KR20030097487A - CAM lookup table management method based on LPM. - Google Patents

Abstract

PURPOSE: A method and device for managing a contents addressable memory lookup table based on an LPM(Longest Prefix Matching) being used in an IPv4 is provided to reduce data updating time generally by locating an empty area between an area the prefix length thereof is 23-bit and 24-bit instead of the prefix length of '0' or '32' in a lookup table of an IPv4. CONSTITUTION: A pointer storage(510) stores sixty six pointers. A table managing unit(530) interfaces with a CPU(520) and controls pointers and a CAM(Contents Addressable Memory) control unit(550). The CAM control unit(550) interfaces with the table managing unit(530) and the pointer storage(510), and controls a CAM table storage(540). The table managing unit(530) receives a data appending command from the CPU(520), controls a pointer stored in the pointer storage(510), operates the CAM control unit(550), and updates the CAM table storage(540). The pointer storage(510) stores a pointer having position data of a CAM table, and stores two pairs of upper pointer and lower pointer the prefix lengths. The CAM control unit(550) receives a control command from the table managing unit(530) and the pointer storage(510), operates a CAM, and executes a retrieving command, a reading command, and a writing command.

Description

CAM lookup table management method based on LPM based on LPM-based content addressable memory (CAM) lookup table used in IP4

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 16 on average needs to be added, there is a problem that more than 16 moves must be made in order to secure a necessary space. .

In addition, another method may be implemented by using a content addressable memory (CAM) in order of data having a long prefix from a high address to a low address. In other words, it is a way to leave a blank area in the low address area. However, even in this case, when an item having a prefix shorter than 16 is to be added on average, there is a problem in that necessary space must be moved several times.

In order to solve the above problem, in the present invention, in the IPv4 lookup table, a blank area is located between a 23-bit and a 24-bit area without having an empty area in an area having a prefix length of 0 or an area of 32. It aims to provide a way to reduce the data update time as a whole.

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

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

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

Fig. 4 is a diagram of a data storage state in a content addressable memory (CAM) in the presence of prefix data of prefix bits 0 to 32 bits of the present invention.

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

Fig. 6 is a diagram showing a CAM storage state and a pointer of i-bit data when the prefix length is 24 bits or more.

Fig. 7 is a diagram showing a CAM storage state and a pointer of i-bit data when the prefix length is less than 24 bits.

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 illustrating the addition of a CAM table of data when the prefix length is 24 bits or more.

Fig. 10 is a diagram illustrating the addition of a CAM table of data when the prefix length is less than 24 bits.

To achieve the above object, the present invention provides a method of providing a content addressable memory (CAM) lookup table having a lower pointer and an upper pointer indicating data area information having a predetermined prefix length; Receiving a command to add data to the content addressable memory (CAM) lookup table and comparing a prefix length and a predetermined value of the data to be added; As a result of the above step, if the prefix length of the data to be added is greater than or equal to a predetermined value, the address data stored by the lower pointer of each data band is sequentially moved to the address data area stored by the upper pointer of each data band. step; And as a result of the step, if the prefix length of the data to be added is less than a predetermined value, the address data stored by the upper pointer of each data band is sequentially moved to the address data area stored by the lower pointer of each data band. A method of managing a content addressable memory (CAM) lookup table using Longest Prefix Matching (LPM), the method comprising:

Providing a content addressable memory (CAM) lookup table having a lower pointer representing data area information having the predetermined prefix length and an upper pointer may store a plurality of address data having a prefix equal to or greater than a predetermined prefix length. For each data band, a lower pointer storing address information of data having the lowest address among a plurality of address data having the same prefix length stored in the data band, and an address among the plurality of address data having the same prefix length stored in the data band Providing a content addressable memory (CAM) lookup table having an upper pointer storing address information next to the highest data; A lower pointer storing next address information of data having the lowest address among a plurality of address data having the same prefix length stored in the data band for each data band in which a plurality of address data having a prefix less than a predetermined prefix length are stored; And providing a content addressable memory (CAM) lookup table having an upper pointer storing address information of data having the highest address among a plurality of address data having the same prefix length stored in the data band. desirable.

In order to achieve the above object, the present invention provides a memory device including: a content addressable memory (CAM) including a lookup table for storing data from a low address or a high address according to a prefix length; A pointer storage unit including a lower pointer and an upper pointer for storing boundary data of a data band region having a predetermined prefix length; And a command for adding data to the data band to control an upper pointer and a lower pointer stored in the pointer storage unit, and to drive the content addressable memory (CAM) controller to control a content addressable memory (CAM) table. Provided is a content addressable memory (CAM) lookup table management apparatus using Longest Prefix Matching (LPM), including a table management unit for updating a network.

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 general forwarding engine for routing performed in a 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 general lookup table.

The general 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.

FIG. 4 is a diagram illustrating a data storage state in a content addressable memory (CAM) when there is prefix data having a prefix length of 0 bits to 32 bits.

That is, in the IPv4 lookup table, the data update time is reduced overall by placing the free area between the 23-bit and 24-bit regions of the prefix length rather than the region having the prefix length of 0 bits.

5 is a block diagram of a table management device of the present invention.

The table management apparatus 500 of the present invention has an interface with a pointer storage unit 510, a central processing unit (CPU) 520, which stores 66 pointers, and a pointer and a content addressable memory (CAM). To the content addressable memory (CAM) control unit 550 having an interface with the table management unit 530, the table management unit and the pointer storage unit controlling the control unit, and controlling the content addressable memory (CAM) table storage unit 540. It is composed.

The table manager 530 receives a data addition command from the CPU 520, controls a pointer stored in the pointer storage 510, and drives a content addressable memory (CAM) controller 550 to control content. Update the addressable memory (CAM) table 540.

The pointer storage unit 510 stores a pointer having position data of a content addressable memory (CAM) table, and includes two pointers, an upper pointer UP (0) and a lower pointer LP (0) having a prefix length of 0 bits. 66 pointers are stored from the pair of pointers to the two pairs of pointers 32 of the prefix length 32 bits of the upper pointer UP 32 and the lower pointer LP 32.

The content addressable memory (CAM) control unit 550 receives a control command from the table manager 530 and the pointer storage unit 510 to drive the content addressable memory (CAM) to search for, read, and write data. Do this.

FIG. 6 is a diagram illustrating a CAM storage state and a pointer of i-bit data when the prefix length is 24 bits or more.

That is, among the 66 pointers, upper and lower pointers having a prefix length of 24 bits or more have address data as shown in FIG. 6. That is, the lower pointer refers to the data having the lowest address among the data having the same prefix length, and the upper pointer refers to the data following the data having the highest address among the data having the same prefix length. In FIG. 6, 610 is a band of data having a prefix of length i bits, and 620 is a band of data having a prefix of length i-1 bits.

7 is a diagram showing the CAM storage state and pointer of i-bit data when the prefix length is less than 24 bits.

That is, upper and lower pointers having a remaining prefix length of less than 24 bits have address data as shown in FIG. 7. The lower pointer points to the next data of the data having the lowest address among the data having the same prefix length, and the upper pointer points to the data having the highest address among the data having the same prefix length. In FIG. 7, 710 is a band of data having a prefix of length i bits, and 720 is a band of data having a prefix of length i-1 bits. Band data of length 0 bits is used when there is no prefix that matches 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.

First, an upper pointer and a lower pointer required for data addition are initialized (810).

In operation 830, a command for adding data to the content addressable memory (CAM) lookup table is received, and a prefix length of the data to be added is determined (830). If the prefix length of the data to be added is 24 or more, the address data stored by the lower pointer of each data band is stored in the address data area stored by the upper pointer of each data band, and the upper and lower pointers are adjusted. (840).

When the prefix length of the address data to be added is less than 24, the address data stored by the upper pointer of each data band is stored in the address data area stored by the lower pointer of each data band, and the upper pointer and lower Adjust the pointer (850).

If an empty area is created in this manner, data is added to the area (860). If there is data to be added (870), if there is data to be added, it goes back to the beginning and waits for a data adding command.

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.

FIG. 9 is a diagram for adding a CAM table of data when the prefix length is 24 bits or more. FIG.

When the table manager 530 receives a data addition command from the CPU 520, the prefix bit length information of the data to be added is compared with 24 to add to the lower address of an empty area and to be less than 24. Enter in the upper address. If the prefix bit length of the data to be added is 24 or more, the data of the LP 24 is transferred to the UP 24 because the band of the data having the 24-bit prefix is located at a low address of an empty area. Moving it (ie, reading the data pointed to by LP 24 and writing it to the space pointed by UP 24) 910, the data space of UP 25, or LP 24, becomes empty. Therefore, if the data of the LP 25 is moved to this space (920), the data space of the UP (26), that is, the LP (25) becomes empty, and i-prefix data of length i bits to be moved and added sequentially. The table update is completed by adding data to UP (i) of the space.

FIG. 10 is an additional diagram of a CAM table of data when the prefix length is less than 24 bits. FIG.

If the prefix bit length of the data to be added is less than 24 bits, since the band of data having a 23-bit prefix is at a low address of an empty area, the data of the UP 23 is stored in LP ( 23) (i.e., reading the data pointed by the UP 23 and writing it to the space pointed by the LP 23) 1010, the data space of the UP 23 or LP 22 becomes empty. Therefore, if the data of the UP 22 is moved to this space (1020), the data space of the UP 22, that is, the LP 21 becomes empty, and i-prefix data of length i bits to be moved and added sequentially. The table update is completed by adding data to the LP (i) of the space.

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 an effect of reducing the number of shifts of the prefix length data and reducing the data update time as a whole when the prefix length distribution of the additional data is divided into 24 bits. . Therefore, when updating a lot of data, there is an advantage that can update the entire data in a short time.

Claims (8)

(a) providing a content addressable memory (CAM) lookup table having a lower pointer representing data area information having a predetermined prefix length and an upper pointer; (b) receiving a command to add data to the content addressable memory (CAM) lookup table and comparing a prefix length and a predetermined value of the data to be added; (c) As a result of step (b), if the prefix length of the data to be added is greater than or equal to a predetermined value, the address data stored by the upper pointer of each data band stores the address data stored by the lower pointer of each data band. Sequentially moving to regions; And (d) If the prefix length of the data to be added is less than a predetermined value as a result of step (b), the address data stored by the lower pointer of each data band stores the address data stored by the upper pointer of each data band. A method of managing a content addressable memory (CAM) lookup table using Longest Prefix Matching (LPM), comprising sequentially moving to an area. The method of claim 1, wherein step (a) (a1) A data pointer having a prefix length equal to or greater than a predetermined value includes a lower pointer storing address information of data having the lowest address among a plurality of data having the same prefix length stored in the data band, and the prefix stored in the data band. Providing an upper pointer storing next address information of data having the highest address among a plurality of data having the same length; And (a2) In a data band having a prefix length less than a predetermined value, a lower pointer storing next address information of data having the lowest address among a plurality of data having the same prefix length stored in the data band, and stored in the data band. A content addressable memory (CAM) using Longest Prefix Matching (LPM), characterized by comprising an upper pointer storing address information of data having the highest address among a plurality of data having the same prefix length. How to manage lookup tables. The method according to claim 1 or 2, wherein the predetermined value is 24. A method of managing a content addressable memory (CAM) lookup table using Longest Prefix Matching (LPM), characterized in that: A content addressable memory (CAM) including a lookup table for storing data from a low address or from a high address according to a prefix length; A pointer storage unit including a lower pointer and an upper pointer for storing boundary data of a data band region having a predetermined prefix length; And A command to add data to the data band is used to control an upper pointer and a lower pointer stored in the pointer storage unit, and to drive the content addressable memory (CAM) control unit to generate a content addressable memory (CAM) table. A content addressable memory (CAM) lookup table management device using Longest Prefix Matching (LPM) including a table management unit for updating. The method of claim 4, wherein the pointer storage unit A data band having a prefix length equal to or greater than a predetermined value includes a lower pointer storing address information of data having the lowest address among a plurality of data having the same prefix length stored in the data band, and having the same prefix length stored in the data band. An upper pointer storing next address information of data having the highest address among the plurality of data; A data band having a prefix length less than a predetermined value includes a lower pointer storing next address information of data having the lowest address among a plurality of data having the same prefix length stored in the data band, and a prefix length stored in the data band. A content addressable memory (CAM) lookup table management apparatus using Longest Prefix Matching (LPM), characterized by having an upper pointer storing address information of data having the highest address among a plurality of data. The method of claim 4, wherein the table management unit If the prefix length of the data to be added is equal to or greater than a predetermined value, the address data stored by the lower pointer of each data band is sequentially moved to the address area stored by the upper pointer of each data band, and the prefix length of the data to be added When L is less than a predetermined value, Longest Prefix Matching (LPM) is used, which sequentially moves data of an address stored by an upper pointer of each data band to an address area stored by a lower pointer of each data band. A content addressable memory (CAM) lookup table management device. The method of claim 5 or 6, wherein the predetermined value is 24. A Content Addressable Memory (CAM) lookup table management device using Longest Prefix Matching (LPM), characterized in that the value of 24. A computer-readable recording medium having recorded thereon a program for executing the method according to any one of claims 1 to 3.