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

[Santanu Kar <[e-mail]>]

Hi Peter

-----Original Message-----
From: Peter Psenak [mailto:[e-mail]]
Sent: Thursday, April 02, 2015 3:48 PM
To: Santanu Kar; [e-mail]; [e-mail]; [e-mail];
[e-mail]; [e-mail]; [e-mail]
Cc: [e-mail]
Subject: Re: PHP route determination in
draft-ietf-ospf-segment-routing-extensions-03

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.
[SANTANU] Since PHP is enabled globally, B may not expect a label packet for
20.1.1.0/24 as it expects it to be POPed in penultimate node. So B may
choose not to install any POP entry for 20.1.1.0/24. In that case packet
will be dropped.

regards,
Peter

>
> Regards
> Santanu
>
> -----Original Message-----
> From: Peter Psenak [mailto:[e-mail]]
> Sent: Thursday, April 02, 2015 1:08 PM
> To: Santanu Kar; [e-mail]; [e-mail];
> [e-mail]; [e-mail]; [e-mail];
> [e-mail]
> 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.
>>
>

-- 
.