JP2006074554A - Aging system of address management table - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ease a load of process for aging determination in a Eethernet switch in the aging system of address management table. <P>SOLUTION: The aging system is provided with an address management table 10 registering a transmitting source address of the receiving frame and a receiving port number corresponding to the entry number and an arrival management unit 11 provided with an arrival management table including an arrival data storing unit for each period of many number of bits corresponding to the entry number. The arrival management unit 11 is constituted to set to the arriving state, when the transmitting source address within the frame when the frame arrives is registered to the address management table 10, the least significant bit in the arrival data storing unit of each period corresponding to the relevant entry number, shift the arrival data of each period for each management period to the left side by one bit, and to conduct the aging by determining the entry number where the number of bits as many as multiple of the management period corresponding to the aging time are all in the non-arriving state to the frame from the least significant bit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an aging method of an address management table in a communication system that multiplexes or switches IEEE Ethernet (registered trademark) frames.

  In recent years, a network that constitutes a core network (ISP (Internet Service Provider), VPN (Virtual Private Network), CDN (Contents Distribution Network: a network that provides contents such as videos)) having a wide bandwidth and high reliability, SDH (Synchronous Digital Hierarchy: Digital Synchronous Network) and ATM (Asynchronous Transfer Mode) technologies have been mainly used as the network to be connected.

  However, with the rapid spread of LAN worldwide, LAN devices such as Ethernet switches have been rapidly provided at low cost. In addition, since a large number of end users, including large-scale corporate users, use LANs that use Ethernet, Ethernet-based services that can build networks at low cost in access networks and core networks have become widespread. .

  FIG. 5 shows the overall configuration of a communication service based on Ethernet technology. In the figure, 80 is a user network, 81A to 81C are users, 82 is FTTH / B / C (Fiber To The Home, Bulking / Curb), ONU (Optical Network Unit), DSU (Digital Service Unit), etc. An access network that accommodates the unit 83, 83 is a unit, 84 is a switch that switches frames based on a MAC (Media Access Control) address included in the header of an Ethernet format frame (an edge switch that uses Ethernet technology, 85 represents a core network, 86-1 represents a core network provided with an ISP, 86-2 represents a core network constituting a VPN, and 86-3 represents a CDN (Contents Distribution). Network) is a core network.

  FIG. 6 shows various formats of the Ethernet frame. FIG. 6 shows a plurality of types of frame configurations, and a. Is Ethernet II (DIX), b. Is Ethernet 802.3 (RAW), c. Is Ethernet 802.3 (LLC: Logical Link Control), d. Corresponds to Ethernet 802.3 (LLC + SNAP (Sub-Network Access Protocol)) standards. In the figure, PA is an 8-byte preamble, which is a specific signal bit string used for establishing synchronization. SFD (1 byte = 8 bits) is a start frame delimiter of a specific pattern. DA (Destination Address) is the destination address (6 bytes), SA (Source Address) is the source address (6 bytes), TPID (Tag Protocol IDentifier) is the tag protocol identifier, TCI (Tag Control Identifier) is the tag control information, Length Represents the length of the data part (excluding padding), Data is data of the upper protocol, PAD (Padding) is a byte to be added and adjusted when the data does not reach the minimum frame length, DSAP (Destination Service Access Point) Is a destination upper layer protocol identifier, SSAP (Source Service Access Point) is a source upper layer protocol identifier, Ctrl (Control) is control, OUI (Organizationally Unique Identifier) is a management organization identifier, and PID (Protocol IDentifier) is a protocol identifier. , FCS (Frame Check Sequence) is a frame check sequence. In the following description, these a. ~ D. In addition to the above frame, a VLAN tag specified by IEEE 802.3 and a frame to which a tag uniquely defined by the user is added are also included in the Ethernet frame.

  In the Ethernet switch, a transfer route is determined based on a destination address (DA) of an Ethernet frame compliant with the IEEE802.1D bridge function (referred to as a MAC bridge). The switch has an address table having a learning function, and has a configuration for associating a source address (SA) that is a MAC address with a source port (SP: Source Port) that represents a port number at which a frame arrives. .

  FIG. 7 is an explanatory diagram of a switch and an address management table. In the figure, 84 is a switch having ports A, B, C, and D, 840 is an address management table, the source address (SA) that is the MAC address at the head, the source port number (SP), and the The last arrival time of the frame having the transmission source address and the transmission source port number is registered. In the initial state, nothing is set in this address management table. For example, when a frame having a source address (SA) “Y” and a destination address (DA) “X” arrives at port A, The switch 84 searches the address management table 840, but treats it as an unlearned frame because the destination address (DA) set in the frame cannot be detected.

  When an unlearned frame arrives, the switch 84 newly registers the transmission source address (MAC address “Y”) and transmission source port number (“A”) in the address management table 840 and sets the time as the final arrival time of the frame. It is set to a certain “T1”, and the received frame is flooded (the frame is copied to all ports of the switch and transferred). On the other hand, when the counterpart device corresponding to the destination (MAC address “X”) of the frame connected ahead of a specific port (port C) responds and transmits the frame, the switch 84 sends the frame to the port. The frame received by C and newly registering the transmission source address “X” and the port number “C” in the address management table 840 and the subsequent MAC address “X” as the destination address (DA) is the port number “C”. Is used in the switch.

  Further, even if registered in the address management table, a source address that does not arrive for a certain period (aging time) is deleted from the address management table. As the aging time, for example, a time of 8 minutes can be used.

  FIG. 8 is an explanatory diagram of a conventional aging method. In the figure, reference numeral 840 denotes an entry management number (No), a transmission source address (MAC address), a transmission source port number (Port number), and an address management table including items of a last arrival time (LAT), and 841 denotes a current item. A device clock 842 for generating time is an aging processing unit.

  In the conventional Ethernet switch, the last arrival time (LAT) in the address management table is individually managed by hardware or software processing in the aging processing unit 842 in FIG. That is, the aging processing unit 842 extracts the corresponding last arrival times LAT (a), LAT (b),... For each entry (numbers a, b, c,...), And performs the next calculation. Judgment is made at regular intervals.

Last arrival time + aging time ≦ current time When an entry corresponding to this, that is, an entry whose aging time has elapsed from the last arrival time is detected, the data of the entry is deleted from the address management table.

As a conventional switching hub technology, there is known a technology for changing the aging time of a filtering table in which a port number corresponding to a source MAC address is registered together with a registration time for each entry (see Patent Document 1). In addition, there is a technique (see Patent Document 2) that reduces the processing load by variably controlling the registration time of the bridge table provided in the LAN switching hub device according to the access frequency.
JP 2000-196643 A Japanese Patent No. 3259672

  In the conventional method, since the aging determination is performed by combining the addition process and the comparison process for each entry, there is a problem that the circuit scale becomes large when realized by hardware and the calculation load becomes heavy when realized by software. In this regard, in the techniques of Patent Document 1 and Patent Document 2 described above, the cycle for performing the aging determination is variably set, and the aging determination process itself is not performed efficiently.

  An object of the present invention is to provide an address management table aging method capable of reducing the load of aging determination processing in an Ethernet switch.

  FIG. 1 shows the principle configuration of the present invention. In the figure, reference numerals 10 to 13 denote parts constituting a communication system using an Ethernet frame according to the present invention, and 10 denotes an address management table for managing MAC addresses, and entry numbers (represented by No.) a, b, Corresponding to c,..., a transmission source address (also referred to as a source address: SA) and a port number at which a frame arrives (also referred to as a source port: SP) are registered. 11 is an arrival presence / absence management unit provided by the present invention, 110 is an entry number storage unit 110a for storing each entry number, and a period-by-cycle arrival presence / absence data storage unit 110b having (n + 1) bits corresponding to each entry number. It is the arrival presence management table comprised by these. Reference numeral 12 denotes a device clock for interrupting every management cycle, and 13 denotes an aging processing unit.

  The arrival / absence data storage unit 110b for each period corresponding to each entry number in the address management table 10 is composed of (n + 1) bits of data, and within a certain management period (T), the transmission source address (SA) of the entry number. When a frame having a transmission source port (SP) arrives, “1” is set to the least significant (right end) bit of the corresponding entry in the period arrival / absence presence / absence data storage unit 110b. This least significant bit (rightmost bit) indicates whether or not a frame has arrived in the latest management cycle (represented by T0), and the left bit of the least significant bit indicates whether or not a frame has arrived one cycle before (represented by T1) The most significant bit (n bits) at the left end indicates whether or not a frame has arrived n cycles before (represented by Tn).

  The address management table 10 is initially in a reset state, and when the frame arrives, the source MAC address and the port number at which the frame has arrived are registered corresponding to the entry number. When there is a frame arrival, the arrival presence / absence management unit 11 searches and determines whether there is an entry in which the transmission source MAC address of the arrived frame matches the “MAC address” in the address management table 10. If there is no matching entry, it is registered in the address management table 10 together with the incoming port as a new entry. Then, the latest bit (rightmost bit) in the (n + 1) bits of the period arrival arrival presence / absence data storage unit 110b corresponding to the entry number in the address management table 10 is set to “1” indicating the arrival of the frame. When an interrupt occurs every fixed management period (t) from the device clock 12, the bit string corresponding to all the entry numbers is shifted to the left by 1 bit, and the latest bit is set to “0”. Further, if the aging time of the address management table 10 is set to m times (mt) of the fixed management cycle (t) for each management cycle, m bits including the least significant bit of the arrival / absence data storage unit 110b for each cycle ( Whether m bits from the right end) are all “0” (no frame received) is identified. The entry numbers that are all “0” are notified to the aging processing unit 13, and the aging processing unit 13 deletes (or invalidates) the data (source address and source port) of the corresponding entry number in the address management table 10. Instruct.

  According to the present invention, in a communication system that multiplexes or switches Ethernet frames, in the aging process of each entry in the address management table for managing the MAC address, arrival presence / absence management data that records the arrival / absence within a certain period for each entry is stored. By holding, when determining whether or not the aging process is executed for each entry, it is possible to determine for each entry only by counting the number of consecutive 0s corresponding to the aging time from the least significant bit of the arrival / absence management data. It has become easy to implement in both hardware and software.

  FIG. 2 is a diagram illustrating the configuration of the first embodiment. In the figure, 20 to 23 correspond to reference numerals 10 to 13 in FIG. 1, 20 is an address management table for managing MAC addresses, 20a is an entry number (indicated by Entry No., 0, 1, 2,..., 4095) 20b is a used / unused indication bit indicating whether the entry is in use or unused, 20c is a source address (source address: SA) that is a MAC address, and 20d is a source port (Port). This represents a number (source port: SP) number. 21 is an arrival presence / absence management unit, 210 is an arrival presence / absence management table provided in the arrival presence / absence management unit, 210a is an entry number storage unit, 210b is a 16-bit period arrival / absence presence / absence data storage unit, and 210c is This is a used / unused display bit indicating whether the entry number area is in use or unused. 22 is an apparatus clock, 23 is an aging processing unit, 24 is a frame input processing unit, 25 is a frame relay processing unit, and 26 is a frame output processing unit.

  In the configuration of the first embodiment, the used / unused display bits 20b and 210c are provided in the address management table 20 and the arrival presence / absence management table 210 in the arrival presence / absence management unit 21, respectively, so that they are not used in the respective data storage areas. It is possible to easily determine whether there is an area (used / unused display bit is “0”) and to newly register a free area.

  Corresponding to each entry number in the address management table 20, arrival information for each cycle of 16 bits is provided for the entry number in the arrival presence management table 210, the number of entries is 4096 (0 to 4095), and a certain management cycle is set. 1 minute and aging time is 8 minutes.

In the device initialization, the processes (1) to (5) are executed.
(1) Start the device.
(2) Set the current time in the device clock 22.
(3) The address management table 20 is initialized. In this case, “0” (invalid state) is written in the used / unused display bit 20b for all entries.
(4) All “1” is written to all entries in the arrival / absence data storage unit 210b for each period.
(5) The input process of the arrival frame is started.

Processing for Each Frame Arrival In the first embodiment, the following processing is executed in the frame input processing unit 24, the frame relay processing unit 25, and the frame output processing unit 26 for each frame arrival.

Each time a frame arrives, the frame input processing unit 24 performs the following processes (1) to (3).
(1) Extract the source address (source address: SA) and source port (source port: SP) of the arrival frame.
(2) The source address of the arrival frame is searched for the MAC address of the address management table 20.

    (a) If the transmission source address is not registered in the address management table 20 and there is an empty entry (used / unused display bit is “0”), a new MAC address is registered as the transmission source address, and the corresponding “1” is written in the least significant bit of the arrival / absence data storage unit 210b for each period.

  As the address registration method, the used / unused display bit 20d of the free entry in the address management table 20 is set to “1”, the MAC address = the source address of the arrival frame (SA), and the port number = the source port of the arrival frame (SP ) Is written.

    (b) If the source address is not registered and there is no empty entry (used / unused indication bit is “0”), the new MAC address is not registered and is ignored.

    (c) When the transmission source address has been registered in the same combination as the new arrival source port, “1” is written in the least significant bit of the corresponding entry in the arrival presence / absence management table 210.

    (d) If the source address has already been registered with a combination different from the new arrival source port, the source port of the corresponding entry in the address management table is rewritten with the new arrival source port number. The corresponding entry in the arrival presence / absence management table 210 is initialized with all “1”.

  (3) The arrival frame is transferred to the frame relay processing unit 25.

  Each time a frame arrives, the frame relay processing unit 25 performs the following processes (1) and (2).

(1) The address management table 20 is searched with the destination address (DA) of the arrival frame.
(2) When the entry of the corresponding MAC address exists (hits) in the address management table 20, it is transferred to the frame output processing unit 26 of the transmission source port in the corresponding entry. If there is no hit, it is transferred to the frame output processing unit 26 of all ports.
Each time a frame arrives, the frame output processing unit 26 performs the following process (1).

(1) The frame received from the frame relay processing unit 25 is transmitted on the transmission path.
In the first embodiment, the following processes (1) to (3) are performed at regular intervals (1 minute).
(1) For all entries (entry numbers i, i = 0, 1,... 4095), the aging processing unit 23 performs the lower 8 bits (aging time) of the arrival / absence presence / absence data storage unit 210b of the arrival / absence presence / absence management table 210. 8), and the use / unused display bit of the arrival / absence management table 210 is “1” (used) (the last 8 minutes among the used entries). Search for frames that do not arrive at

  (2) Each entry number hit in the above search is notified to the aging processing unit 23, the aging processing unit 23 instructs to delete the data of the corresponding area number in the address management table 20, and the used / unused display bit 210c is indicated. Write “0” (unused). As a result, the past aging time (8 minutes) can be checked every management cycle (1 minute).

  (3) The 16 bits of the arrival / absence data storage unit 210b for each period in the arrival / absence management table 210 are shifted left by 1 bit. For the least significant bit of the arrival / absence data storage unit 210b for each period, the inverted value of the used / unused display bit of each entry is written.

  With the configuration of the first embodiment, an unused entry number can be easily detected by providing used / unused bits for the address management table 20 and the arrival presence / absence management table 210. Further, the arrival / absence data storage unit 210b for each period is shifted to the left every fixed period (1 minute) to record the presence / absence of the arrival of a frame within each period, and the arrival of the latest 8 minutes as the aging time. Whether the lower 8 bits of the arrival / absence arrival / absence data storage unit 210b are all “0” (indicating that the frame has not arrived in the last 8 minutes), or not (at least one of the lower 8 bits is “ It can be identified by checking if 1 ″ is standing.

  FIG. 3 shows the configuration of the second embodiment. In the figure, 30 to 33 correspond to reference numerals 10 to 13 in FIG. 1, and 34 to 36 correspond to 24 to 26 in the first embodiment in FIG. That is, 30 is an address management table for managing MAC addresses, 30a is a used / unused display bit indicating whether an entry is in use or unused, 30b is an entry number (displayed as an entry number, 0, 1, 2) ,... Up to 4095), 30c represents a source address (source address: SA) which is a MAC address, and 30d represents a port number (source port: SP) of the source. 31 is an arrival presence / absence management unit, 310 is an arrival presence / absence management table provided in the arrival presence / absence management unit, 310a is an entry number storage unit, 310b is a 16-bit second arrival / absence arrival data storage unit, 310c is a 16-bit first arrival / absence data storage unit for each period, and 310d is a used / unused display bit indicating whether the area of the entry number is in use or unused. 32 is a device clock, 33 is an aging processing unit, 34 is a frame input processing unit, 35 is a frame relay processing unit, and 36 is a frame output processing unit.

  In the configuration of the second embodiment, the configuration of the arrival presence / absence management table 310 in the arrival presence / absence management unit 31 is different from the arrival presence / absence management table 210 of the first embodiment. That is, the arrival / absence data for each cycle is composed of the first arrival / absence data storage unit 310c for each cycle and the second arrival / absence data storage unit 310b for each cycle. Similar to the arrival / absence data storage unit 210b for each cycle in the first embodiment, when a frame arrives within a certain cycle (1 minute), “1” is set in the least significant bit corresponding to the entry number, and the cycle of 1 minute. Each time one bit is shifted to the left (the least significant bit is set to the inverted contents of the used / unused display bits). When the first cycle arrival / absence data storage unit 310c shifts to the left every minute, the left end (most significant) bit overflows. The contents of the overflowed bits are supplied to the rightmost (least significant) bit of the second period arrival / absence presence / absence data storage unit 310b, and the contents and logical sum (OR) are taken and set. The second period arrival / absence presence / absence data storage unit 310b shifts 1 bit to the left every 16 minutes by the device clock 32.

  In the second embodiment, the number of entries in the address management table 30 and the arrival presence / absence management table 310 is 4096, the period is 1 minute, and the aging time of the aging processor 33 is 100 minutes.

Device initialization processing of the second embodiment
(1) Device startup
(2) Current time setting
(3) Initialization of the address management table 30: “0” (unused) is written to the used / unused display bits for all entries.

  (4) Initialization of arrival / absence management table: All “1” s are written in the first and second arrival / absence data storage units 310c and 310b for each period for all entries.

  (5) Set the number of bits in the arrival / absence data for each period to be checked at regular intervals to determine whether it is subject to aging processing. When the monitoring cycle is 1 minute and the aging time is 100 minutes, the following values are obtained.

Number of monitoring bits in first cycle arrival / absence data storage unit 310c = MIN (aging time + 1, 16) = MIN (101, 16) = 16 bits Number of monitoring bits in second cycle arrival / absence data storage unit 310b = MIN (rounded down (aging time / 16), 16) = 6 bits
(6) The input process of the arrival frame is started.

Processing for Each Frame Arrival in Embodiment 2 In Embodiment 2, the following processing is executed in the frame input processing unit 34, the frame relay processing unit 35, and the frame output processing unit 36 for each frame arrival.

  The frame input processing unit 34 according to the second embodiment performs the following processes (1) to (3) every time a frame arrives.

  (1) Extract the source address (source address: SA) and source port (source port: SP) of the arrival frame.

  (2) Search the transmission source address (SA of the received frame) in the address management table 30.

    (a) If the source address is not registered in the address management table 30 and there is an empty entry (used / unused display bit is “0”), a new MAC address is registered as the source address and “1” is written in the least significant bit of the arrival number data storage unit 310c for each first period of the entry number.

  As an address registration method, the used / unused display bit 20d of the address management table 30 is set to “1”, the MAC address = the source address (SA) of the arrival frame, and the port number = the source port (SP) of the arrival frame. ) Is written.

    (b) If the source address is not registered and there is no empty entry (used / unused indication bit is “0”), the new MAC address is not registered.

    (c) When the transmission source address has already been registered in the same combination as the source port (SP) of the new arrival frame, “1” is written in the least significant bit of the corresponding entry in the arrival presence / absence management table 310.

    (d) When the transmission source address has been registered with a combination different from the source port (SP) of the new arrival frame, the source port of the corresponding entry in the address management table 30 is rewritten with the new arrival source port number. The corresponding entry in the arrival presence / absence management table 310 is initialized with all “1”.

  (3) The arrival frame is transferred to the frame relay processing unit 35.

  The frame relay processing unit 35 of the second embodiment performs the following processes (1) and (2) every time a frame arrives.

(1) The address management table 30 is searched with the destination address (DA) of the arrival frame.
(2) When the entry of the corresponding MAC address exists (hits) in the address management table 30, it is transferred to the frame output processing unit 36 of the source port (source port) in the entry. If there is no hit, it is transferred to the frame output processing unit 36 of all ports.

The frame output processing unit 36 according to the second embodiment performs the following process every time a frame arrives.
(1) The frame received from the frame relay processing unit 35 is transmitted on the transmission path.
In the second embodiment, the following processes (1) to (3) are performed every minute.

  (1) The aging processing unit 33 sets the use / unused display bit 310d of the arrival presence / absence management table 310 to “1” (used) for all entries (entry numbers i, i = 0, 1,... 4095). In addition, all 16 bits of the second arrival / absence data storage unit 310b (No. i) = all “0”, and the lower 6 bits of the first arrival / absence data storage unit 310c (No. i) = all Search for an entry corresponding to “0”. This process detects that the frame has not been received in the latest 16 minutes × 6 = 96 minutes because the lower 6 bits of the second period arrival / absence data storage unit 310b are “0”. Since the 16 bits of the arrival / absence data storage unit 310c of 1 period are all “0”, it is detected that no frame has been received in the latest 16 minutes, and the total aging time is 96 + 16 = 112 minutes. Correspond.

  (2) Each entry hit in the above (1) is notified to the aging processing unit 33, the aging processing unit 33 is instructed to delete the corresponding data in the address management table 30, and the used / unused display bit is set to “0”. ”(Unused) is written.

  (3) When the first period arrival / absence data storage unit 320c (16 bits) in the arrival / absence management table 310 is shifted to the left every minute, the least significant bit is the inverted value of the used / unused display bit value. Write.

In the second embodiment, the following processing is performed every 16 minutes.
(1) The second period arrival / absence data storage unit 310b is shifted by 1 bit to the left and the least significant bit (rightmost bit) is ORed with all bits of the first period arrival / absence data storage unit 310c. Set the result.

  According to the configuration of the second embodiment, even if the aging time is extended by using 1 minute which is the management cycle, it is possible to cope with a simple configuration without significantly increasing the number of bits for storing arrival / absence data for each cycle. it can.

  FIG. 4 shows a configuration example of a layer 2 switch to which the present invention is applied. In the figure, 4 is a layer 2 switch that performs switching at layer 2 as a data link layer, 40 is a frame input / output unit provided in a plurality of input / output ports, 41 is a switch unit, 410 is a frame processing unit, and 411 is a frame. A relay processing unit, 412 is a MAC address management table, 413 is an arrival presence / absence management unit (210 in FIG. 2, 310 in FIG. 3), and 42 is a device clock.

  In this layer 2 switch, the frame input to the frame input / output unit 40 is input to the frame processing unit 410 of the switch unit 41. At this time, the input port (source port: SA) number input to the frame is identified by hardware, the source address (SA) in the frame is detected, and the MAC address management table 412 is searched. That is, the address management table (20 in FIG. 2 and 30 in FIG. 3) described above with reference to FIGS. 2 and 3 is searched for an entry having the same source address (SA) and source port (SP). Then, “1” is set in the least significant bit of the arrival / absence data for each period (not shown in FIG. 4, 210b in FIG. 2, second arrival / absence data 310c in FIG. 3) inside the arrival / absence management unit 413. The frame relay processing unit 411 identifies the destination address (DA) of the frame, searches the MAC address management table 412 by the destination address (DA), detects the corresponding transmission source port (SP) when hit, A process of transmitting a frame toward the frame input / output unit 40 corresponding to the port is performed. If there is no hit, a frame number is transmitted from each frame input / output unit 40 and a response from the other party is detected to detect the port number corresponding to the destination address (DA). The arrival presence / absence management unit 413 performs the operation (shift operation and aging check) described for the configuration of the first embodiment of FIG. 2 or the configuration of the second embodiment of FIG. ) Is executed.

It is a figure which shows the principle structure of this invention. 1 is a diagram illustrating a configuration of Example 1. FIG. 6 is a diagram illustrating a configuration of Example 2. FIG. It is a figure which shows the structural example of the layer 2 switch to which this invention is applied. It is a figure which shows the whole structure of the communication service based on Ethernet technology. It is a figure which shows the various formats of an Ethernet frame. It is explanatory drawing of a switch and an address management table. It is explanatory drawing of the conventional aging system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Address management table 11 Arrival / absence management unit 110 Period arrival / absence table 110a Entry number storage unit 110b Period arrival / absence data storage unit 12 Device clock 13 Aging processing unit

Claims (4)

An address management table aging method in a communication system for multiplexing or switching Ethernet frames,
An address management table in which the transmission source address and reception port number of the received frame are registered in correspondence with the entry number
An arrivals presence / absence management unit including an arrival / absence presence / absence management table including an arrival / absence presence / absence data storage unit of a number of bits of (n + 1) or more corresponding to the entry number;
The arrival / absence management unit stores the arrival / absence data for each period corresponding to the entry number corresponding to the registered address management table when the transmission source address in the frame is already registered in the address management table when the frame arrives. The least significant bit of each part is set to the frame arrival state, and the arrival / absence data for each period is shifted to the left by 1 bit every management period of (n + 1) of the aging time, and the aging time is equivalent to the least significant bit. The entry number in which all the least significant bits to (n + 1) bits of the arrival / absence data for each period representing the period state are in a frame non-arrival state is determined, and the data in the address management table of the determined entry number is deleted. An aging method for address management tables. In claim 1,
In each of the address management table and the arrival presence / absence management table, a used / unused display bit for setting a use state of a data area corresponding to each entry number is provided,
The arrival presence / absence management unit is configured such that every number of bits corresponding to the aging time including the least significant bit of the arrival / absence presence / absence data storage unit in each cycle is in a frame non-arrival state and the use / non-arrival management table is used / The entry number in which the bit indicating unused is used is determined, and the used / unused display bits of the address management table and the arrival presence / absence management table corresponding to the determined entry number are set to an unused state. An aging method for address management tables. In either claim 1 or 2,
In the arrival presence / absence management table, the most significant bit signal of the arrival / absence presence / absence data storage unit composed of the (n + 1) bits corresponds to each entry number every (n + 1) times the management cycle. A second period arrival / absence presence / absence data storage unit composed of (n + 1) bits inputted is provided,
An address management table aging method, wherein each bit constituting the second period arrival / absence presence / absence data storage unit represents a frame arrival state at a cycle of (n + 1) times the management cycle. In either claim 2 or 3,
An aging of an address management table, wherein when the arrival / absence data storage section for each cycle is shifted left by 1 bit for each management cycle, the used / unused display bit is written as an inverted value in the least significant bit at the right end. method.

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