Patent Application
20130176893
This invention generally relates to computer communication networks, and in particular to methods, apparatus, and systems for preventing loops within the network.
Computer communication networks, such as local area networks (LANs), typically have several bridges with multiple links interconnecting between the several bridges to carry data therebetween. The several bridges in the network may have various levels of connectivity in terms of both the number of pathways to a particular bridge, as well as, the number of other bridges a particular bridge is connected to. Each of the bridges can have multiple ports that can be used to establish a point-to-point link from the bridge to another bridge or an end terminal, such as a desktop computer. The ports of each of the bridges can be selectively activated or deactivated based upon whether a particular link is required in the network.
Often times there is also a hierarchy associated with the several bridges in the network, where each of the bridges may have various levels of priority within the network. For example, the bridge with the highest level of priority may be designated a root bridge and the network may be required to establish a communicative pathway from each of the several bridges to the root bridge.
Therefore, when a network is set up or a new node or new bridge is added to an existing network, each bridge must first determine which bridge is the root bridge and then establish a pathway to communicate with the root bridge, as well as, other predetermined bridges of the network. Rapid spanning tree protocol (RSTP), standardized as Institute of Electrical and Electronic Engineers (IEEE) standard 802.1D, is currently used to establish a pathway for each of the bridges of the network to be able to communicate with the root bridge. The RSTP may first establish a root bridge, determine least cost paths to the root bridge from each of the other bridges, and disable all other paths, other than the least cost path to the root bridge from each of the bridges. This process may entail sending a message from the root bridge to another bridge and then having the root bridge establish a link between the two bridges by selectively placing ports along the link in a forwarding state. Therefore, unidirectional messaging is performed in the process of the root bridge placing ports in a forwarding state.
There is a possibility that during changes in the network, such as if one or more ports temporarily cease to function, such as due to hardware failure including port transceiver failure, or if new nodes are added or removed from the network, then a loop may occur in the network. A loop occurs when there is more than one active path between any two communicating bridges and can lead to network instability by providing the possibility of a broadcast storm, or an excessive amount of broadcast data. A bridge can rebroadcast a broadcast message repeatedly when a loop exists in the network, potentially overwhelming the network's capability in handling a large number of messages.
Certain embodiments of the invention can provide systems, methods, and apparatus for loop containment enhancement in a communication network. Certain embodiments of the invention can include providing a communication network free of loops. Certain embodiments of the invention can include loop free connections between two or more bridges in a network.
In one embodiment, a method can include providing a first bridge with at least one port, and providing a second bridge with at least one port and transmitting a first message from one of a first port on the first bridge selected from the at least one port of the first bridge and a second port on the second bridge selected from the at least one port of the second bridge. The method can further include transmitting a second message from the other of the first port and the second port and establishing a connection between the first bridge and the second bridge via the first port and the second port if both the first and the second message were received by one of the first and second bridge.
In another embodiment, a communication bridge can include at least one port, one or more paths, each path connected to one or more of the at least one ports, and a bridge controller controlling a state of each of the at least one ports, wherein a message is received at one of the at least one port via the corresponding path and a second message is transmitted by the communication bridge on the same one of the at least one port upon receiving the message.
In yet another embodiment, a system can include a root bridge having at least one port, a second bridge having at least one port and a second bridge controller for controlling the state of the at least one port of the second bridge, and at least one path between the root bridge and the second bridge, each path corresponding to one of the at least one port of the second bridge. Furthermore, one path selected from the at least one path can be established as a communicative pathway between the root bridge and the second bridge by sending a first and second message between the root bridge and the second bridge and the second bridge controller placing the port corresponding to the communicative pathway in a forwarding state if the first and second messages were received.
Other embodiments, features, and aspects of the invention are described in detail herein and are considered a part of the claimed inventions. Other embodiments, features, and aspects can be understood with reference to the following detailed description, accompanying drawings, and claims.
Reference will now be made to the accompanying tables and drawings, which are not necessarily drawn to scale, and wherein:
Embodiments of the invention are described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.
Embodiments of the invention may provide apparatus, systems, and methods for loop containment enhancement in a communication network. In certain embodiments, a more robust communications network that has greater immunity from broadcast storm failures can be implemented. Such improvements may entail providing communications networks that are free from loops. In one aspect, a loop-free network may be established by sending messages from a bridge to another bridge via a port and then monitoring the port for a return message and upon receiving a return message, establishing the port for communicating between the two bridges. Further improvements may include a more robust reconfiguration of a communication network if a hardware failure is experienced. Preventing loops in the communication network may be implemented by requiring two messages to be transmitted when establishing a connection from one port on one bridge to another port on another bridge. Establishing a communicative link, therefore, between two bridges may involve bi-directional messaging and may require the receipt of a confirmation message before establishing a communicative link.
Example embodiments of the invention will now be described with reference to the accompanying figures.
Referring now to
It should be noted that each bridge may have multiple ports, such as, for example, 24 ports, 48 ports, or 96 ports. As illustrated, only a subset of, for instance, P1, P2, P3, P4, P5, P6, P7, P8, P9, P10, of the total number of ports of a bridge, such as Bridge A, Bridge B, Bridge C, and Bridge D, may be used to establish a communicative link, such as Segment 1, Segment 2, Segment 3, Segment 4, and Segment 5. For example, Bridge A is illustrated as using only two of its ports P1 and P2 to establish communicative link Segment 1 with Bridge B and Segment 2 with Bridge C.
Each of the ports P1, P2, P3, P4, P5, P6, P7, P8, P9, P10 can be in one of at least four states: (i) listening; (ii) learning; (iii) forwarding; and (iv) blocking. For a segment to be active, or capable of transmitting messages, the two ports associated with that segment must be in a forwarding state. For example, for Segment 1 to be active as a communicative link, both ports P1 and P3 must be in a forwarding state.
Continuing on with
The process of establishing a root bridge and setting states for each of the ports P1, P2, P3, P4, P5, P6, P7, P8, P9, P10 to establish root ports and links Segment 1, Segment 2, Segment 3, Segment 4, and Segment 5 from each of the bridges to the root bridge may require communication between the bridges Bridge A, Bridge B, Bridge C, and Bridge D. A bridge protocol data unit (BDPU) may be used to establish communication with and between the bridges Bridge A, Bridge B, Bridge C, and Bridge D. There may be various types of BDPUs, such as configuration BPDU, topology change notification BDPU, topology change notification acknowledgement BDPU, and the like.
The formation of network loops in a network will be explained by way of example by still referring to
Referring now to
In one embodiment, the type 2 BDPU sent from Bridge A to Bridge D is a routed message and is not a broadcast message. In other words, the type 2 BDPU message may be sent by Bridge A and transmitted only on port P1 of Bridge A and then forwarded only on port P5 of Bridge B to Bridge D. To further clarify, the type 2 BDPU between Bridge A and Bridge D may not have been transmitted on port P2 of Bridge A and port P4 of Bridge B, when trying to establish a potential communicative pathway to the root bridge via links Segment 1 and Segment 3.
The type 2 BDPU can be a data packet that includes several data fields including, but not limited to, address of the root bridge, priority of the root bridge, address of the bridge to be linked to the root bridge, and priority of the bridge to be linked to the root bridge. The type 2 BDPU may not have a payload.
Once the message in the form of the type 2 BDPU is received by Bridge D from the root bridge Bridge A, Bridge D may extract information from the type 2 BDPU and then respond with a confirmation type 2 BDPU message, or a second message, over a reciprocal path as depicted by arrows 106 and 108. If the root bridge Bridge A receives the confirmation type 2 BDPU, then the root bridge Bridge A may establish a communicative link between Bridge D and itself by placing ports P1, P3, P5, and P9 in a forwarding state to provide a communicative pathway using links Segment 1 and Segment 3. The data fields of the type 2 BDPU of the confirmation message from Bridge D to Bridge A may be similar to the first communicative type 2 BDPU from Bridge A to Bridge D.
Referring now to
Still referring to
In the example discussed above in conjunction with
In one embodiment, the lowest cost path may be selected by the root bridge to establish a potential communicative link between itself and another bridge. In other words, considering the above example, the root bridge A may have determined that the communicative pathway comprising Segment 1, Segment 3 and ports P1, P3, P5 and P9 are lower cost than alternative communicative pathways between Bridge A and Bridge D, such as via Segment 1, Segment 4, Segment 5 and ports P1, P3, P4, P7, P8, and P10. Cost determination of a communicative pathways may consider elements including, but not limited to, the latency of pathways, the bandwidth of the pathways, the energy consumption per bit on pathways, processing bandwidth required of the root bridge using each pathway, or combinations thereof.
In other embodiments of the invention, the choice of establishing a pathway by the root bridge may consider an overall cost for the network as a whole rather than on a link by link basis. In other words, a root bridge may establish a pathway to a bridge that is not the lowest cost path to that bridge if holistically the communicative pathway cost of the network is reduced or minimized. Such holistic cost determination may involve statistical analysis of historical data, neural network analysis, Monte Carlo analysis, or the like.
Although the process of establishing a communicative pathway between the root bridge and another bridge is depicted as the root bridge sending the first communicative message, it is not necessary for the root bridge to send the first communicative message according to an embodiment of the invention. In fact, the first communicative message can be sent from the bridge that needs to establish a connective pathway to the root bridge. Following that, the root bridge may provide the confirmation message and a communicative pathway may be established by placing the appropriate ports of the network in a forwarding state.
It should be noted, that the network topologies of the network 100 may be modified in various ways in accordance with certain embodiments of the invention. For example, in certain embodiments, one or more nodes may be placed and interconnected at a different location relative to the other nodes on the network 100. Additionally, in other embodiments, other nodes can be added or removed from the network 100.
Referring now to
It should be noted, that the method 120 may be modified in various ways in accordance with certain embodiments of the invention. For example, one or more operations of method 120 may be eliminated or executed out of order in other embodiments of the invention. Additionally, other operations may be added to method 120 in accordance with other embodiments of the invention.
While certain embodiments of the invention have been described in connection with what is presently considered to be the most practical and various embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
This written description uses examples to disclose certain embodiments of the invention, including the best mode, and to enable any person skilled in the art to practice certain embodiments of the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of certain embodiments of the invention is defined in the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
