From the url below, http://www.boost.org/doc/libs/1_53_0/doc/html/boost_asio/overview/core/async...
I found a note below.
Many operating systems offer a native asynchronous I/O API (such as overlapped I/O on Windows) as the preferred option for developing high performance network applications. The library may be implemented in terms of native asynchronous I/O. However, if native support is not available, the library may also be implemented using synchronous event demultiplexors that typify the Reactor pattern, such asPOSIX select().
I think this implementation looks similar to ACE. The proactor implementation varies depends on platforms. ACE uses native asynch IO features for Windows, Solaris but not for LINUX. I wanted to know if boost.asio implements asynch IO for LINUX not like ACE. But the note above gives me an impression that boost.asio is almost the same with ACE for LINUX and other platforms also.
The above note says that Asio relays on the native async. i/o where availble. Do you expect Asio to make use of native async. i/o where it's *unavailable*? The main difference between ACE and Asio is in their high-level interfaces.