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Re: [OSPF] PHP route determination in draft-ietf-ospf-segment-routing-extensions-03

Peter Psenak <ppsenak@cisco.com> Thu, 02 April 2015 10:17 UTC

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Date: Thu, 02 Apr 2015 12:17:42 +0200
From: Peter Psenak <ppsenak@cisco.com>
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To: Santanu Kar <santanu.kar@ipinfusion.com>, ospf@ietf.org, sprevidi@cisco.com, cfilsfil@cisco.com, hannes@juniper.net, rob.shakir@bt.com, wim.henderickx@alcatel-lucent.com
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Cc: Penchala.Reddy@ipinfusion.com
Subject: Re: [OSPF] PHP route determination in draft-ietf-ospf-segment-routing-extensions-03
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Santanu,

On 4/2/15 11:34 , Santanu Kar wrote:
> Hi Peter
>
> I think, considering we are using Ext Prefix LSA in 'Area-Flooding' scope, A
> should do PHP for 20.1.1.0/24  if C has advertised it.

I do not see why would you do PHP, if B is not advertising the SID.

> If  A doesn’t pop for 20.1.1.0/24, and give the packet to B, it will drop
> it, since PHP is enabled by default for all nodes.

why would it drop? B will get the packet with the label that corresponds 
to 20.1.1.0/24.

regards,
Peter

>
> Regards
> Santanu
>
> -----Original Message-----
> From: Peter Psenak [mailto:ppsenak@cisco.com]
> Sent: Thursday, April 02, 2015 1:08 PM
> To: Santanu Kar; ospf@ietf.org; sprevidi@cisco.com; cfilsfil@cisco.com;
> hannes@juniper.net; rob.shakir@bt.com; wim.henderickx@alcatel-lucent.com
> Subject: Re: PHP route determination in
> draft-ietf-ospf-segment-routing-extensions-03
>
> Santanu,
>
> If B is not advertising a SID for 20.1.1.0/24, then A will not do PHP.
>
> regards,
> Peter
>
>
> On 4/2/15 08:39 , Santanu Kar wrote:
>> SANTANU> Iactually wanted to highlight the non-ABR cases here.
>> SANTANU> Consider
>> the3routers below,in same area.
>>
>>    A -----10.1.1.0/24----- B ------20.1.1.0/24 -----C
>>
>> In thecontext of A, the route of 20.1.1.0/24 <http://20.1.1.0/24> is a
>> PHP route. Now the Prefix Segment for prefix 20.1.1.0/24
>> <http://20.1.1.0/24> can be advertised by bothB, as well as by C
>> towards A. The case I am considering here is, C has advertised the
>> prefix segment of 20.1.1.0/24 <http://20.1.1.0/24> to Afirst.Stillwhen
>> A is calculating label for20.1.1.0/24 <http://20.1.1.0/24>,it should
>> take it as PHP. Howeverthe text in draft states "upstream neighbor of
>> the Prefix-SID originator MUST pop the Prefix-SID". Here A is not the
>> upstream neighbor of C.
>>
>

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