Subject: [6lo] Thomas' review of draft-richardson-6lo-ra-in-ie-00

From: Thomas Watteyne <[email-masked]>
Date: Mon, 21 Nov 2016 14:13:28 +0100

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

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   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
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   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",
   and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119
   [RFC2119] and indicate requirement levels for compliant STuPiD
   implementations.

1.2.  Layer-2 Synchronization

   As explained in Section 6 of [I-D.ietf-6tisch-minimal], the Enhanced
   Beacon has a number of purposes: synchronization of ASN and Join
   Metric, timeslot template identifier, channel hopping sequence
   identifier, container for minimal slotframe/cell configuration.

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TW> I have completely rewritten the paragraph below
The Enhanced Beacon (EB) is used by nodes already part of a TSCH network to
annouce its existance.
Receiving an EB allows a Joining Node (pledge) to learn about the network
and synchronize to it.
The EB may also be used as a means for a node already part of the network
to re-synchronize [RFC7554].

EBs are sent on broadcast slots.
   There are a limited number of timeslots designated as a broadcast
   slot by each router.  These slots are rare, and with 10ms slots and
   a slotframe length of 100 slots, there may be as little as 1 slot per
second
   available to send the EB on.

1.3.  Layer-3 synchronization IPv6 Router Solicitations and
      Advertisements

   At layer 3, [RFC2461] defines a mechanism by which nodes learn about
   routers by listening for multicast Router Advertisements (RA).  If
   no RA is heard within a set time, a Router Solicitation (RS) may
   be multicast, to which an RA will be received, usually unicast.

   Although [RFC6775] reduces the amount of multicast necessary to do
   address resolution via Neighbor Solicitation messages, it still
   requires multicast of either RAs or RSs.  This is an expensive
   operation for two reasons: in the TSCH context, there are few multicast
timeslots for
   unsolicited RAs; if a pledge node does not hear an RA, and decides to
   send a RS (consuming a broadcast aloha slot with unencrypted
   traffic), many unicast RS may be sent in response.

   This is a particularly acute issue for the 6TiSCH join process for the
   following reasons:

   1.  Use of a multicast slot by even a non-malicious unauthenticated
       node for a Router Solicitation may overwhelm that time slot.

   2.  It may require many seconds of on-time before a new pledge hears
       a Router Solicitation it can use.

   3.  A new pledge may listen to many Enhanced Beacons before it can
       pick an appropriate network and/or closest Join Assistant to
       attach to.  If it must listen for a RS as well as find the
       Enhanced Beacon, then the process may take a very long time.

2.  Protocol Definition

   [I-D.kivinen-802-15-ie] creates a registry for new IETF IE subtypes.
   This document allocates a new subtype TBD-XXX.

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   The base IE subtype structure is as follows.  As explained in
   [I-D.kivinen-802-15-ie] the length of the Sub-Type Content can be
   calculated.

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   TBD-XXX     |       6LoRH encoded structure                 |
   +-+-+-+-+-+-+-+-+                                               |
   ~                       Sub-Type Content                        ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

TW> I'm missing some text here which explains what is being proposed.
TW> It's clear at this point what IEs and RAs are, and I was expecting some
text which says, basically
TW> "and we want to transport RAs in IEs, in some compressed format, and
here is the proposed format"
TW> The remainder of my remarks relate to this: I'm a confused at this
point of the reading what it is you are trying to accomplish.

   Inside the Sub-Type content should be placed compressed packets
   according to [RFC6282] (as updated by
   [I-D.ietf-6lo-dispatch-iana-registry].

2.1.  Protocol Example

TW> I assume that by "Typically", you mean "in the unconstrained IPv6 case"
   Typically, a Router Advertisement is placed inside the Sub-Type.
TW> Sub-Type of what?
   The entire structure typically looks like:

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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Ver  6 | TC = 0        |           Flow Label = 0              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Payload Length        |  NH = 58      | Hop Lmt = 1   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                         Source Address                        +
   |                           fe80::LL                            |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                      Destination Address                      +
   |                           fe02::1                             |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Type = 134   |  Code = 0     |          Checksum             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | HL = 0        |0|0|  Reserved |  Router lifetime = 9000       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Reachable Time   = 0  XXX             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Retrans Timer   = 0  XXX             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Type = 1      | Len = 10      |    EUI-64 of router           |
   +-+-+-+-+-+-+-+-+-+-+-+---------+                               +
   |                    EUI-64 of router                           |
   +                               +---------------+---------------+
   | EUI-64 of router              | Type = TBD-YYY|  Len = 18     |
   +-------------------------------+-------------------------------+
   |                             DODAGID                           |
   +                                                               |
   |                                                               |
   +                                                               |
   |                                                               |
   +                                                               |
   |                                                               |
   +---------------------------------------------------------------+

TW> Not clear at this point what IPv6 Neighbor Discovery Option TBD-YYY
refers to

   When compressed by [RFC6282], this becomes:

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   +---------------------------------------------------------------+
   | 0 | 1 | 1 |TF= 11 |NH |HLIM=01|CID|SAC|  SAM  | M |DAC|  DAM  | 0
   +   |   |   |       | 0 |       | 0 | 0 | 0   1 + 1 + 0 + 1   1 +
   +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   | NH = 0x58                     |   dstXX = 0x01                | 4
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Type = 134   |  Code = 0     |          Checksum             | 8
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | HL = 0        |0|0|  Reserved |  Router lifetime = 9000       | 12
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Reachable Time   = 0  XXX             | 16
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Retrans Timer   = 0  XXX             | 20
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Type = 1      | Len = 10      |    EUI-64 of router           | 24
   +-+-+-+-+-+-+-+-+-+-+-+---------+                               +
   |                    EUI-64 of router                           | 28
   +                               +---------------+---------------+
   | EUI-64 of router              | Type = TBD-YYY|  Len = 18     | 32
   +-------------------------------+-------------------------------+
   |                             DODAGID                           | 36
   +                                                               |
   |                                                               | 40
   +                                                               |
   |                                                               | 44
   +                                                               |
   |                                                               | 48
   +---------------------------------------------------------------+

TW> but this is simply the 4944/6282 compression of it, right? I don't see
any IEs here.

   The total number of bytes needed is 56 bytes.

3.  Security Considerations

   TBD.

4.  IANA Considerations

   Allocate a new number TBD-XXX from Registry IETF IE Sub-type ID.
   This entry should be called 6LoRH-in-IE.
TW> 6LoRH-in-IE or RA-in-IE?

   Allocate a new number TBD-YYY from Neighbor Discovery Option Types
   (RFC2461) with the name   "Constrained Network Identification".
TW> not sure what this refers to

5.  References

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5.1.  Normative References

   [I-D.ietf-6lo-dispatch-iana-registry]
              Chakrabarti, S., Montenegro, G., Droms, R., and j.
              woodyatt, "6lowpan ESC Dispatch Code Points and
              Guidelines", draft-ietf-6lo-dispatch-iana-registry-05
              (work in progress), September 2016.

   [I-D.ietf-6tisch-architecture]
              Thubert, P., "An Architecture for IPv6 over the TSCH mode
              of IEEE 802.15.4", draft-ietf-6tisch-architecture-10 (work
              in progress), June 2016.

   [I-D.ietf-6tisch-minimal]
              Vilajosana, X. and K. Pister, "Minimal 6TiSCH
              Configuration", draft-ietf-6tisch-minimal-16 (work in
              progress), June 2016.

   [I-D.kivinen-802-15-ie]
              Kivinen, T. and P. Kinney, "IEEE 802.15.4 Information
              Element for IETF", draft-kivinen-802-15-ie-03 (work in
              progress), October 2016.

   [ieee802154]
              IEEE Standard, ., "802.15.4-2015 - IEEE Standard for Low-
              Rate Wireless Personal Area Networks (WPANs)", 2015,
              <http://standards.ieee.org/findstds/
              standard/802.15.4-2015.html>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC2461]  Narten, T., Nordmark, E., and W. Simpson, "Neighbor
              Discovery for IP Version 6 (IPv6)", RFC 2461,
              DOI 10.17487/RFC2461, December 1998,
              <http://www.rfc-editor.org/info/rfc2461>.

   [RFC6282]  Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
              Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
              DOI 10.17487/RFC6282, September 2011,
              <http://www.rfc-editor.org/info/rfc6282>.

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   [RFC6775]  Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
              Bormann, "Neighbor Discovery Optimization for IPv6 over
              Low-Power Wireless Personal Area Networks (6LoWPANs)",
              RFC 6775, DOI 10.17487/RFC6775, November 2012,
              <http://www.rfc-editor.org/info/rfc6775>.

   [RFC7228]  Bormann, C., Ersue, M., and A. Keranen, "Terminology for
              Constrained-Node Networks", RFC 7228,
              DOI 10.17487/RFC7228, May 2014,
              <http://www.rfc-editor.org/info/rfc7228>.

5.2.  Informative References

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
              December 1998, <http://www.rfc-editor.org/info/rfc2460>.

   [RFC4191]  Draves, R. and D. Thaler, "Default Router Preferences and
              More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191,
              November 2005, <http://www.rfc-editor.org/info/rfc4191>.

   [RFC4443]  Conta, A., Deering, S., and M. Gupta, Ed., "Internet
              Control Message Protocol (ICMPv6) for the Internet
              Protocol Version 6 (IPv6) Specification", RFC 4443,
              DOI 10.17487/RFC4443, March 2006,
              <http://www.rfc-editor.org/info/rfc4443>.

   [RFC4655]  Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
              Element (PCE)-Based Architecture", RFC 4655,
              DOI 10.17487/RFC4655, August 2006,
              <http://www.rfc-editor.org/info/rfc4655>.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              DOI 10.17487/RFC4861, September 2007,
              <http://www.rfc-editor.org/info/rfc4861>.

   [RFC7554]  Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using
              IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the
              Internet of Things (IoT): Problem Statement", RFC 7554,
              DOI 10.17487/RFC7554, May 2015,
              <http://www.rfc-editor.org/info/rfc7554>.

Appendix A.  appendix

   insert appendix here

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Author's Address

   Michael Richardson
   Sandelman Software Works

   Email: [email-masked]

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---

From: sajjad akbar <[email-masked]>
Date: Sun, 27 Nov 2016 13:42:46 +0000

Hi

As per my research experiments if we consider patient monitoring, I found TSCH
is considered as a new efficient MAC protocol that incorporates
time-slotted access with multiple channel and channel hopping. It is
popular mainly due to its interoperability with Internet of things (IoTs)
with appropriate support to mesh networks.  As TSCH more suitable for high
coverage scenarios and particularly node-coordinator scenarios like patient
monitoring systems are ignored, however slotted CSMA/CA proved to be more
efficient for patient monitoring. What you guys think?

Regards
Sajjad

On Mon, Nov 21, 2016 at 1:13 PM, Thomas Watteyne <[email-masked]>
wrote:

> The Enhanced Beacon (EB) is used by nodes already part of a TSCH network
> to annouce its existance.
> TW> It's clear at this point what IEs and RAs are, and I was expecting
> some text which says, basically
> _______________________________________________
> 6lo mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/6lo
>
>

---

From: [email-masked] (Dale R. Worley)
Date: Sun, 27 Nov 2016 13:11:19 -0500

> efficient for patient monitoring. What you guys think?

Can you give us more details about your experiments and their results?

Dale

---

From: sajjad akbar <[email-masked]>
Date: Mon, 28 Nov 2016 13:42:45 +0000

Hi

As I am doing my PhD thesis on patient monitoring systems which are based
on lower power radio like IEEE 802.15.4. I will just share a part of this
to elaborate the scenario in context of patient monitoring systems.

In patient monitoring systems where life critical data requires limited
delay, high throughput and energy efficient communication simultaneously. it
is observed that wireless biomedical sensors generate a large number of
small packets in a limited time period which poses challenges for the MAC
layer, especially on channel access process.  Therefore, for mentioned
challenges TSCH proves to be expensive in terms of management and
resources, however simple hybrid channel access mechanism of IEEE is more
suitable. In the following , the traffic patterns analysis mechanism is
developed to understand the requirements of the sensor nodes in patient
monitoring systems.

Regards