Aalyria Technologies This document defines an optional extension to the Bundle Transfer Protocol - Unidirectional, as described in [BTPU], to enable forward error correction (FEC) coding to be applied selectively to the transfer of individual bundles on a case by case basis. The definition and use of FEC follows the FECFRAME framework defined in [RFC6363], and this document introduces new Message types to BTPU in order to carry the FEC information as defined in the framework.