On Wed, 6 Jan 2010 11:50:05 -0500, you wrote: "Reserved" means "send zero, ignore on receipt". It most definitely does NOT mean "check on receive that this is zero", that's a silly mistake all too often make in protocol design. This too is for mixed version handling. If a new flag can safely be ignored by an older system, then the newer system can simply send that flag in what used to be a reserved field, and the right thing happens. Sure, but I'm not trying to implement something nor to make different DECnet versions cooperate. I'm just studying the actual content of some packets and have noticed some discrepancies between the standard specifications and the actual data on wire, sent from a VMS V7.2 box to another V7.2 system. :-) Finally, proxy was originally a VMS specific enhancement and was adopted in some other implementations (I know DECnet/E picked it up, at least in a semi-compatible form). I'm not sure that it was ever specified in an architecture spec. See above. What I'm looking at is the data exchange between two VMS boxes, both at V7.2, so it's not strange to see something about proxies. Speaking about specifications, I was thinking that DEC was quite strict about this and I was hoping that somewhere there was at least an update if not an entire new specification, or that someone would know who to ask for. BTW, all the differences I've found are in the session control protocol and the one about proxies is just one of them: another is in the contents of the format 2 "destination end user name". Thanks, G.