I'm curious - are you trying to provide an Asio-like abstraction over a native SCTP stack, or provide an SCTP API for OS's that don't provide an SCTP stack (using Asio as part or all of the implementation)? I think this basic goal would determine much of the design. (Providing a full SCTP implementation seems like an ambitious task, while an Asio-like abstraction over a native stack seems much less so.) The HP doc on SCTP is excellent, btw (thanks for the link). How about providing your proposed API (with specifics on how it differs from Asio), then we can provide suggestions on the best way to implement it in conjunction with Asio? Or show code alternatives for the functions / methods you want to extend? (Your option 2 seems like the best way to go, but it's hard to tell without specific details.) Cliff