draft-ietf-roll-turnon-rfc8138-02.txt   draft-ietf-roll-turnon-rfc8138-03.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 12 December 2019 Intended status: Standards Track 22 January 2020
Expires: 14 June 2020 Expires: 25 July 2020
Configuration option for RFC 8138 Configuration option for RFC 8138
draft-ietf-roll-turnon-rfc8138-02 draft-ietf-roll-turnon-rfc8138-03
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
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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 14 June 2020. This Internet-Draft will expire on 25 July 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 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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extracted from this document must include Simplified BSD License text extracted from this document must include Simplified BSD License text
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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 . . . . . . . . . . . . . . . . . . . . . . 2
4. Updating RFC 8138 . . . . . . . . . . . . . . . . . . . . . . 3 4. Updating RFC 8138 . . . . . . . . . . . . . . . . . . . . . . 3
5. Transition Scenarios . . . . . . . . . . . . . . . . . . . . 3 5. Transition Scenarios . . . . . . . . . . . . . . . . . . . . 3
5.1. Inconsistent State While Migrating . . . . . . . . . . . 4 5.1. Inconsistent State While Migrating . . . . . . . . . . . 5
5.2. Single Instance Scenario . . . . . . . . . . . . . . . . 5 5.2. Single RPL Instance Scenario . . . . . . . . . . . . . . 5
5.3. Double Instance 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 . . . . . . . . . . . . . . . . . . . 7 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 to [RFC8138] in a network can only be done when all
nodes support the specification. In a mixed case with both nodes support the specification. In a mixed case with both
RFC8138-capable and non-capable nodes, the compression should be RFC8138-capable and non-capable nodes, the compression should be
turned off. turned off.
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 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. When the bit is not set, source
nodes that support RFC 8138 should refrain from using the compression nodes that support RFC 8138 should refrain from using the compression
unless the information is superseded by configuration. unless the information is superseded by configuration.
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.
skipping to change at page 3, line 41 skipping to change at page 3, line 41
The decision of using RFC 8138 to compress a packet is made at the The decision of using RFC 8138 to compress a packet is made at the
source depending on its capabilities and its knowledge of the state source depending on its capabilities and its knowledge of the state
of the "T" flag. A router MUST forward the packet in the form that of the "T" flag. A router MUST forward the packet in the form that
the source used, either compressed or uncompressed. A router that the source used, either compressed or uncompressed. A router that
encapsulates a packet is the source of the resulting packet and the encapsulates a packet is the source of the resulting packet and the
rules above apply to it in that case. rules above apply to it in that case.
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 an 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
implicitely 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 a node
that supports this specification in a network with RFC 8138 that supports this specification in a network with RFC 8138
compression turned off. But it cannot forward compressed packets and compression turned off. But it cannot forward compressed packets and
therefore it cannot act as a router in a network with RFC 8138 therefore it cannot act as a router in a network with RFC 8138
compression turned on. It may remain connected to that network as a compression turned on. It may remain connected to that network as a
leaf and generate uncompressed packets as long as imcoming packets leaf and generate uncompressed packets. The leaf can receive packets
are decapsulated by the parent and delivered in uncompressed form. if they are delivered by the parent 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". In other words, the configuration option is a way for the
root to configure the LLN nodes but it cannot be used by a parent to root to configure the LLN nodes but it cannot be used by a parent to
advertise its capabilities down the DODAG. It results whether a advertise its capabilities down the DODAG. A parent propagates the
parent supports RFC 8138 is not known by the child with the current "T" flag as set whether it supports RFC 8138 or not. The setting of
level of specifications, and a child cannot favor a parent based on a the "T" flag can thus not be used as an indication of the support by
particular support. 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 attach to a DODAG as a leaf node only, e.g., when a 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. But the node is also other parameters in the configuration option. [USEofRPLinfo]
free to refrain from joining an Instance when a parameter is not indicates that the node may also join as a RUL, in which case it
suitable. This means that changing the OCP in a DODAG can be used to refrains from participating to RPL and depends on the 6LR to ensure
force nodes that do not support a particular feature to join as leaf connectivity regardless on the way the RPL network is operated.
only. This specification reiterates that a node that is configured
to operate in an Instance but does not support a value for a known This means that changing the OCP in a DODAG can be used to force
nodes that do not support a particular feature to join as leaf only.
This specification reiterates that a node that is configured to
operate in a RPL Instance but does not support a value for a known
parameter that is mandatory for routing MUST NOT operate as a router parameter that is mandatory for routing MUST NOT operate as a router
but MAY still joins as a leaf. Note that a legacy node will not but MAY still join as a leaf. Note that a legacy node will not
recognize when a reserved field is now used and will not turn to a recognize when a reserved field is now used and will not turn to a
leaf when that happens. leaf when that happens.
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. Some nodes will see the flag and start sourcing
packets in the compressed form while other nodes in the same instance packets in the compressed form while other nodes in the same RPL
are still not aware of it. Conversely, in non-storing mode, the root Instance are still not aware of it. Conversely, in non-storing mode,
will start using RFC 8138 with a SRH-6LoRH that routes all the way to the root will start using RFC 8138 with a SRH-6LoRH that routes all
the last router or possibly to the leaf, if the leaf supports RFC the way to the last router or possibly to the leaf, if the leaf
8138. supports RFC 8138.
This is why it is required that all the routers in the Instance This is why it is required that all the routers in the RPL Instance
support [RFC8138] at the time of the switch, and all nodes that do support [RFC8138] at the time of the switch, and all nodes that do
not support [RFC8138] only operate as leaves. 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 Instance Scenario 5.2. Single RPL Instance Scenario
In a single instance scenario, nodes that support RFC 8138 are In a Single RPL Instance Scenario, nodes that support RFC 8138 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. when it finally sets the "T" flag, the root also variation of it. The root sets the "T" flag at the time it migrates
migrates to the new OCP. As a result, nodes that do not support RFC to the new OCP. As a result, nodes that do not support RFC 8138 join
8138 join as leaves and do not forward packets anymore. The leaves as leaves and do not forward packets anymore. The leaves generate
generate packets without compression. The parents - which supports packets without compression. The parents - which supports RFC 8138 -
RFC 8138 - may encapsulate the packets using RFC 8138 if needed. The may encapsulate the packets using RFC 8138 if needed. The other way
other way around, the root encapsulates packets to the leaves all the around, the root encapsulates packets to the leaves all the way to
way to the parent, which decapsulates and distribute the uncompresses the parent, which decapsulates and distribute the uncompressed inner
inner packet to the leaf. packet to the leaf.
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 requires a means to
signal the capabilities of the leaf, e.g., using "RPL Mode of signal the capabilities of the leaf, e.g., using "RPL Mode of
Operation extension" [MOP-EXT]. Operation extension" [MOP-EXT].
* If an implementation does not move to a leaf mode when the OCP is * If an implementation does not move to a leaf mode when the OCP is
changed to an unknown one, then the node may be stalled. 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 RFC 8138, 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 * Nodes that only support RFC8138 for forwarding may not parse the
RPI in native form. If such nodes are present, the parent needs RPI in native form. If such nodes are present, the parent needs
to encapsulate with RFC8138. to encapsulate with RFC8138.
5.3. Double Instance Scenario 5.3. Double RPL Instances Scenario
An alternate to the Single Instance Scenario is to deploy an An alternate to the Single RPL Instance Scenario is to deploy an
additional Instance for the nodes that support [RFC8138]. The two additional RPL Instance for the nodes that support [RFC8138]. The
instances operate as ships-in-the-night as specified in [RFC6550]. two RPL Instances operate independently as specified in [RFC6550].
The preexisting Instance that does not use [RFC8138], whereas the new The preexisting RPL Instance that does not use [RFC8138], whereas the
Instance does. This is signaled by the "T" flag which is only set in new RPL Instance does. This is signaled by the "T" flag which is
the configuration option in DIO messages in the new Instance. 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 Nodes that support RFC 8138 participate to both Instances but favor
the new Instance for the traffic that they source. On the other the new RPL Instance for the traffic that they source. On the other
hand, nodes that only support the uncompressed format would either hand, nodes that only support the uncompressed format would either
not be configured for the new instance, or would be configured to not be configured for the new RPL Instance, or would be configured to
join it as leaves only. 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 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
the "T" flag reset before allowing nodes that do not support the the "T" flag reset before allowing nodes that do not support the
compression in the network (see caveats in Section 5.2). compression in the network (see caveats in Section 5.2).
It is RECOMMENDED to only deploy nodes that support [RFC8138] in a It is RECOMMENDED to only deploy nodes that support [RFC8138] in a
network where the compression is turned on. A node that does not network where the compression is turned on. A node that does not
skipping to change at page 7, line 41 skipping to change at page 7, line 49
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>.
[USEofRPLinfo]
Robles, I., Richardson, M., and P. Thubert, "Using RPI
Option Type, Routing Header for Source Routes and IPv6-in-
IPv6 encapsulation in the RPL Data Plane", Work in
Progress, Internet-Draft, draft-ietf-roll-useofrplinfo-34,
20 January 2020, <https://tools.ietf.org/html/draft-ietf-
roll-useofrplinfo-34>.
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
2019, <https://tools.ietf.org/html/draft-ietf-roll-mopex- 2019, <https://tools.ietf.org/html/draft-ietf-roll-mopex-
cap-01>. cap-01>.
Authors' Addresses Authors' Addresses
Pascal Thubert (editor) Pascal Thubert (editor)
Cisco Systems, Inc Cisco Systems, Inc
Building D, 45 Allee des Ormes - BP1200 Building D
45 Allee des Ormes - BP1200
06254 MOUGINS - Sophia Antipolis 06254 MOUGINS - Sophia Antipolis
France France
Phone: +33 497 23 26 34 Phone: +33 497 23 26 34
Email: pthubert@cisco.com Email: pthubert@cisco.com
Li Zhao Li Zhao
Cisco Systems, Inc Cisco Systems, Inc
Xinsi Building, No. 926 Yi Shan Rd Xinsi Building
No. 926 Yi Shan Rd
SHANGHAI SHANGHAI
200233 200233
China China
Email: liz3@cisco.com Email: liz3@cisco.com
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