Description

A METHOD AND SYSTEM FOR THE PROTECTION OF ETHERNET RINGS

Technical area

This invention involves a type of protection method for Ethernet rings, specifically a type of protection method for Ethernet rings with multicast services, and a protection system for Ethernet rings which corresponds to this method.

Technical background

Current Ethernet applications cover a range of areas including access networks, metropolitan area networks and even backbone networks. However, as broadband data networks continue to develop, the existing Ethernet-based metropolitan area network systems face an enormous challenge. Existing network infrastructures are unable to provide operator-grade service protection methods, and where network disconnections occur due to failures in fiber optics and equipment, it is necessary to provide dependable protection for and recovery of services. It is apparent from existing technologies that Ethernet ring-based structures can provide effective protection for client services.

At the same time, the continual development of broadband multimedia networks has led to the emergence of a steady stream of broadband network applications. IP TV, video conferencing, data and information distribution, multimedia distance learning and other such broadband applications all present a challenge for the load capacity of existing broadband multimedia networks. Traditional

networks built on unicast technology have been unable to meet the requirements of these emerging broadband applications in terms of bandwidth and network service quality. Multicast (also known as multiple broadcast or IP group broadcast) technology is a type of TCP/IP network technology which allows one or multiple servers (multicast sources) to send single data packets to multiple servers . Multicast services which use multicast technologies to carry out transmissions are already widely used in broadband network applications .

There are many types of protection method for Ethernet rings. One such method is the Ethernet ring protection (ERP) protocol, a two-level protocol protection method that carries out rapid failure detection and recovery for links within the topological structure of an Ethernet ring.

The service protection time to achieve link or equipment failover with the help of Ethernet rings is generally set at around 50 milliseconds, and this requirement must be met regardless of whether unicast or multicast technology is used. Currently, in unicasts, this requirement can be met by using said Ethernet ring protection protocol; however, for multicasts, this protocol is unable to meet said requirement for failover time.

Invention content

The main object of this invention is therefore to provide a type of protection method for Ethernet rings to enable failover time levels for multicast services running on Ethernet that are acceptable to clients.

In order to achieve this object, the specific technical solution according to the invention is implemented as follows: A type of protection method for an Ethernet ring which is composed of at least one Ethernet node and includes at least one domain; each of said domains includes at least one active link and at least one protection link, as well as at least one redundancy manager. This method includes the following steps:

(1) Each active node of an active link within said domain notifies the other Ethernet nodes within the domain of its multicast information .

(2) Each Ethernet node within said domain receives the multicast information from said active nodes and updates the Ethernet node's multicast information table according to said multicast information .

In step (1), each active node of an active link within said domain notifies the other Ethernet nodes within the domain of its multicast information synchronously.

In step (1), each active node of an active link within said domain notifies the other Ethernet nodes within the domain of its multicast information via a bridge protocol data unit (BPDU) .

The interval between transmissions from each active node of an active link within said domain to their neighboring bridge protocol data units is shorter than the failover time of the Ethernet ring.

In step (2), each Ethernet node within said domain receives the multicast information sent by said active nodes via the bridge

protocol data units and updates the Ethernet node's multicast information table according to said multicast information.

The multicast information in the bridge protocol data unit includes at least one of the following information items: Ethernet node identifiers, domain names, virtual local area network (VLAN) group identification (GID) for Ethernet ring protection, and multicast group identification (GID) for Ethernet ring protection.

In step (1), each active node of an active link within said domain uses the polling method or the disconnection method to notify the other Ethernet nodes within the domain of its multicast information.

In step (1), the other Ethernet nodes within said domain are the active nodes of the active link or the protection nodes of the protection link.

This invention also proposes a type of protection system for an Ethernet ring which comprises at least one Ethernet node and includes at least one domain. Each of said domains includes at least one active link and at least one protection link, as well as at least one redundancy manager. Said Ethernet ring also includes at least one transmitter unit and at least one receiver unit; the transmitter unit sends multicast information from each active node of the active link(s) within said domain to the other Ethernet nodes within the domain; the receiving unit receives the multicast information sent by the transmitter unit and updates the multicast information table of the Ethernet nodes within the domain according to said multicast information.

Said transmitter unit is located in an active node of an active link within the domain, and said receiver unit is located in an Ethernet node within said domain.

It is therefore apparent that the protection method and system for Ethernet rings provided according to the invention has the following features and advantages:

(1) The method according to the invention is able to notify the protection link of the active link's multicast information before a failure occurs in an active link or after a failure occurs in an active link. If a link fails, the protection link is able to obtain the active link's multicast information within a short time and thereby take over operation of the traffic package; moreover, the recovery time for failures in dynamic multicast services can be reduced from seconds to milliseconds, thus reducing the protection time.

(2) The method according to the invention is a supplement to the existing Ethernet ring protection protocol (ERP) which requires no alterations to existing equipment, and the cost of using the method according to the invention is therefore extremely low.

Explanation of drawings

More detailed descriptions of specific embodiments according to the invention are given below with the aid of the diagrams, wherein:

Figure l isa schematic diagram of the Ethernet protection protocol (ERP) .

Figure 2 is a schematic diagram showing the initial state of an Ethernet ring using ERP.

Figure 3 is a schematic diagram showing the normal state of an Ethernet ring using ERP.

Figure 4 is a schematic diagram showing the state of an Ethernet ring using ERP when a failure occurs and the method according to the invention is therefore used to carry out protection. Figure 5 is a schematic diagram showing recovery and return to the normal state for an Ethernet ring using ERP.

Specific embodiments

Figure l isa schematic diagram of the Ethernet protection protocol (ERP) . Ethernet nodes NE1~NE7 in Figure 1 form a physical Ethernet ring which includes multiple logical domains, and each of these domains includes an active link and a protection link. For example, in the domain shown in Figure 1, Ethernet nodes RM A, NE2, NE3, NE4 and NE5 have formed an active link, as shown by the solid line in Figure 1; while NEl, NE7 and NE6 have formed a protection node, as shown by the broken line in Figure 1. One node within this domain has been designated as the redundancy manager RM A. The other nodes on the Ethernet ring have been designated as ordinary switching nodes .

In general, one multicast source sends service information to the nodes in one domain. Multiple virtual local area networks (VLAN) generally exist within a single domain, and each VLAN generally includes multiple multicast groups.

The RM A processes control information from the ERP and maintains the information of the active link and the protection link in the domain, including information such as which nodes within the domain

are active nodes, which nodes are protection nodes and whether an active node has failed and been disconnected. In addition, the RM node has two ports on the ring in said domain, one of which is deployed by the RM as the primary port (P) , while the other is deployed by the RM as the secondary port (S) .

In the domain where the RM is located, the secondary port is blocked for all non-ERP control information within the multicast group for the VLANs, as shown by the broken-line circles below the RM in Figure 1. In this way, the RM effectively separates the primary port (P) and the secondary port (S) , thereby preventing the formation of short circuits on the Ethernet ring. Despite the block, ERP control information may still be sent or received via the secondary port, so that when traffic packages are operating on the active link, control information will also be operating; no traffic packages from the domain will be operating on the protection link, upon which only control information will operate.

Figure 2 is a schematic diagram showing the initial state of an Ethernet ring using ERP. A multicast source is shown on the right-hand side of Figure 2. Before information is distributed by this multicast source via Ethernet, the multicast information tables of all Ethernet nodes within domains associated with this multicast source are empty, including those of the active link nodes and the protection link nodes, i.e. the multicast information tables of NE1-NE7 and RM A are all empty.

Figure 3 is a schematic diagram showing the normal state of an Ethernet ring using ERP. Said multicast source distributes service information to all nodes within the domain via the Ethernet ring.

The nodes of the active links within said domain are able to obtain multicast information from the service information distributed by the multicast source, and then write it into the multicast information table of the active link nodes; in other words, RM A, NE2, NE3 NE4 and NE5 respectively obtain multicasting information from the service information distributed by the multicast source and write this information into their respective multicast information tables. The nodes on the protection link within said domain cannot process the service information from the multicast source, as the secondary port is blocked, and the multicast information tables of NEl, NE7 and NE6 therefore remain empty.

Figure 4 is a schematic diagram showing the state of an Ethernet ring using ERP when a failure occurs and the method according to the invention is therefore used to carry out protection. The circles drawn with a solid line in Figure 4 indicate that a failure in the Ethernet ring has occurred at the corresponding location. Once the RM discovers by polling, disconnection or other failure detection mechanisms that a failure has occurred in the link, the RM opens the previously blocked secondary port (S) , allowing traffic packages to operate on the original protection link as well.

Then, each of the active nodes in the active link (NE2, NE3, NE4, NE5 and RM A) notifies the other Ethernet nodes within said domain of the multicast information in their multicast information tables . The so-called "other Ethernet nodes" include both the active nodes and the protection nodes. The multicast information sent by the active nodes is control information. Generally, each active node within an active link may inform the other Ethernet nodes within the domain of its multicast information via the BPDU. The multicast

information within the BPDU includes Ethernet node identifiers, domain names, virtual local area network (VLAN) group identification (GID) for Ethernet ring protection and multicast group identification (GID) for Ethernet ring protection (for the sake of simplicity, only multicast GID is shown in Figures 3 to 5) .

Ethernet node identifiers indicate from which node the multicast information was sent. If the Ethernet node identifier information in the BPDU received by an Ethernet node within said domain is different from the node identifier of the Ethernet node itself, the Ethernet node will receive the multicast information held by said BPDU. If the Ethernet node identifier information in the BPDU received by an Ethernet node within said domain is the same as the node identifier of the Ethernet node itself, the Ethernet node will discard the multicast information held by the BPDU. In this way, duplication can be avoided. The domain name indicates the domain in which the active node and the protection node are located, while virtual local area network (VLAN) group identification (GID) for Ethernet ring protection indicates which multicast groups are contained in each VLAN. Each multicast group has at least one port.

After each Ethernet node within the domain completes receipt of the multicasting information held by the BPDU, each node updates its own multicast information table according to the content of the multicast information.

The process in which each active node in the active link sends its multicast information is dynamic, continuing until the multicast information of every Ethernet node within the domain which uses

ERP becomes identical; in other words, the multicast information of every Ethernet node within the domain which uses ERP is synchronized. There is a certain time interval between two adjacent BPDUs sent by each active node of an active link. This time interval should be at least shorter than the failover time required by the Ethernet ring, generally 50 milliseconds, in order to ensure the synchronization of the multicast information of said Ethernet nodes .

Figure 5 is a schematic diagram showing recovery and return to normal state for an Ethernet ring using ERP. After the multicast information of all nodes within the domain is synchronized, the protection link within the diagram becomes a new active link, and the active link becomes a new protection link; in other words, RM A, NEl, NE7, NE6 and NE5 are the new active nodes, while NE2, NE3 and NE4 are the new protection nodes. Multicast clients can obtain service information from multicast sources via a new active link. The RM node redeploys the primary port (P) and secondary port (S) within said domain, as illustrated by the broken-line circles in Figure 5.

The multicast information notification method used in the above exemplary embodiment is the disconnection method. In addition to the disconnection method, other methods such as the polling method may also be used. The difference between the disconnection method and the polling method is that in the former, the multicast information of active nodes in an active link is sent to the protection node in the protection link after a link failure occurs, while in the latter, the multicast information of active nodes in an active link is sent to the protection node in the protection

link before a link failure occurs.

Furthermore, Figure 1 also shows an exemplary embodiment for the protection system for Ethernet rings according to the invention. Ethernet nodes NE1-NE7 in Figure 1 form a physical Ethernet ring which includes multiple logical domains, and each of these domains includes an active link and a protection link. For example, in the domain shown in Figure 1, Ethernet nodes RM A, NE2, NE3, NE4 and NE5 have formed an active link, as shown by the solid line in Figure 1, while NEl, NE7 and NE6 have formed a protection link, as shown by the broken line in Figure 1. One node within this domain has been designated as the redundancy manager RM A. The other nodes on the Ethernet ring have been designated as ordinary switching nodes .

The Ethernet ring includes 5 transmitter units and 8 receiver units. These 5 transmitter units are located in the active nodes, RM A, NE2, NE3, NE4 and NE5, of the active link within the domain, respectively; the 8 receiving units are located in the Ethernet nodes within the domain RM A and NE1~NE7. The receiver units receive the multicast information sent by the transmitter units and update the multicast information tables of the Ethernet nodes within the domain according to said multicast information.

As the exemplary embodiment above shows, the method according to the invention is able to notify the protection link of the active link's multicast information before a failure occurs in an active link or after a failure occurs in an active link; if a link fails, the protection link is able to obtain the active link's multicast information within a short time and thereby take over operation

of the traffic package; moreover, the failover time in dynamic multicast services can be reduced from seconds to milliseconds, reducing the protection time. In addition, the method according to the invention is a supplement to the existing Ethernet ring protection protocol (ERP) which requires no alterations to existing equipment, and the cost of using the method according to the invention is therefore extremely low.