLS, since the DLS setup request frame is defined to be transmitted via the legacy AP, it is not efficient to have the TDLS additionally transmit the DLS setup request frame. In addition, in TDLS, it is not easy to give a high priority to the frame because the management frame is encapsulated and transmitted through the AP.

According to one embodiment of the present invention, a default DLS timeout value may be defined first. The default DLS timeout value has the same function as the timeout value set in the DLS timeout field of an existing DLS setup request frame, but the value is not included in the DLS setup request frame and transmitted, but as a default value to the peer STA. The stored value. That is, when direct is established between two peer STAs, the two peer STAs set a DLS inactivity timer as a stored default DLS timeout value, so that either a peer failure or a link failure occurs on the established direct link. Judge whether or not. In this case, it is preferable to set the default timeout value to a sufficiently large value to prevent a malfunction from occurring in determining whether a link fails.

According to this embodiment of the present invention, since the STA transmitting the DLS setup request message does not need to transmit the DLS timeout value to the counterpart STA in the procedure for establishing the direct link, the DLS setup procedure can be simplified. In addition, the embodiment of the present invention is consistent with the procedure because the same mechanism is applied to the embodiments of the present invention described below which do not use the DLS setup request message in resetting the DLS inactivity timer.

As such, an embodiment of the present invention defining a default DLS timeout value is not necessarily applied to a direct link management procedure according to an embodiment of the present invention described below. That is, in the direct link management procedure according to the embodiment of the present invention, the DLS inactivity timer is set according to a default DLS timeout value or is included in the DLS timeout value field of the DLS setup request frame according to an existing scheme. It can be applied regardless of the case where the DLS inactivity timer is set by the value.

When one of the QSTAs that set up the direct link enters the power save mode and suspends the link, or when the QSTA transmits a frame using the AP path through best path switching, the QSTA transmits to another QSTA. It is desirable to inform this situation. That is, the QSTA needs to inform another QSTA whether the power save mode or the like or the frame transmission path has been switched from the DLS path to the AP path using, for example, a notification frame.

According to an embodiment of the present invention, if a special situation occurs in which one frame cannot transmit a frame by using a direct link, but it is necessary to keep the established direct link, this intention is informed to the other QSTA. Update the set timeout value or disable the DLS inactivity timer. For example, the preset timeout value can be updated using a data frame that contains no data (hereinafter referred to as a NULL data frame) or a new type of management frame that prevents the DLS link from being released. Alternatively, you can disable the DLS inactivity timer. According to this embodiment of the present invention, the DLS inactivity timer configured with the default timeout value may be operated between peer STAs that set the direct link without including the DLS timeout field value in the DLS setup request frame. .

According to this embodiment of the present invention, it is possible to prevent the established direct link from being released against the QSTA's intention without further transmitting a DLS request frame. In particular, according to an embodiment of the present invention, the DLS inactivity timer may be reset using a NULL data frame or a new type of management frame (eg, TDLS Keep Alive Management Frame). According to an aspect of an embodiment of the present invention, the DLS inactivity timer operates according to the DLS timeout value which is set to a sufficiently large value by default between peer QSTAs that set the DLS, so that the DLS timeout value in the DLS setting procedure. No need to exchange

EMBODIMENT OF THE INVENTION Hereinafter, this Example of this invention is described in detail with reference to an accompanying drawing.

1 is a message flowchart for explaining a management procedure of a direct link between radio stations according to a first embodiment of the present invention. 1 is a case where the first radio station 10 and the second radio station 20 transmit data through a DLS path.

Referring to FIG. 1, first, a direct link is established between the first radio station STA1 and 10 and the second radio station STA2 and 20 (S101). There is no particular limitation on the method for establishing the direct link. For example, the direct link may be established using the DLS procedure or the Tunneled DLS (TDLS) procedure defined in the IEEE 802.11 standard. The direct link may be established at the request of the first radio station 10 or at the request of the second radio station 20. As such, when a direct link is established between the first radio station 10 and the second radio station 20, the timeout value negotiated during the direct link setup process (that is, the timeout value included in the DLS setup request frame). Or or by default timeout value, the DLS inactivity timer is set.

Then, the data frame and / or the acknowledgment frame are exchanged between the first radio station 10 and the second radio station 20 through the established direct link (S102). When there is a transmission of a data frame and / or an acknowledgment frame for the transmission of the data frame through the established direct link before the time of the DLS inactivity timer expires, the DLS inactivity of the first radio station 10 and the second radio station 20 is transmitted. Each timer is reset and starts running again from the beginning.

If there is no data to be transmitted through the established direct link but wants to maintain the direct link, the first radio station 10 or the second radio station 20 transmits a NULL data frame to the other station (S103). In FIG. 1, the first radio station 10 transmits a NULL data frame to the second radio station, but vice versa. The NULL data frame is to prevent the DLS inactivity timer from expiring, so it must be transmitted before the running DLS inactivity timer expires. For example, it can be set to send a NULL data frame a few seconds before the DLS inactivity timer expires. The exact time or method is not particularly limited.

The second radio station 20 or the first radio station 10 having received the NULL data frame transmits an acknowledgment frame to the other party (S104). The acknowledgment frame may be, for example, an ACK frame. In the present invention, since the DLS link is maintained between the peer radio stations 10 and 20, it is preferable to transmit an acknowledgment frame.

As such, after the exchange of the NULL data frame and the acknowledgment frame therefor between the peer radio stations 10, 20, the DLS inactivity timer at the peer radio stations 10, 20 ceases operation and is reset again. . As a result, according to the embodiment of the present invention, even if there is no data to be transmitted, by transmitting a NULL frame, the established DLS link can be prevented from being released.

Is a method of updating a timeout value of a DLS inactivity timer by using a notification frame including a DLS timeout value field. When there is no frame transmitted through the DLS path and can be mistaken for the dropout of the peer STA, for example, the QSTA enters a power saving mode or the like, or switches a path from one link to another. Therefore, by including the DLS timeout value field in a frame that must be transmitted for both operations, such as a link suspension notification frame or a best path switch notification frame, The timer may be set to a value greater than the preset DLS inactivity timer to prevent the release of the direct link due to the passage of the preset time. Here, the preset DLS inactivity timer may be a timer set by a DLS request frame or a timer newly set according to the present embodiment.

1 is a block diagram showing an example of a frame format including a DLS timeout value field according to the first embodiment of the present invention, which is an example of a format of a link pause notification frame or a best path switch notification frame. Hereinafter, each of the cases in which the frame format shown in FIG. 1 is the link pause notification frame or the best path switch notification frame will be described in detail.

2 is a message flow chart for explaining a direct link management procedure between wireless stations according to a second embodiment of the present invention. 2 illustrates that the first radio station 10 and the second radio station 20 establishing a DLS link transmit data through an AP path instead of the DLS path, or the first radio station 10 and the second radio station ( In this case, at least one of the wireless stations operates in the power saving mode. The following description will focus on differences from the first embodiment.

Referring to FIG. 2, first, a direct link is established between the first radio station STA1 and 10 and the second radio station STA2 and 20 (S201). There is no particular limitation on the method for establishing the direct link. For example, the direct link may be established using the DLS procedure or the Tunneled DLS (TDLS) procedure defined in the IEEE 802.11 standard. As such, when a direct link is established between the first radio station 10 and the second radio station 20, the timeout value negotiated during the direct link setup process (that is, the timeout value included in the DLS setup request frame). Or or by default timeout value, the DLS inactivity timer is set.

The first and second radio stations 10 and 20 negotiate to transmit data through the AP path rather than the DLS path before the data frame is exchanged or the data frame is exchanged through the established DLS link. By performing the switching procedure for the frame transmission path or informs the other station of the at least one of the first and second radio stations (10, 20) to use the power saving mode (S202).

In the former case, that is, when it is decided to switch to the AP path, the data frame and / or the acknowledgment frame are exchanged between the first radio station 10 and the second radio station 20 via the AP path (S203). In this case, when there is a transmission of a data frame and / or an acknowledgment frame for it through the AP path before the time of the DLS inactivity timer expires, the first radio station 10 and the second radio station 20 Each DLS inactivity timer is reset and starts running again from the beginning.

Subsequently, when there is no data to be transmitted to the counterpart of the established direct link or enters the power saving mode as in the latter case, the DLS inactivity timer may expire. In this case, the first radio station 10 or the second radio station 20 transmits a NULL data frame to the counterpart radio station through the AP path (S204). The NULL data frame may be transmitted through the AP path (if the AP path is selected in step S202) or may be transmitted through the DLS link. 2 shows that the first radio station 10 transmits a NULL data frame to the second radio station, but the reverse is also possible. Since these NULL data frames are intended to prevent the DLS inactivity timer from expire, they should be sent before the working DLS inactivity timer expires.

In operation S205, the second radio station 20 or the first radio station 10 having received the NULL data frame transmits an acknowledgment frame to the other party through the AP path. The acknowledgment frame may be, for example, an ACK frame. In the present invention, since the DLS link is maintained between the peer radio stations 10 and 20, it is preferable to transmit an acknowledgment frame.

As such, after the exchange of the NULL data frame and the acknowledgment frame therefor between the peer radio stations 10, 20, the DLS inactivity timer at the peer radio stations 10, 20 ceases operation and is reset again. . As a result, according to the embodiment of the present invention, even if there is no data to be transmitted, by transmitting a NULL frame, the established DLS link can be prevented from being released.

3 is a message flow chart for explaining a direct link management procedure between wireless stations according to a third embodiment of the present invention. In the third embodiment shown in FIG. 3, like the second embodiment, the first radio station 10 and the second radio station 20 that have established a DLS link transmit data through an AP path instead of the DLS path, or At least one of the first radio station 10 and the second radio station 20 operates in a power saving mode. However, the third embodiment differs from the second embodiment in that a DLS link maintenance frame (for example, a TDLS Keep Alive Management Frame) is used instead of a NULL data frame. The following description will focus on differences from the first and second embodiments.

Referring to FIG. 3, first, a direct link is established between the first radio station STA1 and 10 and the second radio station STA2 and 20 (S301). When a direct link is established between the first radio station 10 and the second radio station 20, a timeout value (ie, a timeout value included in the DLS establishment request frame) negotiated during the establishment of the direct link or a default value. By the timeout value, the DLS inactivity timer is set. The first and second radio stations 10 and 20 negotiate to transmit data through the AP path rather than the DLS path before the data frame is exchanged or the data frame is exchanged through the established DLS link. By performing the switching procedure for the frame transmission path or at least one of the first and second radio stations (10, 20) to inform the other station of the radio station to use in the power saving mode (S302).

In the former case, that is, when it is determined to switch to the AP path, the data frame and / or the acknowledgment frame are exchanged between the first radio station 10 and the second radio station 20 through the AP path (S303). . In this case, when there is a transmission of a data frame and / or an acknowledgment frame for it through the AP path before the time of the DLS inactivity timer expires, the first radio station 10 and the second radio station 20 Each DLS inactivity timer is reset and starts running again from the beginning.

Subsequently, when there is no data to be transmitted to the counterpart of the established direct link or enters the power saving mode as in the latter case, the DLS inactivity timer may expire. In this case, the first radio station 10 or the second radio station 20 transmits a DLS link maintenance frame, for example, a TDLS Keep Alive Management Frame, to the other station (S304).

The TDLS keep Alive Management Frame may be transmitted through the AP path (if the AP path is selected in step S202) or may be transmitted through the DLS link. In FIG. 2, the first radio station 10 transmits the TDLS keep Alive Management Frame to the second radio station, but the reverse is also possible. Since the TDLS keep Alive Management Frame is to prevent the DLS inactivity timer from expire, it should be transmitted before the working DLS inactivity timer expires.

4 shows an example of information included in a TDLS keep Alive Management Frame. Referring to FIG. 4, the TDLS keep Alive Management Frame 400 includes at least a Link Identifier Element 410 and a Dialog Token 420. The link identifier information 410 includes an element ID field (Element ID 411), a length field (Length, 412), a basic service set ID field (BSS ID, 413), a source address field (Source Address, 414), and a destination address. Field (Destination Address, 415), regulatory class field (Regulatory Class, 416), and channel number field (Channel Number, 417).

The element ID field 411 may be set to a value indicating that it is a link identifier element, and the length field may be set to a value in bytes, for example, 20 indicating the length of the link identifier element 410. The basic service set ID field 413 is set to the ID of the BSS to which the radio stations 10 and 20 are currently joined, and the source address field 414 is set to the medium access control (MAC) address of the transmitting station. The address field 415 is set to the MAC address of the target radio station. The regulatory class field 416 is set to regulatory class information for the current combination of radio stations, and the channel number field 417 is set to the channel number to which the radio station is currently combined.

After receiving the TDLS keep Alive Management Frame, the second radio station 20 or the first radio station 10 transmits an acknowledgment frame to the other party (S305). The acknowledgment frame may be, for example, an ACK frame. In the present invention, since the DLS link is maintained between the peer radio stations 10 and 20, it is preferable to transmit an acknowledgment frame.

As such, after the exchange of the TDLS keep Alive Management Frame and the acknowledgment frame therefor is performed between the peer radio stations 10 and 20, the DLS inactivity timer in the peer radio stations 10 and 20 stops operation, and again. It is reset. As a result, according to the embodiment of the present invention, even if there is no data to be transmitted, by transmitting a NULL frame, the established DLS link can be prevented from being released.

The embodiments of the present invention described in detail above are merely illustrative of the technical idea of the present invention, and should not be construed as limiting the technical idea of the present invention by the embodiments. The protection scope of the present invention is specified by the claims of the present invention described later.

1 is a message flowchart for explaining a management procedure of a direct link between radio stations according to a first embodiment of the present invention.

2 is a message flow chart for explaining a direct link management procedure between wireless stations according to a second embodiment of the present invention.

3 is a message flow chart for explaining a direct link management procedure between wireless stations according to a third embodiment of the present invention.

4 is a block diagram illustrating an example of a Tunneled Direct Link Setup (TDLS) Keep Alive management frame format.

Claims (6)

A direct link having a direct link setup (DLS) inactive timer is set between the first station and the second station, The first radio station transmitting a data frame that does not contain data to the second radio station, A data frame that does not contain the data has a function of preventing release of the direct link even if there is no transmission of the frame between the first radio station and the second radio station through the direct link during the timeout value of the inactivity timer. And managing direct links between wireless stations. A direct link having a direct link setup (DLS) inactive timer is set between the first station and the second station, The first radio station transmitting a direct link maintenance frame to the second radio station, The direct link maintenance frame performs a function of preventing the release of the direct link even if there is no transmission of the frame between the first radio station and the second radio station through the direct link during the timeout value of the inactivity timer. And managing direct links between stations. The access point according to claim 1 or 2, wherein the data frame or the direct link maintenance frame, which does not contain the data, is transmitted through the direct link, or an access point in which the first radio station and the second radio station are combined together. And managing a direct link between wireless stations. 3. The direct link between radio stations according to claim 1 or 2, wherein the first radio station transmits a data frame or the direct link maintenance frame not including the data in a power saving mode. How to manage. 3. A method according to claim 1 or 2, wherein the inactivity timer is automatically set to a timeout value stored in the first and second radio stations. 3. The method of claim 2, wherein the direct link maintenance frame is a Tunneled Direct Link Setup (TDLS) Keep Alive management frame, and the TDLS Keep Alive management frame includes a link identifier element and dialog token information. How to manage direct links.

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