[HECnet] DECnet et al

[Johnny Billquist]

On 2011-07-17 20.10, Bob Armstrong wrote:
The term segment is used because each node that runs the
bridge program does filter packets that should stay local.

    Ah, so the bridge program is not really a bridge (at least not in the way
I use the word).   Usually I think of a bridging two networks as meaning to
copy all traffic from network A to network B and vice versa.   If the box or
program does something smart about deciding which traffic should go where,
then it's a "router" (or at least a "switch").

Hans gives the bridge program too much credit. :-)

    How does the bridge program decide what DECnet messages to bridge and what
to drop?

It only have one small optimization, in the same vein as a switch. If it knows the destination (have seen traffic from it previously), it will only propagate traffic to that other end if it is directed traffic.

A router would be something very different, and way more clever. But a router would actually be a very nice thing to implement. If anyone feel like it, I'd be happy to help.

The difference between a switch and my bridge program is mostly in that the bridge program works using UDP as a carrier for remote endpoints, as well as interfacing to local ethernets. It can also do some traffic throttling, but unlike a switch, it does not do something like STP, nor do it do any kind of ethernet autonegotiation. It does not really play with ethernet on a low enough level for that.

	Johnny