SLIM: Enabling Transparent Extensibility and Dynamic Configuration via Session-Layer Abstractions.

Increasingly, communication requires more from the network stack, e.g., seamless handoff and synchronization of state between multiple participants. Due to the lack of support for desired functionality, networking libraries are created to fill the void. This leads to considerable duplication of effort and complicates cross-platform development. Furthermore, the means for extending legacy protocol stacks is largely exhausted (e.g., the TCP options space in the SYN message is mostly allocated), making the addition of future extensions much more challenging. In this paper, we tease apart elements of session management that are currently conflated with the transport semantics in TCP and highlight the need for sessions in contemporary communications. Next, we propose session, flow, and endpoint abstractions that lead to a clearer description of advanced communication models. This effort results in an extensible session-layer intermediary (SLIM) that leverages the above abstractions to support the additional functionality needed by modern applications, such as mobility, communication between two or more participants, and dynamic reconfiguration. SLIM's approach also provides the means for future extensibility of the network stack in a backward-compatible way, thus enabling incremental adoption.