G.8032 with optical bypass

Abstract

Systems and methods implemented by a network element in a G.8032 ring include steps of operating an Operations, Administration, and Maintenance (OAM) session with an adjacent network element; and detecting an optical bypass in the G.8032 ring based on the OAM session. The steps can include flushing a forwarding database of the network element based on the optical bypass. The steps can include detecting prior to the optical bypass, that a neighboring node includes a ring block; and subsequent to the optical bypass, installing a new channel block. The optical bypass enables faster protection switching and the present disclosure incorporates an optical bypass in G.8032.

Claims

1. A network element configured to operate in a G.8032 ring, the network element comprising: a plurality of ports interconnected by circuitry configured to operate an Operations, Administration, and Maintenance (OAM) session with an adjacent network element, and detect an optical bypass in the G.8032 ring based on the OAM session.

2. The network element of claim 1, wherein the circuitry is further configured to flush a forwarding database of the network element based on the optical bypass.

3. The network element of claim 1, wherein the circuitry is further configured to detect, prior to the optical bypass, that a neighboring node includes a ring block, and subsequent to the optical bypass, install a new channel block on the G.8032 ring.

4. The network element of claim 3, wherein the circuitry is further configured to remove the new channel block if another channel block is detected on the G.8032 ring.

5. The network element of claim 3, wherein the ring block is detected via a Type-Length-Value (TLV) field in a packet associated with the OAM session.

6. The network element of claim 1, wherein the OAM session includes Continuity Check Messages (CCMs).

7. The network element of claim 1, wherein the optical bypass is detected based on an auto remote Maintenance End Point (MEP) discovery and a timeout of an old remote MEP.

8. The network element of claim 1, further comprising an optical switching device that is configured to connect ring ports of the plurality of ports to the G.8032 ring under normal conditions and to connect the ring ports together responsive to a node fault, thereby providing the optical bypass.

9. A non-transitory computer-readable medium comprising instructions that, when executed, cause a network element in a G.8032 ring to perform steps of: operating an Operations, Administration, and Maintenance (OAM) session with an adjacent network element; and detecting an optical bypass in the G.8032 ring based on the OAM session.

10. The non-transitory computer-readable medium of claim 9, wherein the steps further include flushing a forwarding database of the network element based on the optical bypass.

11. The non-transitory computer-readable medium of claim 9, wherein the steps further include detecting prior to the optical bypass, that a neighboring node includes a ring block; and subsequent to the optical bypass, installing a new channel block on the G.8032 ring.

12. The non-transitory computer-readable medium of claim 11, wherein the steps further include removing the new channel block if another channel block is detected on the G.8032 ring.

13. The non-transitory computer-readable medium of claim 11, wherein the ring block is detected via a Type-Length-Value (TLV) field in a packet associated with the OAM session.

14. The non-transitory computer-readable medium of claim 9, wherein the OAM session includes Continuity Check Messages (CCMs).

15. The non-transitory computer-readable medium of claim 9, wherein the optical bypass is detected based on an auto remote Maintenance End Point (MEP) discovery and a timeout of an old remote MEP.

16. The non-transitory computer-readable medium of claim 9, wherein an optical switching device is configured to connect ring ports of the network element to the G.8032 ring under normal conditions and to connect the ring ports together responsive to a node fault, thereby providing the optical bypass.

17. A method implemented by a network element in a G.8032 ring, the method comprising steps of: operating an Operations, Administration, and Maintenance (OAM) session with an adjacent network element; and detecting an optical bypass in the G.8032 ring based on the OAM session.

18. The method of claim 17, wherein the steps further include flushing a forwarding database of the network element based on the optical bypass.

19. The method of claim 17, wherein the steps further include detecting prior to the optical bypass, that a neighboring node includes a ring block; and subsequent to the optical bypass, installing a new channel block on the G.8032 ring.

20. The method of claim 17, wherein the optical bypass is detected based on an auto remote Maintenance End Point (MEP) discovery and a timeout of an old remote MEP.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present disclosure is illustrated and described herein with reference to the various drawings, in which like reference numbers are used to denote like system components/method steps, as appropriate, and in which:

[0010] FIGS. 1A - 1B are network diagrams of a network including optical bypass equipment A1, B1, C1, D1, E1, F1 and network elements, nodes A, B, C, D, E, F, forming a G.8032 ring via the optical bypass equipment, with FIG. 1A illustrating normal conditions (no fault), and FIG. 1B illustrating a fault at the node E.

[0011] FIGS. 2A - 2B are network diagrams of the network including optical bypass equipment A1, B1, C1, D1, E1, F1 and network elements, nodes A, B, C, D, E, F, forming a G.8032 ring via the optical bypass equipment, with FIG. 2A illustrating normal conditions (no fault), and FIG. 2B illustrating a single fiber fault at node D and a dual fiber fault or node fault at node E.

[0012] FIGS. 3A - 3B are network diagrams of a network including network elements, nodes A, B, C, D, E, F, forming a G.8032 ring via the optical bypass equipment (not shown), with FIG. 3A illustrating normal conditions (no fault), and FIG. 3B illustrating a fault at the node A and a corresponding optical bypass event.

[0013] FIGS. 4 - 11 are tables of G.8032 request/state priority and of the G.8032 state machine with the addition of an adjacent node change based on an optical bypass event.

[0014] FIGS. 12 - 22 are network diagrams illustrating example faults and behaviors in the network with optical bypass.

[0015] FIG. 23 is a flowchart of a process for optical bypass with G.8032.

[0016] FIG. 24 is a block diagram of an example implementation of a node.

[0017] FIG. 25 is a block diagram of an example processing device.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0018] The present disclosure relates to systems and methods for preserving G.8032 ring redundancy and a loop free topology in the presence of optical bypass relays.

G.8032 Ring With Optical Bypass

[0019] FIGS. 1A - 1B are network diagrams of a network 10 including optical bypass equipment A1, B1, C1, D1, E1, F1 and network elements, nodes A, B, C, D, E, F, forming a G.8032 ring via the optical bypass equipment, with FIG. 1A illustrating normal conditions (no fault), and FIG. 1B illustrating a fault at the node E. FIGS. 2A - 2B are network diagrams of the network 10 including optical bypass equipment A1, B1, C1, D1, E1, F1 and network elements, nodes A, B, C, D, E, F, forming a G.8032 ring via the optical bypass equipment, with FIG. 2A illustrating normal conditions (no fault), and FIG. 2B illustrating a single fiber fault at node D and a dual fiber fault or node fault at node E.

[0020] The optical bypass equipment A1, B1, C1, D1, E1, F1, at each node, is configured to connect the nodes A, B, C, D, E, F to the ring under normal conditions (FIG. 1A), and to interconnect the ring for a passthrough when there is a nodal fault (FIG. 1B). The optical bypass equipment A1, B1, C1, D1, E1, F1 can be an optical protection switch, bypass switch, etc. That is, under normal conditions, the optical bypass device maintains connectivity to both ports of the connected ring node and each of the east/west ring ports to the adjacent optical bypass devices. Under nodal faults to the connected ring node, the optical bypass device switches to connect both ring ports to the adjacent optical bypass devices.

[0021] The basis of this disclosure is the use of optical bypass equipment (i.e., bypass A1, B1, C1, D1, E1, F1) to constitute a G.8032 ring (i.e., nodes A, B, C, D, E, F). FIGS. 1A - 1B depict the inner ring network elements representing the optical bypass devices and the outer ring network elements representing the packet switching devices operating the ITU-T G.8032 Ring Automatic Protection Switching (RAPS) protocol.

[0022] An optical bypass event can occur as a result of a nodal outage (e.g., faults, software upgrades, power outage) as depicted in FIG. 1B, or dual fiber faults to the same ring node, as depicted in FIG. 2B.

[0023] Under normal conditions, an optical bypass device (e.g., bypass D1) maintains connectivity to both ports of the connected ring node (e.g., node D) and each of the east/west ring ports to the adjacent optical bypass devices (e.g., bypass C1 & E1). In the event of a ring nodal fault (e.g., node D), the optical bypass connected node D to the G.8032 ring initiates a protection switch, whereby it switches connectivity directly between the ring nodes to each of adjacent optical bypass C1 and E1, resulting in a reconstituted ring.

[0024] Importantly, this optical bypass protection switch is invisible to the standard G.8032 ring protocol and ring nodes. As such, the optical bypass under these conditions is not detectable by adjacent G.8032 ring nodes (e.g., nodes C & E) and may result in incorrect forwarding information on the G.8032 ring. As such, the G.8032 ring nodes remaining on the ring, must be able to detect this change in the ring topology and take action to refresh its forwarding entries. This can result in prolonged blackholing scenarios. Actual customer reported outage durations is on the order of 2-3 minutes, until the configured Media Access Control (MAC) age out timer expires.

Adjacent Node Change Detection

[0025] The present disclosure leverages CCMs to monitor the G.8032 ring spans and to detect when an optical bypass event has occurred. FIGS. 3A - 3B are network diagrams of a network 10 including network elements, nodes A, B, C, D, E, F, forming a G.8032 ring via the optical bypass equipment (not shown), with FIG. 3A illustrating normal conditions (no fault), and FIG. 3B illustrating a fault at the node A and a corresponding optical bypass event.

[0026] In FIG. 3A, CCM sessions via Down MEPs 12 are created as shown. Of note, in this example, a ring block 14 is on a port of the node A facing the node F. The Down MEPs 12 are configured with auto Remote MEP discovery. All sessions created at same Maintenance Entity Group (MEG) Level with same MEG identifier and on the same Virtual Local Area Network (VLAN). In FIG. 3B, there is an optical bypass event at the node A. This is detected, If a new Remote MEP 16 is discovered and an old Remote MEP 16 has detected “CCM timeout”, then this is indicative of a change in ring topology (e.g., Optical Node Bypass).

[0027] By defining an approach as illustrated in FIGS. 3A - 3B to detect that an optical bypass event has occurred, this can enable the G.8032 ring to take action and flush its FDB using an existing RAPS FDB flush propagation event. The approach proposed to monitor and detect an optical bypass, can be simplified to detecting whether a G.8032 ring neighbor node has changed. When a G.8032 ring node comes up, it can monitor the ring spans by operating an IEEE 802.1ag Down MEP using a CCM session, on each RAPS ring port. The CCM interval is inconsequential to the operation of this approach and only serves to establish the detection performance, and for this reason it can be any value. In order to configure a MEP, a remote MEP ID is required.

[0028] There can be two approaches to determine the remote MEP ID. The first is to use a static configuration - the typical usage. The second approach which is proposed for this novelty is to use a dynamic discovery of the remote MEP. By using this approach method, a change in the remote MEP discovered can be used to detect if a ring node has changed. The novelty is in using this second approach to not only detect the neighbor change, but to also initiate the RAPS FDB flush propagation to re-establish the forwarding entries.

Previous Peer Channel Block Determination

[0029] However, not only is the optical bypass detection required, so is the recreation of any channel blocks 14 on the ring that have been bypassed, to ensure that the G.8032 ring does not form a network loop. This would require detecting if a neighbor node, before an optical bypass, had a channel block, as in the node A in FIG. 3A. The approach to detect this channel block status is to use a CCM port status Type-Length-Value (TLV) to exchange this information with neighbor nodes. Then following a bypass event, to install a channel block 18 to replace the bypassed block 14. This new channel block 18 could be temporary and may be removed if another channel block on the ring is detected via the monitoring of G.8032 RAPS PDU types reflecting that a channel block is installed somewhere else on the ring. If no event on the ring is detected that represents a channel block, the temporary channel block remains in place to guarantee the loop free topology of the ring. CCMs Tx with Port Status TLV - Port Status TLV set to psBlocked if MEP on Channel Block port, and otherwise set to psUp.

[0030] FIGS. 4 - 11 are tables of G.8032 request/state priority and of the G.8032 state machine with the addition of an adjacent node change based on an optical bypass event.

Failure Scenario Examples

[0031] The following FIGS. 12 - 22 all describe example faults and behaviors in the network 10 with optical bypass.

[0032] FIG. 12 illustrates the ring block on node A and a node D fault. There is an optical bypass at node D. The adjacent nodes C, E detect the bypass based on CCM timeout and new remote CCM discovered. The nodes C, E perform a Tx R-APS(Flush) and there is no state machine state change.

[0033] FIG. 13 illustrates the ring block on node A along with a node A fault. There is an optical bypass at node A. The adjacent nodes B, F detect the bypass based on CCM timeout and new remote CCM discovered. At the node B, there is a Tx R-APS(Flush) and there is no state machine state change. At the node F, the ring block is installed, there are state machine changes -- Tx R-APS(Flush), Tx R-APS(NR), Next state .fwdarw. PENDING.

[0034] FIG. 14 illustrates the ring block on node A along with a node F fault. There is an optical bypass at node F. The adjacent nodes A, E detect the bypass based on CCM timeout and new remote CCM discovered. The nodes A, E perform a Tx R-APS(Flush) and there is no state machine state change.

[0035] FIG. 15 illustrates a dual fault scenario where the ring block is initially on node A and a first fault on node B followed by a second fault on node A. With the first fault, there is an optical bypass at node B. The adjacent nodes A, C detect the bypass based on CCM timeout and new remote CCM discovered. The nodes A, C perform a Tx RAPS(Flush) and there is no state machine state change. With the second fault, there is an optical bypass at node A. The adjacent nodes F, C detect the bypass based on CCM timeout and new remote CCM discovered. At the node F, the ring block is installed, there are state machine changes -- Tx R-APS(Flush), Tx R-APS(NR), Next state .fwdarw. PENDING. At the node C, there is a Tx R-APS(Flush) and there is no state machine state change.

[0036] FIG. 16 illustrates a dual fault scenario where the ring block is initially on node A and a first fault on node A followed by a second fault on node F. With the first fault, there is an optical bypass at node A. The adjacent nodes B, F detect the bypass based on CCM timeout and new remote CCM discovered. At the node F, the ring block is installed, there are state machine changes -- Tx R-APS(Flush), Tx R-APS(NR), Next state .fwdarw. PENDING. At the node B, there is a Tx R-APS(Flush) and there is no state machine state change. With the second fault, there is an optical bypass at node F. The adjacent nodes E, B detect the bypass based on CCM timeout and new remote CCM discovered. At the node B, the ring block is installed, there are state machine changes -- Tx RAPS(Flush), Tx R-APS(NR), Next state .fwdarw. PENDING. At the node E, there is a Tx RAPS(Flush) and there is no state machine state change.

[0037] FIGS. 17 - 22 are various network diagrams illustrating multiple fault scenarios.

Process

[0038] FIG. 23 is a flowchart of a process 50 for optical bypass with G.8032. The process 50 can be realized in any of the nodes A, B, C, D, E, F in the network 10. Also, the process 50 can be a method having steps, implemented via an apparatus that is configured to execute the steps, as a non-transitory computer-readable medium having instructions for executing the steps, and the like. For example, the process 50 can be implemented by the node 100, the processing device 200, or any other suitable device.

[0039] The steps include operating an Operations, Administration, and Maintenance (OAM) session with an adjacent network element (step 52); and detecting an optical bypass in the G.8032 ring based on the OAM session (step 54). The steps can further include flushing a forwarding database of the network element based on the optical bypass (step 56). The steps can further include detecting prior to the optical bypass, that a neighboring node includes a ring block (step 58); and, subsequent to the optical bypass, installing a new channel block (step 60). The steps can further include removing the new channel block if another channel block is detected on the G.8032 (step 62).

[0040] The ring block can be detected via a Type-Length-Value (TLV) field in a packet associated with the OAM session. The OAM session can include Continuity Check Messages (CCMs). The optical bypass can be detected based on an auto remote Maintenance End Point (MEP) discovery and a timeout of an old remote MEP. An optical switching device can be configured to connect the ports to the G.8032 ring under normal conditions and to connect the ports together responsive to a node fault, thereby providing the optical bypass.

Example Node

[0041] FIG. 24 is a block diagram of an example implementation of a node 100, such as for any of the nodes A, B, C, D, E, F in the network 10. Those of ordinary skill in the art will recognize FIG. 24 is a functional diagram in an oversimplified manner, and a practical embodiment may include additional components and suitably configured processing logic to support known or conventional operating features that are not described in detail herein.

[0042] In an embodiment, the node 100 is a packet switch, but those of ordinary skill in the art will recognize the systems and methods described herein can operate with other types of network elements and other implementations that support SR networking. In this embodiment, the node 100 includes a plurality of modules 102, 104 interconnected via an interface 106. The modules 102, 104 are also known as blades, line cards, line modules, circuit packs, pluggable modules, etc. and generally refer to components mounted on a chassis, shelf, etc. of a data switching device, i.e., the node 100. Each of the modules 102, 104 can include numerous electronic devices and/or optical devices mounted on a circuit board along with various interconnects, including interfaces to the chassis, shelf, etc.

[0043] Two example modules are illustrated with line modules 102 and a control module 104. The line modules 102 include ports 108, such as a plurality of Ethernet ports. For example, the line module 102 can include a plurality of physical ports disposed on an exterior of the module 102 for receiving ingress/egress connections. Additionally, the line modules 102 can include switching components to form a switching fabric via the interface 106 between all of the ports 108, allowing data traffic to be switched/forwarded between the ports 108 on the various line modules 102. The switching fabric is a combination of hardware, software, firmware, etc. that moves data coming into the node 100 out by the correct port 108 to the next node 100. “Switching fabric” includes switching units in a node; integrated circuits contained in the switching units; and programming that allows switching paths to be controlled. Note, the switching fabric can be distributed on the modules 102, 104, in a separate module (not shown), integrated on the line module 102, or a combination thereof.

[0044] The control module 104 can include a microprocessor, memory, software, and a network interface. Specifically, the microprocessor, the memory, and the software can collectively control, configure, provision, monitor, etc. the node 100. The network interface may be utilized to communicate with an element manager, a network management system, etc. Additionally, the control module 104 can include a database that tracks and maintains provisioning, configuration, operational data, and the like.

[0045] Again, those of ordinary skill in the art will recognize the node 100 can include other components which are omitted for illustration purposes, and that the systems and methods described herein are contemplated for use with a plurality of different network elements with the node 100 presented as an example type of network element. For example, in another embodiment, the node 100 may include corresponding functionality in a distributed fashion. In a further embodiment, the chassis and modules may be a single integrated unit, namely a rack-mounted shelf where the functionality of the modules 102, 104 is built-in, i.e., a “pizza-box” configuration. That is, FIG. 24 is meant to provide a functional view, and those of ordinary skill in the art will recognize actual hardware implementations may vary.

Example Controller

[0046] FIG. 25 is a block diagram of an example processing device 200, which can form a control module for a network element, etc. The processing device 200 can be part of the network element, or a stand-alone device communicatively coupled to the network element. Also, the processing device 200 can be referred to in implementations as a control module, a shelf controller, a shelf processor, a system controller, etc. The processing device 200 can include a processor 202 which is a hardware device for executing software instructions. The processor 202 can be any custom made or commercially available processor, a central processing unit (CPU), an auxiliary processor among several processors associated with the processing device 200, a semiconductor-based microprocessor (in the form of a microchip or chipset), or generally any device for executing software instructions. When the processing device 200 is in operation, the processor 202 is configured to execute software stored within the memory, to communicate data to and from the memory, and to generally control operations of the processing device 200 pursuant to the software instructions. The processing device 200 can also include a network interface 204, a data store 206, memory 208, an I/O interface 210, and the like, all of which are communicatively coupled to one another and to the processor 202.

[0047] The network interface 204 can be used to enable the processing device 200 to communicate on a data communication network, such as to communicate to a management system, to the nodes 12, the like. The network interface 204 can include, for example, an Ethernet module. The network interface 204 can include address, control, and/or data connections to enable appropriate communications on the network. The data store 206 can be used to store data, such as control plane information, provisioning data, Operations, Administration, Maintenance, and Provisioning (OAM&P) data, etc. The data store 206 can include any of volatile memory elements (e.g., random access memory (RAM, such as DRAM, SRAM, SDRAM, and the like)), nonvolatile memory elements (e.g., ROM, hard drive, flash drive, CDROM, and the like), and combinations thereof. Moreover, the data store 206 can incorporate electronic, magnetic, optical, and/or other types of storage media. The memory 208 can include any of volatile memory elements (e.g., random access memory (RAM, such as DRAM, SRAM, SDRAM, etc.)), nonvolatile memory elements (e.g., ROM, hard drive, flash drive, CDROM, etc.), and combinations thereof. Moreover, the memory 208 may incorporate electronic, magnetic, optical, and/or other types of storage media. Note that the memory 208 can have a distributed architecture, where various components are situated remotely from one another, but may be accessed by the processor 202. The I/O interface 210 includes components for the processing device 200 to communicate with other devices.

[0048] It will be appreciated that some embodiments described herein may include or utilize one or more generic or specialized processors (“one or more processors”) such as microprocessors; Central Processing Units (CPUs); Digital Signal Processors (DSPs): customized processors such as Network Processors (NPs) or Network Processing Units (NPUs), Graphics Processing Units (GPUs), or the like; Field-Programmable Gate Arrays (FPGAs); and the like along with unique stored program instructions (including both software and firmware) for control thereof to implement, in conjunction with certain nonprocessor circuits, some, most, or all of the functions of the methods and/or systems described herein. Alternatively, some or all functions may be implemented by a state machine that has no stored program instructions, or in one or more Application-Specific Integrated Circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic or circuitry. Of course, a combination of the aforementioned approaches may be used. For some of the embodiments described herein, a corresponding device in hardware and optionally with software, firmware, and a combination thereof can be referred to as “circuitry configured to,” “logic configured to,” etc. perform a set of operations, steps, methods, processes, algorithms, functions, techniques, etc. on digital and/or analog signals as described herein for the various embodiments.

[0049] Moreover, some embodiments may include a non-transitory computer-readable medium having instructions stored thereon for programming a computer, server, appliance, device, at least one processor, circuit/circuitry, etc. to perform functions as described and claimed herein. Examples of such non-transitory computer-readable medium include, but are not limited to, a hard disk, an optical storage device, a magnetic storage device, a Read-Only Memory (ROM), a Programmable ROM (PROM), an Erasable PROM (EPROM), an Electrically EPROM (EEPROM), Flash memory, and the like. When stored in the non-transitory computer-readable medium, software can include instructions executable by one or more processors (e.g., any type of programmable circuitry or logic) that, in response to such execution, cause the one or more processors to perform a set of operations, steps, methods, processes, algorithms, functions, techniques, etc. as described herein for the various embodiments.

[0050] Although the present disclosure has been illustrated and described herein with reference to preferred embodiments and specific examples thereof, it will be readily apparent to those of ordinary skill in the art that other embodiments and examples may perform similar functions and/or achieve like results. All such equivalent embodiments and examples are within the spirit and scope of the present disclosure, are contemplated thereby, and are intended to be covered by the following claims. Moreover, it is noted that the various elements, operations, steps, methods, processes, algorithms, functions, techniques, etc. described herein can be used in any and all combinations with each other.