[168396] in North American Network Operators' Group
Re: OSPF Costs Formula that include delay.
daemon@ATHENA.MIT.EDU (Owen DeLong)
Fri Jan 24 15:39:06 2014
From: Owen DeLong <owen@delong.com>
In-Reply-To: <495D0934DA46854A9CA758393724D5903B9787@NI-MAIL02.nii.ads>
Date: Fri, 24 Jan 2014 12:36:48 -0800
To: Erik Sundberg <ESundberg@nitelusa.com>
Cc: "nanog@nanog.org" <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Some networks I have worked with took the average latency of each link =
and assigned that (with some constant multiple) as the interface cost.
Of course this all fails miserably if you are using anything like MPLS =
underneath your OSPF.
Owen
On Jan 24, 2014, at 12:26 PM, Erik Sundberg <ESundberg@nitelusa.com> =
wrote:
> I understand OSPF default calculation for cost doesn't include delay. =
I am looking for a formula that I can use to manually set the OSPF costs =
that factors in delay.
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> When using OSPF's default costs, the shortest path is not always the =
optimal path.
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> Example
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> New York to Los Angeles. Assuming all links are the same bandwidth and =
have a ospf cost of 1.
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> Path 1 (75ms) - OSPF Cost 2 - New York > Dallas > Los Angeles
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> Path 2 (65ms) - OSPF Cost 3 - New York > Chicago > Denver > Los =
Angeles
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> If I left the default cost's alone then path 1 would win because it =
has a lower ospf cost, however it take traffic 10ms longer to get there.
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> However I would like traffic to take Path 2 by adjusting the OSPF =
cost.
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> I am looking for a formula that other people are using .p
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> Thanks
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> Erik
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> -----Original Message-----
> From: Randy [mailto:randy_94108@yahoo.com]
> Sent: Thursday, January 23, 2014 9:03 PM
> To: Erik Sundberg; nanog@nanog.org
> Subject: Re: OSPF Costs Formula that include delay.
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> ----- Original Message -----
>> From: Erik Sundberg <ESundberg@nitelusa.com>
>> To: "nanog@nanog.org" <nanog@nanog.org>
>> Cc:
>> Sent: Thursday, January 23, 2014 4:47 PM
>> Subject: OSPF Costs Formula that include delay.
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>> What is everyone using for an OSPF cost formula that factors in a
>> circuits delay and bandwidth (10M-100G)???
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>> Thanks in advance
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> umm..are you sure your question is not about EIGRP?
> OSPF has no concept of interface-delays.
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> The default reference bandwidth for OSPF is 100M
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> In your case if you set your reference bandwidth to 100000 your 100G =
links would have a link cost of 1, 10G - 10, 1G-100, 100M-1000 and =
10M-10000
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> A vendor specific list would be a better place to ask.
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> ./Randy
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> ________________________________
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