Multiring control method, node using the method, and control program

A method of controlling a multi-two-media ring network in which a plurality of two-media ring networks using ring nodes capable of transferring an NNI packet by using an inner ring or an outer ring and transferring the NNI packet to a desired network or terminal are connected, said method comprising:

• a TTL value updating step of updating a TTL value in the NNI packet when the NNI packet is transferred from one of the two-media ring networks to another of the two-media ring networks;
• a TTL discard value recomputation step of recomputing a TTL discard value on the basis of in-ring fault information in the transferred NNI packet in a case where a fault occurs in some of the ring nodes in the another of the two-media ring networks;
• and
• an NNI packet processing step of comparing the updated TTL value and the recomputed TTL discard value and discarding the NNI packet or transferring the NNI packet to an adjacent ring node according to the result of comparison.

A ring node connected between a plurality of two-media ring networks using said ring node and other ring nodes capable of transferring an NNI packet by using an inner ring or an outer ring and transferring the NNI packet to a desired network or terminal are connected, said ring node comprising:

• TTL value updating means of updating a TTL value in the NNI packet when the NNI packet is transferred from one of the two-media ring networks to another of the two-media ring networks;
• TTL discard value recomputation means of recomputing a TTL discard value on the basis of in-ring fault information in the transferred NNI packet in a case where a fault occurs in some of the ring nodes in the another of the two-media ring networks;
• and
• NNI packet processing means of comparing the updated TTL value and the recomputed TTL discard value and discarding the NNI packet or transferring the NNI packet to an adjacent ring node according to the result of comparison.

A ring node R1 in a multi-two-media ring network in which a plurality of two-media ring networks constituted by said ring node R1 and other ring nodes R1 capable of transmitting and receiving an NNI packet by using an inner ring or an outer ring and performing transmitting and receiving of the NNI packet with a terminal through a port are connected by ring nodes R2 which bridge the two-media ring networks, a ring protection domain being formed by a plurality of the ring nodes R2 bridging the two-media ring networks, said ring node R1 comprising:

• fault information notice means of notifying fault information to the other ring nodes R1 in the same two-media ring network if a fault occurs at an adjacent one of the ring nodes R2;
• send-back transfer means of sending back the transferred NNI packet in transfer of the NNI packet;
• and
• NNI packet transmitting means of updating the TTL value on the basis of fault information from the other ring nodes R1 if said ring node R1 is a transmission source ring node R1, said NNI packet transmitting means transmitting the NNI packet from the same two-media ring network as before the occurrence of the fault to one of the ring nodes R2 other than the ring node R2 at which the fault has occurred.

A program for making a computer execute a method of controlling a multi-two-media ring network in which a plurality of two-media ring networks using ring nodes capable of transferring an NNI packet by using an inner ring or an outer ring and transferring the NNI packet to a desired network or terminal are connected, said program comprising:

• a TTL value updating step of updating a TTL value in the NNI packet when the NNI packet is transferred from one of the two-media ring networks to another of the two-media ring networks;
• a TTL discard value recomputation step of recomputing a TTL discard value on the basis of in-ring fault information in the transferred NNI packet in a case where a fault occurs in some of the ring nodes in the another of the two-media ring networks;
• and
• an NNI packet processing step of comparing the updated TTL value and the recomputed TTL discard value and discarding the NNI packet or transferring the NNI packet to an adjacent ring node according to the result of comparison.

A method of controlling a multi-two-media ring network in which a plurality of two-media ring networks are connected, each two-media ring network using ring nodes which transfer an NNI packet having a transmission source ring node address, a transmission destination ring node address, a TTL area, and a data storage area, the ring nodes being connected by a two-media ring formed by an inner ring and an outer ring having different NNI packet transfer directions, the ring nodes transferring the NNI packet by using the inner ring or the outer ring and transferring the NNI packet to a desired network or terminal, said method including a ring frame discard method in which,

• in a case where, when an NNI packet to be transmitted over a plurality of packet ring networks is input, one of the ring nodes bridging different two-media rings transfers the NNI packet to the two-media ring at the other bridge end,
• the ring node updates the TTL value in the NNI packet to a TTL initial value A of the transmission destination two-media ring, and transfers the NNI packet from the inner ring or the outer ring;
• one of the ring nodes receiving the NNI packet subtracts 1 from the TTL value in the NNI packet and transfers the NNI packet to the same ring as the inner ring or the outer ring from which the NNI packet has been received, if the transmission destination ring node to which the NNI packet is directed is different from the receiving ring node, if the NNI packet does not need to be transferred to a different one of the two-media rings via the receiving ring node, or if the TTL value in the NNI packet is different from a predetermined TTL value M;
• and
• the receiving ring node removes the NNI packet from the inner ring or the outer ring if the transmission destination ring node to which the NNI packet is directed corresponds to the receiving ring node, if the NNI packet needs to be transferred to a different one of the two-media rings via the receiving ring node, or if the TTL value in the NNI packet is the same as the predetermined TTL value M.

A ring node in a multi-two-media ring network in which a plurality of two-media ring networks are connected, each two-media ring network being constituted by ring nodes which transfer an NNI packet having a transmission source ring node address, a transmission destination ring node address, a TTL area, and a data storage area, or an NNI packet having a packet attribute area and a flow ID area in addition to said NNI packet configuration, the ring nodes being connected by a two-media ring formed by an inner ring and an outer ring having different NNI packet transfer directions, the ring nodes transferring the NNI packet by using the inner ring or the outer ring and transferring the NNI packet to a desired network or terminal, said ring node comprising:

• a TTL comparator which refers to the TTL area of the NNI packet input from the inner ring or the outer ring and discards the NNI packet if the value in the TTL area is equal to a set TTL discard value M;
• a pass/drop determination circuit which subtracts 1 from the TTL value in an NNI packet transferred from said TTL comparator, having a transmission destination ring node address or a flow ID designating said ring node or a group of ring nodes including said ring node, and having as a packet attribute an identifier for in-ring fault information notice, an NNI packet having as a packet attribute an identifier for data and having as a transmission destination ring node address an address indicating a need for inter-ring bridging or an NNI packet having as a flow ID an identifier indicating a need for inter-ring bridging, and an NNI packet having as a packet attribute an identifier for data and having as a transmission destination ring node address an address indicating a need for inhibiting inter-ring bridging or an NNI packet having as a flow ID an identifier indicating a need for inhibiting inter-ring bridging, which outputs each of the NNI packets having values other than 0 as the results of subtraction of the TTL value respectively to a suitable port, and which discards an NNI packet if the result of subtraction of the TTL value is 0;
• a protection switch which allows the NNI packet transferred from said pass/drop determination circuit, having as a packet attribute an identifier for data and having as a transmission destination ring node address an address indicating a need for inhibiting inter-ring bridging or the NNI packet having as a flow ID an identifier indicating a need for inhibiting inter-ring bridging to pass therethrough in a pass mode, and which sends back the NNI packet in a wrap mode;
• a ring bridge which outputs to a suitable port the NNI packet transferred from said pass/drop determination circuit, having as a packet attribute an identifier for data and having as a transmission destination ring node address an address indicating a need for inter-ring bridging or the NNI packet having as a flow ID an identifier indicating a need for inter-ring bridging;
• a TTL setting circuit which updates the TTL value in the NNI packet transferred from said ring switch;
• a ring protection processing/topology management circuit which notifies said TTL setting circuit of a TTL initial value A, which computes the TTL discard value M on the basis of the number n of ring nodes existing in the two-media ring if the in-ring fault information notice in the NNI packet transferred from the pass/drop determination circuit, having a transmission destination ring node address or a flow ID designating said ring node or a group of ring nodes including said ring node, and having as a packet attribute an identifier for in-ring fault information notice does not indicate occurrence of any fault, or on the basis of the number of hops h1 on the inner ring and the number of hops h2 on the outer ring to the fault detecting ring node if the in-ring fault information notice indicates occurrence of a fault, which informs the TTL comparator of the computed TTL discard value M, and which changes the mode of said protection switch to the wrap mode and forms an NNI packet having an in-ring fault information including the address of said node if a fault occurs at a junction link in said ring node;
• and
• a multiplexing circuit which multiplexes the NNI packets from said TTL setting circuit, said protection switch, and said ring protection processing/topology management circuit, and transfers the multiplexed packets to the inner ring or the outer ring.

A method of controlling a multi-two-media ring network in which a plurality of two-media ring networks are connected by a ring node R2 for inter-ring bridging, each two-media ring network being constituted by ring nodes R1 which transfer an NNI packet having a transmission source ring node address, a transmission destination ring node address, a TTL area, and a data storage area, or an NNI packet having a packet attribute area, a flow ID area and a transmission ring ID in addition to said NNI packet configuration, the ring nodes R1 being connected by a two-media ring formed by an inner ring and an outer ring having different NNI packet transfer directions, the ring nodes R1 transmitting and receiving the NNI packet by using the inner ring or the outer ring and performing transmitting and receiving of the NNI packet with a terminal through a tributary port, said method comprising:

• forming an inter-ring protection domain by arranging the ring node R2 and a plurality of other ring nodes R2 in an annular configuration, and measuring or previously setting the number of hops to each of the adjacent ring nodes R2 in the same inter-ring protection domain;
• and
• effecting protection from a fault at any of the inter-ring bridging ring nodes by performing processing including:
• if one of the ring nodes R2 becomes faulty, causing an NNI packet, which is about to be transferred to the faulty ring node R2 via the inner ring, to be transferred to the outer ring by means of the adjacent ring node R1 or R2 on the two-media ring containing the faulty ring node R2, causing an NNI packet, which is about to be transferred to the faulty ring node R2 via the outer ring, to be transferred to the inner ring by means of the ring node R1 or R2, and, when some of the ring nodes R1 and R2 on the same two-media ring as that having the faulty ring node R2 cause NNI packets to flow into the two-media ring, storing a value which is the sum of an initial value A, the number of hops h to the faulty ring node R2 and a fixed value i as TTL in the NNI packet to be transferred from the faulty ring node R2 to another of the two-media rings, storing the initial value A as TTL in the NNI packet not to be transferred from the faulty ring node R2 to any of the other two-media rings, and transferring each of the NNI packets to the same ring as before the occurrence of the fault;
• when one of the ring nodes R2 belonging to the same inter-ring protection domain receives an NNI packet, comparing the transmission ring ID and the TTL value in the NNI packet with the ID of the receiving ring and the TTL extract value X, respectively, taking in the NNI packet if the result of comparison meets a certain extraction condition, setting the TTL initial value A common in the two-media ring at the other bridge end as TTL in the NNI packet if the faulty ring node R2 belongs to the two-media ring at the other bridge end, and transferring the NNI packet;
• and
• setting a value obtained by adding the number of hops BD to the adjacent ring node R2 in the same inter-ring protection domain and a fixed value k to the TTL initial value A common in the two-media ring at the other bridge end as TTL in the NNI packet if the faulty ring node R2 does not belong to the two-media ring at the other bridge end, and transferring the NNI packet.

A ring node R1 in a multi-two-media ring network in which a plurality of two-media ring networks are connected by ring nodes R2 for inter-ring bridging, each two-media ring network being constituted by said ring node R1 and other ring nodes R1 which transfer an NNI packet having a transmission source ring node address, a transmission destination ring node address, a TTL area, and a data storage area, or an NNI packet having a packet attribute area, a flow ID area and a transmission ring ID in addition to said NNI packet configuration, the ring nodes being connected by a two-media ring formed by an inner ring and an outer ring having different NNI packet transfer directions, the ring nodes transmitting and receiving the NNI packet by using the inner ring or the outer ring and performing transmitting and receiving of UNI packets with a terminal through a tributary port, said ring node R1 comprising:

• an address comparator which discards an NNI packet transferred from the inner ring or the outer ring, having a transmission source ring node address coinciding with the address of said ring node, and having a transmission ring ID coinciding with the receiving ring;
• a forwarding circuit which outputs to a suitable port an NNI packet transferred from said address comparator and meeting a condition 1, i.e., having a packet attribute indicating fault information notice, an NNI packet meeting a condition 2, i.e., having a packet attribute indicating data and a transmission destination ring node address coinciding only with the address of said ring node, and an NNI packet meeting a condition 3, i.e., having a packet attribute indicating data and a transmission destination ring node address indicating a plurality of ring node addresses including the address of said ring node, which discards an NNI packet not meeting said condition 1, an NNI packet not meeting said condition 2, and an NNI packet having a TTL value equal to 0 as result of subtraction of 1 from the TTL value of an NNI packet copied from an NNI packet meeting said condition 3, and which outputs NNI packets with TTL values other than 0 to a suitable port.
• a frame conversion circuit which converts an input UNI packet into an NNI packet and outputs the NNI packet to a transmission destination ring node, and which converts an input NNI packet into a UNI packet and outputs the UNI packet;
• a TTL setting circuit which is supplied with an NNI packet transmitted from said frame conversion circuit and updates the TTL values in the NNI packet to designated values according to a designated flow ID and a transmission destination ring node address;
• a packet switch which transfers NNI packets supplied from said forwarding circuit and said TTL setting circuit to said frame conversion circuit or suitable ports as required;
• a protection switch which allows an NNI packet not meeting the conditions 1 and 2 but meeting the condition 3, transferred from said forwarding circuit by being copied, and having a TTL value other than 0 to pass therethrough in a pass mode, and sends it back in a wrap mode;
• a ring node protection circuit which receives an NNI packet meeting the condition 1 from said forwarding circuit, which changes the mode of said protection switch to the wrap mode if a fault occurs at a junction link of said ring node, forms an NNI packet containing fault information indicating that the said ring node is a fault detecting ring node, and transfers the NNI packet to a suitable output port, and which transfers a received NNI packet to a suitable output port and notifies fault detecting ring node information if fault information is contained in the received NNI packet;
• a multiplexing circuit which multiplexes NNI packets transferred from said packet switch, said protection switch and said ring node protection circuit, and transfers the multiplexed packets to the inner ring or the outer ring;
• and
• a TTL management circuit which locates a fault point from fault detecting ring node information notified from said ring node protection circuit, grasps the number of hops h to a faulty ring node which may exist as a ring node effecting inter-ring bridging at the fault point, and notifies said TTL updating circuit that the TTL value in an NNI packet transferred to one of the other two-media rings via the faulty ring node is set to a value obtained by adding the number of hops h to the TTL initial value A, and that the TTL value of an NNI packet not transferred to the two-media ring via the faulty ring node is set to the initial value A.

A ring node R2 in a multi-two-media ring network in which a plurality of two-media ring networks are connected by said ring node R2 and other ring nodes R2 for inter-ring bridging, each two-media ring network being constituted by ring nodes R1 which transfer an NNI packet having a transmission source ring node address, a transmission destination ring node address, a TTL area, and a data storage area, or an NNI packet having a packet attribute area, a flow ID area and a transmission ring ID in addition to said NNI packet configuration, the ring nodes being connected by a two-media ring formed by an inner ring and an outer ring having different NNI packet transfer directions, the ring nodes transmitting and receiving the NNI packet by using the inner ring or the outer ring and performing transmitting and receiving of UNI packets with a terminal through a tributary port, said ring node R2 comprising:

• an NNI packet input via the inner ring or the outer ring, having a packet transmission destination ring node address or a flow ID, or both the packet transmission destination ring node address and the flow ID, and a packet attribute indicating in-ring fault information notice, an NNI packet having a packet attribute indicating data and to be transferred to different two-media rings, and an NNI packet in which the relationship between a transmission ring ID and a receiving ring and the relationship between a TTL value and a TTL extract value X satisfy a certain condition;
• a bridge determination circuit which separates NNI packets which are to be transferred to the same two-media ring and which have a TTL value from which a value other than 0 is obtained by subtraction of 1, which transfers each NNI packet to a suitable output port, and which discards NNI packets among those to be transferred to the same two-media ring if the result of TTL subtraction is 0;
• a protection switch which allows an NNI packet processed by subtraction processing and transferred from said bridge determination circuit to pass therethrough in a pass mode, and which sends it back in a wrap mode;
• a ring node protection circuit which receives an NNI packet transferred from said bridge determination circuit and having a packet attribute indicating in-ring fault information notice, which grasps fault information about the two-media ring to which said ring node belongs, which changes the mode of said protection switch to the wrap mode if a fault occurs in a junction link of said ring node, and which holds fault detecting ring node information in a fault information notice in the case of a fault other than that at the junction link of said ring node, forms an in-ring fault information NNI packet, and transfers this packet to a suitable output port;
• a ring bridge which transfers to a suitable output port an NNI packet transferred from said bridge determination circuit, having as a packet attribute indicating data and to be transferred to different two-media rings, and an NNI packet in which the relationship between the transmission ring ID and the receiving ring and the relationship between the TTL value and the TTL extract value X satisfy a certain condition;
• a TTL updating circuit which updates the TTL value in the NNI packet transferred from said ring bridge in a unit corresponding to a packet flow ID, a transmission destination ring node address, or a combination of a flow ID, a transmission destination ring node address and a transmission source ring node address;
• a multiplexing circuit which multiplexes NNI packets transferred from said protection switch, said ring node protection circuit, and said ring bridge, and transfers the multiplexed packets to the inner ring or the outer ring;
• and
• a TTL management circuit which locates a fault point by referring to fault detecting ring node information notified from said ring node protection circuit, grasps the number of hops h to a faulty ring node which may exist as a ring node effecting inter-ring bridging at the fault point, and identifies an NNI packet transferred to the other two-media ring via the faulty ring node;
• which notifies said TTL updating circuit that the TTL value in the identified NNI packet is set to a TTL value Y, the TTL value in an NNI packet not transferred to the other two-media ring via the faulty ring node is set to the initial value A, and the TTL value in the NNI packet in which the relationship between the transmission ring ID and the receiving ring and the relationship between the TTL value and the TTL extract value X satisfy a certain condition, and which is transferred to said ring bridge is set to a TTL value Z;
• and
• which notifies said bridge determination circuit of the TTL extract value X.

A ring node R2 in a multi-two-media ring network in which a plurality of two-media ring networks are connected by said ring node R2 and other ring nodes R2 for inter-ring bridging, each two-media ring network being constituted by ring nodes R1 which transfer an NNI packet having a transmission source ring node address, a transmission destination ring node address, a TTL area, and a data storage area, or an NNI packet having a packet attribute area, a flow ID area and a transmission ring ID in addition to said NNI packet configuration, the ring nodes being connected by a two-media ring formed by an inner ring and an outer ring having different NNI packet transfer directions, the ring nodes transmitting and receiving the NNI packet by using the inner ring or the outer ring and performing transmitting and receiving of UNI packets with a terminal through a tributary port, said ring node R2 comprising:

• an NNI packet input via the inner ring or the outer ring, having a packet transmission destination ring node address or a flow ID, or both the packet transmission destination ring node address and the flow ID, and a packet attribute indicating in-ring fault information notice, an NNI packet having a packet attribute indicating data and to be transferred to different two-media rings, and an NNI packet in which the relationship between a transmission ring ID and a receiving ring and the relationship between a TTL value and a TTL extract value X satisfy a certain condition;
• a bridge determination circuit which separates NNI packets which are to be transferred to the same two-media ring and which have a TTL value from which a value other than 0 is obtained by subtraction of 1, which transfers each NNI packet to a suitable output port, and which discards NNI packets among those to be transferred to the same two-media ring if the result of TTL subtraction is 0;
• a protection switch which allows an NNI packet processed by subtraction processing and transferred from said bridge determination circuit to pass therethrough in a pass mode, and which sends it back in a wrap mode;
• a ring node protection circuit which receives an NNI packet transferred from said bridge determination circuit and having a packet attribute indicating in-ring fault information notice, which grasps fault information about the two-media ring to which said ring node belongs, which changes the mode of said protection switch to the wrap mode if a fault occurs in a junction link of said ring node, and which holds fault detecting ring node information in a fault information notice in the case of a fault other than that at the junction link of said ring node, forms an in-ring fault information NNI packet, and transfers this packet to a suitable output port;
• a hop counter which receives an NNI packet transferred from said bridge determination circuit, having as a packet attribute indicating data and to be transferred to different two-media rings, and an NNI packet in which the relationship between the transmission ring ID and the receiving ring and the relationship between the TTL value and the TTL extract value X satisfy a certain condition, and which computes the number of hops h1 of the NNI packet in the two-media ring from the difference from the TTL initial value A determined in advance in the two-media ring;
• a ring bridge which transfers an NNI packet from the hop counter to a suitable output port;
• a TTL updating circuit which updates the TTL value in the NNI packet transferred from said ring bridge in a unit corresponding to a packet flow ID, a transmission destination ring node address, or a combination of a flow ID, a transmission destination ring node address and a transmission source ring node address;
• a multiplexing circuit which multiplexes NNI packets transferred from said protection switch, said ring node protection circuit, and said ring bridge, and transfers the multiplexed packets to the inner ring or the outer ring;
• and
• a TTL management circuit which locates a fault point by referring to fault detecting ring node information notified from said ring node protection circuit, grasps the number of hops h to a faulty ring node which may exist as a ring node effecting inter-ring bridging at the fault point, and identifies an NNI packet transferred to the other two-media ring via the faulty ring node from the relationship between the flow ID notified from said hop counter or transmission source ring node address and the number of hops h1 in the two-media ring notified from said hop counter;
• which notifies said TTL updating circuit that the TTL value in the identified NNI packet is set to a TTL value Y, the TTL value in an NNI packet not transferred to the other two-media ring via the faulty ring node is set to the initial value A, the TTL value in the NNI packet is set to Z1 if the NNI packet is transferred to said ring bridge while the relationship between the transmission ring ID and the receiving ring and the relationship between the TTL value and the TTL extract value X satisfy a certain condition, and if the faulty ring node R2 does not exist on the two-media ring at the other bridge end, and the TTL value in the NNI packet is set to Z2 if the faulty ring node R2 exists on the two-media ring at the other bridge end;
• and
• which notifies said bridge determination circuit of the TTL extract value X.

A ring node R2 in a multi-two-media ring network in which a plurality of two-media ring networks are connected by said ring node R2 and other ring nodes R2 for inter-ring bridging, each two-media ring network being constituted by ring nodes R1 which transfer an NNI packet having a transmission source ring node address, a transmission destination ring node address, a TTL area, and a data storage area, or an NNI packet having a packet attribute area, a flow ID area and a transmission ring ID in addition to said NNI packet configuration, the ring nodes being connected by a two-media ring formed by an inner ring and an outer ring having different NNI packet transfer directions, the ring nodes transmitting and receiving the NNI packet by using the inner ring or the outer ring and performing transmitting and receiving of UNI packets with a terminal through a tributary port, said ring node R2 comprising:

• an NNI packet input via the inner ring or the outer ring, having a packet transmission destination ring node address or a flow ID, or both the packet transmission destination ring node address and the flow ID, and a packet attribute indicating in-ring fault information notice, an NNI packet having a packet attribute indicating inter-ring fault information notice, an NNI packet having a packet attribute indicating data and to be transferred to different two-media rings, and an NNI packet in which the relationship between a transmission ring ID and a receiving ring and the relationship between a TTL value and a TTL extract value X satisfy a certain condition;
• a bridge determination circuit which separates NNI packets which are to be transferred to the same two-media ring and which have a TTL value from which a value other than 0 is obtained by subtraction of 1, which transfers each NNI packet to a suitable output port, and which discards NNI packets among those to be transferred to the same two-media ring if the result of TTL subtraction is 0;
• a protection switch which allows an NNI packet processed by subtraction processing and transferred from said bridge determination circuit to pass therethrough in a pass mode, and which sends it back in a wrap mode;
• a ring node protection circuit which receives an NNI packet transferred from said bridge determination circuit and having a packet attribute indicating in-ring fault information notice, which grasps fault information about the two-media ring to which said ring node belongs, which changes the mode of said protection switch to the wrap mode if a fault occurs in a junction link of said ring node, and which holds fault detecting ring node information in a fault information notice in the case of a fault other than that at the junction link of said ring node, forms an in-ring fault information NNI packet, and transfers this packet to a suitable output port;
• a ring bridge which transfers to a suitable output port an NNI packet transferred from said bridge determination circuit, and having as a packet attribute indicating inter-ring fault information notice, and NNI packet having a packet attribute indicating data and to be transferred to different two-media rings, and an NNI packet in which the relationship between the transmission ring ID and the receiving ring and the relationship between the TTL value and the TTL extract value X satisfy a certain condition;
• an inter-ring protection circuit which receives an NNI packet transferred from said ring bridge, and having as a packet attribute indicating inter-ring fault information notice, and which, in the event of detection of fault information or a fault at one of the adjacent ring nodes R2 on the same ring protection domain notified through inter-ring fault information, notifies some of the adjacent ring-nodes R2 on the same ring protection domain;
• a TTL updating circuit which updates the TTL value in the NNI packet transferred from said ring bridge in a unit corresponding to a packet flow ID, a transmission destination ring node address, or a combination of a flow ID, a transmission destination ring node address and a transmission source ring node address;
• a multiplexing circuit which multiplexes NNI packets transferred from said protection switch, said ring node protection circuit, and said ring bridge, and transfers the multiplexed packets to the inner ring or the outer ring;
• and
• a TTL management circuit which locates a fault point by referring to fault detecting node information notified from said ring node protection circuit, grasps the number of hops h to a faulty node which may exist as a ring node effecting inter-ring bridging at the fault point, and identifies an NNI packet transferred to the other two-media ring via the faulty ring node from the relationship between the flow ID notified from said hop counter or transmission source ring node address and the number of hops h1 in the two-media ring notified from said hop counter;
• which notifies said TTL updating circuit that the TTL value in the identified NNI packet is set to a TTL value Y, the TTL value in an NNI packet not transferred to the other two-media ring via the faulty ring node is set to the initial value A, the TTL value in the NNI packet is set to Z1 if the NNI packet is transferred to said ring bridge while the relationship between the transmission ring ID and the receiving ring and the relationship between the TTL value and the TTL extract value X satisfy a certain condition, and if the faulty ring node R2 does not exist on the two-media ring at the other bridge end, and the TTL value in the NNI packet is set to Z2 if the faulty ring node R2 exists on the two-media ring at the other bridge end;
• and
• which notifies said bridge determination circuit of the TTL extract value X.

A ring node R2 in a multi-two-media ring network in which a plurality of two-media ring networks are connected by said ring node R2 and other ring nodes R2 for inter-ring bridging, each two-media ring network being constituted by ring nodes R1 which transfer an NNI packet having a transmission source ring node address, a transmission destination ring node address, a TTL area, and a data storage area, or an NNI packet having a packet attribute area, a flow ID area and a transmission ring ID in addition to said NNI packet configuration, the ring nodes being connected by a two-media ring formed by an inner ring and an outer ring having different NNI packet transfer directions, the ring nodes transmitting and receiving the NNI packet by using the inner ring or the outer ring and performing transmitting and receiving of UNI packets with a terminal through a tributary port, said ring node R2 comprising:

• an NNI packet input via the inner ring or the outer ring, having a packet transmission destination ring node address or a flow ID, or both the packet transmission destination ring node address and the flow ID, and a packet attribute indicating in-ring fault information notice, an NNI packet having a packet attribute indicating inter-ring fault information notice, an NNI packet having a packet attribute indicating data and to be transferred to different two-media rings, and an NNI packet in which the relationship between a transmission ring ID and a receiving ring and the relationship between a TTL value and a TTL extract value X satisfy a certain condition;
• a bridge determination circuit which separates NNI packets which are to be transferred to the same two-media ring and which have a TTL value from which a value other than 0 is obtained by subtraction of 1, which transfers each NNI packet to a suitable output port, and which discards NNI packets among those to be transferred to the same two-media ring if the result of TTL subtraction is 0;
• a protection switch which allows an NNI packet processed by subtraction processing and transferred from said bridge determination circuit to pass therethrough in a pass mode, and which sends it back in a wrap mode;
• a ring node protection circuit which receives an NNI packet transferred from said bridge determination circuit and having a packet attribute indicating in-ring fault information notice, which grasps fault information about the two-media ring to which said ring node belongs, which changes the mode of said protection switch to the wrap mode if a fault occurs in a junction link of said ring node, and which holds fault detecting ring node information in a fault information notice in the case of a fault other than that at the junction link of said ring node, forms an in-ring fault information NNI packet, and transfers this packet to a suitable output port;
• a hop counter which receives an NNI packet transferred from said bridge determination circuit, having as a packet attribute indicating data and to be transferred to different two-media rings, and an NNI packet in which the relationship between the transmission ring ID and the receiving ring and the relationship between the TTL value and the TTL extract value X satisfy a certain condition, and which computes the number of hops h1 of the NNI packet in the two-media ring from the difference from the TTL initial value A determined in advance in the two-media ring;
• a ring bridge which transfers to a suitable output port an NNI packet transferred from said hop counter;
• an inter-ring protection circuit which receives an NNI packet transferred from said ring bridge, and having as a packet attribute indicating inter-ring fault information notice, and which, in the event of detection of fault information or a fault at one of the adjacent ring nodes R2 on the same ring protection domain notified through inter-ring fault information, notifies some of the adjacent ring nodes R2 on the same ring protection domain;
• a TTL updating circuit which updates the TTL value in the NNI packet transferred from said ring bridge in a unit corresponding to a packet flow ID, a transmission destination ring node address, or a combination of a flow ID, a transmission destination ring node address and a transmission source ring node address;
• a multiplexing circuit which multiplexes NNI packets transferred from said protection switch, said ring node protection circuit, and said ring bridge, and transfers the multiplexed packets to the inner ring or the outer ring;
• and
• a TTL management circuit which locates a fault point by referring to fault detecting ring node information notified from said ring node protection circuit, grasps the number of hops h to a faulty ring node which may exist as a ring node effecting inter-ring bridging at the fault point, and identifies an NNI packet transferred to the other two-media ring via the faulty ring node from the relationship between the flow ID notified from said hop counter or transmission source ring node address and the number of hops h1 in the two-media ring notified from said hop counter;
• which notifies said TTL updating circuit that the TTL value in the identified NNI packet is set to a TTL value Y, the TTL value in an NNI packet not transferred to the other two-media ring via the faulty ring node is set to the initial value A, the TTL value in the NNI packet is set to Z1 if the NNI packet is transferred to said ring bridge while the relationship between the transmission ring ID and the receiving ring and the relationship between the TTL value and the TTL extract value X satisfy a certain condition, and if the faulty ring node R2 does not exist on the two-media ring at the other bridge end, and the TTL value in the NNI packet is set to Z2 if the faulty ring node R2 exists on the two-media ring at the other bridge end;
• and
• which notifies said bridge determination circuit of the TTL extract value X.