SteelHead™ Deployment Guide - Protocols : RiOS Version Compatibility with Domains and Domain Relationships : User Domain Is the Different from Server Domain (Bidirectional)—Delegation Mode
  
User Domain Is the Different from Server Domain (Bidirectional)—Delegation Mode
Use the following table when the use is in a different domain from the servers in question, there is a bidirectional trust relationship between the domains, and depending you want to use Delegation mode.
 
Delegation Mode
Different Domain
Bidirectional Trust

Domain(Server)
Windows XP Clients
Windows Vista and Windows 2008 Clients
Windows 7 and Windows 2008-R2 Clients
Windows 2000
None
None
None
Windows 2003
RiOS v6.1
RiOS v6.0
RiOS v6.1
Windows 2008
RiOS v6.1
RiOS v6.1
RiOS v6.1
Windows 2008-R2
RiOS v6.1
RiOS v6.1
RiOS v6.1