Hi Gaoqiang,

Thanks a lot for your comments.

Co-authors will discuss those comments and feedback you soon.

 

B.R.

Weiqiang Cheng

 

发件人: Gaoqiangzhou [mailto:gaoqiangz...@huawei.com] 
发送时间: 2022年10月13日 14:19
收件人: draft-ietf-spring-srv6-srh-compress...@ietf.org
抄送: spring@ietf.org
主题: comments of CSID draft

 

Hello authors,

 

When implementing the C-SID mechanism defined in the draft, I find out
something is missing and something can be enhanced in the draft, so I
provide comments below.

 

1.      The pseudo code does not align with original drafts

・         NEXT-C-SID: in original draft [1], the node checks the
DA.Argument.next (the next C-SID in DA) instead of DA.argument in this
draft. 

・         REPLACE-C-SID: in original draft[2], the if node checks the
DA.Argument.SI instead of DA.argument in this draft.

We have implemented and deployed following the original draft, so It will be
better to align with the code. We think use DA.Argument.next and
DA.argument.SI is correct, easy for implementation and hardware friendly.

 

2.      The combined flavor pseudo code can be enhanced.  The current
version is too complicated, and not friendly for hardware implementation.
Actually, we can simply combine the pseudo code of NEXT-C-SID and
REPLACE-C-SID to make it very simple. This is the same way to combine
flavors such as PSP, USP and USD (to generate PSP&USP&USD).

 

              “Inserting the pseudo code of NEXT-C-SID flavor with
DA.Argument replaced by DA.Argument.Next between lines S01 and S02 of the
REPLACE-C-SID pseudo code. ”

 

When DA.Argument.Next is not 0, the endpoint node performs NEXT-C-SID
processing to shift the Argument to the left by the length of the C-SID. 

When the DA.Argument.Next is 0, the endpoint node performs REPLACE-C-SID
processing to replace the C-SID from Segment list to DA.   Doing this can
bring a lot of enhancement to the whole draft, and bring benefits to
implementation and deployment.

 

3.      For REPLACE-C-SID flavor, it will be good to check the next CSID is
0 or not before updating the CSID to the DA when SI > 0, so that we can
handle the processing error when the REPLACE-C-SID flavor SID is the last
C-SID in the CSID sequence. For example, when the SI >0 and next CSID is 0,
meaning the end of the CSID sequence, so update the next 128-bit SID to the
DA when SL >0, or stop processing when SL=0.

 

These are some enhancements of the C-SID mechanism I found in
implementation.  Hope we can update the draft to address the comments to
help implementation and inter-op test, thanks.

 

Best regards,

Qiangzhou

 

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