JP6588416B2 - Communication device - Google Patents

Description

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

  In general, a communication device constituting an access network is often provided with a plurality of communication interfaces for communicating with other communication devices. Such a communication apparatus 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 backbone communication network that connects communication carriers, and the edge router is a router that connects a network to which a communication device belongs and a core network. The communication apparatus identifies the priority of the frame based on a value such as COS (Cost of Service) included in the communication frame, and identifies a transmission source user based on an identifier such as a VLAN ID.

  On the other hand, in recent years, a C-RAN (Centralized Radio Access Network) that consolidates a large number of REs (Radio Equipment) arranged at high density into REC (Radio Equipment Controls) in order to efficiently accommodate mobile terminals whose traffic has increased significantly. ) Is being considered. Such a network connecting RE-REC is called a fronthaul, and the standardization of a technology for constructing a lower-cost fronthaul by using a layer 2 switch is progressing (for example, IEEE 802.1CM).

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

  Further, in the TDD (Time Division Duplex) system, which is considered to be applied to a mobile network in the future, 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, the fronthaul network may become an environment in which competition between packets is likely to occur.

  Further, various methods are being studied for functional division between RE and REC. When these function division methods are adopted, it is conceivable that the communication bandwidth of the fronthaul becomes variable due to data packetization. In this case, it is assumed that traffic is transferred according to the amount of communication in the front hall. Since the transfer data amount is fixed in the conventional CPRI, 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 conventional CPRI.

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

Quality-of-service routing for traffic with performance guarantees, in Building QoS into Distributed Systems.Springer, 1997, pp. 115-126.

  However, as described above, in the conventional routing algorithm, the e2e delay can be suppressed in consideration of the processing delay and the propagation delay. On the other hand, it is not possible to set the transfer route in consideration of the competition delay between packets. could not. For example, when the technology of Non-Patent Document 1 is used, it is described regarding QoS (Quality of Service) routing for selecting a transfer path for a flow that needs to guarantee a bandwidth and a delay time. The delay guarantee was not realized. This is because it is not easy to calculate the traffic competition delay in the multiplexing method in the conventional fronthaul network.

  In view of the above circumstances, an object of the present invention is to provide a technique that can more easily calculate the competitive delay of the traffic that propagates in a network in which a competitive delay may occur.

  One aspect of the present invention is a communication apparatus that includes a plurality of communication links and performs a transfer process of transferring an input flow input from a part of the plurality of communication links to a communication link according to a destination of the input flow The input flow that is input at the same timing and transferred to the same communication link is a competitive flow, and the communication link that inputs the competitive flow is a competitive link. The maximum delay time due to the transfer process of the competitive flow is calculated based on the number of inputs of 1 and the second input number that is the input number of the competitive flow in the communication link that inputs the most competitive flows among the competitive links. An estimation unit for estimation is provided.

  One aspect of the present invention is the communication apparatus described above, further including a transfer path control unit that sets a transfer path of the input flow based on the maximum delay time estimated by the estimation unit.

  One aspect of the present invention is the communication apparatus, wherein the estimation unit sets the first input number to N, the second input number to n, the maximum burst length of the competitive flow to m, and a transfer destination When the link speed of the communication link is e, the maximum delay time d is calculated by the following equations (1) and (2).

  One aspect of the present invention is the communication apparatus described above, wherein the estimation unit includes the first input number N, the second input number n, the maximum burst length of the competitive flow, and the competitive link. The maximum delay time d is calculated by the following formulas (3) and (4), where c is the link speed and e is the link speed of the transfer destination communication link.

  According to the present invention, it is possible to guarantee a delay time of a propagating traffic in a network in which a competitive delay may occur.

It is a figure which shows the structural example of the fronthaul network 100 in 1st Embodiment. 3 is a diagram illustrating a first setting example of a transfer path between RE2 and REC3 in the fronthaul network 100. FIG. It is a block diagram which shows the specific example of a function structure of the node 1 in 1st Embodiment. It is a figure which shows the operation example of the node 1 in a 1st setting example. It is a figure which shows the 2nd example of a setting of the transfer path | route between RE2 and REC3 in the fronthaul network 100. FIG. It is a figure which shows the operation example of the node 1 in a 2nd setting example.

<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, and RE2 and REC3 connected to the node 1. FIG. 1 shows nodes 1-1 to 1-8 as examples of one or more nodes 1. Nodes 1-1 to 1-4 constitute a first network 101, and nodes 1-4 to 1-8 constitute a second network 102. The node 1-4 is connected to both the first network 101 and the second network 102 by the first to fourth links. Here, the first link connects the node 1-1 and the node 1-4, and the second link connects the node 1-3 and the node 1-4. The third link connects the node 1-4 and the node 1-5, and the fourth link connects the node 1-4 and the node 1-8. The node 1-4 functions as a bridge that connects both the first network 101 and the second network 102. In the fronthaul network 100, a transfer path is set based on a routing protocol such as IS-IS.

  FIG. 1 shows RE2-1 to 2-6 as examples of RE2 connected to the node 1. Specifically, RE2-1 is the node 1-1, RE2-2 is the node 1-2, RE2-3 is the node 1-3, RE2-4 is the node 1-5, and RE2-5 is the node. 1-6 and RE2-6 are connected to nodes 1-7, respectively. REC3 is connected to node 1-8 and performs end-to-end communication with each RE2. In the fronthaul network 100, these end-to-end communications are multiplexed by the TDD scheme.

  FIG. 1 shows an example of the fronthaul network, but this does not limit the applicable topology of the present invention, and the fronthaul network may be configured in any topology.

  FIG. 2 is a diagram illustrating a first setting example of a transfer path between RE2 and REC3 in the fronthaul network 100. For example, the transfer route R1 represents a transfer route starting from RE2-1 and arriving at REC3 in the order of node 1-1, node 1-4, and node 1-8. In FIG. 2, for the sake of simplicity, only the route from RE2 to REC3 is shown, but actually, the route from REC3 to RE2 is set in the same manner. Hereinafter, “flow n” (n is an integer of 1 or more) represents the traffic of RE1-n.

  FIG. 3 is a block diagram illustrating a specific example of a functional configuration of the node 1 in the first embodiment. 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 functions as a device including a switching unit 11, an output queue 12, an output unit 13, an estimation unit 14, and a transfer control unit 15 by executing a program. Note that all or some of the functions of the node 1 may be realized by using hardware such as an application specific integrated circuit (ASIC), a programmable logic device (PLD), or a field programmable gate array (FPGA). 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, a CD-ROM, or a storage device such as a hard disk built in the computer system. The program may be transmitted via a telecommunication line.

  The switching unit 11 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. The received frames output from the switching unit 11 are accumulated in the output queue 12 in the output queue 12 corresponding to each output port. FIG. 3 shows output queues 12-1 to 12-8 as examples of the output queue 12 corresponding to each output port. Hereinafter, the received frame is referred to as a flow.

  The output unit 13 reads the flow from the output queue 12 and outputs the read flow to a communication unit (not shown) corresponding to the transfer destination. For example, the output unit 13 reads a flow from each output queue 12 by a round robin (RR) method. Note that the order in which flows are read from each output queue 12 may be determined by a weighted round robin (WRR) method in which a weight assigned to each output queue 12 is reflected in the read order.

  Based on the number of flows that flow into the device at the same timing (hereinafter referred to as “number of inputs”), the estimation unit 14 estimates an index value related to the magnitude of the competition delay that occurs in the transfer process of the flow group that has flowed in. The estimation unit 14 notifies the transfer control unit 15 of the estimated index value.

  The transfer control unit 15 controls the transfer path of the input flow based on the index value related to the magnitude of the competition delay estimated by the estimation unit 14. Specifically, the transfer control unit 15 uses a predetermined threshold value for all the competition flows, and the total delay time of each competition flow calculated based on the competition delay estimated by the estimation unit 14, the processing delay, and the propagation delay. Select the following transfer path.

  FIG. 4 is a diagram illustrating an operation example of the node 1 in the first setting example. FIG. 4 shows an operation example of transfer processing by the node 1-4 shown in FIGS. As shown in FIG. 1, the node 1-4 has first to fourth links between the node 1-1, the node 1-3, the node 1-5, and the node 1-8. FIG. 4 shows a situation in which flows 1 and 2 from the first link, flow 3 from the second link, and flow 5 from the third link flow into the node 1-4.

  Here, bursts B1, B2, B3 and B5 represent bursts of flow 1, flow 2, flow 3 and flow 5, respectively. A burst is a unit that represents a group of a plurality of packets transmitted together in each flow. Here, the maximum burst length transmitted from RE2 in one period of the uplink transmission period in TDD is m. Furthermore, in the following, it is assumed that the burst length of each flow is m in order to take into account the e2e delay that can occur.

  In this case, all bursts that have flowed into the node 1-4 are transferred to the output port by the switching function. At this time, each burst is queued in the output queue 12 for each flow and read out in a round robin manner. The read flow is output to an output port corresponding to the destination of the flow. For example, in the node 1-4, information indicating a correspondence relationship between each output port and a VLAN-ID (Virtual LAN IDentifier) is stored in advance. In this case, the output unit 13 identifies an output port serving as a transfer destination of the frame based on the VLAN-ID described in the received frame. With such a switching function, in a situation where the transfer path between each RE2 and REC3 is set as in the example of FIG. 2, for example, all the flows that have flowed into the node 1-4 are output from the fourth link. Here, as an example, the configuration in which the output queue 12 is provided for each flow is shown, but the configuration of the output queue 12 is not limited to such a configuration.

In the node 1 that performs such transfer processing, an input flow having the Lth link as a transfer destination is defined as a competitive flow, and a link to which the competitive flow is input is defined as a competitive link. Here, a set of competing links represented as G _L, to represent the identifier of the competition links in G _L in k. Furthermore, a set of competitive flows that are input from the competitive link (competitive link k) identified by the identifier k and transferred to the L-th link are represented as F _k .

Hereinafter, the number of elements in the set A is represented as #A. In addition, the maximum value among the values of the elements included in the set A is expressed as Max (A). Sum (A) represents the sum of the values of the elements of the set A. For example, set A _{{A 1, A 2, ...} , A n} if with each element of, Max (A) is _{{A 1, A 2, ...} , A n} represents the maximum value among, Sum (A) becomes (A ₁ + A ₂ +... + A _n ).

The node 1 has the largest competition delay when competition flows start to be input simultaneously from all the competition links. Hereinafter, the competitive flow that is input first at this timing is referred to as a “first flow”. In particular, the competition delay is particularly large when bursts of each competition flow included in F _k (burst length of each competition flow is m) are continuously input in each competition link k. At this time, the competition flow that experiences the longest competition delay is a competition flow that is input last in a series of continuously input competition flows (hereinafter referred to as “last flow”). This is because the last flow waits for completion of transfer of the flow input before itself. The number of flows that the last flow waits is set as the maximum competition number λ _L.

If the time required to input a competitive flow with a burst length m is counted as one slot, Max (#F _k ) (k = 1, 2,...) Slots from the start of input of the first flow to the end of input of the last flow. is required. That is, while the competitive flow number Sum (#F _k ) (k = 1, 2,...) Is input, a flow of Max (#F _k ) (k = 1, 2,...) Is output. Therefore, the number of flows λ _L that the last flow waits for its own transfer is expressed as Sum (#F _k ) −Max (#F _k ). Here, when the link speed of the L-th link is e _L and the maximum competition delay is d _L , the maximum competition delay is obtained as d _L = mλ _L / e _L.

In FIG. 4, the competitive flows with the fourth link as the transfer destination are flow 1, flow 2, flow 3, and flow 5. (For i.e. L = 4) In this case, the elements of competition link set G ₄ to enter these competition flows, the first link, a second link and the third link. Thus, the competitive flow transferred to the fourth link is represented as F ₁ , F ₂ and F ₃ for each competitive link.

At this time, F ₁ = {Flow 1, Flow 2}, F ₂ = {Flow 3}, and F ₃ = {Flow 5}. FIG. 4 shows a situation in which inputs having the flow 1, the flow 3 and the flow 5 as the first flow are started simultaneously in the first link, the second link, and the third link. In this case, the last flow in the first link is flow 2.

In this case, the number of competitive flows Sum (#F _k ) (k = 1, 2, 3) = 2 + 1 + 1 = 4, and while these are input, Max (#F _k ) (k = 1, 2, 3) = Max (2, 1, 1) = 2 is output. That is, the maximum competition number λ ₄ that the last flow waits is Sum (#F _k ) −Max (#F _k ) = 4-2 = 2. The maximum competition delay at this time is d ₄ = 2 m / e ₄ .

  FIG. 5 is a diagram illustrating a second setting example of the transfer path between RE2 and REC3 in the fronthaul network 100. FIG. 6 is a diagram illustrating an operation example of the node 1 in the second setting example. The difference between the second setting example shown in FIG. 5 and the first setting example shown in FIG. 2 is that the flow 5 does not go through the node 1-4 but goes through the nodes 1-6 and 1-7. Is a point. Due to this difference, FIG. 6 shows a situation where the flow 1 and the flow 2 from the first link and the flow 3 from the second link flow into the node 1-4.

Compared to the first setting example, there is no flow input from the third link in the second setting example. Therefore, in the second setting example, the number of competitions in the node 1-4 is reduced. At this time, the competitive flows with the fourth link as the transfer destination are flow 1, flow 2 and flow 3. Also, competition link set G ₄ are composed of first and second links. In this case, F ₁ = {Flow 1, Flow 2} and F ₂ = {Flow 3}.

FIG. 6 shows a situation in which inputs of flow 1 and flow 3 are started simultaneously as head flows. The last flow at this time is flow 2. In this case, the number of competitive flows Sum (#F _k ) (k = 1, 2) = 2 + 1 = 3, and while these are input, Max (#F _k ) (k = 1, 2) = Max ( A flow of 2, 1) = 2 is output. That is, the maximum competition number λ ₄ that the last flow waits is Sum (#F _k ) −Max (#F _k ) = 3−2 = 1. The maximum competition delay at this time is d ₄ = m / e ₄ .

The node 1 according to the first embodiment configured as described above has the number of competitive flows input Sum (#F _k ) by the competitive link and the competitive flow in the communication link that inputs the most competitive flows among the competitive links. By providing the estimation unit 14 that estimates the maximum delay time due to the competition flow transfer process based on the number of inputs Max (#F _k ), the delay time of the traffic that propagates in the network in which the competition delay may occur Can be guaranteed.

  Specifically, the transfer control unit 15 can use the competition delay estimated in advance for route setting or the like. In the present embodiment, it can be seen that, for example, the first setting example has a smaller competition delay in the node 1-4 than the second setting example. Thus, by calculating the competition delay in each link, the e2e delay of the set transfer path can be calculated and compared. If such a comparison becomes possible, the node 1 can select an optimum transfer path in consideration of the competition delay, and therefore, the e2e delay can be reduced.

<Second Embodiment>
The configuration of the fronthaul network 100 in the second embodiment is the same as the configuration in the first embodiment shown in FIG. The difference between the second embodiment and the first embodiment is that the link speed is different between the competitive link and the output link. The node 1 in the second embodiment can calculate the maximum competition delay even when the link speed is different between the competitive link and the output link. Specifically, in the second embodiment, the estimation unit 14 of the node 1 calculates the maximum competition delay by the following method.

As described in the first embodiment, a Max (#F _k ) slot is required from the start of input of the first flow to the end of input of the last flow. If the link speed of the output link is e _L and the link speed of the competitive link is e _C (≠ e _L ), the number of flows output during this period is Max (#F _k ) × e _L / e _C. . Therefore, the maximum competition number λ _L is expressed as Sum (#F _k ) −Max (#F _k ) × e _L / e _C. With such a calculation method, the estimation unit 14 can calculate a competition delay in consideration of a difference in link speed.

<Modification>

  You may make it implement | achieve the node 1 in embodiment mentioned above with 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 into a computer system and executed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory inside a computer system serving as a server or a client in that case may be included and a program held for a certain period of time. Further, the program may be a program for realizing a part of the above-described functions, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system. You may implement | achieve using programmable logic devices, such as FPGA (Field Programmable Gate Array).

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

  The present invention is applicable to a communication apparatus that has a plurality of communication links and executes a transfer process for transferring an input flow input from a part of the plurality of communication links to a communication link according to the destination of the input flow. .

DESCRIPTION OF SYMBOLS 100 ... Front hall network, 101 ... 1st network, 102 ... 2nd network, 1,1-1 to 1-8 ... Node, 11 ... Switching part, 12, 12-1 to 12-8 ... Output queue, 13 ... Output unit, 14 ... estimation unit, 15 ... transfer control unit, 2 ... RE (Radio Equipment), 3 ... REC (Radio Equipment Controls), B1, B2, B3, B5 ... Burst of competitive flow

Claims (4)

A communication apparatus that has a plurality of communication links and executes a transfer process of transferring an input flow input from a part of the plurality of communication links to a communication link according to a destination of the input flow;
The first input number that is the number of inputs of the competitive flow by the competitive link, where the input flow that is input at the same timing and transferred to the same communication link is the competitive flow, the communication link that inputs the competitive flow is the competitive link And a second input number that is the number of competitive flow inputs in the communication link that inputs the most competitive flows among the competitive links, and an estimation unit that estimates a maximum delay time due to the competitive flow transfer process Comprising
Communication device. A transfer path control unit that sets a transfer path of the input flow based on the maximum delay time estimated by the estimation unit;
The communication apparatus according to claim 1. When the first input number is N, the second input number is n, the maximum burst length of the contention flow is m, and the link speed of the destination communication link is e, the estimation unit The delay time d is calculated by the following equations (1) and (2).

The communication apparatus according to claim 1 or 2. The estimation unit is configured such that the first number of inputs is N, the second number of inputs is n, the maximum burst length of the contention flow is m, the link speed of the contention link is c, and the link speed of the destination communication link Where e is the maximum delay time d according to the following equations (3) and (4):

The communication apparatus according to claim 1 or 2.

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