Re: [dhcwg] MPL config draft (Re: [Roll] I-D Action: draft-ietf-roll-mpl-parameter-configuration-01.txt)

Yusuke DOI <yusuke.doi@toshiba.co.jp> Tue, 08 July 2014 09:14 UTC

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Date: Tue, 08 Jul 2014 16:55:27 +0900
From: Yusuke DOI <yusuke.doi@toshiba.co.jp>
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To: Andre Kostur <akostur@incognito.com>
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Cc: "dhcwg@ietf.org" <dhcwg@ietf.org>, Routing Over Low power and Lossy networks <roll@ietf.org>
Subject: Re: [dhcwg] MPL config draft (Re: [Roll] I-D Action: draft-ietf-roll-mpl-parameter-configuration-01.txt)
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Hi Andre,

Thank you for the comments.

I think I need to explain background more.

1) Typical MAC we're expecting is 50k-200kbps mesh network with 5+ hops.
I think a compact option format is more suitable for the case.

2) A parameter set is bound for an MPL domain. A network may have
multiple MPL domains. I think it is much simpler to handle all
parameters as a set.

(2014-07-08 01:32), Andre Kostur wrote:
> A couple of quick thoughts (keeping in mind RFC 7227 - Guidelines for
> Creating New DHCPv6 Options):
>
> - An encoded option is frowned upon.  Split all of those into separate
> options, and the "Reserved" parts simply disappear.  A "sub-optioned"
> option is also frowned upon (section 9, RFC 7227).

As described above, the parameters are considered as a set. I could not
find recommended design for parameter sets. More than one parameter set
will be configured. To make them separated I think each option should be
with MPL domain (= IPv6 address).

> - Why add the additional complexity of the floating point?   Why not
> use a 32-bit unsigned integer representing milliseconds which gets you
> a little over 40 days?  Not the 18 weeks that you currently can
> represent, but is there a practical use for timers over a month long
> in MPL?

The motivation behind the floating point is to reduce message length as
much as possible. As MPL has 7 timers, it will reduce 14 bytes. Though,
usually 40 days should be enough and this is just a tradeoff (I'm not
insisting on the floating point format).

> - If you do go with separate options, consider what it would mean if
> certain options don't exist.  ietf-roll-trickle-mcast appears to
> define defaults, perhaps reference that draft to say that if an option
> is missing, the client is to use the default defined in that draft?

If the draft goes with separate options, I agree it should be the
default values.

> - Speaking of RFC 7227...  I-D.ietf-dhc-option-guidelines got published in May

Thank you.

Yusuke