Re: [Roll] Use of flow-label in RPL (LLN) networks

Philip Levis <> Fri, 26 September 2014 17:19 UTC

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Date: Fri, 26 Sep 2014 10:19:08 -0700
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Subject: Re: [Roll] Use of flow-label in RPL (LLN) networks
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On Sep 12, 2014, at 6:42 AM, Michael Richardson <> wrote:

> There are two paths for forward (perhaps more): 
>  A. adopt draft-thubert-6man-flow-label-for-rpl, incorporate 6man feedback,
>     publish (perhaps add to ROLL milestones) 
>  B. create a 6man-flow-label considerations in LLNs document, taking just
>     the issues about resetting flowlabel to zero, and negotiate who (6lo vs
>     ROLL) will adopt draft-bormann-6lo-rpl-mesh 

B is a better approach. draft-bormann-6lo-rpl-mesh does not require any updates, changes, notes, or deviations to RFC6437. I originally said that I thought the reasoning behind draft-thubert-6man-flow-label-for-rpl (improved energy efficiency due to reduced header overheads) was sufficient to warrant a second case in which the flow label was not preserved end-to-end. But that was under the assumption that we had to twiddle with the flow label in this way. If we can achieve the same goals without doing so, that is a technically superior solution.

In short, draft-bormann-6lo-rpl-mesh is more efficient (uses fewer bits) than draft-thubert-6man-flow-label-for-rpl. Furthermore, unlike draft-thubert-6man-flow-label-for-rpl it complies with RFC6437 and requires no exceptions.

I understand that there is a sense of time pressure here, but I think that, in the context of standards, expediency is not a good motivation for decision making. I.e., it's better to have a better standard that will stick and become the solid technical basis for decades to come, rather than get something out quick that we'll have to redo.