Internet DRAFT - draft-richardson-6tisch-join-enhanced-beacon
draft-richardson-6tisch-join-enhanced-beacon
6lo Working Group D. Dujovne
Internet-Draft Universidad Diego Portales
Intended status: Informational M. Richardson
Expires: July 20, 2018 Sandelman Software Works
January 16, 2018
IEEE802.15.4 Informational Element encapsulation of 6tisch Join
Information
draft-richardson-6tisch-join-enhanced-beacon-03
Abstract
In TSCH mode of IEEE802.15.4, as described by [RFC8180],
opportunities for broadcasts are limited to specific times and
specific channels. 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 small details critical
for new nodes (pledges) and long sleeping nodes may be carried within
the Enhanced Beacon.
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 https://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 July 20, 2018.
Copyright Notice
Copyright (c) 2018 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
(https://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
Dujovne & Richardson Expires July 20, 2018 [Page 1]
Internet-Draft IE for ICMPv6 January 2018
to this document. Code Components extracted from this document must
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 . . . . . . . . . . . . . . . . . 3
1.3. Layer-3 synchronization IPv6 Router solicitations and
advertisements . . . . . . . . . . . . . . . . . . . . . 3
2. Protocol Definition . . . . . . . . . . . . . . . . . . . . . 4
2.1. Protocol Example . . . . . . . . . . . . . . . . . . . . 4
3. Security Considerations . . . . . . . . . . . . . . . . . . . 5
4. Privacy Considerations . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . 6
Appendix A. Change history . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
[RFC7554] describes the use of the time-slotted channel hopping
(TSCH) mode of [ieee802154]. As further details in [RFC8180], an
Enhanced Beacon is transmitted during a slot designated a 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.
Dujovne & Richardson Expires July 20, 2018 [Page 2]
Internet-Draft IE for ICMPv6 January 2018
1.2. Layer-2 Synchronization
As explained in section 6 of [RFC8180], the Enhanced Beacon has a
number of purposes: synchronization of ASN and Join Metric, timeslot
template identifier, the channel hopping sequence identifier, TSCH
SlotFrame and Link IE.
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].
There are a limited number of timeslots designated as a broadcast
slot by each router. These slots are rare, and with 10ms slots, with
a slot-frame length of 100, there may be only 1 slot/s for the
beacon.
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 multicasted Router Advertisements (RA). If
no RA is heard within a set time, then 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 RS. This is an expensive
operation for two reasons: 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 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 Soliciation that 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.
Dujovne & Richardson Expires July 20, 2018 [Page 3]
Internet-Draft IE for ICMPv6 January 2018
2. Protocol Definition
[RFC8137] creates a registry for new IETF IE subtypes. This document
allocates a new subtype TBD-XXX.
This document documents a new IE subtype structure is as follows. As
explained in [RFC8137] the length of the Sub-Type Content can be
calculated from the container, so no length information is necessary.
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 |R|join priority| network ID |
+-+-+-+-+-+-+-+-+-+-+-+---------+ |
| |
+ +
| network ID |
+ +
| |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| network ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
J the Join prority value contains a number from 0 to 0x7f. Lower
numbers are considered to be a higher preference. A priority of
0x7f indicates that the announcer should never be considered as a
viable proxy. Lower value indicates willing to act as a Join
Proxy as described in [I-D.ietf-6tisch-minimal-security].
R the Router Advertisement flag is set if the sending node will act
as a Router for host-only nodes that need addressing via unicast
Router Solicitation messages.
network ID this is an opaque 16-byte identifier that uniquely
identifies this network, potentially among many networks that are
operating in the same frequencies in overlapping physical space.
In a 6tisch network, where RPL is used as the mesh routing protocol,
the network ID SHOULD be constructed from a SHA256 hash of the
DODAGID of the network. The result will be a 32-byte hash, and the
right-most 16-bytes should be used as the network ID.
2.1. Protocol Example
Here will be three examples of processing.
Dujovne & Richardson Expires July 20, 2018 [Page 4]
Internet-Draft IE for ICMPv6 January 2018
3. Security Considerations
All of the contents of this Information Element are sent in the
clear. The containing Enhanced Beacon is not encrypted, but may be
authenticated to nodes which have already received network-wide
keying material.
4. Privacy Considerations
The use of a network ID may reveal information about the network.
The use of a SHA256 hash of the DODAGID, rather than using the
DODAGID directly provides some cover the addresses used within the
network. The DODAGID is usually the IPv6 address of the root of the
RPL mesh.
An interloper with a radio sniffer would be able to use the network
ID to map out the extend of the mesh network.
5. IANA Considerations
Allocate a new number TBD-XXX from Registry IETF IE Sub-type ID.
This entry should be called 6tisch-Join-Info.
6. Acknowledgements
Thomas Watteyne provided extensive editorial comments on the
document.
7. References
7.1. Normative References
[I-D.ietf-6tisch-architecture]
Thubert, P., "An Architecture for IPv6 over the TSCH mode
of IEEE 802.15.4", draft-ietf-6tisch-architecture-13 (work
in progress), November 2017.
[I-D.ietf-6tisch-minimal-security]
Vucinic, M., Simon, J., Pister, K., and M. Richardson,
"Minimal Security Framework for 6TiSCH", draft-ietf-
6tisch-minimal-security-04 (work in progress), October
2017.
[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>.
Dujovne & Richardson Expires July 20, 2018 [Page 5]
Internet-Draft IE for ICMPv6 January 2018
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://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,
<https://www.rfc-editor.org/info/rfc2461>.
[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,
<https://www.rfc-editor.org/info/rfc6775>.
[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,
<https://www.rfc-editor.org/info/rfc7554>.
[RFC8137] Kivinen, T. and P. Kinney, "IEEE 802.15.4 Information
Element for the IETF", RFC 8137, DOI 10.17487/RFC8137, May
2017, <https://www.rfc-editor.org/info/rfc8137>.
7.2. Informative References
[I-D.ietf-6tisch-dtsecurity-secure-join]
Richardson, M., "6tisch Secure Join protocol", draft-ietf-
6tisch-dtsecurity-secure-join-01 (work in progress),
February 2017.
[RFC8180] Vilajosana, X., Ed., Pister, K., and T. Watteyne, "Minimal
IPv6 over the TSCH Mode of IEEE 802.15.4e (6TiSCH)
Configuration", BCP 210, RFC 8180, DOI 10.17487/RFC8180,
May 2017, <https://www.rfc-editor.org/info/rfc8180>.
Appendix A. Change history
This is an evolution of an earlier proposal which provided for
storing an entire IPv6 Router Adverisement in an Informational
Element. It was deemed too general a solution, possibly subject to
mis-use. This proposal restricts the use to just the key pieces of
information required.
Dujovne & Richardson Expires July 20, 2018 [Page 6]
Internet-Draft IE for ICMPv6 January 2018
Authors' Addresses
Diego Dujovne (editor)
Universidad Diego Portales
Escuela de Informatica y Telecomunicaciones, Av. Ejercito 441
Santiago, Region Metropolitana
Chile
Phone: +56 (2) 676-8121
Email: diego.dujovne@mail.udp.cl
Michael Richardson
Sandelman Software Works
Email: mcr+ietf@sandelman.ca
Dujovne & Richardson Expires July 20, 2018 [Page 7]
