14 Jan
2016
14 Jan
'16
10:35 p.m.
On 2016-01-14 22:26, hvlems at zonnet.nl wrote:
Johnny,
When the area routers in the other area are on the same LAN then the bridge w?ill only be
involved if there is another area router in that other area on the remote side of the
bridge program.
And will (very likely) slow down communications.
The bridge have no clue about areas at all. No more than a physical
ethernet cable would. There don't have to be area routers on any side.
But if there are, they are no different from any other ethernet node.
Can the bridge program detect whether there are area
routers for the dame area at both ends and favor the local one, possibly block advertising
of the remote area router?
I tried blocking traffic from a node in one area from getting to another
area, with the exception of packets from area routers.
Unfortunately, it does not work. DECnet can be clever about local
ethernet connectivity. If you are on the same ethernet segment, nodes
can communicate directly with other nodes on the same ethernet segment,
even if they are endnodes, and this exen extends to nodes on different
areas. So such filtering in the bridge cause communication to fail for
endnodes on the ethernet segment, when the destination is on the same
ethernet, even if in a different area.
(I hope the explanation makes sense, otherwise I can try and explain it
more. I tried doing this many years ago, and ended up realized it cannot
be done.)
Johnny
Hans
Verzonden vanaf mijn BlackBerry 10-smartphone.
Origineel bericht
Van: Johnny Billquist
Verzonden: donderdag 14 januari 2016 22:06
Aan: hecnet at Update.UU.SE
Beantwoorden: hecnet at Update.UU.SE
Onderwerp: Re: [HECnet] Multinet peerings...?
On 2016-01-14 21:38, Peter Lothberg wrote:
If all links in HECNet where point-to-point, with the same metric on
both sides, it will most likely be almost *perfect* by itself.
The complex movie is when they *THINK* they are all on the same
ethernet with metric 1.....
Well, in all honesty, default cost for ethernet links in VMS is 4, and
in RSX is 3...
So, if you want to favor a different link, set the cost to less.
But you are blindly assuming that Multinet (or other) point-to-point
links are better. That one I still do not see. There are definitely
cases where it can be worse.
The worst thing about the bridge is, as I wrote in another mail, is when
you are on an ethernet segment, and you want to talk to a different
area, which have several area routers on that same ethernet segment you
are on, in which case you might end up going through pretty bad hopping.
Johnny
On Jan 14, 2016, at 3:02 PM, Peter Lothberg
<roll at Stupi.SE> wrote:
> The values are somewhat arbitrary; it doesn't really matter what
> scheme you use but if you are inconsistent the routing may be
> surprising.
>
> The routing spec has a suggested algorithm (100,000/line speed)
> which may have made sense in the old days but for modern networks
> isn't terribly useful.
> paul
What I wanted to get to was a scenario where traffic was symetric
between two nodes, eg, use the same links from a-b as b-a, it makes it
much easier to understand what's wrong when things behave funny...
If costs are the same at both ends of a link, that will certainly
help. Then again, it is quite possible for two paths to have equal
cost, and if so, DECnet implementations will pick one of the two, in
a way that is not specified.
paul