Not any separate test solution can be used to monitor networks during this migration to SDN networks. These environments require test instruments that support Forward Error Correction (FEC) performance tests using Poisson distribution random errors. Adopted by ITU-T O.182, these tests are important because the FEC section is one of the most vital areas of the network frame. It allows for greater dB range between equipment by correcting errors within the frame at the receiver end.

Reproducible, accurate FEC error correction tests are performed by generating truly random signal errors that can stress OTN FEC. This allows for a much lower BERT measurement to ensure testing to the limit or beyond the switching equipment’s ability. This is necessary to accurately measure the actual performance and threshold of an OTN.

Network Monitoring

To maintain network performance and efficiently troubleshoot issues, test solutions need to support Section Monitoring (SM) and Path Monitoring (PM) of an OTN, each of which has different alarms and error detection. These maintenance signals send feedback on issues that occur at the network far end and offer an indication of the layer in which it occurred. Among the indications are:

• Backward Defect Indication (BDI) - indicates signal fail in the upstream;
• Backward Error Indication (BEI) - indicates the number of errors detected in the upstream;
• Incoming Alignment Error (IAE) - detects error by BIP-8 code in the OTU layer; and
• Backward Incoming Alignment Error (BIAE) - counts the IAE errors in the upstream in the OTU.

Network engineers and technicians use these OTN maintenance signals to quickly and correctly locate an issue, so they know the position in the network where testing should begin. It also allows issues to be prioritized. For example, Layer SM will have a higher priority because it is likely a core issue, whereas a PM problem is most likely a single customer issue.

Taking this Tandem Connection Monitoring (TCM) approach makes it easy to identify the customer or segment level affected. With this information, operators can ensure that issues affecting high-priority customers are corrected first. Additionally, understanding the various TCM levels that are being analyzed or injecting errors identifies the actual section where there is a problem.

SDNs are evolving so that networks can effectively and efficiently meet ever-growing bandwidth needs. The transition from traditional network environments to SDN is a careful process that poses many challenges to operators who must maintain high QoS and customer retention. The most effective way to ensure that this move will be done seamlessly is to use separate test solutions with a “golden” reference rather than integrating test software into the SDN.