< draft-ietf-roll-turnon-rfc8138-04.txt   draft-ietf-roll-turnon-rfc8138-05.txt >
ROLL P. Thubert, Ed. ROLL P. Thubert, Ed.
Internet-Draft L. Zhao Internet-Draft L. Zhao
Updates: 6550, 8138 (if approved) Cisco Systems Updates: 6550, 8138 (if approved) Cisco Systems
Intended status: Standards Track 24 January 2020 Intended status: Standards Track 24 March 2020
Expires: 27 July 2020 Expires: 25 September 2020
Configuration option for RFC 8138 Configuration option for RFC 8138
draft-ietf-roll-turnon-rfc8138-04 draft-ietf-roll-turnon-rfc8138-05
Abstract Abstract
This document complements RFC 8138 and dedicates a bit in the RPL This document complements RFC 8138 and dedicates a bit in the RPL
configuration option defined in RFC 6550 to indicate whether RFC 8138 configuration option defined in RFC 6550 to indicate whether RFC 8138
compression is used within the RPL Instance. compression is used within the RPL Instance.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
skipping to change at page 1, line 33 skipping to change at page 1, line 33
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on 27 July 2020. This Internet-Draft will expire on 25 September 2020.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. BCP 14 . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Updating RFC 6550 . . . . . . . . . . . . . . . . . . . . . . 3 2.1. References . . . . . . . . . . . . . . . . . . . . . . . 3
4. Updating RFC 8138 . . . . . . . . . . . . . . . . . . . . . . 3 2.2. Glossary . . . . . . . . . . . . . . . . . . . . . . . . 3
5. Transition Scenarios . . . . . . . . . . . . . . . . . . . . 4 2.3. BCP 14 . . . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Inconsistent State While Migrating . . . . . . . . . . . 5 3. Updating RFC 6550 . . . . . . . . . . . . . . . . . . . . . . 4
5.2. Single RPL Instance Scenario . . . . . . . . . . . . . . 5 4. Updating RFC 8138 . . . . . . . . . . . . . . . . . . . . . . 4
5.3. Double RPL Instances Scenario . . . . . . . . . . . . . . 6 5. Transition Scenarios . . . . . . . . . . . . . . . . . . . . 5
5.4. Rolling Back . . . . . . . . . . . . . . . . . . . . . . 6 5.1. Inconsistent State While Migrating . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 5.2. Single RPL Instance Scenario . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7 5.3. Double RPL Instances Scenario . . . . . . . . . . . . . . 7
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 5.4. Rolling Back . . . . . . . . . . . . . . . . . . . . . . 7
9. Normative References . . . . . . . . . . . . . . . . . . . . 7 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
10. Informative References . . . . . . . . . . . . . . . . . . . 8 7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
9. Normative References . . . . . . . . . . . . . . . . . . . . 8
10. Informative References . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
The transition of a RPL [RFC6550] network to activate the compression The transition of a RPL [RFC6550] network to activate the compression
defined in [RFC8138] can only be done when all routers in the network defined in [RFC8138] can only be done when all routers in the network
support it. A non-capable node acting as a router would drop the support it. Otherwise, a non-capable node acting as a router would
compressed packets and black-hole its subDAG. In a mixed case with drop the compressed packets and black-hole its subDAG. In a mixed
both RFC8138-capable and non-capable nodes, the compression may be case with both RFC8138-capable and non-capable nodes, the compression
turned on only if all the non-capable nodes act as leaves and their may be turned on only if all the non-capable nodes act as Hosts and
RPL parents handle the compression/decompression on their behalf. their RPL parents handle the compression/decompression for them.
This document complements RFC 8138 and dedicates a flag in the RPL This document complements [RFC8138] and dedicates a flag in the RPL
configuration option to indicate whether RFC 8138 compression should configuration option to indicate whether [RFC8138] compression should
be used within the RPL Instance. The setting of new flag is be used within the RPL Instance. The setting of this new flag is
controlled by the Root and propagates as is in the whole network. controlled by the Root and propagates as is in the whole network.
When the bit is not set, source nodes that support RFC 8138 should When the bit is not set, source nodes that support [RFC8138] should
refrain from using the compression unless the information is refrain from using the compression unless the information is
superseded by configuration. superseded by configuration.
This specification provides scenarios that force a legacy node to With RPL, a leaf is an IPv6 Host, which implies that leaves do not
become a RPL-Aware-Leaf (RAL). In that case, the 6LR must be aware forward packets. This specification provides scenarios that force a
by means out of scope that it must uncompress the packets before non-capable RPL-Aware Node (RAN) to become a leaf. The parent router
delivering to the RAL. must know, e.g., by configuration, or leveraging "RPL Capabilities"
[CAPABILITIES], when a leaf does not support the compression defined
in [RFC8138]. This is implicitly the case for a RPL-Unaware Leaf
(RUL) but is not known for a RPL-Aware Leaf (RAL). The parent router
must uncompress the packets before delivering them to a non-capable
leaf and it must compress the traffic from the leaf.
2. BCP 14 2. Terminology
2.1. 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].
"RPL", the "RPL Packet Information" (RPI), "RPL Instance" (indexed by
a RPLInstanceID) are defined in "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks" [RFC6550]. The RPI is the abstract
information that RPL defines to be placed in data packets, e.g., as
the RPL Option [RFC6553] within the IPv6 Hop-By-Hop Header. By
extension the term "RPI" is often used to refer to the RPL Option
itself. The DODAG Information Solicitation (DIS), Destination
Advertisement Object (DAO) and DODAG Information Object (DIO)
messages are also specified in [RFC6550].
This document uses the terms RPL-Unaware Leaf (RUL) and RPL Aware
Leaf (RAL) consistently with "Using RPI Option Type, Routing Header
for Source Routes and IPv6-in-IPv6 encapsulation in the RPL Data
Plane" [USEofRPLinfo]. The term RPL-Aware Node (RAN) refers to a
node that is either a RAL or a RPL Router. A RAN manages the
reachability of its addresses and prefixes by injecting them in RPL
by itself. In contrast, a RUL leverages "Registration Extensions for
IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN) Neighbor
Discovery" [RFC8505] to obtain reachability services from its parent
router(s) as specified in "Routing for RPL Leaves" [UNAWARE-LEAVES].
2.2. Glossary
This document often uses the following acronyms:
6LoWPAN: IPv6 over Low-Power Wireless Personal Area Network
6LoRH: 6LoWPAN Routing Header
DIO: DODAG Information Object (a RPL message)
DODAG: Destination-Oriented Directed Acyclic Graph
LLN: Low-Power and Lossy Network
RPL: IPv6 Routing Protocol for Low-Power and Lossy Networks
OF: RPL Objective Function
OCP: RPL Objective Code Point
MOP: RPL Mode of Operation
RPI: RPL Packet Information
RAL: RPL-Aware Leaf
RAN: RPL-Aware Node
RUL: RPL-Unaware Leaf
SRH: Source Routing Header
2.3. BCP 14
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119][RFC8174] when, and only when, they appear in all 14 [RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. Updating RFC 6550 3. Updating RFC 6550
This specification defines a new flag "Enable RFC8138 Compression" This specification defines a new flag "Enable RFC8138 Compression"
skipping to change at page 3, line 29 skipping to change at page 4, line 37
in the DIO Base Object. The new "T" flag is defined only for MOP in the DIO Base Object. The new "T" flag is defined only for MOP
value between 0 to 6. For a MOP value of 7 or above, the flag MAY value between 0 to 6. For a MOP value of 7 or above, the flag MAY
indicate something different and MUST NOT be interpreted as "Enable indicate something different and MUST NOT be interpreted as "Enable
RFC8138 Compression" unless the specification of the MOP indicates to RFC8138 Compression" unless the specification of the MOP indicates to
do so. do so.
4. Updating RFC 8138 4. Updating RFC 8138
A node that supports this specification MUST source packets in the A node that supports this specification MUST source packets in the
compressed form using [RFC8138] if and only if the "T" flag is set. compressed form using [RFC8138] if and only if the "T" flag is set.
This behaviour can be overridden by a configuration of the node in This behaviour can be overridden by the configuration of the node in
order to cope with intermediate implementations of the root that order to cope with intermediate implementations of the Root that
support [RFC8138] but not this specification and cannot set the "T" support [RFC8138] but not this specification and cannot set the "T"
flag. flag.
The decision of using [RFC8138] is made by the originator of the The decision of using [RFC8138] is made by the originator of the
packet depending on its capabilities and its knowledge of the state packet depending on its capabilities and its knowledge of the state
of the "T" flag. A router that encapsulates a packet is the of the "T" flag. A router that encapsulates a packet is the
originator of the resulting packet and decides whether to compress originator of the resulting packet and decides whether to compress
the outer headers as indicated above. An external target the outer headers as indicated above. An external target
[USEofRPLinfo] is not expected to support [RFC8138]. An intermediate [USEofRPLinfo] is not expected to support [RFC8138]. An intermediate
router MUST forward the packet in the form that the source used, router MUST forward the packet in the form that the source used,
either compressed or uncompressed, unless it is either forwarding to either compressed or uncompressed, unless it is forwarding to an
an external target or delivering to a leaf that is not known to external target or delivering to a leaf that is not known to support
support RFC 8138, in which cases it MUST uncompress the packet. [RFC8138], in which cases it MUST uncompress the packet.
A RPL-Unaware Leaf (RUL) [UNAWARE-LEAVES] is both a leaf and an
external target. A RUL does not participate to RPL and depends on
the 6LR to ensure its connectivity. Packets from/to a RUL are
tunneled back and forth to the Root regardless of the MOP used in the
RPL Instance. A node that supports this specification but does not
support [RFC8138] SHOULD join as a RUL to ensure that the 6LR is
aware it needs to uncompress the packets before delivering.
5. Transition Scenarios 5. Transition Scenarios
A node that supports [RFC8138] but not this specification can only be A node that supports [RFC8138] but not this specification can only be
used in a homogeneous network and an upgrade requires a "flag day" used in an homogeneous network. Enabling the [RFC8138] compression
where all nodes are updated and then the network is rebooted with requires a "flag day"; all nodes must be upgraded, and then the
implicitly RFC 8138 compression turned on with the "T" flag set on. network can be rebooted with the [RFC8138] compression turned on.
A node that supports this specification can work in a network with A node that supports this specification can work in a network with
RFC 8138 compression turned on or off with the "T" flag set [RFC8138] compression turned on or off with the "T" flag set
accordingly and in a network in transition from off to on or on to accordingly and in a network in transition from off to on or on to
off (see Section 5.1). off (see Section 5.1).
A node that does not support [RFC8138] can interoperate with nodes A node that does not support [RFC8138] can interoperate with nodes
that do in a network with RFC 8138 compression turned off. If the that do in a network with [RFC8138] compression turned off. If the
compression is turned on, the node cannot forward compressed packets compression is turned on, the node cannot forward compressed packets
and therefore it cannot act as a router. It may remain connected to and therefore it cannot act as a router. It may remain connected to
that network as a leaf, in which case it generates uncompressed that network as a leaf, generates uncompressed packets, and can
packets and can receive packets if they are delivered by the parent receive packets if they are delivered by the parent router in the
6LR in the uncompressed form. uncompressed form. Unless this is known by other means, the node
SHOULD join as a RUL as an indication that its parent router needs to
uncompress the packets before delivering.
[RFC6550] states that "Nodes other than the DODAG root MUST NOT [RFC6550] states that "Nodes other than the DODAG Root MUST NOT
modify this information when propagating the DODAG Configuration modify this information when propagating the DODAG Configuration
option". Therefore, even a legacy parent propagates the "T" flag as option". Therefore, even a legacy parent propagates the "T" flag as
set by the Root whether it supports this specification or not. So set by the Root whether it supports this specification or not. So
when the "T" flag is set, it is transparently flooded to all the when the "T" flag is set, it is transparently flooded to all the
nodes in the RPL Instance. nodes in the RPL Instance.
Sections 8.5 and 9.2 of [RFC6550] also suggests that a RPL-aware node Sections 8.5 and 9.2 of [RFC6550] also suggests that a RAN may only
may only attach to a DODAG as a leaf node when the node does not attach to a DODAG as a leaf when it does not support the Mode of
support the Mode of Operation of a RPL Instance, the Objective Operation of a RPL Instance, the Objective Function (OF) as indicated
Function (OF) as indicated by the Objective Code Point (OCP) or some by the Objective Code Point (OCP) or some other parameters in the
other parameters in the configuration option. configuration option.
Per the above, changing the OCP in a DODAG can be used to force nodes This specification reiterates that a RAN that is configured to
that do not support a particular feature to join as leaf only. This operate in a RPL Instance but does not support a value for a known
specification reiterates that a node that is configured to operate in parameter that is mandatory for routing, such as the OCP, MUST NOT
a RPL Instance but does not support a value for a known parameter operate as a router but MAY still join as a leaf. Note that a legacy
that is mandatory for routing MUST NOT operate as a router but MAY RAN will not recognize when a reserved field is used and will not
still join as a leaf. Note that a legacy node will not recognize turn to a leaf when the "T" flag is set.
when a reserved field is now used and will not turn to a leaf when
the "T" flag is set.
The intent for this specification is to perform a migration once and The intent for this specification is to perform a migration once and
for all without the need for a flag day. In particular it is not the for all without the need for a flag day. In particular it is not the
intention to undo the setting of the "T" flag, and though it is intention to undo the setting of the "T" flag, and though it is
possible to roll back (see Section 5.4), adding nodes that do not possible to roll back (see Section 5.4), adding nodes that do not
support [RFC8138] after a roll back may be problematic if the roll support [RFC8138] after a roll back may be problematic if the roll
back is not fully complete (see caveats in Section 5.2). back is not fully complete (see caveats in Section 5.2).
5.1. Inconsistent State While Migrating 5.1. Inconsistent State While Migrating
When the "T" flag is turned on in the configuration option by the When the "T" flag is turned on in the configuration option by the
root, the information slowly percolates through the DODAG as the DIO Root, the information slowly percolates through the DODAG as the DIO
gets propagated. Some nodes will see the flag and start sourcing gets propagated.
packets in the compressed form while other nodes in the same RPL
Instance are still not aware of it. Conversely, in non-storing mode,
the root will start using RFC 8138 with a SRH-6LoRH that routes all
the way to the last router or possibly to the leaf, if the leaf
supports RFC 8138.
This is why it is required that all the routers in the RPL Instance Some nodes will see the flag and start sourcing packets in the
support [RFC8138] at the time of the switch, and all nodes that do compressed form while other nodes in the same RPL Instance are still
not support [RFC8138] only operate as leaves. not aware of it. Conversely, in non-storing mode, the Root will
start using [RFC8138] with a Source Routing Header 6LoRH (SRH-6LoRH)
that routes all the way to the parent router or to the leaf.
To ensure that a packet is forwarded across the RPL Instance in the
form in which it was generated, it is required that all the routers
support [RFC8138] at the time of the switch, and that all nodes that
do not support [RFC8138] only operate as leaves.
Setting the "T" flag is ultimately the responsibility of the network Setting the "T" flag is ultimately the responsibility of the network
administrator. In a case of upgrading a network to turn the administrator. In a case of upgrading a network to turn the
compression on, the network SHOULD be operated with the "T" flag compression on, the network SHOULD be operated with the "T" flag
reset until all targeted nodes are upgraded to support this reset until all targeted nodes are upgraded to support this
specification. Section 5.2 and Section 5.3 provide possible specification. Section 5.2 and Section 5.3 provide possible
transition scenarios where this can be enforced. transition scenarios where this can be enforced.
5.2. Single RPL Instance Scenario 5.2. Single RPL Instance Scenario
In a Single RPL Instance Scenario, nodes that support RFC 8138 are In a Single RPL Instance Scenario, nodes that support [RFC8138] are
configured with a new OCP, that may use the same OF operation or a configured with a new OCP, that may use the same OF operation or a
variation of it. The root sets the "T" flag at the time it migrates variation of it, while nodes that do not support [RFC8138] are not,
to the new OCP. As a result, nodes that do not support RFC 8138 join but are configured to join an unknown OCP.
as leaves and do not forward packets anymore. The leaves generate
packets without compression. The parents - which supports RFC 8138 - The Root migrates to the new OCP before it sets the "T" flag, so that
may encapsulate the packets using RFC 8138 if needed. The other way nodes that do not support [RFC8138] are all attached as leaves when
around, the root encapsulates packets to the leaves all the way to the "T" flag is eventually set.
the parent, which decapsulates and distribute the uncompressed inner
packet to the leaf. The parent router - which supports [RFC8138] - compresses the packets
originated from the leaf and uncompresses the packets going to the
leaf. This may be done on the fly by the parent of a non-capable
RAL, or as part of the tunneling operation between the parent and the
Root, if the leaf behaves as a RUL. This is described in section 7,
8, and 9 of [USEofRPLinfo].
Note that though tunneling from the Root to the parent is the generic
case for RULs, on paper it is possible for the Root to avoid it for
the traffic that it originates. The Root SHOULD always use tunneling
to the parent of a RUL, even for its own packets, unless it knows
that the leaf supports [RFC8138].
This scenario presents a number of caveats: This scenario presents a number of caveats:
* The method consumes an extra OCP. It also requires a means to * The method consumes an extra OCP. It also forces nodes that do
signal the capabilities of the leaf, e.g., using "RPL Mode of not support [RFC8138] to operate as RULs, unless there is a method
Operation extension" [MOP-EXT]. to let the parent router know that it must uncompress the packet
for this RAL.
* If an implementation does not move to a leaf mode when the OCP is * If the RPL implementation of a node does not turn it to a leaf
changed to an unknown one, then the node may be stalled. when the OCP is changed to an unknown one, then the node may be
stalled.
* If the only possible parents of a node are nodes that do not * If the only possible parents of a node are nodes that do not
support RFC 8138, then that node will loose all its parent at the support [RFC8138], then that node will loose all its parent at the
time of the migration and it will be stalled until a parent is time of the migration and it will be stalled until a parent is
deployed with the new capability. deployed with the new capability.
* Nodes that only support RFC8138 for forwarding may not parse the
RPI in native form. If such nodes are present, the parent needs
to encapsulate with RFC8138.
5.3. Double RPL Instances Scenario 5.3. Double RPL Instances Scenario
An alternate to the Single RPL Instance Scenario is to deploy an An alternative to the Single RPL Instance Scenario is to deploy an
additional RPL Instance for the nodes that support [RFC8138]. The additional RPL Instance for the nodes that support [RFC8138].
two RPL Instances operate independently as specified in [RFC6550].
The preexisting RPL Instance that does not use [RFC8138], whereas the
new RPL Instance does. This is signaled by the "T" flag which is
only set in the configuration option in DIO messages in the new RPL
Instance.
Nodes that support RFC 8138 participate to both Instances but favor The two RPL Instances operate independently as specified in
the new RPL Instance for the traffic that they source. On the other [RFC6550]. The preexisting RPL Instance does not use [RFC8138],
hand, nodes that only support the uncompressed format would either whereas the new RPL Instance does. This is signaled by the "T" flag
not be configured for the new RPL Instance, or would be configured to which is only set in the configuration option in DIO messages in the
join it as leaves only. new RPL Instance.
Nodes that support [RFC8138] participate in both Instances but favor
the new RPL Instance for the traffic that they source. By contrast,
nodes that only support the uncompressed format would either not be
configured for the new RPL Instance, or would be configured to join
it as leaves only.
This method eliminates the risks of nodes being stalled that are This method eliminates the risks of nodes being stalled that are
described in Section 5.2 but requires implementations to support at described in Section 5.2 but requires implementations to support at
least two RPL Instances and demands management capabilities to least two RPL Instances and demands management capabilities to
introduce new RPL Instances and deprecate old ones. introduce new RPL Instances and deprecate old ones.
5.4. Rolling Back 5.4. Rolling Back
After downgrading a network to turn the [RFC8138] compression off, After downgrading a network to turn the [RFC8138] compression off,
the administrator SHOULD make sure that all nodes have converged to the administrator SHOULD make sure that all nodes have converged to
skipping to change at page 7, line 15 skipping to change at page 8, line 20
+------------+---------------------------------+-----------+ +------------+---------------------------------+-----------+
| Bit Number | Capability Description | Reference | | Bit Number | Capability Description | Reference |
+============+=================================+===========+ +============+=================================+===========+
| 2 | Turn on RFC8138 Compression (T) | THIS RFC | | 2 | Turn on RFC8138 Compression (T) | THIS RFC |
+------------+---------------------------------+-----------+ +------------+---------------------------------+-----------+
Table 1: New DODAG Configuration Option Flag Table 1: New DODAG Configuration Option Flag
7. Security Considerations 7. Security Considerations
First of all, it is worth noting that with [RFC6550], every node in
the LLN that is RPL-aware can inject any RPL-based attack in the
network. A trust model MUST be put in place so that rogue nodes are
excluded from participating to the RPL and the 6LowpAN signaling, and
from the data packet exchange. This trust model could be at a
minimum based on a Layer-2 Secure joining and the Link-Layer
security. This is a generic RPL and 6LoWPAN requirement, see Req5.1
in Appendix of [RFC8505].
Setting the "T" flag before some routers are upgraded may cause a Setting the "T" flag before some routers are upgraded may cause a
loss of packets. The new bit is protected as the rest of the loss of packets. The new bit is protected as the rest of the
configuration so this is just one of the many attacks that can happen configuration so this is just one of the many attacks that can happen
if an attacker manages to inject a corrupted configuration. if an attacker manages to inject a corrupted configuration.
Setting and resetting the "T" flag may create inconsistencies in the Setting and resetting the "T" flag may create inconsistencies in the
network but as long as all nodes are upgraded to RFC 8138 support network but as long as all nodes are upgraded to [RFC8138] support
they will be able to forward both forms. The draft insists that the they will be able to forward both forms. The source is responsible
source is responsible for selecting whether the packet is compressed for selecting whether the packet is compressed or not, and all
or not, and all routers must use the format that the source selected. routers must use the format that the source selected. So the result
So the result of an inconsistency is merely that both forms will be of an inconsistency is merely that both forms will be present in the
present in the network, at an additional cost of bandwidth for network, at an additional cost of bandwidth for packets in the
packets in the uncompressed form. uncompressed form.
8. Acknowledgments 8. Acknowledgments
The authors wish to thank Rahul Jadhav for his in-depth review and The authors wish to thank Dominique Barthel and Rahul Jadhav for
constructive suggestions. their in-depth reviews and constructive suggestions.
9. Normative References 9. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550, Low-Power and Lossy Networks", RFC 6550,
DOI 10.17487/RFC6550, March 2012, DOI 10.17487/RFC6550, March 2012,
<https://www.rfc-editor.org/info/rfc6550>. <https://www.rfc-editor.org/info/rfc6550>.
[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>.
[USEofRPLinfo] [USEofRPLinfo]
Robles, I., Richardson, M., and P. Thubert, "Using RPI Robles, I., Richardson, M., and P. Thubert, "Using RPI
Option Type, Routing Header for Source Routes and IPv6-in- Option Type, Routing Header for Source Routes and IPv6-in-
IPv6 encapsulation in the RPL Data Plane", Work in IPv6 encapsulation in the RPL Data Plane", Work in
Progress, Internet-Draft, draft-ietf-roll-useofrplinfo-34, Progress, Internet-Draft, draft-ietf-roll-useofrplinfo-38,
20 January 2020, <https://tools.ietf.org/html/draft-ietf- 23 March 2020, <https://tools.ietf.org/html/draft-ietf-
roll-useofrplinfo-34>. roll-useofrplinfo-38>.
[UNAWARE-LEAVES] [UNAWARE-LEAVES]
Thubert, P. and M. Richardson, "Routing for RPL Leaves", Thubert, P. and M. Richardson, "Routing for RPL Leaves",
Work in Progress, Internet-Draft, draft-ietf-roll-unaware- Work in Progress, Internet-Draft, draft-ietf-roll-unaware-
leaves-08, 16 December 2019, <https://tools.ietf.org/html/ leaves-13, 17 March 2020, <https://tools.ietf.org/html/
draft-ietf-roll-unaware-leaves-08>. draft-ietf-roll-unaware-leaves-13>.
10. Informative References 10. Informative References
[RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low-
Power and Lossy Networks (RPL) Option for Carrying RPL
Information in Data-Plane Datagrams", RFC 6553,
DOI 10.17487/RFC6553, March 2012,
<https://www.rfc-editor.org/info/rfc6553>.
[RFC8138] Thubert, P., Ed., Bormann, C., Toutain, L., and R. Cragie, [RFC8138] Thubert, P., Ed., Bormann, C., Toutain, L., and R. Cragie,
"IPv6 over Low-Power Wireless Personal Area Network "IPv6 over Low-Power Wireless Personal Area Network
(6LoWPAN) Routing Header", RFC 8138, DOI 10.17487/RFC8138, (6LoWPAN) Routing Header", RFC 8138, DOI 10.17487/RFC8138,
April 2017, <https://www.rfc-editor.org/info/rfc8138>. April 2017, <https://www.rfc-editor.org/info/rfc8138>.
[MOP-EXT] Jadhav, R., Thubert, P., and M. Richardson, "Mode of [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C.
Operation extension and Capabilities", Work in Progress, Perkins, "Registration Extensions for IPv6 over Low-Power
Internet-Draft, draft-ietf-roll-mopex-cap-01, 2 November Wireless Personal Area Network (6LoWPAN) Neighbor
2019, <https://tools.ietf.org/html/draft-ietf-roll-mopex- Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018,
cap-01>. <https://www.rfc-editor.org/info/rfc8505>.
[CAPABILITIES]
Jadhav, R., Thubert, P., Richardson, M., and R. Sahoo,
"RPL Capabilities", Work in Progress, Internet-Draft,
draft-ietf-roll-capabilities-02, 11 March 2020,
<https://tools.ietf.org/html/draft-ietf-roll-capabilities-
02>.
Authors' Addresses Authors' Addresses
Pascal Thubert (editor) Pascal Thubert (editor)
Cisco Systems, Inc Cisco Systems, Inc
Building D Building D
45 Allee des Ormes - BP1200 45 Allee des Ormes - BP1200
06254 MOUGINS - Sophia Antipolis 06254 MOUGINS - Sophia Antipolis
France France
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