JP6633499B2 - Communication device - Google Patents

Description

  The present invention relates to a communication device.

  In general, in an access network, a communication device that performs data transfer control collects various traffics to be transferred, multiplexes these traffics, and transfers the multiplexed traffic to a core network through an edge router. The core network is a large-capacity trunk communication network that connects communication carriers. Each communication device identifies a priority using a value such as a COS (Class of Service) described in a layer 2 frame, and identifies a transmission source user using a user identifier such as a VLAN ID (Virtual Local Area Network Identifier). Identify.

  On the other hand, in order to efficiently accommodate the increasing mobile traffic in recent years, a large number of REs (Radio Equipments: wireless devices) are arranged at a high density and connected to centralized RECs (Radio Equipment Controls: wireless control devices). A C-RAN (Centralized Radio Access Network) configuration is under study. A network connecting the RE and the REC is called a fronthaul, and the standardization of the IEEE 802.1CM is progressing in order to configure the fronthaul at a low cost by a layer 2 switch.

  For fronthaul traffic, the requirements for e2e (end-to-end) delay required for transmission between REs and RECs are strict. It is prescribed. The main elements of the e2e delay include a processing delay related to transfer processing in a bridge, a propagation delay required for physical transmission between bridges, and a competition delay between packets. The contention delay is, for example, when two packets with the same priority are input to the bridge at the same time and output from the same port, the time until the transfer of one packet is completed, and the other packet is the time until the start of transfer You need to wait, which refers to the delay that is occurring.

  In a TDD (Time Division Duplex) system that is expected to be used in a mobile network in the future, uplink and downlink traffic transmission between REs and RECs is performed by time division. At this time, by synchronizing the transmission timing of each RE, the fronthaul network is in an environment where competition between packets is likely to occur.

  Furthermore, various methods are being studied for functional division between the RE and the REC. When these functional division methods are adopted, it is conceivable that data is packetized and becomes a variable band, and fronthaul data transfer according to the amount of mobile data is performed. When CPRI is used, since the transfer data amount of the fronthaul is fixed, competition between packets can be avoided by a simple method such as shifting the transmission timing of each RE in advance. On the other hand, in the case of a variable band, there is a problem that such a simple method cannot be applied.

  Regarding the configuration of the fronthaul network using the layer 2 switch, in addition to a ring topology using a ring protocol, an inter-node (IS-IS) (Intermediate System to Intermediate System) such as SPB (Shortest Path Bridging) and IEEE 802.1Qca is used. It is conceivable to use a technique for realizing a flexible network configuration by exchanging route information and determining a transfer route. In particular, when IEEE 802.1Qca is used, it is possible to set and use a transfer route other than a simple shortest route according to a routing algorithm to be used.

  However, in some conventional routing algorithms, the e2e delay is suppressed in consideration of the processing delay and the propagation delay, but the transfer path cannot be set in consideration of the competition delay between packets. Also, there is no conventional queuing or scheduling algorithm that takes into account race delay.

  For example, when the technique of Non-Patent Document 1 is used, QoS (Quality of Service) routing for selecting a route for a flow requiring a bandwidth and delay guarantee is possible. There was a problem that it could not be considered.

  In addition, when the technique of Non-Patent Document 2 is used, it is possible to weight the packet transmission opportunity between flows, but it is not possible to execute scheduling for reducing e2e delay in consideration of contention delay. .

Qingming Ma and Peter Steenkiste, "Quality-of-Service Routing for Traffic with Performance guarantees", Building QoS into Distributed Systems, Springer, 1997, p. 115-126 Manolis Katevenis and Costas Courcoubetis, "Weighted Round-Robin Cell Multiplexing in a General-Purpose ATM Switch Chip", IEEE Journal on selected Areas in Communications, 1991, vol. 9, no. 8, p. 1265-1279

  In view of the above circumstances, an object of the present invention is to provide a communication device capable of reducing e2e delay in consideration of competition delay.

One aspect of the present invention is the communication device in a communication network having a plurality of communication devices and transferring a plurality of flows, wherein the communication device receives a flow transmitted from a transmission device, and receives a time from the received flow. A timestamp providing unit that provides a timestamp that is data indicating, the flow to which the timestamp is provided in the timestamp providing unit, and a transfer path that is forwarded from the other communication device immediately before, and Receiving a time-stamped flow from the other communication device on the transfer path, and determining a priority of the flow based on the received time-stamp given to the flow Unit and the other communication device one point ahead in the transfer path in an order according to the priority determined by the time determination unit. Ri and a transmission section for outputting the flow, the time determination unit, the time stamp and high when the front hole delays calculated by the difference between the current time exceeds a preset threshold priority It is determined to be a degree .
One embodiment of the present invention is a communication device in a communication network having a plurality of communication devices and transferring a plurality of flows, wherein the communication device receives a flow transmitted from a transmission device, and receives the received flow. A time stamp providing unit for providing a time stamp which is data indicating a time, the flow to which the time stamp is provided in the time stamp providing unit, and a flow transferred from another immediately preceding communication device on a transfer path. And receiving a time-stamped flow from the other communication device on the transfer path, and determining the priority of the flow based on the received time-stamp attached to the flow A time determination unit, and the other communication device one point ahead in the transfer path, according to the priority determined by the time determination unit. A transmission unit that outputs the flow according to the introduction, wherein the time determination unit determines that the delay in the front hall calculated by the difference between the time stamp and the current time is dynamically determined from the history of the past front hall delay. Is determined to have a higher priority if the threshold value is exceeded.
One embodiment of the present invention is a communication device in a communication network having a plurality of communication devices and transferring a plurality of flows, wherein the communication device receives a flow transmitted from a transmission device, and receives the received flow. A time stamp providing unit for providing a time stamp which is data indicating a time, the flow to which the time stamp is provided in the time stamp providing unit, and a flow transferred from another immediately preceding communication device on a transfer path. And receiving a time-stamped flow from the other communication device on the transfer path, and determining the priority of the flow based on the received time-stamp attached to the flow A time determination unit, and the other communication device one point ahead in the transfer path, according to the priority determined by the time determination unit. A transmitting unit that outputs the flow according to an introduction, wherein the time determination unit removes the time stamp from the received flow, and a difference between the removed time stamp and the current time is a delay in a front hall and a threshold. A process of notifying the priority of the flow determined based on the comparison with the other communication device, and a process of determining the priority of the received flow as the priority of the flow notified from the other communication device And at least one of

  One embodiment of the present invention is the above-described notification device, wherein the time determination unit adds information indicating the priority determined for the flow to the flow.

  One aspect of the present invention is the above-described notification device, wherein the queue for each priority for temporarily storing the flow, and the flow according to the priority determined by the time determination unit for the flow by the time determination unit. It further includes a switching unit for inputting to the queue, and a control unit for controlling the flow to be read from the queue for each priority by the strict priority queuing method and output from the transmitting unit.

  According to the present invention, it is possible to provide a communication device capable of reducing an e2e delay in consideration of a competition delay.

FIG. 1 is a diagram illustrating a configuration example of a communication network according to a first embodiment of the present invention. FIG. 3 is a diagram illustrating an example of setting a transfer path in a communication network configuration example according to the embodiment. FIG. 3 is a block diagram illustrating a configuration example of a communication device according to the embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The embodiment of the present invention relates to a traffic control technique in a communication device, and in particular, measures a transfer delay of a communication flow (signal) using a time stamp given at an edge, and preferentially transfers a flow with a large delay. In this regard, the present invention relates to a technology for reducing e2e (end-to-end) delay. Note that e2e means the entire route connecting the two devices at both ends for communication, or the two devices at both ends for communication.

The communication device according to the embodiment measures the delay of each flow of fronthaul traffic flowing into the fronthaul network using a time stamp given to the flow at an edge. As a result, each communication device operating as a bridge identifies a flow with a large delay and transfers the identified flow preferentially. As described above, the communication device according to the embodiment reduces the e2e delay by considering the competition delay for the fronthaul traffic flowing into the fronthaul network. The fronthaul network is a network that connects a radio device (RE: Radio Equipment Control) and a radio control device (REC: Radio Equipment Control), and the fronthaul traffic is communication between the RE and the REC. Traffic.
First, a first embodiment of the present invention will be described with reference to FIGS.

<First embodiment>
FIG. 1 is a diagram illustrating a configuration example of a communication network 100 according to the first embodiment. In the communication network 100 shown in FIG. 1, n (n is an integer of 2 or more) nodes 1 connected in a ring form a fronthaul network. The node 1 is an example of a communication device. Node 1 operates as a fronthaul bridge in the fronthaul network. The topology of the fronthaul network can be arbitrarily set, and a transfer path is set using a ring protocol or a routing protocol such as IS-IS (Intermediate System to Intermediate System). A wireless device 2 (hereinafter, referred to as “RE2”) or a wireless control device 3 (hereinafter, referred to as “REC3”) is connected to each node 1. Hereinafter, n nodes 1 will be referred to as nodes 1-1 to 1-n, respectively, and RE2 connected to node 1-i (i is an integer of 1 or more and n-1 or less) will be referred to as RE2-i. Describe. REC3 is connected to the node 1-n.

  FIG. 2 illustrates an example of setting a transfer path of a flow between each RE 2 and REC 3 in the fronthaul network configuration of the communication network 100 illustrated in FIG. In the case of the example shown in FIG. 2, the flows transmitted from RE2-i (i is an integer of 1 or more and (n-1) or less) to REC3 include nodes 1-i, 1- (i + 1),. A path connected to REC3 via 1-n is set. For example, in the flow from RE2-1 to REC3, a path connected to REC3 via nodes 1-1, 1-2,..., Node 1-n is set.

  In the figure, for simplicity, only the route from RE2 to REC3 is shown, but the reverse route from REC3 to each RE2 is taken. In the following, fronthaul traffic passing from RE2-i (i is an integer of 1 or more and (n-1) or less) to REC3 is referred to as a flow Fi. It is conceivable that the flow is identified using a VLAN-ID or the like set in the transmission data.

  FIG. 3 shows the configuration and flow processing of the node 1 in the above-described transfer path setting example. The node 1, which is a fronthaul bridge, includes a control unit 10, a time stamp adding unit (Timestamper) 11, a time determining unit (Timekeeper) 12, a switching unit 13, a highest priority queue (Super express queue) 14, a priority It has a queue (Express queue) 15 and a transmission unit 16.

  The control unit 10 controls each unit. The time stamp giving unit 11 receives the flow transmitted by the RE 2 (hereinafter, referred to as “Station flow”). The time stamp adding unit 11 adds a time stamp, which is data indicating the current time, to the Station flow, and outputs it to the time determining unit 12.

  The time determination unit 12 receives a flow (hereinafter, referred to as “Transit flow”) transmitted by the immediately preceding node 1 on the transfer path. Further, the time determination unit 12 receives the Station flow output by the time stamp providing unit 11. The time determination unit 12 determines, based on the received time stamps of these flows, whether the flow is the highest priority flow to be transferred with priority over other flows. The time determination unit 12 inputs the flow determined as the highest priority flow to the highest priority queue 14 and inputs the flow determined not to be the highest priority flow, that is, the normal fronthaul flow to the priority queue 15. The flow input to the highest priority queue 14 and the flow input to the priority queue 15 are read out by strict priority queuing (SPQ) under the control of the control unit 10 operating as a scheduler, and input to the transmission unit 16. Is done. The transmission unit 16 is an output port. The transmission unit 16 transfers the flow input from the highest priority queue 14 or the priority queue 15 to the next node 1 on the transfer path.

  In the above description, the node 1 has the output queues according to the priority of the highest priority queue 14 and the priority queue 15, but may have the output queues according to the priority for each flow.

The operation will be described using the node 1-i as an example.
The time stamp giving unit 11 of the node 1-i gives a time stamp to the frame of the Station flow input from the RE 2-i. The time stamp giving unit 11 may give a time stamp to all arriving frames, or may selectively give a time stamp to only a specific frame. The frame to which the time stamp has been added by the time stamp adding unit 11 is transferred to the time determining unit 12. The frame of the transit flow arriving from the node 1- (i-1) is directly transferred to the time determination unit 12 without passing through the time stamp adding unit 11. A time stamp is assigned to the frame of the transit flow by the time stamp assigning unit 11 of any of the nodes 1-1 to 1- (i-1).

  The time determination unit 12 performs the following time determination processing on the frames of both the transit flow and the station flow. First, the time determination unit 12 calculates a front-hall delay d that is a difference between the time stamp given to the frame and the current time. The time determination unit 12 compares the value of the delay d in the front hall with a preset threshold T. When determining that d> T, the time determination unit 12 determines that the flow of the frame is the highest priority flow to be transferred with priority. Which flow the frame is in is identified by, for example, the VLAN-ID set in the frame. Thereafter, the time determination unit 12 rewrites the priority information set in the frame of the flow determined as the highest priority flow to information indicating the highest priority (higher priority than the fronthaul flow). The time determination unit 12 performs this rewriting process regardless of the presence or absence of the time stamp.

  The method of setting the threshold T can be arbitrary, but an example will be given here. First, there is a method of using a value obtained by multiplying the e2e delay D of the front hall defined for the flow to be subjected to the time determination process by a constant coefficient as the threshold T. In addition, there is a method of using a value obtained by multiplying the e2e delay D by a coefficient corresponding to the number of remaining nodes (the number of hops) up to REC3 using the route setting information indicating the transfer route of each flow as the threshold T. Similarly, there is a method in which a value obtained by multiplying the e2e delay D by a coefficient according to the number of remaining nodes and the path length up to REC3 is used as the threshold T.

  The time determination unit 12 transfers the flow subjected to the time determination process to the switching unit 13. The switching unit 13 selects an output queue based on the priority information set for the frame, and inputs the frame to the selected queue. As a result, the switching unit 13 inputs the frame of the normal fronthaul flow to the priority queue 15 and inputs the frame of the highest priority flow to the highest priority queue 14. The frame of the flow input to the highest priority queue 14 and the frame of the flow input to the priority queue 15 are read out by the SPQ by the scheduler, and transferred from the transmission unit 16 which is the output port to the node 1- (i + 1). . That is, the frame in the highest priority queue 14 is always read out prior to the frame in the priority queue 15. Although not shown here, the frames in the priority queue 15 are always read out prior to other low-priority frames. The time stamp is removed when the node 1-n outputs a frame to the link connected to REC3.

  According to this method, a flow in which the e2e delay is likely to be large can be identified in advance, and the priority can be selectively increased and transferred. As a result, the number of flows that can be transferred within the range of the e2e delay specified in the fronthaul can be increased.

<Second embodiment>
A second embodiment of the present invention will be described. The second embodiment is almost the same as the first embodiment, except for the following points. That is, in the time determination process in the time determination unit 12, instead of comparing the value of the delay d in the front hall with the threshold T set in advance, a threshold dynamically determined from the history of the delay d in the front hall up to that time. Compared to T ', the difference is that when d>T', the flow is determined to be the highest priority flow to be transferred with priority. With this method, it is possible to adaptively determine the delay amount according to the situation in the network.

  The method of setting the threshold value T 'can be arbitrary, but an example will be given. The time determination unit 12 records the history of the value of the delay d in the front hall during a specific period, calculates the average value thereof, and gives the highest priority when the delay d in the front hall is larger than the calculated average value by a certain amount or more. There is a method of determining a flow. Alternatively, the time determination unit 12 calculates an average value and a standard deviation of the delay d in the front hall during a specific period, and calculates a front-end value based on the calculated average value and the standard deviation (for example, a total value). There is a method of determining the highest priority flow when the in-hole delay d is large.

<Third embodiment>
A third embodiment of the present invention will be described. The third embodiment is almost the same as the first embodiment, except for the following points. That is, in the time determination process in the time determination unit 12, instead of calculating the value of the delay d in the fronthaul in each node 1, the time determination unit 12 in the node 1-n connected to the REC 3 removes the time stamp from the frame. Only when this is done, the priority of the flow is determined based on a comparison between the delay d in the fronthaul and the threshold.

  Specifically, the time determination unit 12 of the node 1-n calculates a value obtained by subtracting the delay d in the front hall from the prescribed e2e delay D of the front hall, and when the calculated D−d is equal to or less than a certain value. Performs feedback to notify the other nodes 1-1 to 1- (n-1) that the flow of the frame has the highest priority. Although the feedback method is not particularly limited, a dedicated protocol may be used or some data frame may be used. The nodes 1-1 to 1- (n-1) that have been notified of the flow to be given the highest priority by the feedback determine the notified flow as the highest priority flow.

  Similarly, when the time determination unit 12 of the node 1-n determines that Dd calculated for the flow that is currently the highest priority flow exceeds a certain value, the highest priority release for that flow is canceled. For the other nodes 1-1 to 1- (n-1). The nodes 1-1 to 1- (n-1) which have been notified of the flow whose highest priority is canceled by the feedback stop judging the notified flow as the highest priority flow, and are the same as the normal fronthaul flow. This is a priority flow.

  In this way, e2e delays can be measured directly and flows that need to be prioritized can be accurately top priority.

  According to the embodiment described above, the communication network has a plurality of communication devices and transfers a plurality of flows. The communication device is, for example, the node 1. The communication device includes a time stamp adding unit, a time determining unit, and a transmitting unit. The time stamp assigning unit receives the flow transmitted from the transmitting device, and assigns a time stamp to the received flow. The transmitting device is, for example, RE2. The time determination unit receives the flow to which the time stamp is added by the time stamp adding unit and the flow transferred from another communication device immediately before and to which the time stamp is added on the transfer path. The time determination unit determines the priority of the received flow based on the time stamp given to the flow. The time determination unit may overwrite information indicating the priority determined for the received flow to the flow. The transmitting unit outputs the flow to another communication device one point ahead in the transfer path in an order according to the priority determined by the time determining unit.

  Note that the communication device may further include a queue for each priority for temporarily accumulating the flow, a switching unit, and a control unit. The switching unit inputs the flow received by the time determination unit to a queue corresponding to the priority determined for the flow. The control unit controls to read the flow from the queue for each priority by the strict priority queuing method and output the flow from the transmission unit.

  The time determination unit may determine that the priority is high when the delay in the front hall calculated from the difference between the time stamp and the current time exceeds a threshold. This threshold value may be a preset value or a value dynamically determined from a past history of delay in the fronthaul.

  In addition, the time determination unit of the communication device connected to the receiving device that is the destination of the flow removes the time stamp from the received flow, and determines the difference between the removed time stamp and the current time and the delay in the fronthaul and the threshold. The priority of the flow determined based on the comparison may be notified to another communication device. For example, if the transmitting device is REC2, the receiving device is RE3. The time determination unit of the communication device that has received the notification determines the priority of the received flow as the notified priority of the flow.

  According to the above-described embodiment, it is possible to construct a network that is highly resistant to delay reduction by considering the competition delay of the fronthaul traffic flowing into the fronthaul network.

  Some functions of the node 1 in the above-described embodiment may be realized by a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read and executed by a computer system. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, and a CD-ROM, and a storage device such as a hard disk built in a computer system. Further, a "computer-readable recording medium" refers to a communication line for transmitting a program via a network such as the Internet or a communication line such as a telephone line, and dynamically holds the program for a short time. Such a program may include a program that holds a program for a certain period of time, such as a volatile memory in a computer system serving as a server or a client in that case. Further, the above-mentioned program may be for realizing a part of the above-mentioned functions, and may be for realizing the above-mentioned functions in combination with a program already recorded in the computer system.

  As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiments and includes a design and the like within a range not departing from the gist of the present invention.

  The present invention can be used for a communication network that transmits a communication flow by a plurality of communication devices.

1-1 to 1-n Nodes 2-1 to 2- (n-1) Radio equipment (RE)
3. Radio control device (REC)
DESCRIPTION OF SYMBOLS 10 ... Control part 11 ... Time stamp addition part 12 ... Time determination part 13 ... Switching part 14 ... Highest priority queue 15 ... Priority queue 16 ... Transmission part 100 ... Communication network

Claims (5)

The communication device in a communication network having a plurality of communication devices and transferring a plurality of flows,
A time stamp providing unit that receives the flow transmitted from the transmitting device, and adds a time stamp that is data indicating time to the received flow,
The flow to which the time stamp is added by the time stamp adding unit, and the transfer from the other communication device immediately before on the transfer path , and the time stamp by the other communication device on the transfer path. A time determination unit that receives a flow to which the flow is attached, and determines a priority of the flow based on the time stamp attached to the received flow,
A transmission unit that outputs the flow in the order according to the priority determined by the time determination unit to the other communication device one point ahead in the transfer path,
Equipped with a,
The time determination unit determines that the priority is high when the delay in the front hall calculated by the difference between the time stamp and the current time exceeds a preset threshold.
A communication device characterized by the above-mentioned. The communication device in a communication network having a plurality of communication devices and transferring a plurality of flows,
A time stamp providing unit that receives the flow transmitted from the transmitting device, and adds a time stamp that is data indicating time to the received flow,
The flow to which the time stamp is added by the time stamp adding unit, and the transfer from the other communication device immediately before on the transfer path , and the time stamp by the other communication device on the transfer path. A time determination unit that receives a flow to which the flow is attached, and determines a priority of the flow based on the time stamp attached to the received flow,
A transmission unit that outputs the flow in the order according to the priority determined by the time determination unit to the other communication device one point ahead in the transfer path,
Equipped with a,
The time determination unit has a high priority when the delay in the front hall calculated by the difference between the time stamp and the current time exceeds a threshold dynamically determined from the history of the delay in the past front hall. Judge that there is
A communication device characterized by the above-mentioned. The communication device in a communication network having a plurality of communication devices and transferring a plurality of flows,
A time stamp providing unit that receives the flow transmitted from the transmitting device, and adds a time stamp that is data indicating time to the received flow,
The flow to which the time stamp is added by the time stamp adding unit, and the transfer from the other communication device immediately before on the transfer path , and the time stamp by the other communication device on the transfer path. A time determination unit that receives a flow to which the flow is attached, and determines a priority of the flow based on the time stamp attached to the received flow,
A transmission unit that outputs the flow in the order according to the priority determined by the time determination unit to the other communication device one point ahead in the transfer path,
Equipped with a,
The time determination unit removes the time stamp from the received flow, and determines the priority of the flow determined based on a comparison between the removed time stamp and a delay in the fronthaul, which is a difference between the current time, and a threshold, and the like. Performing at least one of the process of notifying the communication device and the process of determining the priority of the received flow as the priority of the flow notified from another communication device,
A communication device characterized by the above-mentioned. The time determination unit is configured to add information indicating the priority determined for the flow to the flow,
The communication device according to any one of claims 1 to 3, wherein: A queue for each priority for temporarily storing the flow,
A switching unit that inputs the flow to the queue according to the priority determined by the time determination unit for the flow,
A control unit that reads the flow from the queue for each priority by the strict priority queuing method and controls the flow to be output from the transmission unit.
The communication device according to any one of claims 1 to 4, wherein:

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