I just came across a good article by Keith Brown on a common trap when
setting up
SQL Server with kerberos delegation. As he noted, the port number for the
Sql Server Service should be specified when setting the service principal name
(SPN).
Delegation is a powerful feature of Active Directory but can be difficult to
setup. It can be used to allow SQL Server to impersonate the user when
connecting to other services: such as BULK LOAD connecting to a network file
server. Or for middle tier applications to impersonate users on other servers. A
detailed
explanation of delegation can be found here.
Microsoft’s whitepaper on
troubleshooting kerberos delegation has more detail on setting up SQL
Server, including linking servers with delegation.