Packet Delivery Context

Overview

Packet Delivery Contexts (PDCs) are the Ultra Ethernet Consortium's replacement for traditional network connection state. Unlike TCP/RDMA connections that are created and managed by software, PDCs are invisible to the application, created and destroyed automatically by hardware on demand — standing up with zero round trips (pipelined with the first message) and closing in one RTT (which can be hidden behind other concurrent traffic). This ephemeral model eliminates the connection-count scaling problem that plagues RoCEv2 in large AI clusters, where tens of thousands of GPUs maintaining persistent all-to-all connection state becomes a memory and management bottleneck. Each PDC exists only while data is in flight; when idle, it consumes no resources.