A join between local table ls1 and remote table rl1 results in this query being sent to the remote server:
select a,b,c from localserver.testdb.dbo.ls1 t1, rl1 t2 where t1.a = t2.a
The statement sent to the remote server contains a fully qualified reference back to the local table on the local system. The remote server either dynamically creates a temporary proxy table definition for this table, or uses an existing proxy table with a matching mapping. The remote server then executes the join and returns the result set back to the local server.
See the Performance and Tuning Series: Query Processing and Abstract Plans.
