[HECnet] Multinet circuit costs

[Johnny Billquist]

On 2012-01-06 00.26, Steve Davidson wrote:
They are valid, but not necessarily preferred.   Only the site owners can determine that.

True. But if you prefer one over the other, you should not set the cost equal on your interfaces. If you really only want to use one if the other is broken, make it *very* expensive.

	Johnny


-Steve


________________________________

From: owner-hecnet at Update.UU.SE on behalf of Johnny Billquist
Sent: Thu 1/5/2012 18:06
To: hecnet at Update.UU.SE
Subject: Re: [HECnet] Multinet circuit costs



No. Equal cost paths are valid. DECnet will do one of two things. Either
pick one on random (well, there is some algorithm to it, but it don't
matter, it will pick one anyway), or if the DECnet is slightly more
modern than plain phase IV (it was called phase IV+ if I remember
right), then DECnet will do equal path cost splitting. That is, it will
use both paths.

                Johnny

On 2012-01-05 16.58, Steve Davidson wrote:
The circuit costs here are set to 4 for LAN and 3 for tunnels.   The issue may be that if a node (at the end of the chain so to speak) has 2 tunnel links of the same cost and that the final destination costs the same I could see where DECnet *might* get confused.   Let's look at the following contrived example:

FRUGAL:: connects to LEGATO:: - cost of 3
FRUGAL:: connects to SG1::             - cost of 3

LEGATO:: connects to GORVAX:: - cost of 3
SG1::             connects to GORVAX:: - cost of 3

Fred, on node FRUGAL:: tries to copy a (large) file from GORVAX:: to FRUGAL:: *may* see some issues.   On the other hand if Fred chooses to favor SG1:: over LEGATO:: (cost wise) he should not see any problems:   Ex:

FRUGAL:: connects to LEGATO:: - cost of 3
FRUGAL:: connects to SG1:: - cost of 2

The route is guaranteed to be the same for the entire transaction.   It will be (using poor man's routing to demonstrate) FRUGAL::SG1::GORVAX:: at a cost of 5, not FRUGAL::LEGATO::GORVAX:: at a cost of 6.

-Steve

________________________________

From: owner-hecnet at Update.UU.SE on behalf of hvlems at zonnet.nl
Sent: Thu 1/5/2012 10:43
To: hecnet at Update.UU.SE
Subject: Re: [HECnet] Multinet circuit costs



PS
I can copy to Legato alright.

PPS
I did check the netserver.log files and found nothing out of the order.