JP6867230B2 - Communication device - Google Patents

Description

The present invention relates to a communication device.

Generally, in an access network, a communication device that controls data transfer collects lines of various traffic to be transferred, multiplexes these traffic, and then transfers the data to the core network through an edge router. The core network is a large-capacity core communication network that connects telecommunications carriers. Each communication device identifies the priority by using a value such as COS (Class of Service) described in the layer 2 frame, and uses a user identifier such as VLAN ID (Virtual Local Area Network Identifier) to identify the source user. Identify.

On the other hand, in order to efficiently accommodate the ever-increasing number of mobile traffic in recent years, a large number of REs (Radio Equipment) are arranged at high density and connected to the centrally arranged RECs (Radio Equipment Control). C-RAN (Centralized Radio Access Network) configuration is being studied. The network connecting RE-REC is called a front hole, and since this is configured by a layer 2 switch at low cost, the standardization of IEEE 802.1CM is progressing. In this technology, the front hall traffic is transferred by connecting RE and REC to the network configured by the layer 2 switch.

Further, in the TDD (Time Division Duplex) system, which is expected to be used in the mobile network in the future, uplink and downlink traffic transmission between RE-REC is performed in time division. At this time, time synchronization is performed between each RE and REC, a time stamp is added, and data is transmitted. Further, at this time, in the layer 2 network to which RE and REC are connected, time synchronization is performed between the switches, and the front hall traffic is transferred with low delay.

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

Conventionally, as a technique for detecting an abnormality in time synchronization in a layer 2 network, for example, PTP listed in Non-Patent Document 1 and 802.1AS listed in Non-Patent Document 2 are generally used. This technology synchronizes the time by sending and receiving synchronization messages between switches. In addition, the time synchronization state is maintained by sending and receiving synchronization messages periodically. However, the frequency of the synchronized message is 128 per second at the maximum, that is, a cycle of about 8 ms, and the abnormality detection cannot be performed faster than this.

"IEEE-1588 Standard Version 2 -A Tutorial-", Agilent Technologies, 2006 IEEE P802.1AS / D7.6, "Timing and Synchronization for Time-Sensitive Applications in Bridged Local Area Networks", 2010

In view of the above circumstances, an object of the present invention is to provide a communication device that detects a time synchronization abnormality at a higher speed.

One aspect of the present invention is a communication unit that communicates with another device, a traffic monitor unit that acquires a time stamp from a frame received by the communication unit, and the time stamp and the current time acquired by the traffic monitor unit. The delay time is calculated from the difference, and the delay time calculated for the received frame is abnormal based on the history of the delay time calculated for each of the plurality of other frames received before the frame. It is a communication device including a time control unit that determines a time synchronization abnormality when it is detected.

One aspect of the present invention is the above-mentioned communication device, in which the time control unit creates a delay distribution, which is the distribution of the delay time for each flow, based on the history of the delay time, and calculates the received frame. Anomalies are detected based on the comparison between the delay time obtained and the delay distribution created for the same flow as the received frame.

According to the present invention, it is possible to detect a time synchronization abnormality at a higher speed.

It is a figure which shows the configuration example of the communication network by embodiment of this invention. It is a figure which shows the transfer route setting example in the configuration example of the communication network by the same embodiment. It is a block diagram which shows the configuration example of the node by the same embodiment. It is a figure for demonstrating the normal operation of a node by this embodiment. It is a figure for demonstrating the operation at the time of the failure occurrence of the node by this embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The communication device of the present embodiment is, for example, a layer 2 switch constituting a front hall network connecting RE (Radio Equipment: wireless device) and REC (Radio Equipment Control: wireless control device), and detects high-speed time synchronization abnormality. I do. Therefore, in the communication device of the present embodiment, the delay time in normal times is measured by using the time stamp given to the frame of the front hall traffic. When the communication device detects that the delay time of the received frame is an abnormal value based on the history of the delay time measured in the past, it determines that the time synchronization is abnormal. As a result, the time required for abnormality detection is shortened.

FIG. 1 is a diagram showing a configuration example of a communication network 100 according to the present embodiment. In the communication network 100 shown in the figure, n nodes (n is an integer of 2 or more) connected in a ring form form a front hall network. Node 1 is an example of a communication device. Node 1 operates as a layer 2 switch constituting the front hall network. In the front hall network, which is a layer 2 network to which the wireless device 2 (hereinafter, referred to as “RE2”) and the wireless control device 3 (hereinafter, referred to as “REC3”) are connected, the node 1 (layer 2 switch) is used. ) Are synchronized and the front hall traffic is transferred. Conventional technology can be used for time synchronization. Further, the topology of the front hall network can be arbitrary, and the transfer route is set by using a ring protocol or a routing protocol such as IS-IS (Intermediate System to Intermediate System). RE2 and REC3 are each connected to node 1. In the figure, n nodes 1 are described 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) is referred to as RE2-i. It is described as. REC3 is connected to node 1-n.

FIG. 2 shows an example of setting a flow transfer path between each RE2 and REC3 in the front hall network configuration of the communication network 100 shown in FIG. In the case of the example shown in FIG. 2, the flow from RE2-i (i is an integer of 1 or more (n-1) or less) to REC3 includes node 1-i, node 1- (i + 1), ..., Node 1-. A transfer path connected to REC3 via n is set. For example, in the flow from RE2-1 to REC3, a transfer route connected to REC3 via nodes 1-1, nodes 1-2, ..., Node 1-n is set. In the figure, for the sake of simplicity, only the transfer path of the flow from RE2 to REC3 is shown, but there is also a transfer path of the flow from REC3 to each RE2. When transmitting a frame in which transmission data is set, RE2 and REC3 add a time stamp which is data indicating the transmission time of the frame. A time stamp may be added to the node 1 that relays the frame. For the same flow, it is assumed that the nodes 1 to be time stamped on the transfer path of the flow are the same.

FIG. 3 is a block diagram showing a configuration example of the node 1. The node 1 includes a communication unit 11, a switching unit 12, a traffic monitor unit 13, and a time control unit 14.

The communication unit 11 communicates with other devices and transmits / receives frames. The node 1 shown in FIG. 2 includes communication units 11-1 to 11-3 as three communication units 11. The communication unit 11-1 communicates with RE2, and the communication units 11-2 and 11-3 each communicate with another node 1.

The switching unit 12 communicates a frame received from another device by the communication unit 11 with another device determined to be a transfer destination based on a transfer path set for the flow of the frame. Output. The transfer destination is another node 1, RE2 or REC3 one hop ahead in the communication path.

The traffic monitor unit 13 acquires the time stamp and the information for specifying the flow from the frame received by the communication unit 11, and outputs the time stamp to the time control unit 14. For example, as the information for specifying the flow, a VLAN ID set in the frame, a combination of a source MAC (Medium Access Control) address and a destination MAC (Medium Access Control) address, and the like can be used.

The time control unit 14 calculates the delay time of the received frame by calculating the difference between the current time and the time stamp. The time control unit 14 records the history of the calculated delay time. The time control unit 14 determines whether or not the delay time of the received frame is a normal value based on the history of the delay time calculated for each of the plurality of other frames received before the frame. .. When the time control unit 14 determines that the delay time calculated for the received frame is not a normal value but an abnormal value, it determines that the occurrence of a time synchronization abnormality has been detected.

Next, the operation of the node 1 will be described with reference to FIGS. 4 and 5.
FIG. 4 is a diagram for explaining the normal operation of the node 1. In the figure, nodes 1-1 to 1-9 constitute a front hall network. RE2-1 is connected to node 1-1 and REC3 is connected to node 1-9. In the flow from RE2-1 to REC3, a transfer route connected to REC3 via node 1-1, node 1-4, node 1-7, node 1-8, and node 1-9 is set. .. In the flow from REC3 to RE2-1, a transfer route opposite to the flow from RE2-1 to REC3 is set.

At node 1-8 on this transfer path, the communication unit 11 receives a frame addressed to REC3 from RE2-1 from node 1-7. The switching unit 12 transmits the frame received by the communication unit 11 to the node 1-9 via the communication unit 11 connected to the node 1-9 which is the next transfer destination (one hop destination on the transfer path). To do.

The traffic monitor unit 13 of the node 1-8 acquires the time stamp and the information for specifying the flow from the frame received from the frame received from the node 1-7 by the communication unit 11, and outputs the information to the time control unit 14. The time control unit 14 calculates the delay time from the difference between the current time and the time stamp acquired from the received frame. The time control unit 14 performs a determination process for determining whether or not the delay time of the received frame is a normal value based on the history of the delay time of the flow from RE2-1 to REC3, which is the same as the received frame. .. The method for determining that the time control unit 14 has an abnormal value in the determination process is not limited, but an example will be described below.

The time control unit 14 creates a delay distribution, which is a distribution of the delay time, based on the history of the delay time for each flow, and creates the delay time calculated for the received frame and the same flow as the received frame. Abnormality is detected based on comparison with the delayed distribution. Specifically, the time control unit 14 calculates the average value of the delay time and the standard deviation (σ) for each flow. The time control unit 14 compares the delay time calculated for the newly received frame with the average value and standard deviation (σ) of the past delay times calculated for the same flow as the frame. For example, if the delay time of the newly received frame deviates from the average value by nσ (n is a variable) or more, the time control unit 14 determines that it is an abnormal value, and if the deviation from the average value is less than nσ. Judge as normal. However, when the number of samples is small and it is determined that the delay distribution is incomplete, the time control unit 14 does not determine that it is an abnormal value. Further, the time control unit 14 uses a predetermined predetermined value instead of nσ, and determines that the value is abnormal when the deviation between the delay time of the newly received frame and the average value is equal to or greater than the predetermined value. May be good. When the time control unit 14 determines that the delay time is normal, the time control unit 14 updates and records the delay distribution of the flow from RE2-1 to REC3 based on the delay time calculated for the received frame.

FIG. 5 is a diagram for explaining the operation of the node 1 when a failure occurs. It is said that a failure has occurred in any node 1 on the transfer path (node 1-1, node 1-4, node 1-7, node 1-8) in which the frame transmitted by RE2-1 reaches node 1-8. To do. In this case, the time control unit 14 of the node 1-8 determines that the delay time of the newly received frame in the above determination process is an abnormal value, and detects the occurrence of a time synchronization abnormality. Alternatively, when the time control unit 14 continuously determines an abnormal value for the same flow or in a plurality of determination processes of a predetermined number of times or more regardless of the type of flow, a time synchronization abnormality has occurred. You may detect that. From this detection, the time control unit 14 of the node 1-8 knows that a time synchronization abnormality has occurred at the own node or another node 1 on the transfer path. Therefore, the time control unit 14 of the nodes 1-8 immediately starts the time correction including the own node by using the time synchronization protocol used with the other nodes 1 constituting the front hall network. To do. For example, when it is determined that different flows are abnormal a plurality of times, it can be seen that a time synchronization abnormality has occurred in the node 1 which gives a time stamp in common to those flows.

According to the above-described embodiment, it is possible to shorten the time required for detecting the time synchronization abnormality in the layer 2 switch constituting the front hall network. That is, the layer 2 switch reads the time stamp of the received frame and calculates the delay time from the difference between the current time and the time stamp. When the layer 2 switch detects that the delay time of the received frame is abnormal by a predetermined method based on the history of the delay time, it determines that the time synchronization is abnormal. This makes it possible to detect a time synchronization abnormality in a shorter time than a method using a conventional time synchronization protocol by using the traffic time stamp flowing into the layer 2 switch. Therefore, low-delay transfer in the layer 2 switch is possible, and a layer 2 communication device such as a base station in which low delay is important can be realized.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs and the like within a range that does not deviate from the gist of the present invention.

This is applicable when multiple communication devices perform time synchronization and transfer frames.

1, 1-1-1-9, 1- (n-1), 1-n-1 ... Node 2 ... Radio device (RE)
3 ... Wireless control device (REC)
11-1 to 11-3 ... Communication unit 12 ... Switching unit 13 ... Traffic monitor unit 14 ... Time control unit 100 ... Communication network

Claims (2)

With the communication unit that communicates with other devices,
A traffic monitor unit that acquires a time stamp from a frame received by the communication unit, and a traffic monitor unit.
The delay time is calculated from the difference between the time stamp acquired by the traffic monitor unit and the current time, and the delay time calculated for the received frame is for each of the plurality of other frames received before the frame. A time control unit that determines a time synchronization abnormality when an abnormality is detected based on the calculated history of the delay time.
Equipped with a,
For the same flow, among the plurality of devices on the transfer path of the flow, the device that adds the time stamp to the frame is the same.
When the time control unit determines that the time synchronization abnormality occurs a plurality of times for different flows, it determines that the time synchronization abnormality has occurred in the device that gives a time stamp in common to the different flows.
A communication device characterized by that. The time control unit creates a delay distribution, which is a distribution of the delay time for each flow, based on the history of the delay time, and creates the delay time calculated for the received frame and the same flow as the received frame. Abnormality is detected based on the comparison with the delay distribution.
The communication device according to claim 1.

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