Method for performing telework service by transferring ethernet frame over ring network using low-order address of mac address

Abstract

To perform transfer via a ring network.SOLUTION: When a packet from a terminal 13 arrives at a device 6, 1 is stored in first and second bits of a storage region at an address position of an SRAM which is accessed by a low-order address of a source MAC address, 1 is stored in third and fourth bits of a storage region at an address position of the SRAM which is accessed by an intermediate address of the source MAC address, and the packet is sent out to a counterclockwise ring 1, and a packet from a server is sent to both rings from the device 6 of which the NICMAC address of a router is stored as the source MAC address of the packet. When the packet arrives at the device 6, in the case where 1 is stored in the first and second bits of a storage region at an address position of the SRAM which is accessed by the low-order address of the destination MAC address and 1 is stored in third and fourth bits of a storage region at an address position of the SRAM which is accessed by an intermediate address of the destination address, the packet is sent outside of the ring and the other is sent out ahead of the ring.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for providing a telework service by transferring an Ethernet frame through a ring network using a lower address of a MAC address.

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

[0003] 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.

[0004] A typical conventional example of a ring network is a ring network using a master switch and a slave switch, as described in Patent Document 3. If one of the ring ports on the switch is a blocked port that does not pass frames, This prevents congestion caused by cluttering. If a fault occurs in the ring network, the monitoring frames sent from the master switch to the master switch will not arrive, and instead The master switch receives a failure notification frame from the slave switch at the failure point. The master switch unblocks the blocked port of the master switch to allow the frame to pass. Also, a blocked port is set on the failed transmission line side of one of the slave switches of the failure point, and the link The ring network continues to operate even after the ring network has recovered from a failure. 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 failure, the FDBs of all ring node devices in the ring are cleared and the FDBs are reconstructed by flooding. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2000-151617 A [Patent Document 2] JP 2004-15592 A [Patent Document 3] Retable No. 2008-068813 [Non-patent literature]

[0006] [Non-Patent Document 1] G.8032 “Ethernet Ring Protection Swithing” Summary of the Invention [Problem to be solved by the invention]

[0007] The conventional address storage method disclosed in Japanese Patent Application Laid-Open No. 2000-151617 stores MAC addresses by nesting, which causes a problem that it takes a long time to trace the stored address destination.

[0008] In addition, in the conventional address storage method disclosed in Japanese Patent Application Laid-Open No. 2004-15592, the lower bits It is described that if there is no vacancy in the entry table position of the MAC address specified by the 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 the two lower bit strings, and since there are multiple stored addresses at the same address position in the same entry table, it is necessary to compare these multiple addresses, which results in a problem of long search times.

[0009] Conventional ring networks, such as 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 using MAC addresses and port numbers, which results in a large number of MAC addresses to be stored.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, a drawback is that when the destination MAC address of a packet to be forwarded is not stored in the MAC address table, the packet is flooded.

[0010] In addition, because an FDB (Forwarding Database) based on a MAC address table is used, when a loopback packet returns to the source ring node device in the event of a ring transmission path failure, the source MAC address of the packet has the port number stored as the port number outside the ring, so in RPR, the port number of the destination MAC address of the packet is set to the ring downstream transmission path port, making it possible to transition to steering; however, in a normal Ethernet ring, the arrival ring port and source MAC address are stored as a pair in the MAC address table, so there is a problem that it is not possible to transition to steering operation. In addition, a blocking point is adopted in the ring as an STP to avoid congestion caused by flooding when recovering from a fault in the ring network. However, because of this blocking point, a method of transitioning from wrapping to steering, such as RPR, cannot be used, and it becomes necessary to re-store the FDB by flooding.

[0011] Furthermore, in a conventional ring network, when searching for a connection destination, the entire destination MAC address is required, and searching using the lower address of the destination MAC address is not possible. 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 storage process is not possible because the lower address of the destination MAC address does not indicate when the packet arrived at the destination. When the destination address is fixed, such as a server, it can be reached using the destination MAC address, but this is not possible for a terminal device with many destinations.

[0012] In addition, in conventional MAC address tables, when a MAC address cannot be stored, it becomes an unknown packet, and the problem is solved by flooding, which has the drawback of being prone to congestion. In addition, conventional RPR steering involves writing the MAC address of the destination node of the wrapped packet into a table on the left wall, which poses the problem that it must be written to all ring nodes not beyond the destination ring node.

[0013] The object of the present invention is to provide a method for providing telework services in a simple manner, without using a conventional MAC address table, by using a ring network in which a lower address memory that stores lower addresses of a MAC address is used in a ring node device. [Means for solving the problem]

[0014] The present invention has been made in consideration of the above problems in the prior art, and the means for solving the problems are described below. A first aspect of the present invention is a network system in which a plurality of packet adding, dropping and passing devices are inserted into an upper ring network of a clockwise ring transmission path 2 and a counterclockwise ring transmission path 1, a lower ring network is connected to the packet adding, dropping and passing devices, and a terminal device is accommodated under the packet adding, dropping and passing devices of the lower ring network, wherein a packet accessing one of a plurality of servers connected from the terminal device to the upper ring network via a router is forwarded to the router as an Ethernet (registered trademark) frame, and on the counterclockwise ring as a packet whose destination MAC address is the NIC MAC address of the ring network interface of the router, and an Ethernet frame traveling from the server to the terminal device via the router is copied in the add, drop and passing device of the ADDed packet and forwarded to both rings.

[0015] A second aspect of the present invention is a system according to the first aspect of the present invention, in which, when a packet from the terminal device arrives at a packet add, drop and pass-through device of the upper ring network, a means for storing a bit 1 in the first and second bit positions of a storage area of ​​an address position of the SRAM accessed by a lower address of the source MAC address of the packet, and storing a bit 1 in the third and fourth bit positions of a storage area of ​​an address position of the SRAM accessed by an intermediate address of the source MAC address of the packet, and sending the packet to a counterclockwise ring, and directing the packet by a server via a router to a ring node device in which a NIC MAC address of the router is stored as a destination MAC address of the packet; When a packet from a server is sent to both rings from a ring node 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 an add, drop, or pass-through device of the packet, means for sending the packet out of the ring when bit 1 is stored in the first and second bit positions of a memory area of ​​an address location in the SRAM accessed by a lower address of the destination MAC address of the packet, and when bit 1 is stored in the third and fourth bit positions of a memory area of ​​an address location in the SRAM accessed by an intermediate address of the destination MAC address of the packet, and means for sending the packet forward in the ring in other cases.

[0016] A third aspect of the present invention provides a system according to the first aspect of the present invention, When a plurality of packets from the terminal device arrive at a packet add, drop and pass-through device of the upper ring network, means for storing a bit 1 in the first and second bit positions when the least significant bit of the source MAC address of the packet in a storage area of ​​an address position of the SRAM accessed by a lower address of the source MAC address of the packet is bit 0, storing a bit 1 in the third and fourth bit positions of the storage area of ​​an address position of the SRAM accessed by an intermediate address of the source MAC address of the packet, storing a bit 1 in the fifth and sixth bit positions when the least significant bit of the source MAC address of the packet in a storage area of ​​an address position of the SRAM accessed by a lower address of the source MAC address of the packet is bit 1, and storing a bit 1 in the seventh and eighth bit positions of the storage area of ​​an address position of the SRAM accessed by an intermediate address of the source MAC address of the packet, and sending the packet to a counterclockwise ring, and directing the packet by the server via a router to a ring node device in which a NIC MAC address of the router is stored as a destination MAC address of the packet; When a packet from a server is copied from a ring node device in which the NIC MAC address of the router is stored as the source MAC address of the packet via a router and sent to both rings, and the packet arrives at an add, drop, or pass-through device of the packet, means for sending the packet out of the ring when, when the least significant bit of the destination MAC address of the packet in the storage area of ​​the address location of the SRAM accessed by the lower address of the destination MAC address of the packet is bit 0, a bit 1 is stored in the first and second bit positions and a bit 1 is stored in the third and fourth bit positions of the storage area of ​​the address location of the SRAM accessed by the intermediate address of the destination MAC address of the packet, or when the least significant bit of the destination MAC address of the packet in the storage area of ​​the address location of the SRAM accessed by the lower address of the destination MAC address of the packet is bit 1, a bit 1 is stored in the fifth and sixth bit positions and a bit 1 is stored in the seventh and eighth bit positions of the storage area of ​​the address location of the SRAM accessed by the intermediate address of the destination MAC address of the packet, and means for sending the packet forward on the ring in other cases.

[0017] A fourth aspect of the present invention is a system according to any one of the first, second, or third aspects of the present invention, comprising: This system is characterized in that packets traveling from the terminal device to the server via the ring network include an in-house VLAN ID in the frame header of the VLAN tag in both directions from the OLT to the router before the in-house server, and the VLAN ID of the packets is checked at the device interface for adding, dropping and passing packets in the ring network to which the router is connected and at the ring network connection interface of the OLT. Effect of the Invention

[0018] As explained above, the present invention has the advantage that an employee's terminal device can access the receiving server at the head office using Ethernet frames without increasing the hardware scale of the ring network. Alternatively, the receiving servers at the head office or branch office can be accessed via an access server. A VLAN can be used to increase the reliability of this communication. Since flooding is not required even when a ring transmission path fails, there is an advantage that congestion does not occur even if the Ethernet domain is large. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram for explaining an example of the operation of a packet forwarding system between a terminal device 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, and a server connected to the ring network via a router, the terminal device having an SRAM for a lower address memory that specifies packet transmission outside the ring according to the first embodiment of the present invention, and the packet forwarding system; [Figure 2A] An example of an operation flow diagram of a packet adding, dropping and passing device according to a first embodiment of the present invention. [Figure 2B] An example of an operation flow diagram of a packet adding, dropping and passing device according to a first embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] A first embodiment of the present invention will be described with reference to Fig. 1. This embodiment is an example of a TCP packet forwarding operation of a terminal device using a ring network in a packet forwarding system in which a lower ring containing a terminal device is connected to a packet adding, dropping and passing device having an SRAM for a lower address memory that specifies packet transmission outside the ring, the device being connected by an optical transmission line, the terminal device forwarding information as a MAC packet to a router connected to the upper ring network, and a server connected to the upper ring network via the router. The server is a company server, and this embodiment is an example of a teleworking operation.

[0021] In Fig. 1, 1 is an optical transmission line for a counterclockwise ring, 2 is an optical transmission line for a clockwise ring, 6-1, 6-2, 6-3, and 6-4 are devices for adding, dropping, and passing packets, 11 is an SRAM for lower address memory that specifies packet transmission outside the ring, 12 is an address table for connecting to routers, 13-1, 13-2, 13-3, and 13-4 are terminal devices, 15-1, 15-2, and 15-3 are lower rings, 20 is a company server, and 22 is a router. Also, (1) to (17) indicate the order of packet transfer, in which the MAC addresses transferred through the ring indicated by the dotted line are abbreviated with letter symbols, and I0, I1, I2, I3, and I4 are global IPv4 addresses that are dynamically set as IP addresses in the terminals, or domestic IPv4 addresses of the service provider. Or they are IPv6 addresses. The OE conversion circuit, EO conversion circuit, input buffer, and output buffer are not shown in the figure.

[0022] The operation of Fig. 1 is explained below. An example is shown in which terminal device 13-2 receiving the telework service sends packet (1) Mr1r2γβα(I0) (M indicates an Ethernet packet, r1r2 indicates the NIC MAC address of the ring network interface of router 22, γβα indicates the upper MAC address γ, the middle MAC address β, and the lower MAC address α, which are the MAC addresses of terminal device 13-2, and I0 indicates the IP address of the company's server, which is the destination) to the lower ring 15-2 via ONU, PON, and OLT. When the Ethernet frame is passed from the OLT to the lower ring, the company's VLAN ID is inserted into the VLAN tag of the frame header. When the packet from the terminal 13-2 and the packet from the terminal 13-4 reach the device 6-2 for adding, dropping and passing packets of the upper ring, if the least significant bit of the source MAC address of the packet is bit 0 in the memory area of ​​the address position of the SRAM (11) for the lower address memory for specifying packet transmission outside the ring, accessed by the lower address α (for example, the 1st bit to the 17th bit) of the source MAC address of the packet, a bit 1 is stored in the 1st bit, and a bit 1 is stored in the 2nd bit as the even parity of the 1st bit, and the source MAC address of the packet is stored in the 2nd 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 memory that specifies packet transmission outside the ring accessed by the intermediate address β of the AC address (for example, the 18th to 34th bits are regarded as the 1st to 17th bits of the memory), and 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 upper ring network interface of the router 22 that connects to the company server 20 via the current optical transmission line 1 of the counterclockwise ring is stored. On the other hand, when the least significant bit of the source MAC address of the packet is bit 1 in a storage area of ​​an address position of the SRAM (11) for a lower address memory that specifies packet transmission outside the ring and is accessed by a lower address α (e.g., the 1st to 17th bits) of the source MAC address of the packet, bit 1 is stored in the 5th bit, bit 1 is stored in the 6th bit as the even parity of the 5th bit, and bit 1 is stored in the 7th bit of a storage area of ​​an address position of the SRAM (11) for a lower address memory that specifies packet transmission outside the ring and is accessed by an intermediate address η of the source MAC address of the packet (e.g., the 18th to 34th bits are regarded as the 1st to 17th bits of the memory), bit 1 is stored in the 8th bit as the even parity of the 7th bit.

[0023] When the packet is transferred to the counterclockwise ring 1 by (2) Mr1r2γβα(I0) as shown in the figure and arrives at the device 6-4 for adding, dropping and passing packets, the destination MAC address r1r2 of the packet is stored in the address table 12 for the router, and the VLAN ID (01) of the VLAN tag of the header of the frame is stored in the address table, so the packet is dropped from the ring as (4) Mr1r2γβα(I0) toward the router 22 outside the ring. When the packet arrives at the 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 put into the option field of the IP header, and the IP packet is transferred by (5) IPI3I0 (IP indicates an IP address, I3 indicates the IP address of the terminal connected to the terminal device 13-2, and I0 indicates the IP address of the destination server 20) as shown in the figure, and reaches the server 20.

[0024] Next, an example is shown in which terminal device 13-1 receiving the telework service sends packet (6) Mr1r2δβα(I0) (M indicates an Ethernet packet, r1r2 indicates the NIC MAC address of the ring network interface of router 22, δβα indicates the upper MAC address δ, the middle MAC address β, and the lower MAC address α, which are the MAC addresses of terminal device 13-1, and I0 indicates the IP address of the destination company server) to the lower ring 15-1 via ONU, PON, and OLT. When the Ethernet frame is passed from the OLT to the lower ring, the company's VLAN ID (01) is inserted into the VLAN tag of the frame header. When the packet reaches the device 6-1 for adding, dropping and passing packets of the upper ring, the VLAN tag connection is ignored, and bit 1 is stored in the first bit of the storage area of ​​the address position of SRAM (11) for the lower address memory that specifies packet transmission outside the ring accessed by the lower address α of the source MAC address 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 position of SRAM (11) for the lower address memory that specifies 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 the packet is sent to address table 12 in which the NICMAC address of the upper ring network interface of router 22 that connects to company server 20 via the current optical transmission line 1 of the counterclockwise ring is stored.

[0025] When the packet is forwarded through counterclockwise ring 1 by (8)Mr1r2δβα(I0) as shown in the figure and arrives at device 6-2 for adding, dropping and passing packets, it passes through device 6-2 and arrives at device 6-4 for adding, dropping and passing packets where the destination MAC address r1r2 of the packet is stored in address table 12 for the router and the VLAN ID (01) of the VLAN tag in the header of the frame is stored in the address table, and the packet is dropped from the ring as (11)Mr1r2δβα(I0) toward 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 in the figure), or the source MAC address (δβα) is placed in the option field of the IP header, and the IP packet is forwarded as shown in the figure by (12) IPI2I0 (IP indicates an IP address, I2 indicates the IP address of the terminal connected to terminal device 13-1, and I0 indicates the IP address of the destination server 20), and reaches server 20.

[0026] Next, when a response packet (13) 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) of the upload packet 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 (14) Mδβαr1r2 (I2) used as the MAC header address of the MAC packet is sent to packet add, drop, and pass-through device 6-4 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 obtained from an ARP table (not shown in the figure), and a MAC packet (14)Mδβαr1r2(I2) using the MAC address in the optional field of the IP header as the destination MAC address and the NIC MAC address r1r2 of the ring network interface of router 22 as the source MAC address is sent to device 6-4 for adding, dropping, and passing packets in the ring network.

[0027] When the MAC packet (14) Mδβαr1r2 (I2) arrives at packet add, drop, and pass-through device 6-4, the source MAC address of the packet is stored in address table 12 for router connection, so the company VLAN ID (01) stored in the address table is inserted into the VLAN tag area of ​​the MAC packet, the packet is copied, and sent to both rings.

[0028] When a packet (15-1)Mδβαr1r2(I2) is transferred through the clockwise ring 2 and arrives at the packet add, drop and pass device 6-2, the VLAN tag connection is ignored, and the packet is sent out of the ring because bit 1 is stored in the first bit of the memory area of ​​the address position of the SRAM (11) for the lower address memory that specifies the packet transmission outside the ring 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 memory that specifies the packet transmission outside the ring 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. Since there is no destination terminal device for the packet, it is discarded.

[0029] On the other hand, when the packet (15-2) Mδβαr1r2 (I2) is transferred through the counterclockwise ring 1 and arrives at the device 6-1 for adding, dropping and passing packets, the VLAN tag connection is ignored, and bit 1 is stored in the first bit of the storage area of ​​the address position of the SRAM (11) for the lower address memory that specifies the packet transmission outside the ring 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 storage area of ​​the address position of the SRAM (11) for the lower address memory that specifies the packet transmission outside the ring 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 passes through the lower ring 15-1 and arrives at the OLT connection point toward the destination terminal device 13-1, the VLAN IDs match, so the packet is directed to the terminal device 13-1.

[0030] Next, Fig. 2A and Fig. 2B show an example of an operation flow diagram of the device for adding, dropping and passing packets in the first embodiment. In Fig. 2A, 100 judges whether a packet has arrived from the left-handed ring or the right-handed ring, and if YES, judges 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 dropping (SRAM for the lower address memory for specifying packet sending outside the ring) accessed by the lower address of the destination MAC address of the received packet in 101, 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 dropping accessed by the intermediate address of the destination MAC address of the received packet, and if YES, sends the received packet in 102 out of the ring and returns to (a). If NO, sends the received packet to the front of the ring and returns to (a). If NO at 100, transition to (b). In Fig. 2B, 104 judges whether a packet has arrived from the ADD line, and if the answer is Yes / No, it stores a bit 1 in the first and second bits of the data storage area of ​​the address position of the memory for packet dropping (SRAM for lower address memory specifying packet sending outside the ring) accessed by the lower address of the source MAC address of the received packet in 105, stores a bit 1 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 source MAC address of the received packet, sends the received packet in 106 to the front of the ring in a counterclockwise direction, and returns to (a). If the answer is NO in 104, it returns to (a).

[0031] The first embodiment is based on the premise that there are only two ring node devices on a ring in which bit 1 is stored in the first and second bits of the memory area of ​​an address position in SRAM that is accessed by the lower address of the destination MAC address of a packet, and bit 1 is stored in the third and fourth bits of the memory area of ​​an address position in SRAM that is accessed by the intermediate address of the destination MAC address of the packet. Incidentally, if the number of packet terminals to be ADDed to the ring is 10,000 and the number of addressing bits in the SRAM is 17, then 10,000 / EXP(17ln2) / EXP(17ln2)*10,000 / EXP(17ln2) / EXP(17ln2)*10,000 / EXP(17ln2) / EXP(17ln2)=5.8*EXP(-7ln10)*5.8*EXP(-7ln10)*5.8*EXP(-7ln10) =1.9*EXP(-19ln10), and since the occurrence of three matches is very small, Example 1 is valid. If the source MAC addresses of multiple packets added by the ring node device are divided into the least significant bits, bits 0 and 1, and stored in SRAM, the probability of a match will be even smaller. If the MAC addresses are divided into two parts, bits 1 to 17 and bits 18 to 34, and stored, rather than storing the lowest 24 bits, the probability of a false match may be smaller if the 24 bits are the same than if a lower address memory that stores the same lowest 24 bits is used by the NIC manufacturer.

[0032] In the case of a ring fault in the first embodiment, it can be handled without flooding by steering or both-ring loopback. In the case of both-ring loopback, when a ring network fault occurs, the add, drop and pass devices of the packet on both sides of the fault 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. [Explanation of symbols]

[0033] 1. Counterclockwise ring optical transmission line 2. Clockwise ring optical transmission line 5 Vertex device 6-1, 6-2, 6-3 Packet Add, Drop and Pass Devices 11 SRAM for lower address memory that specifies packet transmission outside the ring 12 Address table for router connections 13-1, 13-2, 13-3, 13-4 Terminal equipment 15-1, 15-2, 15-3 Lower Ring 20 Servers 22 Router

Claims

1. A network system in which a plurality of packet add, drop and pass devices are inserted into an upper ring network of a clockwise ring transmission path 2 and a counterclockwise ring transmission path 1, a lower ring network is connected to the packet add, drop and pass devices, and a terminal device is accommodated under the packet add, drop and pass devices of the lower ring network, wherein a packet accessing one of a plurality of servers connected from the terminal device to the upper ring network via a router is forwarded to the router as an Ethernet (registered trademark) frame, and on the counterclockwise ring as a packet whose destination MAC address is the NIC MAC address of the ring network interface of the router, and the system is provided with a means for copying an Ethernet frame traveling from the server to the terminal device via the router in the add, drop and pass device of the ADDed packet and forwarding it to both rings.

2. When a packet from the terminal device arrives at a packet add, drop and pass-through device of the upper ring network, a means for storing a bit 1 in the first and second bit positions of a storage area of ​​an address position of the SRAM accessed by a lower address of the source MAC address of the packet, and storing a bit 1 in the third and fourth bit positions of a storage area of ​​an address position of the SRAM accessed by an intermediate address of the source MAC address of the packet, to send the packet to a counterclockwise ring, and a means for a server to direct the packet via a router to a ring node device in which a NIC MAC address of the router is stored as a destination MAC address of the packet; When a packet from a server is sent to both rings from a ring node 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 an add, drop, or pass-through device of the packet, the system according to claim 1 further comprising: means for transmitting the packet outside the ring when bit 1 is stored in the first and second bit positions of a memory area of ​​an address location of the SRAM accessed by a lower address of the destination MAC address of the packet, and when bit 1 is stored in the third and fourth bit positions of a memory area of ​​an address location of the SRAM accessed by an intermediate address of the destination MAC address of the packet, and means for transmitting the packet to the front of the ring in other cases.

3. When a plurality of packets from the terminal device arrive at a packet add, drop and pass-through device of the upper ring network, means for storing bit 1 in the first and second bit positions when the least significant bit of the source MAC address of the packet in a storage area of ​​an address position of the SRAM accessed by a lower address of the source MAC address of the packet is bit 0, storing bit 1 in the third and fourth bit positions of the storage area of ​​an address position of the SRAM accessed by an intermediate address of the source MAC address of the packet, storing bit 1 in the fifth and sixth bit positions when the least significant bit of the source MAC address of the packet in a storage area of ​​an address position of the SRAM accessed by a lower address of the source MAC address of the packet is bit 1, and storing bit 1 in the seventh and eighth bit positions of the storage area of ​​an address position of the SRAM accessed by an intermediate address of the source MAC address of the packet, and sending the packet to a counterclockwise ring, and directing the packet by the server via a router to a ring node device in which a NIC MAC address of the router is stored as a destination MAC address of the packet; When a packet from a server is copied from a ring node device in which the NIC MAC address of the router is stored as the source MAC address of the packet via a router and sent to both rings, and the packet arrives at an add, drop, or pass-through device of the packet, 2. The system according to claim 1, further comprising: means for transmitting the packet out of the ring when, when the least significant bit of the destination MAC address of the packet in a storage area of ​​an address location of the SRAM accessed by a lower address of the destination MAC address of the packet is bit 0, a bit 1 is stored in the first and second bit positions and a bit 1 is stored in the third and fourth bit positions of the storage area of ​​the address location of the SRAM accessed by an intermediate address of the destination MAC address of the packet, or when the least significant bit of the destination MAC address of the packet in a storage area of ​​an address location of the SRAM accessed by a lower address of the destination MAC address of the packet is bit 1, a bit 1 is stored in the fifth and sixth bit positions and a bit 1 is stored in the seventh and eighth bit positions of the storage area of ​​the address location of the SRAM accessed by an intermediate address of the destination MAC address of the packet, and for transmitting the packet to the front of the ring in other cases.

4. A system as described in any one of claims 1 to 3, characterized in that packets traveling from the terminal device to the server via the ring network include an internal VLAN ID in the frame header of the VLAN tag in both directions from the OLT to the router before the internal server, and the VLAN ID of the packet is checked at the device interface for adding, dropping and passing packets of the ring network to which the router is connected and at the ring network connection interface of the OLT.

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