Packet Transmission Control Method and Apparatus for a PTN Access Node in an ITS Communication Network

Abstract

A method for controlling packet transmission at a PTN access node for an ITS communication network and an apparatus for the same are disclosed. A packet transmission control method according to an embodiment of the present invention may include: a step of classifying into a plurality of service classes including control traffic and video traffic based on the header and service identifier of a received frame; a step of receiving traffic event metadata including signal cycles, conflicting traffic events, and priority signal events from a control policy server; a step of generating scheduling parameters including time slot allocation parameters for a control traffic queue and weight adjustment parameters for a video traffic queue based on the metadata; a step of calculating a microburst indicator based on frame inflow characteristics in a short-time observation window, and determining the output order by performing queue management and scheduling control for a queue by service class according to the scheduling parameters and the microburst indicator; a step of transmitting by applying a predetermined transmission encapsulation according to a service identifier; and a step of maintaining an independent protection domain for each service and performing linear or ring protection switching only for the corresponding service when a threshold is exceeded based on an OAM performance indicator for each service.

Description

Technology Field

[0001] The present invention relates to a method for controlling packet transmission at a Packet Transport Network (PTN) access node for an Intelligent Transportation System (ITS) communication network and an apparatus for the same. Background Technology

[0002] The content described in this section merely provides background information regarding embodiments of the present invention and does not constitute prior art.

[0003] In urban transportation infrastructure, numerous field terminals—such as signal controllers, various detectors (sensors), Roadside Units (RSUs), and Closed-Circuit Television (CCTV) systems—are distributed to exchange control and monitoring data with control centers. Recently, there has been a trend toward adopting Ethernet-based Packet Transmission Networks (PTNs) for these communications, providing transmission services equipped with operator-grade operation, management, and protection switching functions.

[0004] Packet Transport Networks (PTNs) can be implemented as Multiprotocol Label Switching - Transport Profile (MPLS-TP) or Carrier Ethernet (e.g., IEEE 802.1ad VLAN Stacking, QinQ; Ethernet Virtual Private Network, EVPN) and provide point-to-point and multipoint connections through standard service models of the Metro Ethernet Forum (MEF), such as E-Line, E-LAN, etc.

[0005] In addition, it performs connectivity checks (CC) and measures latency, jitter, and frame loss using OAM (Operations, Administration and Maintenance) based on IEEE 802.1ag and ITU-T Y.1731, and supports Ethernet Ring Protection Switching (ERPS) and 1+1 or 1:1 linear protection. For time alignment, a configuration that runs in parallel with the Precision Time Protocol (PTP, IEEE 1588v2) and Synchronous Ethernet (SyncE) is common.

[0006] In ITS applications, control traffic originating from signal controllers and RSUs has a small payload but requires very strict latency and jitter tolerances and high priority in emergency situations. On the other hand, video traffic has high bandwidth requirements and exhibits burst characteristics due to large instantaneous bitrate fluctuations caused by Group of Pictures (GOP) boundaries or scene transitions. When this traffic mixes at field premises switches and aggregates to PTN access nodes, microbursts frequently occur, characterized by a surge in output queues over short time windows ranging from hundreds of microseconds to a few milliseconds. This is easily triggered by factors such as GOP concurrency of multiple cameras, simultaneous event occurrences within the same phase, Transmission Control Protocol (TCP) incasts, and simultaneous uploads to storage or analysis servers.

[0007] Conventional QoS provides service differentiation by combining Differential Services (DiffServ)-based classification, Strict Priority scheduling, Weighted Round Robin (WRR) or Deficit Round Robin (DRR), and single-token bucket-based policing and shaping. However, since it is difficult for schedulers to directly reflect time patterns unique to the ITS domain, such as traffic signal cycles (Cycle / Offset / Split), conflicting phase transitions, and priority signal occurrences, delays and jitter in control traffic can increase during sensitive periods like phase transitions. Furthermore, if a microburst occurs within the same egress, queue depth spikes even in high-priority queues, leading to increased head-of-line delays. In particular, this increases queuing jitter for time-synchronized packets, such as PTPs, which can result in a degradation of synchronization precision across the entire network. Furthermore, in environments where delay-sensitive control traffic and bandwidth-intensive video traffic coexist, it is difficult to guarantee stable delay and jitter at short time scales ranging from hundreds of microseconds to milliseconds, and it is challenging to simultaneously achieve ultra-short burst absorption and time-aligned priority processing using only a single token bucket and general weighted scheduling.

[0008] Furthermore, there are limitations in terms of protection operations. Conventional PTN ring and linear protection often operate within a public protection domain, such as physical links, ports, and VLAN trunks. Consequently, if performance degradation or a fault in a specific service (e.g., video) triggers a protection failover, it can lead to the unintended consequence of other services (e.g., control) within the same domain being failed as well. Conversely, even if performance deterioration occurs only in the control service, there is a risk that a timely failover may not be triggered if the public threshold is not exceeded. Additionally, if OAM is not configured as an independent session for each service, it is difficult to set differential monitoring cycles and thresholds tailored to the operational characteristics differences between control and video. The problem to be solved

[0009] The main objective of the present invention is to provide a method for controlling packet transmission at a PTN access node for an ITS communication network and an apparatus therefor, which perform precision delay guarantee, scheduling, and service-specific protection switching of the PTN access node using traffic metadata and burst indicators. means of solving the problem

[0010] According to one aspect of the present invention, a method for controlling packet transmission at a PTN access node for an ITS communication network to achieve the above objective comprises: a step of classifying into a plurality of service classes including control traffic and video traffic based on the header and service identifier of a received frame; a step of receiving traffic event metadata including signal cycles, conflicting traffic events and priority signal events from a control policy server; a step of generating scheduling parameters including time slot allocation parameters for a control traffic queue and weight adjustment parameters for a video traffic queue based on the metadata; a step of calculating a microburst indicator based on frame inflow characteristics in a short-time observation window, and determining an output order by performing queue management and scheduling control for a queue by service class according to the scheduling parameters and the microburst indicator; a step of transmitting by applying a predetermined transmission encapsulation according to a service identifier; and a step of maintaining an independent protection domain for each service and performing linear or ring protection switching only for the corresponding service when a threshold is exceeded based on an OAM performance indicator for each service.

[0011] In addition, according to another aspect of the present invention, a PTN access node for controlling packet transmission for an ITS communication network to achieve the above objective comprises: a forwarding classification processing unit configured to classify into a plurality of service classes, including control traffic and video traffic, based on the header and service identifier of a received frame and map to a class-specific queue; a traffic event interlocking unit configured to receive traffic event metadata, including signal cycles, conflicting traffic events, and priority signal events, from a control policy server, and to generate scheduling parameters, including time slot assignment parameters for a control traffic queue and weight adjustment parameters for a video traffic queue, based on said metadata; a traffic-specific QoS scheduling processing unit configured to calculate a microburst indicator based on frame inflow characteristics in a short-time observation window, and to determine the output order by performing queue management and scheduling control for service-specific queues according to said scheduling parameters and said microburst indicator; and a transmission encapsulation processing unit configured to transmit a frame by applying a predetermined transmission encapsulation according to a service identifier. It may include a service-specific protection domain control unit configured to maintain independent protection domains for each service and configured to perform linear or ring protection switching only for the relevant service when a threshold is exceeded based on OAM performance indicators for each service. Effects of the invention

[0012] As explained above, the present invention has the effect of stably suppressing delay and jitter of control traffic even in short intervals of hundreds of microseconds to several milliseconds and maintaining the synchronization precision of the Precision Time Protocol (PTP) through time slot assignment based on traffic event metadata and microburst indicator-linked scheduling.

[0013] In addition, the present invention separates control (E-Line) and video (E-LAN) into independent protection domains for each service and selectively performs linear protection or ring protection switching based on service-specific OAM performance indicators and thresholds, thereby preventing unnecessary concomitant switching and improving the availability and recovery reliability of the control service, while simultaneously reducing the excessive occurrence of operational alerts. Brief explanation of the drawing

[0014] FIG. 1 is a block diagram schematically showing a PTN-based ITS transmission system according to an embodiment of the present invention. FIG. 2 is a block diagram schematically showing a PTN access node according to an embodiment of the present invention. FIG. 3 is a flowchart illustrating the processing operation of an ITS transmission system according to an embodiment of the present invention. FIG. 4 is a flowchart illustrating a packet transmission control method at a PTN access node according to an embodiment of the present invention. Specific details for implementing the invention

[0015] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, detailed descriptions of related known configurations or functions are omitted if it is determined that such detailed descriptions may obscure the essence of the present invention. Furthermore, while preferred embodiments of the present invention will be described below, the technical concept of the present invention is not limited or restricted thereto and can be modified and implemented in various ways by those skilled in the art. Hereinafter, with reference to the drawings, a packet transmission control method at a PTN access node for an Intelligent Transportation System (ITS) communication network and an apparatus for the same proposed in the present invention will be described in detail.

[0016] FIG. 1 is a block diagram schematically showing a PTN-based ITS transmission system according to an embodiment of the present invention.

[0017] The ITS transmission system (10) according to the present embodiment includes a packet transport network (PTN) (100), a plurality of sales offices including field terminals and PTN access nodes (110), a control policy server (300), and a PTN management system (500). The ITS transmission system (10) of FIG. 1 is according to one embodiment, and not all blocks shown in FIG. 1 are essential components, and some blocks included in the ITS transmission system (10) in other embodiments may be added, changed, or deleted.

[0018] A packet transport network (PTN) (100) includes a plurality of PTN core nodes (120a, 120b) and is connected to PTN access nodes (110a, 110b) deployed at each site via lines (12a, 12b). The lines (12a, 12b) may be laid along optical cable communication conduits (20, 30), for example, and the conduit identifiers (20, 30) may differ or be interchangeable depending on the implementation.

[0019] An internal L2 / L3 switch is installed at each branch office (site). Traffic generated from the field terminals—signal controller (200), sensor (210), roadside unit (RSU) (220), and closed-circuit television (CCTV) (230)—is collected by the switch and then transmitted to the corresponding PTN access node (110). Here, PTN access nodes (110a, 110b, ..., 110n) may be installed for each branch office.

[0020] The PTN access nodes (110a, 110b) perform service classification based on the header and service identifier of the received frame according to the internal configuration shown in FIG. 2, link traffic event metadata, perform Quality of Service (QoS) scheduling and transmission encapsulation, and then transmit to the PTN transmission network (100).

[0021] In this embodiment, the service is operated by dividing it into control service and video service. For example, control traffic may be configured as an E-Line (point-to-point) in the form of an Ethernet Virtual Connection (EVC) mapped to Virtual LAN 600, and video traffic may be configured as an E-LAN ​​(multi-point) mapped to Virtual LAN 61X. The above Virtual LAN number and EVC type are examples for illustrative purposes only and may be replaced with other identifiers or variations such as E-Tree depending on the operator's policy.

[0022] The control policy server (300) generates traffic event metadata including signal cycles (Cycle / Offset / Split), conflicting traffic events, and priority signal events, and distributes them to the PTN transmission network (100) and PTN access nodes (110) through a management policy path.

[0023] The PTN access node calculates scheduling parameters, including time slot allocation parameters for control traffic queues and weight adjustment parameters for video traffic queues, based on received metadata. Additionally, the PTN access node calculates a microburst metric based on frame inflow characteristics in short-time viewing windows and determines the output order by combining the metric with the scheduling parameters to perform queue management and scheduling control by service class.

[0024] According to an embodiment of the present invention, dual token bucket-based shaping, gating of signal phase transition intervals, and hybrid scheduling combining Priority Queuing (PRIQ) and Weighted Round Robin (WRR) or Deficit Round Robin (DRR) may be applied to the control service. Additionally, delay-based Active Queue Management (AQM) is applied to the video service to suppress congestion by performing frame discarding or marking when queue delay exceeds a threshold.

[0025] The PTN access node (110) transmits a frame by applying a predetermined transport encapsulation according to the service identifier. Here, depending on the implementation, the encapsulation method may be configured as one or more of the Label Switched Path (LSP) or Pseudowire (PW) of the Multiprotocol Label Switching - Transport Profile (MPLS-TP), or QinQ (IEEE 802.1ad VLAN Stacking), which is a dual tagging method.

[0026] The PTN management system (500) performs operations, administration and maintenance (OAM) and network management functions. Specifically, the PTN management system (500) establishes and monitors connectivity check (CC) and performance measurement (latency, jitter, frame loss) sessions for each service, and if the performance indicators exceed a threshold, it directs linear protection (1+1 or 1:1) or ring protection (ERPS: Ethernet Ring Protection Switching) only for the corresponding service while maintaining an independent protection domain for each service.

[0027] Additionally, the PTN management system (500) collects telemetry such as queue occupancy, microburst indicators, and OAM results from the PTN access node (110), and performs remote updates of policies or schedule parameters as needed. If necessary, Precision Time Protocol (PTP: IEEE 1588v2) and Synchronous Ethernet (SyncE: Synchronous Ethernet) may be applied in parallel for precise time synchronization, and synchronization information is distributed to the scheduling processing unit and the transmission encapsulation processing unit through the time synchronization processing unit inside the PTN access node.

[0028] In FIG. 1, the solid line represents the user data path. Traffic generated from the field terminal is transmitted to the PTN access node via the premises switch and then sent to the PTN transmission network. The dotted line represents the management policy path, and management traffic such as policies, metadata distribution, OAM and management session setup, and telemetry collection is transmitted through this path. In this way, control traffic and video traffic are separated by service at the PTN access node and transmitted through the PTN transmission network, and the control policy server (300) and the PTN management system (500) interact with each node through the path shown by the dotted line.

[0029] Meanwhile, in the ITS transmission system (10), the number of sales offices and PTN access nodes (110), the number and arrangement of core nodes of the PTN transmission network (100) (e.g., the number and phase of 120a, 120b), the redundancy method of the lines (12a, 12b), the encapsulation method (MPLS-TP LSP / PW or QinQ), and the protection method (linear or ring) may be varied depending on the network scale and operation policy. The configuration illustrated in FIG. 1 is an example to explain the technical concept of the present invention, and various variations are possible to achieve the same purpose.

[0030] FIG. 2 is a block diagram schematically showing a PTN access node according to an embodiment of the present invention.

[0031] The PTN access node (110) according to the present embodiment may include a forwarding classification processing unit (401), a traffic event linkage unit (430), a traffic-specific QoS scheduling processing unit (450), a transmission encapsulation processing unit (480), a service-specific protection domain control unit (460), a time synchronization processing unit (470), and a remote management agent unit (490). The PTN access node (110) of FIG. 2 is according to one embodiment, and not all blocks shown in FIG. 2 are essential components, and some blocks included in the PTN access node (110) in other embodiments may be added, changed, or deleted.

[0032] The PTN access node (110) according to the present embodiment may be an access node included in a business office such as a headquarters, sales office, or branch office, and may be one of a plurality of PTN access nodes (110a, 110b,…, 110n). Here, n may be the maximum number of the plurality of PTN access nodes.

[0033] Below, each component included in the PTN access node (110) will be described.

[0034] The forwarding classification processing unit (401) receives a frame incoming from a local L2 / L3 switch and parses the frame header and service identifier (e.g., Ethernet Virtual Connection (EVC) / Virtual LAN (VLAN), Class of Service (CoS) / Differentiated Services Code Point (DSCP)).

[0035] The forwarding classification processing unit (401) classifies the traffic into multiple service classes, including control traffic and video traffic, based on the parsed results. Here, the classification results are mapped to class-specific queues, and service identification information is provided to the traffic-specific QoS scheduling processing unit (450) and the service-specific protection domain control unit (460). The service identifier may be defined to include the E-Line of the control service and the E-LAN ​​of the video service, and each service is mapped to a different EVC / VLAN.

[0036] The traffic event linkage unit (430) receives traffic event metadata from the control policy server (300). Specifically, the traffic metadata collection management unit (432) receives and stores metadata including signal cycles (Cycle / Offset / Split), conflicting traffic events, and priority signal events through a management path, and the policy parameter conversion unit (436) generates scheduling parameters based on the metadata. The scheduling parameters may include time slot allocation parameters for control traffic queues and weight adjustment parameters for video traffic queues.

[0037] The traffic event linkage unit (430) can be configured to calculate periodic time slots aligned to the signal cycle and conflicting traffic phase pattern, and to additionally calculate temporary priority slots according to the time of event occurrence.

[0038] Additionally, the traffic event linkage unit (430) can reserve a priority slot of the control queue during a predetermined time interval Δt based on the phase transition point, and control the schedule weight of the video queue to be temporarily attenuated during the interval Δt. When metadata reception is not possible, a robust mode is operated to automatically switch to a predefined basic schedule profile, and even in this case, the service-specific independent protection domain is maintained.

[0039] The traffic-specific QoS scheduling processing unit (450) determines the output order by performing queue management and scheduling control for each service class using the above scheduling parameters and microburst indicators calculated based on the inflow characteristics in the short-time observation window.

[0040] The traffic-specific QoS scheduling processing unit (450) includes a burst management shaping unit (452), a gating scheduling kernel unit (456), and a delay-based AQM processing unit (459).

[0041] The burst management shaping unit (452) calculates a microburst indicator using the increase in the amount of incoming bytes or packets in the observation window and the duration, and if the indicator exceeds a threshold, temporarily increases the minimum guarantee rate or priority slot width of the control queue. In addition, the burst management shaping unit (452) performs dual token bucket shaping by applying a first token bucket for average speed control and a second token bucket for ultra-short burst absorption in parallel to limit the delay and jitter of the control traffic.

[0042] The gating scheduling kernel unit (456) executes hybrid scheduling based on time slot information provided by the traffic event linkage unit (430), opening the control queue first during a predetermined interval of the signal phase transition time, and applying strict priority (PRIQ: Priority Queuing) to the control queue and weighted round robin (WRR: Weighted Round Robin) or deficit round robin (DRR: Deficit Round Robin) to other queues during scheduling.

[0043] The delay-based AQM processing unit (459) primarily applies delay-based active queue management (AQM) to video queues and suppresses frame backlogging by performing frame marking or discarding when the queue delay exceeds a threshold.

[0044] The time synchronization processing unit (470) receives the Precision Time Protocol (PTP: Precision Time Protocol, IEEE 1588v2) and / or Synchronous Ethernet (SyncE: Synchronous Ethernet) and provides time and frequency information to the traffic-specific QoS scheduling processing unit (450) and the transmission encapsulation processing unit (480). The time synchronization processing unit (470) may, if necessary, assign a priority slot or a minimum guaranteed bandwidth to the time synchronization packet so that synchronization precision is maintained even during scheduling.

[0045] The transmission encapsulation processing unit (480), depending on the service identification result of the forwarding classification processing unit (401) and the output of the traffic-specific QoS scheduling processing unit (450), encapsulates the frame in one or more ways such as the Label Switched Path (LSP) or Pseudowire (PW) of the Multiprotocol Label Switching Transport Profile (MPLS-TP), or QinQ (IEEE 802.1ad VLAN Stacking), which is a dual tagging method, and transmits it to the PTN uplink (circuits 12a, 12b).

[0046] In this case, each service is assigned a distinct identifier (EVC / VLAN, LSP label, Pseudowire identifier, etc.), enabling independent forwarding, OAM, and protection failover at the service level even when sharing the same path. Here, a service refers to an Ethernet Virtual Connection (EVC) or a corresponding logical transport instance configured according to the Metro Ethernet Forum's service models (E-Line, E-LAN, etc.), and this instance combines a unique identifier (VLAN / EVC, MPLS-TP LSP label, Pseudowire identifier, etc.) with service-specific QoS, OAM, and protection policies.

[0047] The service-specific protection domain control unit (460) includes a protection domain control management unit (462) and an OAM linkage processing unit (464).

[0048] The protection domain control management unit (462) manages the protection group identifier (PGID) per service, primary path and secondary path, and failover triggers (loss of local signal, link failure, exceeding OAM performance threshold, etc.) in a table format, and can perform priority arbitration to prioritize the recovery of the control E-Line service in the event of a simultaneous failure.

[0049] The OAM linkage processing unit (464) sets up and manages independent operation management sessions (OAM: Operations, Administration and Maintenance) for each service to perform connectivity checks (CC: Connectivity Check) and performance measurements (latency, jitter, frame loss, etc.), and if the performance indicator exceeds a threshold, it instructs protection switching only for the corresponding service. For example, it can be configured to independently apply linear protection (1+1 or 1:1) to control services and Ethernet ring protection (ERPS: Ethernet Ring Protection Switching) to video services.

[0050] The remote management agent unit (490) is responsible for receiving or updating settings and policies and reporting telemetry. The remote management agent unit (490) distributes parameters to the traffic event linkage unit (430), the traffic-specific QoS scheduling processing unit (450), the service-specific protection domain control unit (460), the time synchronization processing unit (470), and the transmission encapsulation processing unit (480), periodically collects and reports operational data such as queue occupancy, microburst metrics, and OAM results, and supports adaptive updating of thresholds or weights based on the reported results.

[0051] In terms of data path, the PTN access node (110) maps frames entering from the premises switch to service-specific queues in the forwarding classification processing unit (401), then determines the output order in the traffic-specific QoS scheduling processing unit (450), and then encapsulates them in the transmission encapsulation processing unit (480) and transmits them to the PTN uplinks (12a, 12b).

[0052] In terms of control and management paths, the PTN access node (110) receives metadata from the control policy server through the traffic event linkage unit (430) and provides scheduling parameters, the time synchronization processing unit (470) provides synchronization information to the internal module of the access node, and the service-specific protection domain control unit (460) directs protection switching at the service level according to OAM performance indicators. The configuration and operation of the PTN access node (110) are merely examples, and the length of the observation window, the threshold calculation method, the width of the time slot and the numerical value of the schedule weight, the transmission encapsulation method, and the protection method may be changed according to the network policy and implementation environment.

[0053] FIG. 3 is a flowchart illustrating the processing operation of an ITS transmission system according to an embodiment of the present invention.

[0054] The processing operations of the ITS transmission system can be performed repeatedly in a periodic manner based on signal cycles or in an event-based manner.

[0055] In step S310 (policy and event generation), the control policy server (300) generates traffic event metadata including signal cycles (Cycle, Offset, Split), priority signals, and conflicting traffic information, and service policies (e.g., service-specific weights, thresholds, connectivity check cycles).

[0056] In step S320 (policy and metadata distribution), the control policy server (300) distributes the generated metadata and service policies to the Packet Transport Network (PTN) (100) and each PTN access node (110) via a management policy path. The distribution items may include mapping of Ethernet Virtual Connections (EVC) and Virtual LANs (VLANs), service class definitions, initial values ​​for time slots and schedule weights, and Operations, Administration and Maintenance (OAM) cycle settings.

[0057] In step S330 (setting up OAM and management channels), the PTN management system (500) sets up OAM sessions for each service. The PTN management system (500) opens IEEE 802.1ag Connectivity Check (CC) and ITU-T Y.1731-based delay, jitter, and frame loss measurement sessions, and can set a shorter check cycle for the control service (E-Line) than for the video service (E-LAN).

[0058] In step S340 (field traffic collection), the premises L2 / L3 switch aggregates traffic generated from the signal controller (200), sensor (210), roadside unit (RSU) (220), and closed-circuit television (CCTV) (230) and transmits it to the PTN access node (110x).

[0059] In step S350 (service separation), the PTN access node (110x) parses the header of the received frame and service identifiers, such as EVC / VLAN, Class of Service (CoS), and Differential Services Code Point (DSCP), classifies it into a plurality of service classes including control services (E-Line, e.g., VLAN 600) and video services (E-LAN, e.g., VLAN 61X), and maps the classification results to class-specific queues.

[0060] In step S355 (transmission path setup and transmission), the PTN access node (110x) applies transport encapsulation to the frame according to the classification result and policy and transmits it to the uplink. Depending on the implementation, a Label Switched Path (LSP) of Multiprotocol Label Switching - Transport Profile (MPLS-TP), a Pseudowire (PW), or QinQ (IEEE 802.1ad VLAN Stacking) may be used, and the frame is transmitted to the circuit (12a, 12b) through the active path among the configured primary or secondary paths. To provide a precise time reference, Precision Time Protocol (PTP, IEEE 1588v2) and / or Synchronous Ethernet (SyncE) may be distributed to the internal modules of the PTN access node.

[0061] In step S360 (collection of OAM performance per service), the PTN access node (110x) or PTN management system (500) collects OAM performance indicators, such as delay, jitter, and frame loss, for each service being transmitted and provides them to protection control.

[0062] In step S370 (threshold determination and alarm), the PTN management system (500) or the PTN access node (110x) determines whether a performance indicator exceeds a service-specific threshold, and if a threshold exceedance is detected, records and notifies a relevant alarm. In this embodiment, the PTN access node (110x) calculates a microburst indicator using the inflow characteristics in a short-time observation window and can preemptively detect a surge in queue delay or jitter deterioration by considering the indicator together.

[0063] In step S380 (Protection Switching Instruction), the PTN management system (500) or the PTN access node (110x) instructs protection switching only for the relevant service when a switching trigger, such as threshold exceeding, link failure, or local signal loss, is satisfied. For example, the control service (E-Line) is switched to linear protection (1+1 or 1:1), the video service (E-LAN) is switched to Ethernet Ring Protection Switching (ERPS), and the two protection domains are operated independently of each other.

[0064] In step S390 (policy and schedule update), the PTN management system (500) or remote management agent updates schedule parameters such as policies, thresholds, time slots, and schedule weights based on OAM results and telemetry, such as queue occupancy and microburst indicators, and redistributes the updated information to each PTN access node.

[0065] Finally, in step S395 (repetition of the next cycle), the PTN access node (110x) repeats the above procedure at the time of the next signaling cycle or the next traffic event. If traffic event metadata cannot be received, the PTN access node (110x) operates in a robust mode that automatically switches to the default schedule profile, and even then, the service-specific independent protection domain is maintained. The order of the above steps is merely an example for convenience of explanation, and some steps may be performed in parallel, omitted, or added depending on the network policy and operating environment.

[0066] FIG. 4 is a flowchart illustrating a packet transmission control method at a PTN access node according to an embodiment of the present invention.

[0067] The packet transmission control method at the PTN access node (110) can be performed repeatedly in a periodic manner in signal cycle units or in an event-based manner.

[0068] In step S410, the PTN access node obtains time and frequency synchronization by the Precision Time Protocol (PTP, IEEE 1588v2) and / or Synchronous Ethernet (SyncE), and provides the obtained synchronization information to subsequent scheduling and transmission encapsulation processing.

[0069] In step S420, the PTN access node checks the management path status with the control policy server to determine whether traffic event metadata can be received. If reception is not possible, the PTN access node immediately switches to a predefined default schedule profile in step S425 and proceeds to step S440 while maintaining the service-specific independent protection domain. If reception is possible, the PTN access node receives metadata including signal cycles (Cycle / Offset / Split), conflicting traffic events, and priority signal events in step S430, and generates scheduling parameters including time slot allocation parameters for the control queue and weight adjustment parameters for the video queue based on the received metadata. The scheduling parameters may include cycle-aligned time slots aligned with the signal cycle and conflicting traffic phase patterns, and temporary priority slots corresponding to the time of event occurrence. In particular, they may be configured to reserve priority slots for the control queue during a predetermined Δt interval based on the phase transition time and to temporarily attenuate the weight of the video queue during that interval.

[0070] In step S440, the PTN access node collects frames incoming from the premises L2 / L3 switch. In step S450, the PTN access node parses the header and service identifier of the collected frames, such as Ethernet Virtual Connection (EVC) / Virtual LAN (VLAN) and Class of Service (CoS) / Differentiated Services Code Point (DSCP), classifies them into multiple service classes including control services (E-Line, e.g., VLAN 600) and video services (E-LAN, e.g., VLAN 61X), and maps the classification results to class-specific queues.

[0071] In step S455, the PTN access node maps frames to the corresponding protection domains based on the protection group identifier (PGID), primary path and secondary path, and failover triggers (loss of local signal, link failure, exceeding operational and management performance thresholds, etc.). The PTN access node may apply priority arbitration to prioritize the recovery of the control E-Line in the event of a concurrent failure.

[0072] In step S460, the PTN access node calculates a microburst metric using the increase in incoming bytes or packets and the duration in the short-time observation window. If the metric exceeds a threshold, the PTN access node adjusts scheduling parameters to temporarily increase the minimum guarantee rate or priority slot width of the control queue.

[0073] In step S470, the PTN access node performs traffic-specific Quality of Service (QoS) scheduling. The PTN access node performs dual token bucket shaping by applying a first token bucket for average speed control and a second token bucket for ultra-short burst absorption in parallel, applies gating to prioritize opening control queues during a specific interval at the signal phase transition point, and performs hybrid scheduling by applying Priority Queuing (PRIQ) to control queues and Weighted Round Robin (WRR) or Deficit Round Robin (DRR) to other queues. The PTN access node determines the output order by performing the above scheduling according to the scheduling parameters generated in step S430 and the microburst indicator of step S460. If necessary, the PTN access node controls congestion by applying delay-based Active Queue Management (AQM) to video queues and performing marking or discarding when queue delays exceed a threshold. The PTN access node maintains synchronization precision even during scheduling by assigning priority slots or minimum guaranteed bandwidth to time synchronization packets.

[0074] In step S480, the PTN access node transports the determined output frame according to the service identifier using at least one of the Multiprotocol Label Switching - Transport Profile (MPLS-TP), Label Switched Path (LSP), Pseudowire (PW), or IEEE 802.1ad VLAN Stacking (QinQ) methods. In step S485, the PTN access node transmits the frame along the established active path to the uplink line (12a / 12b).

[0075] In step S490, the PTN access node collects Connectivity Check (CC) and performance measurement (latency, jitter, frame loss) results through Operations, Administration and Maintenance (OAM) sessions. The PTN access node or the PTN management system may perform differential monitoring by setting a shorter CC interval for the Control E-Line than for the Video E-LAN. In step S495, the PTN access node or the PTN management system determines whether the collected performance indicators exceed service-specific thresholds, and if an exceedance is confirmed, performs protection switching for the relevant service in step S496. For example, linear protection (1+1 or 1:1) is applied to the Control E-Line, and Ethernet Ring Protection Switching (ERPS) is applied to the Video E-LAN. If the thresholds are not exceeded, the PTN access node maintains the current path and schedule in step S497.

[0076] Finally, in step S498, the remote management agent reports queue occupancy, microburst metrics, and OAM results via telemetry, and updates and deploys schedule and protection parameters, such as thresholds, weights, and time slots, based on the reported results. In step S499, the PTN access node repeats the above procedure until the next cycle or the next event.

[0077] The order of steps included in the packet transmission control method according to the present embodiment is merely an example to aid understanding, and some steps may be performed in parallel, omitted, or added depending on network policies and operating environments. Even when metadata reception is unavailable, the PTN access node automatically switches to the default schedule profile and maintains service-specific independent protection domains to continue the service.

[0078] Although FIGS. 3 and FIGS. 4 describe each step as being executed sequentially, they are not necessarily limited thereto. In other words, since it is possible to modify and execute the steps described in FIGS. 3 and FIGS. 4 respectively, or to execute one or more steps in parallel, FIGS. 3 and FIGS. 4 are not limited to a chronological order.

[0079] The packet transmission control method according to the present embodiment described in FIGS. 3 and 4 may be implemented as an application (or program) and recorded on a recording medium readable by a terminal device (or computer). The recording medium, on which the application (or program) for implementing the packet transmission control method according to the present embodiment is recorded and which is readable by a terminal device (or computer), includes all types of recording devices or media in which data that can be read by a computing system is stored.

[0080] The foregoing description is merely an illustrative explanation of the technical concept of the embodiments of the present invention, and those skilled in the art to which the embodiments of the present invention pertain will be able to make various modifications and variations within the scope that does not deviate from the essential characteristics of the embodiments of the present invention. Accordingly, the embodiments of the present invention are intended to explain, not limit, the technical concept of the embodiments of the present invention, and the scope of the technical concept of the embodiments of the present invention is not limited by these embodiments. The scope of protection of the embodiments of the present invention shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of the embodiments of the present invention.

Claims

Claim 1 A method for controlling packet transmission at a PTN access node for an ITS communication network, comprising: a step of classifying into a plurality of service classes including control traffic and video traffic based on the header and service identifier of a received frame; a step of receiving traffic event metadata including signal cycles, conflicting traffic events, and priority signal events from a control policy server; a step of generating scheduling parameters based on the metadata, including time slot allocation parameters for a control traffic queue and weight adjustment parameters for a video traffic queue; a step of calculating a microburst indicator based on frame inflow characteristics in a short-time observation window, and determining the output order by performing queue management and scheduling control for queues by service class according to the scheduling parameters and the microburst indicator; a step of transmitting by applying a predetermined transmission encapsulation according to a service identifier; and a step of maintaining independent protection domains for each service and performing linear or ring protection switching only for the corresponding service when a threshold is exceeded based on an OAM performance indicator for each service. Claim 2 A packet transmission control method according to claim 1, wherein the step of generating the scheduling parameters comprises calculating a periodically aligned time slot for a control queue to be aligned with the signal cycle and conflicting traffic phase pattern, and additionally calculating a temporary priority slot according to the time of event occurrence. Claim 3 A packet transmission control method according to paragraph 2, wherein the time slot is reserved for a predetermined Δt interval based on the transition point of the conflicting traffic phase, and is set to temporarily attenuate the schedule weight of the video queue during the Δt interval. Claim 4 A packet transmission control method according to claim 1, wherein the step of calculating the microburst indicator is performed by calculating the indicator using the increase in incoming bytes or packets and the duration in a short-term observation window, and temporarily increasing the minimum guarantee rate or priority slot width of the control queue when the indicator exceeds a threshold. Claim 5 A packet transmission control method according to claim 1, wherein the step of determining the output order is characterized by performing shaping to limit delay and jitter by applying a first token bucket for average speed control and a second token bucket for ultra-short burst absorption in parallel to the control traffic. Claim 6 A packet transmission control method according to claim 1, wherein the step of determining the output order is characterized by performing gating on the control queue in a predetermined interval of the signal phase transition time to perform queue management and scheduling control. Claim 7 A packet transmission control method according to claim 1, wherein the step of determining the output order is characterized by performing hybrid scheduling by applying strict priority (PRIQ) to the control queue and weighted round-robin (WRR or DRR) to other queues to perform queue management and scheduling control. Claim 8 A packet transmission control method according to claim 1, wherein the step of determining the output order by performing queue management and scheduling control is characterized by applying a delay-based active queue management (AQM) policy to a video traffic queue and controlling frame congestion by performing frame discarding or marking when the queue delay exceeds a threshold. Claim 9 A packet transmission control method according to claim 1, wherein the step of classifying into a plurality of service classes is performed such that the service identifier is defined to include an E-Line for control services and an E-LAN ​​for video services, and each service is mapped to a different EVC / VLAN. Claim 10 delete Claim 11 A packet transmission control method according to claim 9, wherein the step of performing the protection switching is characterized by setting the OAM as an independent session for each service and setting the connectivity check cycle (CC interval) of the control E-Line to be shorter than that of the video E-LAN ​​to perform differential monitoring. Claim 12 A packet transmission control method according to claim 9, wherein the step of performing the protection switching defines a protection group identifier (PGID), a primary path and a secondary path, and a switching trigger (including local signal loss, link failure, and exceeding an OAM performance threshold) for each service, and performs priority arbitration to prioritize the recovery of the control E-Line service in the event of a simultaneous failure. Claim 13 A packet transmission control method according to claim 12, wherein the step of performing the protection switching is characterized by performing linear protection (1+1 or 1:1) for the control E-Line and ring protection (ERPS) for the image E-LAN. Claim 14 A packet transmission control method according to claim 1, wherein the step of receiving traffic event metadata is characterized by operating in a robust mode that automatically switches to a basic schedule profile when receiving the metadata is not possible, while maintaining an independent protection domain for each service. Claim 15 A packet transmission control method according to claim 1, further comprising: receiving and updating the metadata and schedule or protection parameters through a remote management agent; periodically reporting telemetry including queue occupancy, microburst indicators and OAM results; and adaptively updating thresholds or weights based on the reported results. Claim 16 A PTN access node controlling packet transmission for an ITS communication network comprises: a forwarding classification processing unit configured to classify into multiple service classes, including control traffic and video traffic, based on the header and service identifier of a received frame and map to a class-specific queue; a traffic event interlocking unit configured to receive traffic event metadata, including signal cycles, conflicting traffic events, and priority signal events, from a control policy server, and to generate scheduling parameters, including time slot assignment parameters for a control traffic queue and weight adjustment parameters for a video traffic queue, based on said metadata; a traffic-specific QoS scheduling processing unit configured to calculate a microburst indicator based on frame inflow characteristics in a short-time observation window, and to determine the output order by performing queue management and scheduling control for service-class queues according to said scheduling parameters and said microburst indicator; and a transmission encapsulation processing unit configured to transmit a frame by applying a predetermined transmission encapsulation according to a service identifier. A PTN access node characterized by including a service-specific protection domain control unit configured to maintain independent protection domains for each service and configured to perform linear or ring protection failover only for the relevant service when a threshold is exceeded based on OAM performance indicators for each service. Claim 17 A PTN access node according to claim 16, further comprising: a time synchronization processor that receives and distributes PTP and / or SyncE and provides time information to the traffic-specific QoS scheduling processor and the transmission encapsulation processor; and a remote management agent that receives and updates schedule and protection parameters and performs telemetry reporting including queue occupancy, microburst indicators, and OAM results.

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