All, In light of the recent email threads on the topic of ACK it is worthwhile to revisit the enclosed doc that generated last year and uploaded to the EI list . In this doc are a set of requirements that outline what response a VEN may have to give to a VTN in response to receiving an EIEvent message. These requirements are specific to EIEvent and not intended to cover the other services in EI. Of particular note is that some of these requirements can be fulfilled with transport level mechanisms and some cannot. Thanks, -ed Koch Requirements for VEN Responses to DR Signals.pdf