Efficient Cross-Layer Negotiation

Internet evolution often depends on either inserting new protocol layers or upgrading existing layers to new protocols, but both of these evolutionary paths are obstructed by the difficulty and inefficiency of determining which protocols a pair of hosts mutually support and prefer. We propose a novel cross-layer Negotiation Protocol that sets up a complete stack of connection-oriented protocols at once, concurrently performing handshaking for multiple layers and choosing among alternative protocols for each layer in as few round trips as possible, often just one. The initiator proposes a protocol graph explicitly encoding possible configurations along with protocol-specific handshake data; the peers then prune, refine, and atomically commit to a final configuration, exchanging messages over a specialized transport that can operate in-line with the negotiated protocol stack. Although a practical Negotiation Protocol presents many challenges, our initial exploration suggests that these challenges are solvable, and we believe addressing them is a necessary step toward a more evolvable Internet.