[HECnet] DECnet et al

[Johnny Billquist]

On 2011-07-17 19.55, Bob Armstrong wrote:
No. By the endnode itself. It have no idea where to send it. For
ethernet, DECnet supposedly already knows the MAC address where to send
every packet. Where would it send a packet that isn't to the local
ethernet segment?

    All the end node needs to know to send an Ethernet frame is a MAC for the
destination, and if it knows the DECnet node number then it knows the MAC by
definition.   Anything beyond that is not its problem.

Right. But this only works if the destination is in the same ethernet segment.

    That's what the bridge program does, right?   Moves those DECnet Ethernet
frames, via TCP/IP (or UDP - I forget which you used) over Internet to
another LAN ?

Right. (UDP)

    BTW, what do you mean by Ethernet "segment" in the context of the bridge
program?   Aren't bridged "segments" by definition the same segment (at least
as far as DECnet messages go)?   Or is the bridge itself doing something
smart with DECnet traffic?

Yes, the bridge makes it all look like it's on the same segment. But HECnet as a whole is not connected to this segment... There are parts that are further away, with routers in between, and which have point-to-point connections using DECnet over TCP, as provided by VMS Multinet.

And also, some places use the bridge for HECnet access, but have a separate local ethernet segment with their own area traffic going in.

Someone should at some point make a connectivity graph for HECnet. That would be cool. Where you could see all the segments and connections...

	Johnny