Breaking Up the Transport Logjam

Current Internet transports conflate transport semantics with endpoint addressing and flow regulation, creating roadblocks to Internet evolution that we propose to address with a new layering model. Factoring endpoint addressing (port numbers) into a separate {\em Endpoint Layer} permits incremental rollout of new or improved transports at OS or application level, enables transport-oblivious firewall/NAT traversal, improves transport negotiation efficiency, and simplifies endpoint address space administration. Factoring congestion control into a separate {\em Flow Layer} cleanly enables in-path performance optimizations such as on satellite or wireless links, permits incremental rollout of new congestion control schemes within administrative domains, frees congestion control evolution from the yoke of ``TCP-friendliness,'' and facilitates multihoming and multipath communication. Though this architecture is ambitious, existing protocols can act as starting points for the new layers---UDP or UDP-Lite for the Endpoint Layer, and Congestion Manager or DCCP for the Flow Layer---providing both immediate deployability and a sound basis for long-term evolution