Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
  • H04L12/42—Loop networks
  • H04L12/437—Ring fault isolation or reconfiguration
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
  • H04L12/46—Interconnection of networks
  • H04L12/4637—Interconnected ring systems

Definitions

• Metropolitan area networks and enterprise networks are generally constructed as ring networks due to their
• RPR Resilient Packet Ring
• Ethernet ring A ring network based on RPR requires special hardware, and is therefore expensive to implement.
• the technology of Ethernet ring is
• RSTP Rapid Spanning Tree Protocol
• PVST Per-VLAN Spanning Tree protocol
• Multimedia Subsystem Multimedia Subsystem
• RSTP Spanning Tree Protocol
• RRPP Rapid Ring Protection Protocol
• Figure 2 is the configuration of another example of a multi-ring intersecting Ethernet ring network
• Figure 3 is a flow chart depicting an example of a method for handling a fault in a link in a multi-ring intersecting Ethernet ring network
• Figure 4 is a flow chart depicting an example of a setup processing method
• Figure 5 is the configuration of yet another example of a multi-ring intersecting Ethernet ring network
• Figure 7 is a flow chart depicting an example of a ring-extension processing method
• Figure 8 is the configuration of Figure 5 depicting a shared-link-down state
• Figure 9 is the configuration of Figure 5 depicting ring 1 extending to ring 2
• Figure 10 is the configuration of Figure 5 depicting ring 1 and ring 2 extending to ring 3;
• Figure 11 is the configuration of Figure 5 depicting the recovery of ring 3;
• Figure 12 is a flow chart depicting an example of a ring-recovery processing method
• Figure 13 is the configuration of a further example of a multi-ring intersecting Ethernet ring network
• Figure 14 is the configuration of another further example of a multi-ring intersecting Ethernet ring network.
• Figure 15 is a schematic diagram of an example of a communication device.
• the Ethernet ring network of the example comprises two Ethernet rings, ring 1 and ring 2, each ring comprising a plurality of nodes.
• a master node is a node which is the primary control node for the ring, e.g. it may initiate HELLO packets to check the health of the ring and/or perform control to prevent data loops.
• Each ring is provided with one master node.
• Nodes other than a master node that are on the same ring as the master node are all transit nodes.
• nodes A and E are respective master nodes for ring 1 and ring 2
• nodes C, D and F are transit nodes.
• Nodes C and D are shared nodes.
• a shared node is a node that is shared between two or more rings (in this example shared between ring 1 and ring 2) .
• a shared link connects nodes C and D and is shared between ring 1 and ring 2.
• a master node may be a shared node. Examples of such a configuration will be illustrated and described later on.
• Each ring may be identified by a ring ID, or ring sequence number.
• the ring ID for ring 1 will be “1”
• the ring ID for ring 2 will be “2”
• the ring ID for ring n will be “n” and so on.
• Ethernet ring forms a respective Virtual Local Area Network (VLAN) , which can be identified by a VLAN ID (or network ID) .
• the VLAN of each ring may include a separate control VLAN for communicating control signals and a data VLAN for communicating data signals.
• each ring forms a respective control VLAN and data VLAN, the control VLAN of each ring being identified by a control VLAN ID, and the data VLAN of each ring being identified by a data VLAN ID.
• Each node has a plurality of ports for sending or receiving data/control packets.
• one port may be specified as a primary port, and one port may be specified as a secondary port.
• the primary port is configured to transmit a loop detection packet such as a HELLO message
• the secondary port is configured to receive the HELLO message, after it has been forwarded around the ring by the transit nodes of the same ring.
• the secondary port of the master node allows only packets from the control VLAN of the ring to pass, but logically blocks packets from the data VLAN of the ring.
• the master node releases the secondary port and begins to forward packets from the data VLAN.
• all ports of the transit nodes are configured to be
• a port of a shared node which forms a link with a neighbouring ring with a higher ring ID is designated as an extension port, which sends packets to or receives packets from a
• Figure 2 shows an example of another configuration of a multi-ring Ethernet ring network.
• the number of intersecting Ethernet rings is not limited to two, and each ring may have any number of nodes.
• nodes A, E, V and Y are the master nodes for rings 1, 2, m and n respectively.
• Transit nodes C and D are the designated shared nodes shared between rings 1 and 2, and the connection between nodes C and D forms a shared link at which rings 1 and 2 intersect.
• Master node E and transit node F are the designated shared nodes for ring 2 and a neighbouring ring 3 (not shown)
• transit nodes W and X are the designated shared nodes for ring m and the neighbouring ring n.
• the method may be considered, for example as shown in Figure 3, as comprising three processing methods: a setup processing 3-1, a ring-extension processing 3-2, and a ring-recovery processing 3-3.
• each of the plurality of ports of each node belonging to ring n joins the control VLAN and data VLAN of ring n, and also joins the control VLAN and data VLAN of every ring of the
• the same processing is performed for all remaining Ethernet rings of the communication network, for instance, the ports of each node that belongs to ring m join the control VLAN and data VLAN of ring m and of rings m-1, 2, 1.
• the ports of nodes belonging to ring 1 only join the control VLAN and the data VLAN of ring 1.
• the joining of a port in a VLAN may be implemented by creating a correspondence
• each ring comprises a master node (e.g. node Y) and one or more transit nodes (e.g. node Z) .
• Each master node is configured to transmit, at regular intervals, a HELLO message from its primary port in the control VLAN of the ring to which the master node belongs, and listen for the HELLO message at its secondary port.
• the one or more transit nodes of the ring are configured to forward the HELLO message around the ring. When the HELLO message is received at the secondary port this indicates that the ring is in a normal healthy state (the UP state) .
• the master node is configured to block the secondary port from receiving data packets while the ring is in the normal healthy state. Where two neighbouring rings (e.g. ring m and ring n) intersect, the intersecting link is a shared link.
• the nodes on the shared link are specified as shared nodes.
• nodes E and F are specified as shared nodes, and the link between the shared nodes E and F is specified as the shared link between rings 2 and 3 (not shown) .
• nodes W and X are specified as shared nodes, and the link between the shared nodes W and X is specified as the shared link between rings m and n.
• either a master node or a transit node may be configured to function as a shared node.
• the port of each shared node that connects the respective shared link is specified as a shared port.
• Each of the two shared nodes transmits SHARED LINK HELLO messages at regular intervals down the shared link from its respective shared port so as to perform a connectivity test on the shared link.
• Figure 5 depicts a SHARED LINK HELLO message being transmitted from and returned to shared node C and shared node D.
• a ⁇ SHARED LINK HELLO message' is a HELLO message initiated by a shared node and sent down a shared link. If the shared port of a shared node does not receive a returned SHARED LINK HELLO message within a predetermined time, for instance three times the interval for transmitting a SHARED LINK HELLO message
• the shared port determines that the shared link has lost connectivity and is DOWN.
• RRPP_VER is the version number of the RRPP used in the Ethernet ring network.
• the version number may be 2 to distinguish the version used in the examples herein from a previous version.
• RRPPTYPE may, for example, be 0x11, to identify the message as a SHARED LINK HELLO message.
• RRPP Length defines the total length of the RRPP message.
• Ring ID identifies the ring ID of the Ethernet ring with the highest ring ID amongst the Ethernet rings that share the shared link. Ring-extension processing
• the master node of an Ethernet ring When the master node of an Ethernet ring does not receive a HELLO message within a predetermined time, or a shared node at a shared link does not receive a SHARED LINK HELLO message within a predetermined time, it is determined that the respective link is DOWN, and the status of the ring is determined as FAILED.
• the connectivity status In the first case where a common link (i.e. a link other than a shared link) is experiencing connectivity issues, the connectivity status is determined as common-link-down, while in the second case where a fault is detected at a shared link, the connectivity status is determined as shared-link-down.
• the two link-down states are handled differently.
• Figure 6 illustrates the scenario in which a common-link- down is detected by transit nodes B and C.
• transit nodes B and C transmit LINK DOWN messages in the control VLAN of ring 1.
• Master node A of ring 1 receives a LINK DOWN message, and releases (unblocks) its secondary port.
• Master node A then sends COMMON-FLUSH FDB messages in the control VLAN of ring 1 from its secondary port.
• each of the transit nodes B, C and D renews its own MAC/ARP/ND table entries according to the received COMMON-FLUSH FDB message.
• transit nodes C and F detect that the common link CF between nodes C and F is DOWN, the same process may be performed with respect to ring 2, in which master node E releases its secondary port.
• a fault is detected by shared nodes C and D. It is not necessary for both shared nodes C and D to detect the fault simultaneously, and it is possible that only shared node C or only shared node D detects the fault at the shared link.
• shared nodes C and D begin to send SHARED
• a SHARED LINK DOWN message contains the ring ID of each ring that will form an extended ring (the ring ID of each ring sharing the shared link CD) , and the control VLAN ID and data VLAN ID of each ring forming the extended ring.
• the RRPPTYPE entry of the SHARED LINK DOWN message may be set to 0x12, to identify the message as a SHARED LINK DOWN message.
• Shared nodes C and D determine the status of ring 2, that is, the ring that has the highest ring ID amongst the rings sharing the shared link CD, as FAILED.
• the shared node is a master node, for example the shared node E in Figure 9 which is a master node, the shared node reconfigures its extension port as the primary port, and begins transmitting HELLO messages from the extension port.
• transit node F of ring 2 upon receiving a SHARED LINK DOWN message, records the number of the port at which the SHARED LINK DOWN message is received (receiving port number) , and forwards the SHARED LINK DOWN message to master node E. At this point, transit node F determines the status of ring 2 as FAILED.
• master node E Upon receiving the SHARED LINK DOWN message, master node E releases (unblocks) its secondary port, and sends a COMMON- FLUSH FDB message in the control VLAN of ring 2 to instruct each of the nodes in ring 2 to renew its MAC/ARP/ND table entries. At this point, master node E determines the status of ring 2 as FAILED.
• master node E joins ring 1, since ring 1 is a ring that shares the shared link CD and has a ring ID lower than the ring ID of ring 2. Using the ring ID of ring 1 that is contained in the SHARED LINK DOWN message, master node E creates an extended ring that comprises ring 1 and ring 2. Master node E records the correspondence
• the primary port and the secondary port of master node E join the extended ring by creating and recording the
• master node E intermittently sends a RING EXTEND message at regular intervals from its primary port and its secondary port in the control VLAN of ring 2, which contains the ring ID of each ring that shares the shared link CD and has a ring ID lower than the ring ID of ring 2, in this example, ring 1.
• RRPP TYPE may be set as 0x14 to identify the message as a RING EXTEND message.
• additional entries Ring List Length and a ring list are included.
• the ring list contains the ring ID of each ring forming the extended ring.
• the value in the ring list indicates the ID information of one or more rings to be included in the extended ring.
• the transit node(s) of ring 2 upon receiving the RING EXTEND message, forms the extended ring that includes each of the rings indicated in the RING
• the transit node of ring 2, node F is configured such that the port at which the RING EXTEND message is received, and the port at which the SHARED LINK DOWN message is received, join the extended ring. This may be performed by creating and recording correspondence information between the receiving port number of the RING EXTEND message and the receiving port number of the SHARED LINK DOWN message of transit node F, and the ring ID of each of the rings forming the extended ring, for instance ring 1.
• Transit node F of ring 2 continues to forward RING EXTEND messages in the control VLAN of ring 2.
• shared nodes C and D receive a RING EXTEND message from master node E
• shared nodes C and D stop transmitting SHARED LINK DOWN messages.
• the shared node is configured such that the receiving port of the RING EXTEND message joins the extended ring specified in the RING EXTEND message. This may be
• FIG. 9 shows the configuration of the Ethernet ring network after the method of Figure 7 as described above has been applied in response to a shared-link-down state detected at the shared link CD.
• the nodes of ring 2 now function as transit nodes of ring 1, in the same way as transit node B. However, from the perspective of master node A of ring 1 there are no changes to ring 1.
• the method of Figure 7 may be applied again to extend ring 2 (now part of ring 1) into ring 3.
• the shared link EF now functions as a shared link of ring 1, ring 2 and ring 3.
• the shared nodes E and F send SHARED LINK DOWN messages to the master node of the ring with the highest ring ID at the shared link EF, in this case ring 3.
• Each SHARED LINK DOWN message contains the ring IDs of ring 1 and ring 2, as well as the
• Blocks 7-3 to 7-5 of the process of Figure 7 are similarly performed so that ring 1 continues to extend into ring 3, as shown in Figure 10.
• the status of ring 1 is UP, while the status of each of ring 2 and ring 3 is now
• Ethernet ring network of Figure 6 may be performed on the extended ring network. Ring-recovery processing
• FIG. 12 is a flow chart of an example of the ring- recovery processing method for handling the recovery of a shared link of an intersecting Ethernet ring network that is in a shared-link-down state. In the present example, it is assumed that the ring IDs of rings 1 to n are
• a shared node at a shared link that has been in a DOWN state receives a SHARED LINK HELLO message sent by itself, and determines that the shared link is restored.
• shared node E or shared node F receives a SHARED LINK HELLO message, it determines that the shared link EF is restored, and that the status of ring 3 changes from FAILED to UP.
• Shared node E and shared node F each pre-blocks its respective extension port, and withdraws the respective extension port from each ring sharing the shared link EF, which has a ring ID that is not the highest ring ID at the shared link EF.
• shared node E and shared node F withdraw their respective extension port from ring 1 and ring 2. Then, each of shared node E and shared node F renews its own AC/ARP/ND table entries.
• each shared node transmits SHARED LINK UP messages to the master node of the ring with the highest ring ID at this shared link.
• shared node E and shared node F each transmits SHARED LINK UP messages to master node G of ring 3.
• a SHARED LINK UP message contains the ring ID of each shared node.
• a SHARED LINK UP message contains the ring ID of ring 1 and ring 2.
• the format of a SHARED LINK UP message is essentially the same as a SHARED LINK HELLO message.
• the RRPP TYPE value may be set to 0x13, identifying the message as a SHARED LINK UP message.
• the field Ring ID is set to the ring ID of the Ethernet ring with the highest ring ID amongst the Ethernet rings that share the shared link.
• shared node in this step is a master node, for instance master node E in this example, shared node E moreover reconfigures its extension port and its shared port so that the shared port becomes the primary port of master node E again, and master node E resumes intermittent transmission of HELLO messages from the reconfigured shared port that is the primary port.
• master node E moreover reconfigures its extension port and its shared port so that the shared port becomes the primary port of master node E again, and master node E resumes intermittent transmission of HELLO messages from the reconfigured shared port that is the primary port.
• While the shared link is DOWN, if the master node of an Ethernet ring that is sharing the shared link receives, at its secondary port, a HELLO message sent by itself in the control VLAN of the Ethernet ring, or if the master node receives a SHARED LINK UP message sent by a shared node at the shared link, the master node determines that the shared link is restored.
• master node G receives a HELLO message sent by itself or a SHARED LINK UP message sent by shared node E or shared node F, master node G determines that the shared link EF is restored, and that the status of ring 3 changes from FAILED to UP.
• Master node G then, at block 12-3, deletes all information regarding its correspondence with the extended rings, which are Ethernet rings that share the shared link with ring ID lower than the highest ring ID at the shared link - ring 1 and ring 2 in this case, according to the ring ID of the extended rings. In doing so, master node G removes itself from the extended ring 1 and ring 2. Moreover, master node G blocks its secondary port again from receiving signals from the data VLAN.
• the information to be deleted here includes the ring ID of each extended ring, ring 1 and ring 2, the mapping
• master node G transmits DELETE RING messages and COMPLETE-FLUSH FDB messages in the control VLAN of ring 3.
• a DELETE RING message contains the ring ID of each extended ring.
• the format of a DELETE RING message is essentially the same as a RING EXTEND message.
• the RRPP TYPE value may be set to 0x15, identifying the message as a DELETE RING message .
• the transit node(s) of the Ethernet ring that is sharing the DOWN shared link receives, at block 12-5, a COMPLETE-FLUSH FDB message or a DELETE RING message from the master node, for instance, when transit node H receives a COMPLETE-FLUSH FDB message or a DELETE RING message from master node G, the transit node determines that the status of the Ethernet ring changes from FAILED to UP. Upon receiving a COMPLETE-FLUSH FDB message, transit node H renews its MAC/ARP/ND table entries in accordance with the received COMPLETE-FLUSH FDB message.
• transit node H Upon receiving a DELETE RING message, transit node H deletes all information regarding its correspondence with the extended rings according to the ring ID of each extended ring included in the received DELETE RING message.
• the information to be deleted includes the ring ID of each extended ring included in the DELETE RING message, ring 1 and ring 2, the mapping relationship (correspondence information) between the ring ID of each extended ring and the respective control VLAN ID and data VLAN ID, and the mapping relationship
• master node E Upon receiving a SHARED LINK UP message, master node E deletes all information regarding its correspondence with ring 1, and transmits COMPLETE-FLUSH FDB messages and
• the DELETE RING messages in the control VLAN of ring 2.
• the DELETE RING messages contain the ring ID of ring 1.
• transit node F Upon receiving a COMPLETE-FLUSH FDB message, transit node F renews its own MAC/ARP/ND table entries in accordance with the received COMPLETE-FLUSH FDB message. Upon receiving a DELETE RING message, transit node F deletes all information regarding its correspondence with ring 1. Upon receiving a COMPLETE-FLUSH FDB message, shared nodes C and D release their respective extension ports.
• Ethernet ring network configurations of Ethernet ring network.
• one or more of the processing methods may be applied to an Ethernet ring network having a configuration in which a shared link connects more than two shared nodes, such as the configuration illustrated in Figure 13, or to an
• Ethernet ring network having a configuration in which the shared nodes of a shared link are shared by more than two Ethernet rings, such as the configuration illustrated in Figure 14.
• Figure 15 is an example of a network device (such as a switch or router etc) , which may be employed as a node in an Ethernet ring network as described above and in
• the network device 15-1 When configured to function as a master node, the network device 15-1 has a primary port and a secondary port, the secondary port being blocked from receiving data.
• the network device 15-1 comprises a ring-extension module 15-10, a ring- recovery module 15-20 and an interface 15-30.
• a storage module 15-40 may be further provided if desired, for example, for storing correspondence information.
• the ring-extension module 15-10 determines that there is a fault in the shared link, for example by receiving a SHARED LINK DOWN message from a shared node at the shared link, and unblocks its secondary port to allow data to be received from the data VLAN of the Ethernet ring.
• the ring-extension module 15-10 then causes the network device 15-1 to join the neighbouring Ethernet ring, and sends RING EXTEND messages via the interface 15- 30 in control VLAN of the Ethernet ring to notify other communication devices of the Ethernet ring to join the neighbouring Ethernet ring.
• the ring-recovery module 15-20 determines that the shared link is restored, for example by receiving a SHARED LINK UP message from a shared node at the shared link, and blocks the secondary port again from receiving data from the data VLAN.
• the ring-recovery module 15-20 then causes the network device 15-1 to leave the neighbouring Ethernet ring, and sends DELETE RING messages in the control VLAN of the Ethernet ring via the interface 15-30 to notify other communication devices of the Ethernet ring to leave the neighbouring Ethernet ring.
• the network device of Figure 15 may be configured to function as a transit node for use in an Ethernet ring network.
• the ring-extension module 15-10 receives a RING EXTEND message from the control VLAN of the Ethernet ring, and in response causes the network device 15-1 to join the neighbouring Ethernet ring in accordance with the received RING EXTEND message.
• the ring-recovery module 15-20 receives a DELETE RING message from the control VLAN of the Ethernet ring, and in response causes the communication device to leave the neighbouring Ethernet ring in accordance with the received DELETE RING message.
• the ring-extension module 15-10 and the ring-recovery module 15-20 described above may for instance be
• the network device of Figure 15 may be provided at a shared link as a shared node.
• a port of the network device 15-1 is configured as an extension port that connects to the Ethernet ring.
• the ring-extension module 15-10 sends SHARED LINK DOWN messages in the control VLAN of the Ethernet ring in response to detecting a fault in the shared link.
• the ring-recovery module 15-20, or the processing module 16-10 sends SHARED LINK UP messages in the control VLAN of the Ethernet ring in response to detecting that the shared link is restored, and blocks the extension port from sending or receiving data from the data VLAN of the Ethernet ring until the communication device 15-1 or 16-1 receives a COMPLETE-FLUSH FDB message from the master node of the Ethernet ring via the interface 15-30 or 16-20, whereupon said extension port is unblocked.
• the present disclosure thus provides a fault handling method for implementation in a communication network, such as an RRPP multiple-ring Ethernet ring network, and a network device, such as a master node, a transit node or a shared node, for deploying in such a communication network, that may provide a protection mechanism that is data-loop free for such a multiple-ring communication network.
• a communication network such as an RRPP multiple-ring Ethernet ring network
• a network device such as a master node, a transit node or a shared node, for deploying in such a communication network, that may provide a protection mechanism that is data-loop free for such a multiple-ring communication network.
• the present disclosure may provide an improved mechanism for monitoring the connectivity for such a multiple-ring communication network. Furthermore, the present disclosure may provide a framework for

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