KR20060040637A - Optical Piggyback Switching Method and Switching Node Structure Based on Wavelength Division Multiplexing - Google Patents

Abstract

The present invention relates to an optical piggyback switching method and an optical piggyback switching node structure based on wavelength division multiplexing for large capacity and reliable data transmission. That is, the present invention relates to optical piggyback switching, which is a new switching technique in optical networks. In the optical splitting switching method based on wavelength division multiplexing, a backbone WDM (Wavelength Division Multiplexing) for processing a large amount of traffic IP packets applied to the network and input to the piggyback switching node are collected in the standby buffer and then transmitted to the destination through the framing by optical signals. In order to reduce the packet delay, a signaling method for this purpose is to use a bidirectional signaling technique rather than the one-way signaling technique used in the optical burst switching technique, and thus, it is possible to transmit a plurality of data simultaneously with one signaling. In addition, the node-to-node elastic resource reservation scheme can solve the high loss rate problem, which is the biggest disadvantage of the optical burst switching technique, by realizing a high utilization rate per channel compared to the conventional wavelength switching.

Wavelength Division Multiplexing, Optical Piggyback Switching, Bidirectional Signaling, Elastic Resource Reservation

Description

OPPICAL PIGGYBACK SWITCHING METHOD BASED ON WAVELENGTH DIVISION MULTIPLEXING AND SWITCHING NODE STRUCTURE}

1 is a block diagram of an optical piggyback switching network in a wavelength division multiplexing network according to an embodiment of the present invention;

2 is a structural diagram of an optical piggyback switch node according to an embodiment of the present invention;

3 is a diagram illustrating a signaling and data transmission process between a source node and a destination node according to an embodiment of the present invention;

4 is a graph comparing average loss ratios of packets according to an embodiment of the present invention;

5 is a graph comparing average delay times of packets according to an embodiment of the present invention;

6 is a graph comparing average bandwidth utilization according to an embodiment of the present invention.

<Brief description of the major symbols in the drawings>

9: demultiplexer 12: optocoupler

11: switch control unit 13: On / Off switch

14: local drop portion 15: switch fabric

18: local adder 16: optical wavelength converter

17: multiplexer

The present invention relates to an optical switching method in an optical network using wavelength division multiplexing. In particular, an optical piggyback switching method and an optical piggyback switching node structure based on wavelength division multiplexing for large capacity and reliable data transmission It is about.

In recent years, due to the rapid development and demand of the Internet industry, the Internet traffic is rapidly increasing every year, and the existing Internet technology cannot be accommodated. However, with the development of Dense Wavelength Division Multiplexing (DWDM) technology and the development of fiber amplifiers, it is now possible to transmit several terabytes of information simultaneously on a single fiber. As a result, IP / WDM-type optical Internet is attracting worldwide attention, and optical fiber technology, wavelength division multiplexing technology (WDM), optical device technology (optical amplifier, optical switching device) for constructing more efficient and economical optical internet network Related technologies such as optical switching technology have been steadily being developed.

In line with the current tide, the Broad Convergence Network (BcN) project, the next-generation Internet network project that the government is promoting to accommodate the explosive growth of IP traffic, is a quality broadband broadband service that converges telecommunications, broadcasting, and the Internet. Can be defined as a next-generation converged network that can be used securely and broadband anywhere, anytime.

In order to guarantee the above broadband service, research institutes and academia are considering optical transmission network with optical interface as All-IP backbone network, and optical switching technology such as optical wavelength switching, optical burst switching, and optical packet switching have. The switching techniques have different advantages and disadvantages due to their switching characteristics.

First, in the case of optical wavelength switching technology, reliable data transmission is possible because bidirectional-based signaling is used, but since a node exclusively uses a channel, it has to have a very low channel utilization rate. There is a limit. In addition, optical packet switching technology, which is considered as the ultimate optical internet switching technique, can efficiently use resources through statistical multiplexing, but due to technical limitations (optical memory, optical signal processing), commercialization of optical packet switching technology will take a long time. It is thought to be.

Finally, the optical burst switching technology is proposed to overcome the disadvantages of low bandwidth utilization of the optical wavelength switching and high complexity of the optical packet switching technology. The optical packet is not required and the control packet containing all the information is electrically processed. Information can be transmitted end-to-end without optical / electric conversion.

Such optical burst switching uses unidirectional signaling such as Just-enough-time (JET) and Just-in-time (JIT), and data bursts are sent along the corresponding burst control packet without waiting for acknowledgment (Ack) packets. However, optical burst switching technology has overcome some of the shortcomings of conventional switching techniques. However, due to the high loss rate resulting from unidirectional signaling, it is still difficult to put into practical use. It was not enough to lower the high loss rate resulting from signaling.

Therefore, in order to effectively lower the loss rate, it is necessary to use a bidirectional signaling technique instead of unidirectional signaling. In addition, in order to increase the utilization of resources, high resource utilization can be obtained by reserving only the size of data to be transmitted rather than reserving the entire channel as in optical wavelength switching. However, when resource reservation is made by using a bidirectional signaling technique for each data that is to be transmitted, a delay occurs during a round trip time (RTT) time of signaling information, thereby having a high packet delay.

Accordingly, an object of the present invention is to achieve a high resource utilization rate by greatly reducing the loss rate using the bidirectional signaling technique and reserving only the size of data to be transmitted in the switching method in the optical network using wavelength division multiplexing. The present invention provides an optical piggyback switching method based on wavelength division multiplexing and an optical piggyback switching node structure for data transmission that can secure a large capacity and reliability by solving packet delay through interleaved signaling.

The present invention for achieving the above object is an optical piggyback switching method using bidirectional signaling in an optical network using wavelength division multiplexing, (a) from the source node of the optical network to the destination node to which data packets are to be transmitted. Transmitting a control packet for band reservation to all intermediate nodes in the path, (b) reserving an available band at each intermediate node to a destination node according to a band request through the control packet, and (c Transmitting an Ack packet to the source node at the destination node when a band is successfully reserved on each link of the intermediate node; and (d) configuring the segments based on reservation information of the Ack packet at the source node. Generating a burst of data, and (e) the burst of data generated from the source node is applied to each intermediate node on a transmission path. Drop of the segments / Ad as is performed characterized in that it comprises the step that is sent to the destination node.

In addition, the present invention is an optical piggyback switching node structure using bidirectional signaling in an optical network using wavelength division multiplexing, and demultiplexing to demultiplex multiple wavelength multiplexed WDM signals transmitted from any source node of the optical network. A 1: 2 optical coupler for separating the optical signal passing through the demultiplexer into 1: 2, a switch fabric for switching the demultiplexed optical signal, and a data burst of the demultiplexed optical signal A local drop section for dropping the segment separated from the intermediate node, a local add section for adding a segment added at the intermediate node to a data burst of the optical signal switched from the switch fabric, and an optical signal switched from the switch fabric And convert the data segment added from the local adder into the optical wavelength And an optical wavelength converter, and characterized in that it comprises a multiplexer and, a switch control unit for controlling a switching operation of the switch fabric to multiplex the light wavelength-converted data burst optical signal from the optical wavelength converter of.

Hereinafter, with reference to the accompanying drawings will be described in detail the operation of the preferred embodiment according to the present invention.

In the optical piggyback switching technology of the present invention, a bidirectional signaling technique having a flexible resource reservation scheme and a piggyback transmission characteristic is adopted. Hereinafter, the main features of the optical piggyback switching will be described.

First, the elastic resource reservation scheme will be described. In general, the optical burst switching scheme reserves only the bandwidth required for data transmission. If no resources are available for the exact time interval of the required resource, the switch simply discards the input data. In the optical piggyback switching scheme, when there is no resource in the switch for the exact time interval of the required resource, the switch reserves the maximum available resource within the time interval and re-adjusts or acknowledges the reserved resource in the acknowledgment period. The elastic resource reservation scheme enables the transmission data size to be determined dynamically based on the availability of network resources. By reducing the existing strict resource reservation scheme and operating flexibly, the packet loss rate can be greatly reduced.

Next, the piggyback transmission scheme includes not only the band request for the destination node but also the band request to all intermediate nodes in the path to the destination when generating a control packet of the band request at the source node. Thus, data to all intermediate nodes existing on the route to the destination are collected and generated in one huge burst. As part of the burst, data to be sent to a particular intermediate node is defined as a segment, and each segment is passed to that intermediate node. In addition, when the control packet generated by the source arrives at the intermediate node on the path, the intermediate node may transmit its bandwidth request to the downstream node in a control packet.

Next, interleaved signaling refers to a signaling method for transmitting a control packet by predicting an amount of input data in advance in order to reduce transmission delay, which is a disadvantage of bidirectional based signaling. The basic assumption of interleave signaling starts from the assumption that the amount of aggregated traffic at the backbone node changes very slowly over time, so that the amount of input traffic can be predicted. Basically, interleaved signaling may be applied when the RTT time between the source node and the destination node is large.

1 is a block diagram of an optical piggyback switching network in a wavelength division multiplexing network according to an exemplary embodiment of the present invention. In the present invention, a four-hop optical path is illustrated to describe the optical piggyback switching method in detail. Let's explain.

에서부터

까지 예약을 한다. 여기서

는 노드 i에서 노드 j로 보내기 위한 데이터의 양으로서 현재 버퍼의 크기를 의미한다. Referring to FIG. 1, N1 (1) is a source node and N4 (4) is a destination node. At any time t node N1 (1) will send a control packet to reserve the band on the link on the path to each destination node. First, the control packet then times the band on link 1 (5).

From

Make a reservation by here

Is the amount of data to send from node i to node j, which is the size of the current buffer.

로부터 t+δ+

까지 예약한다. 여기서 δ 는 제어패킷의 처리 시간이고 σ는 링크의 전달 지연시간이다. 만약 모든 대역 요청이 링크 1(5), 링크 2(6), 링크 3(7)에서 성공적으로 예약되면 목적지 노드 N4(4)는 Ack 패킷을 소스노드 N1(1)으로 보내게 된다. The control packet then arrives at node N2 (2) at time t + δ + σ and switches the band of link 2 (6) at time t + δ +.

From t + δ +

Book by. Where δ is the processing time of the control packet and σ is the propagation delay time of the link. If all band requests are successfully reserved on link 1 (5), link 2 (6) and link 3 (7), then destination node N4 (4) sends an Ack packet to source node N1 (1).

At this time, the Ack packet plays a role of re-confirming a reserved band while canceling an unnecessary band while passing through intermediate nodes on a path, and includes band reservation information of each link. Based on the reservation information of the Ack packet, the source node N1 (1) generates a data burst 8, which is composed of data (segments) 9 for all downstream nodes on the path. In other words, one burst consists of several segments, each of which is a collection of data transmitted from one node to another. Each segment is separated from the corresponding intermediate node and dropped, and the intermediate nodes add segments according to the reservation information to be sent to a node located in a direction more than that. The great advantage of this piggyback transmission scheme is that the signaling overhead can be greatly reduced as a plurality of segments are transmitted through one signaling, compared to the conventional scheme of transmitting signaling signals for each segment.

2 illustrates a node structure supporting the optical piggyback switching scheme according to an embodiment of the present invention.

)(11)은 스위치 제어부(switch control unit)(13)에서 전기적으로 처리되며 광 커플러(12)는 스플리터(splitter)로 사용되고 광 신호를 1:2로 분리하는 기능을 한다. 스플리터의 출력 양단자에는 각각 On/Off 스위치(14)가 연결되어 있다. 만약 입력 버스트의 일부 세그먼트들이 해당 노드에서 드롭(drop) 되어져야 한다면 로컬 드롭부(local drop)(15) 방면의 on/off 스위치는 드롭(drop) 되어야할 세그먼트의 시간 동안 온(on) 상태로 조정되고 그렇지 않으면 on/off 스위치는 오프(off) 상태로 남아 있는다. 이와는 반대로 스위치 패브릭(16)쪽의 on/off 스위치에서는 드롭(drop) 되어야할 세그먼트 부분에서는 오프(off)되고 나머지 세그먼트 부분에서는 온(on)되어 스위치를 통과 할 수 있게 된다. 자원예약 정보에 따라 해당 노드에서 애드(add)되는 데이터와 파장 변환기(wavelength converter)(17) 및 다중화기(18)를 거쳐 다중화된 신호는 하향 노드로 전송된다. Referring to FIG. 2, a wavelength division multiplexing (WDM) signal multiplexed with multiple wavelengths is demultiplexed at the input port 10. Control wavelength (

11 is electrically processed by a switch control unit 13, and the optical coupler 12 serves as a splitter and splits an optical signal 1: 2. On / Off switch 14 is connected to both output terminals of the splitter. If some segments of the input burst are to be dropped at that node, the on / off switch toward the local drop 15 remains on for the time of the segment to be dropped. Otherwise the on / off switch remains off. On the contrary, in the on / off switch on the switch fabric 16, the segment part to be dropped is turned off and the other segment part is turned on so that it can pass through the switch. The data added from the corresponding node according to the resource reservation information and the multiplexed signal through the wavelength converter 17 and the multiplexer 18 are transmitted to the downlink node.

3 is a diagram illustrating an elastic reservation scheme which is a signaling protocol of optical piggyback switching according to an embodiment of the present invention. In the present invention, for convenience of explanation, the case where the available band of the intermediate node is smaller than the required band will be described as an example.

That is, if the available band of the intermediate node is smaller than the required band as above, the intermediate node reserves only 24 available bands in the set up step 22. When the control packet reaches the destination node N4 (4), the destination node N4 (4) determines the size and position of the segments, which are components of the burst, based on the available band information of all intermediate nodes on the path. This burst configuration information is stored in the Ack packet and forwarded upward (23). As soon as the intermediate nodes N2 (2) and N3 (3) receive the Ack packet, they finally confirm the resource reservation according to the determined bandwidth reservation information (25), and if the determined bandwidth reservation period is greater than the bandwidth reserved in the set up phase, If it is small, the remaining band is canceled (27). In addition, when the burst is configured at the destination node N4 (4), the data of the upstream node on the path has a higher priority than the data of the downlink node.

The source node N1 (1) receiving the Ack packet generates one burst 28 consisting of three data segments for the intermediate node N3 (3), the destination node N4 (4), and the intermediate node N2 (2). The data segment 29 for node N2 (2) is dropped at node N2 (2) and the remaining bursts are switched at the light level without photoelectric conversion. Although node N2 (2) has a data segment to be sent to nodes N3 (3) and N4 (4), the segment is already unavailable for another burst because the segment is already unavailable for another burst (26). It cannot be added. On the other hand, the node N3 (3) can see that the data segment to be transmitted to the node N4 (4) is added. It is noteworthy here that the size of the data segment added at the intermediate node is dynamically determined by the available bandwidth of each link. Therefore, in the optical piggyback switching method of the present invention, the elastic resource reservation scheme may not only increase the bandwidth utilization but also increase the probability of success of data forwarding.

4 shows the average loss rate of IP packets present in a segment. In the present invention, to measure the performance of the optical piggyback technique, NSFNET consisting of 14 nodes is configured as a simulation network topology. Each link has one control wavelength and three data wavelengths. 10Gbps.

The IP packet arrives at each node with the Po and Song distribution of arrival rate λ. When one segment is longer than 100ms or the timer time of a specific segment is longer than 50ms, each node generates a control packet to transmit the segment. Send to the destination node. In this case, due to the piggybacked segment and the elastic resource reservation scheme, the size of the data burst is determined dynamically, and the intermediate nodes in the path do not have a buffer for the simple passing burst. The performance of the optical burst switching technique is compared with the JET and Tell-and-Wait (TAW) techniques. The JET scheme is one of the typical optical burst switching schemes and is a one-way signaling-based switching technique. TAW is a two-way signaling-based protocol and does not consider data piggyback transmission and elastic resource reservation.

In general, since the TAW and optical piggyback switching techniques do not cause packet loss during data transmission, the data is considered to be discarded when the data delay time, which is caused by resource contention during signaling, is greater than 150ms. Under these circumstances, the loss rate of optical piggyback switching is significantly lower than that of JET and TAW. This is because the probability of data forwarding success and the bandwidth utilization are increased through the piggyback data transmission and the elastic resource reservation scheme.

Figure 5 shows the delay time of the end-to-end average IP packet according to the load of the input traffic. As shown in FIG. 5, since the optical piggyback switching is bidirectional signaling based, the average packet delay is larger than that of the JET. However, piggyback data transmission does not require queuing delays such as packet assembly delay of piggybacked segments, and the elastic resource reservation scheme has a smaller average delay time compared to TAW because it increases the data transmission opportunity. Furthermore, the application of interleaved signaling to the optical piggyback switching technique is further reduced.

6 compares the bandwidth utilization according to the input load. As shown in FIG. 6, the elastic resource reservation scheme of the optical piggyback switching scheme dynamically determines the burst size based on the available resource information on the path, thereby decreasing the bandwidth utilization in the JET and TAW techniques. It generates at least, which is superior to other techniques in terms of bandwidth utilization.

As a result, optical piggyback switching showed better packet loss rate, signaling overhead, and bandwidth utilization than JET and TAW. In addition, although the average packet delay time of the optical piggyback switching scheme is larger than that of JET, it is considerably smaller than that of TAW and slightly larger than that of JET using interleaved signaling. Therefore, the optical piggyback switching technique has a little packet delay than the JET technique, but it can be seen that it is an optical switching technique that increases the possibility of practical use by enabling more reliable transmission and efficient bandwidth use.

Meanwhile, in the above description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the invention should be determined by the claims rather than by the described embodiments.

As described above, the present invention relates to optical piggyback switching, which is a new switching technique in an optical network. In the optical splitting switching method based on wavelength division multiplexing, a backbone WDM ( It is applied to a Wavelength Division Multiplexing (IP) network, and the IP packets input to the piggyback switching node are collected in the standby buffer and then transmitted through the framing to the optical signal to the destination. In order to reduce the packet delay, a signaling method for this purpose is to use a bi-directional signaling technique rather than the one-way signaling technique used in the optical burst switching technique, which enables more reliable transmission. have. In addition, the node-to-node elastic resource reservation scheme shows higher utilization per channel than conventional wavelength switching, and has the advantage of solving the high loss rate problem, which is the biggest disadvantage of the optical burst switching technique.

Claims (5)

An optical piggyback switching method using bidirectional signaling in an optical network using wavelength division multiplexing, (a) transmitting a control packet for band reservation to all intermediate nodes in the path from a source node of the optical network to a destination node to which a data packet is to be transmitted; (b) reserving an available band at each intermediate node to a destination node according to a band request through the control packet; (c) transmitting an Ack packet to the source node at the destination node when a band is successfully reserved on each link of the intermediate node; (d) generating a data burst composed of segments based on reservation information of the Ack packet at the source node; (e) transmitting the burst of data generated from the source node to the destination node by dropping / adding a segment at each intermediate node on a transmission path; Wavelength division multiplexing based optical piggyback switching method comprising a. The method of claim 1, In step (a), the band request of the control packet includes a band request for the destination node only and a band request to all intermediate nodes in the path to the destination node. Multiplexing based optical piggyback switching method. The method of claim 1, In the step (c), the destination node dynamically determines the size and position of the segments that constitute the data burst based on the available band information of all the intermediate nodes and includes them in the Ack packet to be transmitted to the source node. An optical piggyback switching method based on wavelength division multiplexing. The method of claim 3, The Ack packet includes bandwidth reservation information on each inter-node link for reconfirming a reserved band at each intermediate node or canceling an unnecessary band while passing through the intermediate nodes on a path. Multiplexing based optical piggyback switching method. An optical piggyback switching node structure using bidirectional signaling in an optical network using wavelength division multiplexing, A demultiplexer for demultiplexing multiplexed WDM signals transmitted from any source node of the optical network; A 1: 2 optical coupler for separating the optical signal passing through the demultiplexer into 1: 2, A switch fabric for performing switching on the demultiplexed optical signal; A local drop unit for dropping a segment separated from a corresponding intermediate node from a data burst of the demultiplexed optical signal; A local adder configured to add a segment added at a corresponding intermediate node to a data burst of an optical signal switched from the switch fabric; An optical wavelength converter for optically converting an optical signal switched from the switch fabric and a data segment added from the local add portion; A multiplexer for multiplexing an optical wavelength converted data burst optical signal from the optical wavelength converter; Switch control unit for controlling the switching operation of the switch fabric Wavelength division multiplexing based optical piggyback switching node structure comprising a.

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