Patent Publication Number: US-2023134830-A1

Title: Device and method for queues release and optimization based on run-time adaptive and dynamic gate control list strategy

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/EP2020/084583, filed on Dec. 4, 2020, the disclosure of which is hereby incorporated by reference in its entirety. 
    
    
     FIELD 
     The present disclosure relates to communication networks, and particularly to the switching of scheduled frames. In order to overcome typical instantaneous network overload conditions, the disclosure describes a controller, an improved network node, and corresponding methods, to implement adaptive and dynamic gate control list (GCL) based on status of network queues. 
     BACKGROUND 
     One problem in network switches, routers. and gateways may be the overload of the internal queues/first-in first-out (FIFO) memories required to buffer (or momentarily store) network frames that flow from ingress ports to egress ports. 
       FIG.  1    and  FIG.  2    both show an example of a set of queues, which can be found in the frame dispatching stage of the Time-Sensitive Networking (TSN) standard 802.1Qbv. TSN is a set of standard-defined mechanisms for the time-sensitive transmission of data over deterministic Ethernet networks. The IEEE 802.1Qbv time-aware scheduler (TAS) is designed to separate the communication on the Ethernet network into fixed length, and repeating time cycles. According to 802.1Qbv, frames to be transferred can be allocated to one of two or more types of traffic classes (priorities). As shown in  FIG.  1    or  FIG.  2   , traffic classes may comprise traffic classes from #0 to #7. Frames are transferred in cycles corresponding to the traffic class, as defined in a gate control list (GCL), to where the data is allocated. Notably, “o” shown in the GCL indicates that a transmission gate corresponding to a particular traffic class is open, and “C” shown in the GCL indicates that a transmission gate corresponding to a particular traffic class is closed. 
     Especially during moments of network overload and traffic burst, it is important that network nodes (e.g., switches/routers/gateways) withstand such peaks of traffic by buffering/storing the frames in internal queues to avoid unexpected frame drops due to lack of capacity, which would degrade the quality of service (QoS) of networks. 
     Most of existing solutions synthesized today in network nodes implement queues of a fixed depth and queue management algorithms per queue. However, given a gateway with N ingress ports and M egress ports, it can occur that, at one particular point in time, some of these ports have low activity (i.e., are quite empty) while other ports are overstressed (i.e., are nearly full). In such conditions, queues of the low activity ports may be unused while queues of other ports are collapsed. This can result in unwanted frame drops. 
     SUMMARY 
     In view of the above-mentioned deficiencies, embodiments of the present disclosure introduce devices and methods to overcome typical instantaneous network overload conditions. In particular, embodiments of the present disclosure avoid frame drops, particularly, the drop of high priority packets, and thus improve QoS in critical network scenarios. An aspect of the present disclosure also optimizes the usage of the total amount of memory devoted to queues. 
     A first aspect of the disclosure provides a controller being configured to: obtain a state of each of a plurality of queues of a network node, wherein the state of a queue is indicative of a utilization of the queue, and wherein each queue is associated with a priority entry; determine, based on the states of the queues, whether the utilization of one or more queues exceeds one or more thresholds, wherein one threshold is associated with each of the plurality of queues; generate one or more new entries for a GCL of the network node that controls the plurality of queues, if one or more thresholds are exceeded; and provide the one or more new entries to the network node. 
     Embodiments of this disclosure accordingly provide a controller for controlling GCL of queues based on the network queues status. The controller may be implemented directly in hardware (like a co-processor or peripheral of a microcontrolleror System-on-Chip (SoC) device, as a part of the network node or the like), and/or in software (as executable code running on a central processing unit (CPU) of that microcontrolleror SoC as a part of the network node or the like). 
     This disclosure relies on the state of each queue. In particular, when a queue reaches a defined threshold (i.e., implying that this queue is full or nearly full), such information may be sent to the controller in order to modify the GCL entries. As previously mentioned, frames are transferred in cycles corresponding to the traffic class as defined in the GCL. In particular, a gate (also named as transmission gate) corresponding to a particular traffic class is controlled to be open or closed, according to the GCL. By modifying the GCL on the fly, gates for overloaded queues (e.g., with high priority) can be set to open, and gates for less loaded or empty queues (e.g., with low priority) can be set to closed. Thus, GCL entries may be modified at runtime, depending on the traffic needs. 
     In an implementation form of the first aspect, the one or more thresholds comprises a first threshold indicative of a nearly full state of a queue. 
     Notably, the one or more thresholds may be configured for instance based on specific requirements. In particular, the mechanism of the adaptive and dynamic GCL may be triggered based on a flag or an event called Queue Nearly Full Alert (QNFA). This may be implemented using the first threshold defined in this implementation. Notably, Queue Full Alert (QFA) may be not used because it is desired to not wait until the queue is full, otherwise this may lead to packets (frames) drop before the mechanism is applied. 
     In an implementation form of the first aspect, the state of the queue is indicative of a quantity of frames in the queue. 
     In an implementation form of the first aspect, the controller is further configured to: determine that the utilization of one or more queues exceeds the one or more thresholds, if a quantity of frames in the queue exceeds the first threshold; and determine one or more first queues from the plurality of queues, wherein for each of the one or more first queues the quantity of frames exceeds the first threshold. 
     Optionally, each of the first queues may be a queue with a higher priority. If a QNFA event is detected by the high priority queue, it may request for more buffer. 
     In an implementation form of the first aspect, the controller is further configured to determine one or more second queues from the plurality of queues, based on one or more default priority entries of the one or more second queues, wherein a default priority entry of each of the one or more second queues is lower than a respective default priority entry of one of the one or more first queues. 
     Accordingly, the controller would thus search for one or more queues with a lower priority. Such low priority queue may need to give its buffer to the high priority queue. 
     In an implementation form of the first aspect, the one or more thresholds comprises a second threshold indicative of a nearly empty state of a queue, and/or a third threshold indicative of an empty state of a queue. 
     The one or more thresholds may be designed to be able to trigger a Queue Nearly Empty Alert (QNEA) event, and/or a Queue empty Alert (QEA) event. 
     In an implementation form of the first aspect, the controller is further configured to determine the one or more second queues from the plurality of queues, based on the one or more default priority entries of the one or more second queues, a state of each of the one or more second queues, and the second threshold or the third threshold, wherein a quantity of frames in each second queue does not exceed the second threshold or the third threshold. 
     For instance, if the state of a queue with a lower priority shows that this queue is empty or nearly empty, this may imply that this queue may have free space in the buffer to be given up (e.g., it may be given to a nearly full high priority queue). 
     In an implementation form of the first aspect, the GCL is responsible for a traffic shaping of frames in each queue, wherein the controller is further configured to generate the one or more new entries for the GCL, wherein a gate for each of the one or more first queues is set to open, and a gate for each of the one or more second queues is set to closed, for the one or more new entries. 
     Optionally, when the nearly full high priority queue, e.g., queue 7 (priority=7), requires buffer and the controller finds a nearly empty or empty low priority queue, e.g., queue 0, (priority=0), a new GCL entry will be generated for queue 0 and queue 7. In particular, a gate for queue 0 is set to closed, while a gate for queue 7 is set to open. 
     In an implementation form of the first aspect, the generated one or more new entries indicates the network node to open a gate for each of the one or more first queues, and to close a gate for each of the one or more second queues. 
     Notably, the GCL determines which traffic queue is permitted to transmit at a specific point in time within the cycle. In particular, after the new GCL entries applied, the high priority queue (e.g., queue 7) is permitted to transmit its frames at a time period that was assigned to queue 0, and thus avoid dropping arriving frames. 
     In an implementation form of the first aspect, the controller is further configured to set a timer for the generated one or more new entries, wherein the generated one or more new entries are active before the timer expires. 
     In particular, the generated one or more new entries of the GCL may be active for a controllable period of time. 
     In an implementation form of the first aspect, the controller is further configured to obtain an updated state of each of the plurality of queues from the network node. 
     In an implementation form of the first aspect, the controller is further configured to set each of the one or more generated GCL entries back to the default GCL entry, if it is determined that the utilization of no queue exceeds the one or more thresholds. 
     Notably, after the high priority queue (queue 7) transmits its burst packets at the time period that was assigned to queue 0, the level in queue 7 (i.e., the utilization of queue 7) may be decreased. If the level is below the QNFA, it means no need to continue to apply this new GCL entry. Thus, the GCL configuration may be set back to the default configuration. 
     A second aspect of the disclosure provides a network device being configured to: provide a state of each of a plurality of queues to a controller, wherein the plurality of queues are formed at an egress port of the network node, wherein each queue is associated with a priority entry; and obtain one or more new entries for a GCL of the network node that controls the plurality of queues, from the controller. 
     Embodiments of the disclosure accordingly also provide a network device, where the adaptive and dynamic GCL implementation allows optimizing the usage of the memory on the network device, and avoiding frames drop in critical network scenarios. The network node may be a switch, router, gateway and the like. In particular, the network node will apply one or more new GCL entries that are obtained from the controller, where the new GCL entries may be determined based on the queue status provided by the network node. 
     In an implementation form of the second aspect, the network device is further configured to replace one or more default entries of the GCL with the obtained one or more new entries. 
     In an implementation form of the second aspect, the network device is further configured to open or close a gate for each of the plurality of queues based on the GCL. 
     As previously described, after the new GCL entry is applied, a nearly full high priority queue may transmit its burst frames at the time period that was assigned to a nearly empty or empty low priority queue. Thus, frame drops in critical network scenarios may be prevented for the high priority queue. 
     In an implementation form of the second aspect, the network device is further configured to provide an updated state of each of the plurality of queues to the controller. 
     As previously described, after the high priority queue transmits frames according to the new GCL entry, the level of the high priority queue may become below the QNFA. The updated state will be provided to the controller. 
     A third aspect of the disclosure provides a method performed by the controller of the first aspect, wherein the method comprises: obtaining a state of each of a plurality of queues of a network node, wherein the state of a queue is indicative of a utilization of the queue, and wherein each queue is associated with a priority entry; determining, based on the states of the queues, whether the utilization of one or more queues exceeds one or more thresholds, wherein one threshold is associated with each of the plurality of queues; generating one or more new entries for a GCL of the network node that controls the plurality of queues, if one or more thresholds are exceeded; and providing the one or more new entries to the network node. 
     Implementation forms of the method of the third aspect may correspond to the implementation forms of the controller of the first aspect described above. The method of the third aspect and its implementation forms achieve the same advantages and effects as described above for the controller of the first aspect and its implementation forms. 
     A fourth aspect of the disclosure provides a method performed by the network node of the second aspect, wherein the method comprises: providing state of each of a plurality of queues to a controller, wherein the plurality of queues are formed at an egress port of the network node, wherein each queue is associated with a priority entry; and obtaining one or more new entries for a GCL of the network node that controls the plurality of queues, from the controller. 
     Implementation forms of the method of the fourth aspect may correspond to the implementation forms of the controller of the second aspect described above. The method of the fourth aspect and its implementation forms achieve the same advantages and effects as described above for the network device of the second aspect and its implementation forms. 
     A fifth aspect of the disclosure provides a computer program product comprising a program code for carrying out, when implemented on a processor, the method according to the third aspect and any implementation forms of the third aspect, or the fourth aspect and any implementation forms of the fourth aspect. 
     It has to be noted that all devices, elements, units and means described in the present application could be implemented in software or hardware elements or any kind of combination thereof. All steps which are performed by the various entities described in the present application as well as the functionalities described to be performed by the various entities are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functionalities. Even if, in the following description of exemplary embodiments, a specific functionality or step to be performed by external entities is not reflected in the description of a specific detailed element of that entity which performs that specific step or functionality, it should be clear for a skilled person that these methods and functionalities can be implemented in respective software or hardware elements, or any kind of combination thereof. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The above described aspects and implementation forms of the present disclosure will be explained in the following description of exemplary embodiments in relation to the enclosed drawings, in which: 
         FIG.  1    shows queues according to 802.1Qbv; 
         FIG.  2    shows queues according to 802.1Qbv; 
         FIG.  3    shows an example of instantaneous status of queues; 
         FIG.  4    shows a controller according to an embodiment of the disclosure; 
         FIG.  5    shows status of queues in a network node, according to an embodiment of the disclosure; 
         FIG.  6    shows a network node according to an embodiment of the disclosure; 
         FIG.  7    shows an example of an IEEE 802.1Qbv implementation according to an embodiment of this disclosure; 
         FIG.  8    shows an example of an IEEE 802.1Qbv implementation according to an embodiment of this disclosure; 
         FIG.  9    shows an example of an IEEE 802.1Qbv implementation according to an embodiment of this disclosure; 
         FIG.  10    shows an example of an IEEE 802.1Qbv implementation according to an embodiment of this disclosure; 
         FIG.  11    shows a hardware implementation according to an embodiment of this disclosure; 
         FIG.  12    shows an algorithm according to an embodiment of this disclosure; 
         FIG.  13    shows a method according to an embodiment of the disclosure; and 
         FIG.  14    shows a method according to an embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION= 
     Illustrative embodiments of a method, device, and program product for controlling release of queues in a network node are described with reference to the figures. Although this description provides a detailed example of possible implementations, it should be noted that the details are intended to be exemplary and in no way limit the scope of the application. 
     Moreover, an embodiment/example may refer to other embodiments/examples. For example, any description including but not limited to terminology, element, process, explanation and/or technical advantage mentioned in one embodiment/example is applicative to the other embodiments/examples. 
     As previously discussed, in an existing solution that implements fixed depth queues and a queue management algorithm per queue, it may happen that queues of the inactive ports are unused (i.e., empty) while queues of other ports are collapsed (i.e., full). 
       FIG.  3    shows an example of an instantaneous status of queues in such a situation. Queue #1 and queue #N both have incoming frames. At time t, frames drop is about to happen in queue #N, due to a lack of space in the queue, even though there is enough empty space in the total queue memory. This may degrade the network QoS. It can be seen that, although the implementation strategy of queue management algorithms per queue and fixed depth queues is quite simple, it is unable to self-adapt to changing traffic conditions. 
     In order to overcome typical instantaneous network overload conditions, this disclosure proposes to implement an adaptive and dynamic GCL based on the status of the network queues. 
       FIG.  4    shows a controller  400  according to an embodiment of the disclosure. The controller  400  may comprise processing circuitry configured to perform, conduct or initiate the various operations of the controller  400  described herein. The processing circuitry may comprise hardware and software. The hardware may comprise analog circuitry or digital circuitry, or both analog and digital circuitry. The digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), digital signal processors (DSPs), or multi-purpose processors. The controller  400  may further comprise memory circuitry, which stores one or more instruction(s) that can be executed by the processor or by the processing circuitry, in particular under control of the software. For instance, the memory circuitry may comprise a non-transitory storage medium storing executable software code which, when executed by the processor or the processing circuitry, causes the various operations of the controller  400  to be performed. In one embodiment, the processing circuitry comprises one or more processors and a non-transitory memory connected to the one or more processors. The non-transitory memory may carry executable program code which, when executed by the one or more processors, causes the controller  400  to perform, conduct or initiate the operations or methods described herein. 
     In particular, the controller  400  is configured to obtain a state  401  of each of a plurality of queues of a network node  410 . The state  401  of a queue is indicative of a utilization of the queue, and wherein each queue is associated with a priority entry. The controller  400  is further configured to determine, based on the states  401  of the queues, whether the utilization of one or more queues exceeds one or more thresholds, wherein one threshold is associated with each of the plurality of queues. Then, the controller  400  is configured to generate one or more new entries  402  for a GCL of the network node  410  that controls the plurality of queues, if one or more thresholds are exceeded. Further, the controller  400  is configured to provide the one or more new entries  402  to the network node  410 . 
     The network device  410  may be a switch, a router, a gateway or the like. The plurality of queues may be implemented on an egress port of the network device  410 . Typically, each queue is configured with an individual transmission class, which represents an internal priority among all queues. For instance, a transmission class #N has a higher priority than a transmission class #N−1, where N being a positive integer. 
     The controller  400  may be implemented directly in hardware (like a coprocessor or peripheral of a Microcontroller or SoC device as a part of the network node  410 ). Optionally, the controller  400  may be implemented in software (as executable code running on a central processing unit or CPU of that Microcontroller or SoC as a part of the network node  410 ). 
       FIG.  5    shows an example of status of queues in the network node  410 , according to an embodiment of the disclosure. In particular, the GCL controller shown in  FIG.  5    may be the controller  400  shown in  FIG.  4   . Possibly, the GCL controller may be a finite state machine (FSM) or an arithmetic logic unit (ALU). 
     The controller  400  as proposed in embodiments of this disclosure relies on the state  401  of each queue. When a queue reaches or exceeds a defined threshold, an event may be triggered and this information is sent to the controller  400 , which allows the controller  400  to modify the entries  402  associated with queues, and thus to modify traffic of outgoing frames. 
     According to embodiments of the disclosure, one or more configurable thresholds may be set for triggering different events. Optionally, the one or more thresholds may comprise a first threshold indicative of a nearly full state of a queue. In particular, the event triggered by the first threshold may be called QNFA. The dash line shown in  FIG.  5    may indicate the first threshold. 
     Possibly, another threshold may be set to trigger a Queue Full Alert (QFA) event, i.e., for indicating that the queue is full. However, this event may not be used because it is desired to not wait until the queue is full, otherwise this may lead to frames drop before the mechanism for adapting GCL is applied. 
     Notably, the state  401  of a queue may be indicative of a quantity of frames in the queue. According to an embodiment of this disclosure, the controller  400  may be configured to determine that the utilization of one or more queues exceeds the one or more thresholds, if a quantity of frames in the queue exceeds the first threshold. Notably, if the quantity of frames in the queue exceeds the first threshold, the QNFA event is triggered. 
     Further, the controller  400  may be configured to determine one or more first queues from the plurality of queues, wherein for each of the one or more first queues the quantity of frames exceeds the first threshold. That is, if a QNFA event is triggered in one queue, this queue will be identified by the controller  400 , here for example it is named as a first queue. Notably, there are be more than one queue that the quantity of frames in the queue exceeds the first threshold. 
     Knowing that there are queues requesting more buffer (i.e., the one or more first queues, since they are nearly full), the controller  400  would accordingly search for one or more other queues with a lower priority. Such low priority queue may need to give its buffer to the high priority queue. 
     According to embodiments of the disclosure, the controller  400  may be further configured to determine one or more second queues from the plurality of queues, based on one or more default priority entries of the one or more second queues, wherein a default priority entry of each of the one or more second queues is lower than a respective default priority entry of one of the one or more first queues. Notably, a second queue should not have a priority or a transmission class higher than a first queue. 
     Possibly, if one or more low priority queues (i.e., the one or more second queues) are found, the controller  400  may modify GCL entries for the high priority queues and the low priority queues (i.e., in this implementation, the one or more first queues and the one or more second queues), in order to make frames in the high priority but overloaded queues to be transmitted first. 
     As previously discussed, the GCL determines which traffic queue is permitted to transmit at a specific point in time within the cycle. In particular, after the new GCL entries applied, the one or more first queues may be permitted to transmit their frames at time periods that was assigned to the one or more second queues, and thus avoid dropping arriving frames. 
     Preferably, the controller  400  would also check whether the low priority queues are capable of receiving additional frames, to avoid frames loss on the low priority queues as well. 
     Optionally, the one or more thresholds may further comprise a second threshold indicative of a nearly empty state of a queue, and/or a third threshold indicative of an empty state of a queue. Notably, the second threshold may be set for triggering a QNEA event, and the third threshold may be set for triggering a QEA event. 
     Accordingly, the controller  400  may be further configured to determine the one or more second queues from the plurality of queues, based on the one or more default priority entries of the one or more second queues, a state of each of the one or more second queues, and the second threshold or the third threshold, wherein a quantity of frames in each second queue does not exceed the second threshold or the third threshold. 
     That is, each of the second queues may be a queue with a priority lower than each of the first queues, and also the state of the second queue should meet certain conditions. In particular, the quantity of frames in each second queue does not trigger a QNFA event or a QFA event. That is, the second queue may have no frame or only a few of frames, thus it is suitable for giving up its chance for transmitting frames (for certain time period). 
     Accordingly, if a suitable low priority queues (i.e., the one or more second queues) are found, the controller  400  may generate new GCL entries  402  for the high priority queues and the low priority queues (i.e., in this implementation, the one or more first queues and the one or more second queues), in order to make frames in the high priority but overloaded queues to be transmitted first by taking the transmit opportunity of other empty or nearly empty low priority queues. 
     In particular, a gate for each of the one or more first queues is set to open, while a gate for each of the one or more second queues is set to closed. Optionally, when the nearly full high priority queue, e.g., queue 7 (priority=7), requires buffer and the controller finds a nearly empty or empty low priority queue, e.g., queue 0, (priority=0), a new GCL entry will be generated for queue 0 and queue 7. In particular, a gate for queue 0 is set to closed, while a gate for queue 7 is set to open. 
     For instance, as the example shown in  FIG.  5   , QNFA events are triggered in queue 7 (i.e., queue for traffic class 7) and queue 6 (i.e., queue for traffic class 6) at T 05 . As default GCL entry for queue 7 is “C”, and a default GCL entry for queue 3 (i.e., queue for traffic class 3) is “o”. The controller  400  may thus modify the GCL entry for queue 7 to be “o”, and the GCL entry for queue 3 to be “C”. In this way, the overloaded queue 7 is able to use the transmit opportunity that was assigned to queue 3, thereby avoiding the drop of high priority frames. This thus improves the QoS in critical network scenarios. 
     Notably, to ensure that the low priority queue that gives up its transmit opportunity also gets a chance to transmit (avoiding a possible frames drop on the low priority), a timer may be set for the new GCL entries. In particular, the new GCL entries may be active for a configurable time period (i.e., before the timer expires). As the example shown in  FIG.  5   , the new GCL entries are only active for T 06  and T 07 . 
     Further, once the outgoing frames being transmitted, the QNFA event may not be triggered anymore for the first queue. That is, the state of the first queue, i.e., the quantity of frames in the queue, may become below the first threshold. 
     According to an embodiment of the disclosure, the controller  400  may be further configured to obtain an updated state of each of the plurality of queues from the network node  410 . Accordingly, the controller  400  may be further configured to set each of the one or more generated GCL entries  402  back to the default GCL entry, if it is determined that the utilization of no queue exceeds the one or more thresholds. 
     Embodiments of this disclosure accordingly also propose a network node  410 . As previously described, the network device  410  may be a switch, a router, a gateway or the like. 
       FIG.  6    shows a network node  410  according to an embodiment of the disclosure. The network node  410  may be the network node  410  shown in  FIG.  4   . The network node  410  may comprise processing circuitry configured to perform, conduct or initiate the various operations of the network node  410  described herein. The processing circuitry may comprise hardware and software. The hardware may comprise analog circuitry or digital circuitry, or both analog and digital circuitry. The digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), digital signal processors (DSPs), or multi-purpose processors. The network node  410  may further comprise memory circuitry, which stores one or more instruction(s) that can be executed by the processor or by the processing circuitry, in particular under control of the software. For instance, the memory circuitry may comprise a non-transitory storage medium storing executable software code which, when executed by the processor or the processing circuitry, causes the various operations of the network node  410  to be performed. In one embodiment, the processing circuitry comprises one or more processors and a non-transitory memory connected to the one or more processors. The non-transitory memory may carry executable program code which, when executed by the one or more processors, causes the network node  410  to perform, conduct or initiate the operations or methods described herein. 
     In particular, the network node  410  is configured to provide a state  401  of each of a plurality of queues to a controller  400 . Possibly, the controller  400  may be the controller  400  shown in  FIG.  4   . Notably, the plurality of queues are formed at an egress port of the network node  410 , wherein each queue is associated with a priority entry. The network node  410  is further configured to obtain one or more new entries  402  for a GCL of the network node  410  that controls the plurality of queue, from the controller  400 . 
     Notably, traffic needs of the network node  410  are provided to the controller  400  at runtime. Relying on status of the plurality of queues, the controller  400  is able to modify on the fly the GCL entries, and thus optimize the usage of the total amount of memory of the network node  410 , which is devoted to queues. 
     According to an embodiment of the disclosure, the network device  410  is configured to replace one or more default entries of the GCL with the obtained one or more new entries. Accordingly, the network device  410  may open or close a gate for each of the plurality of queues based on the GCL. Therefore, outgoing frames of an overloaded higher priority queues may be allowed to be transmitted first. This disclosure aims at avoiding the drop of high priority frames/packets, and thus improving the QoS in critical network scenarios. 
     According to an embodiment of the disclosure, the network device  410  may be further configured to provide an updated state of each of the plurality of queues to the controller  400 . As previously described, after the high priority queue delivered its burst packets, the level of the high priority queue may become below the QNFA. That means, the modified GCL entries may not be needed anymore. The updated state will be provided to the controller  400 , and the controller  400  may accordingly set back the default GCL configuration for the network node  410 . 
       FIG.  7   - FIG.  10    show a specific example of an IEEE 802.1Qbv implementation according to an embodiment of this disclosure, each figure showing status of queues in a chronological order. 
       FIG.  7    shows eight queues of a network node  410 , and status of all the queues. Possibly, the network node  410  is a network node shown in  FIG.  4    or  FIG.  6   . It is assumed that a time cycle of 1 ms comprises eight time-slots, i.e., T 0 , T 1 , . . . , T 7  as shown in  FIG.  7   . Each time-slot is for a dedicated priority, such as T 7  is allocated for the queue with a priority of 7. As previously discussed, each transmission class or traffic class represents a dedicated priority. It is also assumed that a dedicated queue is set for each priority. In this example, the queue for traffic class #7 has the highest priority among all eight queues. 
     Notably, the time cycle is repeated continuously. Order and status of each transmitting gate is defined in a GCL. In particular, at each time-slot transmission gate for each queue will be open or closed according to the GCL. According to embodiments of this disclosure, the the GCL is fixed. 
       FIG.  8    is based on  FIG.  7   , and shows a later time point of all eight queues. Notably, four thresholds for indicating events QFA, QNFA, QNEA and QEA are further illustrated in the figure. It can be seen that a quantity of frames in the queue of traffic class #7 (namely, queue 7) exceeds the threshold for triggering the QNFA event. This indicates a nearly full state of that queue. According to an embodiment of the disclosure, this threshold may be the first threshold defined in the previous embodiments. This information will be provided to a controller  400 , particularly the controller  400  as shown in  FIG.  4    or  FIG.  6   . Therefore, the controller  400  knows that the queue with priority  7  is nearly full, i.e., it requests more buffer, otherwise further arriving frames that with high priority may be dropped. 
     Using the approach defined in the previous embodiments, the controller  400  may determine a low priority queue that accept to give from its buffer. Further, the controller  400  may generate new GCL entries for that low priority queue and the high priority queue, in order to indicate the network node  410  to transmit one or more outgoing frames of queue 7 first. 
       FIG.  9    is based on  FIG.  8   . At the time point shown in  FIG.  9   , the GCL entry of the queue for traffic class #7 (i.e., queue 7) at T 0  has been modified from “C” as shown in  FIG.  8    to “o”. That means, a transmission gate for queue 7 is set to open. At the meanwhile, the GCL entry of the queue for traffic class #0 (i.e., queue 0) at T 0  has been modified from “o” as shown in  FIG.  8    to “C”. That means, a transmission gate for queue 0 is set to closed. 
     Accordingly, the network node  410  open the gate for queue 7. That is, the first time-slot T 0  that was allocated to queue 0 is now allocated to queue 7 (i.e., a “prio 7” frame is transmitted at T 0 ). 
       FIG.  10    is further based on  FIG.  9   . It can be seen that once the outgoing frames being transmitted, the quantity of frames in queue 7 no longer exceed the QNFA threshold. That is, for queue 7, the QNFA event is not triggered anymore. In this way, queue 7 delivers its overloaded frames and thus avoids dropping arriving frames. 
     The updated state of queue 7 (no longer exceed the QNFA threshold) is provided to the controller  400 . Accordingly, the controller  400  restores the default GCL entry setting for queue 0 and queue 7, i.e., the GCL entry of queue 7 at T 0  is set back to “C” and the GCL entry of queue 0 at T 0  is set back to “o”. Therefore, the first time-slot T 0  sends again frames from queue 0 (prio=0). 
       FIG.  11    shows a hardware implementation according to an embodiment of the disclosure. Notably, the different queues will send updates to GCL controller (i.e., the controller  400  as shown in  FIG.  4    or  FIG.  6   ). The updates may concern the following events: QFA, 
     QNFA, QNEA and QEA. 
     High priority queues may be configured in the system via “qmodenTX”, which represents a list of queues requesting more buffer. Low priority queues may be configured in the system via “qmodenRX”, which represents a list of queues accepting to be closed. Further, in order to allow a high flexibility of implementation, a plurality of modes of the mechanism may be configured via “GCLmod”. 
       FIG.  12    shows an algorithm according to an embodiment of the disclosure, based on four different modes:
         Mode “D” (Default): Apply the default GCL without modification   Mode “ME” (Modify Empty): Apply the new GCL only when the target low priority queue is empty   Mode “MNE” (Modify Nearly Empty): Apply the new GCL when the target low priority queue is nearly empty   Mode “JM” (Just Modify): Apply the new GCL regardless the status of the target low priority queues       

     Notably, in different modes, the adaptive and dynamic GCL solution can be implemented differently. For mode “D”, the adaptive and dynamic GCL is not applied. 
       FIG.  13    shows a method  1300  according to an embodiment of the disclosure. In a particular embodiment, the method  1300  is performed by a controller  400  shown in  FIG.  4    or  FIG.  6   . In particular, the method  1300  comprises a step  1301  of obtaining a state  401  of each of a plurality of queues of a network node  410 . Possibly, the network node  410  may be a network node  410  shown in  FIG.  4    or  FIG.  6   . In particular, the state  401  of a queue is indicative of a utilization of the queue, and wherein each queue is associated with a priority entry. The method further comprises a step  1302  of determining, based on the states  401  of the queues, whether the utilization of one or more queues exceeds one or more thresholds, wherein one threshold is associated with each of the plurality of queues. Further, the method  1300  comprises a step  1303  of generating one or more new entries  402  for a GCL of the network node  410  that controls the plurality of queues, if one or more thresholds are exceeded. Then, the method  1300  further comprises a step  1304  of providing the one or more new entries  402  to the network node  410 . 
       FIG.  14    shows a method  1400  according to an embodiment of the disclosure. In a particular embodiment, the method  1400  is performed by a network device  410  shown in  FIG.  4    or  FIG.  6   . In particular, the method  1400  comprises a step  1401  of providing a state  401  of each of a plurality of queues to a controller  400 . Possibly, the controller  400  may be a controller  400  shown in  FIG.  4    or  FIG.  6   . The plurality of queues are formed at an egress port of the network node  410 , wherein each queue is associated with a priority entry. The method  1402  further comprises a step  1402  of obtaining one or more new entries  402  for a GCL of the network node  410  that controls the plurality of queues, from the controller  400 . 
     This disclosure provides for adaptive and dynamic GCL based on the network queues status. Accordingly, embodiments of the disclosure provide a controller and a network node. The innovate controller, i.e., the controller  400 , brings major level of flexibility to the queues, makes network nodes more robust to changes in traffic load conditions. The controller also optimizes the usage of the total amount of memory devoted to queues by modifying on the fly GCL entries. In particular, the GCL entries will be modified at runtime, depending on the traffic needs. Since outgoing frames with high priority having overloaded queues will be transmitted first, this disclosure is able to prevent the drop of high priority packets and to improve thus the QoS in critical network scenarios. 
     The present disclosure has been described in conjunction with various embodiments as examples as well as implementations. However, other variations can be understood and effected by those persons skilled in the art and practicing the claimed invention, from the studies of the drawings, this disclosure and the independent claims. In the claims as well as in the description the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutual different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation. 
     Furthermore, any method according to embodiments of the present disclosure may be implemented in a computer program, having code means, which when run by processing means causes the processing means to execute the steps of the method. The computer program is included in a computer readable medium of a computer program product. The computer readable medium may comprise essentially any memory, such as a ROM (Read-Only Memory), a PROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electrically Erasable PROM), or a hard disk drive. 
     Moreover, it is realized by the skilled person that embodiments of the controller  400  and/or the network device  410  comprises the necessary communication capabilities in the form of e.g., functions, means, units, elements, etc., for performing the solution. Examples of other such means, units, elements and functions are: processors, memory, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selecting units, switches, interleavers, de-interleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiver units, transmitter units, DSPs, trellis-coded modulation (TCM) encoder, TCM decoder, power supply units, power feeders, communication interfaces, communication protocols, etc. which are suitably arranged together for performing the solution. 
     Especially, the processor(s) of the controller  400  and/or the network device  410  may comprise, e.g., one or more instances of a CPU, a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions. The expression “processor” may thus represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above. The processing circuitry may further perform data processing functions for inputting, outputting, and processing of data comprising data buffering and device control functions, such as call processing control, user interface control, or the like.