Eliding and Querying RPL Information
draft-thubert-roll-eliding-dio-information-00
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Pascal Thubert , Dominique Barthel , Rahul Jadhav | ||
| Last updated | 2019-10-15 | ||
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draft-thubert-roll-eliding-dio-information-00
ROLL P. Thubert, Ed.
Internet-Draft Cisco Systems
Updates: 6550 (if approved) D. Barthel
Intended status: Standards Track Orange Labs
Expires: 17 April 2020 R.A. Jadhav
Huawei Tech
15 October 2019
Eliding and Querying RPL Information
draft-thubert-roll-eliding-dio-information-00
Abstract
This document presents a method to elide a group of global RPL
options by synchonizing the state associated with each of these
options between parent and child using a new sequence counter in DIO
messages. A child that missed a DIO message with an update of any of
those protected options detects it by the change of sequence counter
and queries the update with a DIS Message.
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
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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 17 April 2020.
Copyright Notice
Copyright (c) 2019 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 to this document. Code Components
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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
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. BCP 14 . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. References . . . . . . . . . . . . . . . . . . . . . . . 3
2.3. Glossary . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Updating RFC 6550 . . . . . . . . . . . . . . . . . . . . . . 4
4. New RPL Configuration State Sequence . . . . . . . . . . . . 4
5. Protected Options . . . . . . . . . . . . . . . . . . . . . . 5
6. Child Operation . . . . . . . . . . . . . . . . . . . . . . . 6
7. Pulling Options . . . . . . . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
10. Security Considerations . . . . . . . . . . . . . . . . . . . 7
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
12. Normative References . . . . . . . . . . . . . . . . . . . . 7
13. Informative References . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
Classical Link State protocol synchronize their Link State Database
(LSDB) by sequencing every change. Each interested node maintains
the last sequence of the LSDB it is synchronizing with. If a last
known sequence is older than the current, the node needs to learn one
by one all the state changes between the last known and the current
state.
[RPL] does not operate that way. With RPL, the routing information
is repeated over and over in DODAG Information Object (DIO) and
Destination Advertisement Object (DAO) messages. There is no concept
of synchronization. The most recent information overrides a previous
one and a stale state eventually times out.
The RPL way was designed to enable routing from most nodes to most
nodes most of the time in a Low-Power Lossy Network (LLN) where the
quality of the links and the cost of communications does not permit
to maintain a permanent synchronization. This principle was applied
to both the routing information and non-routing state such as
configuration settings, prefix information, and node capabilities.
This non-routing state may be needed to decide whether a node can
join a network as a leaf or as a router, and may affect the parent
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selection. [RPL] allows a parent to elide that information in the
DIO it sends repeatedly, but if it does so, a newcomer child may have
missed the early DIOs that contained the configuration option and
live with only partial information. If it is pessimistic, it may
query all possible information even when it is not needed.
Conversely, a node that slept may have missed a DIO message with a
change in some critical information and not be aware of it, so it may
fail to query for the update and operate on deprecated parameters.
This document uses a new sequence counter to synchronize the state in
a child node with that of its parent, and recursively with that of
the network.
2. Terminology
2.1. BCP 14
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here.
2.2. References
The Terminology used in this document is consistent with and
incorporates that described in Terms Used in Routing for Low-Power
and Lossy Networks (LLNs). [RFC7102].
Other terms in use in LLNs are found in Terminology for
Constrained-Node Networks [RFC7228].
A glossary of classical RPL acronyms is given in Section 2.3.
The term "byte" is used in its now customary sense as a synonym for
"octet".
"RPL", "RPL Packet Information" (RPI) and "RPL Instance", DIO, DAO
and DIS messages are defined in the "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks" [RPL] specification.
This document uses the terms RPL-Unaware Leaf (RUL) and RPL Aware
Leaf (RAL) consistently with [USE_OF_RPL_INFO].
The term RPL-Unaware Leaf (RUL) is used to refer to a node that uses
a RPL router (without necessarily knowing it) as 6LR and depends on
that router to obtain reachability for its addresses inside the RPL
domain. On the contrary, the term RPL-Aware Node (RAN) is used to
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refer to a RAL or a RPL router that participates to RPL and
advertises its addresses of prefixes by itself.
2.3. Glossary
This document often uses the following acronyms:
DODAG Destination-Oriented Directed Acyclic Graph
LLN Low-Power and Lossy Network
RPI RPL Packet Information (an Option in the Hop-By_Hop Header)
RAL RPL-Aware Leaf
RAN RPL-Aware Node, a RPL router or a RPL-Aware Leaf
RS Router Solicitation
RPL IPv6 Routing Protocol for LLNs (pronounced ripple)
RUL RPL-Unaware Leaf
3. Updating RFC 6550
This document adds a sequence counter called RPL Configuration State
Sequence (RCSS) to the DIO message. The RCSS is set by the root and
operated as specified in Section 7 of [RPL], more in Section 4.
This document introduces a new RPL Control Message Options called the
Abbreviated Option Option (AOO). The AOO is an empty replacement of
an existing option that indicates the RCSS of the last change of that
option.
This document modifies the Solicited Information Option to enable the
individual query of the protected options by a node that missed a
change, more in Section 7.
4. New RPL Configuration State Sequence
The format of the DIO Base Object is defined in section 6.3.1 of
[RPL]. This specification uses a 8th octet that was previously
reserved to transport the RCSS.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RPLInstanceID |Version Number | Rank |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|G|0| MOP | Prf | DTSN | Flags | RCSS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ DODAGID +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option(s)...
+-+-+-+-+-+-+-+-+
Figure 1: MOdified DIO Base Object
Updated fields:
RCSS
One Byte, the RPL Configuration State Sequence
The RCSS protects network-wide options that are set by the root and
that are propagated without a change down the DODAG. The RCSS MUST
be incremented when the root sends a DIO where at least one of the
protected options is modified. It MUST propagated down without a
change together with the options that it protects.
During the straight part of the lollipop, a second reboot of the root
might not be recognized and a same value of the RCSS may appear with
new values in the protected options. For that reason the protected
options MUST be present in the DIOs during the straight part of the
lollipop and the root SHOULD move rapidly away from the straight part
once the network has settled by resetting the RCSS to 0, which places
the RCSS in the circular region of the lollipop.
5. Protected Options
The protected options are:
1. The Route Information Option (RIO) defined in section 6.7.5 of
[RPL]
2. The DODAG Configuration Option (DCO) defined in section 6.7.6 of
[RPL]
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3. The Prefix Information Option (PIO) defined in section 6.7.10 of
[RPL]
4. The Extended MOP Option (MOPex) defined in [MOPEX-CAP]
5. The Global Capabilities Option (GCO) defined in [MOPEX-CAP]
When a protected option is unchanged from the previous DIOs, the root
MAY replace it with its abbreviated version. The abbreviated version
of an option is transported in a 4-bytes long Abbreviated Option
Option (AOO). The AOO indicates the RCSS at which the protected
option was last changed.
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 2
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length | Abbrev. opt. | Last Mod RCSS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Abbreviated Option Option Format
Option fields:
Option Type
One byte indicating "Abbreviated Option", see Table 1
Option Length
MUST be set to 2 indicating Option data of 2 bytes
Abbreviated Option
The Option Type of the option being abreviated
Last Modification RCSS
The RCSS at which the option was last modified
6. Child Operation
When a field is modified in one of the protected options in a fashion
that may affect the routing or forwarding decision inside the DODAG,
the root MUST send a DIO with the protected options. Unchanged
options may be abreviated as discussed in Section 5.
The freshness of the protected options is asserted based on the RCSS.
RCSS values are compared as described in section 7.2 of [RPL]. When
a parent exposes a new RCSS, the child node SHOULD refrain from using
that parent until it has resynchronized all the protected fields to
the latest. When it is resynchronized, the child SHOULD refrain from
using other parents that expose an older RCSS.
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A child MUST store the content of all the protected options and keep
track of the RCSS of the DIO where each of these option was last seen
in a non-abbreviated version. If that RCSS is fresher than the Last
Modification RCSS in the abbreviated version of the option then the
child is up-to-date for that option. If a protected option elided in
a DIO and not abbreviated, and the child has a stored RCSS value for
that option that is lower than the RCSS in the DIO, then the child
MUST query that option from the parent to ensure that is has the
latest. This is done with a DIS message as indicated in Section 7.
7. Pulling Options
8. Security Considerations
TBD
9. IANA Considerations
A new entries is required for the new option of type "Abbreviated
Option", from the "RPL Control Message Options" space defined for
[RPL].
+----------+--------------------+-----------+
| Value | Meaning | Reference |
+==========+====================+===========+
| TBD IANA | Abbreviated Option | THIS RFC |
+----------+--------------------+-----------+
Table 1: New Option Type
10. Security Considerations
TBD
11. Acknowledgments
12. Normative References
[MOPEX-CAP]
Jadhav, R. and P. Thubert, "Mode of Operation extension
and Capabilities", Internet-Draft, draft-ietf-roll-mopex-
cap-00, 9 August 2019, <https://tools.ietf.org/html/draft-
ietf-roll-mopex-cap-00>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
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DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and
Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January
2014, <https://www.rfc-editor.org/info/rfc7102>.
[RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for
Constrained-Node Networks", RFC 7228,
DOI 10.17487/RFC7228, May 2014,
<https://www.rfc-editor.org/info/rfc7228>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RPL] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550,
DOI 10.17487/RFC6550, March 2012,
<https://www.rfc-editor.org/info/rfc6550>.
[USE_OF_RPL_INFO]
Robles, I., Richardson, M., and P. Thubert, "Using RPL
Option Type, Routing Header for Source Routes and IPv6-in-
IPv6 encapsulation in the RPL Data Plane", Internet-Draft,
draft-ietf-roll-useofrplinfo-31, 7 August 2019,
<https://tools.ietf.org/html/draft-ietf-roll-useofrplinfo-
31>.
13. Informative References
Authors' Addresses
Pascal Thubert (editor)
Cisco Systems, Inc
Building D, 45 Allee des Ormes - BP1200
06254 Mougins - Sophia Antipolis
France
Phone: +33 497 23 26 34
Email: pthubert@cisco.com
Dominique Barthel
Orange Labs
28 chemin du Vieux ChĂȘne
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38243 Meylan
France
Email: dominique.barthel@orange.com
Rahul Arvind Jadhav
Huawei Tech
Kundalahalli Village, Whitefield,
Bangalore 560037
Karnataka
India
Phone: +91-080-49160700
Email: rahul.ietf@gmail.com
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