JPH10222535A - Data retrieving circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accelerate retrieval processing. SOLUTION: In a data retrieving circuit which retrieves a coinciding IP (internet protocol) from a routing table that is preliminarily stored in memory circuits 1 to 4 with 'the opposite IP address' which is externally inputted as a key and reads information that corresponds to the retrieved IP address, when the coinciding IP address does not exist in a previous retrieval data group that is acquired by a previous retrieval, a pointer that designates a different data group to be retrieved next is arranged in the previous data group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method of searching for a data group including a matching item from a data table including a plurality of data groups stored in advance in data storage means, using an item input from the outside as a key. The present invention relates to a data search circuit for reading specific data from a searched data group, and more particularly to a data search circuit suitable for a circuit that performs high-speed best match processing used in routing processing for the Internet Protocol (IP). It is about.

[0002]

2. Description of the Related Art To perform an IP routing process using an IP routing processing device (router) having a plurality of input / output ports, a 32-bit "counterpart IP address" is detected from header information of a packet arriving at an input port. Then, it is necessary to send the packet to an output port corresponding to the “other party IP address”.

At this time, it is necessary to determine to which output port the packet is to be transmitted. This is done by searching a routing table in the router using the "partner IP address" as a key, and setting a matching data group. This is done by selecting the output port that is being used.

[0004] The search process employs a best match method. In this best match process, first, a part (for example, lower) bit of the “partner IP address” is matched with the IP address in the routing table and the netmask information separately prepared for each IP address on a one-to-one basis. Is compared with the contents excluded from the target (the contents subjected to the masking processing). At this time, when a plurality of candidates match, the one with the shortest mask length (bit width) is adopted as the highest priority candidate.

[0005]

However, although this best match process is a main part of the routing process, it has conventionally been processed by software using a CPU, so that the throughput of the router itself is improved. It was a problem in letting me do that. That is, conventionally, when there is no IP address that matches the previous data group obtained in the previous search, it is necessary to obtain a pointer (next address) specifying another data group to be searched next by software calculation. There was a long time.

An object of the present invention is to perform high-speed data search processing such as the above-described best match processing, in which a part of a search key needs to be masked with separate information for each search. An object of the present invention is to provide a data search circuit as described above.

[0007]

According to a first aspect of the present invention, there is provided a data retrieving circuit which uses an item input from the outside as a key to select a matching item from a data table composed of a plurality of data groups stored in advance in data storage means. In a data search circuit that searches for a data group that includes, and reads out specific data from the searched data group, if there is no item that matches the previous data group obtained in the previous search, the next search should be performed. A pointer designating another data group is provided in the preceding data group.

The data search circuit according to a second aspect of the present invention is the data search circuit according to the first aspect, wherein the pointer of each data group in the data table is a binary tree, a linear data,
It was set to be related in other relations.

A data search circuit according to a third aspect of the present invention uses a set of mask data, IP data, a first pointer, a second pointer, and information data as one data group, and stores a data table including a plurality of the data groups. Data storage means (1 to 4), a first register (6) for temporarily holding the input "partner IP address", and a data group currently accessed in the data storage means (1 to 4). A second register (5) holding an address indicating
Third to sixth registers (for temporarily storing the IP data, the first pointer, the second pointer, and the information data of the currently accessed data group in the data storage means (1 to 4), respectively) 8-11),
A mask processor (7) for receiving the "partner IP address" from the first register (6) and performing a mask process in accordance with the mask data of the accessed data group
A comparator (12) for judging a magnitude and a matching relationship between the masked “partner IP address” output from the mask processor (7) and the content of the third register (8); The fourth register (9) when it is determined by comparison of the comparator (12) that one is greater than the other;
When it is determined that the contents of the data register are small, the contents of the fifth register (10) are output to the second register (5), and the address for accessing the data storage means (1 to 4) is updated. And a selector (13) that outputs the content of the sixth register (11) as search data when the comparison result of the comparator (12) is determined to be coincident.

[0010]

FIG. 1 is a diagram showing a configuration of a data search circuit according to one embodiment of the present invention, which is a circuit for performing a best match process in an IP routing process. Reference numerals 1 to 4 denote SRAM circuits, each of which is a memory circuit (data storage means) in which a search target is stored as a table (routing table), all of which are addressed by an address register 5.

First, the "partner I"
When the mask data for the "P address" is compared with the "other party IP address" (but masked) input to the memory circuit 2, and the result of the comparison does not match in the memory circuit 3. A pointer indicating the address of a data group to be searched next is stored in the memory circuit 4, and information to be read when the comparison result matches (for example, the IP address of the router to which the packet is to be sent next) is stored. ing.

The mask data, the IP address, the pointer, and the information constitute a data group having one address as a set, and a plurality of the data groups are individually different addresses, and the memory circuits 1 to 4 have different addresses. 4 is stored as a routing table. The pointers stored in the memory circuit 3 are two address data "left" and "right".

Reference numeral 6 denotes a register for storing an input “partner IP address”; 7, a mask processor for performing a mask process on a specific bit of the “partner IP address” with mask data read from the memory circuit 1; Is the memory circuit 2
A register for storing the “search IP address” read from the memory circuit 9 is a pointer “left” read from the memory circuit 3
Is a register for storing the pointer "right" read from the memory circuit 3, and 11 is a register for storing information read from the memory circuit 4.

Reference numeral 12 denotes the “other party IP address” masked by the mask processor 7 and the “search I” stored in the register 8.
A comparator for comparing "P address" with each other, and determines whether or not the two addresses match. If the two data do not match, the input data is regarded as an integer of 0 or more. If it is larger than "0", it outputs "0";

A selector 13 selects and outputs the data of the register 9 or the data of the register 10 according to the content of the mismatch when the comparison result of the comparator 12 does not match.
Is a selector that initially selects an "input head address" to be input according to the "other party IP address", and then selects the output data of the selector 13. Reference numeral 15 denotes a pointer output from the selector 13 indicating "address 0". At this time, it is an end judging unit that outputs a signal of "no match data".

Next, the operation will be described. First, the “destination IP address” is stored in the register 6, and the “input head address” corresponding to the “destination IP address” is stored in the register 1.
4 via the selector 14. This selector 1
4 is set to input data (pointer) from the selector 13 for the next processing after the storage in the register 5 is completed.

Next, the mask data, the IP address, the pointer "left, right", and the information of the memory circuits 1 to 4 are read out by the "input head address" stored in the register 5, and the mask processing unit 7, Register 8,
9, 10, and 11. Here, the “partner IP address” of the register 6 is subjected to mask processing in the mask processor 7 and becomes one input of the comparator 12.

The comparator 12 compares the “partner IP address” output from the mask processor 7 with the “search IP address” output from the register 8. It instructs to output the information stored there as a search result.

However, if the "other party IP address" is "search I
When it is larger than the "P address", the selector 9 selects the register 9 and the pointer "left" stored therein is selected.
Is stored in the register 5 via the selector 14, and new addressing is performed on the memory circuits 1 to 4 with the content of the pointer "left" to perform a search again. Conversely, when the “partner IP address” is smaller than the “search IP address”, the selector 13 selects the register 10 and stores the pointer “right” stored therein in the register 5 via the selector 14. Then, new addressing is performed using the content of the pointer "right" and the search is performed again.

In this way, the comparison process and the search are repeated until the comparator 12 outputs a coincidence signal. But,
When the pointers “left” and “right” coming out of the selector 13 indicate “address 0”, the end determiner 15
As a result, the signal of "no matching data" is output to the outside, and the processing is interrupted.

As described above, since the pointer is registered in the memory circuit 3 in advance, there is no need for a means for generating the pointer by software calculation or the like as in the prior art, and the speed of the search process can be increased. Further, when a pointer generation circuit is provided in hardware, a circuit for lowering the entire processing speed such as an adder is normally required, but the processing speed is further improved since such a circuit is not required.

FIG. 2 is a diagram showing one form of storing data in the memory circuits 1 to 4 in FIG. This is a schematic representation of a data storage format when storing data in a binary tree format as shown in the upper part of FIG. By storing nine data from A to I in a table as shown in the lower part of FIG. 2, the binary tree search processing in the circuit of FIG. 1 can be realized. At this time, A, B,
C,. . . . , I are stored in this order, the comparison process is performed in that order, so that the best match process can be realized using the circuit of FIG.

FIG. 3 is a diagram showing another format of storing data in the memory circuits 1 to 4 of FIG. When the pointers of the same value are stored in "left" and "right" as shown on the right side of FIG. 3, the data retrieval structure shown on the left side is obtained. When this is applied to the circuit of FIG. A linear search can be performed sequentially.

As described above, in this embodiment, a binary tree search or a linear search can be realized by appropriately setting / changing the value of the pointer stored in the memory circuit 3. It is also possible to search for a method, and there is no need to change the search circuit.

[0025]

As described above, according to the present invention, when there is no item corresponding to the previous data group obtained in the previous search, the pointer for specifying another data group to be searched next is set to the previous data group. Since it is held in the group, the pointer for the next search can be obtained by referring to it without calculating the pointer for the next search, and it is applied to the best match processing of the IP routing processing. However, the processing speed can be increased, and the throughput can be improved.

Further, since the data search order can be substantially changed only by changing the data structure of the pointer stored in the data storage means, even if the circuit is once constructed, the data can be changed without changing the circuit. There is an advantage that it is possible to easily realize a search of a method that matches the characteristics of the above.

Further, only by using a simple circuit configuration such as a register and data storage means, a data search which requires a part of a search key to be masked with separate information for each search including a best match process. There is also an advantage that a data search circuit that executes processing can be realized.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a configuration of a data search circuit according to one embodiment of the present invention.

FIG. 2 is an explanatory diagram of the configuration of a data table when implementing a binary tree search.

FIG. 3 is an explanatory diagram of a configuration of a data table when realizing a linear search.

Claims (3)

[Claims] 1. A data group including a matching item is searched from a data table composed of a plurality of data groups stored in advance in a data storage means, using an item input from the outside as a key, and the data group of the searched data group is searched. In a data search circuit for reading out specific data in the data, when there is no item that matches the previous data group obtained in the previous search, a pointer designating another data group to be searched next is set to the previous data. A data search circuit characterized by being provided in a group. 2. The data search circuit according to claim 1, wherein the pointer of each data group in the data table is
A data search circuit, wherein the individual data groups are set so as to be associated in a binary tree, linear, or other relationship. 3. A data storage means (1 to 3) in which a set of mask data, IP data, a first pointer, a second pointer, and information data is regarded as one data group and a plurality of data tables are stored. 4) and the first to temporarily hold the input “other party IP address”
A register (6); a second register (5) for holding an address indicating a data group currently being accessed in the data storage means (1 to 4); and a current register in the data storage means (1 to 4). Third to sixth registers (8 to 11) for temporarily holding the IP data, the first pointer, the second pointer, and the information data of the data group being accessed; and the first register (7) a mask processor (7) for receiving the "partner IP address" from (6) and performing a mask process in accordance with the mask data of the accessed data group
And the masked "partner IP address" output from the mask processor (7) and the third register (8).
The comparator (1
2), the content of the fourth register (9) is determined when one is greater than the other by the comparison of the comparator (12), and the content of the fifth register (10) is determined when the content is determined to be smaller. A selector (13) for outputting contents to the second register (5) and updating an address for accessing the data storage means (1 to 4); A data search circuit for outputting the contents of the sixth register (11) as search data when the result is determined to be coincident.