Re: [Roll] [6tisch] Support of flow label to carry the RPL information in data packets

Pat Kinney <> Thu, 01 May 2014 16:39 UTC

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From: Pat Kinney <>
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Date: Thu, 1 May 2014 11:39:42 -0500
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Subject: Re: [Roll] [6tisch] Support of flow label to carry the RPL information in data packets
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Dear All;

Over the past 8 years ISA100 has been involved with wireless industrial networks using battery operated wireless modules that must last at least 10 years on a single battery.  Since these applications are typically low data rate (50 - 250 kb/s), and TDMA for low energy usage, these industrial networks use the IEEE 802.15.4 MAC/PHY standard.  Since industrial environments contain significant interference, using shorter packet durations significantly increase the likelihood of a successful message receipt, dramatically reducing retries which consume energy and reduce network throughput.
ISA100 worked with the IETF to allow ISA's first wireless standard, ISA100.11a that is now shipping, to use IPv6 with the 6LoWPAN header compression (RFC6282) at the network layer with a string critical requirement to keep the frame size minimal so as to stay under the 127 bytes limit as per the 802.15.4.  ISA100 would now like to consider a wireless industrial standard using the full 6TiSCH suite and in particular RPL (RFC 6550) and the backbone router technology; however using the RPL option in a Hop-by-Hop header as proposed in RFC6553 would add an additional 8 bytes to the packet.  Regretfully, this additional overhead can't be tolerated since it would result in security configuration packets (and others) being larger than the 127 byte limit. 
As a co-chair of ISA100 as well as the editor of ISA100.11a-2011, I would ask the IETF 6man to seriously consider adopting draft-thubert-6man-flow-label-for-rpl that combines optimally with RFC6282 for a minima overhead in the compressed packet. 

Pat Kinney
Kinney Consulting LLC
IEEE 802.15 WG vice chair, TG chair
ISA100.11a WG chair
O: +1.847.960.3715

On Apr 17, 2014, at 9:26 AM, Pascal Thubert (pthubert) <> wrote:

Dear all;
Considering the support we have at 6TiSCH and ROLL for the work, I published draft-thubert-6man-flow-label-for-rpl-00.txt to the 6MAN WG.
The main discussion is probably to confirm whether our proposed use of the flow label inside the RPL domain is compatible with the goals that are achieved by RFC6437. Let us continue the discussion there from now on.
From: [] On Behalf Of Xavier Vilajosana
Sent: jeudi 17 avril 2014 10:00
To: Ines Robles
Cc: Pascal Thubert (pthubert);; roll
Subject: Re: [6tisch] [Roll] Support of flow label to carry the RPL information in data packets
+1 I think this is more than needed. In addition RFC 6282 defines how header compression needs to be handled together with extension headers. I think this is not clear and leads to confusions (afecting already some wireshark dissectors). The use of flow label will solve several problems at once.

2014-04-16 22:44 GMT+02:00 Ines Robles <>om>:
2014-04-15 21:19 GMT-03:00 Qin Wang <>om>:
On Wednesday, April 16, 2014 1:47 AM, Prof. Diego Dujovne <> wrote:
+1 !

2014-04-15 12:25 GMT-03:00 Tom Phinney <>et>:
+1 for sure. The flow label has always been the preferable method for me, and I suspect for others with knowledge of how it is used in ISA100.11a.
On 2014.04.15 07:25, Pascal Thubert (pthubert) wrote:
Dear all:
As some of you remember, the RPL specification has changed over time WRT to the location of the information that RPL places in the data packets. We started with the flow label but these were the days when what became RFC 6437 was being defined at 6MAN, so we shied away and defined the HbH technique that is now specified as RFC 6553.
We’ll note that the RPL option defined in RFC 6553 takes 6 octets, and with the HbH hdr we end up with 8 extra octets. An extra IP-in-IP encapsulation is required on top of that unless both endpoints are in the same RPL domain. All this overhead may be acceptable when power is available and the PHY allows for larger frames, but in traditional battery-operated 15.4 with ~ 80 bytes usable per frame, my experience from integrating 6LoWPAN HC with ISA100.11a says that all these extra bytes will be on the way of the 6TiSCH adoption.
Still, both RFC 6550 and RFC 6552 are designed to allow for an alternate technique and in particular for the use of the flow label, as is elaborated in . Using the flow label reduces the cost of the RPL information dramatically, down to a level that is probably acceptable for the target SDOs.
So my plan for now is to move the flow label draft to 6MAN and prepare for a hot season, and I’m looking for support from both 6TiSCH and ROLL to back me up from the start.  Yes, you can help!
Please +1 if you agree we need this work to happen, and/or provide any suggestion.

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