JPH02190048A - Address filter - Google Patents

Abstract

PURPOSE:To suppress the increase of time till the comparison processing end of an address filter in the case of increasing the number of terminal addresses by comparing a terminal address value with a destination address value in an address register in a way of applying a binary search in order to retrieve a registered terminal address whose value is closest to the destination address of a received data. CONSTITUTION:Terminal addresses to be compared with a destination address in a data received from a LAN(local area network) are stored in an address registration memory 1 in an ascending order. A destination address is set to an address register 2, an address comparison section 3 compares the terminal address of the address registration memory 1 with the destination address in the address register 2 and outputs the result to a memory address generating section 4 and to the external device of the address filter. The memory address generating section 4 generates a memory address so as to search a terminal address close to the destination address of the address register 2 by means of the binary searching method. Thus, the increase in the time till the end of comparison in the case of increasing the number of terminal addresses is suppressed.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a MAC (Media Access Control) bridge that uses connection traps between LANs (O-Cal Area Networks), and in particular, to determine whether data relay is necessary or unnecessary. Regarding address filters.

[Conventional technology]

MA that relays data between two or more LANs and enables communication between terminals connected to different LANs.
By relaying only the data that needs to be relayed instead of testing all the data on the LAN, the C-Bridge reduces the line efficiency of each connected LAN due to unnecessary data. It is known to be effective in preventing this. Here, the data that needs to be relayed by the MAC bridge is data whose source terminal and destination terminal are connected to different LANs. FIG. 3 and FIG. 4 show whether or not data relay is necessary at the MAC bridge depending on the connection position between the source terminal and the destination terminal. Figure 3 shows a case where the source terminal A and the destination terminal C are connected to different LANs, and the data between these terminals is relayed by the MAC bridge and the destination terminal C is connected to separate LANs.
Communication between AN terminals becomes possible. Figure 4 shows a case where source terminal A and destination terminal B are connected to the same LAN, and by preventing data between such terminals from being relayed to another LAN using a MAC bridge, another LAN
Therefore, unnecessary data is not transmitted, and it is therefore effective to prevent a decrease in LAN line efficiency due to relaying of such unnecessary data.

The above-mentioned data relay execution control by the MAC bridge can be done by inserting dedicated control information into the data sent from the terminal, and by using the destination address included in the data sent from the terminal. Using MAC Buri,
A method is known in which the operator himself determines whether data relay is necessary or unnecessary. Of these two methods, in the method in which the MAC bridge itself uses the destination address to determine whether it is necessary to relay data, the MAC bridge has a system that determines whether or not relaying the data is necessary based on the destination address of the data. A function is needed to determine the Address filters are used to implement such functions.

The function required of the address filter is to register the address of a terminal in advance and to detect whether or not this matches the destination address of data received from the LAN. In a MAC bridge, the addresses of terminals connected or existing in a certain LAN in the AN are registered in an address filter, and registered terminals that match the two destination addresses of data received from that LAN are registered in the address filter. The presence or absence of an address is checked using an address filter, and if a matching terminal address is found, it can be determined that the data is data for communication between terminals within one LAN. Therefore, the MAC bridge does not need to relay this data to another LAN. Conversely, if there is no matching registered address, the destination of the data is a terminal on a LAN different from the LAN that received the data, and the MAC bridge transfers the received data to a different LAN. need to be relayed to. The MAC bridge prepares an address filter for each of the multiple I and ANs connected, and provides each L address filter for each address filter.
By registering the terminal address of the AN, it is possible to determine whether data received from the LAN needs to be relayed to another LAN.

FIG. 5 is a block diagram of an address filter having the functions described above. The addresses of terminals connected to the LAN are registered in the address registration memory 5, and the destination addresses of data received from the LAN are set in the address register 6.

The address comparator 7 compares the value of the terminal address in the address registration memory 5 and the value of the destination address in the address register 6. As a result of the comparison, if the values match, the match is notified to the outside and the process is completed. If the comparison result is a mismatch, the process proceeds to a comparison between the value of the next terminal address in the address registration memory 5 and the value of the destination address in the address register 6. In this way, the address comparison unit 7 sequentially compares the value of the terminal address in the address registration memory 5 and the value of the destination address in the address register 6, and when the values match, it notifies the outside that they match. to complete the process. If any terminal address in the address registration memory 5 does not match the destination address in the address register 6, the absence of a matching address is notified to the outside when the comparison with all registered terminal addresses is completed. Ru. The MAC bridge uses this comparison result to
It separates the data received from N and determines whether it is necessary to relay it to AN.

FIG. 6 shows an example of the configuration of a MAC bridge using the address filter described in FIG. 5.

LAN-I terminal addresses are registered in the address filter 8. Data from the LAN-I is received by the data receiving section 9, and the destination address of the data is set in the address register of the address filter 8. The address filter 8 compares the registered terminal address and the destination address in the received data, and if there is a matching terminal address, notifies the MAC bridge of the match. The MAC bridge discards the received data upon notification of this match. If there is no matching terminal address, the address filter 8 notifies the MAC bridge that there is no matching address.

Based on the notification that there is no matching address, the MAC relay relays the data received by the data receiving section 9 to the LAN-1 using the data transmitting section 10. The data received from LAN-■ is the same as the case from LAN-1, and the address filter 11 is used to determine the necessity of data relay, and the data that needs to be relayed, that is, the terminal whose destination is on LAN-1 The data for is received by the data receiving section 12, and is relayed to the 9LAN-1 by the data transmitting section 13.

By using the above address filter, 9, M
AC Bri, Ji relays only the data that needs to be relayed,
It becomes possible to control such that data that does not need to be relayed is not relayed.

[Problem to be solved by the invention]

By the way, the comparison between the value of the registered terminal address and the value of the destination address of the data received from the LAN can be done by sequentially comparing the registered terminal addresses as described above, but in terms of comparison, Although it is functionally sufficient, as the number of registerable terminal addresses increases, it takes longer to complete the comparison in proportion to the increase.

1. In particular, if the data received from the LAN is data that needs to be relayed to another LANK, the destination terminal address of this data is not registered in the address filter, so it is registered in the address filter. The value of all terminal addresses and the value of the data destination address are compared, and the result that there is no matching address is obtained only after all mismatches are confirmed. In other words, in the case of data that needs to be relayed, the longest comparison time is always required.Using such an address filter to increase the number of terminal addresses that can be registered will reduce the time needed to determine the need for data relay. There is a problem in that the time becomes longer and the data relaying ability of the MAC bridge decreases.

In addition, the number of digits in the terminal address does not have to be a certain number of digits, and can be freely determined for each LAN system, but currently there is no standardization or standardization. Some of the LANs currently available use terminal addresses as long as 48 bits. In order to use the above address filter on a system that uses 48-bit terminal addresses, address registration memory,
It would be sufficient for the address filter to function if the address register and address comparator were each made to have 48 bits of digits. Increasing the number of digits would unnecessarily increase the scale of the software and be disadvantageous in terms of cost.

For example, in order to prepare a 48-bit address registration memory, if a general 8-bit data input/output memory is used, six memories are required. This not only means an increase in the number of memories, but also an increase in the component mounting area. Furthermore, even if we try to miniaturize the circuit using gate arrays, etc., it is impossible to create a memory with a sufficient number of digits and capacity for the address filter of the MAC bridge with the current Kate Play, and the address registration memory 3. becomes an external device. For this reason, the number of inputs and outputs increases, and there are cases where it becomes virtually impossible to realize a gate array.

[Means to solve the problem]

The address filter of the first invention includes an address registration memory in which terminal addresses are registered in the order of values, an address register that holds a data destination address, a terminal address in the address registration memory, and a destination address in the address register. and an address comparison section which takes as input, compares the values to see whether they match or are large and small, and outputs the comparison results; and a binary search method to find a terminal address that is closer to the destination address value based on the output of the comparison results of the address comparison section. and a memory address generation section that provides a read address to the address registration memory for searching using the address register.

The address filter of the second invention includes an address registration memory having only the number of digits obtained by dividing the number of digits of the terminal address into several parts, and in which the terminal address is registered divided into a plurality of addresses;
an address register that can select as an output one of the divided destination addresses that hold the destination address with the same number of digits as the destination address of the received data as an input and the same number of divisions as the address registration memory, and the address register; The device includes a memory and an address comparing section having the same number of digits as the output of the address register, and a memory address generating section that provides a read address to the address registration memory and the address register.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows an embodiment of the first invention, in which terminal addresses to be compared with the destination address values in data received from the LAN are stored in the order of values in the address registration memory l. do. In the following explanation, it is assumed that the addresses are arranged in order from the smallest value to the largest value, but the same function can be achieved even if the order is reversed.

Also, the number of digits in the address registration memo IJl is
The number of digits should match the number of digits of the MAC address used in the AN. Further, it is assumed that the storage capacity of the address registration memory 1 is not less than the number of bits equal to the product of the number of terminal addresses that can be registered multiplied by the number of digits of the terminal address. Since not all terminal addresses are actually registered against the number of terminal addresses that can be registered in the address registration memory l, the free space where no terminal addresses are registered is filled with the values of terminal addresses that can be obtained. The maximum value shall be entered. Among the terminals connected to the LAN, it is not possible to connect a terminal with an address equal to the address value for filling this empty area. The address register 2 is set with the destination address of data received from the LAN. The address comparison unit 3 compares the value of the terminal address in the address registration memory l and the value of the destination address in the address register 2,
The resultant match or magnitude is output to the memory address generator 4 and the address filter. Which terminal address in the address registration memory 1 is compared with the destination address in the address register 2 depends on the memory address indicated by the memory address generator 4. The memory address generation unit 4 uses a binary search method to search for terminal addresses that are arranged in the address registration memory 1 from smallest to largest, for a terminal address that is close to the value of the destination address in the address register 2. Generates a memory address in the same way. In the address filter configured as described above, the memory address generator 4 first indicates the center address of the address registration memory l. If the number of registrable terminal addresses in the address registration memory 1 is an even number, one of the two addresses in the center is indicated. It may be possible to indicate the fall of two addresses, but here it is assumed that the smaller address is indicated. address register 2
When the destination address of data from the LAN is set in , the address comparison unit 3 compares the value of the terminal address output by the address registration memory 1 with the address indicated by the memory address generation unit 4 and the value stored in the address register 2. If the values are the same, the presence of a matching address is notified to the outside of the address filter, and the comparison process is completed.

If the values do not match, and the value of the destination address in address register 2 is larger, the terminal address closest to this destination address value, or the terminal address with a matching value, is stored in the current memory. It can be determined that the terminal exists on the side of an address larger than the address, that is, in an area where a terminal address with a larger value is registered. If the value of the destination address in the address register 2 is smaller, conversely, the memory address is limited to an area with a smaller memory address than the current one, that is, an area where a smaller terminal address is registered. In this way, since the registered terminal addresses are arranged in the numerical order of the values, there is a terminal address that is closer to or matches the value of the destination address in the address register 2 by comparing the address values - times. The area in the address registration memo IJl that will be used can be limited to half of the total area. Next, based on the comparison result of the address values, the memory address generator 4 outputs the center address in the area of the remaining address registration memory l, and the value of the terminal address registered at that address and the address register 2 By comparing the value of the destination address with the value of the destination address, the area where a matching address or a terminal address with the closest value may exist is further limited to half. By repeating such a comparison operation, it is possible to search for a terminal address in the address registration memory l that has a value that is very close to the value of the destination address in the address register 2. The maximum number of address value comparisons required to find a matching terminal address or a terminal address with the closest value is given by the following equation.

(loglN)+1 ・・・・・・
(1) Here, N is the number of terminal addresses that can be registered in the address registration memory. Also, [ ] is a Gauss symbol, which means rounding down to the decimal point. -For example, if the number of registrable terminal addresses is 1024,
It is necessary to perform a maximum of 11 comparisons until the comparison process is completed. If there is a terminal address that matches the destination address in the address registration memory l, the comparison process will be completed as soon as the matching terminal address is found, but how many comparisons will it take to complete? It varies depending on the storage location of the matching terminal address in the address registration memory.

The average value of the number of comparisons is given by the following formula.

(l Ogz N :] -
-(2) When the number of registrable terminal addresses is 1024, the average value of the number of comparisons is 10. In a method in which the terminal addresses in the address registration memo IJl are sequentially compared without using the binary search method, the maximum number of comparisons is N for the number of registerable terminal addresses N, and the average number of comparisons is N/2. times. From this, the number of comparisons required to complete the comparison process is the same or smaller when using the binary search method than when comparing sequentially. In particular, as the number of registrable terminal addresses increases, there is a large difference in the number of comparisons required between the case of using the binary search method and the case of sequential comparison.

FIG. 2 shows an embodiment of the second invention. It is assumed that this address filter is compatible with terminal addresses of 48 bits. It is assumed that the address registration memory 1a stores a terminal address to be compared with the value of the destination address in data received from the LAN.

The number of digits in this memory 1a is 8 bits, which is -6/6 of 48 bits, which is the number of digits in the terminal address used in the connected LAN. The storage capacity of the address registration memory 1a shall not be less than the number of terminal addresses that can be registered multiplied by the number of digits of the terminal address. Furthermore, the number of digits in the address registration memory 1a is -6/67, 8
Since it is a bit, the number of addresses in this memory 1a needs to be six times or more the number of registrable terminal addresses. The terminal address is divided into six addresses in the memory and registered. Since not all terminal addresses are actually registered in the number of registrable terminal addresses in the address registration memory 1a, the free space where no terminal address is registered is filled with possible values of the terminal address. The maximum value shall be entered. Among the terminals connected to the LAN, it is not possible to connect a terminal with an address equal to the address value for filling this empty area. Next, the destination address of the data received from the LAN is written into the address register 2a and holds the value.

Further, the address register 2a divides the 48 bits of the destination address held into six parts of 8 bits each, and outputs any 8 bits of the divided parts based on an instruction from the memory address generator 4a. The address comparator 3a compares the value of the terminal address in the address registration memory 1a and the value of the destination address in the address register 2a. However, the address comparison section 3a
is assumed to be the same number of 8-bit digits as the output of address registration memory la and address register 2a. Therefore, the address comparison unit 3a cannot compare the value of the terminal address registered in the address registration memory 1a and the value of the destination address in the address register 2a at the same time.

Since the address value of the 48-bit digit is divided into 8 bits and outputted from the address registration memory Ha and the address register 2a, the address comparator 3a compares the 8 bits at a time and determines whether they match or do not match. Output each time. For this reason, unlike conventional address filters, it is not possible to immediately determine that a matching terminal address exists based on a matching output from the address comparing section. The memory address generation section 4a instructs the address registration memory la and the address register 2a to read out positions, but it is necessary to read out the terminal address value and the destination address value by dividing them into six parts of 8 bits each. Therefore, the memory address generator 4a outputs a read address to the address registration memory 1a and outputs an output selection signal to the address register 2a so that 8 bits at corresponding positions among the six divided address values are read out. put out. The memory address generation section 4a also includes an address comparison section 3a.
Based on the result of the comparison, the value of the next generated memory address and output selection signal is controlled, and when the comparison process is completed, the presence or absence of a matching terminal address, which is the result of the comparison process, is output to the outside of the address filter. This address filter is 48
The terminal address and the destination address of bits are divided into 6 parts, 8 each, and compared.
Compare them one by one, and if all the six divided values match, it means that a terminal address has been found in the address registration memo 'Jla that matches the destination address in the address register la. , at that point, the existence of a matching address is notified to the outside of the address filter, and the comparison process is completed. If the address comparison unit 3a outputs a cine match result while dividing into six parts and sequentially comparing them, it means that the terminal address and destination address being compared at that time do not match. The comparison operation with that terminal address is immediately stopped and the comparison operation with the next terminal address is started. This kind of comparison operation is performed sequentially for the terminal addresses in the address registration memory la, and when a terminal address that matches the destination address value is found, the presence of a matching address is notified to the outside of the address filter and the comparison is performed. Complete the process. If any terminal address in the address registration memo IJ l a does not match the destination address in the address register 2a, when the comparison with all registered terminal addresses is completed, the no matching address is sent to the outside. Notify and complete the comparison process.

In addition, in this address filter, the time required for comparison processing is at worst six times longer than in the conventional address filter when divided into six, but when the comparison result of the address comparison section 3a does not match, the time required for comparison processing is immediately changed to the next terminal address. Moving to the comparison operation increases the time by three times on average.

〔Effect of the invention〕

As explained above, according to the first invention, an address registration memory in which terminal addresses are registered in the order of values is used, and the destination address of the received data and the terminal address value match or are closest in value. Using a memory address generator that generates an address in the address registration memory to perform a binary search to find the registered terminal address, the value of the terminal address in the address registration memory and the value of the destination address in the address register are combined into an address. Compared to comparing terminal addresses in the address registration memory sequentially, the comparison process of the address filter is completed when the number of terminal addresses that can be registered in the address registration memory is increased. This can significantly reduce the increase in time required.

Further, according to the second invention, the terminal address is divided and registered at a plurality of addresses in the address registration memory, and readout is also performed for each division, and furthermore, the destination address is also read out from the address register from the address registration memory. By dividing and reading the terminal address and the destination address in the same manner as in the reading of , by dividing and comparing the terminal address and destination address, it is not necessary to use an address entry memory with the same number of digits as the terminal address. You will be able to get away with things with a much smaller number of digits.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the first invention, Fig. 2 is a block diagram showing an embodiment of the second invention, and Figs. A diagram showing the data route and the necessity/unnecessity of data relay using a MAC bridge. Figure 5 is a block diagram showing an example of a conventional address filter. Figure 6 is a diagram showing an example of an MAe bridge using an address filter. It is. 1.1a...Address registration memory, 2,2a.
- Address register, 3, 3a...address comparison section, 4, 4a...memory address generation section. Agent Patent Attorney Uchihara Uchihara Old Year's Annual Ja Tree A Ya I7 Hanaga C to r-7 Tsunuma Sankyo 3 Concave A to Unknown ε to 0 de'-y Hasunbanai 4M Houki The fishing rod

Claims (2)

[Claims] (1) An address registration memory in which terminal addresses are registered in the order of values, an address register that holds the destination address of data, a terminal address in the address registration memory and a destination address in the address register are input, and the value is an address comparison unit that compares the match or size of the address comparison unit and outputs the comparison result; and a binary search method to search for a terminal address that is closer to the destination address value based on the output of the comparison result of the address comparison unit. An address filter comprising: a memory address generation unit that provides a read address to the address registration memory. (2) Enter the address registration memory, which has only the number of digits obtained by dividing the number of digits of the terminal address into several numbers, and the terminal address is registered divided into multiple addresses, and the number of digits equal to the destination address of the received data. an address register that holds a destination address and can select one of the divided destination addresses as an output by dividing the held destination address into the same number of divisions as the address registration memory, and an address register that is equal to the output of the address registration memory and the address register. a digit address comparison section;
An address filter comprising: the address registration memory; and a memory address generator that provides a read address to the address register.