Subject: [Pce] Clarification regarding SR-ERO Validation Error

From: Mrinmoy Das <[email-masked]>
Date: Tue, 22 Feb 2022 16:52:05 +0530

Hello Team,

I found below SR-ERO validation in RFC 8664, 5.2.1
<https://datatracker.ietf.org/doc/html/rfc8664#section-5.2.1>. SR-ERO
Validation

   The SR-ERO subobjects can be classified according to whether they
   contain a SID representing an MPLS label value or an index value, or
   no SID.  If a PCC detects that the SR-ERO subobjects are a mixture of
   more than one of these types, then it MUST send a PCErr message with
   Error-Type = 10 ("Reception of an invalid object") and Error-value =
   20 ("Inconsistent SIDs in SR-ERO/SR-RRO subobjects").

As per my understanding of the above text, there could be three types of
SIDs:

1. *SID index: *S-bit = 0, M = 0,C = 0
2. *SID as MPLS label:* S-bit = 0, M = 1, C = 0/1
3. *Null:* S-bit = 1

Now, if a LSP contains 3 SR-ERO subobjects then all those three should have
the same SID type, e.g. all may be type 1, or type 2 or type 3 and there
shouldn't be any combination of these 3 types.

Is this understanding correct? Please let me know.

Thanks,
Mrinmoy

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From: Dhruv Dhody <[email-masked]>
Date: Tue, 22 Feb 2022 17:17:16 +0530

Hi Mrinmoy,

On Tue, Feb 22, 2022 at 4:52 PM Mrinmoy Das <[email-masked]> wrote:

> Now, if a LSP contains 3 SR-ERO subobjects then all those three should
> have the same SID type, e.g. all may be type 1, or type 2 or type 3 and
> there shouldn't be any combination of these 3 types.
>
Yes! Your understanding is correct.

Thanks!
Dhruv

> Thanks,
> Mrinmoy
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From: Mrinmoy Das <[email-masked]>
Date: Tue, 22 Feb 2022 17:19:46 +0530

Thanks Dhruv for the clarification.