WO2009000211A1

WO2009000211A1 - Method, network device and network system for network clock tracing

Info

Publication number: WO2009000211A1
Application number: PCT/CN2008/071455
Authority: WO
Inventors: Junjie Feng; Yu Wang; Min Zhao; Kuiwen Ji; Xinghua Shi; Baoquan Rao
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2007-06-26
Filing date: 2008-06-26
Publication date: 2008-12-31
Also published as: CN101335609A; CN101335609B

Abstract

A method, a network device and a network system are disclosed. The clock tracing path of the network device in the network is computed. If the clock tracing path of the network device changes, a request message is sent to the uplink neighbour network device on the clock tracing path of said network device. Then a response message from the uplink neighbor network device is received, and clock tracing is performed based on the response message. Fast clock handover and clock tracing can be achieved through above implementation.

Description

Network clock tracking method, network device and network system

The present invention relates to the field of communications technologies, and in particular, to a network clock tracking method, a network device, and a network system.

Background technique

In a communication network, the clock is a very important factor because it is directly related to the quality of the transmitted service. If there is a problem with the clock, it will cause the pointer adjustment of the Synchronous Digital System (SDH) to change, and the data stream will be slipped and damaged, resulting in data errors. Therefore, it is necessary to ensure clock synchronization of the devices on the entire network, and to ensure fast switching of clock tracking of network devices of the entire network after the topology of the network changes and the network is initialized.

In the traditional network, because the topology of the network is relatively simple, mainly for the ring network and the chain network structure, the clock tracking operation can be completed by using the Synchronization Status Message (SSM) protocol. . However, with the development of the transmission network, the topology of the ring network and the chain network gradually evolved into the topology of the mesh network (MESH network). In the MESH network, the SSM protocol does not start due to its functional limitations. Adapt to the development of transmission networks.

In the traditional clock tracing technology, all network devices are required to configure the priority table of the corresponding reference clock source according to the clock tracing condition, and at the same time configure two reference clock sources for each network device, one of which is used as protection. In the MESH network, the traditional clock tracking technology has two main problems:

1. In the MESH network, since the number of other network devices connected to each network device is more than that of the traditional ring network and chain network, generally more than two, in such a situation, it is difficult to manually plan a suitable one. Clock tracking path.

2. Most network devices can only be configured with two reference clock sources as protection. When the reference clock source configured by the network device fails, the network device cannot find the clock source that can be tracked. Summary of the invention Embodiments of the present invention provide a method for network clock tracking, a network device, and a network system. When a topology of a network changes and a network is initialized, each network device in the network can perform clock tracking quickly.

Embodiments of the present invention are implemented by the following technical solutions:

A method for network clock tracking, including:

Calculating a shortest path to the network device directly connected to the clock source, and using the shortest path as a clock tracking path;

Determining whether the clock tracking path is changed;

Sending a request message to an adjacent upstream network device on the clock tracking path if the clock tracking path changes;

Receiving a response message returned by the adjacent upstream network device, and performing clock tracing according to the response message.

A network device, comprising:

a calculation module, configured to calculate a shortest path to the network device directly connected to the clock source, and use the shortest path as a clock tracking path;

a determining module, configured to determine whether the clock tracking path is changed;

a sending module, configured to send a request message to an adjacent upstream network device on the clock tracking path when the clock tracking path changes;

And a receiving processing module, configured to receive a response message returned by the neighboring upstream network device, and perform clock tracking according to the response message.

A network system includes at least one network device directly connected to a clock source, a first network device, and a second network device, where the second network device is an adjacent upstream network device of the first network device;

The network device directly connected to the clock source is configured to calculate a shortest path to a clock source connected thereto, and use the shortest path as a clock tracking path;

The first network device is configured to calculate a maximum number of network devices that are directly connected to the clock source. a short path, and the shortest path is used as a clock tracking path, and when the clock tracking path changes, sending a request message to the second network device;

The second network device is configured to receive a request message sent by the first network device, and return a response message to the first network device when the clock tracking path of the second network device is determined;

The first network device is further configured to receive a response message returned by the second network device, and perform clock tracking according to the response message.

A computer program product comprising a set of instructions, the sequence of instructions being executed by a network device comprising the steps of:

Calculating a shortest path to the network device directly connected to the clock source, and using the shortest path as the clock tracking path;

Determining whether the clock tracking path is changed;

It can be seen from the specific implementation provided by the foregoing embodiments of the present invention that after the topology of the network changes and the network is initialized, each network device in the network can perform fast clock tracking according to the response message, and implement a fast clock. Switching, and using a serial mechanism ensures that the clock tracking path does not loop. Thus, the present invention overcomes the complicated clock tracking path planning problem in the conventional clock tracking technology, and can quickly and automatically establish a new clock tracking path in the case of a change in the network topology.

DRAWINGS

1 is a schematic diagram of a clock tracking path in a case where a network uses a clock source according to an embodiment of the present invention;

2 is a schematic diagram of a clock tracking path after a link failure occurs in a network according to an embodiment of the present invention; FIG. 3 is a schematic diagram of a clock tracking path when a network uses two clock sources according to an embodiment of the present invention; Intention; is a schematic diagram of the tracking path;

FIG. 5 is a flowchart of a method for clock tracking according to an embodiment of the present invention; FIG.

FIG. 6 is a schematic structural diagram of a network device according to an embodiment of the present invention.

detailed description

The method of the embodiment of the present invention is expressed in the specific implementation process as follows:

As shown in FIG. 5, it is a flowchart of a method for clock tracing in the embodiment of the present invention. The implementation process is as follows: Step 501: The network device calculates a clock tracking path of the network device, where the topology of the network changes or the network During initialization, the network device determines the network topology change and obtains the corresponding algorithm (such as the shortest path first algorithm, the minimum spanning tree algorithm, etc.), and the clock tracking path is from the network device directly connected to the clock source to the network device. The shortest path, which determines the network topology change can be achieved by receiving the network topology change message.

Step 502: The network device determines whether the clock tracking path of the network device is changed, specifically, whether the calculated clock tracking path is consistent with the original clock tracking path of the network device. If not, proceed to step 503. If they are consistent, enter Step 505.

Step 503: The network device sends a request message to the neighboring upstream network device on the clock tracking path calculated by step 501. The request message carries the information of the clock tracking path between the neighboring upstream network device and the network device directly connected to the clock source calculated by the network device, and the clock tracking path calculated in step 501 removes the network device itself, that is, Clock tracking path of adjacent upstream network devices. After receiving the request message, the neighboring upstream network device sends the response message to the network device if its clock tracking path is determined. The clock tracking path of the adjacent upstream network device is determined, specifically, the clock tracking path is not changed, or although its clock tracking path changes, its new clock tracking path has been determined and established.

The adjacent upstream network device determines the clock of the adjacent upstream network device according to the clock tracking path of the received request message and the original clock tracking path of the adjacent upstream network device. Whether the trace path changes.

The specific clock tracking path has been determined and established as follows: After sending a request message to the neighboring upstream network device on the clock tracking path where the adjacent upstream network device is located, the response message returned by the neighboring upstream network device is received. And performing clock tracking according to the response message.

Step 504: The network device receives the response message returned by the neighboring upstream network device, and performs clock tracking according to the response message. At this time, the new clock tracking path of the network device is successfully established.

Step 505: The network device then determines whether the request message of its neighboring downstream network device is received. If yes, the process proceeds to step 506, otherwise the network device has no further action.

Step 506: The network device sends a response message to its neighboring downstream network device, and the downstream network device performs clock tracking according to the response message.

To avoid the impact of frequent network topology changes, you can preset a certain delay time. After receiving the network topology change message, each network device performs a certain delay (for example, 5 seconds) before performing clock tracking. The calculation of the path.

The network device in the network and the adjacent upstream network device on the clock tracking path where the network device is located may be an SDH optical transmission device, a wavelength division multiplexing (WDM) optical transmission device, or a synchronous optical network ( Synchronous Opt ica l Network , SONET ) Network equipment such as optical transmission equipment.

The fast tracking method of the request-response mechanism in the embodiment of the present invention can automatically and quickly determine the clock tracking path of each network device in the network when the topology of the network changes and the network is initialized. The clock automatically switches and tracks automatically, which overcomes the problem that it is difficult to plan a suitable clock tracking path in the traditional clock tracking technology and it is difficult to automatically calculate a new tracking path after the network topology changes. And because the network device carries the information of the clock tracking path of the neighboring upstream network device in the request message, the neighboring upstream network device can select the clock tracking path in the request message and the clock tracking path obtained by the adjacent upstream network device. In comparison, it is determined whether the two clock tracking paths are consistent. When the two are consistent, the adjacent upstream network device sends a response message to the network device, and a request-response serial mechanism is provided, thereby ensuring the network. There is no clock tracking loop in the middle.

In addition, since the formation of the clock interlock is a special case of generating a clock tracking loop, each network device can determine that the network device is not being used by the network device when tracking a network device by using the method of the embodiment of the present invention. In turn, tracking can also avoid the occurrence of clock interlocks.

In order to facilitate a further understanding of the method of the embodiments of the present invention, the method of the embodiments of the present invention will be described in detail below with reference to FIGS. 1 and 2.

It is assumed that after the network is initialized, a clock tracking path as shown by the arrow in Fig. 1 is formed, and the arrow points to the downstream network device of the entire network clock tracking tree. The clock tracking tree is obtained by the network device after receiving the message that the network topology changes, and is calculated by a corresponding algorithm (such as a shortest path first algorithm, a minimum spanning tree algorithm, etc.). When the link between A-B and D-G is interrupted, each network device receives a message that the network topology has changed. After a certain delay (for example, 5 seconds), recalculate the clock tracking path as shown in Figure 2, as indicated by the arrow in the figure. After receiving the network topology change message, the A, C, D, and F network devices in the figure calculate the clock tracking path of the network device. If no change is found, the device does not need to send a request message to the respective upstream network device. After receiving the network topology change message, the B, E, G, and H network devices calculate the clock tracking path of the local network device and find that the clock tracking path changes. Therefore, the network device sends a request message to the respective upstream network device. The request message includes the calculated information of the clock tracking path of the upstream network device of each network device to the network device A directly connected to the clock source. After the upstream network device C of B and the upstream network device F of the E and the G receive the request message, the clock tracking path of the network device does not change, and the clock of the network device to the A carried in the request message is found. If the tracking path is consistent with the clock tracking path saved by the network device, the response message is sent to the node that sends the request message, and the B, E, and G network devices perform clock tracing according to the response message.

However, when the E network device receives the request message of the H network device, the clock tracking path of the network device changes, and the response message of the upstream network device F is not received, and the clock is tracked, so the response cannot be sent to H temporarily. Message. After E receives the response message from F, E performs clock tracking according to the response message, and E sends a response message to H, so that H should send according to E. Answer the message for clock tracking.

At the time of network initialization, the method of the embodiment of the present invention can also be taken to form an initial clock tracking path and perform corresponding clock tracking.

The above embodiment is proposed for a network connected to a clock source. If the network connection has two or more clock sources of the same quality level and priority, the clock tracker can be automatically formed by using the method of the embodiment of the present invention. network. If there is a network device in the network, and the shortest path of the network device to the at least two clock sources accessing the network device is the same, the network device selects a clock source to access the network device tracking. This will be further explained below in conjunction with Figs. 3 and 4.

Regarding which clock source is selected by the network device for tracking, a certain arbitration mechanism can be obtained. These arbitration mechanisms can be different under different circumstances.

If multiple clock sources are connected to the entire network, and their clock quality levels are different, the network device selects the network device directly connected to the clock source with the highest clock quality level to track; if the entire network is connected to multiple clock sources with the same clock quality level, The network device selects the network device directly connected to the clock source with the highest priority to track. If the entire network is connected to multiple clock sources with the same clock quality level and priority, the network device compares the network device to the network connected to these clock sources. The shortest path of the device, and select the one with the shortest path to track; if all of the above are the same, you can further distinguish between the rules that can produce a unique result, for example, which network device is directly connected to the clock source If the node ID is small, which device is tracked.

The arbitration mechanism involved in the following examples is the last one.

As shown in Figure 3, the SSM quality level and priority of clock source 1 and clock source 1 are the same. Each network device calculates the network device to the network device directly connected to the clock source (see network device A and network device J in the figure). The shortest path of the ) forms a clock tracking path as indicated by the arrow in FIG. In the figure, the E network device has the same shortest path to A and J. When determining the clock tracking path of the network device, the arbitration mechanism is selected to select the clock source of the tracking. For example, in this embodiment, E preferentially selects a network device (ie, network device A) connected to a clock source with a smaller number to perform tracking. The G network device and the I network device do similar processing. Thus the clock tracking path of the entire network is formed. Use this on this basis The method of the embodiment of the invention can realize fast clock tracking between network devices of the entire network.

If the clock source 1 fails, the method of the embodiment of the present invention can form a clock tracking tree of the network device as shown in FIG. 4 and the clock source connected to the clock source 2 to access the network device J, as shown in FIG. Shown.

Of course, if there is no need to divide multiple clock subnets, you can also disable this function, configure different priorities and other methods for each clock source connected to the network, making the network a clock tracing network with only one clock source.

It should be understood that the software implementing the method of the present invention for clock tracking can be stored in a computer readable medium. When the software is executed, it includes the following steps:

Calculating, by the network device, a shortest path of the network device directly connected to the clock source as a clock tracking path; if the clock tracking path changes, sending a request message to an adjacent upstream network device on the clock tracking path; A response message returned by the adjacent upstream network device, and clock tracking is performed according to the response message. The readable medium can be: ROM/RAM, disk, or optical disk, and the like.

Embodiments of the present invention also provide a network device. The network device includes a calculation module, a determination module, a transmission module, and a reception processing module.

The calculation module 61 is configured to determine a network topology change and calculate a clock tracking path of the network device. The determining the network topology change includes receiving the network topology change message, and the network device calculates the clock tracking path of the network device, which can be obtained by using a corresponding algorithm (such as a shortest path first algorithm, a minimum spanning tree algorithm, etc.), where the clock tracking path is The shortest path from the clock source to the network device to the network device.

The determining module 62 is configured to compare the acquired clock tracking path with the original clock tracking path to determine whether the clock tracking path of the network device changes.

The sending module 63 is configured to: when the clock tracking path changes, the network device sends a request message to the neighboring upstream network device on the clock tracking path, where the request message includes information of a clock tracking path of the adjacent upstream network device. The sending module 63 is further configured to use a clock tracking path of the network device. When determined, a reply message is sent to an adjacent downstream network device on the clock tracking path of the network device. The clock tracking path is determined, specifically, the clock tracking path of the network device is unchanged, or although the clock tracking path of the network device changes, its new clock tracking path has been determined and established.

The above new clock tracking path has been determined and established as follows: A response message returned by a neighboring upstream network device on its clock tracking path is received, and clock tracking is performed according to the response message. If the returned response message is not received, the network device waits until a response message is received, and after the clock is tracked according to the response message, the response message is sent to the neighboring downstream network device.

The receiving processing module 64 is configured to receive a response message returned by the neighboring upstream network device, and perform clock tracking according to the response message, that is, the clock of the network device can track the clock of the adjacent upstream network device. The receiving processing module is further configured to receive a request message sent by the neighboring downstream network device on the clock tracking path of the network device to the network device, where the request message includes information of a clock tracking path of the network device.

Network devices, adjacent downstream network devices on the clock tracking path of the network device, and adjacent upstream network devices on the clock tracking path of the network device, the clock source access network device may be an SDH optical transmission device, wavelength division multiplexing (Wave) Length Divi s ion Mul t iplex, WDM ) Optical transmission equipment, optical synchronization network (Synchronous Opt ica l Ne twork, SONET) optical transmission equipment and other network equipment.

In the embodiment of the network device of the present invention, when the topology of the network changes and when the network is initialized, the network devices in the network automatically track the clock according to the response message, and implement automatic clock switching. And tracking, overcoming the difficulty of planning a suitable clock tracking path in traditional clock tracking techniques. Moreover, since the request message contains the clock tracking path of the adjacent upstream network device on its clock tracking path, a strict request-response serial mechanism is used, so that the clock tracking loop can be effectively prevented.

An embodiment of the present invention further provides a network system, including at least one network device directly connected to a clock source, a first network device, and a second network device, where the second network device is a first network Adjacent upstream network device of the network device;

Generally, when the network initialization or the network topology changes, the first network device and the second network device respectively calculate clock tracking paths of the network devices directly connected to the clock source. The network device directly connected to the clock source further receives the request message sent by the other network device, and sends a response message to the other network device.

The first network device is configured to obtain a shortest path to the network device directly connected to the clock source, and use the shortest path as a clock tracking path, and when the clock tracking path changes, to the second network device Sending a request message, the second network device returns a response message to the first network device when its clock tracking path is determined. The clock tracking path of the second network device is determined by: the second network device discovering that its clock tracking path has not changed, or although a change has occurred, a new clock tracking path has been determined and established. The first network device receives a response message returned by the second network device, and performs clock tracking according to the response message.

The specific process of the above clock can be understood as follows: When a network device determines that the clock path of the network device changes, it sends a request message to the neighboring upstream node of the network device on the new clock tracking path, and If the upstream node finds that the clock tracking path of the network device has also changed, the same action is taken until the request message reaches a certain network device. The network device finds that the clock tracking path of the network device has not changed, or although it has occurred. Change, but the new clock tracking path has been determined and established, and a response message is sent to the downstream node. The downstream node establishes a clock tracking path for clock tracking according to the information in the response message.

The clock tracking path is the shortest path from the clock source to the network device to the network device. An adjacent upstream network device, located on a clock tracking path of the network device, including a network device directly connected to the clock source. The request message includes information of a clock tracking path of the network device. The neighboring upstream network device receives the request message and sends a response message to the network device if its clock tracking path is determined.

The clock tracking path determination means that the clock tracking path of the adjacent upstream network device has not changed; or although the clock tracking path of the network device changes, its new clock tracking path has been determined and built. Standing.

The first network device, the second network device, and the network device directly connected to the clock source, and other network devices in the network system may be network devices such as an SDH optical transmission device, a WDM optical transmission device, and a SONET optical transmission device. .

In the embodiment of the network system of the present invention, when the topology of the network changes and when the network is initialized, the network devices in the network automatically and automatically track the clock according to the response message, thereby realizing automatic clock switching and Tracking overcomes the difficulty of planning a suitable clock tracking path in traditional clock tracking techniques. And because the request message carries the information of the clock tracking path of its neighboring network device, a strict request-response serial mechanism is used, so that the generation of the clock tracking loop can be effectively prevented.

The above is only the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any change or replacement that can be easily conceived by those skilled in the art within the technical scope of the present invention is All should be covered by the scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

Claim

A method for tracking network clocks, comprising:

Determining whether the clock tracking path is changed;

Receiving a response message returned by the adjacent upstream network device, and performing clock tracking according to the response message.

2. The method according to claim 1, wherein the receiving the response message further comprises:

The neighboring upstream network device receives the request message, and if the clock tracking path of the neighboring upstream network device determines, sends a response message.

3. The method according to claim 2, wherein the clock tracking path is determined, and more specifically:

The clock tracking path of the adjacent upstream network device is unchanged; or the clock tracking path of the adjacent upstream network device changes, but its new clock tracking path has been determined and established.

The method according to claim 3, wherein the request message includes information of a clock tracking path of the adjacent upstream network device, and a clock tracking path of the adjacent upstream network device is calculated to arrive and When the shortest path of the network device directly connected to the clock source is obtained;

The adjacent upstream network device determines whether the clock tracking path of the adjacent upstream network device changes according to the clock tracking path of the received request message and the original clock tracking path of the adjacent upstream network device.

The method according to claim 1 or 2, wherein, if the network is connected to at least two clock sources, and the clock tracking path length of the at least two clock source access network devices is the same, according to arbitration The mechanism selects a network device directly connected to the clock source for tracking.

6. A network device, comprising:

a calculation module (61), configured to calculate a shortest path to the network device directly connected to the clock source, and use the shortest path as a clock tracking path;

a determining module (62), configured to determine whether the clock tracking path is changed;

a sending module (63), configured to send a request message to an adjacent upstream network device on the clock tracking path when the clock tracking path changes;

The receiving processing module (64) is configured to receive a response message returned by the neighboring upstream network device, and perform clock tracking according to the response message.

7. The network device according to claim 6, wherein

The receiving processing module (64) is further configured to receive a request message sent by an adjacent downstream network device on the clock tracking path;

The sending module (63) is further configured to send a response message to the neighboring downstream network device when the clock tracking path is determined.

The network device according to claim 7, wherein the clock tracking path is determined, and more specifically:

The clock tracking path of the network device is unchanged; or the clock tracking path of the network device changes, but its new clock tracking path has been determined and established.

A network system, comprising at least one network device directly connected to a clock source, a first network device, and a second network device, wherein the second network device is an adjacent upstream network device of the first network device ;

The first network device is configured to calculate a shortest path to the network device directly connected to the clock source, and use the shortest path as a clock tracking path, and when the clock tracking path changes, to the second network The device sends a request message;

The second network device is configured to receive a request message sent by the first network device, and in the second network When the clock tracking path of the device is determined, the response message is returned to the first network device; the first network device is further configured to receive a response message returned by the second network device, and perform clock tracking according to the response message.

10. A computer program product, comprising: a set of instruction sequences, the sequence of instructions being executed by a network device comprising the steps of:

Determining whether the clock tracking path is changed;