Re: [6tisch] Handling Inconsistent Allocation in 6P

[Thomas Watteyne]

I'd like to keep 6P simple, and just have a mechanism to detect
inconsistencies. I believe roll-back to a previous schedule generation adds
too much complexity. From an implementation point of view, cells that are
in the process of being reserved (i.e. 6P add request sent but no response
received yet) should be marked as "reserved" and only committed to the
schedule once the 6P transaction if over. I believe this captures Nicola's
idea, but turning it into a recommendation for implementers, rather than a
protocol feature.

On Mon, Nov 21, 2016 at 9:56 PM, Xavi Vilajosana Guillen <
xvilajos...@uoc.edu> wrote:

> Hi Yatch,
> my 2 cents inline
>
>
>> I've been thinking about how to handle inconsistencies. I know the
>> current draft has an inconsistency detection mechanism with generation
>> management; just wondering if there is another way or a supplemental
>> mechanism to deal with such a situation.
>>
>> We decided at the IETF meeting last week to reduce the number of
> generation counters from 2 to 1 (2bits field) as now 6P commands can add
> different types of cells so we need to account for transactions now. I
> state that here to outline that the proposed mechanism is very simple. At
> every transaction we increment a generation counter. It cannot happen that
> the two sides of the transaction have inconsistent counters. If this
> happens, then the schedules are reset. I agree that this is detected after
> the error has occurred.
>
>
>> I thought that the 2-phase commit (2PC) protocol could be useful
>> here. Then, I found the nice idea by Nicola in the ML archive. In
>> terms of the 2PC protocol, 6P ACK is Commit. 6P NACK (mentioned in
>> another email by Nicola) is Abort or Rollback.
>> # We may need another type of message to acknowledge Commit or Abort.
>>
>> An advantage of this approach is that 6P can resolve an inconsistency
>> when it occurs at the least cost, by cancelling the concerned
>> operation alone. An apparent disadvantage is adding further complexity
>> to 6P.
>>
>
> it adds complexity and more messages over the air, which are costly and
> can also fail (e.g external interference). What happens if we loose the 6P
> NACK? How the NACK sender know that the NACK has been received?
>
>>
>> What others think...?
>>
>
> I like to answer with another question. What causes less overhead, 2 bits
> per each 6P command or 1 or 2 extra packets per transaction (assuming only
> write/state modification transactions). For me the former is way simpler.
>
> regards,
> X
>
>
>
>>
>> Best,
>> Yatch
>>
>> ___
>> 6tisch mailing list
>> 6tisch@ietf.org
>> https://www.ietf.org/mailman/listinfo/6tisch
>>
>
>
>
> --
> Dr. Xavier Vilajosana Guillén­
> Research Professor
> Wireless Networks Research Group
> Internet Interdisciplinary Institute (IN3)
> Universitat Oberta de Catalunya­
>
> +34 646 633 681| xvilajos...@uoc.edu­ | Skype­: xvilajosana
> http://xvilajosana.org
> http://wine.rdi.uoc.edu/
>
> Parc Mediterrani de la Tecnologia
> Av. Carl Friedrich Gauss, 5. Edifici B3
> 08860 Castelldefels (Barcelona)
>
>
>
> ­
>
> ___
> 6tisch mailing list
> 6tisch@ietf.org
> https://www.ietf.org/mailman/listinfo/6tisch
>
>


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___

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Sr Networking Design Eng, Linear Tech
Founder & co-lead, UC Berkeley OpenWSN
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[6tisch] [6P+SF0] CALL FOR CONSENSUS: sending a CLEAR request to old parents

[Thomas Watteyne]

In thread "Node Behavior at Boot in SF0" (
https://www.ietf.org/mail-archive/web/6tisch/current/msg04883.html), we
ended up discussing the following paragraph

https://tools.ietf.org/html/draft-ietf-6tisch-6top-sf0-02#section-10:

   In order to define a known state after the node is restarted, a CLEAR
   command is issued to each of the neighbor nodes to enable a new
   allocation process.  The 6P Initial Timeout Value provided by SF0
   should allow for the maximum number of TSCH link-layer retries, as
   defined by Section 4.3.4 of [I-D.ietf-6tisch-6top-protocol].  TODO/
   REMARK: The initial timeout is currently under discussion.

The suggestion on the table is to:

step 1. Change
https://tools.ietf.org/html/draft-ietf-6tisch-6top-sf0-02#section-10 to:

   The 6P Initial Timeout Value provided by SF0
   should allow for the maximum number of TSCH link-layer retries, as
   defined by Section 4.3.4 of [I-D.ietf-6tisch-6top-protocol].  TODO/
   REMARK: The initial timeout is currently under discussion.

step 2. Add the following text to draft-ietf-6tisch-6top-protocol, by
possibly adding a 4.3.X section:

4.3.X. Disconnecting from a neighbor

   If the SF realizes connection to a particular neighbor is no longer
   needed (for example a change in parent by the routing protocol),
   the SF MAY send a CLEAR request to that neighbor to speed up the
   cleanup process of the cells allocated with that neighbor.

I'm hereby opening a call for WG consensus. Please +1 or comment/suggest.
The chairs will summarize on Fridat 25 Nov.

Thomas

-- 
___

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Sr Networking Design Eng, Linear Tech
Founder & co-lead, UC Berkeley OpenWSN
Co-chair, IETF 6TiSCH

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Re: [6tisch] [6TiSCH] Node Behavior at Boot in SF0

[Thomas Watteyne]

Yatch,
Agreed. Let's me start a different thread where I summarize your suggestion
and ask for WG consensus.
Thomas

On Mon, Nov 21, 2016 at 5:10 PM, Michael Richardson 
wrote:

>
> Yasuyuki Tanaka  wrote:
> >> Sending an explicit CLEAR will speed things up, and avoid for the
> >> previous preferred parent to waste energy listening to those. A
> CLEAR
> >> wouldn't hurt, right?
>
> > This is right. But, I don't think it's a SF0 job. The thing is that
> SF0
> > knows nothing about RPL.
>
> > If SF0 provided an API to send CLEAR to a particular neighbor, RPL
> > could trigger the CLEAR request to a previous preferred parent on its
> > parent switch, I guess.
>
> Your SF0 layer could provide whatever internal API it wants to your RPL
> implementation.  This is hardly a standardization issue or problem; this
> is a
> quality of implementation issue.
>
> The observation of *when* RPL should clear traffic reservation may have
> some
> impact on the SF0 protocol, but I'd think it would be just some
> implementation advice.
>
>
> --
> Michael Richardson , Sandelman Software Works
>  -= IPv6 IoT consulting =-
>
>
>
>
> ___
> 6tisch mailing list
> 6tisch@ietf.org
> https://www.ietf.org/mailman/listinfo/6tisch
>
>


-- 
___

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Research Scientist & Innovator, Inria
Sr Networking Design Eng, Linear Tech
Founder & co-lead, UC Berkeley OpenWSN
Co-chair, IETF 6TiSCH

www.thomaswatteyne.com
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Re: [6tisch] Handling Inconsistent Allocation in 6P

[Xavi Vilajosana Guillen]

Hi Yatch,
my 2 cents inline


> I've been thinking about how to handle inconsistencies. I know the
> current draft has an inconsistency detection mechanism with generation
> management; just wondering if there is another way or a supplemental
> mechanism to deal with such a situation.
>
> We decided at the IETF meeting last week to reduce the number of
generation counters from 2 to 1 (2bits field) as now 6P commands can add
different types of cells so we need to account for transactions now. I
state that here to outline that the proposed mechanism is very simple. At
every transaction we increment a generation counter. It cannot happen that
the two sides of the transaction have inconsistent counters. If this
happens, then the schedules are reset. I agree that this is detected after
the error has occurred.


> I thought that the 2-phase commit (2PC) protocol could be useful
> here. Then, I found the nice idea by Nicola in the ML archive. In
> terms of the 2PC protocol, 6P ACK is Commit. 6P NACK (mentioned in
> another email by Nicola) is Abort or Rollback.
> # We may need another type of message to acknowledge Commit or Abort.
>
> An advantage of this approach is that 6P can resolve an inconsistency
> when it occurs at the least cost, by cancelling the concerned
> operation alone. An apparent disadvantage is adding further complexity
> to 6P.
>

it adds complexity and more messages over the air, which are costly and can
also fail (e.g external interference). What happens if we loose the 6P
NACK? How the NACK sender know that the NACK has been received?

>
> What others think...?
>

I like to answer with another question. What causes less overhead, 2 bits
per each 6P command or 1 or 2 extra packets per transaction (assuming only
write/state modification transactions). For me the former is way simpler.

regards,
X



>
> Best,
> Yatch
>
> ___
> 6tisch mailing list
> 6tisch@ietf.org
> https://www.ietf.org/mailman/listinfo/6tisch
>



-- 
Dr. Xavier Vilajosana Guillén­
Research Professor
Wireless Networks Research Group
Internet Interdisciplinary Institute (IN3)
Universitat Oberta de Catalunya­

+34 646 633 681| xvilajos...@uoc.edu­ | Skype­: xvilajosana
http://xvilajosana.org
http://wine.rdi.uoc.edu/

Parc Mediterrani de la Tecnologia
Av. Carl Friedrich Gauss, 5. Edifici B3
08860 Castelldefels (Barcelona)



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Re: [6tisch] [6TiSCH] Node Behavior at Boot in SF0

[Michael Richardson]

Yasuyuki Tanaka  wrote:
>> Sending an explicit CLEAR will speed things up, and avoid for the
>> previous preferred parent to waste energy listening to those. A CLEAR
>> wouldn't hurt, right?

> This is right. But, I don't think it's a SF0 job. The thing is that SF0
> knows nothing about RPL.

> If SF0 provided an API to send CLEAR to a particular neighbor, RPL
> could trigger the CLEAR request to a previous preferred parent on its
> parent switch, I guess.

Your SF0 layer could provide whatever internal API it wants to your RPL
implementation.  This is hardly a standardization issue or problem; this is a
quality of implementation issue.

The observation of *when* RPL should clear traffic reservation may have some
impact on the SF0 protocol, but I'd think it would be just some
implementation advice.


--
Michael Richardson , Sandelman Software Works
 -= IPv6 IoT consulting =-





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Re: [6tisch] [Anima] 6tisch security bi-weekly meetings

[Michael Richardson]

peter van der Stok  wrote:
> which meeting do you want me to join?

You are welcome at both. The 6tisch is probably more important in some ways,
The EST/CoAP discussion will be easier to have in the anima group.

(I will post to ace about that this week)

--
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 -= IPv6 IoT consulting =-





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Re: [6tisch] [6TiSCH] Node Behavior at Boot in SF0

[Yasuyuki Tanaka]

Hi Thomas,


Could we say something to the effect that, if SF0 realizes
connection to a particular neighbor is no longer needed (for example
a change in parent by the routing protocol) SF0 MAY send CLEAR
requests to neighbor to speed up the cleanup process of the cells
with that neighbors?


I guess so. I would say it's a use-case description for CLEAR. To me,
it seems the 6P draft is a right place to add something as you
suggested. In that sense, "SF0" in the text above could be replaced
with "SF", anonymous one:

   If a SF realizes connection to a particular neighbor is no longer
   needed (for example a change in parent by the routing protocol),
   the SF MAY send CLEAR requests to the neighbor to speed up the
   cleanup process of the cells with that neighbors.

# Honestly, I'm not sure what "with that neighbors" suggested...

By the way, the API thing I mentioned is a hypothetical scenario; I
respect the "minimal" nature of SF0. :-)

Best,
Yatch

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Re: [6tisch] [6TiSCH] Node Behavior at Boot in SF0

[Thomas Watteyne]

Yatch,

Hmm, good point. I'm with you that have SF0 be independent from higher
layer stuff is the right design approach.

But SF0 doesn't really offer any API for upper-layers (it would be against
its "minimal" nature). Could we say something to the effect that, if SF0
realizes connection to a particular neighbor is no longer needed (for
example a change in parent by the routing protocol) SF0 MAY send CLEAR
requests to neighbor to speed up the cleanup process of the cells with that
neighbors?

Thomas

On Mon, Nov 21, 2016 at 1:08 PM, Yasuyuki Tanaka <
yasuyuki9.tan...@toshiba.co.jp> wrote:

> Hi Thomas,
>
> Sending an explicit CLEAR will speed things up, and avoid for the
>> previous preferred parent to waste energy listening to those. A
>> CLEAR wouldn't hurt, right?
>>
>
> This is right. But, I don't think it's a SF0 job. The thing is that
> SF0 knows nothing about RPL.
>
> If SF0 provided an API to send CLEAR to a particular neighbor, RPL
> could trigger the CLEAR request to a previous preferred parent on its
> parent switch, I guess.
>
> Best,
> Yatch
>
>


-- 
___

Thomas Watteyne, PhD
Research Scientist & Innovator, Inria
Sr Networking Design Eng, Linear Tech
Founder & co-lead, UC Berkeley OpenWSN
Co-chair, IETF 6TiSCH

www.thomaswatteyne.com
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[6tisch] Thomas' review of draft-richardson-6lo-ra-in-ie-00

[Thomas Watteyne]

Michael, all,

Please find below my review of draft-richardson-6lo-ra-in-ie-00.
Since interesting for both 6lo and 6TISCH, sending to both MLs.

Typos fixed directly in line (please use diff), discussion points started
at newline with "TW>" prefix.

Since short draft, send review in body directly.

Thomas



6lo Working Group  M. Richardson
Internet-Draft  Sandelman Software Works
Intended status: Informational  October 18, 2016
Expires: April 21, 2017


 802.15.4 Informational Element encapsulation of ICMPv6 Router
 Advertisements
draft-richardson-6lo-ra-in-ie-00

Abstract

   In TSCH mode of 802.15.4, as described by [I-D.ietf-6tisch-minimal],
TW> I would suggest to use "IEEE802.15.4" everywhere, just to be ultra clear
   opportunities for broadcasts are limited to specific times and
   specific channels.  An enhanced beacon must be broadcast periodically
   by every router to keep all nodes in sync.
TW> I would rephrase the last sentence to "Nodes in a TSCH network
typically frequently send Enhanced Beacon (EB) frames to announce the
presence of the network"
   This document provides a
   mechanism by which other small ICMPv6 packets, such as Router
   Advertisements may be carried within the Enhanced Beacon,
TW> why not simply talk about RAs rather than "other small... such as..."
   providing
   standard IPv6 router/host protocol.
TW> "providing standard IPv6 router/host protocol." word missing?

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 21, 2017.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



Richardson   Expires April 21, 2017 [Page 1]
Internet-DraftIE for ICMPv6 October 2016


   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
 1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   2
 1.2.  Layer-2 Synchronization . . . . . . . . . . . . . . . . .   2
 1.3.  Layer-3 synchronization IPv6 Router solicitations and
   advertisements  . . . . . . . . . . . . . . . . . . . . .   3
   2.  Protocol Definition . . . . . . . . . . . . . . . . . . . . .   3
 2.1.  Protocol Example  . . . . . . . . . . . . . . . . . . . .   4
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
 5.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
 5.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Appendix A.  appendix . . . . . . . . . . . . . . . . . . . . . .   8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   [I-D.ietf-6tisch-architecture] describes the use of the time-slotted
   channel hopping (TSCH) mode of [ieee802154].
TW> I would cite RFC7554 instead, which specifically describes TSCH
   As further detailed in
   [I-D.ietf-6tisch-minimal], an Extended Beacon is transmitted during a
   slot designated as broadcast slot.

   EDNOTE: Explain why broadcasts are rare, and why we need them.  What
   the Enhanced Beacon is, and what Information Elements are, and how
   the IETF has a subtype for that area.  Explain what kind of things
   could be placed in Information Elements, how big they could be, and
   how they could be compressed.

1.1.  Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
   

Re: [6tisch] macLinkType for the minimal configuration (draft-ietf-6tisch-minimal-16)

[Tero Kivinen]

Xavi Vilajosana Guillen writes:
> We discussed this. We said to use NORMAL in order to support any type of
> packet in the minimal cell/s and not only EBs. From our discussions, I think
> that we all understood (at least is what I captured in the minimal text) that
> if the type is NORMAL we can also send EBs there and hence we discarded
> ADVERTISEMENT type. 

I would disagree with that.

Note, that LinkType of ADVERTISING and NORMAL are local matters, they
are never transmitted over air, and there is not bits for them in the
IEs.

The section 8.2.19.3 MLME-SET-LINK.request of 802.15.4-2015 says:

LinkType Enumeration ADVERTISING,   Set to ADVERTISING if the link
 NORMAL is to be used to advertise the
network, otherwise set to NORMAL. 

And:

If LinkType is set to ADVERTISE, the links may be used to send
Enhanced Beacon frames as the result of the MAC receiving a
MLME-BEACON.request.

Then in section "6.3.6 TSCH PAN formation" the text talks about the
"advertising device":

A TSCH PAN is formed when a device, referred to as an
advertising device, advertises the presence of the network by
sending Enhanced Beacon frames upon receipt of a
MLME-BEACON.request from a higher layer. In a TSCH PAN the
Enhanced Beacon frames contain the following IEs:

...

My understanding is that the fact that LinkType is set to ADVERTISING
indicates that specific link is used to send Enhanced Beacons out,
i.e. it is used to advertise the network compared to the other tx
links, which are not used to advertise network, but which are used for
normal traffic in the network.

The ADVERTISING link can also be used to send normal traffic on it,
and it may be used to send Enhanced Beacons after the higher layer
calls MLME-BEACON.request. I.e., MAC layer somehow needs to know which
link it should be using to send beacons out, and ADVERTISING LinkType
tells that to the MAC level. I also assume that the same link is also
used to send periodic Enhanced Beacons, altough I do not think that is
specified anywhere in the 802.15.4-2015.

I do not know what the MAC level does if none of the links are set to
ADVERTISING and higher layer calls MLME-BEACON.request. It might wait
for the next ADVERTISING link, and not finding them it would not send
the EB out ever.

So I think the LinkType for the minimal should be set as ADVERTISING,
so it can will be used to send EBs and other traffic out.

> A clarification of these will be really valuable now that I will
> proceed with the revision of minimal.
-- 
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Re: [6tisch] [6TiSCH] Node Behavior at Boot in SF0

[Yasuyuki Tanaka]

Hi Thomas,


Sending an explicit CLEAR will speed things up, and avoid for the
previous preferred parent to waste energy listening to those. A
CLEAR wouldn't hurt, right?


This is right. But, I don't think it's a SF0 job. The thing is that
SF0 knows nothing about RPL.

If SF0 provided an API to send CLEAR to a particular neighbor, RPL
could trigger the CLEAR request to a previous preferred parent on its
parent switch, I guess.

Best,
Yatch

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Re: [6tisch] [Anima] 6tisch security bi-weekly meetings

[peter van der Stok]

Hi Michael,

which meeting do you want me to join?

Peter

Michael Richardson schreef op 2016-11-18 04:30:

The 6tisch security design team will meet every two weeks starting on
November 29th at 14:00 UTC.  The meeting is anchored to UTC, not EST, 
but

that will matter only in March.

The nov. 29th meeting will be devoted to:
a) recap of IETF97; work ensuing from the meeting.
b) 6tisch-minimal-security




Tuesday, November 29, 2016
9:00 am Eastern Standard Time (GMT-05:00)
Recurrence: Every 2 weeks on Tuesday, from Tuesday, November 29, 2016, 
to

   Tuesday, March 21, 2017

Meeting number: 641 335 839
Meeting password: pledge
Meeting link:
   
https://ietf.webex.com/ietf/j.php?MTID=me98f12cebda5e6b55c1b8c66c095d0a9

Host key: 587716

Audio connection:
1-877-668-4493 Call-in toll free number (US/Canada)
1-650-479-3208 Call-in toll number (US/Canada)


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