JP6654592B2 - Communication device - Google Patents

Description

  The present invention relates to a technique for controlling communication traffic.

  In general, a communication device forming an access network often includes a plurality of communication interfaces for communicating with other communication devices. Such a communication device multiplexes traffic input via a plurality of communication interfaces, and transfers the multiplexed traffic to a core network via an edge router. For example, the core network is a large-capacity trunk communication network that connects communication carriers, and the edge router is a router that connects the network to which the communication device belongs and the core network. The communication device identifies the priority of the frame based on a value such as COS (Cost of Service) included in the communication frame, and identifies the user of the transmission source based on an identifier such as a VLAN ID.

  On the other hand, in recent years, a C-RAN (Centralized Radio Access Network) that aggregates a large number of REs (Radio Equipment) arranged at a high density into RECs (Radio Equipment Controls) in order to efficiently accommodate mobile terminals with a remarkable increase in traffic. ) Are being considered. Such a network connecting between the REs and the RECs is called a fronthaul, and the standardization of a technology for forming a lower-cost fronthaul by using a layer 2 switch is progressing (for example, IEEE 802.1CM).

  In the fronthaul, there are severe restrictions on the delay time (e2e delay) allowed for the transfer of traffic end-to-end (e2e: end-to-end) between RE and REC. For example, CPRI (Common Public Radio Interface) specifies a maximum allowable delay time of 100 μs. The main factors of the e2e delay include a processing delay required for transfer processing in a bridge, a propagation delay required for physical transmission between bridges, a competition delay between packets, and the like. A contention delay is a queuing delay that occurs between flows of the same priority. For example, when two packets having the same priority are input to the bridge at the same time and output from the same port, the transfer of one packet is made to wait for the transfer of the other packet to be completed.

  Further, in the TDD (Time Division Duplex) system which is being considered for application to a mobile network, uplink traffic and downlink traffic between RE and REC are transmitted in a time division manner. In this case, since the transmission timing of each RE is synchronized, there is a possibility that the fronthaul network becomes an environment in which competition between packets is likely to occur.

  Further, various methods are being studied for functional division between the RE and the REC. When these function dividing methods are adopted, it is conceivable that the communication band of the fronthaul becomes a variable band due to packetization of data. In this case, it is assumed that traffic is transferred at the fronthaul according to the traffic. In the conventional CPRI, since the transfer data amount 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, when the communication band becomes variable, there is a problem that competition between packets cannot be suppressed by a simple method such as the conventional CPRI.

  When a fronthaul network is configured using a layer 2 switch, in addition to a ring topology using a ring protocol, an IS-IS (Intermediate System to Intermediate) is used between nodes, such as shortest path bridging (SPB) and IEEE 802.1Qca. System) A method of determining a transfer route by exchanging route information based on a protocol is conceivable. In the fronthaul network configured as described above, since a transfer route is dynamically determined based on a connection state between RE and RCE, it is necessary to configure a flexible network that changes autonomously according to a network state. Can be. In particular, when IEEE 802.1Qca is used, not only the shortest path can be simply selected as the transfer path but also various selection criteria can be set depending on the routing algorithm used.

IEEE Standard 802.1ag, “Connectivity Fault Management”, 2007.

  2. Description of the Related Art Conventionally, in a layer 2 network, for example, a continuity check (hereinafter, referred to as “CC”) in IEEE802.1ag is generally used as a method of detecting a communication disconnection (hereinafter, referred to as “link disconnection”) due to a failure of a switch or a link between switches. Has been used. The detection of the link disconnection by the CC is to check the normality of the connection by periodically transmitting an OAM (Operations, Administration, Maintenance) frame on each link, and has high versatility. However, the transmission interval of the OAM frame is limited due to its high versatility, and the minimum value is specified at 3.3 ms. For this reason, there was a possibility that the link disconnection could not be quickly detected.

  In view of the above circumstances, an object of the present invention is to provide a technique capable of detecting a link disconnection in a layer 2 network more quickly.

  One aspect of the present invention is a traffic monitor that observes an input state of a flow in its own device, and an arrival timing estimating unit that estimates a timing at which a new flow arrives at its own device based on the input state. An abnormality detection unit that detects the occurrence of an abnormality on the transfer path of each flow based on the input state of the flow in the own device at the timing, and when an abnormality on a certain transfer path is detected, the abnormality is detected. An alternative path setting unit that determines another alternative path that replaces the transfer path.

  One aspect of the present invention is the communication device described above, wherein the arrival timing estimating unit estimates a pattern of a timing at which a new flow arrives at the own device based on an input state of the flow, and the estimated pattern Predicts the expected arrival time at which a new flow arrives at the own device based on the estimated arrival time, and the abnormality detection unit, when the predicted flow input is not observed at the expected arrival time, on the transfer path of the flow It is determined that an abnormality has occurred.

  One aspect of the present invention is the communication device described above, wherein the alternative route setting unit does not overlap with a transfer route of the flow in which the abnormality is detected, from a plurality of candidate routes predetermined as the alternative route candidates. A candidate route is selected as an alternative route for the transfer route.

  One embodiment of the present invention is the communication device described above, wherein the alternative route setting unit extracts a route common to the transfer routes of the plurality of flows in which the abnormality is detected, and is predetermined as the alternative route candidate. From among the plurality of candidate routes, a candidate route that does not include the common route is selected as an alternative route for the transfer routes of the plurality of flows.

  One aspect of the present invention is the communication device described above, further comprising a switching unit that outputs a received frame to an output port associated with a destination address, wherein the alternative route setting unit determines the alternative route to the determined alternative route. Switching is instructed to the switching unit.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to detect the traffic disconnection in a layer 2 network more quickly.

FIG. 2 is a diagram illustrating a configuration example of a fronthaul network 100 according to the first embodiment. FIG. 2 is a diagram illustrating a setting example of a transfer path between each RE2 and REC3 in the fronthaul network 100 according to the first embodiment. FIG. 3 is a block diagram illustrating a specific example of a functional configuration of a node 1 according to the first embodiment. FIG. 3 is a diagram illustrating an operation example of the fronthaul network 100 according to the first embodiment. FIG. 3 is a diagram illustrating an operation example of the fronthaul network 100 according to the first embodiment. FIG. 3 is a diagram illustrating an operation example of the fronthaul network 100 according to the first embodiment. FIG. 14 is a block diagram illustrating a specific example of a functional configuration of a node 1a according to the second embodiment.

<First embodiment>
FIG. 1 is a diagram illustrating a configuration example of a fronthaul network 100 according to the first embodiment. The fronthaul network 100 includes one or more nodes 1 (Node in the figure), and RE2 (Radio Equipment) and REC3 (Radio Equipment Controls) connected to any one of the nodes 1. FIG. 1 illustrates nodes 1-1 to 1-5 as examples of one or more nodes 1. Each node 1 functions as a layer 2 switch configuring the fronthaul network 100. The topology of the fronthaul network 100 is not limited to the ring type illustrated in FIG. 1, and may be any topology such as a bus type, a star type, and a mesh type. In the fronthaul network 100, a transfer route is determined by a routing protocol (for example, a ring protocol or IS-IS) according to the topology.

  FIG. 1 illustrates RE2-1 to 2-4 as examples of RE2 connected to the node 1. Specifically, RE2-1 is connected to node 1-1, RE2-2 is connected to node 1-2, RE2-3 is connected to node 1-3, and RE2-4 is connected to node 1-4. The REC 3 is connected to the nodes 1-5, and performs end-to-end communication with each RE2.

  FIG. 2 is a diagram illustrating an example of setting a transfer path between each RE 2 and REC 3 in the fronthaul network 100 according to the first embodiment. For example, the transfer route R1 is a transfer route starting from RE2-1 and reaching the REC3 in the order of the node 1-1, the node 1-2, the node 1-3, the node 1-4, and the node 1-5. Represents. The transfer route R2 represents a transfer route starting from RE2-2 and arriving at the REC3 in the order of the node 1-2, the node 1-3, the node 1-4, and the node 1-5. The transfer route R3 represents a transfer route that starts at RE2-3 and reaches REC3 via the nodes 1-3, 1-4, and 1-5 in this order.

  FIG. 3 is a block diagram illustrating a specific example of the functional configuration of the node 1 according to the first embodiment. The node 1 is an example of the communication device according to the present invention. The node 1 includes a CPU (Central Processing Unit), a memory, an auxiliary storage device, and the like connected by a bus, and executes a program. The node 1 executes the first communication unit 101, the second communication unit 102, the third communication unit 103, the switching unit 104, the traffic monitor 105, the arrival pattern estimation unit 106, the arrival time prediction unit 107, and the abnormality detection unit 108 by executing the program. And a device including the alternative route setting unit 109. All or a part of each function of the node 1 may be realized using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), and an FPGA (Field Programmable Gate Array). The program may be recorded on a computer-readable recording medium. The computer-readable recording medium is, for example, 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. The program may be transmitted via a telecommunication line.

  The first communication unit 101 and the second communication unit 102 are configured to include a communication interface for connecting the own device and another node 1. For example, the node 1-1 communicates with the node 1-5 via the first communication unit 101 and communicates with the node 1-2 via the second communication unit 102.

  The third communication unit 103 includes a communication interface for connecting the own device to RE2 or REC3. For example, the node 1-1 communicates with the RE 2-1 via the third communication unit 103, and the node 1-5 communicates with the REC 3 via the third communication unit 103.

  The switching unit 104 is a functional unit having a layer 2 switching function. The layer 2 switching function is a function of outputting a received frame to an output port associated with a destination MAC (Media Access Control) address. For example, the switching unit 104 of the node 1-1 acquires a frame transmitted from the RE 2-1 to the REC 3 from the third communication unit 103, and identifies that the destination of the acquired frame is the REC 3. The switching unit 104 outputs the acquired frame to the second communication unit 102 connected to the node 1-2 located next to the own device on the transfer path from the own device to REC3.

  The traffic monitor 105 observes a flow input to its own device. Here, the flow means individual end-to-end (e2e) traffic generated in the fronthaul network 100. The traffic monitor 105 outputs information (hereinafter, referred to as “time information”) indicating an input time (an example of an input state) of the observed flow to the arrival pattern estimation unit 106 and the abnormality detection unit 108.

  The arrival pattern estimating unit 106 and the arrival time estimating unit 107 are examples of the arrival timing estimating unit in the present invention. The arrival pattern estimating unit 106 estimates a pattern (hereinafter, referred to as an “arrival pattern”) of the timing at which each flow arrives at its own device based on the time information output from the traffic monitor 105. The arrival pattern estimation unit 106 outputs information indicating the estimated arrival pattern (hereinafter, “arrival pattern information”) to the arrival time prediction unit 107.

  The arrival time prediction unit 107 predicts the time at which a new flow arrives at its own device (hereinafter referred to as “arrival time”) based on the arrival pattern information output from the arrival pattern estimation unit 106. The arrival time prediction unit 107 outputs information (hereinafter, “arrival time information”) indicating the predicted arrival time (hereinafter, “arrival expected time”) to the abnormality detection unit 108.

  The abnormality detection unit 108 detects the occurrence of an abnormality on the transfer route of each flow based on the time information output from the traffic monitor 105 and the arrival time information output from the arrival time prediction unit 107. Specifically, the abnormality detection unit 108 compares the estimated arrival time of each flow predicted by the arrival time prediction unit 107 with the input time of each flow observed by the traffic monitor 105, and determines the difference between the two times. If it is equal to or greater than the predetermined threshold, it is determined that an abnormality has occurred on the transfer route of the flow. The abnormality detection unit 108 outputs information indicating the transfer route in which the abnormality has been detected (hereinafter, referred to as “abnormality detection information”) to the alternative route setting unit 109.

  The alternative route setting unit 109 determines another alternative route to replace the transfer route in which the abnormality is detected, based on the abnormality detection information output from the abnormality detection unit 108. The alternative route setting unit 109 outputs information indicating the determined alternative route (hereinafter, referred to as “alternative route information”) to the switching unit 104, and instructs the switching unit 104 to switch the transfer route to the alternative route. I do. The switching unit 104 switches the transfer route to the alternative route according to the route switching instruction from the alternative route setting unit 109.

  FIG. 4, FIG. 5, and FIG. 6 are diagrams illustrating an operation example of the fronthaul network 100 in the first embodiment. FIG. 4 shows an operation example at the time of normal operation, and FIGS. 5 and 6 show operation examples at the time of abnormality detection. First, FIG. 4 will be described.

As shown in FIG. 4, if it is a transfer path between RE2~REC3 during the normal, for example, _R US {1,2,3,4,5} and _R DS {5,4,3,2,1} Assume. Wherein _{R US} means transfer path (direction toward the REC3 from RE2) _{upstream, R DS} means the transfer path (direction from REC3 RE2) downstream. The numbers in the parentheses indicate the identifiers of the nodes 1 constituting the transfer path, and correspond to the numbers described in circles indicating the respective nodes 1 in the figure. The numbers in parentheses indicate the order of the nodes 1 from the start point to the end point of the transfer path, with the left end corresponding to the start point of the transfer path and the right end corresponding to the end point of the transfer path.

That is, R _US {1, 2, 3, 4, 5} has the node 1-1 as a start point and the node 1-5 as an end point. 4, and a transfer path through which frames are transferred in the order of the nodes 1-5. Similarly, R _DS {5, 4, 3, 2, 1} has node 1-5 as a start point and node 1-1 as an end point, and has nodes 1-5, 1-4, 1-3, and 1 -2, the transfer path in which the frame is transferred in the order of the node 1-1.

In normal time when the frame is in such a transfer path _{R US} and _{R DS} is transferred, the node 1-1 to 1-5 on the transfer path, the traffic monitor 105 observes the input flow, the arrival pattern estimating unit 106 However, based on the time at which the input of each flow was observed, the arrival pattern of the upstream flow (hereinafter, referred to as “upflow”) and the downstream flow (hereinafter, referred to as “downflow”) in the own device. Estimate the arrival pattern. For example, the arrival pattern estimating unit 106 estimates a period at which a flow is received for each of an uplink flow and a downlink flow (hereinafter, referred to as a “reception period”). Then, the arrival time prediction unit 107 predicts the arrival time (expected arrival time) of the flow arriving at its own device in the next reception cycle based on the estimated arrival pattern.

Next, FIG. 5 will be described. In the normal fronthaul network 100 described with reference to FIG. 4, it is assumed that a failure has occurred at the location (node 1-2) shown in FIG. In this case, uplink flow _{F US} transfer path _{R US} transmitted from RE2 is not transferred to the node 1-2 subsequent nodes. Therefore, the node 1-3 and 1-4 and 1-5 located at the subsequent node 1-2 on the transfer path, the upstream flow F ₁ is received even when the normal predicted times of arrival at the Absent. In this case, the abnormality detection unit 108, since the input flows are not observed in the vicinity of the expected arrival time, detects that the abnormality occurs on the transfer path R _US. Then, the abnormality detection unit 108, by outputting the abnormality detection information indicating a transfer path R _US the alternative route setting unit 109 notifies the alternative route setting unit 109 that the abnormality is detected in the transfer path R _US.

Next, FIG. 6 will be described. An abnormality on the assumption transfer path R _US is detected that in FIG. 5, an alternative route setting unit 109 determines the alternate route replaces the transfer path may be affected of the detected anomaly. FIG. 6 shows that the alternative route setting unit 109 of the node 1-5 changes the alternative route of the transfer route R _DS {5,4,3,2,1} where the abnormality is detected to the transfer route R _DS '$ 5,6. 7, 8, 1} shows an example determined.

  Here, the alternative route may be any transfer route that is at least different from the transfer route before the change. For example, the alternative route may be arbitrarily selected from transfer routes that are different from the transfer route before the change among the transfer routes that can be configured on connection, or a predetermined alternative route may be set in advance for the normal transfer route. It may be associated. However, in order to increase the recovery possibility of the communication, it is desirable that the alternative route is configured by a link that is different from the transfer route before the change as much as possible (does not overlap).

  In addition, when an abnormality is detected even after switching to a certain alternative route (hereinafter, referred to as a “first alternative route”), the alternative route setting unit 109 replaces the second alternative route with the first alternative route. May be determined, and the switching unit 104 may be instructed to further switch the first alternative route to the second alternative route. Further, in some cases, the failure site on the transfer route can be specified to some extent by the nodes 1 sharing the abnormality detection information. In such a case, the alternative route setting unit 109 narrows down or estimates the suspected part based on the abnormality detection information of the own device and the other node 1, and determines a transfer route that can be configured by the node 1 that is not included in the suspected part. An alternative route may be determined.

  The alternative route setting unit 109 instructs the switching unit 104 to switch the transfer route in which the abnormality has been detected to the alternative route determined as described above. The switching unit 104 switches the transfer route to the alternative route determined by the alternative route setting unit 109 according to the route switching instruction from the alternative route setting unit 109.

  For example, a network having a ring topology such as the fronthaul network 100 of the present embodiment is realized by a ring protocol. In this case, by changing a blocking port provided for each VLAN (Virtual Local Area Network), Switching to an alternative route can be performed quickly. On the other hand, if a routing protocol is used, the fronthaul network 100 can be configured with an arbitrary topology. However, if the transfer route is determined based on the link cost or the like, the transfer is performed in the upstream and downstream directions. It is desirable that the routes are set symmetrically on the same route. In this case, the alternative route may be registered in the routing table in advance.

  The node 1 according to the first embodiment configured as described above predicts the expected arrival time of the flow arriving at the own device based on the arrival pattern (for example, periodicity) of the flow arriving at the own device. By comparing with the actual traffic inflow situation, it is possible to more quickly detect a link break in the layer 2 network.

<Second embodiment>

  In the second embodiment, an example of a configuration that dynamically determines an alternative route instead of determining an alternative route for a preset transfer route will be described. FIG. 7 is a block diagram illustrating a specific example of the functional configuration of the node 1a according to the second embodiment. The node 1a according to the second embodiment differs from the node 1 according to the first embodiment in that the node 1a includes an alternative route setting unit 109a instead of the alternative route setting unit 109. The other functional units are the same as those of the node 1 in the first embodiment. Therefore, the same reference numerals as those in FIG.

  For example, when the fronthaul network 100 is configured in an arbitrary topology by a routing protocol, the alternative route setting unit 109a generates a plurality of transfer routes (hereinafter, referred to as “candidate routes”) that are candidates for the alternative route in advance. deep. The candidate route may be determined based on any path calculation algorithm. Also, the path calculation of the candidate route does not necessarily need to be executed by the node 1a. If there are controllers or the like that manage the routing in the fronthaul network 100, other devices such as these controllers may calculate the path. May be executed. In this case, the alternative route setting unit 109a may acquire information on the candidate route from these other devices.

  The alternative route setting unit 109a sets the cost value of the link in use among the links constituting the candidate route to be higher than the cost value of the unused link, so that the link is configured to be different from the current transfer route as much as possible. The alternative route is determined as follows. Hereinafter, a specific example of the method of determining an alternative route in the second embodiment will be described.

For example, the identifier of each flow is f, the set of computed candidate route for a flow f and P _f. First node 1 determines the one transfer path is from the set P _f candidate path, performing the transfer of frames during normal at the determined transfer path. Here, the determined transfer path _{R f} for a flow f, _R f as a set of links constituting a route and switch (node _{1a) O i {O 1,} O 2, O 3, ...} represents the. i is an identifier of a link or a switch, and is an integer of 1 or more.

The node 1a observes a flow input to its own device in the same manner as in the first embodiment, and generates a set N of unarrived flows that are scheduled to arrive. For example, the set N is generated by the abnormality detection unit 108. The alternative route setting unit 109a refers to the transfer route of each flow included in the set N, and extracts a link or a switch O _x (O _x in P _f , f∈N) common to each transfer route. The alternative route setting unit 109a, for each flow in the set N, selects a route that does not include the elements O _x of the transfer path contained in P _f as an alternate route.

  The node 1a of the second embodiment configured as described above can set a route that passes through a link or a switch different from the current transfer route as an alternative route. According to the node 1a of the second embodiment having such a configuration, it is possible to further increase the possibility of recovery from a link break due to switching to an alternative route.

<Modification>
The traffic monitor 105 does not necessarily need to estimate the switching timing for all the flows, but may sample some flows from a group of flows having the same transfer path and estimate the switching timing only for the sampled flows.

  The abnormality detection unit 108 may notify the detected abnormality to not only the alternative route setting unit 109 or 109a but also another switch (node 1 or 1a), a management device, or the like.

  The abnormality detection unit 108 may perform abnormality detection for each reception cycle based on the observation result of the input flow in each reception cycle, or may perform abnormality detection based on the observation results of the input flows in a plurality of reception cycles. You may.

  Even if an abnormality is detected for a certain flow, the abnormality detection unit 108 determines that the transfer route is normal if another flow having the same transfer route has arrived at the expected arrival time. May be.

  The node 1 or 1a 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. The program may be for realizing a part of the functions described above, or may be a program that can realize the functions described above in combination with a program already recorded in a computer system. It may be realized using a programmable logic device such as an FPGA (Field Programmable Gate Array).

  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 is applicable to a communication device that functions as a switch in a layer 2 network.

Reference Signs List 100: fronthaul network, 1, 1-1 to 1-5, 1a: node: 101: first communication unit, 102: second communication unit, 103: third communication unit, 104: switching unit, 105: traffic monitor , 106: arrival pattern estimation unit, 107: arrival time prediction unit, 108: abnormality detection unit, 109, 109a: alternative route setting unit, 2, 2-1 to 2-4: RE (Radio Equipment), 3: REC ( Radio Equipment Controls)

Claims (5)

A traffic monitor for observing the input status of the flow in the own device;
An arrival timing estimating unit that estimates a timing at which a new flow arrives at its own device based on the input situation;
An abnormality detection unit that detects occurrence of an abnormality on the transfer path of each flow based on the input state of the flow in the own device at the estimated timing,
When an abnormality on a certain transfer path is detected, an alternative path setting unit that determines another alternative path in place of the transfer path where the abnormality is detected,
A communication device comprising: The arrival timing estimating unit estimates a pattern of a timing at which a new flow arrives at the own device based on an input state of the flow, and estimates an arrival arrival of a new flow at the own device based on the estimated pattern. Predict the time,
The abnormality detection unit determines that an abnormality has occurred on the transfer route of the flow when the predicted flow input is not observed at the expected arrival time,
The communication device according to claim 1. The alternative path setting unit, from a plurality of candidate paths predetermined as the alternative path candidates, select a candidate path that does not overlap with the transfer path of the flow in which the abnormality is detected as an alternative path of the transfer path,
The communication device according to claim 1. The alternative route setting unit extracts a route common to the transfer routes of the plurality of flows in which the abnormality is detected, and selects a candidate that does not include the common route from a plurality of candidate routes predetermined as the alternative route candidates. Selecting a route as an alternative route for the transfer routes of the plurality of flows,
The communication device according to claim 1. A switching unit that outputs the received frame to an output port associated with the destination address,
The alternative path setting unit instructs the switching unit to switch to the determined alternative path,
The communication device according to claim 1.

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