Handover method for mobile terminal using ring network for searching drop connection destination of packet from ring network by low-order address and intermediate address of destination mac address of ethernet frame

Abstract

To realize handover by transferring Ether frames through a ring network.SOLUTION: There is provided a device in a ring network in which a low-order address and an intermediate address of a transmission source MAC address stored, as two 1-bits, in SRAM for low-order address and intermediate address designation memory accessed by the low-order address and the intermediate address of the transmission source MAC address of a packet subjected to ADD from the outside of the ring have a common address portion Dbit, when the MAC address number required to be stored in an address table designating passage of the packet is N, the mobile terminal number of a transfer packet of a clockwise rotation ring is G, the terminal number of the packet added to the device of adding, dropping and passing of the packet from the outside of the ring is L, and the access low-order address bit number and intermediate address bit number of the SRAM is Sbit, N=G*L*L / e(Dln2) / e((S)ln2) / e((S-D)ln2) is satisfied.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a handover method for a mobile terminal using a ring network that searches for a drop connection destination of a packet from the ring network using the lower address and the middle address of the destination MAC address of an Ethernet (registered trademark) frame. In the present invention, a packet using the MAC address portion of the Ethernet frame and the IPv6 address as the MAC address of the MAC packet is used as the MAC packet.

[0002] As a conventional example of an address storage method, there is Japanese Patent Application Laid-Open No. 2000-151617, "Table Creation Search Device" of Patent Document 1. This conventional example relates to a storage circuit for MAC addresses, and includes a first table composed of a RAM or the like having a row column address, a MAC address data area, and an index area, and a second table composed of a RAM or the like having a row column address, a MAC address data area, and an index area. In this conventional example, the entire 48-bit MAC address is stored at a specified position A in the memory of the first table with the lower bit string (for example, 16 bits). If another MAC address is already stored at the position A, it is recorded at an empty address position B in the memory of the second table, and the recorded address position B is stored in the index area of the address position A of the first table. This is a method of specifying a recording area by nesting.

[0003] Further, as a prior art of an address storage method, there is Japanese Patent Application Laid-Open No. 2004-15592 "MAC Address Pointer Structure, MAC Address Sorting Method" of Patent Document 2. This conventional example is a method of storing a plurality of MAC addresses at the same address position in an entry table specified by a lower bit string. If there is no empty area, the MAC address is stored in an entry table specified by a lower bit string different from the lower bit string of the MAC address.

[0004] As a conventional example of a ring network, a ring network using a master switch and slave switches as in Patent Document 3 is common. In this ring network, one ring port of the master switch is a block port that does not allow frames to pass through, preventing congestion due to flooding. When a failure occurs in the ring network, the monitoring frame that goes out from the master switch and returns to the master switch does not arrive. Instead, a failure notification frame arrives at the master switch from the slave switch at the failure point. Therefore, the master switch releases the block of the block port of the master switch to allow the frame to pass through. Also, a block port is set on the failure transmission path side of one of the slave switches at the failure point to maintain the operation of the ring network even after the failure recovery of the ring network. One ring port of the switch becomes a block port that does not allow frames to pass through, preventing congestion due to flooding. When a failure occurs in the ring network, the monitoring frame that goes out from the master switch and returns to the master switch does not arrive. Instead, a failure notification frame arrives at the master switch from the slave switch at the failure point. Therefore, the master switch releases the block of the block port of the master switch to allow the frame to pass through. Also, a block port is set on the failure transmission path side of one of the slave switches at the failure point to maintain the operation of the ring network even after the failure recovery of the ring network. Generally, in a conventional ring network, since a MAC address table is used in the ring node device, when a transmission path failure occurs, the FDB of all ring node devices in the ring is cleared, and the FDB is reconfigured by flooding.

[0005] As an example of a handover method, there is Patent Document 4. This prior art has an IPv6 connection via a base station and a gateway between a mobile terminal and an access router, an IPv6 connection via the base station before switching, and an IPv6 connection via the target base station, and a method for reducing the downtime of packets via the connection at the time of connection switching.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Non-Patent Document

[0007]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] In the conventional example of Japanese Patent Application Laid-Open No. 2000-151617 as a conventional address storage method, since the MAC address is stored by nesting, there is a problem that it takes time to trace the storage address destination.

[0009] Also, in the conventional example of Japanese Patent Application Laid-Open No. 2004-15592 as a conventional address storage method, if there is no vacancy in the entry table position of the MAC address specified by the lower bit column, it is described that the MAC address is stored in the entry table position of a different lower bit column. In that case, when selecting the position to store the MAC address, it is necessary to search the entry table positions specified by two lower bit columns, and since there are multiple storage addresses at the same address position in the same entry table, it is necessary to compare those multiple addresses, and there is a problem that the search takes time.

[0010] Non-Patent Document 1 and Patent Document 3, which are conventional ring networks, store the destination MAC address of packets going to the left-handed ring, the destination MAC address of packets going to the right-handed ring, and the destination MAC address of packets sent out of the ring using the MAC address and port number. Therefore, the number of MAC addresses to be stored increases. When the entire 48 bits of the MAC address are stored at the address position where the memory is accessed using the lower address of the MAC address in the MAC address table, or when the upper address is stored, if the MAC address cannot be stored, there is a drawback that when the destination MAC address of the transferred packet is not stored in the MAC address table, it is handled by flooding the packet.

[0011] Also, since the FDB (Forwarding DataBase) based on the MAC address table is used, when a loopback packet returns to the source ring node device during a ring transmission path failure, since the source MAC address of the packet stores the port number to the outside of the ring, in RPR, it can shift to steering by setting the port number of the destination MAC address of the packet to the transmission path port for ring downstream. However, in a normal Ethernet ring, there is a problem that it cannot shift to the steering operation because the arrival ring port and the source MAC address are stored in pairs in the MAC address table. Also, as STP for avoiding congestion due to flooding during failure recovery of the ring network, a blocking point is adopted in the ring. Due to this blocking point, a method of shifting from wrapping like RPR to steering cannot be used, and it becomes necessary to re-store the FDB by flooding.

[0012] In addition, when searching for a connection destination in a conventional ring network, the entire destination MAC address is required, and it is not possible to search using the lower address of the destination MAC address. Also, in a ring network, even if one wants to store the packet source MAC address, which is used to specify packet passing, in an address table such that a reverse packet can pass through a node device storing a lower address equal to the lower address of the source MAC address, since it is not known when the destination is reached using the lower address of the destination MAC address, the above storage process cannot be performed. When the destination address is fixed like that of a server, it can be reached using the destination MAC address, but this is not possible for terminals with many destinations.

[0013] In addition, Patent Document 4 of the conventional handover provides two IP6 connections between an access router and a mobile terminal for switching, so two IPv6 connections need to be identified, and there is a drawback that handover control becomes complicated.

[0014] An object of the present invention is to show a method for realizing a simple handover without using a conventional MAC address table by means of a ring network using an SRAM for storing the lower address and intermediate address of a MAC address in a ring node device.

Means for Solving the Problems

[0015] The present invention has been made in view of the problems of the above prior art, and the solution means are the first aspect and the second aspect of the present invention shown below. A first aspect of the present invention is to insert devices for adding, dropping, and passing a plurality of packets into the ring network of the transmission path (2) of the clockwise ring and the transmission path (1) of the counterclockwise ring, connect an L2 switch and a base station to the devices for adding, dropping, and passing the packets, and each terminal and mobile terminal under the L2 switch and the base station receive a packet arriving from the counterclockwise ring of the ring network and transfer it to a router (22). And a function of blocking the passage of a packet having the NIC MAC address of the ring network interface of the router as the source MAC address. In order to communicate with a destination server (20) via the connected router on the vertex device (5) on the ring network, packets from the terminal and the mobile terminal are TCP between the router and the ring network, or an Ethernet frame of a call signal, or a TCP or call signal MAC packet having the MAC address part of the home IPv6 address as the source MAC address, and between the router and the server, as an IP packet, a system for communicating back and forth, When a packet from the terminal or mobile terminal arrives at the device for adding, dropping, and passing packets in the ring network, regardless of whether the packet is a packet immediately after changing the destination base station, and regardless of whether the packet is a communication start packet, Store bit 1 at the first bit position of the storage area of the SRAM for the lower address and the middle address designation memory accessed by the lower address (for example, from the first bit to the seventeenth bit of the least significant bit) of the source MAC address of the packet, and store bit 1 at the second bit position of the storage area of the SRAM address position accessed by the middle address (for example, from the eighth bit to the twenty-fourth bit) of the source MAC address of the packet, and send the packet to the counterclockwise ring, When the packet arrives at the device for adding, dropping, and passing packets, A bit 1 is stored at the first bit position of the storage area of the SRAM address position for the lower address and the middle address designation memory accessed by the lower address of the source MAC address of the packet. And when a bit 1 is stored at the second bit position of the storage area of the SRAM address position accessed by the middle address of the source MAC address of the packet, the source MAC address of the packet is stored in the address table designating the passage of the packet, and otherwise, the packet is directly directed to the vertex device in a counterclockwise ring by means of: When a packet from the server arrives at the vertex device via the router, the packet is sent out in a clockwise ring. When the packet arrives at the device for adding, dropping, and passing the packet, When the destination MAC address of the packet is stored in the address table designating the passage of the packet, the packet is sent out forward in a clockwise ring. When the destination MAC address of the packet is not stored in the address table designating the passage of the packet, and a bit 1 is stored at the first bit position of the storage area of the SRAM address position for the lower address and the middle address designation memory accessed by the lower address of the destination MAC address of the packet, and a bit 1 is stored at the second bit position of the storage area of the SRAM address position accessed by the middle address of the destination MAC address of the packet, the packet is sent out of the ring. Otherwise, the packet is sent out forward in a clockwise ring by means of: The device for adding, dropping, and passing the packet has a common address part Dbit for the source MAC address of the packet stored, the lower address and the middle address of the destination MAC address. When the number N of MAC addresses that need to be stored in the address table specifying the passage of the packets is such that the number of mobile terminals of the transfer packets in the clockwise ring is G, the number of mobile terminals of the packets added, dropped, and passed by the device of the packets from outside the ring to the ring network is L, and the lower address bits and intermediate address bits of the access to the SRAM are Sbit (16bit, 17bit, etc.), N = G * L * L / e (Dln2) / e ((S)ln2) / e ((S-D)ln2) A system characterized by comprising means having a function such that it is about the above.

[0016] A second aspect of the present invention is in the system described in the first aspect of the present invention, The mobile terminal periodically accesses the received mail server, and when it cannot receive a response packet from the received mail server, it accesses the received mail server with a retransmission packet. A system characterized by this.

Effect of the Invention

[0017] As described above, according to the present invention, instead of the MAC address table, an SRAM for a lower address and an intermediate address specifying memory in which the lower address and the intermediate address of the MAC address specifying packet transmission to the outside of the ring have a common address portion is used. Therefore, the operation is simple and fast, and since the ring node device (device for adding, dropping, and passing packets) can be realized with two SRAMs, there is an effect of reducing the system cost. Further, the present invention is a method of realizing handover of a mobile terminal within one MAC domain by a ring network using the above memory, and has an effect of suppressing power consumption and system cost and enabling high-speed communication.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Best Mode for Carrying Out the Invention

[0019] The first embodiment of the present invention will be described with reference to FIG. 1. In this embodiment, a plurality of packet add, drop, and pass devices having an SRAM for a lower address and an intermediate address specifying memory for specifying packet transmission outside the ring and an address table for specifying packet passage are connected by an optical transmission path to form a dual-ring network. A base station is connected to the packet add, drop, and pass devices of the dual-ring network. A mobile terminal under the base station transfers information as a MAC packet to a router connected to the ring network. This is an example of a handover operation of a TCP packet or a voice packet of a mobile terminal using the ring network in a packet transfer system between the mobile terminal and a server connected to the ring network via the router. The server is a received mail server or an Internet connection server.

[0020] In Fig. 1, 1 is the optical transmission path of the counterclockwise ring, 2 is the optical transmission path of the clockwise ring, 5 is the vertex device, 6-1, 6-2, 6-3 are the add, drop, and pass devices of the packet (ring node device), 8 is the address table for specifying the passage of the packet, 11 is the SRAM for the lower address and intermediate address specifying memory for specifying the packet transmission outside the ring, 13-1, 13-2, 13-3 are mobile terminals, 14-1, 14-2, 14-3 are base stations (BS), 20 is the server, 22 is the router, and 12 is the address table for router connection. Also, (1) to (38) indicate the transfer order of the packets in which the MAC addresses transferred in the rings indicated by the dotted lead lines are abbreviated with character symbols, and I0, I1, I2, I3 are the global IPv4 addresses set in the terminals, or the domestic IPv4 addresses of the service providers. Or they are IPv6 addresses. The OE conversion circuit, EO conversion circuit, etc., and the input buffer and output buffer are not shown in the figure.

[0021] The operation of FIG. 1 will be described below. An example is shown in which a mobile terminal 13-2 for mail transmission sends a packet (1) Mn2γa2(I0) (where M indicates an Ethernet packet, n2 is the radio MAC address of the base station 14-2, γa2 indicates the upper MAC address γ and the lower MAC address a2 (composed of α and β) of the mobile terminal 13-2, and I0 indicates the IP address of the destination server 20) to the base station 14-2. When the Ethernet frame (2) Mr1r2γa2(I0) (r1r2 indicates the NIC MAC address of the ring network interface of the router 22) reaches the packet add, drop, and pass device 6-2 from the terminal 13-2, the lower address α of the source MAC address of the packet (for example, from the 1st bit to the 17th bit of the least significant address bit) stores bit 1 in the 1st bit of the storage area of the address position of the SRAM (11) for the lower address and intermediate address designation memory that designates packet transmission to the outside of the ring, stores the even parity of the 1st bit in the 2nd bit, and stores bit 1 in the 3rd bit of the storage area of the address position of the SRAM (11) for the lower address and intermediate address designation memory that designates packet transmission to the outside of the ring with the intermediate address β of the source MAC address of the packet (for example, taking bits 8 to 24 as bits 1 to 17 of the memory access address), stores the even parity of the 3rd bit in the 4th bit, and the packet is sent toward the address table 12 of the vertex device 5 in which the NIC MAC address of the ring network interface of the router 22 connected to the server 20 by the current optical transmission path 1 of the counterclockwise ring is stored. In the figure, the bit storage in the lower address and intermediate address designation memory that designates packet transmission to the outside of the ring is shown with the 1st bit from the left and the last being the 4th bit.

[0022] Direct the packet counterclockwise through Ring 1 towards the vertex device 5. When the packet arrives at the vertex device 5, since the destination MAC address r1r2 of the packet is stored in the address table 12 for the router, the packet is dropped from the ring towards the router 22 outside the ring as (5)Mr1r2γa2(I0). When the packet arrives at the router 22, store the source MAC address (γa2) and IP address (I3) of the packet in an ARP table (not shown in the figure), or put the source MAC address (γa2) in the option field of the IP header, and transfer the IP packet as (6)IPI3I0 (where IP indicates that it is an IP address, I3 is the IP address of the mobile terminal 13-2, and I0 is the IP address of the destination server 20) as shown in the figure to reach the server 20.

[0023] Next, when a mobile terminal 13-1 receiving the mail reception service sends a packet (8)Mr1r2δa2(I0) (where M indicates an Ethernet packet, r1r2 indicates the NIC MAC address of the ring network interface of the router 22, δa2 indicates the upper MAC address δ and the lower MAC address a2 (composed of α and β) of the MAC address of the terminal device 13-1, and I0 indicates the IP address of the destination server) via the base station 14-1 to the device 6-1 for packet add, drop, and pass-through, store bit 1 in the first bit position of the storage area of the address position of the SRAM (11) for the lower address and the intermediate address designation memory accessed by the lower address α (the first bit to the seventeenth bit of the least significant bit) of the source MAC address of the packet, store bit 1 of the even parity bit of the first bit in the second bit position, store bit 1 in the third bit position of the storage area of the address position of the SRAM (11) accessed by the intermediate address β (the eighth bit to the twenty-fourth bit) of the source MAC address of the packet, and store bit 1 of the even parity bit of the third bit in the fourth bit position. The packet is sent toward the address table 12 storing the NIC MAC address of the ring network interface of the router 22 connected to the server 20 via the current optical transmission path 1 of the counterclockwise ring.

[0024] When the packet is transferred through the counterclockwise ring 1 as shown in the figure by (9)Mr1r2δa2(I0) and arrives at the add, drop, and pass device 6-2 of the packet, a bit 1 is stored at the 1st bit position of the storage area of the lower address and the SRAM address position for the middle address designation memory accessed by the lower address α (the 1st bit to the 17th bit of the least significant address bit) of the source MAC address of the packet, and a bit 1 of the even parity bit of the 1st bit is stored at the 2nd bit position. Also, a bit 1 is stored at the 3rd bit position of the storage area of the SRAM address position accessed by the middle address β (the 8th bit to the 24th bit) of the source MAC address of the packet, and a bit 1 of the even parity bit of the 3rd bit is stored at the 4th bit position. Therefore, the source MAC address δa2 of the packet is stored in the address table 8 designating the passage of the packet, and the packet is sent out to the counterclockwise ring. When the destination MAC address r1r2 of the packet arrives at the apex device 5 stored in the address table 12 for the router, the packet is dropped from the ring as (12)Mr1r2δa2(I0) toward the router 22 outside the ring. When the packet arrives at the router 22, the source MAC address (δa2) and the IP address (I2) of the packet are stored in the ARP table (not shown in the figure), or the source MAC address (δa2) is put into the option area of the IP header, and the IP packet is transferred as (13)IPI2I0 (IP indicates an IP address, I2 indicates the IP address of the mobile terminal 13-1, and I0 indicates the IP address of the destination server 20.) as shown in the figure to reach the server 20.

[0025] Next, an example in which the mobile terminal 13-2 moves from the base station 14-2 to under the base station 14-1 is shown. Just before the mobile terminal 13-2 accesses the destination base station 14-1, it sends a MAC address authentication packet transmission request packet (21) Mn2γa2() of the mobile terminal 13-2 to the source base station 14-2. The source base station 14-2 checks the MAC address of the mobile terminal 13-2 in a MAC address table not shown in the figure, and sends a MAC address authentication packet (22) MB1γa2() (where B1 is the MAC address of the base station 14-1) of the mobile terminal 13-2 to the destination base station 14-1. When the MAC address authentication packet arrives at the packet add, drop, and pass device 6-2, the packet is sent to the destination base station 14-1. When a packet (25) Mn1γa2(I0) from the mobile terminal 13-2 (where n1 indicates the wireless NIC MAC address of the base station 14-1 and γa2 indicates the MAC address (upper address γ, lower address a2) of the mobile terminal 13-2) arrives at the base station 14-1, if the packet add, drop, and pass device 6-1 connected to the destination base station is a device that connects to a base station in the direction away from the router 22 on the counterclockwise ring 1, there is a packet immediately after the destination base station change. However, that packet is sent to the packet add, drop, and pass device 6-1 as (26) Mr1r2γa2(I0). When the packet from the mobile terminal 13-2 arrives at the packet add, drop, and pass device 6-1, bit 1 is stored in the first bit of the storage area of the SRAM (11) for the lower address and intermediate address designation memory that designates packet transmission to the outside of the ring accessed by the lower address α of the source MAC address of the packet. As the even parity of the first bit, bit 1 is stored in the second bit. Bit 1 is stored in the third bit of the storage area of the SRAM (11) for the lower address and intermediate address designation memory that designates packet transmission to the outside of the ring accessed by the intermediate address β of the source MAC address of the packet. As the even parity of the third bit, bit 1 is stored in the fourth bit, and the packet is sent toward the address table 12 of the vertex device 5 in which the NIC MAC address of the upper ring network interface of the router 22 connecting to the server 20 via the current optical transmission path 1 of the counterclockwise ring is stored.

[0026] When the packet is transferred to the counterclockwise ring 1 as shown in the figure by (27)Mr1r2γa2(I0) and arrives at the packet add, drop, and pass device 6-2, the least significant bit of the source MAC address α of the packet (the 1st bit to the 17th bit of the least significant address bit) accesses the least significant address and the 1st bit position of the storage area of the SRAM address position for the middle address designation memory stores bit 1, the 2nd bit position stores bit 1 of the even parity bit of the 1st bit, and the 3rd bit position of the storage area of the SRAM address position accessed by the middle address β (the 8th bit to the 24th bit) of the source MAC address of the packet stores bit 1, and the 4th bit position stores bit 1 of the even parity bit of the 3rd bit. Therefore, the source MAC address γa2 of the packet is stored in the address table 8 that designates packet passing. When the packet arrives at the vertex device 5 in the counterclockwise ring 1, since the destination MAC address r1r2 of the packet is stored in the address table 12 for the router, the packet is dropped from the ring as (30)Mr1r2γa2(I0) toward the router 22 outside the ring and goes toward the router 22.

[0027] When the packet arrives at the router 22, the source MAC address (γa2) and IP address (I3) of the packet are stored in an ARP table not shown in the figure, or the source MAC address (γa2) is put into the option area of the IP header, and the IP packet is transferred as (31)IPI3I0 (IP indicates that it is an IP address, I3 is the IP address of the terminal connected to the terminal device 13-2, and I0 indicates the IP address of the destination server 20.) as shown in the figure and reaches the server 20.

[0028] Next, when a packet (32) IPI0I3 from the server 20 (where IP indicates an IP address, I3 is the IPv6 address or IPv4 address of the terminal device 13-2, and I0 is the IP address of the server 20) arrives at the router 22, if the packet is an IPv6 address, the destination MAC address corresponding to the destination IPv6 address I3 of the packet is copied from the MAC address part of the destination IPv6 address and used as the MAC header address of the MAC packet (33) Mγa2r1r2(I3), which is then sent to the vertex device 5 of the ring network. If the packet is an IPv4 address, the destination MAC address γa2 corresponding to the destination IP address I3 of the packet is obtained from an ARP table not shown in the figure, and used as the destination MAC header address of the MAC packet, or the MAC address γa2 in the option area of the IP header is used as the destination MAC address, and the source MAC address is set to the NIC MAC address r1r2 of the ring network interface of the router 22, and the MAC packet (33) Mγa2r1r2(I3) is sent to the vertex device 5 of the ring network.

[0029] When the MAC packet (33) Mγa2r1r2(I3) arrives at the vertex device 5, since the source MAC address of the packet is stored in the address table 12 for router connection, the packet is sent to the right-handed ring 2.

[0030] When the packet (35) Mγa2r1r2(I3) is transferred through the right-handed ring 2 and arrives at the device 6-2 for packet add, drop, and pass, since the destination MAC address γa2 of the packet is stored in the address table 8 that designates packet passing, the packet is sent to the right-handed ring 2.

[0031] When the packet (36) Mγa2r1r2(I3) is transferred to the right - hand ring 2 and arrives at the device 6 - 1 for packet add, drop, and pass - through, if the destination MAC address γa2 of the packet is not stored in the address table that specifies packet pass - through, and the first bit of the storage area of the address position of the SRAM (11) for the lower - order address memory that specifies packet transmission to the outside of the ring accessed by the lower - order address α of the destination MAC address of the packet stores bit 1, and as the even parity of the first bit, the second bit stores bit 1, and the third bit of the storage area of the address position of the SRAM (11) for the lower - order address memory that specifies packet transmission to the outside of the ring accessed by the middle - order address β of the destination MAC address of the packet stores bit 1, and as the even parity of the third bit, the fourth bit stores bit 1, the packet (37) Mγa2r1r2(I3) is sent out of the ring. Since the destination MAC address γa2 of the packet sent to the base station 14 - 1 outside the ring is stored in the MAC address table not shown in the figure, the packet is sent to the mobile terminal 13 - 2. The lower - order address α and the middle - order address β of the SRAM (11) for the lower - order address memory that specifies packet transmission to the outside of the ring of the device 6 - 2 for packet add, drop, and pass - through are erased by a timer. Accordingly, the MAC addresses γa2, δa2 of the address table 8 that specify packet pass - through are also erased.

[0032] In FIG. 1, the lower - order address and the middle - order address of the source MAC address can be stored in 1 bit because the number of memory address bits of the SRAM is equal to the number of lower - order address bits and the number of middle - order address bits of the source MAC address, so the lower - order address and the middle - order address of the source MAC address are included in the address - specifying bit sequence of the memory.

[0033] Note that by separating the memory accessed by the lower address and the memory accessed by the middle address in Example 1, it is also possible to simultaneously perform access by the lower address and access by the middle address, thereby improving the operating speed.

[0034] Next, when storing bit 1 at the first bit position of the storage area of the address position of the SRAM for the lower address and middle address designation memory accessed by the lower address (the first bit to the seventeenth bit of the least significant bit) of the source MAC address of the packet to be added to the ring node device of Example 1, and storing bit 1 at the third bit position of the storage area of the address position of the SRAM accessed by the middle address (the eighth bit to the twenty-fourth bit) of the source MAC address of the packet, the number of MAC addresses that need to be stored in the address table (8) for designating packet passing becomes an issue, and a reference diagram for calculating the number of MAC addresses of the packet used therefor is shown in FIG. 2. Incidentally, when the number of packet terminals to be added to the ring is 5000 (L), the number of terminals transferred on the ring is 100000 (G), and in the case of three examples of the number of SRAM address designation bits (15 bits in (a) of FIG. 2, 16 bits in (b), 17 bits in (c)), and the number of numbers for identifying the NIC manufacturing manufacturers of the mobile terminals is unknown, the number N of MAC addresses of the packets required in the address table for designating packet passing is such that the lower address and the middle address of the MAC address of the packet transferred on the ring are connected, and the probability of matching one of the lower address bits of the lower address group stored in the SRAM is 1 / e (L)ln2) and the probability of matching one of the middle addresses in the one lower address and the middle address group is 5000 / e when the number of overlapping bits between the lower address and the middle address is D bits (10 bits, 8 bits, etc.). (D)ln2) At this time, the probability of the middle addresses matching is 1 / e (L-D)ln2) Therefore, when the lower address and the middle address are 17 bits, D = 10, and N = G * L * (L / e (D)ln2) ) / e (S)ln2 / e (S-D)ln2)=100000 * 5000 * (5000 / e (10ln2) ) / e (17)ln2) / e (7)ln2) ) = 146. This is because the probability that the lower address of the SRAM that matches the lower address of the MAC address from the ring coincides with one of the 5000 is 1 / e (17)ln2) , and the probability that 10 bits in its lower address match the 10 bits of one intermediate address is 5000 / e (10ln2) , and the probability that the upper part of the intermediate address of the SRAM matches the intermediate address of the MAC address from the ring is 1 / e (7)ln2) . When the lower address and the intermediate address are 16 bits, D = 8, and N = 100000 * 5000 * 5000 / e (8ln2) / e (16)ln2) / e (8)ln2) = 582 When the lower address and the intermediate address are 15 bits, D = 6, and N = 100000 * 5000 * 5000 / e (6ln2) / e (15)ln2) / e (9)ln2) ) = 2328 Example 1 can be composed of only existing memories, so it is easy to introduce into the LAN

[0035] In Example 1, when the mobile terminal cannot receive the response packet of the periodic access packet to the receiving mail server, the mobile terminal sends a retransmission packet to the receiving mail server

[0036] In the case of a ring failure in Example 1, it can be handled without flooding by steering or both-ring loopback. When both-ring loopback is performed, in the case of a ring network failure, the packets on both sides of the failure point are looped back to the standby transmission path by the add, drop, and pass devices, and when looped back, a loopback bit is added. The packet with the loopback bit added passes through all devices until the point of the second loopback, and the loopback bit is removed in the second loopback

Explanation of Signs

[0037] 1 Optical transmission path of the counterclockwise ring 2 Optical transmission path of the clockwise ring 5 Vertex device 6-1, 6-2, 6-3 Devices for adding, dropping, and passing packets 8 Address table for specifying packet passing 11 SRAM for lower address and intermediate address specification memory for specifying packet transmission outside the ring 12 Address table for router connection 13-1, 13-2, 13-3 Mobile terminals 14-1, 14-2, 14-3 Base stations (BS) 20 Server 22 Router

Claims

1. Insert devices for adding, dropping, and passing a plurality of packets into the ring network of the transmission path (2) of the clockwise ring and the transmission path (1) of the counterclockwise ring, connect an L2 switch and a base station to the devices for adding, dropping, and passing the packets, and the terminals and mobile terminals under the L2 switch and the base station respectively receive the packets arriving from the counterclockwise ring of the ring network and transfer them to the router (22). The vertex device (5) on the ring network has a function of blocking the passing of packets having the NIC MAC address of the ring network interface of the router as the source MAC address. For communicating with the destination server (20) via the connected router, the packets from the terminals and mobile terminals pass between the router and the ring network as TCP, or an Ethernet (registered trademark) frame of a call signal, or a TCP or call signal MAC packet having the MAC address part of the home IPv6 address as the source MAC address, and the router and the server communicate with each other as IP packets. When the packets from the terminals and mobile terminals arrive at the devices for adding, dropping, and passing the packets of the ring network, regardless of whether the packets are immediately after the mobile destination base station change and regardless of whether the packets are communication start packets. Store bit 1 at the first bit position of the storage area of the address position of the SRAM for the lower address and the middle address designating memory accessed by the lower address (for example, from the first bit to the seventeenth bit of the least significant bit) of the source MAC address of the packet, and store bit 1 at the second bit position of the storage area of the address position of the SRAM accessed by the middle address (for example, from the eighth bit to the twenty-fourth bit) of the source MAC address of the packet, and send the packet to the counterclockwise ring. When the packet arrives at the device for adding, dropping, and passing the packet. When a bit 1 is stored at the first bit position of the storage area of the address position of the SRAM for the lower address and the middle address designating memory accessed by the lower address of the source MAC address of the packet, and a bit 1 is stored at the second bit position of the storage area of the address position of the SRAM accessed by the middle address of the source MAC address of the packet, the source MAC address of the packet is stored in an address table that designates the passage of the packet, and otherwise, the packet is directly sent to the vertex device in a counterclockwise ring by means of: When a packet from the server arrives at the vertex device via a router, the packet is sent out in a clockwise ring. When the packet arrives at the device for adding, dropping, and passing the packet: When the destination MAC address of the packet is stored in the address table that designates the passage of the packet, the packet is sent out in front of the clockwise ring. When the destination MAC address of the packet is not stored in the address table that designates the passage of the packet, and a bit 1 is stored at the first bit position of the storage area of the address position of the SRAM for the lower address and the middle address designating memory accessed by the lower address of the destination MAC address of the packet, and a bit 1 is stored at the second bit position of the storage area of the address position of the SRAM accessed by the middle address of the destination MAC address of the packet, the packet is sent out of the ring, and otherwise, the packet is sent out in front of the clockwise ring by means of: The device for adding, dropping, and passing the packet has a common address part Dbit for the source MAC address, the lower address, and the middle address of the destination MAC address stored therein. When the number N of MAC addresses that need to be stored in the address table designating the passage of the packet is such that the number G of mobile terminals of the transfer packet in the clockwise ring, the number L of mobile terminals of the packet added to the device for adding, dropping, and passing the packet of the ring network from outside the ring, and the number of bits of the lower address access bit and the middle address bit of the SRAM are Sbit (16bit, 17bit, etc.). N = G * L * L / e (Dln2) / e ((S)ln2) / e ((S-D)ln2) A system characterized by comprising means having a function of being of such an extent.

2. The mobile terminal according to claim 1, characterized in that it periodically accesses the received mail server, and when it cannot receive a response packet from the received mail server, it accesses the received mail server with a retransmission packet.

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