Subject: [mpls] Question on draft-lm-mpls-sfc-path-verification

From: Loa Andersson <[email-masked]>
Date: Thu, 17 Sep 2020 13:09:18 +0800

Yao,

This is a follow up from your presentation at the MPLS interim meeting 
September 16, 2020.

Thank you for the draft, I think the the problem you are addressing 
might turn out to be real.

A few early comments though.

You are defining new a new LSP Ping TLV and two  sub-TLVs for this TLV, 
but there are no IANA section in the document. An IANA section would 
probably have made it easier to parse the document.

However mostly my question was because I missed the early slides, 
including the SFC Validation TLV.

So let us see if I got it right after reading the document and go over 
the slides again.

You define a new LSP Ping TLV - the SFC Validation TLV.

You also define two sub-TLVs - the SFC Info Sub-TLV and the SFC Basic 
Unit FEC Sub-TLV.

The SFC Validation TLV may be included in a MPLS echo request or an MPLS 
echo reply.

The SFC Basic Unit FEC Sub-TLV maybe included in a SFC Validation TLV 
carried both in a MPLS echo request and a MPLS echo reply.

The SFC Info Sub-TL mayb be included in a SFC Validation TLV only if the 
TLV is carried in a MPLS echo replay.

Correct?

You need to define which range the TLV and sub-TLVs should be allocated 
from.

/Loa
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Loa Andersson                        email: [email-masked]
Senior MPLS Expert                          [email-masked]
Bronze Dragon Consulting             phone: +46 739 81 21 64

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From: <[email-masked]>
Date: Thu, 17 Sep 2020 18:47:12 +0800 (CST)

Hi Loa,

Thanks a lot for reaching back to me and your time for reading the draft.

Please find my responses inline, see [Yao].

原始邮件

发件人：LoaAndersson <[email-masked]>
收件人：[email-masked] <[email-masked]>;[email-masked] <[email-masked]>;[email-masked] <[email-masked]>;刘尧00165286;
日 期 ：2020年09月17日 13:09
主 题 ：Question on draft-lm-mpls-sfc-path-verification

Yao,

[Yao] The IANA session will be added in the next version, thanks for the suggestion.

The SFC Validation TLV may be included in a MPLS echo request or an MPLS 
echo reply.
[Yao] Yes, the SFC Validation TLV may be included in both the MPLS echo request and the MPLS echo reply.

The SFC Basic Unit FEC Sub-TLV maybe included in a SFC Validation TLV 
carried both in a MPLS echo request and a MPLS echo reply.
[Yao] Currently the SFC Basic Unit FEC Sub-TLV is denfined as a sub-TLV of the Target FEC Stack TLV,  carried in a MPLS echo request. Its usage is similar to other sub-TLVs of the Target FEC Stack. The information carried in the Basic Unit FEC Sub-TLV is obtained from the control plane.  After receiving a MPLS echo request with the Target FEC Stack TLV and the SFC Basic Unit FEC Sub-TLV included, an SFF may enter the FEC validation procedure to check whether the information is the same between the control place and the local data plane. If the validation is not passed, the SFF will generate an MPLS echo reply with an error code as defined in RFC8029.

[Yao] Yes, the SFC Info Sub-TLV can only be carried in a MPLS echo reply.

Correct?

You need to define which range the TLV and sub-TLVs should be allocated 
from.
[Yao] I'll make the definition more clear as you suggested. Thank you again.

/Loa
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From: Loa Andersson <[email-masked]>
Date: Fri, 18 Sep 2020 11:16:01 +0800

Yao,

So most is sorted out :).

Some small issues.

On 17/09/2020 18:47, [email-masked] wrote:
> [Yao] Currently 
"currently means that it is defined in section 3.3 of 
draft-lm-mpls-sfc-path-verification, right. I find the definition is 3.3 
rather weak, more detals is needed. e.g. that the sub-tlv is defined for 
FEC Stack TLV (TLV #1).
the SFC Basic Unit FEC Sub-TLV is denfined as a sub-TLV
> of the Target FEC Stack TLV,  carried in a MPLS echo request. Its usage 
> is similar to other sub-TLVs of the Target FEC Stack. 
ok- fine, but the sub-TLVs are shared between TLV 1, 16, and 21. Is that 
true for the SFC Basic Unit FEC Sub-TLV?
The information
> carried in the Basic Unit FEC Sub-TLV is obtained from the control 
> plane.  After receiving a MPLS echo request with the Target FEC Stack 
> TLV and the SFC Basic Unit FEC Sub-TLV included, an SFF may enter the 
> FEC validation procedure to check whether the information is the same 
> between the control place and the local data plane. If the validation is 
> not passed, the SFF will generate an MPLS echo reply with an error code 
> as defined in RFC8029.
OK - and you need to point out the range from which the sub-tlv should 
be allocated.

/Loa

PS

Plz note that we are doing updates to the LSP Ping registry, so far I 
have not seen anything that directly have an impact on this draft.
See - draft-ietf-mpls-lsp-ping-registries-update-.

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From: <[email-masked]>
Date: Fri, 18 Sep 2020 23:07:46 +0800 (CST)

Hi Loa,

Thanks for your questions and suggestions.

Please see in line with [Yao].

原始邮件

发件人：LoaAndersson <[email-masked]>
收件人：刘尧00165286;
抄送人：[email-masked] <[email-masked]>;[email-masked] <[email-masked]>;[email-masked] <[email-masked]>;
日 期 ：2020年09月18日 11:16
主 题 ：Re: Question on draft-lm-mpls-sfc-path-verification

Yao,

Some small issues.

On 17/09/2020 18:47, [email-masked] wrote:
>  Currently 

[Yao] Got it. The details of the definition and processing procedure will be added to the section.

[Yao] If the SFC is bi-directional, the SFC Basic Unit FEC Sub-TLV can be carried in TLV 16 for reverse SFP connectivity verification or in TLV 21 to carry the specified return SFP info to be used by the echo reply.  There are more details needed in this section as you said. I'll make it clearer.

The information

[Yao] OK, I will add the paragraph about the allocation in the next version and I believe that the sub-TLV should be allocated from range 0-16383, which is standards action.

/Loa

PS

[Yao] Thanks for reminding~ I'll go through the draft to learn more about it. 

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