Create ACNET node MCDPMD
The ACNET node tables contain several entries associated with multicast addresses. These entries provide a shared channel of communication instead of referring to a single computer.
MCAST internally as the multicast address 220.127.116.11. As of this writing, the node table contains these other multicast nodes1:
|Node Name||Multicast Address|
Right now, all DPM clients are using
MCAST to do service discovery which means every ACNET node is receiving those messages when only 8 (currently) need to. We used to have a multicast node,
DPMD, but removed it2. I think I'd like to have a new, multicast node,
MCDPMD, and have DPM and its clients use it.
To avoid disruption:
- Create the node
MCDPMDand associate it with an unused multicast address.
- Modify the DPM code to create a
MCDPMDhandle and only use it to process service discovery messages.
- Restart all the DPMs. When they create their
acnetdwill join the
acnetdwill still be listening to the
MCASTaddress, so current DPM client requests will still work.
- Convert client libraries to use the new node address so that only the DPM nodes will see the flood of discovery requests.
Concerns, comments are welcome.
1 It makes sense that
MCAST have the same multicast address.
DNLDD should probably have its own, unique address, however.
2 The way multicast support works in
acnetd is, if your handle matches a multicast node name,
acnetd joins the multicast. The other side effect is that
acnetd allows multiple clients to use the same multicast handle. This is why we deprecated the
DPMD node name; because multiple clients can appear on a given node as
DPMD and you wouldn't have a way to give one of the clients your DPM request.
#5 Updated by Richard Neswold about 1 year ago
NML Clock isn't in the ACNET node table because it's outside the ACNET protocol (i.e. it's not using port 6801) so it's still valid. The look-up service was abandoned for the same reason as DPM; multiple clients could use the handle on a given node and make the service unreliable. I'll let Charlie decide if he wants to make a similar change to the LOOKUP service as we're trying to do for DPM. I don't know what "requests to STATES" means. Brian? Jim? (The fact that neither are in the node table makes me think they're unused.)