KR20010018534A - Apparatus and Method for packet switching using ATM cell switching - Google Patents

Abstract

PURPOSE: A packet exchange structure using an ATM cell switching function and a method for processing thereof are provided to achieve a high-speed packet by making packet exchange executed by the ATM cell and to transfer traffics using a traffic control function by virtual connections. CONSTITUTION: An input cell processing part(100) is comprised of a cell header processing part(110), a routing table(130) and a header conversion table(140). The cell header processing part(110) makes an intermediate cell having information indicating an output port number and a packet buffer number and transfers it to a cell switch part(200). The routing table(130) stores information to determine an output port number and an output virtual connection number using a destination address value comprised in a packet header. The header conversion table(140) stores the output port number, the output virtual connection number and the packet buffer number. An output cell processing part(400) is composed of a queue management part(420), an index table(430), a cell scheduler(450), a packet buffer part(440) and an empty packet buffer number queue(410). The queue management part(420) stores an inputted intermediate cell in a packet buffer appointed by a cell header and, if all the cells forming a packet arrive, connects an associated packet buffer to a virtual connection queue assigned for the relevant packet. The index table(430) stores link information composing each virtual connection queue. The cell scheduler(450) determines a point of cell output time using the queue information of the index table(4300 and band width information assigned for each virtual connection and outputs a specific virtual connection cell. A plurality of packet buffers(440) store cells forming a packet. The empty packet buffer number queue(410) stores the numbers of empty packet buffers among the packet buffers.

Description

Packet Switching Structure Using Asynchronous Transfer Mode Cell Switching and Its Processing {Apparatus and Method for packet switching using ATM cell switching}

The present invention relates to a structure of a packet switch using an asynchronous transmission mode (hereinafter referred to as ATM) cell switching function and a processing method thereof.

The present invention relates to a switch that performs a packet switching function using a cell switching technology, so that the output port to the cell output is determined by the destination address of the packet header to which the cell belongs, instead of the virtual channel identifier of the ATM cell header, A packet unit multiplexing function is provided so that cells destined for the same destination at the output terminal can be multiplexed by packet unit.

One of the related arts for ATM cell-based packet exchange is a method of using a cellized packet as it is in an ATM switch. Whenever the destination of a packet is changed, a virtual connection is established to a new destination, and when the delivery of the packet is terminated, the virtual connection is established. It requires a complicated control process to release it.

In order to perform this process, an additional protocol that obtains an ATM address corresponding to a destination address of a packet and then establishes a virtual connection to a destination corresponding to an ATM address must be applied. Meanwhile, Classical IP over ATM, LAN Emulation, Multi-Protocol over ATM, Multi-Protocol Label Switching, and Next Hop Resolution Protocol are protocols that perform the above functions made by standardization organizations.

As another conventional technology for one packet exchange, the internal switching is performed on a packet basis, and an input unit converts an input cell into an original packet, and an output unit converts the switched packet back to a cell and outputs the converted input / output unit. As a result of performing the packet-cell conversion process, the configuration is complicated and the processing delay is high.

As described above, the conventional technology of exchanging packets in cell units has been applied to an ATMless connectionless server. However, this technique uses ATM Adaptation Layer (AAL) 3/4 to multiplex the payload of a cell separately. Even if the packet is demultiplexed to the same destination by cell identifier and multiplexed to the same destination by cell unit, the original packet can be restored at the destination.However, the packet-cell conversion process is complicated and the cell transfer efficiency is low. In addition, the prior art has a problem that can not process the cellized packet according to the AAL5 specification.

1 shows a structural diagram of a general ATM switch. In the above structure, the input line matching unit 1 into which the cell is input is determined according to the virtual connection values of the input cells, and then the output port number is output to the cell switch unit 2. The output line matching unit 3 transmits the cells of each channel according to the designated bandwidth.

In general, each port has a plurality of virtual connections, and cells must be output according to a predetermined bandwidth for each virtual connection.

In order to solve the above problems, the present invention enables a high-speed packet by hardware by performing a packet exchange in an ATM cell unit, and to the end-to-end guaranteed band by using a traffic control function for each virtual connection of an ATM switch. It is an object of the present invention to provide a packet exchanger capable of carrying traffic.

In order to achieve the above object, the present invention, if the input cell is the first cell constituting the packet, and determines the output port corresponding to the destination address included in the cell, the packet buffer to store the packet from the port where the cell is output An input cell processing means for receiving the number and adding it to the header and transferring it to the cell switch unit, and if it is not the first cell, adding and transmitting the same packet buffer number of the same output port as the first to the header, and outputting the cell header. Cell switch means for transferring a cell to a port designated by a port number value, and stored in a buffer specifying a packet buffer number of a cell header passing through the cell switch means, and when all cells constituting one packet arrive, the packet buffer Is connected to a corresponding virtual connection queue, and output cell processing means for outputting cells in each virtual connection queue with a specified bandwidth, and the input cell processing means Each time the empty packet buffer number of the output cell processing means is requested, a port selection means for reading the empty packet buffer number from the empty packet buffer number queue of the output cell processing means is provided and provided a predetermined virtual connection number to the output cell processing unit. And a second process of processing a cell when the intermediate cell is input, and a second process of outputting a cell when the output of the cell is requested.

In the ATM cell-based packet exchanger of the present invention, a technique for delivering a plurality of cells constituting a packet to a destination designated by a packet's destination address, and cell-by-cell when packets destined for the same destination arrive simultaneously from multiple sources A technique for enabling multiplexing of packets rather than packet must be solved.

Therefore, the ATM switch determines the destination to be delivered by the virtual channel identifier in the header of every cell. However, in the packet switch, only the first cell among the cells that make up the packet contains the destination address. It must be delivered to the same destination as the first cell.

Therefore, in the present invention, it is assumed that all packets are cellized in the form of AAL5, and the last cell constituting the packet is detected by the payload type region of the cell header to find the boundary point of the packet from the cell flow. Detects and finds the boundary of the packet from the cell flow, and stores the output port value retrieved from the routing table and the routing table that determines the output port to which the packet is forwarded from the destination address in the first cell of the packet. The header conversion table is configured to allow the subsequent consecutive cells constituting the NN to be delivered to the same destination so that several cells constituting one packet can be delivered to the same destination.

Since several cells constituting a packet must be delivered continuously in the same virtual connection, traffic destined for the same destination must be put in the output queue in packet units.

Each output port must be able to handle thousands of virtual connections, each channel forming an independent queue, and each queue has multiple packet buffers that can store cells on a packet-by-packet basis. The complex process of storing cells arriving from the network in different packet buffers must be performed.

Accordingly, in the present invention, in order to simplify the allocation of the packet buffer in which the cells are to be stored, whenever a new packet arrives at the input unit, the packet buffer in which the corresponding packet is to be stored is pre-allocated so that the intermediate cell receives the packet buffer number in which the cell is to be stored. In addition, it solves the packet buffer allocation and packet unit multiplexing problem by transmitting to the output unit.

1 is a block diagram of a general ATM switch,

2 is a block diagram of a packet switch according to the present invention;

3 is a diagram illustrating a connection relationship between an input cell processor and an output cell processor to which the present invention is applied;

4 is a configuration diagram of an input cell processing unit according to the present invention;

5 is a process configuration diagram of dividing a packet into fixed length ATM cells according to the present invention;

6 is a configuration diagram of an intermediate cell delivered between an input cell processor and an output cell processor according to the present invention;

7 is a configuration diagram of an output cell processing unit according to the present invention;

8 is a configuration diagram illustrating the relationship between the index buffer and the virtual connection queue of the output cell processing unit according to the present invention;

9 is an operation flowchart when a cell is input to an output cell processing unit according to the present invention;

10 is a flowchart illustrating a process of outputting a cell in an output cell processor according to the present invention.

* Explanation of symbols for main parts of the drawings

100: input cell processing unit 110: cell header processing unit

120: header conversion table 121: packet boundary indicator

122: output virtual connection number 123: output port number

124: packet buffer number 130: routing table

131: destination address 132: output virtual connection number

133: output port number 200: cell switch unit

300: port selector 400: output cell processor

410: empty packet buffer number queue 420: queue management unit

430: index table 431: tail buffer

432: head buffer 433: cue counter

440: packet buffer 441: cell counter

442: connection pointer 450: cell scheduler

460: packet processing unit

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram of a packet switch according to the present invention. If the input cell is the first cell constituting the packet, the packet exchanger receives the packet number to store the packet from the port where the cell is output and adds the packet number to the header to the cell switch unit. And, if it is not the first cell, the input cell processing unit 100 for creating and transmitting a header so that it can be stored in the same packet buffer of the same output port as the first cell, and delivers the cell to the port designated by the output port number value of the cell header. The cell switch unit 200 and a buffer buffer for specifying the packet buffer number of the cell header passing through the cell switch unit are stored. When all cells constituting one packet arrive, the packet buffer is connected to the queue of the virtual connection. Output cell processing unit 400 for outputting the cells in the queue of each virtual connection with a specified bandwidth, and the empty packet buffer number of the specific output cell processing unit in the input cell processing unit 100 Each time, the port selector 300 reads the empty packet buffer number from the empty packet buffer number queue of the corresponding output cell processing unit and provides the port selection unit 300.

3 is a view including the detailed configuration of the input cell processing unit 100 and the output cell processing unit 400 in the configuration of FIG.

The input cell processing unit 100 searches for a routing table and a header conversion table by using the header value of the input cell, converts the virtual connection identifier of the header into a value to be output, and determines a port to be output from the cell switch unit. Cell header processing unit 110 for creating an intermediate cell to which the port buffer and the packet buffer number of the output cell processing unit to store the cell are added to the cell and delivering the intermediate cell to the cell switch unit, and outputting the destination address value included in the packet header. Packet buffer of the output cell processing unit obtained through the routing table 130 storing information for determining the output port number and the virtual connection number of the cell to be output, and the output virtual connection number, output port number, and port selection unit found in the routing table. It consists of a header conversion table 120 that stores the number.

In addition, the output cell processing unit 400 stores the input intermediate cell in a packet buffer designated by the cell header, and connects the packet buffer to the virtual connection queue allocated to the packet when all cells constituting one packet arrive. Queue management unit 420, an index table 430 storing link information constituting a virtual queue for each virtual connection, an output time point of a cell by using queue information of the index table and bandwidth information allocated to each virtual connection A cell scheduler 450 for outputting a cell of a specific virtual connection, a plurality of packet buffers 440 for storing cells constituting one packet, and an empty packet for storing the number of empty packet buffers among the packet buffers. It is composed of a buffer number queue 410.

Cells constituting the packet of the present invention are received by the input cell processing unit 100 receives the packet buffer number to be stored in the packet is transmitted to the output cell processing unit 400, the allocation of the buffer for storing cells for each virtual connection, packet per packet This ease of configuration not only simplifies the configuration of the queue manager but also makes it easy to configure packet-by-packet multiplexing of multiple packets destined for the same destination.

4 illustrates a detailed configuration of the input cell processor of FIG. 3. In the configuration, the header conversion table 120 includes an output virtual connection number 122, an output port number 123, and a packet buffer number corresponding to the virtual path identifier / virtual channel identifier (VPI / VCI) value of the input cell. 124) and a packet boundary indicator 121 which is set when the value of the payload type region is a value indicating the end of the packet so as to distinguish the first cell of the packet including the destination address. Has)

In addition, the routing table 130 stores the output port number and the virtual connection number corresponding to the destination address value, the cell header processing unit 110 retrieves the header conversion table of the virtual connection when the cell is input, packet boundary If the indicator is set, it indicates the first cell constituting the packet. Thus, the destination address value is extracted from the cell and the routing table 130 is searched using this value to output the output virtual connection number 132 and the output port number 133. Read it.

In addition, through the port selection unit 300, the output cell processing unit 400, which is designated by the output port number, obtains the packet buffer number in which the cell is to be stored, together with the output virtual connection number 132 and the output port number 133, together with the header conversion table. Stored in (120), and also makes an intermediate cell with these values as a header and delivers it to the cell switch unit (200).

If the packet boundary indicator is not set by searching the header conversion table 120, it means that the cell is not the first cell of the packet. Therefore, the cell stored in the header conversion table 120 is read and stored as a header value. The cell is made and delivered to the cell switch unit 200.

In this case, since the information obtained from the routing table 130 and the output cell processor 400 is transmitted as a header value when the first cell arrives, a plurality of cells constituting the same packet are delivered to the same destination.

5 shows a process in which packets are cellized in the form of AAL5. The packet is divided into a packet header including a destination address and an information area. The packet is divided into 48 byte units after an error detection code for error detection is added to the trailer, and an ATM cell header of 5 bytes is added to the ATM cell. Configure

In an ATM network, a plurality of cells constituting a packet must be delivered in succession through the same virtual connection. Therefore, when an AAL5 cell packetized in one virtual connection is multiplexed on a cell-by-cell basis, the original packet may be restored at the destination. Must be multiplexed by packet.

6 shows an intermediate cell configuration of the present invention, in which the input cell processing unit 100 converts the virtual connection number of the header value of the input cell into the output side virtual connection number, and output port number 123 to be used in the cell switch unit 200. And the packet buffer number 124 to be used in the output cell processing unit 400 are added to the cell switch unit 200.

7 is a block diagram of an output cell processing unit according to the present invention. The packet processing unit 460 stores an intermediate cell in an appropriate packet buffer 440. When the arrival of all cells constituting one packet is completed, the packet is processed. It connects the buffer 440k to the virtual connection queue, and outputs the cells stored in the queue for each virtual connection with a specified bandwidth and stores the number of the used packet buffer in the empty packet buffer number queue 410. . This performs the functions of the queue manager 420 and the cell scheduler 450 of FIG.

The buffer 440 has more packet buffers 440 than the number of virtual connections that the output cell processing unit 400 can process, and each packet buffer can store the packet buffer numbers linked when configuring the queue for each virtual connection. And a cell counter 441 indicating the number of cells stored in the packet buffer.

The index table 430 is a queue indicating the number of head buffers and tail buffers 431 and 432 that designate a buffer number constituting the head and tail of the virtual queue for each virtual connection, and the total number of cells stored in the virtual queue for each virtual connection. It has a counter 433.

The queue counter 433 may be used by the cell scheduler 450 to determine the output order of cells.

The empty packet buffer number queue 410 stores the number of the packet buffer 440 in which the cell is not stored, and the packet buffer passes through the port selection unit 300 whenever a request is received from the input cell processing unit 100. Pass the number of 440.

8 shows a relationship between an index table and a virtual queue of virtual connections. The virtual queue of the virtual connection number i indicates the packet buffer number constituting the head, and HBi of the index table 430 indicates the packet buffer number constituting the tail. The packet buffers between the head and tail are connected by connection pointers within each packet buffer.

9 is an operation flowchart when a cell is input to an output cell processing unit according to the present invention. First, when an intermediate cell having a virtual connection number i is input to the output cell processing unit 400 (S1), a packet buffer in the header of the intermediate cell is shown. The packet buffer designated by the number is selected, the cell is stored at the position designated by the cell counter in the packet buffer (S2), and the cell counter value is increased (S3).

If it is determined whether the payload type value of the intermediate cell is the last cell of the packet (S4), it ends if the payload type value is not the last cell (S5).

After the determination, if the payload type value indicates the end of the packet, the packet buffer is connected to the virtual queue of the virtual connection.

In this case, it is determined whether the queue counter value of the corresponding virtual connection of the index table is 0 (S6). If the queue counter value is 0, the queue of the virtual connection is not present. Therefore, the packet buffer number is written to both HBi and TBi (S7). Configure the queue of the virtual connection with the packet buffer.

If the value of the queue counter is not 0 after the determination, since the queue is already set, the packet buffer number is added to the connection pointer of the packet buffer designated by TBi (S8) and the TBi value is added again. Replace.

After adding the packet buffer to the virtual queue, add the cell counter value of the packet buffer to the queue counter value of the corresponding virtual connection of the index buffer (S9) to specify the number of cells stored in the entire queue. The cell counter is changed to 1 (S10) to be used as a pointer when outputting the cell of the packet buffer, and the process ends (S11).

FIG. 10 is a flowchart illustrating a process of outputting a cell by an output cell processor according to an exemplary embodiment of the present invention, and illustrates an operation procedure when a cell scheduler requests a cell output of a virtual connection i.

If the cell scheduler requires cell output with virtual connection number i (S12), the cell buffer reads the cell at the location specified by the cell counter from the packet buffer designated by HBi in the index table and increases the cell counter value (S13). After specifying the stored position, the queue counter value of the index table is decreased (S14) to indicate the number of cells actually stored in the queue.

It is determined whether the output cell is the last cell of the packet (S15). If the payload type value of the output cell indicates that the packet is the last cell of the packet, the connection pointer value of the packet buffer that transmitted the cell is read to the HBi of the index table. After writing (S16), change the cell counter of the packet buffer that sent the cell to 0, write the packet buffer number to the empty packet buffer number queue, terminate and end (S17). Otherwise, it ends (S18).

As described above, the present invention relates to the configuration of a packet switch having an ATM input / output interface. Although the output port and the output virtual connection are determined by the destination address value of the packet, all processes are performed in units of hardware. Switching technology makes it easy to configure a high-speed, high-capacity packet switch.

In addition, by applying the method of adding packet buffer numbers to be stored in the input cell processor to the header, the output cell processor simultaneously performs the queuing function of the virtual connection unit and the packet unit multiplexing. In this case, a packet switch having an ATM interface does not need to have a cell-to-packet conversion function, thereby simplifying the configuration.

In addition, even in a packet exchanger having a packet input / output interface, the present invention converts a cell into an internal cell and applies the present invention, whereby the packet exchanger can be easily configured when processing on a cell basis.

Claims (10)

In the packet exchanger processing on a cell basis, If the input cell is the first cell constituting the packet, the output port corresponding to the destination address included in the cell is determined, and the packet buffer number to store the packet from the port to which the cell is output is added to the header and added to the cell switch. An input cell processing means for transferring to the header and, if it is not the first cell, adding the same packet buffer number of the same output port as the first to the header and transmitting the same; Cell switch means for transferring a cell to a port designated by an output port number value of the cell header; The packet buffer number of the cell header passing through the cell switch means is stored in a buffer, and when all cells constituting one packet arrive, the packet buffer is connected to a corresponding virtual connection queue, and cells in each virtual connection queue. Output cell processing means for outputting them with a specified bandwidth; And a port selection means for reading and providing the empty packet buffer number from the empty packet buffer number queue of the corresponding output cell processing means whenever the input cell processing means requests the empty packet buffer number of a specific output cell processing means. Packet Switch Architecture using Asynchronous Transfer Mode Cell Switching. The method of claim 1, wherein the input cell processing means The routing table and the header conversion table are searched using the inputted header value of the input cell to convert the virtual connection identifier of the header to the output value, and the output port number for determining the port to be output from the cell switch unit, and the output at which the cell is stored. A cell header processing unit for creating an intermediate cell in which information indicating a packet buffer number of the cell processing unit is added to the cell and delivering the intermediate cell to the cell switch unit; A routing table storing information for determining an output port number and a virtual connection number to be outputted to a cell by using a destination address value included in the packet header; And And a header conversion table for storing the output virtual connection number, the output port number, and the packet buffer number of the output cell processor obtained through the port selection unit. The method of claim 2, wherein the intermediate cell is The input cell processing unit converts the virtual connection number from the header value of the input cell to the output virtual connection number, and the cell switch unit makes the intermediate cell with the output port number to be used and the packet buffer number to be used in the output cell processing unit and delivers it to the cell switch unit. Packet switch structure using the asynchronous transmission mode cell switching function, characterized in that. The method of claim 2, wherein the header conversion table Set when the output virtual connection number, output port number, packet buffer number corresponding to the virtual connection identifier value of the input cell and the payload type area value of the input cell are the last cell of the packet. A packet switch structure using an asynchronous transmission mode cell switching function, characterized in that it has a packet boundary indicator. The method of claim 1, wherein the output cell processing means A queue manager for storing the input intermediate cell in a packet buffer designated by the cell header and connecting the packet buffer to a virtual connection queue assigned to the packet when all cells constituting one packet arrive; Index output that stores the link information constituting the virtual connection queue for each virtual connection, the virtual queue information in the index table and the bandwidth information allocated to each virtual connection to determine the output time of the cell to determine the specific virtual connection A cell scheduler for outputting a cell; A plurality of packet buffers storing cells constituting the one packet; And The packet switch structure using an asynchronous transmission mode cell switching function, characterized in that the packet packet number queue for storing the number of the empty packet buffer of the plurality of packet buffers. The method of claim 5, wherein the index table Asynchronous transmission mode comprising a head buffer and a tail buffer for designating the buffer number constituting the head and tail of the virtual queue for each virtual connection, and a queue counter indicating the total number of cells stored in the virtual queue for each virtual connection. Packet Switching Architecture Using Cell Switching Function. The method of claim 5, wherein the empty packet buffer number queue A packet switch using an asynchronous transmission mode cell switching function, which designates a packet buffer number in which a cell is not stored, and transmits the packet buffer number through a port selector whenever a request is received from the input cell processing unit. rescue. In a method for facilitating multiplexing of packet units at an output port by allocating a packet buffer of an output port to which a corresponding cell is output each time a start cell of each packet is input. A first step of processing an intermediate cell having a predetermined virtual connection number in the output cell processor; And a second process of outputting the cell by the output cell processor when the output of the cell is requested. The method of claim 8, wherein the first process is When the incremental cell with virtual connection number i is inputted to the output cell processing unit, the packet buffer designated by the packet buffer number in the header of the intermediate cell is selected, the cell is stored in the position designated by the cell counter in the corresponding packet buffer, and the cell counter value A first step of increasing; Determining whether the payload type value of the intermediate cell is the last cell and ending if the effective load type value is not the last cell; A third step of connecting the packet buffer to the virtual queue of the virtual connection if the payload type value indicates the end of the packet after the determination; If the queue counter value of the corresponding virtual connection in the index table is 0, and the queue counter value is 0, the corresponding packet buffer number corresponding to the absence of the queue of the virtual connection is written in both HBi and HBi, which corresponds to one packet buffer. A fourth step of constructing a queue of virtual connections; After the determination, if the queue counter value is not 0, the packet buffer number corresponding to the queue has already been set is written into the connection pointer of the packet buffer designated by TBi, and the TBi value is replaced with the number of the packet buffer added. A fifth step; Adding a packet buffer to the virtual queue and adding a cell counter value of the packet buffer to the queue counter value of the corresponding virtual connection of the index buffer to specify the number of cells stored in the entire queue; And a seventh step of changing the cell count of the added packet buffer to 1 so that the packet buffer cell can be used as a pointer when outputting the cell of the packet buffer and ending. The method of claim 8, wherein the second process If the cell scheduler requires cell output with a certain virtual connection number, read the cell at the location specified by the cell counter from the packet buffer specified by the index table HBi, and increase the cell counter value to specify the location where the next cell is stored. Reducing the queue counter value of the index table and outputting the number of cells actually stored in the queue; If it is determined that the output cell is the last cell of the packet and indicates that the payload status value of the output cell is the last cell of the packet, the value of the connection pointer of the packet buffer that transmitted the cell is read and written into the HBi of the index table. A second step of changing the cell counter of the transmitted packet buffer to 0 and writing the packet buffer number to the empty packet buffer number queue and ending; And a third step of terminating if the outputted cell is not the last after the determination.