CN1717113A - Photoelectric mixed exchanging struture supporting light burst/group exchanging - Google Patents
Photoelectric mixed exchanging struture supporting light burst/group exchanging Download PDFInfo
- Publication number
- CN1717113A CN1717113A CNA2004100401111A CN200410040111A CN1717113A CN 1717113 A CN1717113 A CN 1717113A CN A2004100401111 A CNA2004100401111 A CN A2004100401111A CN 200410040111 A CN200410040111 A CN 200410040111A CN 1717113 A CN1717113 A CN 1717113A
- Authority
- CN
- China
- Prior art keywords
- optical
- output
- wavelength
- input
- switching
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 230000003287 optical effect Effects 0.000 claims abstract description 133
- 239000000872 buffer Substances 0.000 claims abstract description 48
- 239000011159 matrix material Substances 0.000 claims description 42
- 239000013307 optical fiber Substances 0.000 claims description 23
- 239000004744 fabric Substances 0.000 claims description 17
- 230000005693 optoelectronics Effects 0.000 claims 1
- 230000005684 electric field Effects 0.000 abstract description 5
- 230000005540 biological transmission Effects 0.000 description 28
- 238000000034 method Methods 0.000 description 11
- 238000010586 diagram Methods 0.000 description 9
- 238000005516 engineering process Methods 0.000 description 8
- 230000006870 function Effects 0.000 description 6
- 230000000903 blocking effect Effects 0.000 description 5
- 230000003111 delayed effect Effects 0.000 description 5
- 238000012545 processing Methods 0.000 description 5
- 230000011664 signaling Effects 0.000 description 5
- 230000003139 buffering effect Effects 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 239000002131 composite material Substances 0.000 description 4
- 238000013459 approach Methods 0.000 description 2
- 238000004891 communication Methods 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 230000003313 weakening effect Effects 0.000 description 1
Images
Landscapes
- Optical Communication System (AREA)
- Data Exchanges In Wide-Area Networks (AREA)
Abstract
This invention provides a photoelectric mixed exchange structure supporting light burst/packet exchange, which takes optical exchange as the main thing and applies a buffer storage channel composed of a photoelectric converter, RAM buffer storage and an electro optical converter connected by electric field, takes electric-field buffer storage to replace light buffer storage (FDL) and adds with suitable electric-field exchange. This invention utilizes electric-field buffer storage to solve conflict effectively, which is the main reason for loosing data in optical network.
Description
Technical Field
The present invention belongs to the technical field of switching control in a communication system, particularly to a switching structure of a core node in an optical burst/packet switching network.
Background
With the size of the internet and the exponential growth of internet traffic, the demand for network bandwidth has increased dramatically, and thus the demands on the transmission capacity of the network and the processing capacity of routers and switches have increased. Dense Wavelength Division Multiplexing (WDM) technology can multiplex a plurality of Wavelength channels on one optical fiber, and greatly improves the transmission capacity of a single optical fiber. By using the method, a broadband basic network meeting the growth of Internet services can be established, and the problem of network transmission is well solved. The current technology can multiplex 80-120 wavelengths on one fiber for a total transmission capacity of about 400 Gb/s.
On this basis, four techniques for transmitting data over WDM networks have been developed: broadcast-selective reception, wavelength routing, Optical Burst Switching (OBS), Optical Packet Switching (OPS). The wavelength routing provides a switching granularity (basic switching unit) of wavelength, which is not suitable for transmitting packet services with strong burstiness, and needs to overlay a hierarchical structure of combining internet packet services, thus increasing the complexity of the system and reducing the transmission efficiency. To reduce complexity and increase efficiency, it is desirable to transmit IP layer data directly over WDM optical networks, which is a major cause of the advent of optical burst switching and optical packet switching technologies. Among them, the all-optical packet switching technology is considered as the most fundamental method for overcoming the processing bottleneck of the traditional electrical switching, but at present, the technology has several difficulties, such as all-optical storage, optical timing/synchronization, and the like. Therefore, the advantages of the existing optical and electrical technologies are fully combined and exerted, the optical and electrical hybrid switching system is constructed, and the method is an effective method for realizing a large-capacity switching system, such as an Optical Burst Switching (OBS) technology, and effectively combines the advantages of wavelength routing and optical packet switching.
In an optical Burst switching network, Burst data (Burst) carrying user traffic can be regarded as a very long Packet consisting of a large number of data packets, and a Packet Header of the very long Packet is a control Packet (BHP) of the Burst data. The BHP contains information about the burst data, such as Offset Time (i.e. the Time interval between the source sending the BHP and the corresponding burst data), burst length, data channel (wavelength), etc. Unlike conventional packet switching, BHP is separated from the burst data on the physical channel, i.e. using out-of-band signaling: in a dense wavelength division multiplexing transmission system, one (or more) dedicated wavelength channels may be used as a control channel for transmitting BHP, while other wavelength channels are used as data channels, and there is a one-to-one correspondence between BHP and burst data.
In the optical burst switching, in order to reduce the delay of connection establishment and improve the channel utilization, a one-way reservation mechanism is generally adopted, that is, before a source end really sends burst data, a BHP is sent first, and after a certain offset time, the burst data is sent, so that the BHP first reaches an intermediate switching node of the optical burst switching network to perform resource reservation. BHP is converted into an electrical signal at the intermediate switching node for processing, including reservation of output port wavelength, configuration of switching matrix, etc., to ensure that when burst data arrives, the corresponding all-optical data channel is already configured, thereby implementing transparent transmission of data in the optical domain. BHP is also referred to as a signaling message in the sense that it is very similar to signaling in a conventional circuit-switched network in terms of the functions performed. However, unlike the conventional signaling, the optical burst switching signaling is a unidirectional reservation mechanism without waiting for the feedback acknowledgement of the destination.
As is known, nodes in a network must have the ability to output incoming data from a particular output channel at a particular time, as opposed to point-to-point transmission lines, a capability called switched data, which is implemented by a particular switching fabric. The capabilities of different switch fabrics for switching are greatly different, so the performance of the network is directly affected by the quality of the switch fabrics.
An optical burst switched network is mainly composed of edge nodes, core nodes and DWDM links (see fig. 1). The DWDM link includes a Control Channel (Control Channel) and a Data Channel (Data Channel). The structure of the core node is schematically shown in figure 2. All modules above the optical Switch module are collectively called a Switch Control Unit (SCU), and Control the operation of the optical Switch module so that the burst data can pass through correctly. And the optical switching matrix will switch the burst data on the assigned wavelength channel of the assigned input port to the corresponding output wavelength channel at the assigned time according to the instruction of the switching control unit. The architecture of BHP and burst separation avoids the need to convert all data to the electrical domain at the core node and also avoids the use of large amounts of memory. For the core nodes of the optical burst switching network and the optical packet switching network, the optical switching module has universality, and the optical switching module in the optical burst switching is only taken as an example in the following. Meanwhile, the present invention focuses on the optical switching module, and thus the switching control unit is omitted in the following description.
The existing optical switching modules mainly include the following: (see Lisong Xu, Harry G. Perros, and George Rouskas, North Carolina State University, "Techniques for Optical Package Switching and Optical Burst Switching", IEEE Communications major January 2001, Volume: 39, Issue: 1, Jan.2001, Pages: 136-)
1. Classic switching fabric with optical Delay Line (FDL) at input
As shown in fig. 3, this architecture is a classical switching architecture, which consists of two parts, scheduling and switching. Wherein the scheduling part mainly resolves scheduling and conflict resolution of the BHP, and the switching part switches the input burst data to a designated output port. This switching fabric has a head-of-line blocking problem, since two bursts cannot be output from the output of the same FDL at the same time, i.e. on each incoming wavelength channel, the preceding burst will block the following burst. For example, assuming that each burst is of duration T, if two sequential bursts of the input wavelength channel i are to be sent from the output wavelength channel j and the output wavelength channel k, respectively. If the first burst data needs a delay time T, the second burst data must also be delayed for a time longer than T, otherwise, two burst data are output from the same buffer wavelength channel at time T, resulting in a collision. However, if the first burst needs to be delayed by nT (n > 1), then the second burst can be sent without delay as long as there is no collision on port k. The FDL's ability to resolve conflicts can be greatly affected due to head-of-line blocking, and the improvement in loss performance will be limited. Meanwhile, in such a structure, FDL resources cannot be shared, resulting in high cost.
2. Broadcast-selective switching fabric
As shown in fig. 4, the structure comprises three parts of wavelength encoding, buffering and wavelength selection, and can perform switching of N-wavelength input and N-wavelength output K time slots under certain conditions. This configuration requires that only one wavelength signal be output at each output at the same time. In the encoding section, each input wavelength is converted into a signal having no same wavelength by N Fixed Wavelength Converters (FWC), and then combined together and fed to the buffer section. The signal from the wavelength coding part is copied to each time slot by splitter and FDL in the buffer part, and then a space division switching structure is constructed by splitter, optical switch and multiplexer to switch the signal to the output terminal. Finally, the wavelength selection part selects the signal with a certain wavelength at each output end at a certain moment by utilizing the demultiplexer, the optical switch and the multiplexer, thereby achieving the purpose of optical switching. The wavelength at the output is variable because the wavelength is selected at the output.
The structure has the advantages of simple principle and easy realization of a control algorithm. But because of broadcasting, each channel is filled with information which is not needed by the channel, so the resource utilization rate is low; and multiplexing, photoswitch and demultiplexing equipment of each output end cannot be shared, and the required devices are more and have high cost. And the optical signal is divided into N parts after passing through the decomposer, the energy of the optical signal is greatly reduced, and the probability of signal error codes is increased.
3. Shared transformation pool architecture
As shown in fig. 5, this structure consists of a 2N × 2N switching matrix, N TWCs for tuning data to a desired output wavelength, and N ODLs. And the N internal circulation wavelength channels can enable the low-priority data to be sent into the ODL for delaying again when the high-priority data and the low-priority data conflict, thereby realizing the support of the priority. This switching fabric requires more resources; half of the wavelength can not be output, the wavelength utilization efficiency is not high, and the cost of the AWG is too high due to excessive wavelength; although priority can be given with re-delaying, the priority effect provided is limited due to the limited number of times the optical signal is delayed for attenuation reasons.
From the above description, it is known that the following problems mainly exist in the current optical burst switching research:
1) the optical burst switching provides a Best effort Services (Best effort Services), and the lower theoretical limit of the loss rate is the full busy probability calculated by the Ireland formula. The loss rate is too high for packet switching in the electrical domain.
2) FDLs cannot provide random access, can only provide a fixed time delay, are bulky, and have optical power loss. And the series design and the depth design are complex, and more factors need to be considered. The ability to cache data and resolve conflicts is limited.
Disclosure of Invention
The invention aims to provide an optical-electrical hybrid switching structure supporting optical burst/packet switching for a core node in an optical burst/packet switching network.
For convenience of description, the following definitions are given:
edge nodes: the nodes located at the edge of the OBS network mainly realize the generation of burst data and the photoelectric conversion in function.
A core node: the non-edge node in the optical burst switching network realizes the optical switching of the optical burst data.
Exchanging: and sending out the burst data sent in from the specific wavelength channel of the specific input port at the specific time from the specific wavelength channel of the specific output port at the specific time.
Loss rate: the loss rate of packets in the network.
Conflict: when multiple burst packets are simultaneously destined for a particular wavelength channel on the same output port, a "collision," also referred to as "external blocking" in the packet switch, occurs.
Time delay: the time difference between the transmission of burst data to and from a device.
Transmission errors: burst data is transmitted from a source end to a destination end through an OBS network, but due to errors introduced in the transmission process, data sent by the source end and data received by the destination end are inconsistent, and this is referred to as a transmission error.
The invention provides an optical-electrical hybrid switching structure (as shown in fig. 6) supporting optical burst/packet switching, comprising: an optical switching matrix, said optical switching matrix has (M + N × N) input ports and (M + N × N) output ports, M represents the number of buffer channels, N represents the number of input ports or output ports, N × N represents the number of input (output) wavelength channels, and N represents the number of wavelength channels included in each input port or output port; n input ports, N output ports, N wave splitters, N wave combiners and Nxn adjustable wavelength converters (TWC); the input port 1 decomposes n wavelength channels through a wave splitter, and the n wavelength channels are respectively connected to any n input ports of the optical switching matrix by using optical fibers; the input port 2 decomposes n wavelength channels through a wave splitter, and the n wavelength channels are respectively connected to any n input ports of the optical switching matrix by using optical fibers; the rest input ports are analogized in this way to form N input ports; all the input ports share N multiplied by N input ports of the optical switching matrix; corresponding to the input port 1, n wavelength channels output from n output ports of the optical switching matrix are connected to n adjustable wavelength converters through optical fibers, and each adjustable wavelength converter is connected to the combiner through the optical fibers to form an output port 1; corresponding to the input port 2, n wavelength channels output from n output ports of the optical switching matrix are connected to n adjustable wavelength converters through optical fibers, and each adjustable wavelength converter is connected to the combiner through the optical fibers to form an output port 2; the rest output ports are analogized in this way to form N output ports; all output ports share N multiplied by N output ports of the optical switching matrix;
it is characterized in that it also comprises:
the photoelectric converter, the RAM buffer and the photoelectric converter are connected in sequence through an electric domain to form a buffer channel, and M buffer channels are shared; the input end of each buffer channel is connected with the output port of the optical switching matrix through an optical fiber, and the output end of each buffer channel is connected with the input port of the optical switching matrix through an optical fiber.
It should be noted that, in the following description,
the input ports and the output ports of the optical switching matrix described above can be connected to only one channel.
The branching filter is used for decomposing an input multi-wavelength composite optical signal into a plurality of single-wavelength optical signals and outputting the single-wavelength optical signals, wherein each single-wavelength optical signal corresponds to different wavelengths.
The optical switching matrix is used for switching an optical signal input by a certain input port of the optical switching matrix in a specified time period to a specified output port of the optical switching matrix for output.
The photoelectric converter is used for converting an input optical signal with any wavelength into an electric signal through photoelectric conversion and outputting the electric signal;
the RAM buffer is used for storing the input electric signal for a certain time and then outputting the electric signal; the function of the electro-optical converter is to convert the electric signal buffered by the RAM into an optical signal with a certain wavelength.
The function of the tunable wavelength converter is to convert an input optical signal with an arbitrary wavelength into an optical signal output with a specified output wavelength.
The combiner is used for combining a plurality of input single-wavelength optical signals into one multi-wavelength optical signal and outputting the multi-wavelength optical signal, and each input single-wavelength optical signal corresponds to different wavelengths.
The working process of the invention is as follows:
the multi-wavelength composite optical signal containing a plurality of burst data enters an input port of the switching structure of the invention through an optical fiber, is decomposed into single-wavelength optical signals with different wavelengths (each wavelength has one burst data to be transmitted at the same time) after passing through a wave splitter, and is connected to an input port of an optical switching matrix through the optical fiber. And after the burst data arrives at the optical switching matrix, switching the burst data to a specific output port of the optical switching matrix for output according to the processing result of the corresponding previously received burst control packet. If no conflict exists, switching to a certain output port of the optical switching matrix corresponding to the output port of the switching structure; if conflict occurs, the optical switch matrix is switched to a certain output port corresponding to the cache channel. And sending the burst data with conflict into a buffer channel through an optical fiber for delaying after the burst data with conflict is output from an output port of the optical switching matrix so as to solve the conflict. The burst data enters the photoelectric converter to be converted into an electric signal, then is sent into the RAM buffer for time delay through electric connection, then is taken out from the RAM buffer and is sent to the photoelectric converter through the electric connection to be converted into an optical signal, and finally is sent back to the input port of the optical switching matrix from the photoelectric converter through the optical fiber. And the optical burst data after being delayed by the buffer channel is switched to an output port again without conflict according to the processing result of the corresponding burst control packet for output. For the burst data without conflict and the burst data with conflict resolved through the buffer channel, the burst data is converted to the appointed wavelength through the adjustable wavelength converter after being output from the optical switching matrix. The plurality of bursts converted to the specified wavelengths (the wavelengths used by the converted bursts are different) are connected to a combiner through optical fibers, and are processed and combined by the combiner into a multi-wavelength composite optical signal containing the plurality of bursts, and the multi-wavelength composite optical signal is sent to an output port for output.
The invention has the innovation that:
the main idea of the switching structure proposed by the present invention is to use optical switching as the main, and to use a buffer channel composed of a photoelectric converter, a RAM buffer, and an electro-optical converter connected in turn via an electrical domain, to replace the optical buffer FDL with an electrical domain buffer, and to properly assist with the electrical domain switching. Compared with the optical buffer FDL, the method has the characteristics of effectively reducing the loss rate of the network, reducing the error/lost retransmission time delay, effectively supporting multiple priorities and the like.
The optical-electrical hybrid switching structure supporting optical burst/packet switching provided by the invention has the advantages that:
1) the loss rate of the network is reduced, and the network performance is improved. The most significant cause of data loss in optical networks is collisions. The exchange structure can effectively solve conflict by using electric domain buffer memory, and the conflict solving ability is greatly superior to the conflict solving scheme of optical domain. Referring to fig. 7, ti1 represents the original arrival time of the ith burst, ti2 represents the original departure time of the ith burst, ti1 'represents the arrival time of the ith burst after passing through the buffer, and ti 2' represents the departure time of the ith burst after passing through the buffer. As shown, three bursts of BHP arrive in sequence, which give the expected arrival times t11, t21, t31 and departure times t12, t22, t32 of the corresponding bursts. It can be seen from the figure that when burst data 3 arrives, burst data 1 is being transmitted, and burst data 3 must be buffered and delayed before being transmitted to resolve the collision. If FDL is used to resolve the collision, the time of the delay must be an integer multiple of the fixed time (set to T). This makes it possible to prevent data from being transmitted in a gap due to a delay of a fixed time even if there is a gap in which data can be transmitted. It can be seen in the figure that the transmission of burst data 3 after delay T through the optical delay line collides with burst data 2, even though the time gap between burst data 1 and burst data 2 can transmit burst data 3. It can be seen from the diagram that the burst data 3 must be transmitted without collision after a delay of 4T, which increases the transmission time of the burst data from the source to the destination, and the attenuation of the optical signal after the 4T delay increases, which is more likely to introduce errors. These problems can be avoided if we use the optical cache structure proposed by this patent. As shown in the figure, the burst data 3 arrives at t31 and collides with the burst data 1, and is subjected to photoelectric conversion and buffered in the electric domain RAM, and after the delay of Δ t (Δ t ═ t 31' -t31), the photoelectric conversion is performed again, and the data is sent back to the optical domain for transmission. Since the delay of the electric domain RAM is arbitrary, the gap between the burst data 1 and the burst data 2 can be used to transmit the burst data 3 after the delay Δ T smaller than T. Because Δ T < 4T, the transmission time from source to destination is greatly shortened; and the electro-optically converted optical signal is a regenerated optical signal without the problem of weakening due to time delay, which also reduces the probability of transmission errors.
2) The delay of error/lost retransmission is reduced, and the network load caused by retransmission is reduced, so that the effective bandwidth is increased to a certain extent. The OBS provides only best effort service, that is, it does not guarantee the quality of service, so the handling of collision packet loss and transmission errors is done by upper layer protocols. When conflict packet loss occurs, the upper layer protocol can only adopt a retransmission mode to solve; and for transmission errors, the upper layer protocol can correct through an efficient coding scheme or require source-side retransmission. An efficient coding scheme can indeed correct certain errors, but the redundancy for error correction is too costly when there are more errors and rather not as efficient as retransmission. It can be seen that this manner of retransmission is an important means for providing reliable transmission, but retransmission can load the network and reduce the effective transmission performance of the network. From the analysis of 1), it can be seen that the switching fabric proposed by the present patent can reduce the loss rate and reduce the probability of transmission errors. This reduces the probability of retransmission, i.e. indirectly reduces the load on the network, increasing the effective bandwidth.
3) Different priorities can be flexibly and conveniently provided for different services. Currently, there are few methods for providing QoS in optical burst switching, and most of the methods are based on offset time or burst aggregation. The offset time based approach introduces a large delay and can be prioritized only with limited priority. The method based on the burst convergence is realized at the edge node, and is not helpful to the provision of the core network QoS. Other approaches, such as providing limited buffering with FDLs, also provide limited and inflexible QoS due to the deficiencies of FDLs themselves. In the switching structure provided by the patent, the technology of electric domain maturity can be utilized to easily obtain almost unlimited storage time and storage capacity, and meanwhile, random access can be realized. Therefore, the transmission time slots meeting the priority requirements of the services with different priorities can be allocated, namely, the services can obtain almost the same priority support as the pure electric field transmission network.
4) Wavelength-granularity switching can be supported to some extent. In current switching fabrics, the rate of loss of bursty data is already much higher than in packet switching in the electrical domain, which introduces higher loss rates when longer circuit switching (i.e., wavelength switching) is required. In the present structure, some wavelength channels in the ports can be used to provide certain wavelength switching while ensuring the burst loss rate is stable.
In summary, the switching structure provided by the present invention can effectively reduce the loss rate of the network, reduce the delay of error/lost retransmission, effectively support multiple priorities, provide switching of wavelength granularity, and is a switching structure with good performance.
Drawings
FIG. 1 is a schematic diagram of a conventional OBS network structure
FIG. 2 is a schematic diagram of a core node structure
Where IDC represents an input data channel, ODC represents an output data channel, ICC represents an input control channel, OCC represents an output control channel, FDL represents a fiber delay line, and BCP represents a burst control packet.
FIG. 3 is a schematic diagram of an input buffer type switching fabric
Wherein,
a tunable wavelength converter is shown that is,
representing an optical delay line.
FIG. 4 is a schematic diagram of a broadcast selective switch fabric
Wherein K represents the maximum delay section number of the optical delay line; n represents the number of incoming wavelength channels of the switch fabric; the function of the decomposer is to duplicate one signal into a plurality of identical signals; the combiner is used for combining a plurality of channels into one channel; the optical switch functions to allow or prohibit the passage of an optical signal.It is meant a fixed wavelength converter that,which is representative of an optical delay line,a resolver is shown which is,which is indicative of an optical switch, is shown,a combiner is represented.
FIG. 5 is a schematic diagram of a shared transform pool structure
Wherein N represents the number of input wavelength channels of the switch fabric; p represents the number of optical buffer channels; wherein,a tunable wavelength converter is shown that is,representing an optical delay line.
Fig. 6 shows a burst switching scheme with reduced loss according to the invention in which the connection is split into multiple sub-connections
FIG. 7 electric domain conflict resolution diagram
Wherein, T represents unit fixed time delay of an optical delay line (FDL); ti1 denotes the original arrival time of the ith burst; ti2 denotes the original departure time of the ith burst; ti 1' represents the arrival time of the ith burst after passing through the buffer; ti 2' represents the departure time of the ith burst after it passes through the buffer; Δ t (t 31' -t31) represents the minimum electrical domain delay for collision-free transmission of burst data.
Fig. 8 is a schematic diagram of an embodiment of 100% non-packet loss after collision
Fig. 9 is a schematic diagram of an embodiment of no packet loss after collision
Detailed Description
Embodiment one, embodiment of 100% no packet loss after collision
Referring to fig. 8, we use a 32 x 32 optical switch matrix without internal blocking; the input end is provided with two input ports with 8 wavelength channels respectively, and 16 input wavelength channels are used as the input of signals; the output end is also provided with two output ports with 8 wavelength channels respectively, the 16 output wavelength channels are used as the output of signals, and the difference from the input end is that 16 wavelength converters can adjust the output signals to the required wavelength; the remaining 16 wavelength channels and 16 photoelectric converters at the input end and the output end, 16 RAM buffers and 16 photoelectric converters form a buffer part together to provide 16 buffer channels for solving the conflict.
When the node starts to operate, the cache section stores no data, and all data is input from 16 input wavelength channels. The worst case scenario for collisions at this time is that 16 wavelength channels each have a burst of data to transmit at the same time and all 16 data need to be sent on the same output wavelength channel. The solution to the collision in this case is to send one of the 16 data out of the wavelength channel that it needs to output, and to send the remaining 15 bursts into 15 different cache channels, and then to select the appropriate time for sending without collision. So 16 input-output wavelength channels and 16 buffer channels can ensure that no packet is lost after 100% of collisions during initial operation. But this is not yet the worst case scenario for collisions, which is 32 bursts of data simultaneously needed to be transmitted on the 16 input wavelength channels and 16 cache channels at the ingress end of the switch matrix. From the introduction to optical burst switching systems, we know that we have handled their respective BHPs before the burst data arrives, i.e. we know the collision situation in advance. Therefore, the burst data sent by the 16 cache channels do not collide with each other, that is, the burst data sent by the 16 cache channels are respectively sent to the 16 output wavelength channels, that is, the 16 output wavelength channels all have burst data to be sent. Then collisions are only possible between bursts fed in by the 16 incoming wavelength channels and between bursts fed in by the incoming wavelength channels and bursts fed in by the cache. From each output wavelength channel, when n burst data are in conflict, one of the n burst data is selected to be sent out, and the rest n-1 burst data are sent into a buffer to delay and solve the conflict. So in the case of 16 output wavelength channels all having data, 16 bursts are sent out by the output wavelength channels, and 32-16 bursts are respectively sent into 16 buffer channels for delay. Thus, in the worst case, we can provide 100% of the collision without losing packets. Certainly, the problem to be considered is that the capacity of the buffer cannot be infinite, so that all burst data sent after collision can be loaded; the upper layer protocol has a limit on the buffering time, and if the upper layer protocol has a limit on the whole transmission time of the data, the buffering time is too long, so that the upper layer protocol can consider the packet to be lost and retransmit the packet. In summary, in an ideal situation, if the number M of cache channels is equal to the total number N × N of input/output wavelength channels, the switch fabric proposed in this patent can provide 100% of protection against packet loss after collision.
Embodiment two, embodiment with a certain loss rate after collision
The configuration of fig. 9 also achieves a better cost performance if a certain degree of data loss rate is allowed in practical applications. As shown, a 32 × 32 non-blocking optical switching matrix is still used; the input end is provided with three input ports with 8 wavelength channels respectively, and 24 input wavelength channels are used as the input of signals; the output end is provided with three output ports with 8 wavelength channels respectively, 24 output wavelength channels are used as the output of signals, and 24 wavelength converters can adjust the output signals to the required wavelength; the remaining 8 wavelength channels and 8 photoelectric converters at the input end and the output end, 8 RAM buffers and 8 photoelectric converters form an electric buffer part together to provide 8 electric buffer channels for solving the conflict. The increased 8 input/output wavelength channels can increase the input/output capacity and support more services to pass through. The probability of a worst collision scenario is very small and 8 cache channels can provide better support for collisions. That is, a larger traffic transmission capability is achieved by sacrificing a little data loss rate without changing the size of the switching matrix. This configuration both controls cost and guarantees loss performance because the high speed optical switching matrix increases cost significantly with the increase in ports.
Claims (3)
1. An opto-electronic hybrid switching fabric supporting optical burst/packet switching, comprising: an optical switching matrix, said optical switching matrix has (M + N × N) input ports and (M + N × N) output ports, M represents the number of buffer channels, N represents the number of input ports or output ports, N × N represents the number of input (output) wavelength channels, and N represents the number of wavelength channels included in each input port or output port; n input ports, N output ports, N wave splitters, N wave combiners and Nxn adjustable wavelength converters (TWC); the input port (1) decomposes n wavelength channels through a wave splitter, and the n wavelength channels are respectively connected to any n input ports of the optical switching matrix by using optical fibers; the input port (2) decomposes n wavelength channels through a wave splitter, and the n wavelength channels are respectively connected to any n input ports of the optical switching matrix by using optical fibers; the rest input ports are analogized in this way to form N input ports; all the input ports share N multiplied by N input ports of the optical switching matrix; corresponding to the input port (1), n wavelength channels output from n output ports of the optical switching matrix are connected to n adjustable wavelength converters through optical fibers, and each adjustable wavelength converter is connected to the combiner through the optical fibers to form the output port (1); corresponding to the input port (2), n wavelength channels output from n output ports of the optical switching matrix are connected to n adjustable wavelength converters through optical fibers, and each adjustable wavelength converter is connected to the combiner through the optical fibers to form the output port (2); the rest output ports are analogized in this way to form N output ports; all output ports share N multiplied by N output ports of the optical switching matrix;
it is characterized in that it also comprises:
the photoelectric converter, the RAM buffer and the photoelectric converter are connected in sequence through an electric domain to form a buffer channel, and M buffer channels are shared; the input end of each buffer channel is connected with the output port of the optical switching matrix through an optical fiber, and the output end of each buffer channel is connected with the input port of the optical switching matrix through an optical fiber.
2. An optical-electrical hybrid switching fabric supporting optical burst/packet switching as claimed in claim 1, wherein each input port of said optical switching matrix is connectable to only one channel.
3. An optical-electrical hybrid switching fabric supporting optical burst/packet switching as claimed in claim 1 wherein each output port of said optical switching matrix is connectable to only one channel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2004100401111A CN1717113A (en) | 2004-07-02 | 2004-07-02 | Photoelectric mixed exchanging struture supporting light burst/group exchanging |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2004100401111A CN1717113A (en) | 2004-07-02 | 2004-07-02 | Photoelectric mixed exchanging struture supporting light burst/group exchanging |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN1717113A true CN1717113A (en) | 2006-01-04 |
Family
ID=35822455
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNA2004100401111A Pending CN1717113A (en) | 2004-07-02 | 2004-07-02 | Photoelectric mixed exchanging struture supporting light burst/group exchanging |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN1717113A (en) |
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2008077322A1 (en) * | 2006-12-26 | 2008-07-03 | Huawei Technologies Co., Ltd. | A network node and a buffer device and a scheduling method |
| CN1996799B (en) * | 2006-11-30 | 2010-04-14 | 上海交通大学 | Optical packet access method based on the optical and electrical mixed cache structure |
| CN101924961A (en) * | 2010-07-19 | 2010-12-22 | 浙江工业大学 | The multiple size light cross connection device that is used for core nodes of optical burst switching network |
| CN101370312B (en) * | 2007-08-17 | 2010-12-29 | 电子科技大学 | Construction method for hybrid switching optical network based on loop circuit |
| CN101426152B (en) * | 2008-12-08 | 2011-03-16 | 电子科技大学 | Data transmission method for integrated mixed optical network based on burst exchange |
| CN101621719B (en) * | 2009-07-29 | 2012-04-25 | 电子科技大学 | Switch processor matched with core node of hybrid optical switching network |
| CN101656900B (en) * | 2009-09-11 | 2012-09-26 | 重庆邮电大学 | OPS node optical buffering device and method based on load selection |
| CN101778047B (en) * | 2010-02-09 | 2013-01-23 | 重庆邮电大学 | Method for resolving optical switching grouping competition and photoelectric hybrid cache device |
| CN102118305B (en) * | 2010-01-06 | 2014-04-30 | 上海贝尔股份有限公司 | Service board of communication equipment and communication equipment employing same |
| WO2015109606A1 (en) * | 2014-01-27 | 2015-07-30 | 华为技术有限公司 | Data exchange device and system |
| CN105515993A (en) * | 2015-11-26 | 2016-04-20 | 西安空间无线电技术研究所 | Photoelectric hybrid exchange internal path mapping method |
| CN103873833B (en) * | 2012-12-10 | 2017-06-20 | 常州华龙通信科技有限公司 | Digital video light exchanges transmission platform |
| CN107333190A (en) * | 2017-06-01 | 2017-11-07 | 清华大学 | A kind of photoelectricity hybrid switching structure of variable granularity |
-
2004
- 2004-07-02 CN CNA2004100401111A patent/CN1717113A/en active Pending
Cited By (19)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1996799B (en) * | 2006-11-30 | 2010-04-14 | 上海交通大学 | Optical packet access method based on the optical and electrical mixed cache structure |
| US8249449B2 (en) | 2006-12-26 | 2012-08-21 | Huawei Technologies Co., Ltd. | Network node, buffer device, and scheduling method |
| CN101212818B (en) * | 2006-12-26 | 2010-12-08 | 华为技术有限公司 | Network node and buffer device, and scheduling method |
| WO2008077322A1 (en) * | 2006-12-26 | 2008-07-03 | Huawei Technologies Co., Ltd. | A network node and a buffer device and a scheduling method |
| CN101370312B (en) * | 2007-08-17 | 2010-12-29 | 电子科技大学 | Construction method for hybrid switching optical network based on loop circuit |
| CN101426152B (en) * | 2008-12-08 | 2011-03-16 | 电子科技大学 | Data transmission method for integrated mixed optical network based on burst exchange |
| CN101621719B (en) * | 2009-07-29 | 2012-04-25 | 电子科技大学 | Switch processor matched with core node of hybrid optical switching network |
| CN101656900B (en) * | 2009-09-11 | 2012-09-26 | 重庆邮电大学 | OPS node optical buffering device and method based on load selection |
| CN102118305B (en) * | 2010-01-06 | 2014-04-30 | 上海贝尔股份有限公司 | Service board of communication equipment and communication equipment employing same |
| CN101778047B (en) * | 2010-02-09 | 2013-01-23 | 重庆邮电大学 | Method for resolving optical switching grouping competition and photoelectric hybrid cache device |
| CN101924961A (en) * | 2010-07-19 | 2010-12-22 | 浙江工业大学 | The multiple size light cross connection device that is used for core nodes of optical burst switching network |
| CN101924961B (en) * | 2010-07-19 | 2013-04-17 | 浙江工业大学 | Multi-granular optical cross connection device for core nodes in optical burst switching network |
| CN103873833B (en) * | 2012-12-10 | 2017-06-20 | 常州华龙通信科技有限公司 | Digital video light exchanges transmission platform |
| WO2015109606A1 (en) * | 2014-01-27 | 2015-07-30 | 华为技术有限公司 | Data exchange device and system |
| US9806909B2 (en) | 2014-01-27 | 2017-10-31 | Huawei Technologies Co., Ltd. | Data switching apparatus and system |
| CN105515993A (en) * | 2015-11-26 | 2016-04-20 | 西安空间无线电技术研究所 | Photoelectric hybrid exchange internal path mapping method |
| CN105515993B (en) * | 2015-11-26 | 2019-02-15 | 西安空间无线电技术研究所 | A kind of photoelectricity hybrid switching inner track mapping method |
| CN107333190A (en) * | 2017-06-01 | 2017-11-07 | 清华大学 | A kind of photoelectricity hybrid switching structure of variable granularity |
| CN107333190B (en) * | 2017-06-01 | 2020-04-28 | 清华大学 | Photoelectric mixed exchange structure with variable granularity |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Kim et al. | Contention resolution for optical burst switching networks using alternative routing | |
| US6466343B1 (en) | System for assigning wavelengths in a wave division multiplexing based optical switch | |
| US8249449B2 (en) | Network node, buffer device, and scheduling method | |
| Iizuka et al. | A scheduling algorithm minimizing voids generated by arriving bursts in optical burst switched WDM network | |
| CN1717113A (en) | Photoelectric mixed exchanging struture supporting light burst/group exchanging | |
| Xue et al. | High-capacity multiservice optical label switching for the next-generation Internet | |
| US7499650B2 (en) | Optical burst switching node with internal speedup | |
| KR100715520B1 (en) | Apparatus for transportation optical data in optical switching system and method thereof | |
| US7734176B2 (en) | Hybrid optical burst switching with fixed time slot architecture | |
| CN1275413C (en) | Burst counting and multiplexing method for avoiding optical signal conflict in optical network | |
| CN1316799C (en) | Method for supporting real-time service in optical burst exchange | |
| Agustí-Torra et al. | Retransmission schemes for optical burst switching over star networks | |
| KR100751447B1 (en) | Optical piggyback switching method based on wavelength division multiplexing and switching node structure | |
| Samoud et al. | Performance improvements of hybrid opto-electronic packet switch using SDM in addition to WDM | |
| US20020154361A1 (en) | Wavelength division multiplexed (WDM) network element and a method for propagating data packets across the network element | |
| Orphanoudakis et al. | A hybrid optical switch architecture with shared electronic buffers | |
| Li et al. | A CSMA/CP MAC protocols for IP over WDM metropolitan area ring networks | |
| Qiu | Performance analysis of a selective burst discarding scheme for deflection routing in OBS networks | |
| CN1716903A (en) | Light burst/grouping switching structure without team head block | |
| Samoud et al. | Performance analysis of a hybrid opto-electronic packet switch using WDM technology | |
| KR0150525B1 (en) | Output recontending space/code mixed type optical switching system | |
| Thompson | Photonic Switch | |
| Binh et al. | Improved WDM packet switch architectures with output channel grouping | |
| Reza et al. | Performance of two-stage shared fiber delay line optical packet switch under bursty traffic | |
| Hirota et al. | Multicast design method using multiple shared-trees in optical WDM networks |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C02 | Deemed withdrawal of patent application after publication (patent law 2001) | ||
| WD01 | Invention patent application deemed withdrawn after publication |