Latency Based Bidirectional Path Optimization

Bidirectional path computation ensures that two paths are computed for both traffic flow directions, providing symmetry and consistency. This is beneficial for services requiring matched paths in both directions, such as real-time communication or applications with strict quality requirements. The internet draft "draft-ietf-pce-sr-bidir-path" defines a PCEP extension to group two unidirectional paths into a single associated bidirectional SR Path. Currently, there has been a noticeable lack of implementation for this draft. So, the only way to use strict bidirectionality as a path computation constraint is to use path-profiles overrides in the Nokia NSP PCE. This path profile is applied after LSPs have been reported and delegated to the PCE.
The test procedure includes: 

• Establish PCEP sessions between the PCE and the PCC
• Compute and delegate a path on the PCCs to the PCE
• Create a path profile in the PCE and include both LSPs in it
  For additional verification, we configured the profile with a strict symmetric and applied latency as a constraint. After that, we increased the latency on a link and only in one direction. We observed the PCE optimizing both directions to another link, avoiding the high latency and preserving the symmetrically.