We've identified a connectivity issue to certain carrier endpoints that affected outbound calls between 13:21 and 13:37, but should now be resolved as the offending endpoints have been removed from routing. A small number of inbound calls were also affected between 13:21 and 13:41, but this should now be resolved as well. We are currently investigating the issue with the carrier in question and will provide further updates as soon as we have them.
UPDATE: Our preliminary investigations indicate a one-way packet loss issue, so we are currently trying to establish whether this occurred on the carrier side or at the IP transit level on the routes to those particular endpoints.
UPDATE: We now believe that the issue occurred at the IP transit level with a third-party ISP.