Re: [spring] WGLC - draft-ietf-spring-srv6-network-programming

["Pablo Camarillo (pcamaril)" <[e-mail]>]

Hi Greg,

Inline.

Thanks,
Pablo.

From: Greg Mirsky <[e-mail]>
Date: Tuesday, 7 January 2020 at 21:01
To: Bruno Decraene <[e-mail]>
Cc: SPRING WG List <[e-mail]>, "[e-mail]" <[e-mail]>, draft-ietf-spring-srv6-network-programming <[e-mail]>
Subject: Re: WGLC - draft-ietf-spring-srv6-network-programming
Resent from: <[e-mail]>
Resent to: <[e-mail]>, <[e-mail]>, <[e-mail]>, <[e-mail]>, <[e-mail]>, <[e-mail]>
Resent date: Tuesday, 7 January 2020 at 21:01

Dear Authors, WG Chairs, et al.,
I hope I'm not too late with my comments and questions on the document. Please kindly consider them as WG LC comments:
·         I have a question regarding the following pseudo-code:
  S08.   max_LE = (Hdr Ext Len / 2) - 1
  S09.   If ((Last Entry > max_LE) or (Segments Left > (Last Entry+1)) {
  S10.      Send an ICMP Parameter Problem to the Source Address,
               Code 0 (Erroneous header field encountered),
               Pointer set to the Segments Left field.
               Interrupt packet processing and discard the packet.
  S11.   }

According to RFC 8200, Hdr Ext Len is the length of the extension header in 8-octet units, not including the first 8 octets. Thus, as I understand, max_LE is the length in 8-octet units of half of the extension header less one. On the other hand, Last Entry and Segments Left are indices. Hence my question, What is being compared in line S09 ( Last Entry > max_LE)? Length and index? If the goal is to use Hdr Ext Len to calculate the number of entries in the header, then what assumption is used in S08? Is it that the entry's length is always and only 128 bits, i.e. 16 octets? I believe that using such an assumption is too narrowing and limiting to SRH.

PC: This has already been discussed with Adrian. Please check this thread: https://mailarchive.ietf.org/arch/msg/spring/IOA_4nlNPacD2v7Jue2dkGeOABk

·         Another question is to Section 6.3. What value do you see in this section? I've noticed that draft-ietf-6man-spring-srv6-oam is in the Informational References section. I agree with that for the first sentence in the section. But I believe that the second sentence that refers to the new O-bit and OAM behaviors defined in  draft-ietf-6man-spring-srv6-oam requires it to be moved into the Normative References section. Unless you'll decide to remove the section altogether.
PC: The O-bit and OAM behaviors described in draft-ietf-6man-spring-srv6-oam are not required to understand or implement the technology described in draft-ietf-spring-srv6-network-programming. However, they are relevant as to provide additional information to the reader. Why would it be a normative reference?

Regards,
Greg

On Thu, Dec 5, 2019 at 9:15 AM <[e-mail]<mailto:[e-mail]>> wrote:

Hello SPRING,



This email starts a two weeks Working Group Last Call on draft-ietf-spring-srv6-network-programming [1].



Please read this document if you haven't read the most recent version, and send your comments to the SPRING WG list, no later than December 20.



You may copy the 6MAN WG for IPv6 related comment, but consider not duplicating emails on the 6MAN mailing list for the comments which are only spring specifics.



If you are raising a point which you expect will be specifically debated on the mailing list, consider using a specific email/thread for this point.

This may help avoiding that the thread become specific to this point and that other points get forgotten (or that the thread get converted into parallel independent discussions)



Thank you,

Bruno



[1] https://tools.ietf.org/html/draft-ietf-spring-srv6-network-programming-05




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