My Directory Service log is full of the following warning;
what does this mean?

The attempt to establish a replication link for the
following writable directory partition failed.

Directory partition:
DC=DOMAIN,DC=LOCAL
Source domain controller:
CN=NTDS Settings,CN=Server02,CN=Servers,CN=Default-First-
Site-Name,CN=Sites,CN=Configuration,DC=DOMAIN,DC=LOCAL
Source domain controller address:
d334c4a5-13da-4b7f-a9df-52754b7463b7._msdcs.DOMAIN.LOCAL
Intersite transport (if any):


This domain controller will be unable to replicate with
the source domain controller until this problem is
corrected.

User Action
Verify if the source domain controller is accessible or
network connectivity is available.

Additional Data
Error value:
1753 There are no more endpoints available from the
endpoint mapper.