Unable to contact a KDC for the source domain in it's own site. This means either there are no available KDC's for this domain ...

[%1] Unable to contact a KDC for the source domain in it's own site.  This means either there are no available KDC's for this domain in the site, *including* the source DC itself, or we're having network or packet fragmentation issues connecting to it.  We'll check packet fragmentation connection to the source DC, make recommendations, and continue.