The purpose of this document is to guide the design of congestion notification in any lower layer protocol that encapsulates IP. The aim is for explicit congestion signals to propagate consistently from lower layer protocols into IP. Then the IP internetwork layer can act as a portability layer to carry congestion notification from non- IP-aware congested nodes to the destination transport endpoint. Following these guidelines should assure interworking between new encapsulations of congestion notification, whether specified by the IETF or other standards bodies.