Apparatus for handover and frame addition, dropping, and passing in communication system

Abstract

To easily implement handovers for mobile terminals by using Ethernet frames and a ring network.SOLUTION: In an SRAM for access memory, the lower and middle addresses of the source MAC address of a frame to be added to a ring are stored as two 1-bit values. Furthermore, if the lower and middle addresses of the source MAC address of a frame arriving at a device for adding, dropping, and passing frames from a counter-clockwise ring are stored as two 1-bit values, then the bits meaning the lower and middle addresses are erased, and the source MAC address of the frame is stored in a frame drop address table together with a bit 1, which is a negated bit. If the lower address of the source MAC address of the frame to be added to the ring is included in the stored data of the frame drop address table, then 48 bits of the source MAC address are stored.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a communication system handover and frame adding, dropping and passing devices, and in particular to a network handover method for searching for a drop connection destination from a ring network using the lower address and intermediate address of the destination MAC address of an Ethernet (registered trademark) frame, making use of the characteristics of a ring network by using an SRAM that stores lower addresses and intermediate addresses of a MAC address in the frame adding, dropping and passing devices of the ring network. The present invention uses an Ethernet frame and a frame that uses the MAC address portion of an IPv6 address as the MAC address of the frame.

[0002] A conventional example of an address storage method is the one disclosed in Patent Document 1, Japanese Patent Application Laid-Open No. 2000-151617, entitled "Table This conventional example is related to the memory circuit of MAC addresses, It consists of a first table consisting of RAM or the like having column addresses, MAC address data areas, and index areas, and a second table consisting of RAM or the like having row and column addresses, MAC address data areas, and index areas. In this conventional example, the entire 48 bits of a MAC address are stored at location A specified in the memory of the first table by the lower bit string (for example, 16 bits). If another MAC address is already stored at location A, it is recorded at an empty address location B in the memory of the second table, and the recorded address location B is stored in the index area of ​​address location A of the first table. This is a method of specifying recording areas by nesting.

[0003] Furthermore, as a conventional technique for storing addresses, Patent Document 2, Japanese Patent Application Laid-Open No. 2004-15592 "MAC Address Pointer Structure, MAC Address Rearrangement Method." This conventional example is a method for storing multiple MAC addresses at the same address location in an entry table specified by a low-order bit string. If there is no free space, the MAC address is stored in an entry table specified by a low-order bit string different from the low-order bit string of the MAC address.

[0004] A typical example of a conventional ring network is a ring network using a master switch and a slave switch, as shown in Patent Document 3. One of the ring ports on the switch is a blocked port that does not pass frames. This prevents congestion due to clutter. If a failure occurs in the ring network, the monitoring frames that leave the master switch and return to the master switch will not arrive, and instead The master switch receives a failure notification frame from the slave switch at the point of failure. The master switch unblocks the blocked port of the master switch to allow the frame to pass. Also, a blocked port is set on the failed transmission path side of one of the slave switches at the failure point, and the link The ring network continues to operate even after the ring network has recovered from a failure. Generally, in conventional ring networks, ring node devices use MAC address tables. In the event of a transmission path failure, the FDBs of all ring node devices in the ring are cleared and reconstructed through flooding. In conventional WANs, the router is the company's exit point, resulting in congestion and slow data transfer within the WAN. Using MAC for data transfer within the WAN raises the issue of fairness between companies and the fairness of fees. Optical paths can accommodate only about 10 paths, and AWGs are expensive, but they do not have the problem of TCP congestion. If only large companies can afford optical path fees, MAC multiplexing is an option, but it does not solve the congestion problem. If there is no congestion, MAC multiplexing is also an option. This proposal aims to achieve high-speed data transfer by eliminating intra-company routers and forwarding data only using MAC. Since companies vary in quality, MAC multiplexing is desirable, but MAC congestion-free data transfer is only possible at around 10G. Each company uses a VLAN to manage bandwidth reservations at the apex device.

[0005] An example of a handover method is Patent Document 4. This prior art is a method that has an IPv6 connection via a base station before switching via a gateway between a mobile terminal (user equipment (UE)) and an access router, and an IPv6 connection via a destination base station, and reduces the interruption time of frames via the connections when switching connections.

[0006] An example of a handover method is Non-Patent Document 2. This prior art is a method for realizing high-speed handover of Layer 3 by transferring a Fast Binding Update (FBU) and a reverse FBU having an old Care of Address (CoA) and a new CoA of the target access point (AP) between an old access router and a mobile node.

[0007] Non-Patent Document 3 provides an example of a handover method. This prior art is an example of an LTE Layer 3 handover, and involves transferring a Fast Binding Update (FBU) and a reverse FBU between the old access router and the mobile node, which contain the old Care of Address (CoA) and the new CoA of the target base station (BS), achieving a high-speed Layer 3 handover over a Layer 2 handover. The old base station advertises information about surrounding base stations to the mobile node, and the mobile node uses this information to send information about the new base station to the old base station. The old base station then confirms the new access router and sends an FBU to the old access router. After exchanging information with the new access router, the old access router sends packets destined for the mobile node to the new access router. Upon receiving notification after the mobile node's Layer 2 handover, the new access router sends packets stored in its buffer to the mobile node via the new base station.

[0008] An example of a handover method is Non-Patent Document 4. This prior art is an improvement of Non-Patent Document 3, and shortens the time it takes for an old access router to identify a new access router before receiving an FBU. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2000-151617 [Patent Document 2] Japanese Patent Publication No. 2004-15592 [Patent Document 3] Retable No. 2008-068813 [Patent Document 4] Re-tabled publication No. 2017-195497 [Non-patent literature]

[0010] [Non-Patent Document 1] G.8032 “Ethernet Ring Protection Swithing” [Non-patent document 2] RFC4260, ``Mobile IPv6 Fast handovers for 802.11 networks,'' Website, https: / / datatracker.org / doc / html / rfc4260. [Non-patent document 3] RFC5270, ``Mobile IPv6 Fast handovers over 802.16e networks,'' Website, https: / / datatracker.ictf.org / doc / html / rfc5270. [Non-patent document 4] S. Masoud Seyyedoshohadei, et al. ``An Integrated Scheme to Improve Performance of Fast Mobile IPv6 Handover in IEEE 802.16e Network,'' Proceedings of the 2009 IEEE 9th Malaysia International Conference on Communications 15-17 Dec. 2009 Kuala Lumpur Malaysia Summary of the Invention [Problem to be solved by the invention]

[0011] The conventional address storage method disclosed in Japanese Patent Application Laid-Open No. 2000-151617 stores MAC addresses using nesting, which causes a problem that it takes a long time to trace the stored address destination.

[0012] In addition, the conventional address storage method disclosed in Japanese Patent Application Laid-Open No. 2004-15592 uses the lower bits It is stated that if there is no vacant entry table position for the MAC address specified by the column, the MAC address will be stored in the entry table position of a different lower bit column. In this case, however, when selecting the position to store the MAC address, it is necessary to search the entry table positions specified by the two lower bit columns, and since there are multiple stored addresses at the same address position in the same entry table, it is necessary to compare these multiple addresses, which results in a problem that the search takes a long time.

[0013] Conventional ring networks, such as those described in Non-Patent Document 1 and Patent Document 3, store the destination MAC addresses of frames bound for the left-handed ring, the destination MAC addresses of frames bound for the right-handed ring, and the destination MAC addresses of frames sent outside the ring using MAC addresses and port numbers, which means that a large number of MAC addresses must be stored.When the MAC address table stores the entire 48 bits of the MAC address at the address location accessed by the lower address of the MAC address, or when the upper address is stored, if the MAC address cannot be stored, a drawback is that if the destination MAC address of a frame to be transferred is not stored in the MAC address table, the frame is flooded.

[0014] Furthermore, because it uses a forwarding database (FDB) based on a MAC address table, when a loopback frame returns to the source ring node device in the event of a ring transmission path failure, the source MAC address of the frame is stored as the port number outside the ring. Therefore, by setting the port number of the destination MAC address of the frame to the ring downstream transmission path port, RPR can transition to steering. However, in a typical Ethernet ring, the arrival ring port and source MAC address are stored as a pair in the MAC address table, making it impossible to transition to steering operation. Conventional MAC address tables operate at high speed, with a 1M-bit memory class of around 800 MAC addresses, and a 64M memory would slow down the speed. Furthermore, increasing speed through miniaturization leads to the problem of vulnerability to noise, which is related to shielding. In addition, a block point is used in the ring as an STP to avoid congestion caused by flooding when recovering from a ring network failure. However, because of this block point, a method of transitioning from wrapping to steering, such as RPR, cannot be used, and the FDB must be re-stored by flooding.

[0015] Furthermore, in a conventional ring network, when searching for a connection destination, the entire destination MAC address is required, and searching using the lower addresses of the destination MAC address is not possible. Furthermore, in a ring network, even if it is desired to store the source MAC address of a frame in an address table that specifies the frame passage so that a reverse direction frame can pass through a node device that stores a lower address equal to the lower address of the source MAC address, the storage process is not possible because the lower address of the destination MAC address does not indicate when the frame will arrive at the destination. When the destination address is fixed, such as a server, it can be reached using the destination MAC address, but this is not possible for terminals with many destinations.

[0016] Furthermore, the conventional handover technique disclosed in Patent Document 4 sets up two IPv6 connections between the access router and the mobile terminal (user equipment (UE)) and switches between them, which has the drawback of requiring identification of the two IPv6 connections and making handover control complicated.

[0017] All of Non-Patent Documents 2 to 4 involve a layer 3 handover on a layer 2 handover, which involves IP address conversion, and therefore has the drawback of causing a large handover delay.

[0018] The object of this invention is to show a method for realizing simple handover without using the conventional MAC address table by using a ring network in which SRAM that stores lower addresses and intermediate addresses of MAC addresses is used in the ring node devices, in order to expand Layer 2 handover within a subnet by enlarging one MAC domain using an Ethernet ring network and realizing handover with fewer opportunities for IP address conversion using CoA. [Means for solving the problem]

[0019] The present invention has been made in consideration of the above-mentioned problems of the prior art, and the means for solving the problems are the first to fifth aspects of the present invention as shown below. A first aspect of the present invention is a communications system in which a plurality of frame add, drop and pass devices are inserted into a ring network of a clockwise ring transmission path 2 and a counterclockwise ring transmission path 1, base stations are connected to the frame add, drop and pass devices, and a mobile terminal under the control of the base station has a function of receiving packets arriving from the counterclockwise ring of the ring network and forwarding them to a router and a function of blocking the passage of packets having the NIC MAC address of the ring network interface of the router as a source MAC address, so that packets from the mobile terminal travel between the router and the ring network as Ethernet (registered trademark) frames and between the router and the server or exchange as IP packets across the ring network, When a frame from the mobile terminal arrives at a device for adding, dropping, and passing frames in a ring network, regardless of whether the frame is a frame immediately after a change of the destination base station or not, or whether the frame is a communication initiation frame or not, If the source MAC address of the frame is stored in the frame drop address table (11), the source MAC address of the frame is stored in the frame drop address table (11); if the lower address α (the 19th bit from the least significant bit) of the source MAC address of the frame is included in the data stored in the data storage area of ​​the frame drop address table (11) and a negation bit 1 is stored at the end of the data storage area, the source MAC address of the frame is stored in the frame drop address table and the negation bit is erased; otherwise, a bit 1 indicating lower address storage is stored in the first bit position of a storage area of ​​an address location in the SRAM (10) for an access memory accessed with the lower address α (e.g., the 19th bit from the least significant bit) of the source MAC address of the frame, and a bit 1 indicating intermediate address storage is stored in the first bit position of a storage area of ​​an address location in the SRAM (10) for an access memory accessed with the intermediate address β (e.g., the 6th bit to the 24th bit) of the source MAC address of the frame; means for transmitting said frame onto a counterclockwise ring; When a frame from the counterclockwise ring arrives at a frame add, drop, or pass-through device, If the frame is a frame immediately after a change of the destination base station, bit 1 indicating that the lower address is stored is read from the first bit position of a storage area of ​​an address location in the SRAM (10) for an access memory accessed by the lower address α (e.g., the least significant bit to the 19th bit) of the source MAC address of the frame, and bit 1 indicating that the intermediate address is stored is read from the first bit position of a storage area of ​​an address location in the SRAM (10) for an access memory accessed by the lower address α (e.g., the least significant bit to the 19th bit) of the source MAC address of the frame, then erase bit 1 of the first bit of the storage area of ​​the address location in the SRAM (10) for an access memory accessed by the lower address α (e.g., the least significant bit to the 19th bit) of the source MAC address of the frame, On the other hand, if the frame is not a frame immediately after a change of the destination base station, bit 1 indicating that the lower address is stored is read from the first bit position of a storage area of ​​an address location in the SRAM (10) for an access memory accessed by the lower address α (e.g., the least significant bit to the 19th bit) of the source MAC address of the frame, and bit 1 indicating that the intermediate address is stored is read from the first bit position of a storage area of ​​an address location in the SRAM (10) for an access memory accessed by the intermediate address β (the 6th bit to the 24th bit) of the source MAC address of the frame, then bit 1 of the first bit of the storage area of ​​the address location in the SRAM (10) for an access memory accessed by the lower address α (e.g., the least significant bit to the 19th bit) of the source MAC address of the frame is erased, and the source MAC address of the frame is stored in a data storage area of ​​a frame drop address table (11), and bit 1 of a negation bit is stored at the end of the data storage area; means for erasing the MAC address from the frame drop address table (11) if the source MAC address of the frame is stored in a frame drop address table and the frame has just moved to a destination base station away from the router on a counterclockwise ring, and for other cases, transferring the frame as is on the counterclockwise ring and sending it to the router via a vertex device; When a frame arrives at the apex device from the server via the router and is sent to the clockwise ring, and arrives at the frame add, drop, or pass-through device, If the destination MAC address of the frame is stored in the frame drop address table (11), the frame is dropped from the ring. If the destination MAC address of the frame is not stored in the frame drop address table (11), bit 1 indicating that the lower address is stored is read from the first bit position of the storage area of ​​the address location of the SRAM (10) for access memory accessed by the lower address α (for example, from the least significant bit to the 19th bit) of the destination MAC address of the frame, and bit 1 indicating that the lower address is stored is read from the first bit position of the storage area of ​​the address location of the SRAM (10) for access memory accessed by the intermediate address β (from the 6th bit to the 24th bit) of the destination MAC address of the frame. and means for transmitting the frame clockwise to the front of the ring unless bit 1 indicating the presence of storage of the intermediate address is read, and for transmitting the frame out of the ring if bit 1 indicating the presence of storage of the lower address is read from the first bit position of a storage area of ​​an address location in SRAM (10) for access memory accessed by a lower address α (for example, the least significant bit to the 19th bit) of the destination MAC address of the frame, and bit 1 indicating the presence of storage of the intermediate address is read from the first bit position of a storage area of ​​an address location in SRAM (10) for access memory accessed by an intermediate address β (the 6th bit to the 24th bit) of the destination MAC address of the frame.

[0020] A second aspect of the present invention is a communication system according to the first aspect of the present invention, When a mobile terminal (user equipment UE) moves from a source base station to a destination base station on the side of the apex device on a counterclockwise ring, the mobile terminal transmits a MAC address authentication packet transmission request frame of the mobile terminal to the source base station, the source base station checks the MAC address of the mobile terminal in a MAC address table, transmits a MAC address authentication packet to the destination base station on the counterclockwise ring, and transmits a second short lower address (for example, the first shortest bit from the least significant bit) of the MAC address of the mobile terminal to the source base station or an intermediate base station of an add, drop, or pass-through device of the frame. The communication system further comprises means for storing the 48-bit source MAC address of the frame in a frame drop address table (11) accessed with a second lower address (e.g., from the least significant bit to the 16th bit) of the MAC address of the mobile terminal of a device for adding, dropping and passing frames connected to a destination base station, when the lower address α (e.g., from the least significant bit to the 19th bit) of the MAC address of the mobile terminal is included in the 48-bit MAC address read from the frame drop address table (11) accessed with a second lower address (e.g., from the least significant bit to the 16th bit) of the MAC address of the mobile terminal.

[0021] A third aspect of the present invention provides a communication system according to the first aspect of the present invention, The communication system is characterized in that the frame adding, dropping and passing device does not have a timer function for storing addresses in memory.

[0022] A fourth aspect of the present invention is a communication system according to the first aspect of the present invention, The frame is a communication system that is a frame carrying TCP packets or bidirectional UDP packets.

[0023] A fifth aspect of the present invention provides a communication system according to the second aspect of the present invention, The frame is a communication system that carries TCP packets or UDP packets. [Effects of the Invention]

[0024] As explained above, in this invention, instead of a MAC address table, the lower address and intermediate address of the source MAC address of a frame to be added to the ring are stored as two 1-bit bits in an SRAM for access memory using lower addresses and intermediate addresses that specify frame transmission outside the ring, and when the lower address and intermediate address of the source MAC address of a frame that arrives at a device (ring node device) for adding, dropping, and passing frames from the counterclockwise ring are stored as two 1-bit bits, the bit representing the lower address and the bit representing the intermediate address are erased and the source MAC address of the frame is stored together with the negation bit 1 in the frame drop address table, and when the lower address of the source MAC address of a frame to be added to the ring is included in the stored data in the frame drop address table, the 48-bit source MAC address is stored, which results in simple and fast operation and the ring node device (device for adding, dropping, and passing frames) can be implemented with just two memories, which has the effect of reducing system costs. Furthermore, the present invention is a method for realizing handover of a mobile terminal within one MAC domain using a ring network using the above-mentioned memory, which has the effect of reducing power consumption and system costs and enabling high-speed communication. [Brief explanation of the drawings]

[0025] [Figure 1]FIG. 1 is a diagram illustrating an example of handover operation in a communication system between a mobile terminal (user equipment UE) that transfers MAC frames to a router connected to a vertex device of a ring network through a base station connected to the frame add, drop and pass device of a double ring network in which a plurality of devices are connected in a ring shape by an optical transmission path, the mobile terminal (user equipment UE) and a server connected to the ring network via the router; the frame add, drop and pass device has an SRAM for access memory by a lower address and an intermediate address that specify frame transmission outside the ring according to a first embodiment of the present invention and an SRAM for a frame drop address table; [Figure 2] FIG. 2 is a diagram illustrating an example of handover operation in a communication system between a mobile terminal (user equipment UE) that transfers MAC frames to a router connected to a vertex device of a ring network through a base station connected to the frame add, drop and pass device of a double ring network in which a plurality of devices are connected in a ring shape by an optical transmission path, the mobile terminal (user equipment UE) and a server connected to the ring network via the router, the mobile terminal forwarding MAC frames to a router connected to a vertex device of the ring network through a base station connected to the frame add, drop and pass device of a second embodiment of the present invention and a server connected to the ring network via the router. [Figure 3] FIG. 1 shows the positional relationship between the lower address and intermediate address of the source MAC address, which are stored as two 1-bits in the SRAM for access memory by the lower address and intermediate address that specify sending a frame outside the ring in the frame add, drop, and pass-through device of the first and second embodiments of the present invention, and the lower 24 bits of the source MAC address of the frame. DETAILED DESCRIPTION OF THE INVENTION

[0026] A first embodiment of the present invention will be described with reference to Figure 1. This embodiment illustrates an example of handover operation of a TCP frame or voice frame of a mobile terminal (user equipment UE) using a ring network in a communication system in which a wireless base station (eNB) is connected to a frame adding, dropping, and passing device in a dual ring network connected by multiple optical transmission paths. The frame adding, dropping, and passing device has an SRAM that stores two 1-bit values ​​representing a lower address and an intermediate address for access memory based on the lower address and intermediate address used to specify frame transmission outside the ring, and a frame drop address table. A mobile terminal (user equipment UE) under the base station transfers information as a MAC frame to a router connected to the ring network, and then transfers the information as an IP packet between the router and a server connected to the ring network. The frame can also be a UDP frame. The server is a mail receiving server or an Internet connection server.

[0027] In Figure 1, 1 is a transmission path for the counterclockwise ring, 2 is a transmission path for the clockwise ring, 5 is a vertex device, 6-1, 6-2, and 6-3 are devices for adding, dropping, and passing frames (ring node devices), 10 is an SRAM that stores two 1-bit values ​​representing a lower address and an intermediate address for access memory using the lower address and intermediate address that specify frame transmission outside the ring, 11 is a frame drop address table, 12 is an address table for router connection, 13-1, 13-2, and 13-3 are mobile terminals (user devices UE), 14-1, 14-2, and 14-3 are base stations (eNB / BS), 15 is movement of the mobile terminal, 20 is a server, 22 is a router, 26 is a switch, and 27 is a home memory. Also, (1) through (32) indicate the transmission order of frames in which MAC addresses are abbreviated using letter symbols (a1a2, a3a2 are not ASCII codes) transmitted through the ring indicated by the dotted line, and I0, I1, I2, and I3 are global IPv4 addresses dynamically assigned to terminals, or domestic IPv4 addresses of service providers, or IPv6 addresses. SRAM (10) stores two 1-bit values ​​representing the lower and intermediate addresses used for access memory by the lower and intermediate addresses to specify frame transmission outside the ring, with the 1-bit value set to all 0s at initial setting. The OE conversion circuit, EO conversion circuit, input buffer, and output buffer are not shown in the diagram.

[0028] The operation of FIG. 1 will be explained below. An example is shown in which a mobile terminal (user device UE) 13-2 for game communication sends frame (1) Mn2a3a2(I0) (M indicates an Ethernet frame, n2 is the wireless MAC address of the base station 14-2, a3a2 indicates the upper MAC address a3 and the lower MAC address a2 (composed of α and β (see FIG. 3)) which are the MAC addresses of the mobile terminal (user device UE) 13-2, and I0 indicates the IP address of the destination server 20) to the base station 14-2. Here, a2 is not an ASCII code. When a frame arrives at the add, drop and pass device 6-2 from the terminal 13-2, if the source MAC address of the frame is stored in the frame drop address table (11), the source MAC address of the frame is stored in the frame drop address table (11), and if the lower address α (the 19th bit from the least significant bit) of the source MAC address of the frame is included in the data stored in the data storage area of ​​the frame drop address table (11) and if the negation bit 1 is stored at the end of the data storage area, The source MAC address of the frame is stored in the frame drop address table (11), and the negation bit is cleared. However, the figure shows that in cases other than those described above, a bit 1 indicating lower address storage is stored in the first bit position of the storage area of ​​the address location of the SRAM (11) for the access memory accessed by the lower address α (for example, the least significant bit to the 19th bit) of the source MAC address of the frame, and a bit 1 indicating intermediate address storage is stored in the first bit position of the storage area of ​​the address location of the SRAM (11) for the access memory accessed by the intermediate address β (for example, the 6th bit to the 24th bit) of the source MAC address of the frame. In the figure, the bits stored in the access memory (10) based on the lower address and intermediate address that specify the sending of a frame outside the ring are stored as follows: from the left of the SRAM (10), bit 1 is stored in the first bit after the vertical line following the memory access bit string α, bit 1 is stored in the first bit after the vertical line following the memory access bit string β of the SRAM (10), and the even parity bit of the first bit is stored in the second bit.

[0029] The frame is sent to vertex device 5 on counterclockwise ring 1, and when the frame arrives at vertex device 5, the frame's destination MAC address r1r2 is stored in address table 12 for the router, so the frame is dropped from the ring as (5) Mr1r2a3a2(I0) toward router 22 outside the ring. When the frame arrives at router 22, the frame's source MAC address (a3a2) and IP address (I3) are stored in an ARP table (not shown), or the source MAC address (a3a2) is placed in the options field of the IP header, and the IP frame is forwarded as shown in the figure by (6) IP I3 I0 (IP indicates an IP address, I3 indicates the IP address of mobile terminal (user equipment) 13-2, and I0 indicates the IP address of destination server 20), until it reaches server 20.

[0030] Next, an example will be shown in which the mobile terminal (user equipment UE) 13-2 moves from the base station 14-2 to the base station 14-1. Just before the mobile terminal (user equipment UE) 13-2 accesses the destination base station 14-1, it sends a MAC address authentication frame transmission request frame (7)Mn2a3a2() (n2 is the wireless MAC address of the base station 14-2) of the mobile terminal (user equipment UE) 13-2 to the source base station 14-2, and the source base station 14-2 checks the MAC address a3a2 of the mobile terminal (user equipment UE) 13-2 in the MAC address table of the base station 14-2 (not shown) and sends MAC address authentication IP packets (8), (9), and (10)MB1B2(a3a2) of the mobile terminal (user equipment UE) 13-2 (B1 is the NIC MAC address of the destination base station 14-1 selected from the phase modulation angle of the (beam) PSK, and a3a2 is stored in the option field of the IP header) to the destination base station 14-1. When the MAC address authentication IP packet arrives at the frame add, drop and pass device 6-1, the frame's destination MAC address B1 is stored together with the destination port number in a MAC address table (not shown in the figure) that stores only the base station NIC MAC address, so the frame is sent to the destination base station 14-1. When the MAC address authentication frame arrives at the destination base station 14-1, the MAC address of the mobile terminal (user equipment UE) 13-2 is stored in a MAC address table (not shown), a channel is set for the mobile terminal (user equipment UE) 13-2, and the frame Ma3a2n1() is sent to the mobile terminal (user equipment UE) 13-2.

[0031] When a frame (11)Mn1a3a2(I0) (n1 indicates the wireless MAC address of the base station 14-1, and a3a2 indicates the MAC address of the mobile terminal (user equipment) 13-2) from the mobile terminal (user equipment UE) 13-2 arrives at the base station 14-1, the frame is sent to the frame adding, dropping and passing device 6-1 as (12)Mr1r2a3a2(I0) immediately after the destination base station is changed, if the frame adding, dropping and passing device 6-1 connected to the destination base station is a device that connects to a base station away from the router 22 on the counterclockwise ring 1. When the frame from the mobile terminal (user equipment) 13-2 reaches the frame add, drop and pass device (ring node device) 6-1, if the source MAC address of the frame is stored in the frame drop address table (11), the source MAC address of the frame is stored in the frame drop address table (11), and if the lower address α (the 19th bit from the least significant bit) of the source MAC address of the frame is included in the data stored in the data storage area of ​​the frame drop address table (11) and if the negation bit 1 is stored at the end of the data storage area, the source MAC address of the frame is stored in the frame drop address table (11). The C address is stored in the frame drop address table (11), and bit 1 of the negation bit is erased. However, the figure shows a case other than the above, in which bit 1, which indicates lower address storage, is stored in the first bit position of the storage area of ​​the address location of the SRAM (10) for the access memory accessed by the lower address α (for example, the least significant bit to the 19th bit) of the source MAC address of the frame, and bit 1, which indicates intermediate address storage, is stored in the first bit position of the storage area of ​​the address location of the SRAM (10) for the access memory accessed by the intermediate address β (for example, the 6th bit to the 24th bit) of the source MAC address of the frame. The frame is sent to the vertex device 5 having the address table 12 in which the NICMAC address of the upper ring network interface of the router 22 connected to the server 20 is stored via the current transmission line 1 of the counterclockwise ring.

[0032] When the frame is transferred by (13) Mr1r2a3a2(I0) on the counterclockwise ring 1 as shown in the figure and arrives at the frame add, drop and pass device 6-2, the frame is a frame immediately after the destination base station has been changed, and bit 1 indicating that the lower address is stored is read from the first bit position of the storage area of ​​the address location in SRAM (10) for access memory accessed by the lower address α (e.g., the least significant bit to the 19th bit) of the source MAC address of the frame, and bit 1 indicating that the intermediate address is stored is read from the first bit position of the storage area of ​​the address location in SRAM (10) for access memory accessed by the intermediate address β (the 6th bit to the 24th bit) of the source MAC address of the frame, so bit 1 of the first bit of the storage area of ​​the address location in SRAM (11) for access memory accessed by the lower address α (e.g., the least significant bit to the 19th bit) of the source MAC address of the frame is erased. If the source MAC address of the frame is stored in the frame drop address table (11) and the frame is a frame that has just moved to a destination base station in a direction away from the router on the counterclockwise ring, the MAC address is deleted from the frame drop address table (11). Furthermore, if the frame is not a frame immediately after a change of the destination base station, and bit 1 indicating that the lower address is stored is read from the first bit position of the storage area of ​​the address location in the SRAM (10) for the access memory accessed by the lower address α (for example, the least significant bit to the 19th bit) of the source MAC address of the frame, and bit 1 indicating that the intermediate address is stored is read from the first bit position of the storage area of ​​the address location in the SRAM (10) for the access memory accessed by the intermediate address β (the 6th bit to the 24th bit) of the source MAC address of the frame, then bit 1 of the first bit of the storage area of ​​the address location in the SRAM (10) for the access memory accessed by the lower address α (for example, the least significant bit to the 19th bit) of the source MAC address of the frame is erased, and the source MAC address of the frame is stored in the data storage area of ​​the frame drop address table (11), and bit 1 of the negation bit is stored at the end of the data storage area. In the figure, the first and second bits accessed at the lower address α of the SRAM (10) are crossed out to indicate that they have been erased. When the frame being forwarded on counterclockwise ring 1 arrives at vertex device 5, the frame's destination MAC address r1r2 is stored in address table 12 for the router, so the frame is dropped from the ring as (16)Mr1r2a3a2(I0) and headed to router 22 outside the ring.

[0033] When the frame arrives at router 22, the source MAC address (a3a2) and IP address (I3) of the frame are stored in an ARP table (not shown), or the source MAC address (a3a2) is placed in the option field of the IP header, and the IP frame is forwarded as shown in the figure by (17)IPI3I0 (IP indicates an IP address, I3 indicates the IP address of the terminal connected to terminal device 13-2, and I0 indicates the IP address of the destination server 20), and reaches server 20.

[0034] Next, the mobile terminal (user equipment UE) 13-1 receiving the UDP download service sends a frame (19) Mr1r2a1a2(I0) (M indicates an Ethernet frame, r1r2 indicates the NIC MAC address of the ring network interface of the router 22, and a1a2 indicates the MAC address of the terminal equipment 13-1, i.e., upper MAC address a1 and lower MAC address a2 (α,β (see FIG. 3), and I0 indicates the IP address of the destination server) is sent to the frame add, drop and pass-through device 6-1 via the base station 14-1, and when the frame from the mobile terminal arrives at the frame add, drop and pass-through device of the ring network, if the source MAC address of the frame is stored in the frame drop address table (11), the source MAC address of the frame is stored in the frame drop address table (11), and if the lower address α (the 19th bit from the least significant bit) of the source MAC address of the frame is included in the data stored in the data storage area of ​​the frame drop address table (11) and bit 1 of the negation bit is stored at the end of the data storage area, the source MAC address of the frame is stored in the frame drop address table (11), and bit 1 of the negation bit is erased. A bit 1 indicating lower address storage is stored in the first bit position of the storage area of ​​the address location of the SRAM (10) for the access memory accessed by α (e.g., from the least significant bit to the 19th bit), and a bit 1 indicating intermediate address storage is stored in the first bit position of the storage area of ​​the address location of the SRAM (10) for the access memory accessed by the intermediate address β (e.g., from the 6th bit to the 24th bit) of the source MAC address of the frame. Therefore, a bit 1 indicating lower address storage is stored in the first bit position of the storage area of ​​the address location of the SRAM (10) for the access memory accessed by the lower address α (e.g., from the least significant bit to the 19th bit) of the source MAC address of the frame, and a bit 1 indicating intermediate address storage is stored in the first bit position of the storage area of ​​the address location of the SRAM (10) for the access memory accessed by the intermediate address β (e.g., from the 6th bit to the 24th bit) of the source MAC address of the frame. The frame is sent to the vertex device 5 having the address table 12 in which the NICMAC address of the ring network interface of the router 22 connected to the server 20 is stored via the counterclockwise ring working transmission line 1 .

[0035] When the frame is forwarded through counterclockwise ring 1 by (20) Mr1r2a1a2(I0) as shown in the figure and arrives at frame add, drop, and pass-through device 6-2, a bit 1 indicating the presence of the lower address (α) (e.g., the least significant bit through the 19th bit) of the source MAC address of the frame is read from the first bit position of the storage area of ​​the address location in SRAM (10) for access memory accessed by the lower address (α) (e.g., the least significant bit through the 19th bit) of the source MAC address of the frame, and a bit 1 indicating the presence of the intermediate address (β) (the 6th through 24th bits) of the source MAC address of the frame is not read from the first bit position of the storage area of ​​SRAM (10), so the frame is sent directly to the counterclockwise ring. When the frame arrives at vertex device 5, where the destination MAC address (r1r2) of the frame is stored in address table 12 for router connection, the frame is dropped from the ring as (23) Mr1r2a1a2(I0) toward router 22 outside the ring. When the frame arrives at router 22, the source MAC address (a1a2) and IP address (I2) of the frame are stored in an ARP table (not shown), or the source MAC address (a1a2) is placed in the options field of the IP header, and the IP frame is forwarded as shown in the figure by (24)IPI2I0 (IP indicates an IP address, I2 indicates the IP address of mobile terminal (user equipment) 13-1, and I0 indicates the IP address of the destination server 20), and reaches server 20.

[0036] Next, when an IP packet (25) IPI0I2 (IP indicates an IP address, I2 is the IPv6 address or IPv4 address of terminal device 13-1, and I0 is the IP address of server 20) from server 20 arrives at router 22, if the IP packet is an IPv6 address, the destination MAC address paired with the destination IPv6 address I2 of the packet is copied from the MAC address portion of the destination IPv6 address, and a MAC frame (26) Ma1a2r1r2 (I2) using this as the MAC header address of the MAC frame is sent to vertex device 5 of the ring network. If the packet is an IPv4 address, the destination MAC address a1a2 paired with the destination IP address I2 of the packet is found from an ARP table (not shown), and is used as the destination MAC header address of the MAC frame, or the MAC address a1a2 in the option field of the IP header is used as the destination MAC address, and a MAC frame (26)Ma1a2r1r2(I2) using the NIC MAC address r1r2 of the ring network interface of the router 22 as the source MAC address is sent to the vertex device 5 of the ring network.

[0037] When the MAC frame (26) Ma1a2r1r2 (I2) arrives at the vertex device 5, the frame is sent to the clockwise ring 2 because the source MAC address of the frame is stored in the address table 12 for router connection.

[0038] When frame (28) Ma1a2r1r2 (I2) is transferred through clockwise ring 2 and arrives at frame add, drop, and pass-through device 6-2, if the destination MAC address of the frame is stored in frame drop address table (11), the frame is dropped from the ring. However, as shown in the figure, the destination MAC address of the frame is not stored in frame drop address table (11), and bit 1 indicating that the lower address is stored is read from the first bit position of the memory area of ​​the address location in SRAM (10) for access memory accessed by the lower address α (for example, the least significant bit to the 19th bit) of the destination MAC address of the frame, and bit 1 indicating that the intermediate address is stored is not read from the first bit position of the memory area of ​​the address location in SRAM (10) accessed by the intermediate address β (the 6th bit to the 24th bit) of the destination MAC address of the frame, so the frame is sent forward on the clockwise ring.

[0039] When the frame (29) Ma1a2r1r2 (I2) is transferred through the clockwise ring 2 and arrives at the frame add, drop, and pass-through device 6-1, if the destination MAC address of the frame is stored in the frame drop address table (11), the frame is dropped from the ring. However, in the figure, the destination MAC address of the frame is not stored in the frame drop address table (11), and bit 1 indicating that the lower address is stored is read from the first bit position of the memory area of ​​the address location in SRAM (10) for access memory accessed by the lower address α (for example, the least significant bit to the 19th bit) of the destination MAC address of the frame, and bit 1 indicating that the intermediate address is stored is read from the first bit position of the memory area of ​​the address location in SRAM (10) accessed by the intermediate address β (the 6th bit to the 24th bit) of the destination MAC address of the frame, so the frame is sent out of the ring as (31) Ma1a2r1r2 (I2). Since the destination MAC address a1a2 of the frame sent to the base station 14-1 outside the ring is stored in a MAC address table not shown in the figure, the frame (32)Ma1a2n1(I2) (n1 is the wireless MAC address of the base station 14-1) reaches the mobile terminal (user equipment UE) 13-1.

[0040] Next, a second embodiment of the present invention will be described with reference to Figure 2. This embodiment illustrates an example of handover operation of a TCP frame or voice frame of a mobile terminal (user equipment UE) using a ring network in a communication system in which a wireless base station (eNB) is connected to a frame adding, dropping, and passing device in a double ring network, which is connected by multiple optical transmission paths between a frame adding, dropping, and passing device having an SRAM that stores two 1-bit values ​​representing a lower address and an intermediate address for an access memory based on the lower address and intermediate address used to specify frame transmission outside the ring, and a frame drop address table. A mobile terminal (user equipment UE) under the base station transfers information as a MAC frame to a router connected to the ring network, and then transfers the information as an IP packet between the router and a server connected to the ring network. The frame can also be UDP. The server is a mail receiving server or an Internet connection server. This embodiment differs from Figure 1 in that in Figure 1 the mobile terminal moves to the destination base station in a direction away from the router on a counterclockwise ring, whereas in Figure 2 the mobile terminal moves to the destination base station in a direction towards the router on a counterclockwise ring.

[0041] In FIG. 2, the devices with the numbers indicated in the figure operate in the same way as in FIG.

[0042] The operation of FIG. 2 will be explained below. An example is shown in which a mobile terminal (user device UE) 13-2 for game communication sends frame (1) Mn1a3a2(I0) (M indicates an Ethernet frame, n1 indicates the wireless MAC address of the base station 14-1, a3a2 indicates the upper MAC address a3 and the lower MAC address a2 (consisting of α and β) which are the MAC addresses of the mobile terminal (user device UE) 13-2, and I0 indicates the IP address of the destination server 20) to the base station 14-1. Here, a2 is not an ASCII code. The above Ethernet frame (2) Mr1r2a3a2(I0)( When a frame arrives at the device 6-1 for adding, dropping, and passing a frame from the terminal 13-2, if the source MAC address of the frame is stored in the frame drop address table (11), the source MAC address of the frame is stored in the frame drop address table (11), and if the lower address α (the 19th bit from the least significant bit) of the source MAC address of the frame is included in the data stored in the data storage area of ​​the frame drop address table (11) and a negation bit is stored at the end of the data storage area, the frame is dropped. The source MAC address of the frame is stored in the frame drop address table (11) and the negation bit is cleared. However, in addition to the above, the figure also shows that a bit 1 indicating low-order address storage is stored in the first bit position of the storage area of ​​the address location of the SRAM (10) for the access memory accessed by the low-order address α (e.g., the least significant bit to the 19th bit) of the source MAC address of the frame, and a bit 1 indicating intermediate address storage is stored in the first bit position of the storage area of ​​the address location of the SRAM (10) for the access memory accessed by the intermediate address β (e.g., the 6th bit to the 24th bit) of the source MAC address of the frame. In the figure, the bits stored in the access memory (10) based on the lower address and intermediate address that specify frame transmission outside the ring are stored as follows: from the left of the SRAM (10), bit 1 is stored in the first bit after the vertical line following the memory access bit string α, bit 1 is stored in the first bit after the vertical line following the memory access bit string β of the SRAM (10), and bit 1, the even parity bit of the first bit, is stored in the second bit.

[0043] The frame is sent to vertex device 5 on counterclockwise ring 1, and when the frame arrives at vertex device 5, the frame's destination MAC address r1r2 is stored in address table 12 for the router, so the frame is dropped from the ring as (6) Mr1r2a3a2(I0) toward router 22 outside the ring. When the frame arrives at router 22, the frame's source MAC address (a3a2) and IP address (I3) are stored in an ARP table (not shown), or the source MAC address (a3a2) is placed in the options field of the IP header, and the IP frame is forwarded as shown in the figure by (7) IP13I0 (IP indicates an IP address, I3 indicates the IP address of mobile terminal (user equipment) 13-2, and I0 indicates the IP address of the destination server 20), until it reaches server 20.

[0044] Next, the mobile terminal (user equipment UE) 13-1 receiving the UDP download service sends a frame (9) Mr1r2a1a2(I0) (M indicates an Ethernet frame, r1r2 indicates the NIC MAC address of the ring network interface of the router 22, and a1a2 indicates the MAC address of the terminal equipment 13-1, i.e., upper MAC address a1 and lower MAC address a2 (α,β), and I0 indicates the IP address of the destination server) is sent to the frame add, drop and pass-through device 6-1 via the base station 14-1, if the source MAC address of the frame is stored in the frame drop address table (11), the source MAC address of the frame is stored in the frame drop address table (11), and if the lower address α (the 19th bit from the least significant bit) of the source MAC address of the frame is included in the data stored in the data storage area of ​​the frame drop address table (11) and if the negation bit 1 is stored at the end of the data storage area, the source MAC address of the frame is stored in the frame drop address table and the negation bit is erased. Since a bit 1 indicating lower address storage is stored in the first bit position of the storage area of ​​the address location of the SRAM (10) for the memory accessed by the intermediate address β (e.g., from the 6th bit to the 24th bit) of the source MAC address of the frame, a bit 1 indicating lower address storage is stored in the first bit position of the storage area of ​​the address location of the SRAM (10) for the memory accessed by the lower address α (e.g., from the least significant bit to the 19th bit) of the source MAC address of the frame, and a bit 1 indicating intermediate address storage is stored in the first bit position of the storage area of ​​the address location of the SRAM (10) for the memory accessed by the intermediate address β (e.g., from the 6th bit to the 24th bit) of the source MAC address of the frame. The frame is sent to the vertex device 5 having the address table 12 in which the NICMAC address of the ring network interface of the router 22 connected to the server 20 is stored via the current transmission line 1 of the counterclockwise ring.

[0045] When the frame is transferred through counterclockwise ring 1 by (10) Mr1r2a1a2 (I0) as shown in the figure and arrives at frame add, drop, and pass-through device 6-2, bit 1 indicating that the lower address is stored is read from the first bit position of the memory area of ​​the address location in SRAM (10) for access memory accessed by the lower address α (e.g., the least significant bit to the 19th bit) of the source MAC address of the frame, and bit 1 indicating that the intermediate address is stored is not read from the first bit position of the memory area of ​​the address location in SRAM (10) for access memory accessed by the intermediate address β (the 6th bit to the 24th bit) of the source MAC address of the frame, so the frame is sent directly to the counterclockwise ring, and when it arrives at vertex device 5 where the destination MAC address r1r2 of the frame is stored in address table 12 for router connection, the frame is dropped from the ring as (13) Mr1r2a1a2 (I0) toward router 22 outside the ring. When the frame arrives at router 22, the source MAC address (a1a2) and IP address (I2) of the frame are stored in an ARP table (not shown), or the source MAC address (a1a2) is placed in the options field of the IP header, and the IP frame is forwarded as shown in the figure by (14)IPI2I0 (IP indicates an IP address, I2 indicates the IP address of mobile terminal (user equipment) 13-1, and I0 indicates the IP address of the destination server 20), and reaches server 20.

[0046] Next, an example will be shown in which the mobile terminal (user equipment UE) 13-2 moves from the base station 14-1 to the base station 14-2. Just before the mobile terminal (user equipment UE) 13-2 accesses the destination base station 14-2, it sends a MAC address authentication frame transmission request frame (15)Mn1a3a2() (n1 is the wireless MAC address of the base station 14-1) of the mobile terminal (user equipment UE) 13-2 to the source base station 14-1, and the source base station 14-1 checks the MAC address a3a2 of the mobile terminal (user equipment UE) 13-2 in the MAC address table of the base station 14-1 (not shown) and sends MAC address authentication IP packets (16), (17), and (18)MB2B1(a3a2) (B2 is the NIC MAC address of the destination base station 14-2, and a3a2 is stored in the option field of the IP header) of the mobile terminal (user equipment UE) 13-2 to the destination base station 14-2. At this time, the MAC address of the terminal 13-1 with the MAC address a1a2 of the same lower address as the lower address a2 (composed of α and β) of the mobile terminal 13-2 is stored in the MAC address table (not shown) of the base station 14-1. Therefore, the second short lower address (for example, from the least significant bit to the 16th bit) of the MAC address of the mobile terminal of the frame add, drop and pass device connecting to the source base station or an intermediate base station is read from the data storage area of ​​the SRAM (11) for the frame drop address table, which is accessed by the second short lower address (for example, from the least significant bit to the 16th bit) of the MAC address of the mobile terminal. As in the case where the lower address α (the 19th bit from the least significant bit) of the MAC address of the mobile terminal is included in the 48-bit MAC address data, the source MAC address 48 bits (a3a2) of the MAC address of the mobile terminal is stored in a storage area of ​​an address location in SRAM (11) for a frame drop address table accessed by the second lower address (for example, the 16th bit from the least significant bit) of the MAC address a3a2 of the mobile terminal 13-2 in the frame add, drop and pass-through device 6-2 connecting to the destination base station. When the MAC address authentication IP packet arrives at frame add, drop and pass device 6-2, after the above operations are performed, the frame is sent to the destination base station 14-2 because the destination MAC address B1 of the frame is stored together with the destination port number in a MAC address table (not shown in the figure) that stores only the base station NIC MAC address. When the MAC address authentication frame arrives at the destination base station 14-2, the MAC address of the mobile terminal (user equipment UE) 13-2 is stored in a MAC address table (not shown), a channel is set to the mobile terminal (user equipment UE) 13-2, and the frame Ma3a2n2() is sent to the mobile terminal (user equipment UE) 13-2.

[0047] When a frame (19)Mn2a3a2(I0) (n2 indicates the wireless MAC address of the base station 14-2, and a3a2 indicates the MAC address of the mobile terminal (user equipment) 13-2) from the mobile terminal (user equipment) 13-2 arrives at the base station 14-2, the frame is sent to the frame adding, dropping and passing device 6-2 as (20)Mr1r2a3a2(I0) immediately after the destination base station is changed, if the frame adding, dropping and passing device 6-2 connected to the destination base station is a device that connects to a base station approaching the router 22 on the counterclockwise ring 1. When the frame from the mobile terminal (user equipment) 13-2 reaches the frame add, drop and pass device 6-2, the frame is the frame immediately after the destination base station has been changed, and the 48-bit source MAC address (a3a2) of the frame is stored in the frame drop address table (11), which is accessed by the second short lower address (for example, the least significant bit to the 16th bit) of the source MAC address of the frame, so the 48-bit source MAC address is stored. The frame is sent to the vertex device 5 having the address table 12 in which the NICMAC address of the ring network interface of the router 22 connected to the server 20 is stored via the current transmission line 1 of the counterclockwise ring.

[0048] When the frame being forwarded on counterclockwise ring 1 arrives at vertex device 5, the frame's destination MAC address r1r2 is stored in address table 12 for the router, so the frame is dropped from the ring as (23)Mr1r2a3a2(I0) and headed for router 22 outside the ring.

[0049] When the frame arrives at router 22, the source MAC address (a3a2) and IP address (I3) of the frame are stored in an ARP table (not shown), or the source MAC address (a3a2) is placed in the option field of the IP header, and the IP frame is forwarded as shown in the figure by (24)IPI3I0 (IP indicates an IP address, I3 indicates the IP address of the terminal connected to terminal device 13-2, and I0 indicates the IP address of the destination server 20), and reaches server 20.

[0050] Next, when an IP packet (25) IPI0I2 (IP indicates an IP address, I2 is the IPv6 address or IPv4 address of terminal device 13-1, and I0 is the IP address of server 20) from server 20 arrives at router 22, if the IP packet is an IPv6 address, the destination MAC address paired with the destination IPv6 address I2 of the packet is copied from the MAC address portion of the destination IPv6 address, and a MAC frame (26) Ma1a2r1r2 (I2) using this as the MAC header address of the MAC frame is sent to vertex device 5 of the ring network. If the packet is an IPv4 address, the destination MAC address a1a2 paired with the destination IP address I2 of the packet is found from an ARP table (not shown), and is used as the destination MAC header address of the MAC frame, or the MAC address a1a2 in the option field of the IP header is used as the destination MAC address, and a MAC frame (26)Ma1a2r1r2(I2) using the NIC MAC address r1r2 of the ring network interface of the router 22 as the source MAC address is sent to the vertex device 5 of the ring network.

[0051] When the MAC frame (26) Ma1a2r1r2 (I2) arrives at the vertex device 5, the frame is sent to the clockwise ring 2 because the source MAC address of the frame is stored in the address table 12 for router connection.

[0052] When frame (28) Ma1a2r1r2 (I2) is transferred through clockwise ring 2 and arrives at frame add, drop, and pass-through device 6-2, the destination MAC address a1a2 of the frame is not stored in the memory area of ​​the address location of frame drop address table (11) accessed by the second lower address (e.g., the least significant bit to the 16th bit) of the destination MAC address a1a2 of the frame, and bit 1 indicating that the lower address is stored is read from the first bit position of the memory area of ​​the address location of SRAM (10) for access memory accessed by the lower address α of the destination MAC address of the frame (e.g., the least significant bit to the 19th bit), and bit 1 indicating that the intermediate address is stored is not read from the first bit position of the memory area of ​​the address location of SRAM (10) accessed by the intermediate address β (the 6th bit to the 24th bit) of the destination MAC address of the frame, so the frame is sent forward on the clockwise ring.

[0053] When the frame (29) Ma1a2r1r2 (I2) is transferred through the clockwise ring 2 and arrives at the frame add, drop and pass-through device 6-1, the MAC address a1a2 of the mobile terminal 13-1 is not stored in the storage area of ​​the address position of the frame drop address table (11) that is accessed by the second lower address (for example, from the least significant bit to the 16th bit) of the MAC address a1a2 of the mobile terminal 13-1, and the lower address α of the destination MAC address of the frame (for example, from the least significant bit to the 19th bit) Bit 1 indicating that the lower address is stored is read from the first bit position of the storage area of ​​the address location of SRAM (10) for access memory accessed by intermediate address β (6th bit to 24th bit) of the destination MAC address of the frame, and bit 1 indicating that the intermediate address is stored is read from the first bit position of the storage area of ​​the address location of SRAM (10) for access memory accessed by intermediate address β (6th bit to 24th bit), so the frame is sent outside the ring as frame (31)Ma1a2r1r2(I2). Since the destination MAC address a1a2 of the frame sent to the base station 14-1 outside the ring is stored in a MAC address table (not shown), the frame (32)Ma1a2n1(I2) reaches the mobile terminal (user equipment UE) 13-1. It is assumed that the MAC address a3a2 in the MAC address table (not shown) of the base station 14-1 has already been deleted.

[0054] Next, Fig. 3 shows the positional relationship between the lower address, intermediate address and the lower 24 bits of the MAC address when bit 1 is stored in the first bit position of the storage area of ​​the address position of the SRAM for the access memory by the lower address and intermediate address accessed by the lower address (the 1st to 19th least significant bits) of the source MAC address of the frame added to the ring node device in Fig. 1 and Fig. 2, and bit 1 is stored in the first bit position of the storage area of ​​the address position of the SRAM accessed by the intermediate address (the 6th to 24th bits) of the source MAC address of the frame. Fig. 3 shows an example in which the lower address and intermediate address, which are memory access address bits, are 17 bits and 19 bits. In the first and second embodiments, when the memory access bits are 17 bits, they can be configured using only existing memory, making them easy to introduce into a LAN.

[0055] In Figures 1 and 2, when a mobile terminal moves to a destination base station on the side away from the router on the counterclockwise ring, bit 1 indicating that the lower address is stored is deleted from the first bit position of the storage area of ​​the address position of the SRAM (10) for the access memory accessed by the lower address α (for example, from the least significant bit to the 19th bit) of the MAC address of the mobile terminal of the device for adding, dropping and passing frames connected to the source base station. However, when the mobile terminal moves to a destination base station on the side closer to the router on the counterclockwise ring, bit 1 indicating that the lower address is stored is deleted from the first bit position of the storage area of ​​the address position of the SRAM (10) for the access memory accessed by the lower address α (for example, from the least significant bit to the 19th bit) of the MAC address of the mobile terminal of the device for adding, dropping and passing frames connected to the source base station. The bit 1 indicating the presence of storage of the lower address is not erased from the first bit position of the storage area of ​​the address location of the SRAM (10) for the access memory accessed by the lower address α (for example, the least significant bit to the 19th bit) of the MAC address of the mobile terminal of the add, drop and pass-through device, and the bit 1 indicating the presence of storage of the intermediate address is not erased from the first bit position of the storage area of ​​the address location of the SRAM (10) accessed by the intermediate address β (the 6th bit to the 24th bit) of the MAC address, but remains as it is, but this is not a problem.

[0056] In Figures 1 and 2, the lower address and intermediate address of the source MAC address of a frame can be stored in one bit because the number of memory address bits in the SRAM is equal to the number of lower address bits and the number of intermediate address bits of the source MAC address, and the lower address and intermediate address of the source MAC address are included in the access address bit string of the memory.

[0057] In the first embodiment, ring failures can be handled without flooding by steering or double-ring loopback. When double-ring loopback is used, in the event of a ring network failure, frames are looped back to the backup transmission path at the frame add, drop, and pass-through devices on both sides of the failure point, and a loopback bit is added when the loopback occurs. The frame with the loopback bit added passes through all devices up to the second loopback point, and the loopback bit is removed during the second loopback. Although the present invention has been described using an example in which SRAM is used, it can also be realized using MRAM. [Explanation of symbols]

[0058] 1 Counterclockwise ring transmission line 2 Clockwise ring transmission line 5 Vertex device 6-1, 6-2, 6-3 Frame add, drop and pass equipment (ring node equipment) 10 SRAM for accessing memory by lower and intermediate addresses specifying frame sending out of the ring 11 Frame Drop Address Table 12 Address table for router connections 13-1, 13-2, 13-3 Mobile terminal (user equipment UE) 14-1, 14-2, 14-3 Base station (BS) 15 Mobile Device Movement 20 servers 22 Router 26 Switchboard 27 Home Memory

Claims

1. A communication system in which a plurality of frame add, drop and pass devices are inserted into a ring network of a clockwise ring transmission path 2 and a counterclockwise ring transmission path 1, base stations are connected to the frame add, drop and pass devices, and a mobile terminal under the control of the base station communicates with a destination server or exchange via the router connected to the apex device on the ring network, the router having the function of receiving packets arriving from the counterclockwise ring of the ring network and forwarding them to a router and the function of blocking the passage of packets having the NIC MAC address of the ring network interface of the router as a source MAC address, and in which packets from the mobile terminal travel between the router and the server or exchange across the ring network as Ethernet (registered trademark) frames, and between the router and the server or exchange as IP packets, When a frame from the mobile terminal arrives at a device for adding, dropping, and passing frames in a ring network, regardless of whether the frame is a frame immediately after a change of the destination base station or not, or whether the frame is a communication initiation frame or not, If the source MAC address of the frame is stored in the frame drop address table (11), the source MAC address of the frame is stored in the frame drop address table (11); if the lower address α (the 19th bit from the least significant bit) of the source MAC address of the frame is included in the data stored in the data storage area of ​​the frame drop address table (11) and a negation bit 1 is stored at the end of the data storage area, the source MAC address of the frame is stored in the frame drop address table and the negation bit is erased; otherwise, a bit 1 indicating lower address storage is stored in the first bit position of a storage area of ​​an address location of an SRAM (10) for an access memory accessed with the lower address α (e.g., the 19th bit from the least significant bit) of the source MAC address of the frame, and a bit 1 indicating intermediate address storage is stored in the first bit position of a storage area of ​​an address location of the SRAM (10) for an access memory accessed with the intermediate address β (e.g., the 6th bit to the 24th bit) of the source MAC address of the frame; means for transmitting said frame onto a counterclockwise ring; When a frame from the counterclockwise ring arrives at a frame add, drop, or pass-through device, If the frame is a frame immediately after a change of the destination base station, bit 1 indicating that the lower address is stored is read from the first bit position of a storage area of ​​an address location in the SRAM (10) for an access memory accessed by the lower address α (e.g., the least significant bit to the 19th bit) of the source MAC address of the frame, and bit 1 indicating that the intermediate address is stored is read from the first bit position of a storage area of ​​an address location in the SRAM (10) for an access memory accessed by the lower address α (e.g., the least significant bit to the 19th bit) of the source MAC address of the frame, then, when bit 1 indicating that the intermediate address is stored is read from the first bit position of a storage area of ​​an address location in the SRAM (10) for an access memory accessed by the lower address α (e.g., the least significant bit to the 19th bit) of the source MAC address of the frame, the first bit of the storage area of ​​the address location in the SRAM (10) for an access memory accessed by the lower address α (e.g., the least significant bit to the 19th bit) of the source MAC address of the frame is erased, On the other hand, if the frame is not a frame immediately after a change of the destination base station, bit 1 indicating that the lower address is stored is read from the first bit position of a storage area of ​​an address location in the SRAM (10) for an access memory accessed with the lower address α (e.g., the least significant bit to the 19th bit) of the source MAC address of the frame, and bit 1 indicating that the intermediate address is stored is read from the first bit position of a storage area of ​​an address location in the SRAM (10) for an access memory accessed with the intermediate address β (the 6th bit to the 24th bit) of the source MAC address of the frame, then bit 1 of the first bit of the storage area of ​​the address location in the SRAM (10) for an access memory accessed with the lower address α (e.g., the least significant bit to the 19th bit) of the source MAC address of the frame is erased, and the source MAC address of the frame is stored in a data storage area of ​​a frame drop address table (11), and bit 1 of a negation bit is stored at the end of the data storage area; means for erasing the MAC address in the frame drop address table (11) when the source MAC address of the frame is stored in a frame drop address table and the frame has just moved to a destination base station away from the router on a counterclockwise ring, and for other cases, transferring the frame as is on the counterclockwise ring and sending it to the router via a vertex device; When a frame arrives at the apex device from the server via the router and is sent to the clockwise ring, and arrives at the frame add, drop, or pass-through device, If the destination MAC address of the frame is stored in the frame drop address table (11), the frame is dropped from the ring. If the destination MAC address of the frame is not stored in the frame drop address table (11), a bit 1 indicating that the lower address is stored is read from the first bit position of the storage area of ​​the address location of the SRAM (10) for access memory accessed by the lower address α (for example, from the least significant bit to the 19th bit) of the destination MAC address of the frame, and a bit 2 indicating that the lower address is stored is read from the first bit position of the storage area of ​​the address location of the SRAM (10) for access memory accessed by the intermediate address β (from the 6th bit to the 24th bit) of the destination MAC address of the frame. and means for transmitting the frame clockwise to the front of the ring unless bit 1 indicating the presence of intermediate address storage is read, and for transmitting the frame out of the ring if bit 1 indicating the presence of lower address storage is read from the first bit position of a storage area of ​​an address location in an SRAM (10) for access memory accessed by a lower address α (e.g., the least significant bit to the 19th bit) of the destination MAC address of the frame, and bit 1 indicating the presence of intermediate address storage is read from the first bit position of a storage area of ​​an address location in the SRAM (10) for access memory accessed by an intermediate address β (the 6th bit to the 24th bit) of the destination MAC address of the frame.

2. When a mobile terminal (user equipment UE) moves from a source base station to a destination base station on the side of the apex device on a counterclockwise ring, the mobile terminal sends a MAC address authentication packet transmission request frame of the mobile terminal to the source base station, the source base station checks the MAC address of the mobile terminal in a MAC address table, sends a MAC address authentication packet to the destination base station on the counterclockwise ring, and the second short lower address (for example, the 16th bit from the least significant bit) of the MAC address of the mobile terminal of the add, drop and pass device that connects to the source base station or an intermediate base station 2. The communication system according to claim 1, further comprising means for storing the 48-bit source MAC address of the frame in a frame drop address table (11) accessed with a second lower address (e.g., from the least significant bit to the 16th bit) of the MAC address of the mobile terminal of a device for adding, dropping and passing frames connected to a destination base station, when the lower address α (e.g., from the least significant bit to the 19th bit) of the MAC address of the mobile terminal is included in the 48-bit MAC address read from the frame drop address table (11) accessed with a second lower address (e.g., from the least significant bit to the 16th bit) of the MAC address of the mobile terminal.

3. 2. The communication system according to claim 1, wherein said frame adding, dropping and passing device does not have a timer function for storing addresses in memory.

4. 2. The communication system of claim 1, wherein the frames are frames carrying TCP packets or bidirectional UDP packets.

5. 3. The communication system according to claim 2, wherein the frame is a frame carrying a TCP packet or a UDP packet.

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