KR20140047314A - Method and apparatus for managing qos for m2m devices - Google Patents

Abstract

A method for allocating machine-to-machine (M2M) network resources according to an embodiment of the present invention comprises determining available network resources allocated from a gateway to a device; calculating the priority order for managing quality of service (QoS) in each device; and allocating the available network resources according to the calculated priority order. The priority order can be calculated based on a parameter related at least one among the QoS requested in each device; availability based on the number of applications available in each device and a call history; connection fail or success availability based on connection success or fail history in each device; arrival possibility and an available arrival state in each device; and error occurrence possibility based on a data transmission and processing error history in each device. [Reference numerals] (S31) Determine available network resources; (S32) Calculate priority orders in each device; (S33) Allocate resources according to the priority order

Description

METHOD AND APPARATUS FOR ALLOCATING M2M NETWORK RESOURCES

The present invention relates to a network resource allocation method and apparatus for M2M devices in an M2M network, and more particularly, to a method and apparatus for allocating available network resources to each device in a gateway of an M2M network including one gateway and a plurality of M2M devices, To a method and apparatus for allocating network resources according to device-specific priorities.

Machine-to-machine (M2M) networks refer to networks for communication between devices that do not require human interaction. However, this does not mean that human interaction is required for the device for the M2M service, and does not mean that human interaction is not required for the operation of the device.

If M2M in the past and the latter half of the 1990s meant one-to-one or many-to-many communication for simple point-to-point (P2P) connection, then the meaning of M2M communication is gathering information read from sensor or wireless communication module And the communication between the machine and the machine in which the person operates. However, the ultimate goal of M2M communication is to provide a more advanced M2M communication service that operates automatically without human control or with human intervention minimized by individual or contextual situations due to location awareness, context awareness, Quality and stability. M2M network communication can be utilized as an essential infrastructure that can contribute to solving social issues, preventing disasters and disasters, and saving energy through conventional u-City, u-Health, u-transportation, and u-environment projects. A variety of services such as remote meter reading, building and facility management, vending machine management, interior lighting control service, traffic information and vehicle control, emergency dispatch, telematics, and wireless settlement service are provided as M2M services.

While conventional data networks typically provide all network traffic known as "best efforts" services. For example, in a TCP / IP network, the "best effort" service is a default operation in which network nodes indiscriminately drop packets in the face of excessive network congestion. However, in the case of such a "best effort" service, there is no mechanism to ensure reliable delivery of data (i. E. There is no Quality of Service (QoS)).

Also, as the number of devices connected to the network increases, the demand for available bandwidth increases. Likewise, as new applications are developed for use in distributed networking environments, problems associated with management of network resources become significant. For example, a network may experience unsatisfactory performance due to users who are overloading the network, and these demands may result from applications that do not match the network operator's work or other goals. Therefore, solutions to manage data networks using packetized protocols such as TCP / IP have been required to cope with the growing demand, and otherwise, congestion, application inadmissibility, user dissatisfaction, and loss of productivity Lt; / RTI >

Various solutions have been used to address these network management problems. For example, network managers often add or reallocate bandwidth selectively to mitigate congestion. Network operators may also use QoS and policy-based management techniques.

QoS generally refers to resource retention and control mechanisms that ensure a certain level of performance for data flows in accordance with requests from application programs or Internet service provider policies. QoS may not allow certain types of packets to be dropped for example to reduce transmission rates, to establish distinct classes of services for certain types of packets and / or users, to display packets with priority values, and / Can be used.

By combining one or more of these methods, the QoS systems can preferentially handle certain network traffic. For example, referring to U.S. Patent No. 7,274,700 entitled " Router providing differentiated quality of service (QoS) and fast internet protocol packet classifying method for the router " issued on Sep. 25, 2007, And a method of classifying high-speed Internet protocol (IP) packets performed in the router. The router hierarchically divides memory having flow tables into high speed internal cache memory and external dedicated memory. The internal cache memory stores recently retrieved table items. The router preferentially searches the flow tables of the internal cache memory. Only when the internal cache memory search fails, the flow tables of the external memory are searched. As a result, the frequency of the interaction between the packet classifier and the external memory is reduced, thereby improving the speed of packet classification. The patent only illustrates a broader class of prior art handling mechanisms for providing or enforcing QoS policies.

U.S. Patent No. 6,771,661 entitled " Apparatus and Methods for Providing Event-Based Data Communications Device Configuration ", filed on August 3, 2004, entitled " To a system and method for enabling a data communication device to be programmed to automatically and dynamically modify the allocation of resources without having to interrupt sessions. Resource allocation may be achieved by network reservation or by bandwidth reservation provided to the data communication device via individual bandwidth retention messages. The bandwidth allocation information may specify session and future bandwidth modification information, e.g., time or event, of the data communication, which allows the data communication device to modify the amount of bandwidth reserved for the specified session of data communication, And receives bandwidth allocation information indicating future bandwidth allocation modification information associated with a session of data communication. The data communication device may then determine future events, that is, future events that modify the amount of bandwidth that the data communication device will allocate to the session of data communication upon the occurrence of that event. Future events may be determined based on future bandwidth allocation modification information and event information (e.g., time signals from a clock or other event signals). The data communication device may detect the occurrence of a future event in the data communication device and may modify the amount of bandwidth allocated to the session of data communication in the data communication device in response to the detection of the occurrence.

However, despite the network QoS assurance and resource management methods described above, network (e.g., WiFi "hot spots" within a wireless LAN) may be allocated by allocating available resources, such as bandwidth, There is a prominent need for a mechanism for effectively managing and controlling the operation of the system.

It is generally desirable to have access to their network for a variety of different operating environments and in accordance with a number of different network parameters such as type of application, geographic proximity or location (e.g., range), type of wireless air interface And provide flexible control to the network administrator and should not significantly interfere with router or gateway performance due to, for example, latencies associated with management processing. It would also be highly desirable to have the ability to retain resources for users of certain classes.

However, the network resource management method according to the related art as described above can be applied mainly to WAN, LAN, WCDMA, LTE and the like, which is a near-distance and long-distance network, There is a need for a QoS management scheme to ensure stable operation of the network. Because the M2M gateway accepts various kinds of devices, it requests a variety of service qualities to the network depending on the type of application of the connected device, and there is a possibility of causing a network load depending on the data amount of the service quality or the data transmission speed This is because there is a problem. Therefore, there is no comprehensive QoS management method considering various situations occurring in the current M2M network.

Embodiments of the present invention have been made to solve the problems of the prior art as described above, and it is an object of the present invention to provide a method for providing a QoS management method considering characteristics of an M2M network. In this way, M2M network traffic is effectively managed to provide a stable M2M service, so that the normal operation of the device can be ensured so that the user can be provided with the service in a timely manner.

According to another aspect of the present invention, there is provided a method of allocating resources of a machine-to-machine (M2M) network, comprising: determining an available network resource to be allocated from a gateway to a device; Calculating a priority for managing Quality of Service (QoS) for each device; And allocating the available network resources according to the calculated priority.

Here, the priority is: QoS required for each device; Availability based on the number of applications available per device and call history; Connection failure or success based on device-specific connection success or failure history; Reachability and reachability by device; And the possibility of error occurrence based on device-specific data transmission and processing error history.

Also, in order to achieve the above object, the present invention provides an apparatus for allocating resources for an M2M network, the apparatus comprising: a priority calculation unit for calculating a priority for managing quality-of-service (QoS) And a resource allocation unit for allocating available network resources of a device-specific gateway according to the calculated or re-calculated priority.

According to the embodiments of the present invention, when the network resource allocation according to the priority according to the device is implemented in the gateway of the M2M network, the QoS for each device of the M2M is ensured so that most of the devices on the M2M network, It is possible to solve the problem of being delayed by a device having a low importance and guarantee the fairness of the service of each device and improve the performance of the entire M2M network.

For example, a security alarm service can be immediately provided by assigning network resources in an emergency to a device that is urgently required to be connected to the M2M network, such as a security device such as intrusion detection. On the other hand, in the case of a device which is rarely used, such as a fire alarm, it is possible to immediately detect a fire accident by checking the use history and data transmission possibility periodically to find out whether a malfunction has occurred before an accident. Finally, when a defibrillator or a pacemaker, which is a device for lifesaving that is directly connected to human life, must be operated, network resources are immediately allocated for medical data transmission, and information can be received to enable emergency treatment.

Also, since the present invention implements the functions of gateways and devices proposed in the standard document (ETSI TS 102 690 M2M Functional Architecture) by applying or utilizing the functions, any one of the products And can be standardized.

Figure 1 shows a architecture for an M2M service that includes a device and gateway domain and a network domain.
FIG. 2 is a diagram showing a configuration of a device and a gateway domain composed of one gateway and a plurality of devices according to a preferred embodiment of the present invention.
3A to 3C are flowcharts illustrating a method of allocating an M2M network resource according to preferred embodiments of the present invention.
FIG. 4 is a diagram schematically illustrating a configuration of an M2M network resource allocation apparatus according to a preferred embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention, the singular forms may include a plurality of representations, unless the context clearly dictates otherwise . Also, in this specification, the terms "comprises" or "having" are used to specify that a feature, a number, a step, an operation, an element, a component, or a combination thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Machine-to-machine communication differs from conventional human-centered human-to-human communication (H2H) in many aspects. From the difference of these characteristics, the technically necessary technology may vary, and the necessary characteristics may vary slightly depending on the field of application using M2M communication. M2M communication is a paradigm of new communication network in the future, and it offers a variety of convergence services in various industries as well as ubiquitous business beyond existing people-oriented communication.

Currently, research and development for successfully standardizing M2M communication continues in the standardization groups of the world including European Telecommunication Standard Institute (ETSI). FIG. 1 shows ETSI TS (Technical Specification) 102 690 [Machine- to-Machine Communications (M2M); Functional architecture], and the architecture for a M2M service that includes a gateway domain and a network domain.

Referring to FIG. 1, the M2M devices 10 and 10 'are terminals for communicating with no human input or intervention, or minimizing the input and interruption thereof. Type of device.

When the M2M device 10 'directly connects to the access network 40, the M2M application 12 (M2M application) 12' of the M2M device is accessed using the M2M service capability 11 of the M2M device 10 ' And when the M2M device 10 accesses the access network 40 through the M2M gateway 30, the M2M gateway 10 uses the M2M service capability 31 of the M2M gateway 30, 30 of the M2M application 32 are used.

The M2M area network (20) provides a connection between the M2M device (10) and the M2M gateway (30). Examples of the M2M local area network 20 include a Personal Area Network (PAN) or a Wireless Local Area Network (LAN) such as IEEE 802.15.x, Zigbee, Bluetooth, IETF ROLL, ISA100.11a, (LAN), PLC, M-BUS, Wireless M-BSU, and KNX.

The M2M gateway 30 is a gateway that executes the M2M application 32 using the M2M service capability 31 and acts as a proxy between the M2M device 10 and the access network 40. [

The access network 40 is a network that allows the M2M devices 10 'through M2M gateways 30 to communicate with the core network 50. Examples of the access network 40 include xDSL, HFC, FTTH, PLC, Satellite network, GERAN, UTRAN, eUTRAN, Wireless LAN, WiMAX (WiBro) and the like.

The core network 50 is a network that provides IP connectivity, access network control and network service control functions, interconnection with other networks, roaming functions, and the like. Examples of the core network 50 include 3GPP CN, ETSI TISPAN CN, 3GPP2 CN, and IMS.

The M2M service capability 60 of the network domain provides functionality that can be shared by different applications and provides an environment for accessing other service capabilities through an open interface. Using M2M service capabilities, it enables the development and deployment of optimal applications without taking into account the characteristics of the subnetwork layer.

The M2M applications 70 in the network domain run M2M service logic and provide M2M systems with an M2M service capability through an open interface.

Meanwhile, according to FIG. 1, the network domain is defined to include M2M management functions and network management functions. Here, the M2M management functions 80 are configured with all the functions required to manage M2M service capabilities in the network domain, and the management of the M2M devices to the M2M gateway utilizes a specific M2M service capability . Network management functions 90 are also comprised of all the functions required to manage the access network 40 and the core network 50 and include provisioning, supervision, fault management, And the like.

FIG. 2 is a diagram showing a configuration of a device and a gateway domain composed of one gateway and a plurality of devices according to a preferred embodiment of the present invention.

2, a device and a gateway domain to which a preferred embodiment of the present invention is applied include a gateway 30 connected to a network domain 100 and N (where N is an integer of 1 or more) M2M devices 10-1, 10- 2, 10-3, ...., 10-N). At this time, the M2M devices 10-1, 10-2, 10-3, ..., 10-N register, authenticate, and authorize the devices through the service capability (Serveice Capability) Management, provisioning, and the like. The gateway 30 executes the M2M application using the service capability. For example, the gateway 30 has a function of collecting and processing various information data from sensors included in the device, To execute the application.

The available network resources that can be allocated to each device in the gateway of the M2M network as shown in Fig. 1 can be defined as follows.

GW (t) is the amount of available network resources that can be allocated to all of the N M2M devices 10-1, 10-2, 10-3, ..., 10-N from the gateway 30 at a specific time t, (T) / N, and the minimum traffic required for one device is min (D_T (t)), if the required traffic per device is D_T (t) .

이 되어야 한다. In this case, the minimum traffic required by one device must be less than the average network resources that can be allocated per device, and the sum of the minimum traffic required by all devices must be less than the network resources that can be allocated to all N devices. In other words,

.

In this case, the difference [Reserved_GW (t)] of the sum of the network resources allocatable to the N M2M devices and the minimum traffic required by all the devices can be defined as follows.

Here, Reserved_GW (t) will be variable according to the device-specific traffic allocation per hour.

Therefore, the total amount of traffic to be allocated to the device during a specific time (t) is t * D_T (t), and the gateway can control the allocation of available network resources by calculating the device priority by the gateway.

3A is a flowchart illustrating a network resource allocation method for managing QoS of an M2M device according to an embodiment of the present invention.

First, step S31 determines an available network resource to be allocated for each device in the gateway. This determination can be performed in consideration of the available network resources allocatable at the gateway and the minimum traffic required for each device in the domain composed of one gateway and N M2M devices as described above with reference to FIG.

Thereafter, in step S32, the gateway calculates a priority for QoS management for each device in the M2M network. In this case, if it is assumed that a function SORT (D (n)) for calculating priority of N devices is implemented in the gateway for convenience, the SORT function can compute the result by taking the following factors together into consideration:

- QoS required by device

- Number of available (mounted) applications per device and availability based on actual call history

- connection failure or success potential based on device-specific connection success or failure history;

- Device reachable and reachable

- Possibility of error based on device-specific data transmission and processing error history.

Here, the above-mentioned SORT function can be determined by a gateway manager or a program as a policy problem such as giving a weight or the like to each element.

The factors for calculating the SORT function of the above-mentioned priority are the service capability (SC) of the gateway and the device, for example, the above-mentioned ETSI TS (Technical Specification) 102 690 [Machine -to-Machine Communications (M2M); Functional architecture]. According to the standard, M2M Service Capabilities provide capabilities that are exposed to reference points (i.e., interfaces), such as combinations of externally accessible interfaces such as 3GPP, 3GPP2, ETSI TISPAN, etc. The capabilities of the core network can be used and can be accessed via one or more core networks and interfaces. In the above standard, the layer representing the M2M service capabilities in the network domain is referred to as a Network Service Capability Layer (NSCL) and the layer representing the M2M service capabilities of the gateway is referred to as a Gateway Service Capability (Hereinafter referred to as 'GSCL'), and a layer representing M2M service capabilities of the M2M device is defined as a Device Service Capability Layer (DSCL), and NSCL, GSCL, and DSCL And is defined as a service capability layer (SCL).

Each of the M2M applications refers to a device application (DA), a gateway application (GA), and a network application (NA) , Or may be located in a device in which the M2M service function is implemented or in a device in which the service capability is not implemented in the DA.

The SC of the GSCL for calculating the constituent factor of the SORT function for the above-mentioned priority may include the following SC:

A Gateway Application Enablement (GAE) capability that provides functions such as allowing GA and DA to register with the GSCL of the gateway; A gateway generic communication (hereinafter referred to as 'GGC') capability that provides functions such as reporting errors that may occur during message transmission; It manages scheduling information about the reachability status and reachability of devices, and creates, deletes, and queries device groups, stores data of NA / DA / GA and GSCL or NSCL, and sets access rights. Gateway Reachability, Addressing and Repository (GRAR) capability; A Gateway Remote Entity Management (GREM) capability that provides functions such as scheduling remote management tasks for sleeping M2M devices; Gateway History and Data Retention (GHDR) capabilities that provide functions such as recording reference points or messages exchanged within GSCL and related information; And Gateway Transaction Management (GTM) capabilities that provide functions such as collecting the results of individual tasks.

In addition, the SC of the DSCL for calculating the constituent factor of the SORT function for the above-mentioned priority may include the following SC:

A Device Application Enablement (DAE) capability that provides functionality such as allowing the DA to register with the DSCL; Device generic communication (hereinafter referred to as 'DGC') capability to perform functions such as reporting an error that may occur during message transmission; Device Reachability, Addressing and Storage that perform functions such as creating, deleting and querying device groups, storing DA registration information and NSCL information, and delivering device related reachability and scheduling information to NSCL. Repository (DRAR) capability; A Device Remote Entity Management (DREM) capability that provides functions such as triggering connection establishment of the device itself; Device history and data retention (hereinafter referred to as " DHDR ") capability that provides functions such as recording reference points or messages and related information exchanged within the DSCL; Device Transaction Management (DTM) capability that collects the results of individual tasks.

Since the M2M service capabilities considered as a constituent factor of the SORT function according to the preferred embodiment of the present invention utilize the service capability that must be implemented as long as the standard as described above is used, Anyone can apply and standardize any product that complies with the above standards.

A concrete calculation method for each element of the priority calculation formula according to an embodiment of the present invention is as follows.

First, the required QoS for each device can be determined according to a predefined type of device. For example, the level of the network traffic required to provide the M2M service for the device can be classified according to classes such as high / medium / low compared with the entire devices. In addition, the service provided through the M2M network may be a service directly related to human life such as e-health service or fire alarm service. In such a case, the importance of a specific device may be separately considered.

For example, the number of DAs (number_of_registered_DA) stored in the device (number_of_registered_DA) can be compared with the number of available DAs (number_of_registered_DA) number_of_performed_DA), it is possible to calculate the possibility that the corresponding DA is used.

Further, regarding the connection failure or the possibility of success based on the connection success or the failure history based on the device, for example, the number of successful registration (number_of_registered_device) of the device as a history or a failed history (number_of_connection) And the number of successes of connection (number_of_registered_Device).

For example, the presently reachable state of the device is calculated by comparing the state of the Gateway Service Capability Layer (GSCL) and the state of the DSCL (status_of_Device) as shown in the following equation: can do.

Next, as to the probability of occurrence of errors based on device-specific data transmission and processing error history, it is possible to calculate the transmission error occurrence probability based on the device's transaction processing history (number_of_successful_transaction) and message transmission failure history (number_of_transmission_errors) as shown in the following equation.

Referring again to FIG. 3A, in step S33, when the priority for each device is determined according to the SORT function calculated in step S32, device-specific network resources are allocated through device bandwidth adjustment and block / .

The SORT (D (n)) function described above with reference to FIG. 3A can be calculated and applied in the case of the initial M2M network configuration, but when the total number of devices connected to the gateway changes, or when Connection_Timer, It may also be used when reassigning the QoS priority of the device.

FIG. 3B shows a flowchart of a method for reallocating available network resources by re-calculating a priority function to efficiently allocate network resources when the number of all M2M devices connected to a gateway increases or decreases.

Steps S31 to S33 are the same as those described above with reference to Fig. 3A, and a detailed description thereof will be omitted. In step S34, it is determined that the number of M2M devices connected to the M2M gateway has witnessed or decreased. If it is determined that the number of M2M devices has changed, the priority function for allocating network resources is calculated again in step S35, And reassigns available network resources using the calculated priority functions.

FIG. 3C is a flowchart illustrating a method of determining whether a connection timer (Connection_Timer) for confirming a connection state of an M2M device has expired (step S36), re-calculating a priority function every time the connection timer expires (step S37) And reallocates available network resources according to a ranking function. Due to the nature of M2M devices, information transmitted from M2M devices tends to be transmitted only for a short period of time with few messages, so it is necessary to periodically check whether the connection between the gateway and the device is abnormally disconnected. The role of the connection timer (Connection_Timer) in the present embodiment is to periodically check the connection between the gateway and the device abnormally, and to check the idle state of each device. The time period of the connection timer (Connection_timer) may be arbitrarily set according to the characteristics of the M2M service provided by the M2M service provider.

4 is a schematic block diagram of an apparatus for allocating M2M network resources according to an exemplary embodiment of the present invention. The device may be included as part of the M2M gateway, but may be included as a separate entity from the gateway or on a network domain to perform the network resource allocation method as described above.

Referring to FIG. 4, an apparatus for allocating an M2M network resource according to an exemplary embodiment of the present invention includes a priority calculating unit 41 and a resource allocating unit 42. Referring to FIG.

The priority calculation unit 41 according to the present embodiment calculates a priority for QoS-based QoS enhancement when the M2M network configured by one or more M2M devices and M2M gateways is configured for the first time. When the number of all devices connected to the M2M gateway changes, or whenever a predetermined time elapses (for example, each time a predetermined Connection_Timer expires to check the connection status of the devices), the priority calculating unit 41 calculates a priority The priority for QoS management is re-calculated. The priority calculation or re-calculation of the priority calculator 41 may be performed by using the SORT function as described above, implemented in the M2M gateway, for example.

In addition, the resource allocation unit 42 according to the present embodiment adjusts the bandwidth for each device and adjusts bandwidth for each gateway to the gateway according to priority for QoS management for each device, which is calculated or re-calculated by the priority calculating unit 41 Allocate or reallocate device-specific network resources through blocking / permitting.

While the above description has shown, described, and pointed out novel features of the invention as applied to various embodiments, various omissions, substitutions and changes in the form and details of the illustrated apparatus or process are within the scope of the present invention Without departing from the spirit and scope of the invention. The above description is directed to the best contemplated mode of carrying out the present invention. This description is not intended to be exhaustive and should be taken as illustrative of the general principles of the invention. The scope of the invention should be determined with reference to the claims.

10, 10 ', 10-1, 10-2, ..., 10-N: M2M device
30: M2M Gateway

Claims (11)

A method for allocating resources in a machine-to-machine (M2M) network,
Determining available network resources to be allocated from the gateway to the device;
Calculating priorities for device-by-device quality of service (QoS) management; And
And allocating the available network resources according to the calculated priority. The method according to claim 1,
The priority is: QoS required for each device; Availability based on the number of applications available per device and call history; Connection failure or success based on device-specific connection success or failure history; Reachability and reachability by device; And a parameter related to at least one of a possibility of occurrence of errors based on device-specific data transmission and a processing error history. The method according to claim 1,
Confirming a change in the number of devices connected to the gateway;
Restoring a priority according to the changed number of the devices; And
And reassigning the available network resources according to the re-calculated priority. The method according to claim 1,
Releasing the priority order every time a predetermined time elapses; And
And reassigning the available network resources according to the re-calculated priority. 3. The method of claim 2,
Wherein the QoS required for each device is divided into layers according to the types of devices. The method according to claim 1,
Wherein the allocation of the available network resources includes bandwidth adjustment of the device according to the priority or blocking of access by time slot. 3. The method of claim 2,
Wherein the priority is calculated based on a function using the M2M service capability implemented in the gateway and the device. 1. A resource allocation apparatus in a machine-to-machine (M2M) network,
A priority calculator configured to calculate priority for device-by-device quality of service (QoS) management; And
M2M network resource allocation apparatus comprising a resource allocating unit for allocating available network resources of the gateway for each device according to the calculated priority. The method of claim 8,
The priority is: QoS required for each device; Availability based on the number of applications available per device and call history; Connection failure or success based on device-specific connection success or failure history; Reachability and reachability by device; And a parameter related to at least one of a possibility of occurrence of errors based on device-specific data transmission and a processing error history. The method of claim 8,
Wherein the priority calculation unit reassigns the priority whenever the number of the devices connected to the gateway changes or when a predetermined time elapses. The method of claim 8,
Wherein the resource allocation unit allocates the available network resources by adjusting a device-specific bandwidth for the gateway or blocking and allowing access by time slot.

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