Currently we have the Request/Response interfaces that we use in wrapping the HttpServletRequest and HttpServletResponse instances. However, if we want to use these interfaces to wrap different request/response implementation objects, the current API doesn't always suit this. In addition, it'd be nicer to split the ServletRequestResponse class into a ServletRequest and ServletResponse class, and still keep the ServletRequestResponse class, but then as a wrapper of a ServletRequest and ServletResponse instance. Introducing PushRequest and PushResponse interfaces (as extensions to Request/Response) can also be utilized to introduce ICEpush-specific getters and setters for ease of development, like getSequenceNumber() and setSequenceNumber(). Then the implementation of these interfaces can decide where to retrieve the sequenceNumber from and where to put it depending on the wrapped Request/Response classes.