JP2025065663A - A handover method for a mobile terminal using a ring network for transferring Ethernet frames, in which a MAC address storage method for storing a bit 1 in both memory storage areas accessed by the lower address and intermediate address of the source MAC address of an Ethernet frame is applied to a ring node device - Google Patents

Abstract

To transfer an Ether frame through a ring network and achieve handover.SOLUTION: When a packet from a mobile terminal reaches a device of addition, drop and passage of a packet of a ring network, a bit 1 is stored at first and second bit positions in a storage area at an address position of SRAM accessed by a low-order address of a transmission source MAC address of the packet, and the bit 1 is stored at third and fourth bit positions in the storage area of the address position of the SRAM accessed by an intermediate address of the transmission source MAC address of the packet. When the packet is delivered to and reaches a counterclockwise ring, the bit 1 is stored at the first and second bit positions, and when the bit 1 is stored at the third and fourth bit positions, the transmission source MAC address of the packet is stored in an address table specifying the passage of the packet, and the packet is directed to a server by the counterclockwise ring.SELECTED DRAWING: Figure 1

Description

The present invention relates to a handover method for a mobile terminal using a ring network that transfers Ethernet frames, in which a MAC address storage method that stores bit 1 in both memory storage areas accessed by the lower address and intermediate address of the source MAC address of an Ethernet frame is applied to a ring node device. The present invention uses an Ethernet frame and a packet that uses the MAC address portion of the IPv6 address as the MAC address of the MAC packet.

A conventional example of an address storage method is Japanese Patent Application Laid-Open No. 2000-151617 "Table Creation and Search Device". This conventional example is related to a storage circuit for MAC addresses, and is composed of a first table made up of a RAM or the like having a row and column address, a MAC address data area, and an index area, and a second table made up of a RAM or the like having a row and column address, a MAC address data area, and an index area. This conventional example stores the entire 48 bits of a MAC address at position A, which is specified in the memory of the first table by a lower bit string (for example, 16 bits). If another MAC address is already stored at 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.

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 of storing multiple MAC addresses at the same address position in an entry table specified by a low-order bit string. If there is no free area, 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.

A typical conventional example of a ring-type network is a ring network using a master switch and a slave switch, as described in Patent Document 3. In this ring network, one of the ring ports of the master switch is a blocked port that does not allow frames to pass, preventing congestion due to flooding. When a fault occurs in the ring network, the monitoring frame that leaves the master switch and returns to the master switch is no longer delivered, and instead a fault notification frame is delivered to the master switch from the slave switch at the fault point, so the master switch unblocks the blocked port of the master switch to allow the frame to pass. In addition, a blocked port is set on the side of the faulty transmission path of one of the slave switches at the fault point, and the ring network continues to operate even after the fault is recovered from.
Generally, in a conventional ring network, a MAC address table is used in the ring node device, so that in the event of a transmission line fault, the FDBs of all ring node devices in the ring are cleared and the FDBs are reconstructed by flooding.

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 and an IPv6 connection via a destination base station between a mobile terminal and an access router, and reduces the interruption time of packets via the connection when switching connections.

Non-Patent Document 2 describes a fast handover for Mobile IPv6. This is a method that uses FBU (Fast Binding Update) between the old access router and the mobile terminal to transmit the CoA (care of address) to the Internet terminal and enables movement to a new access router.

An example of a mobile network that applies handover is Non-Patent Document 3. This is a network that uses a ring as the core network and distributes home agents to each node of the ring.

JP 2000-151617 A JP 2004-15592 A Re-table No. 2008-068813 Re-table No. 2017-195497

G.8032 “Ethernet Ring Protection Swithing” RFC4260, “Mobile IPv6 Fast handovers for 802.11 networks,” Website, https://datatracker.org/doc/html/rfc4260 H. Yokota et. Al, “Study on Decentralized Micro-mobility Magement for Large-scale Mobile Networks,” Journal of information Processing(JIP), Vol. 47 No.4, pp1239-1247, Apr. 2006. (in Japanese)

The conventional address storage method disclosed in JP 2000-151617 uses nesting to store MAC addresses, which can result in a long time required to trace the stored address using the address stored in the index.

Furthermore, the conventional address storage method described in Japanese Patent Application Laid-Open No. 2004-15592 describes that if there is no space in the entry table position of the MAC address specified by the lower bit string, the MAC address will be stored in the entry table position of a different lower bit string. In that case, however, when selecting the position to store the MAC address, it is necessary to search the entry table positions specified by two lower bit strings, and since there are multiple, discrete lower memory addresses at the same intermediate address position in the same entry table, it is necessary to compare all of these multiple lower memory addresses, which results in a problem of long search times.

The conventional ring networks in Non-Patent Document 1 and Patent Document 3 store the destination MAC addresses of packets bound for the left-handed ring, the destination MAC addresses of packets bound for the right-handed ring, and the destination MAC addresses of packets sent outside the ring as MAC addresses and port numbers, which causes the problem of a large number of MAC addresses being stored. In addition, when the MAC address table stores the entire 48 bits of the MAC address at the address position accessed by the memory using the lower address of the MAC address, or when the upper address is stored, if the MAC address cannot be stored, there is a drawback in that the destination MAC address of the packet to be transferred is not stored in the MAC address table (in the case of an unknown packet), and the packet is flooded.

In addition, in a conventional ring network, when searching for a connection destination, 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 it is desired to store the source MAC address of a packet in an address table that specifies the passage of the packet so that a reverse packet can pass through a node device that stores a lower address equal to the lower address of the source MAC address, the above storage process is not possible because the lower address of the destination MAC address does not indicate when the packet will arrive at the destination. If the destination address is a fixed MAC address, such as a server, it can be reached using the destination MAC address, but there is a problem that the device scale becomes large for terminals with many destinations.

In addition, the conventional handover technique disclosed in Patent Document 4 involves setting up and switching between two IPv4 or IPv6 connections between the access router and the mobile terminal, which requires identification of two IP connections, resulting in complex handover control.

Non-Patent Document 2 achieves handover by transferring the FBU from the old access router to the new access router, but since a router is used for handover and waiting takes place at the router, there is a problem of large delay times.

In addition, Non-Patent Document 3 distributes the load of location registration by distributing home agents, but distributing home agents poses the problem of requiring an IP prefix address for each one. When moving between base stations within a ring node, the IP prefix does not change, but when changing base stations, the IP prefix must be changed due to the Care of Address (CoA), which is a problem that cannot be handled with 64-bit host addresses alone. When moving between ring nodes, the IP prefix naturally changes. Introducing IP addresses into the ring poses the problem of making it impossible to transfer Ethernet frames within one domain using MAC addresses.

The objective of this invention is to show a method for achieving simple handover without using conventional MAC address tables, by using a ring network in which the ring node device uses memory that stores the lower address and intermediate address of the MAC address in one bit.

The present invention has been made in consideration of the above problems in the prior art, and the means for solving the problems are as follows: first to eighth aspects of the present invention.
A first aspect of the present invention is a system which inserts a plurality of packet add, drop and pass devices into a ring network of a clockwise ring transmission path 2 and a counterclockwise ring transmission path 1, connects a base station to the packet add, drop and pass devices, and enables handover of a mobile terminal under the base station, and which has a function of receiving packets arriving from the counterclockwise ring of the ring network and transferring them to a router and a function of blocking the passage of packets having a NIC MAC address of a ring network interface of the router as a source MAC address, and which transmits packets from the mobile terminal to a destination server via a router connected to the ring node device (hereinafter referred to as a vertex device) on the ring network as TCP or UDP Ethernet frames between the router and the server or the switch as IP packets, via the ring network, for communication of download services, video lectures, video conferences involving speech signals or content distribution with the destination server, or for voice communication with a switch,
Immediately before the mobile terminal accesses a destination base station, it sends a MAC address authentication packet transmission request packet to the source base station of the mobile terminal, the source base station checks the MAC address of the mobile terminal in a MAC address table, then erases the MAC address from the MAC address table, and sends the MAC address authentication packet of the mobile terminal to the destination base station, and when the packet arrives at a packet add, drop and pass-through device connected to the source base station, it erases bit 1 from the first bit of the storage area at the specified address position of the memory accessed by the lower address and intermediate address, which is accessed by the lower address of the MAC address of the mobile terminal, and the second bit position of the parity, and means for erasing a bit 1 and its even parity in the fourth bit position of a memory area of an address location, when the packet arrives at a packet add, drop and pass-through device connected to a destination base station of the mobile terminal, storing a bit 1 in the first bit and the second bit position of the parity in a memory area of a specified address location of a memory accessed by a lower address and an intermediate address, which is accessed by a lower address of the MAC address of the mobile terminal, and storing a bit 1 and its even parity in the third bit position and the fourth bit position of the memory area of an address location of the memory accessed by an intermediate address of the source MAC address of the packet, and transmitting a mobility preparation packet having the MAC address of the mobile terminal as a destination MAC address to a clockwise ring;
or
means for transmitting a movement preparation packet having the MAC address of the packet as a destination MAC address to the clockwise ring when a packet from the mobile terminal immediately after changing a destination base station arrives at a packet add, drop and pass-through device of the ring network, or when bit 1 is not stored in the first and second bit positions of a storage area of a designated address position of a memory accessed by a lower address and an intermediate address, which is accessed by a lower address of a source MAC address of a packet that has arrived from outside the ring at a packet add, drop and pass-through device of the ring network, and bit 1 is not stored in the third and fourth bit positions of a storage area of an address position of the memory accessed by an intermediate address of the source MAC address of the packet;
when a packet from the mobile terminal arrives at a packet add, drop and pass-through device of the ring network, whether the packet is a packet immediately after a change of destination base station or not, store a bit 1 in the first and second bit positions of a storage area of a designated address position of a memory accessed by a lower address and an intermediate address, which is accessed by a lower address of the source MAC address of the packet, and store a bit 1 in the third and fourth bit positions of a storage area of a designated address position of the memory, which is accessed by an intermediate address of the source MAC address of the packet, and send the packet to a counterclockwise ring;
When the packet arrives at a packet add, drop, or pass-through device,
means for storing the source MAC address of the packet in an address table that specifies the passage of the packet, and directing the packet on a counterclockwise ring to a vertex device in which the ring network interface NIC MAC address of a router to which a server or an exchange is connected via a router is stored as the destination MAC address of the packet, when a bit 1 is stored in the first and second bit positions of a storage area of a designated address position of the memory that is accessed by a lower address and an intermediate address and is accessed by a lower address of the source MAC address of the packet, and a bit 1 is stored in the third and fourth bit positions of a storage area of an address position of the memory that is accessed by an intermediate address of the source MAC address of the packet;
When a packet from a server or a switch is sent to the clockwise ring from a vertex device in which the NIC MAC address of the router is stored as the source MAC address of the packet via a router, and the packet arrives at a packet add, drop, or pass-through device,
means for transmitting the packet forward in a clockwise direction when the destination MAC address of the packet is stored in an address table that specifies the passage of the packet, transmitting the packet out of the ring when the destination MAC address of the packet is not stored in the address table that specifies the passage of the packet and when a bit 1 is stored in the first and second bit positions of a storage area of a designated address position of a memory accessed by a lower address and an intermediate address that is accessed by a lower address of the destination MAC address of the packet and when a bit 1 is stored in the third and fourth bit positions of a storage area of a designated address position of the memory accessed by an intermediate address of the destination MAC address of the packet, and transmitting the packet forward in a clockwise direction in other cases,
When the base station receives a mobility preparation packet from the ring network, and the destination MAC address of the packet is not stored in the MAC address table, and a MAC address with the same lower address as the lower address of the destination MAC address of the packet is stored in the MAC address table, the base station sends a mobility preparation packet having the MAC address stored in the MAC address table as its source MAC address from the immediately upstream packet add, drop and pass through device to the counterclockwise ring, and when the packet arrives at the packet add, drop and pass through device:
The system further comprises a means for storing the source MAC address of the packet in an address table that specifies the passage of the packet when bit 1 is stored in the first and second bit positions of a storage area of a specified address position of the memory that is accessed by a lower address and an intermediate address and that is accessed by a lower address of the source MAC address of the packet, and when bit 1 is stored in the third and fourth bit positions of a storage area of an address position of the memory that is accessed by an intermediate address of the source MAC address of the packet.

A second aspect of the present invention provides a system according to the first aspect of the present invention, comprising:
The system is characterized in that the number n of MAC addresses required to be stored in the address table specifying the passage of the packet is given by n = B * (A + (A/EXP((24-S)ln2)) * (A/EXP(Sln2)))/EXP(24ln2), where A is the number of packet terminals to be added to the ring, B is the number of packet terminals to be transferred on the ring, and S (<24) bits is the number of memory access bits.

A third aspect of the present invention provides a system according to the first aspect of the present invention, comprising:
The router has a home agent (HA) function and a CoA (Care of Address) termination function, and transfers data from the mobile terminal to the router via a base station and a ring network using an Ethernet frame of one domain, with the IP address remaining unchanged during this time due to a tunnel within the MAC address.

A fourth aspect of the present invention provides a system according to the first aspect of the present invention, comprising:
This system is characterized in that a domestic IPv4 address is used between the router and the exchange without using a NAT.

A fifth aspect of the present invention provides a system according to the first aspect of the present invention, comprising:
When the MAC address authentication packet arrives at the destination base station of the mobile terminal, the MAC address of the mobile terminal is stored in a MAC address table, and a mobility preparation packet having the MAC address of the mobile terminal as a destination MAC address is sent to the clockwise ring a plurality of times from a packet add, drop and pass device connected to the destination base station,
The system is characterized by comprising a means for setting up a radio channel to the mobile terminal and storing packets destined for the mobile terminal until a radio channel reception preparation OK signal is received from the mobile terminal.

A sixth aspect of the present invention provides a system according to the first aspect of the present invention, comprising:
The system is characterized in that the mobile terminal further comprises means for periodically accessing a receiving mail server and, if a response packet cannot be received from the receiving mail server, sending a retransmission packet to the receiving mail server.

A seventh aspect of the present invention is a method for enabling handover of a mobile terminal, comprising: inserting a plurality of packet add, drop and pass devices into a ring network of a clockwise ring transmission path 2 and a counterclockwise ring transmission path 1; connecting a base station to the packet add, drop and pass devices; and allowing a mobile terminal under the base station to receive packets arriving from the counterclockwise ring of the ring network and forward them to a router and to block the passage of packets having a NIC MAC address of a ring network interface of the router as a source MAC address, the method comprising: transmitting packets from the mobile terminal to and from the router as TCP or UDP Ethernet frames across the ring network and transmitting packets between the router and the server or the switch as IP packets, the method comprising the steps of:
Immediately before the mobile terminal accesses a destination base station, it sends a MAC address authentication packet transmission request packet to the source base station of the mobile terminal, the source base station checks the MAC address of the mobile terminal in a MAC address table, then erases the MAC address from the MAC address table, sends the MAC address authentication packet of the mobile terminal to the destination base station, and when the packet arrives at a packet add, drop and pass-through device connected to the source base station, it erases bit 1 from the first bit of the storage area at the specified address position of the memory accessed by the lower address and intermediate address, which is accessed by the lower address of the MAC address of the mobile terminal, and the second bit position of the parity, and a step of erasing a bit 1 and its even parity in the fourth bit position of a memory area of a designated address position, when the packet arrives at a packet add, drop and pass-through device connected to a destination base station of the mobile terminal, storing a bit 1 in the first bit and the second bit position of the parity in a memory area of a designated address position of a memory accessed by a lower address and an intermediate address, which is accessed by a lower address of the MAC address of the mobile terminal, and storing a bit 1 and its even parity in the third bit position and the fourth bit position of the memory area of an address position of the memory accessed by an intermediate address of the source MAC address of the packet, and sending a mobility preparation packet having the MAC address of the mobile terminal as a destination MAC address to the clockwise ring;
or
sending a movement preparation packet having the MAC address of the packet as a destination MAC address to the clockwise ring when a packet from the mobile terminal immediately after changing a destination base station arrives at a packet add, drop and pass-through device of the ring network, or when a bit 1 is not stored in the first and second bit positions of a storage area of a designated address position of a memory accessed by a lower address and an intermediate address, which is accessed by a lower address of a source MAC address of a packet that has arrived at a packet add, drop and pass-through device of the ring network from outside the ring, and when a bit 1 is not stored in the third and fourth bit positions of a storage area of an address position of the memory accessed by an intermediate address of the source MAC address of the packet;
when a packet from the mobile terminal arrives at a packet add, drop and pass-through device of the ring network, whether the packet is a packet immediately after a change of destination base station or not, store a bit 1 in the first and second bit positions of a storage area of a designated address position of a memory accessed by a lower address and an intermediate address, which is accessed by a lower address of the source MAC address of the packet, and store a bit 1 in the third and fourth bit positions of a storage area of a designated address position of the memory, which is accessed by an intermediate address of the source MAC address of the packet, and send the packet to a counterclockwise ring;
When the packet arrives at a packet add, drop, or pass-through device,
when a bit 1 is stored in the first and second bit positions of a storage area of a designated address position of a memory accessed by a lower address and an intermediate address, which is accessed by a lower address of the source MAC address of the packet, and a bit 1 is stored in the third and fourth bit positions of a storage area of an address position of the memory accessed by an intermediate address of the source MAC address of the packet, storing the source MAC address of the packet in an address table that specifies the passage of the packet, and directing the packet on a counterclockwise ring to a vertex device in which a ring network interface NIC MAC address of a router to which a server or an exchange is connected via a router is stored as a destination MAC address of the packet;
When a packet from a server or a switch is sent to the clockwise ring from a vertex device in which the NIC MAC address of the router is stored as the source MAC address of the packet via a router, and the packet arrives at a packet add, drop, or pass-through device,
sending the packet forward in the clockwise ring when the destination MAC address of the packet is stored in an address table that specifies the passage of the packet, sending the packet out of the ring when the destination MAC address of the packet is not stored in the address table that specifies the passage of the packet and when a bit 1 is stored in the first and second bit positions of a storage area of a designated address position of a memory accessed by a lower address and an intermediate address that is accessed by a lower address of the destination MAC address of the packet and when a bit 1 is stored in the third and fourth bit positions of a storage area of a designated address position of the memory accessed by an intermediate address of the destination MAC address of the packet, and sending the packet forward in the clockwise ring in other cases;
When the base station receives a mobility preparation packet from the ring network, and the destination MAC address of the packet is not stored in the MAC address table, and a MAC address with the same lower address as the lower address of the destination MAC address of the packet is stored in the MAC address table, the base station sends a mobility preparation packet having the MAC address stored in the MAC address table as its source MAC address from the immediately upstream packet add, drop and pass through device to the counterclockwise ring, and when the packet arrives at the packet add, drop and pass through device:
The method further comprises a step of storing the source MAC address of the packet in an address table that specifies the passage of the packet when bit 1 is stored in the first and second bit positions of a storage area of a specified address position of the memory that is accessed by a lower address and an intermediate address and that is accessed by a lower address of the source MAC address of the packet, and when bit 1 is stored in the third and fourth bit positions of a storage area of an address position of the memory that is accessed by an intermediate address of the source MAC address of the packet.

An eighth aspect of the present invention relates to a method according to the seventh aspect of the present invention, comprising:
The method further comprises a step in which the mobile terminal periodically accesses the receiving mail server, and if it cannot receive a response packet from the receiving mail server, sends a retransmission packet to the receiving mail server.

As described above, the present invention allows the mobile core network and subscriber network to be configured as one ring network, and uses SRAMs for lower addresses and intermediate address designation memory for designating packet transmission outside the ring instead of a MAC address table, making operation simple and fast, and allowing a ring node device (device for adding, dropping and passing packets) to be realized with two SRAMs, resulting in reduced system costs. The present invention also has the advantage that one-way UDP download is possible. The present invention also has the advantage that handover of a mobile terminal can be realized within one domain by a ring network using the above memory, resulting in reduced power consumption and system costs, and high-speed communication.

FIG. 1 is a diagram for explaining an example of handover operation of a mobile terminal in a packet forwarding system between a mobile terminal that forwards MAC packets through a base station connected to the packet add, drop and pass device of a dual ring network having an SRAM for lower address and intermediate address designation memory for designating packet transmission outside the ring and an address table for designating packet passing according to a first embodiment of the present invention, the mobile terminal forwarding MAC packets through a base station connected to the packet add, drop and pass device of the dual ring network having a shape like a flattened inflated balloon at each end like a fiord (Norwegian word) in which multiple rings are connected by optical rings, and a server connected to the ring network via a router. FIG. 2 is a diagram for explaining an example of handover operation of a mobile terminal in a packet forwarding system between a mobile terminal that forwards MAC packets through a base station connected to the packet add, drop and pass device in a dual ring network in which multiple devices are connected by an optical ring, the mobile terminal forwarding MAC packets through a base station connected to the packet add, drop and pass device, and a server connected to the ring network via a router, in a packet forwarding system according to a second embodiment of the present invention. An example of an operation flow diagram of a packet adding, dropping and passing device according to the first embodiment of the present invention. An example of an operation flow diagram of a packet adding, dropping and passing device according to the first embodiment of the present invention.

The first embodiment of the present invention will be described with reference to FIG. 1. In this embodiment, a wireless base station is connected to the packet add, drop and pass-through devices of a double ring network, each of which has an SRAM for lower addresses and intermediate address designation memory that designate packet transmission outside the ring, and an address table that designates packet passage, and each end of the device resembles a flattened inflated balloon, with optical transmission paths connecting the devices. A mobile terminal under the wireless base station transfers information as a MAC packet to a router connected to the ring network, and this is an example of the handover operation of a TCP packet or a voice packet of a mobile terminal using a ring network in a packet transfer system between a server connected to the ring network via the router, or between a switch. This system is also capable of one-way UDP downloads. The server is a mail receiving server or an Internet connection server.

In Fig. 1, 1 is an optical transmission line of a counterclockwise ring, 2 is an optical transmission line of a clockwise ring, 6-1, 6-2, and 6-3 are devices (ring node devices) for adding, dropping, and passing packets, 5 is a vertex device, 8 is an address table specifying the passing of packets, 11 is an SRAM for lower addresses and intermediate address specification memory specifying packet transmission outside the ring, 13-1, 13-2, and 13-3 are mobile terminals, 14-1, 14-2, and 14-3 are wireless base stations (BS), 20 is a server, 22 is a home agent (HA) and a router with a NAT function for Internet connection, 26 is a switch, and 27 is a home memory. Also, (1) to (32) indicate the transfer order of packets, which are abbreviated by letter symbols for MAC addresses transferred through the ring indicated by the dotted lead line, and I0, I1, I2, I3, and I7 are global IPv4 addresses dynamically set as IP addresses in the terminals, or domestic IPv4 addresses of service providers. Or IPv6 addresses. The ring node devices 6-1, 6-2, 6-3 and apex devices of the ring network operate at layer 2, but may have layer 3 switch functions for monitoring, etc. In the case of one ring, the ring node devices can be monitored by wire and do not require ARP functions, so IP addresses are not required and device numbers can be used.
The OE conversion circuit, EO conversion circuit, input buffer, and output buffer are not shown in the figure.

The operation of FIG. 1 will be explained below. An example is shown in which mobile terminal 13-2 for voice transmission has sent packet (1) Mn1r1r2γβα(I7) (M indicates an Ethernet packet, n1 indicates the wireless MAC address of base station 14-1, r1r2 indicates the NIC MAC address of the ring network interface of router 22, γβα indicates the upper MAC address γ, the intermediate MAC address β, and the lower MAC address α, which are the MAC addresses of mobile terminal 13-2, and I7 indicates the IP address of the destination exchange) to base station 14-1. The above Ethernet frame (2) Mr1r2γβα(I0) ( When the packet from the mobile terminal 13-2 arrives at the add, drop and pass device 6-1, the lower address and intermediate address designation memory of the SRAM (11) stores bit 1 in the first bit and bit 1 in the second bit as the even parity of the first bit in the storage area of the address position of the SRAM (11) for the lower address and intermediate address designation memory that designates packet transmission outside the ring, which is accessed by the lower address α (e.g., the 1st bit to the 17th bit) of the source MAC address of the packet, and stores bit 1 in the second bit as the intermediate address β (e.g., the 18th bit A bit 1 is stored in the third bit of the memory area of the address position of the SRAM (11) for the lower address and intermediate address designation memory that designates packet transmission outside the ring accessed by the address (bits 1 to 34 are treated as memory access address bits 1 to 17), and bit 1 is stored in the fourth bit as the even parity of the third bit, and the packet is sent to the vertex device 5 (a device for adding, dropping, and passing packets) whose address table 12 stores the NICMAC address of the upper ring network interface of the router 22 that connects to the server 20 via the currently used optical transmission line 1 of the counterclockwise ring.

When the packet is forwarded by (3) Mr1r2γβα (I7) on counterclockwise ring 1 as shown in the figure and arrives at device 6-2 for adding, dropping, and passing packets, bit 1 is stored in the first and second bits of the memory area of the address location of SRAM (11) for lower address and intermediate address designation memory that specifies packet sending outside the ring accessed by lower address α (e.g., bits 1 to 17) of the source MAC address of the packet, and bit 1 is stored in the first and second bits of the memory area of the address location of SRAM (11) for lower address and intermediate address designation memory that specifies packet sending outside the ring accessed by intermediate address β (e.g., bits 18 to 34 are the memory access address bits 1 to 17) of the source MAC address of the packet. When bit 1 is stored in the third and fourth bits of the memory area of the address position of the SRAM (11) for the lower address and intermediate address specification memory specifying the source MAC address of the packet, the source MAC address of the packet is stored in the address table specifying the passage of the packet. However, in this case, since it is not stored, the packet is sent directly to the vertex device 5 on the counterclockwise ring 1, and when the packet arrives at the device for adding, dropping and passing the packet (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 as (6) Mr1r2γβα (I7) toward the router 22 outside the ring. When the packet arrives at router 22, the source MAC address (γβα) and IP address (I3) of the packet are stored in an ARP table (not shown), or the source MAC address (γβα) is placed in the options field of the IP header, and the IP packet is forwarded as shown in the figure by (7) IPI3I7 (IP indicates an IP address, I3 indicates the IP address of mobile terminal 13-2, and I7 indicates the IP address of destination exchange 26), and reaches exchange 26.

Next, when the mobile terminal 13-1 receiving the mail receiving service sends a packet (9) Mr1r2δβα(I0) (M indicates an Ethernet packet, r1r2 indicates the NIC MAC address of the ring network interface of the router 22, δβα indicates the upper MAC address δ, the intermediate MAC address β, and the lower MAC address α, which are the MAC addresses of the terminal device (e.g., a mobile terminal) 13-1, and I0 indicates the IP address of the destination mail receiving server 20 (a server that can be reached without using NAT)) to the device 6-1 for adding, dropping, and passing the packet via the base station 14-1, the address position of the lower address and intermediate address designation memory that designates the packet sending outside the ring, which is accessed by the lower address α of the source MAC address of the packet, is recorded. A bit 1 is stored in the first bit of the memory area, a bit 1 is stored in the second bit as the even parity of the first bit, a bit 1 is stored in the third bit of the memory area of the address position of the SRAM (11) for the lower address and intermediate address designation memory that designates packet transmission outside the ring accessed by the intermediate address β of the source MAC address of the packet, a bit 1 is stored in the fourth bit as the even parity of the third bit, and the packet is sent to the address table 12 in which the NICMAC address of the ring network interface of the router 22 that connects to the server 20 or the switch 26 via the current optical transmission line 1 of the counterclockwise ring is stored.

When the packet is forwarded by (10) Mr1r2δβα (I0) on counterclockwise ring 1 as shown in the figure and arrives at device 6-2 for adding, dropping, and passing packets, bit 1 is stored in the first and second bits of the address location memory area of SRAM (11) for lower addresses and intermediate address designation memory that specify packet sending outside the ring, which is accessed by the lower address α (e.g., bits 1 to 17) of the source MAC address of the packet, and the intermediate address β (e.g., bits 18 to 34 of the memory) of the source MAC address of the packet is stored in the first and second bits of the address location memory area of SRAM (11). In this case, if bit 1 is not stored in the third and fourth bits of the address location storage area of the SRAM (11) for the lower address and intermediate address specification memory that specifies packet transmission outside the ring accessed by the access address (the first to seventeenth bits of the access address), the packet passes through the device 6-2 as is, and when it arrives at the vertex device 5 where 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 (13) Mr1r2δβα(I0) toward the router 22 outside the ring. When the packet arrives at router 22, the source MAC address (δβα) and IP address (I2) of the packet are stored in an ARP table (not shown), or the source MAC address (δβα) is placed in the options field of the IP header, and the IP packet is forwarded as shown in the figure by (14) IPI2I0 (IP indicates an IP address, I2 indicates the IP address of mobile terminal 13-1, and I0 indicates the IP address of the destination server 20), and reaches server 20.

Next, an example will be shown in which the mobile terminal 13-2 moves from the base station 14-1 to the base station 14-2.
When a packet (15) Mn2γβα (I7) (n2 indicates the wireless NIC MAC address of the base station 14-2, and γβα indicates the MAC address (upper address γ, middle address β, lower address α)) from the mobile terminal 13-2 arrives at the base station 14-2, the packet is a packet immediately after the destination base station is changed when the packet add, drop and pass device 6-2 connected to the destination base station is a device that connects to a base station approaching the server 20 on the counterclockwise ring 1. Therefore, when the packet arrives at the packet add, drop and pass device 6-2 as (16) Mr1r2γβα (I7), the packet is sent to the outside of the ring accessed by the lower address α of the source MAC address of the packet. bit 1 is stored in the first bit of the storage area of the address location of the SRAM (11) for the lower address and intermediate address specification memory specifying packet transmission of the packet, and bit 1 is stored in the second bit as the even parity of the first bit, bit 1 is stored in the third bit of the storage area of the address location of the SRAM (11) for the lower address and intermediate address specification memory specifying packet transmission outside the ring accessed by the intermediate address β of the source MAC address of the packet, and bit 1 is stored in the fourth bit as the even parity of the third bit, and at the same time, a move preparation packet (17) Mγβαr1r2 () having the source MAC address of the packet as the destination MAC address is sent to the clockwise ring 2. When the packet arrives at packet add, drop, and pass device 6-1, the destination MAC address γβα of the packet is not stored in address table 8 that specifies the passing of the packet, and bit 1 is stored in the first and second bits of the storage area of the address position of SRAM (11) for lower addresses and intermediate address designation memory that specifies the sending of the packet outside the ring and is accessed by the lower address α (e.g., the 1st to 17th bits) of the destination MAC address of the packet, and bit 1 is stored in the third and fourth bits of the storage area of the address position of SRAM (11) for lower addresses and intermediate address designation memory that specifies the sending of the packet outside the ring and is accessed by the intermediate address β of the source MAC address of the packet (e.g., the 1st to 17th bits of the memory access address are taken as the 1st to 17th bits of the memory access address). Therefore, the packet is sent outside the ring. When the mobility response preparation packet (18) Mγβαr1r2 () arrives at base station 14-1, the destination MAC address γβα of the packet is not stored in a MAC address table not shown in the figure, and a MAC address δβα with the same lower address as the lower address a2 of the destination MAC address of the packet is stored in the MAC address table, so a mobility response packet (19) Mr1r2δβα (I0) with the MAC address δβα stored in the MAC address table as its source MAC address is sent to counterclockwise ring 1 via packet add, drop, and pass device 6-1. When the packet (20) Mr1r2δβα (I0) arrives at the packet add, drop, and pass device 6-2, a bit 1 is stored in the first and second bits of the memory area of the address position of the SRAM (11) for the lower address and intermediate address designation memory that designates packet transmission outside the ring and is accessed by the lower address α (e.g., the 1st to 17th bits) of the source MAC address of the packet, and a bit 1 is stored in the third and fourth bits of the memory area of the address position of the SRAM (11) for the lower address and intermediate address designation memory that designates packet transmission outside the ring and is accessed by the intermediate address β (e.g., the 18th to 34th bits are the 1st to 17th bits of the memory access address) of the source MAC address of the packet, so that the source MAC address δβα of the packet is stored in the address table 8 that designates the pass of the packet.

On the other hand, the packet (16) Mr1r2γβα (I7) is sent as (22) Mr1r2γβα (I7) to the address table 12 that stores the NICMAC address of the upper ring network interface of the router 22 that connects to the server 20 via the current optical transmission line 1 of the counterclockwise ring.

When the packet arrives at the packet add, drop and pass device (vertex device 5) on counterclockwise ring 1 as is, the packet's destination MAC address r1r2 is stored in the address table 12 for the router, so the packet is dropped from the ring as (24) Mr1r2γβα (I7) and headed for router 22 outside the ring.

When the packet arrives at router 22, the source MAC address (γβα) and IP address (I3) of the packet are stored in an ARP table (not shown), or the source MAC address (γβα) is placed in the options field of the IP header, and the IP packet is forwarded as shown in the figure by (25) IPI3I7 (IP indicates an IP address, I3 indicates the IP address of the terminal connected to terminal device 13-2, and I7 indicates the IP address of the destination exchange 26) and reaches server 20.

Next, when a response packet (26) 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) for the mail reception service from server 20 arrives at router 22, if the packet is an IPv6 address, the destination MAC address of the packet's destination IPv6 address I2 is copied from the MAC address portion of the destination IPv6 address, and the MAC packet (27) Mδβαr1r2(I2) used as the MAC header address of the MAC packet is sent to the packet add, drop and pass-through device (vertex device 5) of the ring network. If the packet is an IPv4 address, the destination MAC address δβα paired with the destination IP address I2 of the packet is found from an ARP table (not shown), and the MAC packet (27) Mδβαr1r2(I2) is sent to the packet add, drop, and pass device (vertex device 5) of the ring network, using the MAC address in the option field of the IP header as the destination MAC address of the MAC packet, or the MAC address in the option field of the IP header as the destination MAC address, and the source MAC address as the NIC MAC address r1r2 of the ring network interface of the router 22.

When the MAC packet (27) Mδβαr1r2 (I2) arrives at the device for adding, dropping, and passing packets (vertex device 5), the source MAC address of the packet is stored in the address table 12 for router connection, so the packet is sent to clockwise ring 2.

When packet (29) Mδβαr1r2 (I2) is transferred through clockwise ring 2 and arrives at packet add, drop, and pass-through device 6-2, the packet is sent to clockwise ring 2 because the destination MAC address δβα of the packet is stored in address table 8, which specifies the packet's pass-through.

When the packet (30) Mδβαr1r2 (I2) is transferred through the clockwise ring 2 and arrives at the packet add, drop, and pass-through device 6-1, the destination MAC address δβα of the packet is not stored in the address table 8 that specifies the pass-through of the packet, and bit 1 is stored in the first bit of the memory area of the address position of the SRAM (11) for the lower address and intermediate address designation memory that specifies the packet being sent outside the ring and is accessed by the lower address α of the destination MAC address of the packet, bit 1 is stored in the second bit as the even parity of the first bit, bit 1 is stored in the third bit of the memory area of the address position of the SRAM (11) for the lower address and intermediate address designation memory that specifies the packet being sent outside the ring and is accessed by the intermediate address β of the destination MAC address of the packet, and bit 1 is stored in the fourth bit as the even parity of the third bit, so the packet is sent outside the ring. When the packet arrives at base station 14-1, the destination MAC address of the packet is stored in a MAC address table (not shown), so the packet is headed to destination mobile terminal 13-1.

A second embodiment of the present invention will be described with reference to FIG. 2. In this embodiment, a wireless base station is connected to a packet add, drop and pass device of a double ring network, which is connected by an optical transmission line, and the packet add, drop and pass device has an SRAM for lower address and intermediate address designation memory that designates packet transmission outside the ring, and an address table that designates packet passage. A mobile terminal under the wireless base station transfers information as a MAC packet to a router connected to the ring network, and the packet transfer system between a server connected to the ring network via the router, or between a switch, is an example of a handover operation of a TCP packet or a voice packet of a mobile terminal using a ring network. This system is also capable of one-way UDP download. The server is a mail receiving server or an Internet connection server.

In Fig. 2, 1 is an optical transmission line of a counterclockwise ring, 2 is an optical transmission line of a clockwise ring, 6-1, 6-2, and 6-3 are devices (ring node devices) for adding, dropping, and passing packets, 5 is a vertex device, 8 is an address table specifying the passing of packets, 11 is an SRAM for lower addresses and intermediate address specification memory specifying packet transmission outside the ring, 13-1, 13-2, and 13-3 are mobile terminals, 14-1, 14-2, and 14-3 are wireless base stations (BS), 20 is a server, 22 is a home agent (HA), a router with a NAT function for Internet connection, 26 is a switch, and 27 is a home memory. Also, (1) to (36) indicate the transfer order of packets, which are abbreviated by letter symbols for MAC addresses transferred through the ring indicated by the dotted lead line, and I0, I1, I2, I3, and I7 are global IPv4 addresses dynamically set as IP addresses in the terminals, or domestic IPv4 addresses of service providers. Or IPv6 addresses. The ring node devices 6-1, 6-2, 6-3 and apex devices in the ring network operate at layer 2, but may have layer 3 switch functions for monitoring, etc. In the case of one ring, ring node devices can be monitored by wire and do not require ARP functions, so IP addresses are not required. When an IPv6 address is used for a base station, the prefix portion of the IPv6 address is the same within the ring, and the base station is identified only by the MAC address portion of the IPv6 address.
The OE conversion circuit, EO conversion circuit, input buffer, and output buffer are not shown in the figure.

The operation of FIG. 2 will be explained below. An example is shown in which mobile terminal 13-2 for voice transmission has sent packet (1) Mn1r1r2γβα(I7) (M indicates an Ethernet packet, n1 indicates the wireless MAC address of base station 14-1, r1r2 indicates the NIC MAC address of the ring network interface of router 22, γβα indicates the upper MAC address γ, the intermediate MAC address β, and the lower MAC address α, which are the MAC addresses of mobile terminal 13-2, and I7 indicates the IP address of the destination exchange) to base station 14-1. The above Ethernet frame (2) Mr1r2γβα(I0) ( When the packet from the mobile terminal 13-2 arrives at the add, drop and pass device 6-1, the lower address and intermediate address designation memory of the SRAM (11) stores bit 1 in the first bit and bit 1 in the second bit as the even parity of the first bit in the storage area of the address position of the SRAM (11) for the lower address and intermediate address designation memory that designates packet transmission outside the ring, which is accessed by the lower address α (e.g., the 1st bit to the 17th bit) of the source MAC address of the packet, and stores bit 1 in the second bit as the intermediate address β (e.g., the 18th bit A bit 1 is stored in the third bit of the memory area of the address position of the SRAM (11) for the lower address and intermediate address designation memory that designates packet transmission outside the ring accessed by the address (bits 1 to 34 are treated as memory access address bits 1 to 17), and bit 1 is stored in the fourth bit as the even parity of the third bit, and the packet is sent to the vertex device 5 (a device for adding, dropping, and passing packets) whose address table 12 stores the NICMAC address of the upper ring network interface of the router 22 that connects to the server 20 via the currently used optical transmission line 1 of the counterclockwise ring.

When the packet is forwarded by (3) Mr1r2γβα (I7) on counterclockwise ring 1 as shown in the figure and arrives at device 6-2 for adding, dropping, and passing packets, bit 1 is stored in the first and second bits of the memory area of the address location of SRAM (11) for lower address and intermediate address designation memory that specifies packet sending outside the ring accessed by lower address α (e.g., bits 1 to 17) of the source MAC address of the packet, and bit 1 is stored in the first and second bits of the memory area of the address location of SRAM (11) for lower address and intermediate address designation memory that specifies packet sending outside the ring accessed by intermediate address β (e.g., bits 18 to 34 are the memory access address bits 1 to 17) of the source MAC address of the packet. When bit 1 is stored in the third and fourth bits of the memory area of the address position of the SRAM (11) for the lower address and intermediate address specification memory specifying the source MAC address of the packet, the source MAC address of the packet is stored in the address table specifying the passage of the packet. However, in this case, since it is not stored, the packet is sent directly to the vertex device 5 on the counterclockwise ring 1, and when the packet arrives at the device for adding, dropping and passing the packet (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 as (6) Mr1r2γβα (I7) toward the router 22 outside the ring. When the packet arrives at router 22, the source MAC address (γβα) and IP address (I3) of the packet are stored in an ARP table (not shown), or the source MAC address (γβα) is placed in the options field of the IP header, and the IP packet is forwarded as shown in the figure by (7) IPI3I7 (IP indicates an IP address, I3 indicates the IP address of mobile terminal 13-2, and I7 indicates the IP address of destination exchange 26), and reaches exchange 26.

Next, when the mobile terminal 13-1 receiving the mail receiving service sends a packet (9) Mr1r2δβα(I0) (M indicates an Ethernet packet, r1r2 indicates the NIC MAC address of the ring network interface of the router 22, δβα indicates the upper MAC address δ, the intermediate MAC address β, and the lower MAC address α, which are the MAC addresses of the terminal device (e.g., a mobile terminal) 13-1, and I0 indicates the IP address of the destination mail receiving server 20 (a server that can be reached without using NAT)) to the device 6-1 for adding, dropping, and passing the packet via the base station 14-1, the address position of the lower address and intermediate address designation memory that designates the packet sending outside the ring, which is accessed by the lower address α of the source MAC address of the packet, is recorded. A bit 1 is stored in the first bit of the memory area, a bit 1 is stored in the second bit as the even parity of the first bit, a bit 1 is stored in the third bit of the memory area of the address position of the SRAM (11) for the lower address and intermediate address designation memory that designates packet transmission outside the ring accessed by the intermediate address β of the source MAC address of the packet, a bit 1 is stored in the fourth bit as the even parity of the third bit, and the packet is sent to the address table 12 in which the NICMAC address of the ring network interface of the router 22 that connects to the server 20 or the switch 26 via the current optical transmission line 1 of the counterclockwise ring is stored.

When the packet is forwarded by (10) Mr1r2δβα (I0) on counterclockwise ring 1 as shown in the figure and arrives at device 6-2 for adding, dropping, and passing packets, bit 1 is stored in the first and second bits of the address location memory area of SRAM (11) for lower addresses and intermediate address designation memory that specify packet sending outside the ring, which is accessed by the lower address α (e.g., bits 1 to 17) of the source MAC address of the packet, and the intermediate address β (e.g., bits 18 to 34 of the memory) of the source MAC address of the packet is stored in the first and second bits of the address location memory area of SRAM (11). In this case, if bit 1 is not stored in the third and fourth bits of the address location storage area of the SRAM (11) for the lower address and intermediate address specification memory that specifies packet transmission outside the ring accessed by the access address (the first to seventeenth bits of the access address), the packet passes through the device 6-2 as is, and when it arrives at the vertex device 5 where 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 (13) Mr1r2δβα(I0) toward the router 22 outside the ring. When the packet arrives at router 22, the source MAC address (δβα) and IP address (I2) of the packet are stored in an ARP table (not shown), or the source MAC address (δβα) is placed in the options field of the IP header, and the IP packet is forwarded as shown in the figure by (14) IPI2I0 (IP indicates an IP address, I2 indicates the IP address of mobile terminal 13-1, and I0 indicates the IP address of the destination server 20), and reaches server 20.

Next, an example will be shown in which the mobile terminal 13-2 moves from the base station 14-1 to the base station 14-2.
When a MAC authentication packet transmission request packet (15)Mn2γβα(I7) (n2 indicates the wireless NIC MAC address of base station 14-2, and γβα indicates the MAC address of mobile terminal 13-2 (upper address γ, intermediate address β, lower address α)) from the mobile terminal 13-2 arrives at the source base station 14-1, the source base station checks the MAC address of the mobile terminal 13-2 in a MAC address table (not shown), deletes the MAC address γβα from the MAC address table, and sends a MAC address authentication packet (16)MB2γβα() (B2 is the MAC address of base station 14-2) of the mobile terminal 13-2 to the destination base station 14-2. When the packet arrives at the packet add, drop and pass device 6-1, the device erases bits 1 through 1 of the memory area of the address location of the SRAM (11) for the lower address and intermediate address designation memory that designates packet transmission outside the ring and is accessed by the lower address α of the MAC address of the mobile terminal 13-2, erases bits 1 through 2 as the even parity of the first bit, and erases bits 1 through 3 of the memory area of the address location of the SRAM (11) for the lower address and intermediate address designation memory that designates packet transmission outside the ring and is accessed by the intermediate address β of the source MAC address of the packet, thereby determining whether the packet has been added, dropped or passed. When the packet arrives at the drop and pass-through device 6-2, a bit 1 is stored in the first bit of the memory area of the address position of SRAM (11) for the lower address and intermediate address designation memory that designates packet transmission outside the ring and is accessed by the lower address α of the MAC address of the mobile terminal 13-2, a bit 1 is stored in the second bit as the even parity of the first bit, and a bit 1 is stored in the third bit of the memory area of the address position of SRAM (11) for the lower address and intermediate address designation memory that designates packet transmission outside the ring and is accessed by the intermediate address β of the source MAC address of the packet, and the packet (18)MB2γβα() is sent to the destination base station 14-2. The destination base station 14-2 stores the MAC address γβα of the mobile terminal in a MAC address table (not shown) and sends a mobility preparation packet (19) Mγβαr1r2() with the MAC address γβα as the destination MAC address from the packet add, drop, and pass device 6-2 to the clockwise ring 2. When the packet (20) Mγβαr1r2 () arrives at the packet add, drop, and pass device 6-1, the destination MAC address γβα of the packet is not stored in the address table 8 that specifies the pass of the packet, and a bit 1 is stored in the first and second bits of the storage area of the address position of the SRAM (11) for the lower address and intermediate address designation memory that specifies the packet transmission outside the ring and is accessed by the lower address α (e.g., the 1st to 17th bits) of the destination MAC address of the packet, and a bit 1 is stored in the third and fourth bits of the storage area of the address position of the SRAM (11) for the lower address and intermediate address designation memory that specifies the packet transmission outside the ring and is accessed by the intermediate address β of the source MAC address of the packet (e.g., the 1st to 17th bits of the memory access address are the 1st to 17th bits of the memory access address). Therefore, the packet is sent outside the ring. When the mobility response preparation packet (21) Mγβαr1r2 () arrives at base station 14-1, the destination MAC address γβα of the packet is not stored in a MAC address table not shown in the figure, and a MAC address δβα with the same lower address as the lower address a2 of the destination MAC address of the packet is stored in the MAC address table, so a mobility response packet (22) Mr1r2δβα (I0) with the MAC address δβα stored in the MAC address table as its source MAC address is sent to counterclockwise ring 1 via packet add, drop, and pass device 6-1. When the packet (23) Mr1r2δβα (I0) arrives at the packet add, drop, and pass device 6-2, a bit 1 is stored in the first and second bits of the memory area of the address position of the SRAM (11) for the lower address and intermediate address designation memory that designates packet transmission outside the ring and is accessed by the lower address α (e.g., the first bit to the seventeenth bit) of the source MAC address of the packet, and a bit 1 is stored in the third and fourth bits of the memory area of the address position of the SRAM (11) for the lower address and intermediate address designation memory that designates packet transmission outside the ring and is accessed by the intermediate address β (e.g., the 18th bit to the 34th bit are the first bit to the 17th bit of the memory access address) of the source MAC address of the packet, so that the source MAC address δβα of the packet is stored in the address table 8 that designates the pass of the packet.

Next, when a packet (25) Mr1r2γβα (I7) from the mobile terminal 13-2 arrives at the packet add, drop and pass device 6-2, which is a device that connects to a base station on the counterclockwise ring 1 in the direction approaching the server 20, immediately after changing the destination base station, the device stores bit 1 in the first bit of the memory area of the address position of the SRAM (11) for the lower address and intermediate address designation memory that designates packet transmission outside the ring and is accessed with the lower address α of the source MAC address of the packet, stores bit 1 in the second bit as the even parity of the first bit, and stores bit 1 in the third bit of the memory area of the address position of the SRAM (11) for the lower address and intermediate address designation memory that designates packet transmission outside the ring and is accessed with the intermediate address β of the source MAC address of the packet.

The packet (25) Mr1r2γβα (I7) is sent as (26) Mr1r2γβα (I7) to the address table 12 that stores the NICMAC address of the upper ring network interface of the router 22 that connects to the server 20 via the current optical transmission path 1 of the counterclockwise ring.

When the packet arrives at the packet add, drop and pass device (vertex device 5) on counterclockwise ring 1 as is, the packet's destination MAC address r1r2 is stored in the address table 12 for the router, so the packet is dropped from the ring as (28) Mr1r2γβα (I7) and headed for router 22 outside the ring.

When the packet arrives at router 22, the source MAC address (γβα) and IP address (I3) of the packet are stored in an ARP table (not shown), or the source MAC address (γβα) is placed in the options field of the IP header, and the IP packet is forwarded as shown in the figure by (29) IPI3I7 (IP indicates an IP address, I3 indicates the IP address of the terminal connected to terminal device 13-2, and I7 indicates the IP address of the destination exchange 26) until it reaches exchange 26.

Next, when a response packet (30) 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) for the mail reception service from server 20 arrives at router 22, if the 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 the MAC packet (31) Mδβαr1r2 (I2) used as the MAC header address of the MAC packet is sent to the packet add, drop and pass-through device (vertex device 5) of the ring network. If the packet is an IPv4 address, the destination MAC address δβα paired with the destination IP address I2 of the packet is found from an ARP table (not shown), and the MAC packet (31) Mδβαr1r2(I2) is sent to the packet add, drop, and pass device (vertex device 5) of the ring network, using the MAC address in the MAC packet's destination MAC header address, or the MAC address in the option field of the IP header as the destination MAC address, and the source MAC address as the NIC MAC address r1r2 of the ring network interface of the router 22.

When the MAC packet (31) Mδβαr1r2 (I2) arrives at the device for adding, dropping, and passing packets (vertex device 5), the source MAC address of the packet is stored in the address table 12 for router connection, so the packet is sent to clockwise ring 2.

When packet (33) Mδβαr1r2 (I2) is transferred through clockwise ring 2 and arrives at packet add, drop, and pass-through device 6-2, the packet is sent to clockwise ring 2 because the destination MAC address δβα of the packet is stored in address table 8, which specifies the packet's pass-through.

When the packet (34) Mδβαr1r2 (I2) is transferred through the clockwise ring 2 and arrives at the packet add, drop and pass device 6-1, the destination MAC address δβα of the packet is not stored in the address table 8 that specifies the pass of the packet, and bit 1 is stored in the first bit of the memory area of the address position of the SRAM (11) for the lower address and intermediate address designation memory that specifies the packet being sent outside the ring and is accessed by the lower address α of the destination MAC address of the packet, and bit 1 is stored in the second bit as the even parity of the first bit, and bit 1 is stored in the third bit of the memory area of the address position of the SRAM (11) for the lower address and intermediate address designation memory that specifies the packet being sent outside the ring and is accessed by the intermediate address β of the destination MAC address of the packet, and bit 1 is stored in the fourth bit as the even parity of the third bit, so that the packet is sent outside the ring as (35) Mδβαr1r2 (I2). When the packet arrives at base station 14-1, the destination MAC address of the packet is stored in a MAC address table (not shown), so the packet is headed to destination mobile terminal 13-1.

Next, Fig. 3A and Fig. 3B show an example of an operation flow diagram of the device for adding, dropping and passing packets in the first embodiment. In Fig. 3A, 100 judges whether a packet has arrived from the clockwise ring, and if YES, 101 judges whether the destination MAC address of the received packet is stored in the address table specifying the passing of the packet, and if NO, 1 is stored in the first and second bits of the data storage area of the address position of the memory for packet dropping (SRAM for the lower address and intermediate address specification memory for specifying packet sending outside the ring) accessed by the lower address of the destination MAC address of the received packet in 102, and whether 1 is stored in the third and fourth bits of the data storage area of the address position of the memory for packet dropping accessed by the intermediate address of the destination MAC address of the received packet, and if YES, 103 sends the received packet out of the ring and returns to (a). If NO, 104 sends the received packet forward to the clockwise ring and returns to (a). If NO at 100, transition to (b). If the answer is YES at 101, the process transitions to 104.
In FIG. 3B, 105 judges whether a packet has arrived from the ADD line (wireless base station side), and if the judgment is Yes, 105 stores a bit 1 in the first and second bits of the data storage area of the address position of the packet dropping memory (SRAM for the lower address memory and intermediate address specification memory for specifying packet transmission outside the ring) accessed by the lower address of the source MAC address of the received packet of 106, stores a bit 1 in the third and fourth bits of the data storage area of the address position of the packet dropping memory accessed by the intermediate address of the source MAC address of the received packet, and if the received packet is a packet received immediately after a change of destination base station, sends a movement preparation corresponding packet with the source MAC address of the packet as the destination MAC to the clockwise ring and sends the received packet of 107 to the front of the counterclockwise ring, and returns to (a). If NO in 105, it is determined whether a packet has arrived from the counterclockwise ring in 108. If YES, it is determined whether bit 1 is stored in the first and second bits of the data storage area of the address position of the memory for packet drop (SRAM for the lower address memory and intermediate address designation memory for specifying packet transmission outside the ring) accessed by the lower address of the source MAC address of the received packet in 109, and whether bit 1 is stored in the third and fourth bits of the data storage area of the address position of the memory for packet drop accessed by the intermediate address of the source MAC address of the received packet. If YES, it is determined whether the source MAC address of the received packet in 110 is stored in the address table that specifies the passage of the packet, and the received packet in 111 is sent forward to the counterclockwise ring, and transition is made to (a). If NO in 108, it returns to (a). If NO in 109, it transitions to 111.

In the first embodiment, bit 1 is stored in the first and second bits of the memory area of an address position of an SRAM accessed by a ring node device with a lower address of the destination MAC address of a packet (bit 1 to bit 17 counting from the least significant bit of the destination MAC address), and bit 1 is stored in the third and fourth bits of the memory area of an address position of an SRAM accessed by an intermediate address of the destination MAC address of the packet (bit 18 to bit 34 counting from the least significant bit of the destination MAC address), and the issue is the number of MAC addresses required to be stored in the address table that specifies the passage of a packet of the ring node device. Incidentally, if the number of packet terminals to be ADDed to the ring is 10,000, the number of terminals to be transferred on the ring is 500,000, and the number of addressing bits in the SRAM is 17 bits, then 500,000*(10,000+(10,000/EXP(7ln2))*(10,000/EXP(17ln2)))/EXP(24ln2)=298, and if there are multiple NIC manufacturers, the number of MAC addresses required to be stored will be even smaller, so there will be no problem in implementing embodiment 1.
In addition, the method of using a 24-bit lower address memory may cause problems with skew and hazards in the logic circuit of the decoder ASIC. If a decoder memory is used to avoid this, it will be a ROM, which will slow down the operation. In addition, since the first embodiment can be configured using only existing memory, it is easy to introduce into a LAN.
The first embodiment is also capable of storing the source MAC address of the location registration packet.

In the first embodiment, if the mobile terminal cannot receive a response packet to an access packet to the receiving mail server of the mobile terminal, a retransmission packet is sent to the receiving mail server.

In the case of a ring failure in the first embodiment, it can be handled without flooding by steering or double-ring loopback. In the case of double-ring loopback, when a ring network failure occurs, the add, drop and pass devices of the packet on both sides of the failure point loop back, and when the loopback occurs, a loopback bit is added, and the packet with the loopback bit added passes through all the devices up to the second loopback point, and the loopback bit is removed at the second loopback.

1. Counterclockwise ring optical transmission line
2. Clockwise ring optical transmission path
5 Vertex devices 6-1, 6-2, 6-3 Packet add, drop and pass devices 8 Address table for specifying packet pass 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, 13-4 Mobile terminal 14-1, 14-2, 14-3 Base station (BS)
20 Server 22 Router 26 Switch

Claims (8)

A system in which a plurality of packet 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, a base station is connected to the packet add, drop and pass devices, and a mobile terminal under 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 a 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 ring network and the router as TCP or UDP Ethernet frames and between the router and the server or the switch as IP packets via the ring network connected to a ring node device (hereinafter referred to as a vertex device) on the ring network for communication with a destination server for download services, television lectures, video conferences involving speech signals or content distribution, or for voice communication with a switch, and which enables handover of the mobile terminal,
Immediately before the mobile terminal accesses a destination base station, it sends a MAC address authentication packet transmission request packet to the source base station of the mobile terminal, the source base station checks the MAC address of the mobile terminal in a MAC address table, then erases the MAC address from the MAC address table, and sends the MAC address authentication packet of the mobile terminal to the destination base station, and when the packet arrives at a packet add, drop and pass-through device connected to the source base station, it erases bit 1 from the first bit of the storage area at the specified address position of the memory accessed by the lower address and intermediate address, which is accessed by the lower address of the MAC address of the mobile terminal, and the second bit position of the parity, and means for erasing a bit 1 and its even parity in the fourth bit position of a memory area of an address location, when the packet arrives at a packet add, drop and pass-through device connected to a destination base station of the mobile terminal, storing a bit 1 in the first bit and the second bit position of the parity in a memory area of a specified address location of a memory accessed by a lower address and an intermediate address, which is accessed by a lower address of the MAC address of the mobile terminal, and storing a bit 1 and its even parity in the third bit position and the fourth bit position of the memory area of an address location of the memory accessed by an intermediate address of the source MAC address of the packet, and transmitting a mobility preparation packet having the MAC address of the mobile terminal as a destination MAC address to a clockwise ring;
or
means for transmitting a movement preparation packet having the MAC address of the packet as a destination MAC address to the clockwise ring when a packet from the mobile terminal immediately after changing a destination base station arrives at a packet add, drop and pass-through device of the ring network, or when bit 1 is not stored in the first and second bit positions of a storage area of a designated address position of a memory accessed by a lower address and an intermediate address, which is accessed by a lower address of a source MAC address of a packet that has arrived from outside the ring at a packet add, drop and pass-through device of the ring network, and bit 1 is not stored in the third and fourth bit positions of a storage area of an address position of the memory accessed by an intermediate address of the source MAC address of the packet;
when a packet from the mobile terminal arrives at a packet add, drop and pass-through device of the ring network, whether the packet is a packet immediately after a change of destination base station or not, store a bit 1 in the first and second bit positions of a storage area of a designated address position of a memory accessed by a lower address and an intermediate address, which is accessed by a lower address of the source MAC address of the packet, and store a bit 1 in the third and fourth bit positions of a storage area of a designated address position of the memory, which is accessed by an intermediate address of the source MAC address of the packet, and send the packet to a counterclockwise ring;
When the packet arrives at a packet add, drop, or pass-through device,
means for storing the source MAC address of the packet in an address table that specifies the passage of the packet, and directing the packet on a counterclockwise ring to a vertex device in which the ring network interface NIC MAC address of a router to which a server or an exchange is connected via a router is stored as the destination MAC address of the packet, when a bit 1 is stored in the first and second bit positions of a storage area of a designated address position of the memory that is accessed by a lower address and an intermediate address and is accessed by a lower address of the source MAC address of the packet, and a bit 1 is stored in the third and fourth bit positions of a storage area of an address position of the memory that is accessed by an intermediate address of the source MAC address of the packet;
When a packet from a server or a switch is sent to the clockwise ring from a vertex device in which the NIC MAC address of the router is stored as the source MAC address of the packet via a router, and the packet arrives at a packet add, drop, or pass-through device,
means for transmitting the packet forward in a clockwise direction when the destination MAC address of the packet is stored in an address table that specifies the passage of the packet, transmitting the packet out of the ring when the destination MAC address of the packet is not stored in the address table that specifies the passage of the packet and when a bit 1 is stored in the first and second bit positions of a storage area of a designated address position of a memory accessed by a lower address and an intermediate address that is accessed by a lower address of the destination MAC address of the packet and when a bit 1 is stored in the third and fourth bit positions of a storage area of a designated address position of the memory accessed by an intermediate address of the destination MAC address of the packet, and transmitting the packet forward in a clockwise direction in other cases,
When the base station receives a mobility preparation packet from the ring network, and the destination MAC address of the packet is not stored in the MAC address table, and a MAC address with the same lower address as the lower address of the destination MAC address of the packet is stored in the MAC address table, the base station sends a mobility preparation packet having the MAC address stored in the MAC address table as its source MAC address from the immediately upstream packet add, drop and pass through device to the counterclockwise ring, and when the packet arrives at the packet add, drop and pass through device:
The system further comprises a means for storing the source MAC address of the packet in an address table that specifies the passage of the packet when bit 1 is stored in the first and second bit positions of a storage area of a specified address position of the memory that is accessed by a lower address and an intermediate address and that is accessed by a lower address of the source MAC address of the packet, and when bit 1 is stored in the third and fourth bit positions of a storage area of an address position of the memory that is accessed by an intermediate address of the source MAC address of the packet.
The system described in claim 1, characterized in that the number n of MAC addresses required to be stored in the address table for specifying the passage of the packet is given by n = B * (A + (A/EXP((24-S)ln2))) * (A/EXP(Sln2)))/EXP(24ln2), where A is the number of packet terminals to be added to the ring, B is the number of packet terminals to be transferred on the ring, and S (<24) bits is the number of address bits to access the memory.
The system described in claim 1, characterized in that the router has a home agent (HA) function and a CoA (Care of Address) termination function, and transfers data from the mobile terminal to the router via a base station and a ring network using an Ethernet frame of one domain, during which the IP address does not change due to a tunnel within the MAC address.
2. The system according to claim 1, wherein a domestic IPv4 address is used between the router and the exchange without using a NAT.
When the MAC address authentication packet arrives at the destination base station of the mobile terminal, the MAC address of the mobile terminal is stored in a MAC address table, and a mobility preparation packet having the MAC address of the mobile terminal as a destination MAC address is sent to the clockwise ring a plurality of times from a packet add, drop and pass device connected to the destination base station,
2. The system according to claim 1, further comprising means for setting up a radio channel to the mobile terminal and storing packets destined for the mobile terminal until a radio channel reception preparation OK signal is received from the mobile terminal.
The system according to claim 1, characterized in that the mobile terminal further comprises means for periodically accessing the receiving mail server and, if it is unable to receive a response packet from the receiving mail server, sending a retransmission packet to the receiving mail server.
A method for enabling handover of a mobile terminal, comprising: inserting a plurality of packet add, drop and pass devices into a ring network of a clockwise ring transmission path 2 and a counterclockwise ring transmission path 1; connecting a base station to the packet add, drop and pass devices; and allowing a mobile terminal under the base station to communicate with a destination server via a router connected to a ring node device (hereinafter referred to as a vertex device) on the ring network, the ring node device having 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 a NIC MAC address of a ring network interface of the router as a source MAC address, for download services, television lectures, video conferences involving speech signals or content distribution, or for voice communication with an exchange, by transmitting packets from the mobile terminal between the mobile terminal and the router as TCP or UDP Ethernet frames across the ring network, and between the router and the server or exchange as IP packets;
Immediately before the mobile terminal accesses a destination base station, it sends a MAC address authentication packet transmission request packet to the source base station of the mobile terminal, and the source base station checks the MAC address of the mobile terminal in a MAC address table, then erases the MAC address from the MAC address table, and sends the MAC address authentication packet of the mobile terminal to the destination base station, and when the packet arrives at a packet add, drop and pass-through device connected to the source base station, it erases bit 1 from the first bit of the storage area at the specified address position of the memory accessed by the lower address and intermediate address, which is accessed by the lower address of the MAC address of the mobile terminal, and the second bit position of the parity, and a step of erasing a bit 1 and its even parity in the fourth bit position of a memory area of a designated address position, when the packet arrives at a packet add, drop and pass-through device connected to a destination base station of the mobile terminal, storing a bit 1 in the first bit and the second bit position of the parity in a memory area of a designated address position of a memory accessed by a lower address and an intermediate address, which is accessed by a lower address of the MAC address of the mobile terminal, and storing a bit 1 and its even parity in the third bit position and the fourth bit position of the memory area of an address position of the memory accessed by an intermediate address of the source MAC address of the packet, and sending a mobility preparation packet having the MAC address of the mobile terminal as a destination MAC address to the clockwise ring;
or
sending a movement preparation packet having the MAC address of the packet as a destination MAC address to the clockwise ring when a packet from the mobile terminal immediately after changing a destination base station arrives at a packet add, drop and pass-through device of the ring network, or when a bit 1 is not stored in the first and second bit positions of a storage area of a designated address position of a memory accessed by a lower address and an intermediate address, which is accessed by a lower address of a source MAC address of a packet that has arrived at a packet add, drop and pass-through device of the ring network from outside the ring, and when a bit 1 is not stored in the third and fourth bit positions of a storage area of an address position of the memory accessed by an intermediate address of the source MAC address of the packet;
when a packet from the mobile terminal arrives at a packet add, drop and pass-through device of the ring network, whether the packet is a packet immediately after a change of destination base station or not, store a bit 1 in the first and second bit positions of a storage area of a designated address position of a memory accessed by a lower address and an intermediate address, which is accessed by a lower address of the source MAC address of the packet, and store a bit 1 in the third and fourth bit positions of a storage area of a designated address position of the memory, which is accessed by an intermediate address of the source MAC address of the packet, and send the packet to a counterclockwise ring;
When the packet arrives at a packet add, drop, or pass-through device,
when a bit 1 is stored in the first and second bit positions of a storage area of a designated address position of a memory accessed by a lower address and an intermediate address, which is accessed by a lower address of the source MAC address of the packet, and a bit 1 is stored in the third and fourth bit positions of a storage area of an address position of the memory accessed by an intermediate address of the source MAC address of the packet, storing the source MAC address of the packet in an address table that specifies the passage of the packet, and directing the packet on a counterclockwise ring to a vertex device in which a ring network interface NIC MAC address of a router to which a server or an exchange is connected via a router is stored as a destination MAC address of the packet;
When a packet from a server or a switch is sent to the clockwise ring from a vertex device in which the NIC MAC address of the router is stored as the source MAC address of the packet via a router, and the packet arrives at a packet add, drop, or pass-through device,
sending the packet forward in the clockwise ring when the destination MAC address of the packet is stored in an address table that specifies the passage of the packet, sending the packet out of the ring when the destination MAC address of the packet is not stored in the address table that specifies the passage of the packet and when a bit 1 is stored in the first and second bit positions of a storage area of a designated address position of a memory accessed by a lower address and an intermediate address that is accessed by a lower address of the destination MAC address of the packet and when a bit 1 is stored in the third and fourth bit positions of a storage area of a designated address position of the memory accessed by an intermediate address of the destination MAC address of the packet, and sending the packet forward in the clockwise ring in other cases;
When the base station receives a mobility preparation packet from the ring network, and the destination MAC address of the packet is not stored in the MAC address table, and a MAC address with the same lower address as the lower address of the destination MAC address of the packet is stored in the MAC address table, the base station sends a mobility preparation packet having the MAC address stored in the MAC address table as its source MAC address from the immediately upstream packet add, drop and pass through device to the counterclockwise ring, and when the packet arrives at the packet add, drop and pass through device:
The method further comprises a step of storing the source MAC address of the packet in an address table that specifies the passage of the packet when a bit 1 is stored in the first and second bit positions of a storage area of a specified address location of the memory that is accessed by a lower address and an intermediate address and that is accessed by a lower address of the source MAC address of the packet, and when a bit 1 is stored in the third and fourth bit positions of a storage area of an address location of the memory that is accessed by an intermediate address of the source MAC address of the packet.
The method according to claim 7, further comprising a step in which the mobile terminal periodically accesses the receiving mail server and, if it cannot receive a response packet from the receiving mail server, sends a retransmission packet to the receiving mail server.