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Re: [spring] PSP and a logical application of RFC8200

Fernando Gont <fgont@si6networks.com> Tue, 03 March 2020 00:49 UTC

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To: Brian E Carpenter <brian.e.carpenter@gmail.com>, "Pablo Camarillo (pcamaril)" <pcamaril@cisco.com>, "Darren Dukes (ddukes)" <ddukes=40cisco.com@dmarc.ietf.org>, 6man WG <ipv6@ietf.org>, SPRING WG List <spring@ietf.org>
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From: Fernando Gont <fgont@si6networks.com>
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Date: Mon, 02 Mar 2020 21:46:25 -0300
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Subject: Re: [spring] PSP and a logical application of RFC8200
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On 2/3/20 20:21, Brian E Carpenter wrote:
> On 03-Mar-20 09:02, Pablo Camarillo (pcamaril) wrote:
>> Brian,
>>
>> The PSP pseudocode is presented as a modification to the End pseudocode starting at line S14 of such.
>> Please go through the PSP pseudocode in conjunction with the End pseudocode (Section 4.1).
>> You will see that the ingress state of the packet is (Segments Left == 1 and Destination Address == the PSP node's address).
> 
> Exactly my point. With SL == 1, you are not at the ultimate destination, so according to what I'll call "Fernando's reading" of RFC8200, you are not entitled to delete the header. That is the point that IMHO needs to be stated explicitly in the draft. You are using "Darren's reading" of RFC8200.
> 
> I really think you need to say so explicitly. Something like:
> 
> Note: this behavior does not contravene section 4 of [RFC8200]
> because the current destination address of the incoming packet
> is the address of the node executing the PSP behavior.

A node that does PSP essentially processes the SR header twice. How is 
that compliant with draft-ietf-6man-segment-routing-header itself?



-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
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