KR100275486B1 - Vitual table lookup table method for atm system - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a table lookup method for finding the address of a virtual connection table to which a received cell belongs in an asynchronous transmission system.

2. Technical problem to be solved by the invention

An object of the present invention is to provide a table lookup method for finding the address of a virtual connection table to which a received cell belongs according to a virtual channel identifier value.

3. Summary of the Solution of the Invention

A table lookup method in an exchange system, comprising: a first step of specifying a value to be used as an offset, a hash index value, and a header value; Determining whether the received virtual channel identifier is intended for a virtual path layer; A third step of reading a virtual path dedicated area using a value as an address and finding a virtual connection table if the virtual path layer is used; And a fourth step that reads the virtual path / virtual channel interface with the address to be used as the offset, if not for the virtual path layer, and searches the hash table to find the virtual linked table.

4. Important uses of the invention

The present invention is used for table lookup.

Description

A table lookup method for finding the address of a virtual connection table to which a received cell belongs in an asynchronous transmission system.

The present invention relates to a method for selecting data items from an array or table in which items are distinguished by keys in an exchange and transmission system. In particular, the present invention relates to finding the address of a virtual connection table to which a received cell belongs in an asynchronous transmission system. A computer-readable recording medium having recorded thereon a table lookup method and a program for realizing the same.

1 is a block diagram of an embodiment of a general asynchronous delivery mode system to which the present invention is applied.

In general, an asynchronous transfer mode (hereinafter, referred to as "ATM") communication exchange and transmission apparatus, as shown in the figure, the input and table lookup unit 101, the loaded table value and the input ATM cell Usage parameter control (Usage Parameter Control (hereinafter referred to as "UPC") and operation and maintenance (hereinafter referred to as "OAM") processing unit 102, routing processing unit 103, buffering and scheduling department (104), the output unit 105 can be divided.

A conventional ATM device initially uses a content addressable memory (hereinafter referred to as "CAM") to input an input port and header information to an external CAM memory, and reads associated data to provide a virtual connection. : "VC") Table lookup was performed. This method has the advantage of being quick and easy to design, but has limited the construction of large tables.

Recently, a popular method is to manage VC tables using external static random access memory (hereinafter referred to as "SRAM").

However, the conventional technique as described above has a problem in that too much space must be allocated in order to find data by simply addressing arbitrary port and header information.

In order to solve the above-mentioned problems, the present invention, in an ATM device having a connection table in an external SRAM, receives an ATM cell input from a plurality of ports and receives an input port and a virtual path identifier (hereinafter, referred to as "VPI"). Computer-readable recording method of looking up the address of the VC table to which the received cell belongs according to the value of the Virtual Channel Identifier (VCI). The purpose is to provide a recording medium.

1 is a configuration diagram of an embodiment of a general asynchronous transmission system to which the present invention is applied.

Figure 2 is an embodiment configuration of a table to which the present invention is applied.

3 is a diagram illustrating an embodiment of a connection configuration that simultaneously supports virtual path termination and virtual channel termination to which the present invention is applied.

4 is a flowchart of one embodiment of a table lookup method according to the present invention;

In order to achieve the above object, the present invention provides a table lookup method for finding the address of a virtual connection table to which a received cell belongs in an asynchronous transmission system, wherein a value to be used as an offset when reading a base table (BOFS) and a virtual channel identifier A first step of specifying a hash index value (HOFS) and a header value (HDR) by hashing the value to reduce the number of bits; A second step of determining whether the received virtual channel identifier (VCI) is reserved for a virtual path (VP) layer; As a result of the determination in the second step, if the virtual channel identifier determined for the virtual path layer is read, the virtual path dedicated area is read with the value BOFS to be used as an offset when reading the base table, and the address ADDR is addressed. A third step of finding a virtual connection (VC) table as follows; And if the virtual channel identifier determined for the virtual path layer is not determined as a result of the second step, the virtual path / virtual channel interface is read as a value (BOFS) to be used as an offset when reading the base table, and the value thereof. And a fourth step of searching the hash table from to find the virtual link (VC) table.

In addition, the present invention, in order to find the address of the virtual connection table to which the received cell belongs in the asynchronous transmission system, a value to be used as an offset when reading the base table (BOFS), virtual channel identifier in the exchange system having a large processor A first function of specifying a hash index value (HOFS) in which the value is reduced to reduce the number of bits, and a header value (HDR); A second function of determining whether a received virtual channel identifier (VCI) is destined for a virtual path (VP) layer; As a result of the determination of the second function, if the virtual channel identifier determined for the virtual path layer is read, the virtual path dedicated area is read with the value BOFS to be used as an offset when the base table is read, and the value ADDR is addressed. A third function of locating a virtual connection (VC) table by using a third function; And as a result of the determination of the second function, reads the virtual path / virtual channel interface as the address (BOFS) to be used as an offset when reading the base table, if the virtual channel identifier is not designated for the virtual path layer. And a computer readable recording medium having recorded thereon a program for realizing a fourth function of retrieving a hash table from the virtual link (VC) table.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. 2 to 4.

FIG. 2 is a diagram illustrating an embodiment of a table to which the present invention is applied. As shown in the drawing, the table includes a base table 210, a hash table 220, and a VC table 230 located in an external SRAM. do.

The base table 210 is a VP / VC common device used when the inputted cell is not known to be a virtual path ("VP") connection or a virtual channel ("VC") connection. The inputted cell belongs to the VP connection, such as the reception of a cell allocated for VP layer OAM or resource management (hereinafter referred to as "RM"), such as the area 211 and VCI = 3,4,5,6. It is divided into a VP dedicated area 212 used when it is known.

When a cell is initially entered, the VCI of the cell entered is viewed first. If the VCI is a number allocated for a special purpose of the VP layer such as 3, 4, 5, 6, the VP dedicated area 212 is read, otherwise the VP / VC interface 211 is read.

The offset to read in each area is obtained by connecting the input port number and the area used in the VPI respectively. When the VP / VC common area and the VP dedicated area are arranged side by side in memory, whether the VP layer special allocation VCI is used as the most significant bit of the base table read address is used.

The number of address bits required to distinguish the entries in the base table becomes [the number of port ID bits used + the number of bits of the VPI field used] for the common area and the VP dedicated area, respectively.

For example, if there are 16 ports (4 bits) and 8 bits of VPI are used, then 4K entries in the common area and 4K entries in the VP-only area, which requires 8K entries.

When a base table entry is read with a port ID and a VPI, it contains a single address and information about whether the connection is a VP or VC connection.

In the case of a VP connection, the VC table of the corresponding VP connection is located, and in the case of a VC connection, it has the starting address of the hash table used for two-stage search. In the case of a VP connection, the address of the VC table has already been found.

In the case of VC connection, the memory is read again by adding the hash index created using VCI to the starting address of the hash table obtained by reading the base table as before. The data read in this way indicates the starting address of the hash chain.

VC tables belonging to the same hash chain are linked to each other by linked lists using pointers inside the VC table. The hash index is created by extracting the parts used in the VCI and re-drawing only the parts used to divide them into hash chains.

For example, if you want to use only the lower 10 bits of the VCI 16 bits and limit the length of the hash chain to 4, you can use the lower 8 bits from the lower 10 bits as the hash index.

This assigns connections with the same lower 8 bits of the 10 bits to the same hash chain. In other words, VCIs are assigned to the same hash chain in the same port, with the lower 8 bits of the VCI being the same connection, for example, hexadecimal.

FIG. 3 is a diagram illustrating an embodiment of a connection configuration that simultaneously supports virtual path termination and virtual channel termination in an asynchronous transmission system to which the present invention is applied.

In the figure, 7/32 should be 17/42, 7/33 should be 17/43, and in the case of 8 / x, VCI will not be changed and VPI should be 18 and go out to 18 / x.

In this case, when the VP-AIS for VPI = 7 is received, the VC-Alarm Indication Signal (hereinafter referred to as "AIS") should be sent in the forward 17/42 and 17/43 directions.

To set and clear the AIS alarm for VP 7, there must be a VC table for VP 7, as well as a VC table for 7/32 or 7/33.

Therefore, in order to establish a connection as shown in the figure, the VPC for VPI 7, 7/32, 7/33 VC connection (VCC), and VPC for VPI 8 should be set.

Four situations can be considered in this situation.

First, when cell 7/33 is received, it reads the interface of the base table to find out that it is a VC connection and finds the VC table of 7/33 via the hash table. You will find 7/34 as well.

In the second case, when cell 8/32 is received, it reads the interface of the base table to find out that it is a VP connection and immediately finds the VC table for the 8 / x VP connection.

In the third case, when a 7/3 segment-to-segment VP-AIS cell is received, the VC table for the 7 / x VP connection is immediately read by reading the VP-only area.

4 is a flowchart illustrating a table lookup method in an asynchronous transmission system according to the present invention.

In the figure, the address used for all tables is assumed to be 24 bits, and port identifiers (Port IDentifier: hereinafter referred to as "PID"), VPI, and VCI are assumed to be extracted from only fields used in the system.

First, the VPI and VCI values of the ATM cell including the input PID will be called a header of extended meaning. In addition, the number of bits is reduced by analyzing the VCI value to divide the value to be used as an offset (Base Table Offset: hereinafter referred to as "BOFS") and all possible VCI values into several groups. A hash index value (Hash Offset: hereinafter referred to as "HOFS") is defined (401).

Determine whether the cell of the VP layer with the received VCI value. If VCI is 3,4, it is a VP layer OAM cell, and VCI 6 is also a VP layer RM cell. Depending on the ATM specification, these VCIs can be added. If the VP layer cell, go to step 403; otherwise go to step 407 (402).

Read the VP exclusive area of the base table using BOFS (PID (Port ID), VPI) as the address. The read value is the VC table address of the VP connection. This read value will be referred to as an address (hereinafter referred to as "ADDR") (for example, in the lower 24 bits of 32-bit memory) (403).

The header value (Header from Table: "HDRT") is read by adding the address of the offset containing the input header information from the VC table. (For example, if the second word of the VC table is header information, 1 is added to the ADDR value as a word address) (404).

Compare the previously read value, that is, the header value HDRT registered in the table with the header value HDRR actually input. If the values are the same, a matching VC table is found, so go to step 406. Otherwise, go to error processing of step 414 (405).

The required information is read using the VC table address found above (lookup is completed) (406).

In step 402, it is determined that it is not a VP layer cell. Therefore, the offset of the VP / VC interface of the base table is read using BOFS (PID, VPI) as an address. This reads the virtual path flag (hereinafter referred to as "VPF") and the address ADDR. (For example, the highest value of 32 bits is VPF and the lower 24 bits are called address ADDR) (407).

Check if the VPF value read earlier is 1. If 1, it is a VP connection, so go to step 404; otherwise, go to step 409 (408).

Since VPF was determined to be a VC connection as 0, the hash table is read using the ADDR value obtained earlier plus HOFS (index obtained by parsing VCI). This again gives the address ADDR of the VC table (for example, the lower 24 bit address can be called ADDR again). Also, since the search starts along the hash chain, the count (hereinafter referred to as "CNT") is set to 1. According to the hash method, the maximum length of the hash chain is predetermined (409).

The header value HDRT is read by adding the ADDR value (the address of the VC table located at the first of the hash chain) obtained above to the header offset in the VC table (410).

The HDRT obtained above is compared with the header HDRR of the actually input cell. If the values match, the corresponding VC table is found. If not, go to step 406. Otherwise, go to step 412 to consider looking again (411).

It is checked whether the CNT value is equal to the preset threshold CNT_threshold CNT_TH. If the values are the same, the number of thresholds for checking along the hash chain is reached. If not, the process proceeds to error processing of step 414. Otherwise, the process proceeds to step 413 because it needs to find more along the linked list (412).

The next address (next addr) of the VC table is added to the ADDR value previously used, and the value is read as the next address (next addr). In step 410, the header check is performed for comparison.

Since the previous matching table failed to be found, an error is handled (414).

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains, and the above-described embodiments and accompanying It is not limited to the drawing.

As described above, the present invention can support a VP connection and a VC connection for ATM cells input through a plurality of input ports at the same time, and a VP corresponding to a desired time as fast as desired without large waste of memory when the cell is input. In addition to categorizing and finding connection tables or VC connection tables, especially for VP connections, you can find them all at once, and for VC connections, you can find them in the time you want by using as much memory as you need. It can provide the completeness and convenience of, and it can be especially effective to set up a table for a VPC and a table for multiple VCCs using that VPI value for the same VPI value.

Claims (5)

A table lookup method for finding the address of a virtual connection table to which a received cell belongs in an asynchronous transmission system, A first step of designating a value (BOFS) to be used as an offset when reading the base table, a hash index value (HOFS) which reduces the number of bits by hashing a virtual channel identifier value, and a header value (HDR); A second step of determining whether the received virtual channel identifier (VCI) is reserved for a virtual path (VP) layer; As a result of the determination in the second step, if the virtual channel identifier determined for the virtual path layer is read, the virtual path dedicated area is read with the value BOFS to be used as an offset when reading the base table, and the address ADDR is addressed. A third step of finding a virtual connection (VC) table as follows; And As a result of the determination in the second step, if it is not a virtual channel identifier designated for the virtual path layer, the virtual path / virtual channel interface is read as a address (BOFS) to be used as an offset when reading the base table, and from that value. Step 4 to search the hash table to find the virtual link (VC) table Table lookup method for finding the address of the virtual connection table to which the received cell belongs in an asynchronous transmission system including a. The method of claim 1, The third step, A fifth step of reading a virtual path (VP) dedicated area of the base table, using the address BOFS as an offset when reading the base table, and storing the value ADDR; A sixth step of reading a header value (HDRT) by adding the address of an offset in which input header information is written in a virtual connection (VC) table to the stored value ADDR; And The header value HDRT registered in the table is compared with the header value HDRR actually input, and if the values are the same, the virtual connection (VC) table is set using the stored value ADDR as the address of the fifth step. Seventh step to find and error handling if the value is not equal Table lookup method for finding the address of the virtual connection table to which the received cell belongs in an asynchronous transmission system including a. The method according to claim 1 or 2, The fourth step, The virtual path / virtual channel (VP / VC) interface of the base table is read as the address (BOFS) to use as an offset when reading the base table, and the virtual path flag (VPF) and address value (ADDR) are read from the base table. Obtaining and storing the eighth step; A ninth step of determining whether the virtual channel identifier (VCI) is a virtual path (VP) connection from the virtual path flag value; A tenth step of returning to the sixth step if the virtual path connection is determined as a result of the ninth step and reading a hash table and specifying a hash chain search variable (CNT) if the virtual path connection is not determined; And The eleventh step of reading the header value HDRT by reading the address value ADDR by adding the offset of the header in the virtual connection table and using the value to find the virtual connection table. Table lookup method for finding the address of the virtual connection table to which the received cell belongs in an asynchronous transmission system including a. The method of claim 3, wherein The eleventh step, A twelfth step of reading a header value (HDRT) by reading the address value (ADDR) by adding an offset of a header in a virtual connection table; A thirteenth step of determining whether the header value HDRT matches the header value HDRR of a cell actually input; A fourteenth step of finding a virtual connection (VC) table using the address value ADDR as a result of the determination in the thirteenth step; A fifteenth step of determining whether the hash chain search variable CNT coincides with a preset threshold value CNT_TH if it does not match; And As a result of the determination in the fifteenth step, an error is processed if there is a match, and if it does not match, the offset value of the next address (next addr) is added to the address value ADDR to the next address ( 16th step of reading next addr) value and returning to the 12th step Table lookup method for finding the address of the virtual connection table to which the received cell belongs in an asynchronous transmission system including a. In a switching system having a large processor, to find the address of a virtual connection table to which a received cell belongs in an asynchronous transmission system, A first function of designating a value to be used as an offset when reading the base table (BOFS), a hash index value (HOFS) in which the number of bits is reduced by hashing a virtual channel identifier value, and a header value (HDR); A second function of determining whether a received virtual channel identifier (VCI) is destined for a virtual path (VP) layer; As a result of the determination of the second function, if the virtual channel identifier determined for the virtual path layer is read, the virtual path dedicated area is read with the value BOFS to be used as an offset when the base table is read, and the value ADDR is addressed. A third function of locating a virtual connection (VC) table by using a third function; And As a result of the determination of the second function, if it is not a virtual channel identifier defined for the virtual path layer, the virtual path / virtual channel interface is read as the address (BOFS) to be used as an offset when reading the base table, and from this value. Fourth function to search hash table to find virtual link (VC) table A computer-readable recording medium having recorded thereon a program for realizing this.