http://www.rfc-editor.org/rfc/rfc1575.txt
RFC 1575: An Echo Function for CLNP (ISO 8473), S. Hares, C. Wittbrodt1994-02-01T23:00:00-00:00This memo defines an echo function for the connection-less network layer protocol. The mechanism that is mandated here is in the final process of being standardized by ISO as "Amendment X: Addition of an Echo function to ISO 8473" an integral part of Version 2 of ISO 8473. [STANDARDS-TRACK]