KR100420959B1 - CAM lookup table management method based on LPM. - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a router that performs routing in a computer network. Specifically, an IP that finds an output port by referring to a destination address of an IP packet by reading an Internet Protocol (IP) packet. A lookup table management method and management apparatus. The method includes providing a pair of pointers for each data band having the same length of prefix, and adding data to a content addressable memory (CAM) lookup table, the data having a prefix length greater than the prefix length of the data to be added. For each band of, recording data of an address stored by the upper pointer of each band in an address stored by a lower pointer of each band, and recording data to be added in a space indicated by a lower pointer of a data band to be added It includes.

The present invention has the effect of reducing the number of movements of data stored in the content addressable memory (CAM) table and the overall data update time when the prefix length of the added data is larger than N / 4 on average. have.

Description

CAM lookup table management method based on LPM. LPM-based content addressable memory (CAM) lookup table that adds data from upper address space

The present invention relates to a router that performs routing in a computer network. More specifically, an output port is referred to by reading an Internet Protocol (IP) packet and referring to a destination address of the IP packet. It relates to how to manage the lookup IP lookup table.

In this case, when a next hop is found by referring to a destination address, a longest prefix matching (LPM) that searches for a match from the address information having the longest prefix with the destination address of the IP packet. There are several ways to implement this LPM.

One method is implemented using Content Addressable Memory (CAM) in order of data with long prefix from low address to high address. Then, when data of length n is added, items with a length 0 prefix are sequentially moved from the item having a length n-1 to a higher address direction in order, and then a prefix item of length n is moved. Save it.

However, in this case, if an item having a prefix longer than N / 4 is added on average, there is a problem that more than N / 4 moves must be made to secure the necessary space. Needs to be.

In order to solve the above problem, in the present invention, when a prefix length of data to be added is larger than N / 4 on average, an empty area is located at a lower address, and data is added after moving to a lower address direction. It is an object of the present invention to provide a method of reducing data update time as a whole by recording data added to an area having a prefix length to reduce the number of shifts of content addressable memory (CAM) lookup data on average.

1 is a block diagram of a forwarding engine for routing performed in a conventional router.

2 is a data storage state diagram of a conventional lookup table.

3 is a diagram illustrating an additional method when adding data of a conventional prefix length n.

4 is a diagram illustrating an additional method in the case of adding data of prefix length n of the present invention.

5 is a configuration diagram of a forwarding table management apparatus of the present invention.

FIG. 6 is a representation of a content addressable memory (CAM) storage state and pointer of data with prefix length i. FIG.

FIG. 7 is a storage state diagram in a content addressable memory (CAM) in the presence of data of length 0 to 32 prefix; FIG.

FIG. 8 is a flow diagram illustrating the process of adding data to a Content Addressable Memory (CAM) table of the present invention. FIG.

Fig. 9 is a diagram showing a storage state and a pointer in a content addressable memory (CAM) of data having a prefix length of N / 2-1;

FIG. 10 is a diagram illustrating an additional process when prefix data of length 0 is added when prefix data of lengths 2 and 1 are stored. FIG.

In order to achieve the above object, according to the present invention, a lower pointer that stores next address information of data having the lowest address among data included in the band for each data band in which data having a predetermined prefix length is stored, and the prefix length is the same. Providing an upper pointer storing address information of data having the highest address among the data; When data is added to the content addressable memory (CAM) lookup table, for each band of data having a prefix length exceeding the prefix length of the data to be added, the data of the address stored by the upper pointer of each band is stored. Recording at an address stored by the lower pointer of each band; And storing data to be added at an address stored by a lower pointer to a band of data having a prefix length equal to the prefix length of the data to be added, the content addressable memory (CAM) using Longest Prefix Matching (LPM). Provides a way to manage lookup tables in).

In order to achieve the above object, the present invention provides a content addressable memory (CAM) including a lookup table for storing data having a long prefix length from a low address; Each band of data having the same prefix length includes a lower pointer that stores the next address of the data having the lowest address among the data having the same prefix length, and a higher pointer which stores the address of the data having the highest address among the data having the same prefix length. Pointer storage; And data added to the lookup table of the content addressable memory (CAM), for each band of data having a prefix length greater than the prefix length of the data to be added; Is recorded at an address stored by the lower pointer of each band, data to be added to an address stored by a lower pointer to a band of data having the same length as the prefix length of the data to be added, and is stored in the pointer storage unit. A content addressable memory (CAM) lookup table management apparatus using an LPM including a table management unit for updating an address stored by an upper pointer and a lower pointer included therein is provided.

In order to achieve the above object, the present invention provides a computer-readable recording medium having recorded thereon a program for executing the above method on a computer.

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

1 is a block diagram of a forwarding engine for routing performed in a conventional router.

The forwarding engine 110 of the router extracts a destination address from the incoming IP packet 100 and a next hop determiner to obtain a next hop corresponding to the destination address. 120 obtains the next hop with reference to forwarding table 130 having information about the next hop, and forwards the IP packet to the next hop.

In this case, when a next hop is found by referring to a destination address, a longest prefix matching (LPM) that searches for a match from the address information having the longest prefix with the destination address of the IP packet. There are several ways to implement this LPM.

2 is a data storage state diagram of a conventional lookup table.

The conventional method is implemented using a content addressable memory (CAM) in order of data having a long prefix from a low address to a high address as shown in FIG. 2. In other words, an item 210 having a prefix of length N / 2-1 is located at the top, followed by an item 220 having a prefix of length N / 2-2. In this order, an item 230 having a length 1 prefix is located in the high address direction, and an item 240 having a length 0 prefix is located. And at the bottom there is an empty area.

3 is a diagram illustrating an additional method in the case of adding data of a conventional prefix length n.

When data of length n is added, items 310 having a length 0 prefix are sequentially moved from an item 320 having a length n-1 to a high address direction in order, and then a prefix of length n prefix) stores the item 330. However, if you need to add an item with a prefix longer than N / 4 on average, you must make more than N / 4 moves to make room for the required space.

4 is a diagram illustrating an additional method in the case of adding data having a prefix length n of the present invention.

That is, when data of length n is added, items 410 having a prefix of length N / 2-1 to items 420 having a length of length n-1 are sequentially moved in the lower address direction. After that, a prefix item 430 of length n is stored.

The present invention places the blank area 440 at a lower address when the prefix length of the added item is larger than N / 4 on average, and moves the data toward the lower address, and then adds the prefix length. By recording the additional data in the region with the average, the number of times of shifting the content addressable memory (CAM) lookup data is reduced, thereby reducing the data update time as a whole.

5 is a configuration diagram of a forwarding table management apparatus of the present invention.

The forwarding table management apparatus 500 of the present invention has an interface with a pointer storage unit 510 and a central processing unit (CPU) 520 that store N pointers, and has a pointer and a content addressable memory (CAM). A content addressable memory (CAM) control unit 550 having an interface with a table management unit 530, a table management unit, and a pointer storage unit that controls the control unit, and controlling the content addressable memory (CAM) table storage unit 540; It consists of.

The table manager 530 receives the data addition command from the CPU 520, controls the N pointers stored in the pointer storage 510, and drives the content addressable memory (CAM) controller 550. To update the content addressable memory (CAM) table in the content addressable memory (CAM) table storage unit 540.

The pointer storage unit 510 stores a pointer having position data of a content addressable memory (CAM) table, which is an upper pointer UP (0) having a prefix length of 0 and a lower pointer LP (0). N pointers from two pairs of pointers to two pairs of pointers UP (N / 2-1) and lower pointers LP (N / 2-1) having a prefix length N / 2-1. The lower pointer among the N pointers indicates the next data of the data having the lowest address among the data having the same prefix length, and the upper pointer indicates the data having the highest address among the data having the same prefix length.

The content addressable memory (CAM) control unit 550 retrieves data by driving the content addressable memory (CAM) table storage unit 540 by receiving a control command from the table manager 530 and the pointer storage unit 510. And read and write commands.

FIG. 6 is a diagram showing the content addressable memory (CAM) storage status and pointer representation of data with prefix length i.

610 of FIG. 6 is a band of data having a prefix of length i, in which the data having a prefix of length i is stored out of order, and 620 is a length. A band of data with a prefix of i-1, in which the data with a prefix of length i-1 is also stored out of order.

The lower pointer LP (i) points to the next data of the lowest address among the address areas of the data stored in the band 610 of the data having the prefix of length i, and the address of the data stored in the band 610 of the data. UP (i), the upper pointer, points to the data of the highest address in the region. Therefore, LP (i-1), which is a lower pointer of a band of data having a prefix of length i-1, indicates the same data as UP (i) and of a data having a prefix of length i + 1. UP (i + 1), the upper pointer of the band, indicates the same data as LP (i). Here, the pointer points to the data, which means that the pointer stores the address of the data.

FIG. 7 is a diagram of a storage state in a content addressable memory (CAM) in the presence of data of length 0 to 32 prefix.

That is, an example in which the band of such data has N / 2-1 of 32 and all band data exists. Prefix length 0 band data is data used when there is no prefix matching the default data, and usually has one data.

8 is a flowchart illustrating a process of adding data to a content addressable memory (CAM) table of the present invention.

When the table manager 530 receives a data addition command from the CPU 520, the table manager 530 sends a data retrieval command to the content addressable memory (CAM) controller 550. The content addressable memory (CAM) control unit 550 searches the lookup table of the content addressable memory (CAM) table storage unit 540 to search whether there is corresponding data (820). If the corresponding data does not exist as a result of the search, the table manager 530 drives the content addressable memory (CAM) control unit 550 to allow content addressing in the content addressable memory (CAM) table storage unit 540. Adjust the memory (CAM) table (830), update the pointer data (address stored by the pointer) included in the pointer storage unit 510, and let the content addressable memory (CAM) control unit 550 add it. The data is stored in the content addressable memory (CAM) table storage unit 540 (840).

A process of adding data to a content addressable memory (CAM) table will now be described in detail with reference to FIGS. 9 and 10.

9 is a diagram showing a storage state and a pointer in a content addressable memory (CAM) of data having a prefix length of N / 2-1.

When the table management unit receives a command to add data from the CPU, the band of data having a prefix of length N / 2-1 is located at a low address of the content addressable memory (CAM) and thus UP (N / 2). -1) move the data to LP (N / 2-1), i.e., read the data pointed to by UP (N / 2-1) and write it to the space pointed to by LP (N / 2-1) (910), The data space of (N / 2-1), that is, LP (N / 2-2), becomes empty. If UP (N / 2-2) data is moved to this space (920), the data space of UP (N / 2-2) or LP (N / 2-3) becomes empty, and if data is moved sequentially The table update is completed by adding data to LP (i) of a prefix data space of length i that should be.

FIG. 10 is a diagram illustrating an additional process when prefix data of length 0 is added when prefix data of lengths 2 and 1 are stored.

Moving from length 32 prefix data to moving length 2 prefix data into a length 3 prefix data band (1010) and length 1 prefix data to length 2 prefix data The band moves to a band (1020) and inputs prefix data of length 0 to be added to an empty space of the prefix data of length 1 (1030).

Meanwhile, the above-described embodiments of the present invention can be written as a program that can be executed in a computer, and can be implemented in a general-purpose digital computer that operates the program using a computer-readable recording medium.

The computer-readable recording medium may be a magnetic storage medium (for example, a ROM, a floppy disk, a hard disk, etc.), an optical reading medium (for example, a CD-ROM, DVD, etc.) and a carrier wave (for example, the Internet). Storage medium).

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

As described above, the present invention has the effect of reducing the number of movements of the prefix length data and reducing the data update time as a whole when the average length of the added data is larger than N / 4. . Therefore, when updating a lot of data, there is an advantage that can update the entire data in a short time.

Claims (6)

(a) a lower pointer for storing the next address information of the data having the lowest address among the data included in the band for each data band in which data having a predetermined prefix length is stored; and data having the highest address among data having the same prefix length. Providing an upper pointer storing address information of the apparatus; (b) When data is added to a Content Addressable Memory (CAM) lookup table, for each band of data having a prefix length exceeding the prefix length of the data to be added, an address stored by the upper pointer of each band Recording the data at an address stored by the lower pointer of each band; And (c) content addressable using Longest Prefix Matching (LPM) comprising storing data to be added at an address stored by a lower pointer to a band of data having a prefix length equal to the prefix length of the data to be added. How to manage lookup tables in memory (CAM). The method of claim 1, wherein step (b) (b1) receiving a command to add data to the content addressable memory (CAM) lookup table; And (b2) For each band of data having a value greater than the prefix length of the data to be added to provide space for recording the data to be added, the lower pointer of each band contains data of an address stored by the upper pointer of each band. A method of managing a lookup table of content addressable memory (CAM) using Longest Prefix Matching (LPM), the method comprising storing at a memorable address. The method of claim 1, wherein the LPM is A method of managing a content addressable memory (CAM) lookup table using Longest Prefix Matching (LPM), characterized by storing long prefix data from a lower address. A content addressable memory (CAM) including a lookup table for storing data having a long prefix length from a low address; A lower pointer that stores the next address of the data having the lowest address among data having the same prefix length for each band of data having a predetermined prefix length, and an upper memory storing the address of the data having the highest address among the data having the predetermined prefix length. A pointer storage unit including a pointer; And When data is added to the lookup table of the content addressable memory (CAM), for each band of data having a prefix length exceeding the prefix length of the data to be added, the data of the address stored by the upper pointer of each band Is recorded at an address stored by the lower pointer of each band, data to be added to an address stored by a lower pointer to a band of data having the same length as the prefix length of the data to be added, and is stored in the pointer storage unit. A content addressable memory (CAM) lookup table management apparatus using Longest Prefix Matching (LPM) including a table management unit for updating an address stored by an upper pointer and a lower pointer included therein. The method of claim 4, wherein the table management unit When updating the address stored by the upper pointer and the lower pointer included in the pointer storage unit, the upper pointer and the lower pointer of the data band having the prefix length exceeding the prefix length of the data to be added are stored in the upper pointer and the lower pointer. And update the lower pointer of the data band having the prefix length equal to the prefix length of the data to be added to the lower address next to the address stored by the lower pointer. A content addressable memory (CAM) lookup table management device using Longest Prefix Matching (LPM). A computer-readable recording medium having recorded thereon a program for executing the method according to any one of claims 1 to 3.