JPH08212790A - Associative memory for retrieval of multiprotocol address and its retrieval method - Google Patents

Abstract

PURPOSE: To obtain an associative memory for retrieval of a multiprotocol address, in which a plurality of addresses of respectively different protocols can be retrieved by one associative memory table and a high speed and a low cost of the route control of a network can be realized at the same time and to obtain its retrieval method. CONSTITUTION: The associative memory is provided with an associative memory table 12 comprising a plurality of entries composed of a plurality of segments in a prescribed bit length and with a selection means 16 for a sequencer 14 which controls an agreement retrieval procedure at every protocol. At least a protocol identifier and a protocol address are stored in every entry, and the entry which agrees with a protocol identifier is detected. Then, the sequencer 14 which corresponds to the prescribed protocol identifier is selected by the selection means 16, and the agreement of the logical product of the protocol address in units of segments is retrieved by the sequencer 14 selected in the detected entry.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an associative memory for multi-protocol address search and a search method therefor. The present invention relates to a multi-protocol address search associative memory that can be searched by performing high-speed and low-cost route control, and a search method therefor.

[0002]

2. Description of the Related Art An associative memory (CAM) is also called a content addressable memory, and has a storage unit for storing data like an ordinary semiconductor memory and a search unit for searching data stored in this storage unit. Have The data to be searched is stored in advance in the storage unit, and the search unit performs a match search between the data stored in the storage unit and the data to be searched. It is searched and output in a single cycle. By using the associative memory, the target data can be instantly obtained from a huge amount of data, and thus it is used for improving the performance of a system that frequently performs search processing.

An application example of the associative memory described above will now be described by taking the route control of the network as an example.
First, an outline of the network will be described.

Data communication is performed between computers connected to the network using a specific data communication protocol (hereinafter, simply referred to as protocol). As such a protocol, for example, IP (Internet P
rotocol), IPX (Internetwork Packet Exchange,
There are many types such as Novel Netware), DECNet, AppleTalk, etc., and the bit length, data storage order, storage location, etc. are generally different for each protocol. Routers are also used to interconnect different networks, and some are capable of routing multiple protocols. This is called a multi-protocol router.

Each protocol assigns a protocol address (address of the protocol: hereinafter simply referred to as address) as an identifier to all computers existing on the network. This uniquely identifies each computer. However, a multi-protocol router cannot uniquely identify a computer by its address. This is because if one protocol and another different protocol assign the same address to different computers, the computer cannot be uniquely identified only by the address assigned by each protocol. is there. For example, when transferring data from the computer 3 to the computer 1 in FIG. 9, the router cannot identify whether to send the data to the computer 1 or the computer 2 only from the destination address 1234.

To solve this problem, a normal LAN is used.
The (Local Area Network) frame includes an identifier for identifying a higher level protocol. The router determines the destination by combining the protocol identifier and the address. An Ethernet frame will be described as an example of such a LAN frame.

FIG. 6 is a conceptual diagram of an Ethernet frame which is one of LANs. Although this frame is conceptual and different from the actual one, the transfer destination and transfer source addresses DA and S of this Ethernet frame
A and the protocol type TYP of the existing protocol,
It is composed of an existing protocol datagram and a communication error detection data CRC. Also, the datagram of the existing protocol is the source and destination addresses sa and da of the datagram of the existing protocol.
And data to be communicated.

Next, communication via the router will be described. Here, FIG. 7A is a conceptual diagram of network connection using a router, FIG. 7B is a conceptual diagram of an Ethernet frame input from the computer A to the router R, and FIG.
(C) is a conceptual diagram of an Ethernet frame output from the router R to the computer B. Note that the MAC (Media Access Control) addresses (Ethernet addresses) of the computers A and B and the addresses of existing protocols are GA, GB and LA, LB, respectively, and the MAC address of the router R is GR, and the following description is continued. .

As shown in FIG. 7A, an Ethernet frame of various protocols is input to the router R that transfers data, and the transfer destination is determined in the router R according to each protocol. Each frame is output from the router R to each communication destination. For example, when transmitting data from the computer A to the computer B, a frame of the protocol used by the computer A is input to the router R, and the transfer destination is determined in the router R according to the protocol used by the computer A.
As a result, the frame is output from the router R to the computer B.

As shown in FIG. 7B, the computer A
The Ethernet frame transferred from the router R to the router R includes the transfer destination and transfer source addresses GR of this frame.
And GA and protocol type T for existing protocols
Includes YP and existing protocol datagrams.
Moreover, the datagram of the existing protocol includes the addresses LA and LB of the communication source and the communication destination, and the data data to be communicated. This Ethernet frame means that a frame of an existing protocol of the protocol type TYP is transferred from the transfer source address GA of the Ethernet to the transfer destination address GR, that is, from the computer A to the router R.

When this Ethernet frame is input to the router R, the router R receives the protocol types TYPE and L.
The transfer destination is determined from B. That is, the router searches the address LB of the computer B in its own table,
By knowing the MAC address of the computer B and which network it is connected to, the Ethernet frame shown in FIG. 7C is sent to the network to which the computer B is connected. That is, GR is GB, GA is
Is converted to GR.

As shown in FIG. 7C, the Ethernet frame transferred from the router R to the computer B is
The transfer destination and transfer source addresses GB and GR of this frame, and the protocol type TYP of the existing protocol
And contains the datagram of the existing protocol. Moreover, the datagram of the existing protocol includes the addresses LA and LB of the communication source and the communication destination, and the data data to be communicated. This Ethernet frame means that an existing protocol frame of the protocol type TYP is transferred from the Ethernet transfer source address GR to the transfer destination address GB, that is, from the router R to the computer B.

In this way, the router R correctly determines the transmission destination, so that even if frames of different protocols are mixed on a plurality of networks, each computer can be uniquely identified. , Can be interconnected for data communication. The multi-protocol router prepares a separate address lookup table for each protocol. When the CAM is used for the table, the CAM chip is assigned for each protocol.

Finally, an example of application of the associative memory to the address search performed when the router determines the transmission destination will be described. In the address search by the router R described above,
The associative memory is the address L of the communication destination of the existing protocol.
B to Ethernet frame transfer destination address G
Used to get B.

FIG. 8 is a schematic diagram of an example of application of an associative memory to a conventional network address search. In the figure, each associative memory has a one-to-one correspondence with all the protocols used in this network, and each associative memory has the address of the corresponding protocol in advance for all computers connected to the network. Remembered. When the Ethernet frame corresponding to each protocol is input to the router R, the router R selects the associative memory corresponding to the protocol type TYP, and the address LB of the communication destination of the existing protocol is used in the associative memory. The search is performed, and the address GB of the communication destination of Ethernet can be obtained at high speed.

In the above-described application example of the associative memory to the address search, the destination address search can be performed at high speed. However, in conventional associative memory, datagrams of different protocols, especially their bit length,
Since it is not possible to retrieve address data with different storage order in one associative memory, it is necessary to use different associative memories for each protocol. For this reason,
There is a problem that the number of associative memories to be used increases and the cost increases. On the other hand, in order to reduce the cost, if the search is performed by software without using the associative memory, the search by software takes a long time.

[0017]

SUMMARY OF THE INVENTION The object of the present invention is to detect various entries based on the above-mentioned prior art, to detect an entry in which a predetermined protocol identifier is stored, and to control a sequencer based on the predetermined protocol identifier. By selecting and using this sequencer, an entry in which a predetermined protocol address is stored is detected from the entries detected by the predetermined protocol identifier, and a plurality of addresses of different protocols are searched in one associative memory table. (EN) Provided is a multi-protocol address search associative memory and a search method therefor capable of simultaneously realizing high-speed and low-cost route control of a network.

[0018]

In order to achieve the above object, the present invention controls an associative memory table having a plurality of entries each consisting of a plurality of segments having a predetermined bit length, and a matching search procedure for each protocol. Selecting means of a sequencer for performing at least a protocol identifier and a protocol address are stored in the entry, an entry matching the predetermined protocol identifier is detected, and a sequencer corresponding to the predetermined protocol identifier is selected by the selecting means. An associative memory for multi-protocol address search is provided in which the logical product coincidence search of the protocol address in the segment unit is performed by the selected sequencer in the detected entry.

Further, it is preferable that the sequencer is provided for each protocol.

Further, according to the present invention, the protocol identifier and the protocol address corresponding to each protocol are stored in advance in different segments of the respective entries, and then the segment in which the protocol identifier is stored is searched for a match to perform the predetermined search. Detecting the entry in which a protocol identifier is stored and obtaining a sequencer identifier based on the predetermined protocol identifier,
Next, a sequencer corresponding to the predetermined protocol identifier is selected by the sequencer identifier, and then, according to the control of the selected sequencer, the segment of the segment in which the protocol address of the entry detected as a match by the predetermined protocol identifier is stored. A method for searching a multi-protocol address, which comprises performing a match search and detecting the entry in which the predetermined protocol address is stored.

Here, after the sequencer identifier corresponding to the protocol identifier is stored in a part of the segment in advance, the sequencer identifier stored in a part of the segment of the entry whose match is detected by the predetermined protocol identifier is stored. Preferably obtained.

Further, it is preferable that the sequencer identifier is obtained by decoding the predetermined protocol identifier.

[0023]

The associative memory for multi-protocol address search according to the present invention comprises a sequencer selecting means and a sequencer corresponding to each protocol. As described above, each protocol address has a different bit length, storage position, etc.
The P address and the IPX address cannot be searched by the same search procedure. Therefore, in the present invention,
By providing a sequencer selection means such as a lookup table with ROM, RAM, and registers, and a decoding circuit, a sequencer is selected according to each protocol, and an address of the protocol is searched according to each protocol. You can Therefore, according to the associative memory for multi-protocol address search of the present invention, addresses of a plurality of different protocols can be stored in one associative memory table, and an entry having a predetermined address of a predetermined protocol can be detected from these. it can.

Further, in the multi-protocol address search method of the present invention, the protocol identifier and the protocol address are stored in different segments of each entry, and first, the segment in which the protocol identifier is stored is searched to determine a predetermined value. Detects the entry in which the protocol identifier is stored, obtains the sequencer identifier from this predetermined protocol identifier, selects the sequencer corresponding to this protocol by this sequencer identifier, and then detects by the predetermined protocol identifier according to this sequencer The segment storing the protocol address of the stored entry is searched to detect the entry storing the predetermined protocol address. Therefore, according to the multi-protocol address search method of the present invention, it is possible to recognize which protocol address each protocol address is from by the protocol identifier, so that addresses of a plurality of different protocols are stored in one associative memory. Then, these can be searched by the protocol identifier and the protocol address. As a result, the route control of the network can be performed at high speed, and the system can be constructed at low cost.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The associative memory for multi-protocol address retrieval of the present invention and its retrieval method will be described in detail below with reference to the preferred embodiments shown in the accompanying drawings.

FIG. 1 is a block diagram of an embodiment of the associative memory for multi-protocol address search according to the present invention. As shown in this block diagram, a multi-protocol address search associative memory 10 of the present invention stores an entry data corresponding to each protocol, and an associative memory table 12 for performing a match search between the entry data and the search data. , A sequencer (group) 14 which is provided for each protocol and controls the procedure for searching entry data 14
And sequencer selecting means 16 for selecting the sequencer 14 according to the protocol.

FIG. 2 is a conceptual diagram of an embodiment of the associative memory table described above. The associative memory table 12 is made up of entries 0, 1, ..., M, and each entry 0 to m has, for example, an IP entry and an IP.
Data such as X entries, DECNet entries and AppleTalk entries are stored in any order. Also, each entry 0 to m is divided into segments 0, 1, ... The segments 0 to n may have the same bit length or different bit lengths, and the bit length is not particularly limited.

Next, FIG. 3 is a conceptual diagram of an embodiment of an entry of the associative memory table shown in FIG. A segment 0 of the entry stores a protocol ID (identifier) and a sequencer ID, and segments 1 to n store a protocol address corresponding to the protocol ID. The bit length of each segment 0 to n is
It is about 32 to 64 bits. For example, segment 1
If the bit length of n is 32 bits, segments 1 to
In the case of an IP entry, the protocol address stored in n is stored only in segment 1 because the IP address is 32 bits. Similarly, for an IPX entry,
Since the IPX address is 80 bits, segment 1,
Up to 16 bits of 2 and segment 3 are stored.
In this way, the number of segments is appropriately selected according to the bit length of the segment and the bit length of the protocol address.

Here, FIG. 4 shows a specific example of the protocol ID and sequencer ID stored in the segment 0. In the figure, in order to facilitate the explanation, the protocol corresponding to which data is
It is shown as a comment like PX. Further, the protocol ID is shown according to the Ethernet standard. The sequencer ID is a number for selecting a sequencer corresponding to the protocol ID, and is a number corresponding to each protocol on a one-to-one basis. As an example, in the case of IP, the protocol ID is 0800 (16
The sequencer ID for this is number 1. In the example shown in this figure, segment 0 is 1
It has a 19-bit size of a 6-bit length protocol ID and a 3-bit length sequencer ID.

Next, referring to the schematic diagram of the associative memory table shown in FIG. 5, in the associative memory of the present invention configured as described above and storing the entry data corresponding to a plurality of different protocols, A method of searching for an entry in which an address is stored will be described. The associative memory table shown in FIG.
1, ..., 4 and each entry 0, 1,
..., 4 are divided into segments 0, 1, ..., 4.

First, in the first search, in segment 0 of all entries 0 to 4 of this associative memory table, a match search is performed while masking the sequencer ID, and an entry storing a predetermined protocol ID is detected. To be done. For example, when 0800 (hexadecimal number) is given as the search data as in the example shown in FIG. 4, only the entry in which the protocol ID of segment 0 stores 0800 (hexadecimal number) is detected as a match. As a result, it is assumed here that a match is detected in entries 0, 2 and 3 and a mismatch is detected in entries 1 and 4.

After that, the sequencer ID stored in the segment 0 of the entry 0, 2 or 3 in which the match is detected by the predetermined protocol ID is read out. For example, in the example shown in FIG. 4, the protocol ID is 0800 (hexadecimal number). Sequencer ID stored in an entry, that is,
The number 1 is read and the sequencer is selected according to this sequencer ID. When the sequencer is selected, the procedure for searching the protocol addresses in the segments 1 to 4 of the entries 0, 2 and 3 which are detected to match by the predetermined protocol ID is controlled by the selected sequencer.

Now, the sequencer described above will be described. As described above, the protocol addresses stored in the segments 1 to n of the respective entries have different bit lengths, storage order, etc. when the protocols are different. Therefore, it is necessary to change the search procedure in the segments 1 to n according to the protocol to be searched. The sequencer controls this search procedure. The sequencer may be provided inside or outside the associative memory on a one-to-one basis with respect to the protocol used in the network.

Next, in the second search, a match search is performed in the segments 1 of the entries 0, 2 and 3 which are found to match in the segment 0 by the predetermined protocol ID in the first search, and the first search of the predetermined protocol address is performed. An entry in which data for one segment is stored is detected. It should be noted that no match search is performed on the segment 1 of the entries 1 and 4 in which the mismatch is detected. Two
As a result of the second search, it is assumed here that a match is detected in entries 0 and 3 and a mismatch is detected in entry 2.

In the third search, the match detection is performed in the segment 2 of the entries 0 and 3 in which the match is detected by the data of the first segment of the predetermined protocol address in the segment 1 in the second search. The entry in which the data for the second segment of the protocol address is stored is detected. Note that no match search is performed on segment 2 of entry 2 for which no match was detected on segment 1.
As a result of the third search, it is assumed here that a match is detected in entry 3 and a mismatch is detected in entry 0. Therefore, it is detected that the predetermined protocol ID and the predetermined protocol address are stored in the entry 3. By performing the logical product search in this way, an efficient search is performed.

For example, in the case of an IP entry, since the IP address is 32 bits (1 segment), the IP sequencer searches the segment 1 of the entry in which the match is detected by the predetermined protocol ID, and the predetermined protocol address is stored. Detected entries. As described above, in the case of the IP entry, the entry in which the predetermined protocol ID and the predetermined protocol address are stored can be detected by performing the logical product search of the segments 0 and 1.

On the other hand, in the case of an IPX entry, the IPX address is 80 bits (3 segments (2 segments + 16
Bit)), the IPX sequencer
The segment 1 of the entry in which the match is detected by the predetermined protocol ID is searched, and the entry in which the data for the first one segment of the predetermined protocol address is stored is detected. Search for segment 2 of the entry found to match by the data of one segment of
The entry in which the data for the second one segment of the predetermined protocol address is stored is detected, and the segment 3 of the entry in which the match is detected by the data for the second one segment of the predetermined protocol address is also detected in segment 2. A search is performed by masking the latter half 16 bits, and an entry in which 16 bits of data of the third one segment of a predetermined protocol address is stored is detected. As described above, in the case of the IPX entry, the predetermined protocol I is obtained by performing the logical product search of the segments 0 to 3.
The entry in which D and the predetermined protocol address are stored can be detected.

The multi-protocol address search associative memory and the search method thereof according to the present invention are basically configured as described above. Although the associative memory for multi-protocol address search and the search method thereof according to the present invention have been described based on the embodiments, the present invention is not limited to this.

For example, in the above-described embodiment, the protocol ID and the sequencer ID are stored in the segment 0 of each entry, but it is not limited to the segment 0 and may be stored in any segment. That is, 1
In the second search, the segment in which the protocol ID is stored may be searched. As the sequencer selection means of the present invention, the sequencer ID is stored in the segment 0, and the sequencer ID corresponding to this one-to-one is acquired from the predetermined protocol ID. However, the sequencer ID may be acquired by decoding a predetermined protocol ID, for example. In this case, in the entry of FIG.
The sequencer identifier part is unnecessary. Similarly, the sequencer ID may be stored not in the associative memory table but in another memory device, for example, a register, a RAM, a ROM, etc., and these memory devices and the above-mentioned decoding circuit etc. It may be provided inside or outside the associative memory. Furthermore, each entry must contain at least the protocol ID or sequencer ID.
Although the protocol address is stored, data other than these data may be stored.

[0040]

As described in detail above, the associative memory for multi-protocol address retrieval of the present invention has a sequencer selection means for controlling the protocol address retrieval procedure according to each protocol. Further, the method of searching a multi-protocol address of the present invention
After storing the protocol ID and the protocol address in different segments in each entry of the associative memory table in advance, first, the segment in which the protocol ID is stored is searched to detect the entry in which the predetermined protocol ID is stored. At the same time, a sequencer is selected based on this predetermined protocol ID, and subsequently,
The selected sequencer searches the segment in which the protocol address of the entry detected by the predetermined protocol ID is stored, and detects the entry in which the predetermined protocol address is stored. That is, according to the associative memory for multi-protocol address search and the searching method thereof of the present invention, a plurality of different protocol addresses can be searched by one associative memory.
It is possible to control the network route at high speed, and at the same time, it is possible to realize cost reduction.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of an associative memory for multi-protocol address search according to the present invention.

FIG. 2 is a conceptual diagram of an embodiment of an associative memory table in the associative memory for multi-protocol address search according to the present invention.

FIG. 3 is a conceptual diagram of an embodiment of an entry of an associative memory table in the associative memory for multi-protocol address search of the present invention.

FIG. 4 is a conceptual diagram of an embodiment of segment 0 of an entry of an associative memory table in the associative memory for multiprotocol address search of the present invention.

FIG. 5 is a conceptual diagram of an embodiment for explaining a multi-protocol address search method of the present invention.

FIG. 6 is a conceptual diagram of an Ethernet frame.

7A is a conceptual diagram of network connection using a router, FIG. 7B is a conceptual diagram of an Ethernet frame input from a computer A to a router R, and FIG. 7C is a router R.
3 is a conceptual diagram of an Ethernet frame output from the computer to the computer B. FIG.

FIG. 8 is a schematic diagram of an example of application of an associative memory to address search of a conventional network.

FIG. 9 is a conceptual diagram of network connection using a conventional router.

[Explanation of symbols]

 1, 2 and 3 computer 10 associative memory (CAM) 12 associative memory table 14 sequencer 16 sequencer selection means

Claims (5)

[Claims] 1. An associative memory table having a plurality of entries each consisting of a plurality of segments having a predetermined bit length, and a sequencer selecting means for controlling a procedure of matching search for each protocol, wherein at least a protocol identifier is provided in the entry. And a protocol address are stored, an entry that matches the predetermined protocol identifier is detected, and a sequencer corresponding to the predetermined protocol identifier is selected by the selecting means, and the selected sequencer in the detected entry An associative memory for multi-protocol address search, wherein a logical product coincidence search of the protocol addresses in segment units is performed. 2. The associative memory for multi-protocol address search according to claim 1, further comprising the sequencer for each of the protocols. 3. A protocol identifier and a protocol address according to each protocol are stored in advance in different segments of each entry, and then a matching search is performed on the segment in which the protocol identifier is stored, and the predetermined protocol identifier is stored. Detected the entry and obtains a sequencer identifier based on the predetermined protocol identifier, then selects a sequencer corresponding to the predetermined protocol identifier by the sequencer identifier, and then controls the selected sequencer. According to the above, a segment matching search is performed on a segment storing the protocol address of the entry detected to match by the predetermined protocol identifier, and the entry storing the predetermined protocol address is detected. Search method of multi-protocol address. 4. The sequencer identifier corresponding to the protocol identifier is stored in a part of the segment in advance, and then the sequencer identifier stored in a part of the segment of the entry whose match is detected by the predetermined protocol identifier is obtained. The method of searching a multi-protocol address according to claim 3. 5. The sequencer identifier is obtained by decoding the predetermined protocol identifier.
Multi-protocol address search method described in.