[168443] in North American Network Operators' Group
Re: OSPF Costs Formula that include delay.
daemon@ATHENA.MIT.EDU (Jeff Tantsura)
Sat Jan 25 13:56:39 2014
From: Jeff Tantsura <jeff.tantsura@ericsson.com>
To: Graham Beneke <graham@apolix.co.za>
Date: Sat, 25 Jan 2014 18:56:14 +0000
In-Reply-To: <52E3556E.4060705@apolix.co.za>
Cc: "nanog@nanog.org" <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
A path to a destination must be loop free, irrespectively.
So it is not a combination of multiple but rather a list of loop free paths=
to a destination where any other metrics are used as tie-breakers.
Another story - how do you get all that state distributed, inter-area cases=
, how do you make it actually useful ( LSDB vs TED ) and not to forget - FE=
C definition.=20
Regards,
Jeff
> On Jan 24, 2014, at 10:13 PM, "Graham Beneke" <graham@apolix.co.za> wrote=
:
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> The auto-cost capability in some vendors devices seems to have left many
> people ignoring the link metrics within their IGP. From what I recall in
> the standards - bandwidth is one possible link metric but certainly not
> the only one. Network designers are free (and I would encourage to) pick
> whatever metric is relevant to them.
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>> On 24/01/2014 22:26, Erik Sundberg wrote:
>> I am looking for a formula that other people are using .p
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> I've started to use a combination of 3 metrics to determine my costing:
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> * The traditional auto-cost calculation based on a 100Gbps reference
> which gives far more useful values than the old 100Mbps reference.
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> * An average or nominal link latency multiplied by a factor of 200.
> Sometimes adjusted if I want two geographically diverse paths between
> the same endpoints to have equivalent costs.
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> * Path length in km multiplied by 2. This accounts for situations when
> the nominal latency is too small to accurately determine and assumes 1
> ms per 100 km.
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> I then pick the largest of the above 3 metrics as my OSPF cost.
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> --=20
> Graham Beneke
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