Subject: Re: [Roll] Working Group Last Call: draft-ietf-roll-protocols-survey-02

From: Ulrich Herberg <[email-masked]>
Date: Tue, 09 Dec 2008 21:19:10 +0000

Hi,

Unfortunately, I did not attend IETF in California, and in Minneapolis I
was attending the autoconf WG meeting, so I was absent in both ROLL
meetings.

I have some concerns about this document.

- I think that the set of criteria chosen for the evaluation is not
complete. As Thomas Clausen said, criteria like delivery ratio and path
length seem to be important in addition to control cost, as they can be
contradictory. I can design routing protocols with an extremely low
control cost, but with a very bad delivery ratio or a high path length.
As in most networks data traffic will take more bandwith than control
traffic, the selection of only "control cost" as criterion does not seem
to be fair. I understand that the authors do not claim to have presented
a complete set of criteria, but just a subset. However, many routing
protocols intentionally do a trade-off between control cost and delivery
ratio/path length, so just putting a "fail" for control cost does not
seem to be adequate for me.

- In the introduction, the authors state:

"this document simply seeks to answer the question: do LLNs require a
new protocol specification document at all?"

I cannot find an answer to that question. What is the conclusion of this
document? Yes, there is no routing protocol in the IETF that --
according to these evaluation criteria -- fulfills all requirements.
Does that mean that we need to rewrite routing protocols from the
scratch? Or just tweak existing protocols? What is the consequence of
this document? In what way does it help us to continue to work on
routing protocols for LLNs considering the limited set of routing
protocols and criteria selected in this ID?

Nits:
 - Section 3,
   "The five criteria, presented in Section 3"
Shouldn't that be section 4?
 - Section 1
  MANET: Mobile Ad-hoc Networks
I think that MANET is mostly used in singular, not in the plural
"networks" (see also your unnumbered section "Protocols Today")

Best regards,
Ulrich Herberg
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From: JP Vasseur <[email-masked]>
Date: Tue, 9 Dec 2008 22:47:57 +0100

Hi Ulrich,

> seem to be adequate for me.

Please bear in mind that the objective is not to look at all possible  
criterion but a required subset in light of the
four routing requirement documents produced by the WG.

> protocols and criteria selected in this ID?

Hopefully I answered these questions on the list today.

> "networks" (see also your unnumbered section "Protocols Today")

Thanks.

JP.