Implement a mechanism to resolve the ambiguity between (TCP) connection handles

Currently, the explicit communication backends (TCP, TLS, DTLS) craft a 16 Bit connection handle and pass that handle around with each request. Unfortunately, the handle is not unique, since it just consists of a few bits to identifiy the particular backend plus a simple index [0..n] to idenitfy the particular connection within the backend.

Now, since requests may take some time to process in the system, and the CIP layer and the backend layers are parallelized, it can happen that a connection is closed and reestablished while a request is being processed. To avoid that the response for a request received over one connection is sent over another, new connection, we should introduce additional means to achieve a unique connection identification for each new (TCP) connection. This can be achieved through an additional sequence number.