JP4017506B2 - Node equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a node device that realizes virtual ring optical burst transfer that performs optical burst transfer in an optical path cross-connect (OXC) network.
[0002]
[Prior art]
Broadband Internet broadband has been accelerated by the fusion of broadband optical transmission technology and Internet technology. With the recent Internet, the distribution of video content has been added to the Internet service provider's service menu, and the volume of content that has been distributed has increased, and the distribution of video content in the hundreds of megabytes to gigabytes has come into view. Yes.
[0003]
By the way, despite the development of such a large-capacity information distribution service, the technical infrastructure for large-capacity content distribution is TCP / IP technology. The advantage of TCP / IP is that narrowband services such as mail, small-volume file transfer, and still image web, and broadband services such as large-capacity content distribution can be accommodated in the same network platform.
[0004]
However, TCP / IP technology is a technology that emphasizes compatibility with Ethernet (registered trademark) technology widely used in local area networks (LAN), and the information to be transferred is a gigabyte-class large-capacity content. However, at present, it is not allowed to transfer information using jumbo packets exceeding 64 kbytes. In addition, even when constructing a backbone network, a method in which real-time transfer such as voice call and gigabyte-class large-capacity content transfer are mixed by packet multiplexing is not desirable. In order to ensure the real-time property of the voice packet, it is necessary to divide the large-capacity content packet into a plurality of short packets. As a result, when transferring large-capacity content, a large amount of overhead information must be added to the IP header, increasing transmission band loss.
[0005]
As means for solving the above problems, it is considered to use an optical networking technology based on an optical path cross-connect (OXC) device. In the optical network, an optical signal can be transmitted in an independent protocol format for each wavelength channel. In each fiber link, a certain wavelength channel accommodates an optical path # 1 connecting IP routers # A- # B and provides a conventional IP transfer service. On the other hand, another wavelength channel contains the optical burst signal.
[0006]
As shown in FIG. 6, the optical burst signal is a signal that occupies a wavelength channel having an ultrahigh-speed transmission capability of 10 Gbit / s or more for a predetermined short time, and when delivering a gigabyte-class large-capacity content, The hold time τ occupies a wavelength channel of 10 Gbit / s around 1 second. This transfer method enables instantaneous batch transfer of moving image content files, for example, for about 2 hours.
[0007]
By the way, the difficulty of optical burst transfer lies in the collision avoidance method for content traffic transferred in bursts. If there is contention for multiple optical burst traffic competing for the same wavelength channel within the transport network, the optical burst traffic that cannot be accommodated in the wavelength channel is accommodated in another wavelength channel, or the buffer inside the node Need to be temporarily evacuated. A system that includes a buffer that temporarily saves gigabyte-class content transferred by an ultrahigh-speed signal of 10 Gbit / s or more at each relay node increases the node implementation scale. To construct an economical optical burst transport network, it is necessary to realize an effective collision avoidance method for optical burst traffic.
[0008]
One of optical burst transfer methods that alleviates such a collision avoidance problem is an optical bar string transfer method (Non-Patent Document 1). This method is a method of transferring optical signals in bursts between nodes while sharing the wavelength band of a single wavelength channel in which multiple nodes are connected in a ring topology. This is done at the input node. That is, as shown in FIG. 7, the bandwidth is secured by the upstream node priority algorithm, and the downstream node (# 3) secures the transmission bandwidth (time slot 1) that was not used by the upstream node (# 1). is there. This system enables instantaneous batch transfer of large-capacity contents, and at the same time, makes it possible to effectively use a limited wavelength band due to the statistical multiplexing effect.
[0009]
[Non-Patent Document 1]
Park, Takada, Imajuku, Yamabayashi, “Examination of ultra-high speed ring network using optical label switch”, PNI2000-10, May 2000
[0010]
[Problems to be solved by the invention]
The advantage of the ring topology is that it is easy to control the optical burst signal and that it is easy to ensure fairness among the nodes. As shown in FIG. 7, the numbers of upstream nodes and downstream nodes as seen from each node are all the same. In such a network, when an optical burst signal is transferred while securing the entire bandwidth of the wavelength channel in the multiplexing unit slot defined in a certain time, the upstream node has the priority to secure the multiplexing unit slot. Even if the traffic control is performed using a simple control algorithm such as the above, the fairness of the multiplexing unit slots that can be secured by each node is easily maintained. For example, the fairness of time slots reserved at each node can be achieved by a simple algorithm such as setting an upper limit for multiplexing unit slots that can be reserved at each node.
[0011]
It is an object of the present invention to provide a node device that realizes virtual ring optical burst transfer in an OXC mesh network with avoidance of optical burst signal collision and minimum guarantee of optical burst transfer bandwidth.
[0012]
[Means for Solving the Problems]
The virtual ring optical burst transfer method realized by the node device according to the present invention includes a plurality of nodes constituting an optical path cross-connect network as a group unit in an optical path cross-connect network that performs optical burst transfer. A single virtual ring network is defined by a collection of optical channels that connect each node constituting a ring in a ring shape, and the transmission band of the virtual ring network is shared by each node constituting the group. When it occurs, the transmission band of the virtual ring network is secured and transferred as an optical burst signal.
[0013]
The nodes constituting this virtual ring network are interconnected by wavelength multiplexing links, and the node device of the present invention for transferring optical burst signals by the virtual ring optical burst transfer method is wavelength multiplexed from the wavelength multiplexing link on the input side. Wavelength demultiplexer that inputs and demultiplexes optical signals, optical switch function unit that outputs optical signals of each wavelength to specified paths, and wavelength multiplexing that multiplexes optical signals output to each path A virtual ring network transmission band by referring to an optical switch unit provided with a device, a virtual ring identification information accommodating the own node, and a database holding an input wavelength channel number and an output wavelength channel number accommodating the virtual ring network. And a burst switch control unit that controls the optical switch function unit.
[0014]
The optical switch function unit includes a wavelength conversion function for converting each input optical signal into a predetermined wavelength. The burst switch control unit sets the output wavelength channel number registered in the database as a priority wavelength channel number. It searches whether this priority wavelength channel number is unused at the arrival time of the optical burst signal, uses the output wavelength channel if it is not used, and searches for another available output wavelength channel if it is in use. Thus, the control is performed to secure the transmission band of the virtual ring network.
[0015]
The burst switch control unit also includes a schedule table for managing the scheduled time for setting the optical switch, the input wavelength channel number and the output wavelength channel number, and a clock for defining the time, and matches the arrival time of the optical burst signal. Thus, the transmission band of the virtual ring network is secured.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment of Virtual Ring Optical Burst Transfer Method)
FIG. 1 shows a configuration example of an optical cross-connect network for explaining a virtual ring optical burst transfer method of the present invention.
[0017]
The present embodiment is an optical path network that defines optical paths in wavelength units, and an optical cross-connect network that realizes a cross-connection of these optical paths. This optical cross-connect network realizes two types of networking. The first networking is a form in which a point-to-point path is defined between a start node and an end node. In the second networking, some nodes in the optical cross-connect network are defined as one group unit. In addition, an optical channel for connecting each node that is a member of the group is defined between the optical path cross-connect devices, and a virtual ring network is configured by an assembly of these optical channels. In order to realize this networking, each node is equipped with a wavelength conversion function as means for avoiding collision between optical paths. Each optical path band is 10 Gbit / s and is transferred in the OTN format of the ITU-T G.709 specification. This optical path is accommodated in the fiber link at intervals of 50 GHz, and wavelength division multiplexing transmission of 32 wavelengths is realized in each fiber link.
[0018]
A feature of this embodiment is that a function for realizing the second networking is implemented in each node. Each node has a function of defining and managing each virtual ring network by assigning an identification number thereto.
[0019]
In the example shown in FIG. 1, nodes # 1, # 2, # 4, and # 6 are group units, and one virtual ring network 101 is defined by an aggregate of optical channels that connect between nodes constituting the group. This is assigned an identification number and managed by each node. This virtual ring network 101 includes, for example, # 1- # 2: wavelength channel λ4
# 2- # 4: Wavelength channel λ3 (# 2- # 3), Wavelength channel λ2 (# 3- # 4)
# 4- # 6: Wavelength channel λ2
# 6- # 1: Wavelength channel λ1
In this form, a wavelength channel, which is a means for connecting these nodes in a ring shape, is secured between the nodes. Here, a single wavelength channel is secured between the nodes, but two or more wavelength channels may be secured.
[0020]
Nodes # 2 and # 4 are connected via node # 3 by using two wavelength channels. A wavelength channel of λ3 is used between # 2 and # 3, and a wavelength channel of λ2 is used between # 3 and # 4, and two wavelength channels are connected using the wavelength conversion function of node # 3. However, since the node # 3 is not a node constituting the virtual ring network 101, it provides only a function for forwarding traffic of the ring network.
[0021]
Each node shares the bandwidth of the virtual ring network 101 configured in this manner. FIG. 2 shows an example of bandwidth sharing of the virtual ring network 101. Nodes # 1, # 2, # 3, and # 4 transfer communication traffic generated between these nodes in a burst manner. Here, it is assumed that the upstream node is given priority to transfer a 10 Gbit / s optical burst signal. At this time, the node # 2 waits to send new traffic from the node # 2 to the ring at the moment when traffic from the node # 1 to the node # 4 arrives. The node # 2 transfers the optical burst signal from the node # 2 to the node # 4 by catching the timing when the traffic has passed. By such processing, large-capacity content traffic generated in a burst manner is accommodated in one virtual ring network by the statistical multiplexing method.
[0022]
Two methods can be mainly applied as a method for identifying the transfer destination information of the optical burst signal by each node. The first is a method of adding destination label information to the optical burst signal itself. The method of adding destination label information to an optical burst signal is as follows: (1) A method of adding destination label information to the head of an optical burst signal to be transferred, based on the same concept as in the prior art, and (2) Destination label of an optical burst signal. There is a method of superimposing a modulation signal carrying information. As the modulation signal, a subcarrier modulation signal, an optical code division multiplexing signal, or the like can be used.
[0023]
The second method uses a control line different from the main signal line for transferring the optical burst signal. Shortly before the optical burst signal is actually transferred, the optical burst signal transfer advance notice information is input, and it is determined whether to drop or continue the optical burst signal based on this transfer advance notice information. Although the present invention does not specify the means for recognizing the transfer destination of the optical burst signal, this embodiment will be described based on a method using the second control line.
[0024]
FIG. 3 shows a transfer form of an optical burst signal transferred from node # 1 to node # 4. First, a control signal packet specifying the optical burst signal transfer time information, destination address information, and input wavelength channel number is transferred from node # 1 to node # 4. Identification information indicating which virtual ring burst traffic is further added to the control signal packet. The node # 2 that has received this control signal packet receives the virtual ring identification information, the destination node access information, the virtual ring identification information stored in the management control unit of the own node, and the output wavelength channel number that accommodates the virtual ring. The output wavelength channel number is determined with reference to the database holding At that time, the input wavelength channel number of the downstream node # 3 is also searched. Through such processing, a new control signal packet is transmitted to the downstream node # 3. This control signal packet includes the same transfer time information as the input information, the same destination address information as the input information, the same virtual ring identification information as the input information, and the input wavelength channel number of the node # 3. Here, the input wavelength channel information of the node # 3 is managed by the LMP (link management protocol: IETF DRAFT draft-ccamp-lmp-06.txt) corresponding to the output wavelength channel number of the node # 2. It is synonymous with the output wavelength channel number of the node.
[0025]
At the same time, the local node performs burst switching processing. First, registration processing is performed in a schedule table database that manages a scheduled time for setting an optical switch, an input wavelength channel number, and an output wavelength channel number. The burst switch control unit with a built-in clock performs optical switch switching processing while referring to the schedule table database. By such processing, the optical switch is driven so as to drop or continue the optical burst signal at the time when the optical burst signal corresponding to the control signal packet arrives at the node # 2. At node # 3, almost the same processing is performed as for the processing of the control signal packet, and the control signal packet is transferred to node # 4. However, since the node # 3 is not an access node of the virtual ring network 101, the setting of the optical switch is semi-fixed. Therefore, the burst switching processing as described above is omitted at node # 2, and only normal optical cross connection setting is performed.
[0026]
In the present invention, a plurality of virtual ring networks that realize such operations are defined in the optical cross-connect network. By accommodating a plurality of virtual ring networks in the optical cross-connect network based on appropriate wavelength allocation, it is possible to transmit and receive optical burst signals between all nodes. The virtual ring network is also subjected to recombination processing taking into account traffic fluctuations at the date and time levels between the nodes.
[0027]
As a result, one or a plurality of wavelength channel bands can be effectively shared by a plurality of nodes by statistically multiplexing these large-capacity contents while realizing instantaneous batch transfer of the large-capacity contents between the nodes. . In this embodiment, in particular, the shared wavelength channel is connected in a virtual ring shape between the nodes, thereby facilitating the control of the optical burst switch, and simplifying the control for contention control and ensuring fairness between the nodes. Can do.
[0028]
(First embodiment of node device realizing virtual ring optical burst transfer method)
FIG. 4 shows a first embodiment of the optical communication node of the present invention.
In the figure, the node device includes an optical switch unit 10, a management control function unit 20 that manages and controls the optical switch unit 10, and a channel management database 15. The optical switch unit 10 includes a wavelength demultiplexer 11 that receives and separates an optical signal that has been wavelength-multiplexed from an input-side wavelength multiplexing link, and an optical switch function unit 12 that outputs each optical signal to a designated path. The wavelength multiplexer 13 that multiplexes each switched optical signal and the switch control unit 14 that controls the optical switch function unit 12. The optical switch unit 10 of the present embodiment has a capability of switching between wavelength channels of a total of 128 wavelengths input from a total of eight optical fibers in 10 milliseconds or less.
[0029]
The management control function unit 20 includes a routing processing function unit (OSPF / IS-IS protocol processing function) 21 that implements optical path setting, deletion, switching, and routing, and a path setting management function unit that performs optical path setting / deletion signaling ( RSVP-TE / CR-LDR protocol processing function) 22, control line management function unit (LMP protocol processing function) 23, IP processing unit 24, and burst switch control unit 25 for monitoring faults in the control circuit network for transmitting control signals Composed.
[0030]
The routing processing function unit 21 has a function of defining a cost for each fiber link and searching for a route that minimizes the fiber link cost accumulated between the start and end nodes of the optical path to be set. The Dijkstra method is applied to the search algorithm. The path setting management function unit 22 includes a signaling processing unit that is a core of the RSVP-TE protocol, a working optical path setting / deleting processing function unit, a protection optical path setting / deleting processing function unit, and a protection optical path activation unit. Further, the working optical path setting / deleting processing function unit and the protection optical path setting / deleting processing function unit are connected to the optical channel management database 15. These functions are applied to conventional optical path setting.
[0031]
The configuration of the virtual ring network is performed by measurement data of the optical burst traffic amount between the nodes and a command from a network management system (NMS) that manages network resources of the optical cross-connect network. The NMS is equipped with an accommodation design engine for deriving an optimal virtual ring network configuration, and each node secures a wavelength channel to be a member of the virtual ring network in accordance with an instruction from the NMS.
[0032]
The management control function unit 20 has a function of receiving a command from the NMS and a function of transmitting / receiving a control signal packet from an adjacent node. The burst switch control unit 25 that processes the control signal packet includes virtual ring number information that passes through its own node, and a virtual ring database 27 that holds an input wavelength channel number and an output wavelength channel number that accommodate the virtual ring. Optical burst switching is basically performed between four parties including an add port and a drop port in addition to the input wavelength channel and the output wavelength channel.
[0033]
When a control signal packet related to burst switching processing is input to the management control function unit 20, the control signal packet is transferred to the control signal packet processing unit 26 of the burst switch control unit 25 via the IP processing unit 24. The control signal packet processing unit 26 reads the virtual ring identification number and the destination node access information included in the control signal packet and the virtual ring identification number stored in the own node, and refers to the virtual ring database 27. To determine the output wavelength channel number. Then, the input wavelength channel number of the adjacent node corresponding to the output wavelength channel number is searched, and a control signal packet reflecting the information is newly assembled and transmitted to the adjacent node. In the overhead of the control signal packet, control channel address information defined in the adjacent node is recorded as destination information.
[0034]
At the same time, the control signal packet processing unit 26 registers the input information of the control signal packet in the schedule table database 28 that manages the scheduled time for setting the optical switch, the input wavelength channel number, and the output wavelength channel number. The burst switch control unit 25 has a built-in clock 29 in which time synchronization is realized with an accuracy of the order of 100 μs in the entire network, and the control signal packet processing unit 26 switches based on the schedule table database 28 and the clock 29. Switching control of the optical switch unit 10 is performed via the drive command sending unit 30. The clock is defined by a 64-bit encoded binary time, and in this embodiment, the optical burst signal is dropped at the node from 10111110 to 11000000.
[0035]
With the node configuration shown above, a virtual ring network can be defined, and can be a specific means for realizing optical burst signal transfer.
[0036]
(Second Embodiment of Node Device for Realizing Virtual Ring Optical Burst Transfer Method)
In the first embodiment, as shown in FIG. 5A, for example, the wavelength channels constituting the virtual ring networks 101 to 104 between the nodes # 2 to # 3 are explicitly and semi-fixedly assigned. . In this embodiment, it is assumed that the wavelength channels that make up the virtual ring network are not explicitly specified. That is, M wavelength channel bands between nodes are shared among N virtual ring networks, and even if a large amount of traffic occurs between virtual ring networks, it is necessary in an autonomous and distributed manner by processing between nodes. Accommodates the transfer band of optical burst signals.
[0037]
For example, as shown in FIG. 5B, the virtual ring networks 101 to 104 between the nodes # 2 to # 3 share five wavelength channels. As a result, as shown in FIG. 5C, the virtual ring network 101 occupies three wavelengths, the virtual ring network 101 occupies one wavelength, and the virtual ring network 104 occupies one wavelength at timing t1, and the virtual ring network 102 at timing t2. 2 can be shared, and the virtual ring network 103 can occupy one wavelength and the virtual ring network 104 can occupy one wavelength.
[0038]
For the node device for that purpose, in the configuration shown in FIG. 4, a high-speed wavelength conversion function is added to the optical switch function unit 12 of the optical switch unit 10. Thereby, each input optical signal can be converted to an arbitrary wavelength at high speed. In addition to the configuration in which the high-speed wavelength conversion function is shared by the entire optical switch function unit, wavelength conversion means may be arranged at all ports on the input (output) side of the optical switch function unit 12.
[0039]
When a control signal packet related to burst switching processing is transferred to the control signal packet processing unit 26 of the burst switch control unit 25, the control signal packet processing unit 26 displays the virtual ring identification number included in the control signal packet. The destination node access information and the virtual ring identification number stored in the own node are read out, and the virtual ring database 27 and the schedule table database 28 are referred to. Here, the output wavelength channel number registered in the virtual ring database 27 is priority wavelength channel number information. First, it is searched whether this priority wavelength channel number is unused at the time when the optical burst signal corresponding to this control signal packet arrives. If unused, registration processing is performed in the schedule table database 28 so as to use this output wavelength channel number. On the other hand, if it is in use, another available output wavelength channel is searched. If there is an available output wavelength channel, the use of the output wavelength channel is registered. Further, the input wavelength channel number of the adjacent node corresponding to the output wavelength channel number is searched, and a control signal packet reflecting the information is newly assembled and transmitted to the adjacent node. If a free output wavelength channel cannot be found, the transfer of the optical burst signal for the control signal packet is blocked.
[0040]
As described above, the wavelength channel band is shared between the virtual ring networks, and burst traffic generated in each virtual ring network can be efficiently accommodated.
[0041]
【The invention's effect】
As described above, by defining a virtual ring network with the virtual ring optical burst transfer method and the node device of the present invention, in an optical path cross-connect network having an arbitrary network topology, collision of optical burst signals by simple control. An optical burst transfer network that avoids the above can be constructed. Further, according to the present invention, it is possible to instantaneously transfer a large-capacity content of a gigabyte class by an optical burst signal.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration example of an optical cross-connect network for explaining a virtual ring optical burst transfer method according to the present invention.
FIG. 2 is a diagram showing an example of bandwidth sharing of the virtual ring network 101. FIG.
FIG. 3 is a diagram showing a transfer form of an optical burst signal transferred from a node # 1 to a node # 4.
FIG. 4 is a diagram showing a first embodiment of an optical communication node according to the present invention.
FIG. 5 is a diagram showing a second embodiment of the optical communication node of the present invention.
FIG. 6 is a diagram for explaining an optical burst signal.
FIG. 7 is a diagram illustrating an optical bar string transfer method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Optical switch part 11 Wavelength demultiplexer 12 Optical switch function part 13 Wavelength multiplexer 14 Switch control part 15 Channel management database 20 Management control function part 21 Routing processing function part 22 Path setting management function part 23 Control line management function part 24 IP processor 25 Burst switch controller 26 Control signal packet processor 27 Virtual ring database 28 Schedule table 29 Clock 30 Switch drive command transmitters 101 to 104 Virtual ring network

Claims (2)

Arbitrary multiple nodes constituting an optical path cross-connect network for performing optical burst transfer are set as one group unit, and a single virtual ring network is an aggregate of optical channels that connect each node constituting the group in a ring shape. And the nodes making up this virtual ring network are interconnected by wavelength multiplexing links,
A virtual ring optical burst in which the transmission band of the virtual ring network is shared by each node constituting the group, and when the communication traffic occurs at each node, the transmission band of the virtual ring network is secured and transferred as an optical burst signal. In a node device that transfers an optical burst signal by a transfer method,
A wavelength demultiplexer that inputs and demultiplexes the wavelength-multiplexed optical signal from the wavelength-multiplexing link on the input side, an optical switch function unit that outputs the optical signal of each wavelength to the specified path, and each path An optical switch unit including a wavelength multiplexer for multiplexing the output optical signal;
The optical switch function that secures a transmission band of the virtual ring network by referring to a virtual ring identification information that accommodates the own node and a database that holds an input wavelength channel number and an output wavelength channel number that accommodates the virtual ring network A burst switch control unit for controlling the unit,
The optical switch function unit includes a wavelength conversion function for converting each input optical signal into a predetermined wavelength,
The burst switch control unit uses the output wavelength channel number registered in the database as a priority wavelength channel number, and first searches whether the priority wavelength channel number is unused at the arrival time of the optical burst signal. The node device is configured to perform control to use the output wavelength channel if used, search for another available output wavelength channel if used, and secure the transmission band of the virtual ring network. . The node device according to claim 1 ,
The burst switch control unit includes a schedule table for managing an optical switch setting, an input wavelength channel number and an output wavelength channel number, and a clock for defining the time, and matches the arrival time of the optical burst signal. A node device characterized in that a transmission band of the virtual ring network is secured.

Images