How Domain and Forest trusts work: https://technet.microsoft.com/en-us/library/cc757352(v=ws.10).aspx
EMC ISILON SID translation errors: https://community.emc.com/thread/177333?tstart=0
Actions to do:
Check Trust relationships
Check Firewall logs and use portqry to test ports required. Also use nltest; netdom command lines.
Check GPO: Network access: Allow anonymous SID/Name translation
and The following groups have the “Access this Computer from the Network” permission on domain controllers by default: