Router switch fabric protection using forward error correction
View Patent ↗Instead of alternatively utilizing only one fabric or the other fabric of a redundant pair, both fabrics simultaneously transmit duplicate information, such that each packet forwarding module (PFM) receives the output of both fabrics simultaneously. In real time, an internal optics module (IOM) analyzes each information chunk coming out of a working zero switch fabric; simultaneously examines a parallel output of a working one duplicate switch fabric; and compares on a chunk-by-chunk basis the validity of each and every chunk from both switch fabrics. The IOM does this by examining forward error correction (FEC) check symbols encapsulated into each chunk. FEC check symbols allow correcting a predetermined number of bit errors within a chunk. If the chunk cannot be corrected, then the IOM provides indication to all PFMs downstream that the chunk is defective. Under such conditions, the PFMs select a chunk from the non-defective switch fabric. Under error-free normal conditions, however, the PFMs select a chunk arbitrarily from a default switch fabric. In this way, each chunk in real time is selected from a non-defective source and is thus guaranteed to be error free. Accordingly, if a switch fabric fails, no information chunks are lost anywhere in the system.
1. A method comprising:
launching an aggregation packet from a first module within a switch fabric, wherein the aggregation packet includes a plurality of Internet Protocol (IP) packets and indicates an ingress address assigned to an ingress module and an egress address assigned to an egress module;
receiving said aggregation packet at a second module within the switch fabric;
comparing the ingress address with the address of the first module;
comparing the egress address with the address of the second module;
responsive to the ingress address not being consistent with the address of the first module or the egress address not being consistent with the address of the second module, determining a data path through the switch fabric to be faulty; and
launching a duplicate copy of the aggregation packet from a protection module corresponding to the first module.
2. The method of claim 1 , further comprising receiving a duplicate copy of the aggregation packet at a protection module corresponding to the second module.
3. The method of claim 1 , further comprising diverting aggregation packets to be launched via the first module to a protection module, thereby allowing the first module to be replaced.
4. The method of claim 1 , further comprising performing error correction and detection.
5. The method of claim 4 wherein said error correction and detection is forward error correction.
6. The method of claim 1 , further comprising reframing the aggregation packet prior to the aggregation packet entering the switch fabric.
7. The method of claim 1 wherein said data path comprises an optical fiber cable.
8. The method of claim 1 wherein said aggregation packet is a substantially fixed size diagnostic chunk.
9. The method of claim 1 wherein said switch fabric, said first module, and said second module are incorporated within a router system.
10. A system, comprising:
a first module comprising hardware and within a switch fabric, the first module configured to launch an aggregation packet, wherein the aggregation packet includes a plurality of IP packets and indicates an ingress address assigned to an ingress module and an egress address assigned to an egress module;
a second module within the switch fabric to receive said aggregation packet;
a comparison mechanism within the switch fabric and configured to:
compare the ingress address with the address of the first module;
compare the egress address with the address of the second module; and
a fault detection mechanism configured to determine a data path through the switch fabric to be faulty responsive to the ingress address not being consistent with the address of the first module or the egress address not being consistent with the address of the second module; and
a protection module corresponding to the first module, the protection module configured to launch a duplicate copy of the aggregation packet.
11. The system of claim 10 , further comprising a protection module corresponding to the second module, the protection module configured to receive a duplicate copy of the aggregation packet.
12. The system of claim 10 , further comprising an error correction and detection mechanism configured to perform error correction or detection or both.
13. The system of claim 12 , wherein said error correction is forward error correction.
14. The system of claim 10 , further comprising a protection mechanism configured to divert aggregation packets to be launched via the first module to a protection module, thereby allowing the first module to be replaced.
15. The switch of claim 10 , wherein said data path comprises an optical fiber cable.
16. The switch of claim 10 , wherein said aggregation packet is a substantially fixed size diagnostic chunk.
17. The switch of claim 10 , wherein said switch fabric, said first module, and said second module are incorporated within a router system.