Benefit of layering The most challenging problem: how to provide a reliable data transfer service on top of an unreliable data network? This problem is so important that today's operating Systems all provide such reliable service. The burden of network application developers has been reduced significantly! -Hence the application developers can simply focus on the application layer issues. -We can easily develop thousands of network applications 1717 Benefit of layering • The most challenging problem: how to provide a reliable data transfer service on top of an unreliable data network? —This problem is so important that today’s Operating Systems all provide such reliable service. • The burden of network application developers has been reduced significantly! —Hence the application developers can simply focus on the application layer issues. —We can easily develop thousands of network applications