Hi Rein, Here are some comments and ideas regarding the DTN project: 1. For the multicast messages, I don't know what you have in mind but if you could split the message with a fixed granularity, say 8 bytes or 16 bytes, then the clients receiving the multicast message could simply request the missing fragments in turn. Each client may benefit from the previous repeats if it too is missing the same segment. This would reduce the overall repeats without the full overhead of a bundle protocol. 2. For ham application, I have have heard twice the comment that it would be great to have ideally the new emails (limited to the first X bytes) or at least the notification of new emails pushed to the clients. I was thinking that the concept of alerts you mentioned could be applied for that purpose, assuming a client's registration similar to the current "link to" concept. The current APRS message delivery lacks ARQ capability for that purpose unfortunately. Otherwise this is a pretty comprehensive list of functions I think. 73, John On Dec 24, 2011 8:31 PM, "Rein Couperus" <rein@xxxxxxxxxxxx> wrote: