[sfc] Warren Kumari's No Objection on draft-ietf-sfc-nsh-tlv-09: (with COMMENT)

[Warren Kumari via Datatracker <[e-mail]>]

Warren Kumari has entered the following ballot position for
draft-ietf-sfc-nsh-tlv-09: No Objection

When responding, please keep the subject line intact and reply to all
email addresses included in the To and CC lines. (Feel free to cut this
introductory paragraph, however.)


Please refer to https://www.ietf.org/blog/handling-iesg-ballot-positions/
for more information about how to handle DISCUSS and COMMENT positions.


The document, along with other ballot positions, can be found here:
https://datatracker.ietf.org/doc/draft-ietf-sfc-nsh-tlv/



----------------------------------------------------------------------
COMMENT:
----------------------------------------------------------------------

I had started writing this as a DISCUSS position, mainly about the lack of
Security Considerations and lack of context / detail around fields, but changed
to NoObj because the SecADs are already holding the DISCUESSes, and the fields
*can* be figured out with sufficient effort. For future documents, it would be
really helpful to have some more information / detail.

As an example:
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Metadata Class = 0x0000    |  Type = TBA4  |U| Length = var|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                     Source Interface                          ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 10: Ingress Network Source Interface

   The fields are described as follows:
      Length: Indicates the length of the Source Interface in bytes (see
      Section 2.5.1 of [RFC8300]).
      Source Interface: Identifier of the ingress interface of the
      ingress network node."

Erm, what format is the Source Interface in? Is "XE-0/0/0.23" an option? What
do I *do* with this?! Only after rereading the section multiple times and then
hunting down some other SFC documents did I notice the text above the document
which says: "This is an opaque quantity to the NSH." -- Ok, fair enough (yes,
I'm dumb for not having noticed that in the intro, but this is just an example
of a common thread in the document)

A "good" example is:
"Node ID: Represents an opaque value of the ingress network node
      ID.  The structure and semantics of this field are deployment
      specific.  For example, Node ID may be a 4 bytes IPv4 address Node
      ID, or a 16 bytes IPv6 address Node ID, or a 6 bytes MAC address,
      or 8 bytes MAC address (EUI-64), etc,." -- this explains what goes in the
      field, and a helpful example to situate the reader.