Multiple endpoint protection using SPVCs
A system and method are provided for a multi-endpoint SPVC, the multi-endpoint SPVC providing redundancy. A primary SPVC is established through a first source node. An intermate communication channel (ICC) is established between the first source node and a second source node. If the primary SPVC fails, the second source node learns of this via the ICC and establishes an alternate SPVC. If the first source node fails, the second source node learns of this failure without having to be explicitly told. The second source node learns of the failure of the first source node when poll messages are no longer received over the ICC as indicated by expiry of a timer. In such an event, the second source node attempts to establish an alternate SPVC. Finite state machines are provided on each source node to monitor the status of each other. Command messages, in the form of Generic Application Transport information elements, are provided by which the finite state machines can communicate over the ICC.
1. A method for providing redundancy for communications through a communication network, comprising:
establishing an Intermate Communication Channel (ICC) between a first source node and a second source node;
establishing a primary Soft Permanent Virtual Circuit (SPVC) network connection through the first source node to one of a list of possible destination nodes;
determining whether the second source node is to attempt establishment of an alternate network connection;
when the second source node is to attempt establishment of the alternate network connection, establishing the alternate network connection through the second source node to one of the list of possible destination nodes; and
using finite state machines (FSMs) residing on the first source node and the second source node to establish connections to at least one destination node, wherein each FSM operates in the following states:
down, as an initial state and when a connection between the source node on which the FSM resides and the destination node is down,
up, when a connection is established from the source node on which the FSM resides to the destination node,
attempting, when the source node on which the FSM resides is attempting to make a connection,
mate attempting, when a source node on which the FSM does not reside is attempting to make a connection, and
mate up, when a connection is established through the source node on which the FSM does not reside.
2. The method of claim 1 , where determining whether the second source node is to attempt establishment of an alternate network connection comprises:
determining whether the first source node cannot support the SPVC network connection;
when the first source node cannot support the SPVC network connection, determining that the second source node is to attempt establishment of the alternate network connection;
at the second source node, determining whether the ICC has failed; and
when the ICC has failed, determining that the second source node is to attempt establishment of the alternate network connection.
3. The method of claim 2 wherein determining whether the first source node cannot support the SPVC network connection comprises:
determining whether the primary SPVC network connection has failed;
when the primary SPVC network connection has failed, determining whether the first source node can re-establish the SPVC network connection; and
when the first source node cannot re-establish the SPVC network connection, determining that the first source node cannot support the SPVC network connection.
4. The method of claim 3 wherein determining whether the first source node can re-establish the SPVC network connection comprises:
attempting to establish the SPVC network connection to each possible destination node in turn until either a connection is established to at least one possible destination node or establishment of a connection to every possible destination node has been unsuccessfully attempted; and
determining that the first source node cannot re-establish the SPVC network connection if establishment of a connection to every possible destination node has been unsuccessfully attempted.
5. The method of claim 4 wherein determining whether the ICC has failed comprises:
operating an Intermate Connection Inactivity Timer on the second source node;
restarting the Intermate Connection Inactivity Timer when a command message is received at the second source node from the first source node; and
when the Intermate Connection Inactivity Timer expires, determining that the ICC has failed.
6. The method of claim 5 wherein establishing an ICC comprises
establishing a connection-oriented bearer independent connection.
7. The method of claim 6 ,
wherein each command message is a Generic Application Transport (GAT) information element which includes a Multi-endpoint (MEP) Action field indicating a type of the command message, and
wherein the type of the command message is one of:
a poll message,
a message indicating that the source node originating the command message is not supporting the SPVC network connection,
a message indicating that the source node originating the command message is supporting the SPVC network connection, and
a message indicating that the source node originating the command message is attempting to establish the SPVC network connection.
8. A node within a communication network, comprising:
a finite state machine (FSM) residing on a first source node and a second source node to establish connections to at least one destination node for storing a state of the node, wherein each FSM operates in the following five states:
down, as an initial state and when a connection between the source node on which the FSM resides and the destination node is down,
up, when a connection is established from the source node on which the FSM resides to the destination node,
attempting, when the source node on which the FSM resides is attempting to make a connection,
mate attempting, when a source node on which the FSM does not reside is attempting to make a connection, and
mate up, when a connection is established through a source node on which the FSM does not reside;
a memory for storing a data structure, the data structure including an indication of whether the source node is a first source node or a second source node and an indication of whether the FSM is a master FSM or a slave FSM;
means for establishing an Intermate Communication Channel (ICC) to a mate node in the event that the FSM is the master FSM;
means for determining whether the ICC is up;
means for establishing an SPVC network connection in the event that the node is a first source node;
means for establishing the SPVC network connection in the event that the node is an second source node and that the FSM indicates a down state; and
means for establishing the SPVC network connection in the event that the source node is the second source node and that the ICC is not up.
9. The node of claim 8 ,
wherein the data structure comprises an Intermate Connection Inactivity Timer, and
wherein the means for determining whether the ICC is up comprises:
means for restarting the Intermate Connection Inactivity Timer upon receipt of a command message over the ICC; and
means for determining that the ICC is not up upon expiry of the Intermate Connection Inactivity Timer.
10. The node of claim 9 further comprising:
means to set the FSM to the down state upon receipt of a command message indicating that the source node on which the FSM does not reside is not supporting the SPVC network connection.