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

From: Warren Kumari via Datatracker <[email-masked]>
Date: Wed, 01 Dec 2021 13:38:00 -0800

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

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COMMENT:
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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.