draft-ietf-roll-turnon-rfc8138-03.txt   draft-ietf-roll-turnon-rfc8138-04.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 22 January 2020 Intended status: Standards Track 24 January 2020
Expires: 25 July 2020 Expires: 27 July 2020
Configuration option for RFC 8138 Configuration option for RFC 8138
draft-ietf-roll-turnon-rfc8138-03 draft-ietf-roll-turnon-rfc8138-04
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
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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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 25 July 2020. This Internet-Draft will expire on 27 July 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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Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Simplified BSD License. provided without warranty as described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. BCP 14 . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. BCP 14 . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Updating RFC 6550 . . . . . . . . . . . . . . . . . . . . . . 2 3. Updating RFC 6550 . . . . . . . . . . . . . . . . . . . . . . 3
4. Updating RFC 8138 . . . . . . . . . . . . . . . . . . . . . . 3 4. Updating RFC 8138 . . . . . . . . . . . . . . . . . . . . . . 3
5. Transition Scenarios . . . . . . . . . . . . . . . . . . . . 3 5. Transition Scenarios . . . . . . . . . . . . . . . . . . . . 4
5.1. Inconsistent State While Migrating . . . . . . . . . . . 5 5.1. Inconsistent State While Migrating . . . . . . . . . . . 5
5.2. Single RPL Instance Scenario . . . . . . . . . . . . . . 5 5.2. Single RPL Instance Scenario . . . . . . . . . . . . . . 5
5.3. Double RPL Instances Scenario . . . . . . . . . . . . . . 6 5.3. Double RPL Instances Scenario . . . . . . . . . . . . . . 6
5.4. Rolling Back . . . . . . . . . . . . . . . . . . . . . . 6 5.4. Rolling Back . . . . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7 7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
9. Normative References . . . . . . . . . . . . . . . . . . . . 7 9. Normative References . . . . . . . . . . . . . . . . . . . . 7
10. Informative References . . . . . . . . . . . . . . . . . . . 8 10. Informative References . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction 1. Introduction
The transition to [RFC8138] in a network can only be done when all The transition of a RPL [RFC6550] network to activate the compression
nodes support the specification. In a mixed case with both defined in [RFC8138] can only be done when all routers in the network
RFC8138-capable and non-capable nodes, the compression should be support it. A non-capable node acting as a router would drop the
turned off. compressed packets and black-hole its subDAG. In a mixed case with
both RFC8138-capable and non-capable nodes, the compression may be
turned on only if all the non-capable nodes act as leaves and their
RPL parents handle the compression/decompression on their behalf.
This document complements RFC 8138 and dedicates a bit in the RPL This document complements RFC 8138 and dedicates a flag in the RPL
configuration option to indicate whether RFC 8138 compression should configuration option to indicate whether RFC 8138 compression should
be used within the RPL Instance. When the bit is not set, source be used within the RPL Instance. The setting of new flag is
nodes that support RFC 8138 should refrain from using the compression controlled by the Root and propagates as is in the whole network.
unless the information is superseded by configuration. When the bit is not set, source nodes that support RFC 8138 should
refrain from using the compression unless the information is
superseded by configuration.
This specification provides scenarios that force a legacy node to
become a RPL-Aware-Leaf (RAL). In that case, the 6LR must be aware
by means out of scope that it must uncompress the packets before
delivering to the RAL.
2. BCP 14 2. 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
RPL defines a configuration option that is registered to IANA in This specification defines a new flag "Enable RFC8138 Compression"
section 20.14. of [RFC6550]. This specification defines a new flag (T). The "T" flag is set to turn on the use of the compression of
"Enable RFC8138 Compression" (T) that is encoded in one of the RPL artifacts with [RFC8138] within a RPL Instance. If a RPL
reserved control bits in the option. The new flag is set to turn on Instance has multiple Roots then they must be coordinated to use the
the use of the compression of RPL artifacts with RFC 8138. The bit same setting.
RPL defines a Configuration Option that is registered to IANA in
section 20.14. of [RFC6550]. The "T" flag is encoded in one of the
reserved control bits in the RPL Configuration Option. The bit
position of the "T" flag is indicated in Section 6. position of the "T" flag is indicated in Section 6.
Section 6.3.1. of [RFC6550] defines a 3-bit Mode of Operation (MOP) Section 6.3.1. of [RFC6550] defines a 3-bit Mode of Operation (MOP)
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
This document specifies controls that enable and disable the use of A node that supports this specification MUST source packets in the
the [RFC8138] compression in a RPL Instance. Arguably, this could compressed form using [RFC8138] if and only if the "T" flag is set.
have been done in [RFC8138] itself. This behaviour can be overridden by a configuration of the node in
order to cope with intermediate implementations of the root that
A node that supports this specification SHOULD source packets in the support [RFC8138] but not this specification and cannot set the "T"
compressed form using [RFC8138] if the new "T" flag is set in the RPL flag.
configuration option from its parents. Failure to do so will result
in larger packets, yields higher risks of loss and may cause a
fragmentation.
A node that supports this specification SHOULD refrain from sourcing The decision of using [RFC8138] is made by the originator of the
packets in the compressed form using [RFC8138] if the "T" flag is packet depending on its capabilities and its knowledge of the state
reset. This behaviour can be overridden by a configuration of the of the "T" flag. A router that encapsulates a packet is the
node in order to cope with intermediate implementations of the root originator of the resulting packet and decides whether to compress
that support [RFC8138] but not this specification and cannot set the the outer headers as indicated above. An external target
"T" flag. [USEofRPLinfo] is not expected to support [RFC8138]. An intermediate
router MUST forward the packet in the form that the source used,
either compressed or uncompressed, unless it is either forwarding to
an external target or delivering to a leaf that is not known to
support RFC 8138, in which cases it MUST uncompress the packet.
The decision of using RFC 8138 to compress a packet is made at the A RPL-Unaware Leaf (RUL) [UNAWARE-LEAVES] is both a leaf and an
source depending on its capabilities and its knowledge of the state external target. A RUL does not participate to RPL and depends on
of the "T" flag. A router MUST forward the packet in the form that the 6LR to ensure its connectivity. Packets from/to a RUL are
the source used, either compressed or uncompressed. A router that tunneled back and forth to the Root regardless of the MOP used in the
encapsulates a packet is the source of the resulting packet and the RPL Instance. A node that supports this specification but does not
rules above apply to it in that case. 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 a homogeneous network and an upgrade requires a "flag day"
where all nodes are updated and then the network is rebooted with where all nodes are updated and then the network is rebooted with
implicitly RFC 8138 compression turned on with the "T" flag set on. implicitly RFC 8138 compression turned on with the "T" flag set 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 RFC 8138 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 a node A node that does not support [RFC8138] can interoperate with nodes
that supports this specification in a network with RFC 8138 that do in a network with RFC 8138 compression turned off. If the
compression turned off. But it cannot forward compressed packets and compression is turned on, the node cannot forward compressed packets
therefore it cannot act as a router in a network with RFC 8138 and therefore it cannot act as a router. It may remain connected to
compression turned on. It may remain connected to that network as a that network as a leaf, in which case it generates uncompressed
leaf and generate uncompressed packets. The leaf can receive packets packets and can receive packets if they are delivered by the parent
if they are delivered by the parent 6LR in the uncompressed form. 6LR in the uncompressed form.
This requires a knowledge by the 6LR that the leaf does not support
RFC 8138. A RPL-Unaware-Leaf (RUL) [USEofRPLinfo] is an external
target and by default is not expected to support RFC 8138.
[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". In other words, the configuration option is a way for the option". Therefore, even a legacy parent propagates the "T" flag as
root to configure the LLN nodes but it cannot be used by a parent to set by the Root whether it supports this specification or not. So
advertise its capabilities down the DODAG. A parent propagates the when the "T" flag is set, it is transparently flooded to all the
"T" flag as set whether it supports RFC 8138 or not. The setting of nodes in the RPL Instance.
the "T" flag can thus not be used as an indication of the support by
the sender, and a child cannot favor a parent based on it.
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 RPL-aware node
may attach to a DODAG as a leaf node only, e.g., when a node does not may only attach to a DODAG as a leaf node when the node does not
support the Mode of Operation of a RPL Instance, the Objective support the Mode of Operation of a RPL Instance, the Objective
Function (OF) as indicated by the Objective Code Point (OCP) or some Function (OF) as indicated by the Objective Code Point (OCP) or some
other parameters in the configuration option. [USEofRPLinfo] other parameters in the configuration option.
indicates that the node may also join as a RUL, in which case it
refrains from participating to RPL and depends on the 6LR to ensure
connectivity regardless on the way the RPL network is operated.
This means that changing the OCP in a DODAG can be used to force Per the above, changing the OCP in a DODAG can be used to force nodes
nodes that do not support a particular feature to join as leaf only. that do not support a particular feature to join as leaf only. This
This specification reiterates that a node that is configured to specification reiterates that a node that is configured to operate in
operate in a RPL Instance but does not support a value for a known a RPL Instance but does not support a value for a known parameter
parameter that is mandatory for routing MUST NOT operate as a router that is mandatory for routing MUST NOT operate as a router but MAY
but MAY still join as a leaf. Note that a legacy node will not still join as a leaf. Note that a legacy node will not recognize
recognize when a reserved field is now used and will not turn to a when a reserved field is now used and will not turn to a leaf when
leaf when that happens. 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
skipping to change at page 7, line 15 skipping to change at page 7, line 15
+------------+---------------------------------+-----------+ +------------+---------------------------------+-----------+
| 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
Turning the "T" flag on 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.
Turning the "T" flag on and off 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 RFC 8138 support
they will be able to forward both forms. The draft insists that the they will be able to forward both forms. The draft insists that the
source is responsible for selecting whether the packet is compressed source is responsible for selecting whether the packet is compressed
or not, and all routers must use the format that the source selected. or not, and all routers must use the format that the source selected.
So the result of an inconsistency is merely that both forms will be So the result of an inconsistency is merely that both forms will be
present in the network, at an additional cost of bandwidth for present in the network, at an additional cost of bandwidth for
packets in the uncompressed form. packets in the uncompressed form.
8. Acknowledgments 8. Acknowledgments
The authors wish to thank Rahul Jadhav for his in-depth review 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>.
skipping to change at page 8, line 9 skipping to change at page 8, line 13
<https://www.rfc-editor.org/info/rfc6550>. <https://www.rfc-editor.org/info/rfc6550>.
[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-34,
20 January 2020, <https://tools.ietf.org/html/draft-ietf- 20 January 2020, <https://tools.ietf.org/html/draft-ietf-
roll-useofrplinfo-34>. roll-useofrplinfo-34>.
[UNAWARE-LEAVES]
Thubert, P. and M. Richardson, "Routing for RPL Leaves",
Work in Progress, Internet-Draft, draft-ietf-roll-unaware-
leaves-08, 16 December 2019, <https://tools.ietf.org/html/
draft-ietf-roll-unaware-leaves-08>.
10. Informative References 10. Informative References
[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 [MOP-EXT] Jadhav, R., Thubert, P., and M. Richardson, "Mode of
Operation extension and Capabilities", Work in Progress, Operation extension and Capabilities", Work in Progress,
Internet-Draft, draft-ietf-roll-mopex-cap-01, 2 November Internet-Draft, draft-ietf-roll-mopex-cap-01, 2 November
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