The Johns Hopkins University Applied Physics Laboratory Science Applications International Corporation This document describes a UDP convergence layer (UDPCL) for Delay- Tolerant Networking (DTN). This version of the UDPCL protocol clarifies requirements of the earlier experimental RFC 7122, adds discussion of multicast addressing, congestion signaling, and updates to the Bundle Protocol (BP) contents, encodings, and convergence layer requirements in BP version 7. Specifically, the UDPCL uses CBOR-encoded BPv7 bundles as its service data unit being transported and provides an unacknowledged transport of such bundles. This version of UDPCL also includes security and extensibility mechanisms.