[HECnet] Attaching to hecnet

[H Vlems]

Paul,
The overhead incurred by level 1 or level 2 routing was pretty low. The site
I mentioned in the earlier example grew to more than 1000 pc's. They all ran
DECnet for Pathworks connectivity. They just fitted in one DECnet area. The
area routing was performed by two microVAX II systems, one active, the other
backup. They did nothing but area routing and had sufficient cpu power and
memory available. Ethernet was 10BASE2 in those days and that worked well.
The only traffic outside the area was CTERM and a little FAL.

The reason we didn't turn of console logging was that plant personnel
archived the console logs for reference purposes.
Hans

-----Oorspronkelijk bericht-----
Van: owner-hecnet at Update.UU.SE [mailto:owner-hecnet at Update.UU.SE] Namens
Paul Koning
Verzonden: dinsdag, juni 2010 12:55
Aan: hecnet at Update.UU.SE
Onderwerp: RE: [HECnet] Attaching to hecnet

Johnny, the original DECnet manuals showed pictures of area routers
that
were interconnected by WAN links. Each site had its own area number.
In
fact
the name "area routing" implies clearly that the concept was meant to
set up
DECnet networks that were geographically separated.

I don't remember those pictures, but this is an issue that generated a
lot of debate and a lot of annoyance in the DECnet architecture group.

...
One reason for separating systems in different areas was that
rebooting
the
pc's would generate so many DECnet state up and down messages that
PDP-
11's
and the older VAX systems choked in their console output.

That's a good one.   (Actually, the way to deal with that is to turn the
logging to console off for that event...)   Yes, that's a valid example.

The purpose of area routing is to avoid having things get too large.
There were various opinions on how big an area (or Phase III network)
could reasonably be.   Originally the limit was assumed to be about 32,
without any basis that I know of.   That too produced a pile of debate,
and later on it became obvious you could go much higher.   But clearly
you couldn't run a flat Phase III style network with 10,000 nodes.   

For that reason area routing was introduced, so each instance of the
routing algorithm (in-area and level 2) would deal with a reasonably
small topology.   Again debates broke out whether a full area (1000
nodes) was acceptable.   It turned out yes, but certainly keeping it
smaller, say to 100-200, would be a good thing if possible.

Geography isn't a consideration unless the links are slow enough to make
route change propagation an issue.   Corporate organization (different
departments) CERTAINLY isnt' a consideration, though some people tried
to argue that it was valid to do so.

	paul
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