[HECnet] Network topology according to MIM.

[Johnny Billquist]

On 2016-01-15 06:30, Robert Armstrong wrote:
>> That HECnet works is not really that much of a trick.
>
>    I wouldn't agree, but the issues I'm thinking of are not technical.  Try getting everyone to agree on a cost structure, for example.

Well, the problem with that is that you (I think) and Peter have been 
believing that you have a problem that can be solved by playing with 
costs in a way that will not solve the problem. You are essentially 
hitting up against a problem with DECnet routing, and you can never get 
this optimal. It is just not possible. And the reason is because of how 
DECnet work. Tweaking your costs to always favor multinet point-to-point 
links will sometimes turn out better, and sometimes worse. Just like the 
other way around. Like I just pointed out in my connection to area 59. 
Wether the ethernet link, or my ptp link is preferrable depends on where 
I would like to go in area 59, and the topology of area 59. And those 
two things are something that MIM can never know. Now, I can know where 
I usually want to communicate to in area 59, but I still don't know 
which ingress to area 59 is better for that purpose. And any cost Peter 
might put on *anything* in area 59 will not change that, since all those 
costs are invisible to anyone outside area 59. And also, optimal would 
actually suggest that I should use different ingress points into area 59 
depending on where to I am communicating, but DECnet cannot do that. All 
traffic to area 59 from MIM will always go through the same path, no 
matter what.

But in general, I would agree that it's always hard to make a large 
group of people agree on anything, yes. :-)

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol