RDC confirmed there is no packet loss, no errors of any sort found on RDC link.
The slow login issue is more likely a desktop or authentication server issue. Closing ticket for now.
RDC login situation improved after the restoration of the Winnipeg - Calgary link. However, the fiber cut on this link is not supposed to affect the RDC login. We are still investigating the root cause of the issue.
RDC reported that a number of centers across the country from Ontario to British Columbia have been reporting instability in their network connectivity since yesterday afternoon, with the effect that researchers are only intermittently able to log in. The start time of the issue seems to align with the fiber break between Winnipeg and Calgary, however, the traffic is re-rerouted and the status of RDC-related Layer 2 services looks fine. We are investigating.