Re: Cost calculating in the OSPF area

["Jevos, Peter" <Peter.Jevos at ORIFLAME-SW.COM>]

Thanks for your answers,

I think I was wrong when I specified my question. I'm looking for some
tool or program , which calculate shortest path. Every cost on the links
is defined but I'd like to know if something happened (changed ) when I
add a new router into system. I know it is matter of Dijsktra's
algorithm, all I'm asking if somenone's using some program to calulate
the shortest path

Thanks 

Pet  

-----Original Message-----
From: Mailing List [mailto:OSPF at PEACH.EASE.LSOFT.COM] On Behalf Of Dave
Katz
Sent: Thursday, February 09, 2006 7:30 AM
To: OSPF at PEACH.EASE.LSOFT.COM
Subject: Re: Cost calculating in the OSPF area

The short version is that OSPF is a lousy mechanism for doing traffic
engineering.  You can influence path selection by the use of areas
and/or link costs, but at the end of the day it will do what it does.

If you really need engineered paths, there are more appropriate
mechanisms than OSPF.

--Dave

On Feb 8, 2006, at 3:33 PM, Erblichs wrote:

> Pet,
>
> 	First, it doesn't matter what the costs are if their
> 	is only one path from each source to each destination.
> 	
> 	Second, if their is only one BB ABR (some ABRs don't have
> 	a BB area), paths to the BB will transit the BB ABR and
> 	again, it doesn't make a diff as to the cost of those paths.
>
> 	Third, if you admin set the priority so that more than 1
> 	router can be a DR, then output costs come into play,
> 	else the output cost of the DR is irrevalent.
>
> 	So, all we need to determine the say X routes that
> 	each have alternate paths.
>
> 	The preferred paths should have a lowest summed costs, how much
> 	lower is irrelevent.
>
> 	The key is that primary paths SHOULD use as one or more
> 	key values as to bandwidth capacity of the line, delays
> 	introduced, costs thru a link, etc. But again this only
> 	makes a diff for the paths that have alternates.
>
> 	Thus Peter, if this doesn't simplify what you are asking,
> 	because you have a large number of alternate possible paths
> 	and all routers can be DR/BRS, and you have multiple BB ABRs,
> 	then you need a consultant.
>
> 	Mitchell Erblich
> 	-------------------
>
> 	
>
> 	
> "Jevos, Peter" wrote:
>>
>> Hello all,
>>
>> I have one questions about ospf metric. I designed a big network with

>> at least one hundred routers with ospf. I'd like to know if exists 
>> some utility, tool, program, software, excel sheet or whatever, which

>> simulate or calculate ospf cost.
>> My problem is following. When I add one or more router into this 
>> system, traffic could change because of lower value of added links 
>> and it could affect almost entire traffic.
>> Thanks a lot
>> Pet
>