Network system supporting spanning tree protocol, relay apparatus thereof, and method of creating spanning tree topology thereof

Provided are a network system supporting a spanning tree protocol (STP), a relay apparatus thereof, and a method of creating a spanning tree. Proposed is a method of creating a tree topology, between AVB bridges, using a STP message including a group MAC address which is different from that used in a non-AVB (Audio Video Bridging) bridge (that is, a bridge without the function of AVB), in order to form a minimum number of AVB clouds. Therefore, it is possible to efficiently ensure transmission quality of a multimedia stream such as an AVB stream.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from Korean Patent Application No. 10-2007-0107445, filed on Oct. 24, 2007, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a network system, and more particularly, to a network system supporting a spanning tree protocol, a relay apparatus thereof, and a method of creating a spanning tree.

2. Description of the Related Art

An example of a network system for transmitting data between a plurality of different terminals is an Ethernet. The Ethernet utilizes a bridge or gateway as a relay apparatus for extending a network. That is, the Ethernet includes a plurality of Local Area Networks (LANs) that are connected respectively to a plurality of terminals, and a plurality of bridges which connect the LANs to one another. A message that is transmitted between the bridges can be bridged from one LAN to another LAN, for example, according to the IEEE802.ID standard which defines Media Access Control (MAC) bridging.

In such a network system which is connected by bridges, if multiple paths exist between the bridges, a loop is formed and thus a traffic looping problem occurs, in which a message sent from a bridge is circulated around the loop. In principle, only one single path has to exist between two bridges. For this reason, each bridge supports a spanning tree algorithm for executing a spanning tree protocol (referred to as a STP) based on the IEEE802.1D standard, which is used to avoid the above-mentioned traffic looping problem.

Meanwhile, it is known that the Ethernet is not suitable for transmitting multimedia data sensitive to a delay in transmission time, but recently a technique for transmitting multimedia data such as images or sounds via existing Ethernet are actively being developed. Such a technique, which is called Audio Video Bridging (AVB), is being standardized by the IEEE802.1.

According to the current consensus of the AVB standardization committee, since Quality of Service (QoS) of AVB protocols 0.1AS, 1Qat, and 0.1Qav is ensured only within an AVB cloud, all bridges should be AVB bridges in order to ensure QoS.

Here, Non-AVB bridges or AVB bridges can construct a tree topology from which redundant routes are removed by applying a spanning tree protocol thereto. The tree topology includes one or several AVB clouds which are connected via non-AVB bridges. However, the tree topology has a problem in that a network range capable of ensuring transmission quality of an AVB stream is limited to within an AVB cloud. In particular, as the number of AVB clouds included in the tree topology increases, it becomes more difficult to ensure transmission quality of a multimedia stream.

SUMMARY OF THE INVENTION

The present invention provides a network system supporting a spanning tree protocol which can efficiently provide high transmission quality for a multimedia stream, a relay apparatus thereof, and a method of creating a spanning tree.

The present invention further provides a network system for supporting a spanning tree protocol for ensuring high transmission quality of a multimedia stream, a relay apparatus thereof, and a method of creating a spanning tree, which take into consideration a fact that networks having the same physical configuration can have different numbers of AVB clouds depending on a root node when a spanning tree protocol is applied to remove redundant routes, and a network range capable of ensuring transmission quality of a multimedia stream is widened as the number of possible AVB clouds decreases.

According to an aspect of the present invention, there is provided a network system supporting a spanning protocol (STP) including: at least one AVB bridge using a group MAC address of an extra area which is assigned to exchange a STP message between AVB clouds in the network system; and at least one non-AVB bridge using a group MAC address of a normal area which is assigned to exchange a STP message between non-AVB bridges in the network system.

The AVB bridge creates a spanning tree using a STP message including the group MAC address of the extra area, thereby minimizing the number of AVB clouds in the network system.

If the AVB bridge receives a STP message including the group MAC address of the normal area, the AVB bridge forwards the STP message to a non-AVB port outside a boundary of an AVB cloud.

According to another aspect of the present invention, there is provided a relay apparatus of a network supporting a spanning tree protocol (STP), the relay apparatus including: at least two ports; a receiver receiving a message for setting up a network path from a port of the at least two ports; a message controller transferring the received message to a predetermined STP processor if the received message supports an Audio Video Bridging (AVB) protocol, or forwarding the received message to another activated port without passing the received message through the predetermined STP processor if the received message does not support the AVB protocol; and a STP processor creating a spanning tree from which a repeated route is removed, on the basis of the message received from the message controller.

The STP processor creates the spanning tree using the received message if the received message supports the AVB protocol, thereby minimizing the number of AVB clouds in the network.

The message processor determines whether the received message supports the AVB protocol, on the basis of a group MAC address included in the received message.

According to another aspect of the present invention, there is provided˜claim12.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

A general spanning tree creating method is carried out by selecting an Audio Video Bridging (AVB) bridge as a root node, and setting the cost of each port so that connecting two AVB ports to each other is more selected than connecting an AVB port to a non-AVB port or connecting two non-AVB ports to each other. A spanning tree algorithm for this is very simple, and is disadvantageous in that path settings depend on a root node and in some cases, optimal results may not be obtained.

FIGS. 1A,1B, and1C show examples in which network paths are set up using a conventional spanning tree creating method.

FIG. 1Ashows an example of a network configuration which includes AVB bridges and non-AVB bridges and supports a spanning tree protocol. In the network configuration illustrated inFIG. 1A, the AVB and non-AVB bridges are physically connected to one another.

FIG. 1Bshows an example of a network configuration when a general spanning algorithm is applied to the network configuration illustrated inFIG. 1in a case where the upper, right bridge of the bridges is set as a root node. In the network configuration illustrated inFIG. 1B, a repeated route is removed and two AVB clouds are formed and connected to each other via non-AVB bridges.

FIG. 1Cshows an example of a network configuration when a general spanning algorithm is applied to the network configuration illustrated inFIG. 1Ain a case where the upper, central bridge of the bridges is set to a root node. In the network configuration illustrated inFIG. 1C, a repeated route is removed and three AVB clouds are formed and connected to one another via non-AVB bridges.

That is, existing spanning tree protocols (for example, a spanning tree protocol (STP), a rapid spanning tree protocol (RSTP), or a multiple spanning tree protocol (MSTP) based on the IEEE 802.1 standard) create a tree topology which includes one or more AVB clouds connected via non-AVB bridges depending on a root node. Here, since no AVB stream can escape from an AVB cloud, the coverage of an AVB stream on the network is limited.

Accordingly, a network setting method is needed which can create a tree structure having a minimum number of AVB clouds. The present invention proposes a method of creating a tree having a minimum number of AVB clouds in a network supporting an AVB apparatus and a non-AVB apparatus on the basis of an existing spanning tree protocol.

Hereinafter, a bridge which is a relay apparatus for extending a network according to an embodiment of the present invention will be described. However, the relay apparatus according to the embodiment of the present invention is not limited to a bridge, and may include various network relay apparatuses such as a gateway.

FIG. 2is a view for explaining a network system supporting a spanning tree protocol, according to an embodiment of the present invention.

Referring toFIG. 2, a basic concept of a network system supporting a spanning tree protocol, according to an embodiment of the present invention, is to use an extra STP message100which is transmitted between AVB bridges connected to each other and which is different from that used between non-AVB bridges, in order to form the maximum size of an AVB cloud.

InFIG. 2, information for setting up a network path is received and transmitted through a STP message100having an address of an extra area which is assigned for an AVB protocol, between AVB bridges which are connected to each other. A STP message200having an address of a normal area is forwarded to a non-AVB port outside the boundary of an AVB cloud, without being used to create a spanning tree for setting up the network path.

In detail, AVB bridges use a group MAC address of an extra area which is assigned to exchange a STP message between AVB clouds. However, if non-AVB bridges receive a STP message100having the group MAC address of the extra area, the non-AVB bridges will ignore the STP message100because they cannot interpret the STP message100.

Meanwhile, the non-AVB bridges use a group MAC address of a normal area in order to exchange a STP message between all non-AVB bridges in the network. However, if AVB bridges receive a STP message200having the group MAC address of the normal area, the AVB bridges forward the STP message200to a port outside the boundary of an AVB cloud, without using the STP message200to create a spanning tree for setting up a network path. Accordingly, since a non-AVB cloud cannot obtain information about AVB bridges forming an AVB cloud, the non-AVB cloud will consider an AVB cloud as a transparent LAN.

In summary, the network system supporting a spanning tree protocol, according to the embodiment of the present invention, includes at least one AVB bridge using a group MAC address of an extra area which is assigned to exchange a STP message between AVB clouds in a network system, and at least one non-AVB bridge using a group MAC address of a normal area in order to exchange a STP message between non-AVB bridges in the network system. Here, the STP message may be a bridge packet data unit (hereinafter, simply referred to as “BPDU”) including information for setting up a network path.

Here, the AVB bridges can minimize the number of AVB clouds in the network by creating a spanning tree using a STP message including the group MAC address of the extra area. Also, if an AVB bridge receives a STP message including the group MAC address of the normal area, the AVB bridge forwards the STP message to a non-AVB port outside the boundary of an AVB cloud.

Meanwhile, if a non-AVB bridge (a legacy bridge) receives a STP message using the group MAC address of the extra area, the non-AVB bridge ignores or discards the STP message. That is, since a non-AVB cloud cannot obtain information about AVB bridges forming an AVB cloud, the non-AVB cloud considers an AVB cloud as a transparent LAN. The non-AVB bridge creates a spanning tree using the STP message including the group MAC address of the normal area.

Here, the STP message includes a group MAC address. A group MAC address of a normal area may be an address defined in the first row of Table 1. A group MAC address of an extra area which is assigned for the AVB protocol according to the embodiment of the present invention may be an address defined in one of the reserved areas for future standardization of Table 1.

Meanwhile,FIG. 3is a block diagram of a network relay apparatus according to an embodiment of the present invention.

Referring toFIG. 3, the network relay apparatus supporting a spanning tree protocol, for example an AVB bridge illustrated inFIG. 2, includes at least two ports40, a message receiver10, a message processor20, and a STP processor30.

The at least two ports40are connected to different networks, and function to connect the networks to each other or to block the networks from each other.

The message receiver10receives a message for setting up a network path from each port40. The message received through the message receiver10may be a bridge packet data unit (BPDU) including information for setting up a network path. If it is determined that the message received through the message receiver10supports an AVB protocol, the message processor20transfers the received message to the STP processor30. If it is determined that the received message does not support an AVB protocol, the message processor20forwards the received message to another activated port without passing it through the STP processor30.

The message processor20may determine whether the received message supports an AVB protocol, on the basis of a group MAC address included in the received massage. That is, if it is determined that a group MAC address included in the received message is a group MAC address of an extra area which is assigned for an AVB protocol, the message processor20transfers the received message to the STP processor30, and if it is determined that the group MAC address included in the received message is a group MAC address of a normal area, the message processor20forwards the received message to another activated port without passing it through the STP processor30.

The STP processor30creates a spanning tree from which repeated routes are removed, using the message transferred through the message processor20. By creating a spanning tree using a message which supports an AVB protocol, instead of creating a spanning tree for all received messages, the number of AVB clouds in the network can be minimized. That is, in the network relay apparatus supporting the AVB protocol, a spanning tree algorithm is applied to networks only using a BPDU message supporting an AVB protocol, so that the maximum size of an AVB cloud can be achieved and thus a spanning tree topology having a minimum number of AVB clouds can be created.

FIG. 4is a flowchart of a spanning tree creating method according to an embodiment of the present invention, which is performed by the network relay apparatus according to an embodiment illustrated inFIG. 3.

Referring toFIG. 4, in order to create a spanning tree in the network supporting a spanning tree protocol, according to the embodiment of the present invention, first, a message for setting up a network path from one of at least two ports is received (operation S800), and it is determined whether the received message supports an AVB protocol, on the basis of a group MAC address included in the received message (operation S810). Here, the received message may be a bridge packet data unit (BPDU) including information for setting up a network path.

If the received message does not support an AVB protocol, the received message is forwarded to another activated port (S820). That is, if the group MAC address included in the received message is a group MAC address of a normal group, the received message is forwarded to another activated port, without creating a spanning tree.

If the received message supports an AVB protocol, a spanning tree from which repeated routes are removed is created using the received message (operation S830). That is, if a group MAC address included in the received message is a group MAC address of an extra area which is assigned for an AVB protocol, a spanning tree is generated using the received message. Accordingly, by creating a spanning tree using a message which supports an AVB protocol, the number of AVB clouds in the network can be minimized.

A network system supporting a spanning tree protocol having a minimum number of AVB clouds, a relay apparatus thereof, and a method of creating a spanning tree, according to embodiments of the present invention, have been described above.

FIGS. 5A,5B, and5C show examples in which network paths are set up using a spanning tree creating method according to an embodiment of the present invention.

FIG. 5Ashows a network system having the same physical configuration as that illustrated inFIG. 1A. When the spanning tree creating method according to this embodiment of the present invention is applied to the network system illustrated inFIG. 5A, network paths illustrated inFIGS. 5B and 5Ccan be obtained. By exchanging information through a STP message including a group MAC address of an extra area which is assigned to AVB bridges, network settings having a minimum number of AVB clouds are possible.

FIGS. 6A through 6Dshow other examples in which network paths are set up using a spanning tree creating method according to an embodiment of the present invention.

FIG. 6Ashows an example of a physical network configuration. As illustrated inFIG. 6B, when a general spanning tree creating method is applied to the network configuration illustrated inFIG. 6A, 6 AVB clouds can be created in the worst case.

However, when the spanning tree creating method according to this embodiment of the present invention is applied to the network configuration illustrated inFIG. 6A, network paths having a minimum number of AVB clouds can be obtained as illustrated inFIGS. 6C and 6D.

According to an embodiment of the present invention, in a network supporting an AVB apparatus and a non-AVB apparatus on the basis of an existing spanning tree protocol (STP, RSTP, and MSTP), a method for creating a tree topology having a minimum number of AVB clouds can be provided. Accordingly, it is possible to efficiently provide high transmission quality for a multimedia stream such as an AVB stream.

Heretofore, a method of creating a tree having a minimum number of AVB clouds in a network system having AVB bridges and non-AVB bridges has been described. However, the method can be generalized to a method of creating a tree having a minimum number of X-clouds for a specific X technique.

As described above, according to an aspect of the present invention, there are provided a network system which can efficiently provide high transmission quality for a multimedia stream by minimizing the number of AVB clouds to enlarge the coverage of an AVB cloud which ensures the transmission quality, a relay apparatus thereof, and a method of creating a spanning tree.