< draft-thubert-roll-turnon-rfc8138-01.txt   draft-thubert-roll-turnon-rfc8138-02.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 May 29, 2019 Intended status: Standards Track July 3, 2019
Expires: November 30, 2019 Expires: January 4, 2020
Configuration option for RFC 8138 Configuration option for RFC 8138
draft-thubert-roll-turnon-rfc8138-01 draft-thubert-roll-turnon-rfc8138-02
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
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 November 30, 2019. This Internet-Draft will expire on January 4, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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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 imcomping packets leaf and generate uncompressed packets as long as imcoming packets
are decapsulated by the parent and delivered in uncompressed form. are decapsulated by the parent and delivered in uncompressed form.
[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. It results whether a
parent supportqs RFC 8138 is not known by the child with the current parent supports RFC 8138 is not known by the child with the current
level of specifications, and a child cannot favor a parent based on a level of specifications, and a child cannot favor a parent based on a
particular support. particular support.
[RFC6550] also suggests that a RPL node may attach to a DODAG as a Sections 8.5 and 9.2 of [RFC6550] also suggests that a RPL-aware node
leaf node only, e.g., when a node does not support the RPL Instance's may attach to a DODAG as a leaf node only, e.g., when a node does not
Objective Function (OF) as indicated by the Objective Code Point support the Mode of Operation of a RPL Instance, the Objective
(OCP) in the configuration option. But the node is also free to Function (OF) as indicated by the Objective Code Point (OCP) or some
refrain from joining an Instance when a parameter is not suitable. other parameters in the configuration option. But the node is also
This means that changing the OCP in a DODAG can be used to force free to refrain from joining an Instance when a parameter is not
nodes that do not support a particular feature to join as leaf only, suitable. This means that changing the OCP in a DODAG can be used to
but the method is not guaranteed to work with all implementations. force nodes that do not support a particular feature to join as leaf
With this specification, it is now RECOMMENDED that a node that is only. This specification reiterates that a node that is configured
configured to operate in an Instance but does not recognize a to operate in an Instance but does not support a value for a known
parameter that is mandatory for routing still joins as a leaf. 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
recognize when a reserved field is now used and will not turn to a
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 wihtout 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 instance
are still not aware of it. Conversely, in non-storing mode, the root 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 will start using RFC 8138 with a SRH-6LoRH that routes all the way to
the last router or to the leaf, depending on its support. 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 Instance This is why it is required that all the routers in the 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
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the configuration option in DIO messages in the new Instance. the configuration option in DIO messages in the new 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 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 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 mamangement capabilities to least two RPL Instances and demands management capabilities to
introduce new Instances and deprecate old ones. introduce new 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 to the "T" flag reset before allowing nodes that do not support the "T" flag reset before allowing nodes that do not support the
[RFC8138] 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
support [RFC8138] MUST be used only as a leaf. support [RFC8138] MUST only be used as a leaf.
6. IANA Considerations 6. IANA Considerations
This specification updates the "Registry for the DODAG Configuration This specification updates the "Registry for the DODAG Configuration
Option Flags" that was created for [RFC6550] as follows: Option Flags" that was created for [RFC6550] as follows:
+---------------+---------------------------------+----------------+ +---------------+---------------------------------+----------------+
| Bit Number | Meaning | Defining Spec | | Bit Number | Meaning | Defining Spec |
+---------------+---------------------------------+----------------+ +---------------+---------------------------------+----------------+
| 2 (suggested) | Turn on RFC8138 Compression (T) | This | | 2 (suggested) | Turn on RFC8138 Compression (T) | This |
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<https://www.rfc-editor.org/info/rfc6550>. <https://www.rfc-editor.org/info/rfc6550>.
[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>.
9.2. Informative References 9.2. Informative References
[I-D.rahul-roll-mop-ext] [I-D.rahul-roll-mop-ext]
Jadhav, R. and P. Thubert, "RPL Mode of Operation Jadhav, R. and P. Thubert, "RPL Mode of Operation
extension", draft-rahul-roll-mop-ext-00 (work in extension", draft-rahul-roll-mop-ext-01 (work in
progress), February 2019. progress), June 2019.
[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>.
Authors' Addresses Authors' Addresses
Pascal Thubert (editor) Pascal Thubert (editor)
Cisco Systems, Inc Cisco Systems, Inc
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