In Ethernet network architectures, devices connected to the network compete for the ability to use shared telecommunications paths at any given time. Where multiple bridges or nodes are used to interconnect network segments, multiple potential paths to the same destination often exist. The benefit of this architecture is that it provides path redundancy between bridges and permits capacity to be added to the network in the form of additional links. However to prevent loops from being formed, a spanning tree was generally used to restrict the manner in which traffic was broadcast on the network. Since routes were learned by broadcasting a frame and waiting for a response, and since both the request and response would follow the spanning tree, most if not all of the traffic would follow the links that were part of the spanning tree. This often led to over-utilization of the links that were on the spanning tree and non-utilization of the links that weren't part of the spanning tree.
To overcome some of the limitations inherent in Ethernet networks, a link state protocol controlled Ethernet network was disclosed in U.S. patent application Ser. No. 11/537,775, filed Oct. 2, 2006, entitled “Provider Link State Bridging,” the content of which is hereby incorporated herein by reference. As described in greater detail in that application, the nodes in a link state protocol controlled Ethernet network exchange link state advertisements to build a synchronized view of the network topology, which is stored in a link state database. The link state database may then be used to compute shortest paths through the network. The link state advertisements may be used to distribute link state updates to all other nodes in a particular network level.
In addition to building a network topology database, each node also populates a Forwarding Information Base (FIB) which will be used by the node to make forwarding decisions so that frames will be forwarded over the computed shortest path to the destination. Since the shortest path to a particular destination is always used, the network traffic will be distributed across a larger number of links and follow a more optimal path for a larger number of nodes than where a single Spanning Tree or even multiple spanning trees are used to carry traffic on the network.
When customer traffic enters a provider network, the customer MAC Destination Address (C-MAC DA) is resolved to a provider MAC Destination Address (B-MAC DA), so that the provider may forward traffic on the provider network using the provider MAC address space. Additionally, the network elements on the provider network are configured to forward traffic based on Virtual LAN ID (VID) so that different frames addressed to the same destination address but having different VIDs may be forwarded over different paths through the network. In operation, a link state protocol controlled Ethernet network may associate one VID range with shortest path forwarding, such that unicast and multicast traffic may be forwarded using a VID from that range, and traffic engineering paths may be created across the network on paths other than the shortest path, and forwarded using a second VID range. The use of Traffic Engineered (TE) paths through a link state protocol controlled Ethernet network is described in greater detail in U.S. patent application Ser. No. 11/732,381, filed Apr. 3, 2007, entitled “Engineered Paths In A Link State Protocol Controlled Ethernet Network”, the content of which is hereby incorporated herein by reference.
The Institute of Electrical and Electronics Engineers (IEEE) has developed a draft standard 802.1Qay which is commonly referred to as Provider Backbone Bridging-Traffic Engineering (PBB-TE). Conventionally, when a PBB-TE network is to be used to transport IP traffic, a connection would be set up across the PBB-TE network. One way to set up a connection across a PBB-TE network is described in U.S. patent application Ser. No. 11/580,796, filed Apr. 19, 2007, entitled “GMPLS control of Ethernet” the content of which is hereby incorporated herein by reference.
As described in greater detail in this application, when a connection is to be established across a PBB-TE network, the connection will be computed by a head-end node or central management system, and then a connection set up message will be transmitted across the PBB-TE network. For example, assume that Node A was asked to establish a connection to node E. Node A would perform a path computation process to figure out a path to E which, for purposes of this example will be assumed to include intermediate nodes B, C, and D.
Node A will then create a RSVP-TE path setup message containing information about the path through the network and send the path setup message to node B. Node B will process the message and pass it to node C. The message will continue until it reaches its destination (node E).
When node E receives the path setup message, it will generate a RSVP-TE resv response message which will follow the reverse path through the network. As part of this RSVP-TE signaling, the nodes on the path reserve resources and install forwarding state to allow traffic to be forwarded along the path.
In U.S. patent application Ser. No. 11/525,594, filed Mar. 22, 2006, entitled Method and Apparatus For Establishing Forwarding State Using Path State Advertisements, a proposal was made to use the link state protocol control packets to carry this connection information on the network rather than using a separate signaling protocol. In this application, the head-end node would calculate a path through the network using network topology information in its topology database. Rather than signaling these connections on the network using RSVP-TE, however, the link state protocol such as ISIS was extended to carry the connection information in particular its path through the network. In this scenario, the head-end node calculates a route and floods the route throughout the network. All nodes on the network store the connection in their connection database. Nodes on the connection's route install forwarding state for the connection to thereby allow the connection to be created on the PBB-TE network. The content of application Ser. No. 11/525,594 is hereby incorporated herein by reference.
A PBB-TE network may include many connections, each of which is carried on a traffic engineered path that is signaled on the network. When a failure occurs on the network, the head-end nodes for those connections affected by the failure will re-compute new routes for the connections and flood the new routes in link state advertisements. The head-end nodes will compute these routes given the new network topology and the constraints associated with the routes such as required bandwidth, desired end node, and relative priority of the connection. Since there are many different head-end nodes that may be affected by a given failure on the network, and each head-end node is responsible for computing a new set of routes for its affected connections, it is possible for clashes to occur in which two different head-end nodes both try to reserve resources for restoration paths for different connections over a given node/link. Additionally, while each of the nodes may prioritize its own connections, coordinating priority of connections established by different nodes on the network remains a challenge. Accordingly, it would be advantageous to provide a new way for connections to be re-established after the occurrence of a failure on the network.
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