Re: [Roll] nsa extension comments

[Remous-Aris Koutsiamanis <[e-mail]>]

Hello Rahul,

thank you very much for the commens and editing.
We'll go through everything and update here.

Best,
Aris

On Sat, Dec 7, 2019 at 9:06 AM Rahul Jadhav <[e-mail]> wrote:

> Hello authors,
>
> I have pushed my PR[1] to the corresponding roll-wg repo.  However, there
> are other
> points which require your attention. Following are my comments:
>
> o Carrying TLVs in NSA
> RFC 6551 explains that an NSA can be used to carry TLVs but it falls short
> of
> specifying the format for these TLVs. This document assumes the format of
> 8-bit
> type and 8-bit length. This format is fine but future specifications will
> have
> to refer to this document if they got to add new TLVs. Thus the generic TLV
> format should be made part of different section and an IANA registry needs
> to
> be created for the NSA TLV type.
>
> o Preference in PS set
> The document assumes that the parent addresses in the PS set have been
> added in
> the decreasing order of preference, without making it explicit. The PS IPv6
> address(es) field requires an explanation in Section 4.
>
> o DIO length
> As per the draft, the DIO needs to carry NSA (Node State and Attributes)
> metric
> with PS (parent set) TLV. As per my understanding without compression, it
> would
> be a challenge to carry even two parent addresses in the PS. There has
> been a
> discussion about compression and as I remember we discussed doing it.
> Regardless, I feel we should do it if we want this to be a practical
> proposition.
>
> o Section 3.4 Usage:
> "For example, using different methods can be used to vary the transmission
> reliability in each hop."
> This statement implies that using different CA policy implementation can
> "control" the transmission reliability. As I understand, the strict policy
> is
> the best policy (in terms of all performance metrics), the nodes will go
> for
> other policy only when the strict policy cannot be used given their parent
> sets.
> The above statement implies that nodes may still go for a relaxed policy
> when
> strict can be used.
>
> o Configuration parameters
> The document specifies configuration parameters such as
> a. PARENT_SET_SIZE ... Not defined
> b. cur_ap_min_path_cost: How can the cur_ap_min_path_cost be equated with
> PARENT_SWITCH_THRESHOLD as mentioned in section 3.2.2
> c. MAX_PATH_COST: No definition for this.
> The parameters warrant a rationale and a default value. Also more
> importantly,
> is it required that different nodes use the same value and if not what
> could be
> the impact.
>
> o Terminology section
> Terminology section should explain Alternative Parent, Parent Set,
> Preferred
> Grand Parent.
>
> o Section realignment
> It is better to explain CA Strict/Medium/Relax policies before explaining
> the
> CAOF because as a reader one needs to be familiar with these policies
> before
> understanding the OF.
>
> Regards,
> Rahul
>
> [1] https://github.com/roll-wg/draft-ietf-roll-nsa-extension/pull/1
>
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