draft-ietf-roll-efficient-npdao-10.txt   draft-ietf-roll-efficient-npdao-11.txt 
ROLL R. Jadhav, Ed. ROLL R. Jadhav, Ed.
Internet-Draft Huawei Internet-Draft Huawei
Intended status: Standards Track P. Thubert Intended status: Standards Track P. Thubert
Expires: October 29, 2019 Cisco Expires: November 26, 2019 Cisco
R. Sahoo R. Sahoo
Z. Cao Z. Cao
Huawei Huawei
April 27, 2019 May 25, 2019
Efficient Route Invalidation Efficient Route Invalidation
draft-ietf-roll-efficient-npdao-10 draft-ietf-roll-efficient-npdao-11
Abstract Abstract
This document describes the problems associated with No-Path This document describes the problems associated with No-Path
Destination Advertisement Object (NPDAO) messaging used in Routing Destination Advertisement Object (NPDAO) messaging used in Routing
Protocol for Low power and lossy networks (RPL) for route Protocol for Low power and lossy networks (RPL) for route
invalidation and signaling changes to improve route invalidation invalidation and signaling changes to improve route invalidation
efficiency. efficiency.
Status of This Memo Status of This Memo
skipping to change at page 1, line 38 skipping to change at page 1, line 38
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 October 29, 2019. This Internet-Draft will expire on November 26, 2019.
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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include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language and Terminology . . . . . . . . . . 3 1.1. Requirements Language and Terminology . . . . . . . . . . 3
1.2. Current NPDAO messaging . . . . . . . . . . . . . . . . . 4 1.2. Current NPDAO messaging . . . . . . . . . . . . . . . . . 4
1.3. Why NPDAO is important? . . . . . . . . . . . . . . . . . 5 1.3. Why NPDAO is important? . . . . . . . . . . . . . . . . . 5
2. Problems with current NPDAO messaging . . . . . . . . 6 2. Problems with current NPDAO messaging . . . . . . . . . . . . 6
2.1. Lost NPDAO due to link break to the previous parent . . . 6 2.1. Lost NPDAO due to link break to the previous parent . . . 6
2.2. Invalidate routes of dependent nodes . . . . . . . . . . 6 2.2. Invalidate routes of dependent nodes . . . . . . . . . . 6
2.3. Possible route downtime caused by async operation of 2.3. Possible route downtime caused by async operation of
NPDAO and DAO . . . . . . . . . . . . . . . . . . . . . . 6 NPDAO and DAO . . . . . . . . . . . . . . . . . . . . . . 6
3. Requirements for the NPDAO Optimization . . . . . . . . . . . 6 3. Requirements for the NPDAO Optimization . . . . . . . . . . . 6
3.1. Req#1: Remove messaging dependency on link to the 3.1. Req#1: Remove messaging dependency on link to the
previous parent . . . . . . . . . . . . . . . 6 previous parent . . . . . . . . . . . . . . . . . . . . . 6
3.2. Req#2: Dependent nodes route invalidation on parent 3.2. Req#2: Dependent nodes route invalidation on parent
switching . . . . . . . . . . . . . . . . . . . . . . . . 7 switching . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3. Req#3: Route invalidation should not impact data traffic 7 3.3. Req#3: Route invalidation should not impact data traffic 7
4. Changes to RPL signaling . . . . . . . . . . . . . . . . . . 7 4. Changes to RPL signaling . . . . . . . . . . . . . . . . . . 7
4.1. Change in RPL route invalidation semantics . . . . . . . 7 4.1. Change in RPL route invalidation semantics . . . . . . . 7
4.2. Transit Information Option changes . . . . . . . . . . . 8 4.2. Transit Information Option changes . . . . . . . . . . . 8
4.3. Destination Cleanup Object (DCO) . . . . . . . . . . . . 9 4.3. Destination Cleanup Object (DCO) . . . . . . . . . . . . 9
4.3.1. Secure DCO . . . . . . . . . . . . . . . . . . . . . 10 4.3.1. Secure DCO . . . . . . . . . . . . . . . . . . . . . 10
4.3.2. DCO Options . . . . . . . . . . . . . . . . . . . . . 10 4.3.2. DCO Options . . . . . . . . . . . . . . . . . . . . . 10
4.3.3. Path Sequence number in the DCO . . . . . . . . . . . 10 4.3.3. Path Sequence number in the DCO . . . . . . . . . . . 10
4.3.4. Destination Cleanup Option Acknowledgement (DCO-ACK) 11 4.3.4. Destination Cleanup Option Acknowledgment (DCO-ACK) . 10
4.3.5. Secure DCO-ACK . . . . . . . . . . . . . . . . . . . 12 4.3.5. Secure DCO-ACK . . . . . . . . . . . . . . . . . . . 11
4.4. DCO Base Rules . . . . . . . . . . . . . . . . . . . . . 12 4.4. DCO Base Rules . . . . . . . . . . . . . . . . . . . . . 12
4.5. Other considerations . . . . . . . . . . . . . . . . . . 12 4.5. Unsolicited DCO . . . . . . . . . . . . . . . . . . . . . 12
4.5.1. Dependent Nodes invalidation . . . . . . . . . . . . 12 4.6. Other considerations . . . . . . . . . . . . . . . . . . 13
4.5.2. NPDAO and DCO in the same network . . . . . . . . . . 13 4.6.1. Dependent Nodes invalidation . . . . . . . . . . . . 13
4.5.3. DCO with multiple preferred parents . . . . . . . . . 13 4.6.2. NPDAO and DCO in the same network . . . . . . . . . . 13
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 4.6.3. DCO with multiple preferred parents . . . . . . . . . 14
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
6.1. New Registry for the Destination Cleanup Object (DCO) 6.1. New Registry for the Destination Cleanup Object (DCO)
Flags . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Flags . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.2. New Registry for the Destination Cleanup Object 6.2. New Registry for the Destination Cleanup Object
Acknowledgement (DCO-ACK) Status field . . . . . . . . . 15 Acknowledgment (DCO-ACK) Status field . . . . . . . . . . 16
6.3. New Registry for the Destination Cleanup Object (DCO) 6.3. New Registry for the Destination Cleanup Object (DCO)
Acknowledgement Flags . . . . . . . . . . . . . . . . . . 16 Acknowledgment Flags . . . . . . . . . . . . . . . . . . 16
7. Security Considerations . . . . . . . . . . . . . . . . . . . 16 7. Security Considerations . . . . . . . . . . . . . . . . . . . 17
8. Normative References . . . . . . . . . . . . . . . . . . . . 17 8. Normative References . . . . . . . . . . . . . . . . . . . . 18
Appendix A. Example Messaging . . . . . . . . . . . . . . . . . 18 Appendix A. Example Messaging . . . . . . . . . . . . . . . . . 18
A.1. Example DCO Messaging . . . . . . . . . . . . . . . . . . 18 A.1. Example DCO Messaging . . . . . . . . . . . . . . . . . . 18
A.2. Example DCO Messaging with multiple preferred parents . . 19 A.2. Example DCO Messaging with multiple preferred parents . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction 1. Introduction
RPL [RFC6550] (Routing Protocol for Low power and lossy networks) RPL [RFC6550] (Routing Protocol for Low power and lossy networks)
specifies a proactive distance-vector based routing scheme. RPL has specifies a proactive distance-vector based routing scheme. RPL has
an optional messaging in the form of DAO (Destination Advertisement an optional messaging in the form of DAO (Destination Advertisement
Object) messages, which the 6LBR (6Lo Border Router) and 6LR (6Lo Object) messages, which the 6LBR (6Lo Border Router) and 6LR (6Lo
Router) can use to learn a route towards the downstream nodes. In Router) can use to learn a route towards the downstream nodes. In
storing mode, DAO messages would result in routing entries being storing mode, DAO messages would result in routing entries being
created on all intermediate 6LRs from the node's parent all the way created on all intermediate 6LRs from the node's parent all the way
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In Figure 1, when node D decides to switch the path from B to C, it In Figure 1, when node D decides to switch the path from B to C, it
sends a regular DAO to node C with reachability information sends a regular DAO to node C with reachability information
containing target as address of D and an incremented Path Sequence. containing target as address of D and an incremented Path Sequence.
Node C will update the routing table based on the reachability Node C will update the routing table based on the reachability
information in the DAO and in turn generate another DAO with the same information in the DAO and in turn generate another DAO with the same
reachability information and forward it to H. Node H also follows reachability information and forward it to H. Node H also follows
the same procedure as Node C and forwards it to node A. When node A the same procedure as Node C and forwards it to node A. When node A
receives the regular DAO, it finds that it already has a routing receives the regular DAO, it finds that it already has a routing
table entry on behalf of the target address of node D. It finds table entry on behalf of the target address of node D. It finds
however that the next hop information for reaching node D has changed however that the next hop information for reaching node D has changed
i.e. node D has decided to change the paths. In this case, Node A i.e., node D has decided to change the paths. In this case, Node A
which is the common ancestor node for node D along the two paths which is the common ancestor node for node D along the two paths
(previous and new), should generate a DCO which traverses downwards (previous and new), should generate a DCO which traverses downwards
in the network. in the network.
4.2. Transit Information Option changes 4.2. Transit Information Option changes
Every RPL message is divided into base message fields and additional Every RPL message is divided into base message fields and additional
Options as described in Section 6 of [RFC6550]. The base fields Options as described in Section 6 of [RFC6550]. The base fields
apply to the message as a whole and options are appended to add apply to the message as a whole and options are appended to add
message/use-case specific attributes. As an example, a DAO message message/use-case specific attributes. As an example, a DAO message
may be attributed by one or more "RPL Target" options which specify may be attributed by one or more "RPL Target" options which specify
the reachability information for the given targets. Similarly, a the reachability information for the given targets. Similarly, a
Transit Information option may be associated with a set of RPL Target Transit Information option may be associated with a set of RPL Target
options. options.
This document specifies a change in the Transit Information Option to This document specifies a change in the Transit Information Option to
contain the "Invalidate previous route" (I) bit. This I-bit signals contain the "Invalidate previous route" (I) flag. This I-flag
the common ancestor node to generate a DCO on behalf of the target signals the common ancestor node to generate a DCO on behalf of the
node. The I-bit is carried in the Transit Information Option which target node. The I-flag is carried in the Transit Information Option
augments the reachability information for a given set of RPL which augments the reachability information for a given set of RPL
Target(s). Transit Information Option should be carried in the DAO Target(s). Transit Information Option should be carried in the DAO
message with I-bit set in case route invalidation is sought for the message with I-flag set in case route invalidation is sought for the
corresponding target(s). corresponding target(s).
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0x06 | Option Length |E|I| Flags | Path Control | | Type = 0x06 | Option Length |E|I| Flags | Path Control |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Path Sequence | Path Lifetime | | | Path Sequence | Path Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
+ +
| |
+ Parent Address +
| |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Updated Transit Information Option (New I flag added) Figure 2: Updated Transit Information Option (New I flag added)
I (Invalidate previous route) bit: The 'I' flag is set by the target I (Invalidate previous route) flag: The 'I' flag is set by the target
node to indicate to the common ancestor node that it wishes to node to indicate to the common ancestor node that it wishes to
invalidate any previous route between the two paths. invalidate any previous route between the two paths.
[RFC6550] allows parent address to be sent in the Transit Information
Option depending on the mode of operation. In case of storing mode
of operation the field is usually not needed. In case of DCO, the
parent address field MUST not be included.
The common ancestor node SHOULD generate a DCO message in response to The common ancestor node SHOULD generate a DCO message in response to
this I-bit when it sees that the routing adjacencies have changed for this I-flag when it sees that the routing adjacencies have changed
the target. I-bit governs the ownership of the DCO message in a way for the target. I-flag governs the ownership of the DCO message in a
that the target node is still in control of its own route way that the target node is still in control of its own route
invalidation. invalidation.
4.3. Destination Cleanup Object (DCO) 4.3. Destination Cleanup Object (DCO)
A new ICMPv6 RPL control message type is defined by this A new ICMPv6 RPL control message type is defined by this
specification called as "Destination Cleanup Object" (DCO), which is specification called as "Destination Cleanup Object" (DCO), which is
used for proactive cleanup of state and routing information held on used for proactive cleanup of state and routing information held on
behalf of the target node by 6LRs. The DCO message always traverses behalf of the target node by 6LRs. The DCO message always traverses
downstream and cleans up route information and other state downstream and cleans up route information and other state
information associated with the given target. information associated with the given target.
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in order to identify the DODAGID that is associated with the in order to identify the DODAGID that is associated with the
RPLInstanceID. RPLInstanceID.
4.3.1. Secure DCO 4.3.1. Secure DCO
A Secure DCO message follows the format in [RFC6550] Figure 7, where A Secure DCO message follows the format in [RFC6550] Figure 7, where
the base message format is the DCO message shown in Figure 3. the base message format is the DCO message shown in Figure 3.
4.3.2. DCO Options 4.3.2. DCO Options
The DCO message MUST carry atleast one RPL Target and the Transit The DCO message MUST carry at least one RPL Target and the Transit
Information Option and MAY carry other valid options. This Information Option and MAY carry other valid options. This
specification allows for the DCO message to carry the following specification allows for the DCO message to carry the following
options: options:
0x00 Pad1 0x00 Pad1
0x01 PadN 0x01 PadN
0x05 RPL Target 0x05 RPL Target
0x06 Transit Information 0x06 Transit Information
0x09 RPL Target Descriptor 0x09 RPL Target Descriptor
The DCO carries an RPL Target Option and an associated Transit The DCO carries an RPL Target Option and an associated Transit
Information Option with a lifetime of 0x00000000 to indicate a loss Information Option with a lifetime of 0x00000000 to indicate a loss
of reachability to that Target. The lifetime indicated in the of reachability to that Target.
Transit Information Option of the DCO message MUST be set to
0x00000000.
4.3.3. Path Sequence number in the DCO 4.3.3. Path Sequence number in the DCO
A DCO message may contain a Path Sequence in the Transit Information A DCO message may contain a Path Sequence in the Transit Information
Option to identify the freshness of the DCO message. The Path Option to identify the freshness of the DCO message. The Path
Sequence in the DCO MUST use the same Path Sequence number present in Sequence in the DCO MUST use the same Path Sequence number present in
the regular DAO message when the DCO is generated in response to a the regular DAO message when the DCO is generated in response to a
DAO message. The Path Sequence present in the Transit Information DAO message. Thus if a DCO is received by a 6LR and subsequently a
Option of the DAO and the correspondingly triggered DCO MUST be same. DAO is received with an old seqeunce number, then the DAO MUST be
Thus if a DCO is received by a 6LR and subsequently a DAO is received ignored.
with an old seqeunce number, then the DAO MUST be ignored.
4.3.4. Destination Cleanup Option Acknowledgement (DCO-ACK) 4.3.4. Destination Cleanup Option Acknowledgment (DCO-ACK)
The DCO-ACK message SHOULD be sent as a unicast packet by a DCO The DCO-ACK message SHOULD be sent as a unicast packet by a DCO
recipient in response to a unicast DCO message with 'K' flag set. If recipient in response to a unicast DCO message with 'K' flag set. If
'K' flag is not set then the receiver of the DCO message MAY send a 'K' flag is not set then the receiver of the DCO message MAY send a
DCO-ACK to signal an error condition. DCO-ACK to signal an error condition.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RPLInstanceID |D| Reserved | DCOSequence | Status | | RPLInstanceID |D| Reserved | DCOSequence | Status |
skipping to change at page 12, line 29 skipping to change at page 12, line 23
same value as that of the DAO message in response to which the same value as that of the DAO message in response to which the
DCO is generated on the common ancestor node. DCO is generated on the common ancestor node.
3. A node MAY set the 'K' flag in a unicast DCO message to solicit a 3. A node MAY set the 'K' flag in a unicast DCO message to solicit a
unicast DCO-ACK in response in order to confirm the attempt. unicast DCO-ACK in response in order to confirm the attempt.
4. A node receiving a unicast DCO message with the 'K' flag set 4. A node receiving a unicast DCO message with the 'K' flag set
SHOULD respond with a DCO-ACK. A node receiving a DCO message SHOULD respond with a DCO-ACK. A node receiving a DCO message
without the 'K' flag set MAY respond with a DCO-ACK, especially without the 'K' flag set MAY respond with a DCO-ACK, especially
to report an error condition. to report an error condition.
5. A node receiving a unicast DCO message MUST verify the stored 5. A node receiving a unicast DCO message MUST verify the stored
Path Sequence in context to the given target. If the stored Path Path Sequence in context to the given target. If the stored Path
Sequence is more fresh i.e. newer than the Path Sequence received Sequence is more fresh i.e., newer than the Path Sequence
in the DCO, then the DCO MUST be dropped. received in the DCO, then the DCO MUST be dropped.
6. A node that sets the 'K' flag in a unicast DCO message but does 6. A node that sets the 'K' flag in a unicast DCO message but does
not receive DCO-ACK in response MAY reschedule the DCO message not receive DCO-ACK in response MAY reschedule the DCO message
transmission for another attempt, up until an implementation transmission for another attempt, up until an implementation
specific number of retries. specific number of retries.
7. A node receiving a unicast DCO message with its own address in 7. A node receiving a unicast DCO message with its own address in
the RPL Target Option MUST strip-off that Target Option. If this the RPL Target Option MUST strip-off that Target Option. If this
Target Option is the only one in the DCO message then the DCO Target Option is the only one in the DCO message then the DCO
message MUST be dropped. message MUST be dropped.
The scope of DCOSequence values is unique to each node. The scope of DCOSequence values is unique to each node.
4.5. Other considerations 4.5. Unsolicited DCO
4.5.1. Dependent Nodes invalidation A 6LR may generate an unsolicited DCO to unilaterally cleanup the
path on behalf of the target entry. The 6LR has all the state
information namely, the Target address and the Path Sequence,
required for generating DCO in its routing table. The conditions why
6LR may generate an unsolicited DCO is beyond the scope of this
document but some possible reasons could be:
1. On route expiry of an entry, a 6LR may decide to gracious cleanup
the entry by initiating DCO.
2. 6LR needs to entertain higher priority entries in case the
routing table is full thus resulting in an eviction of existing
routing entry. In this case the eviction can be handled
graciously using DCO.
Note that if the 6LR initiates a unilateral path cleanup using DCO
and if it has the latest state for the target then the DCO would
finally reach the target node. Thus the target node would be
informed of its invalidation.
4.6. Other considerations
4.6.1. Dependent Nodes invalidation
Current RPL [RFC6550] does not provide a mechanism for route Current RPL [RFC6550] does not provide a mechanism for route
invalidation for dependent nodes. This document allows the dependent invalidation for dependent nodes. This document allows the dependent
nodes invalidation. Dependent nodes will generate their respective nodes invalidation. Dependent nodes will generate their respective
DAOs to update their paths, and the previous route invalidation for DAOs to update their paths, and the previous route invalidation for
those nodes should work in the similar manner described for switching those nodes should work in the similar manner described for switching
node. The dependent node may set the I-bit in the Transit node. The dependent node may set the I-flag in the Transit
Information Option as part of regular DAO so as to request Information Option as part of regular DAO so as to request
invalidation of previous route from the common ancestor node. invalidation of previous route from the common ancestor node.
Dependent nodes do not have any indication regarding if any of its Dependent nodes do not have any indication regarding if any of its
parent nodes in turn have decided to switch their parent. Thus for parent nodes in turn have decided to switch their parent. Thus for
route invalidation the dependent nodes may choose to always set the route invalidation the dependent nodes may choose to always set the
'I' bit in all its DAO message's Transit Information Option. Note 'I' flag in all its DAO message's Transit Information Option. Note
that setting the I-bit is not counter productive even if there is no that setting the I-flag is not counter productive even if there is no
previous route to be invalidated. previous route to be invalidated.
4.5.2. NPDAO and DCO in the same network 4.6.2. NPDAO and DCO in the same network
Even with the changed semantics, the current NPDAO mechanism in Even with the changed semantics, the current NPDAO mechanism in
[RFC6550] can still be used, for example, when the route lifetime [RFC6550] can still be used, for example, when the route lifetime
expiry of the target happens or when the node simply decides to expiry of the target happens or when the node simply decides to
gracefully terminate the RPL session on graceful node shutdown. gracefully terminate the RPL session on graceful node shutdown.
Moreover a deployment can have a mix of nodes supporting the DCO and Moreover a deployment can have a mix of nodes supporting the DCO and
the existing NPDAO mechanism. It is also possible that the same node the existing NPDAO mechanism. It is also possible that the same node
supports both the NPDAO and DCO signalling. supports both the NPDAO and DCO signaling.
Section 9.8 of [RFC6550] states, "When a node removes a node from its Section 9.8 of [RFC6550] states, "When a node removes a node from its
DAO parent set, it SHOULD send a No-Path DAO message to that removed DAO parent set, it SHOULD send a No-Path DAO message to that removed
DAO parent to invalidate the existing router". This document DAO parent to invalidate the existing router". This document
introduces an alternate and more optimized way of route invalidation introduces an alternate and more optimized way of route invalidation
but it also allows existing NPDAO messaging to work. Thus an but it also allows existing NPDAO messaging to work. Thus an
implementation has two choices to make when a route invalidation is implementation has two choices to make when a route invalidation is
to be initiated: to be initiated:
1. Use NPDAO to invalidate the previous route and send regular DAO 1. Use NPDAO to invalidate the previous route and send regular DAO
on the new path. on the new path.
2. Send regular DAO on the new path with the 'I' bit set in the 2. Send regular DAO on the new path with the 'I' flag set in the
Transit Information Option such that the common ancestor node Transit Information Option such that the common ancestor node
initiates the DCO message downstream to invalidate the previous initiates the DCO message downstream to invalidate the previous
route. route.
This document recommends using option 2 for reasons specified in This document recommends using option 2 for reasons specified in
Section 3 in this document. Section 3 in this document.
4.5.3. DCO with multiple preferred parents 4.6.3. DCO with multiple preferred parents
[RFC6550] allows a node to select multiple preferred parents for [RFC6550] allows a node to select multiple preferred parents for
route establishment. Section 9.2.1 of [RFC6550] specifies, "All DAOs route establishment. Section 9.2.1 of [RFC6550] specifies, "All DAOs
generated at the same time for the same Target MUST be sent with the generated at the same time for the same Target MUST be sent with the
same Path Sequence in the Transit Information". Subsequently when same Path Sequence in the Transit Information". Subsequently when
route invalidation has to be initiated, RPL mentions use of NPDAO route invalidation has to be initiated, RPL mentions use of NPDAO
which can be initiated with an updated Path Sequence to all the which can be initiated with an updated Path Sequence to all the
parent nodes through which the route is to be invalidated. parent nodes through which the route is to be invalidated.
With DCO, the Target node itself does not initiate the route With DCO, the Target node itself does not initiate the route
skipping to change at page 14, line 28 skipping to change at page 14, line 43
This documents recommends using a DelayDCO timer value of 1sec. This This documents recommends using a DelayDCO timer value of 1sec. This
value is inspired by the default DelayDAO value of 1sec in [RFC6550]. value is inspired by the default DelayDAO value of 1sec in [RFC6550].
Here the hypothesis is that the DAOs from all possible parent set Here the hypothesis is that the DAOs from all possible parent set
would be received on the common ancestor within this time period. would be received on the common ancestor within this time period.
Note that there is no requirement of synchronization between DCO and Note that there is no requirement of synchronization between DCO and
DAOs. The DelayDCO timer simply ensures that the DCO control DAOs. The DelayDCO timer simply ensures that the DCO control
overhead can be reduced and is only needed when the network contains overhead can be reduced and is only needed when the network contains
nodes using multiple preferred parent. nodes using multiple preferred parent.
5. Acknowledgements 5. Acknowledgments
Many thanks to Alvaro Retana, Cenk Gundogan, Simon Duquennoy, Many thanks to Alvaro Retana, Cenk Gundogan, Simon Duquennoy,
Georgios Papadopoulous, Peter Van Der Stok for their review and Georgios Papadopoulous, Peter Van Der Stok for their review and
comments. Alvaro Retana helped shape this document's final version comments. Alvaro Retana helped shape this document's final version
with critical review comments. with critical review comments.
6. IANA Considerations 6. IANA Considerations
IANA is requested to allocate new codes for the DCO and DCO-ACK IANA is requested to allocate new codes for the DCO and DCO-ACK
messages from the RPL Control Codes registry. messages from the RPL Control Codes registry.
+------+---------------------------------------------+--------------+ +------+---------------------------------------------+--------------+
| Code | Description | Reference | | Code | Description | Reference |
+------+---------------------------------------------+--------------+ +------+---------------------------------------------+--------------+
| TBD1 | Destination Cleanup Object | This | | TBD1 | Destination Cleanup Object | This |
| | | document | | | | document |
| TBD2 | Destination Cleanup Object Acknowledgement | This | | TBD2 | Destination Cleanup Object Acknowledgment | This |
| | | document | | | | document |
| TBD3 | Secure Destination Cleanup Object | This | | TBD3 | Secure Destination Cleanup Object | This |
| | | document | | | | document |
| TBD4 | Secure Destination Cleanup Object | This | | TBD4 | Secure Destination Cleanup Object | This |
| | Acknowledgement | document | | | Acknowledgment | document |
+------+---------------------------------------------+--------------+ +------+---------------------------------------------+--------------+
IANA is requested to allocate bit 1 from the Transit Information IANA is requested to allocate bit 1 from the Transit Information
Option Flags registry for the I-bit (Section 4.2) Option Flags registry for the I-flag (Section 4.2)
6.1. New Registry for the Destination Cleanup Object (DCO) Flags 6.1. New Registry for the Destination Cleanup Object (DCO) Flags
IANA has created a registry for the 8-bit Destination Cleanup Object IANA is requested to create a registry for the 8-bit Destination
(DCO) Flags field. Cleanup Object (DCO) Flags field. This registry should be located in
existing category of "Routing Protocol for Low Power and Lossy
Networks (RPL)".
New bit numbers may be allocated only by an IETF Review. Each bit is New bit numbers may be allocated only by an IETF Review. Each bit is
tracked with the following qualities: tracked with the following qualities:
oBit number (counting from bit 0 as the most significant bit) o Bit number (counting from bit 0 as the most significant bit)
oCapability description o Capability description
oDefining RFC o Defining RFC
The following bits are currently defined: The following bits are currently defined:
+------------+------------------------------+---------------+ +------------+------------------------------+---------------+
| Bit number | Description | Reference | | Bit number | Description | Reference |
+------------+------------------------------+---------------+ +------------+------------------------------+---------------+
| 0 | DCO-ACK request (K) | This document | | 0 | DCO-ACK request (K) | This document |
| 1 | DODAGID field is present (D) | This document | | 1 | DODAGID field is present (D) | This document |
+------------+------------------------------+---------------+ +------------+------------------------------+---------------+
DCO Base Flags DCO Base Flags
6.2. New Registry for the Destination Cleanup Object Acknowledgement 6.2. New Registry for the Destination Cleanup Object Acknowledgment
(DCO-ACK) Status field (DCO-ACK) Status field
IANA has created a registry for the 8-bit Destination Cleanup Object IANA is requested to create a registry for the 8-bit Destination
Acknowledgement (DCO-ACK) Status field. Cleanup Object Acknowledgment (DCO-ACK) Status field. This registry
should be located in existing category of "Routing Protocol for Low
Power and Lossy Networks (RPL)".
New Status values may be allocated only by an IETF Review. Each New Status values may be allocated only by an IETF Review. Each
value is tracked with the following qualities: value is tracked with the following qualities:
oStatus Code o Status Code
oDescription o Description
oDefining RFC o Defining RFC
The following bits are currently defined: The following bits are currently defined:
+------------+----------------------------------------+-------------+ +------------+----------------------------------------+-------------+
| Status | Description | Reference | | Status | Description | Reference |
| Code | | | | Code | | |
+------------+----------------------------------------+-------------+ +------------+----------------------------------------+-------------+
| 0 | Unqualified acceptance | This | | 0 | Unqualified acceptance | This |
| | | document | | | | document |
| 1 | No routing-entry for the indicated | This | | 1 | No routing-entry for the indicated | This |
| | Target found | document | | | Target found | document |
+------------+----------------------------------------+-------------+ +------------+----------------------------------------+-------------+
DCO Status Codes DCO Status Codes
6.3. New Registry for the Destination Cleanup Object (DCO) 6.3. New Registry for the Destination Cleanup Object (DCO)
Acknowledgement Flags Acknowledgment Flags
IANA has created a registry for the 8-bit Destination Cleanup Object IANA is requested to create a registry for the 8-bit Destination
(DCO) Acknowledgement Flags field. Cleanup Object (DCO) Acknowledgment Flags field. This registry
should be located in existing category of "Routing Protocol for Low
Power and Lossy Networks (RPL)".
New bit numbers may be allocated only by an IETF Review. Each bit is New bit numbers may be allocated only by an IETF Review. Each bit is
tracked with the following qualities: tracked with the following qualities:
oBit number (counting from bit 0 as the most significant bit) o Bit number (counting from bit 0 as the most significant bit)
oCapability description o Capability description
oDefining RFC o Defining RFC
The following bits are currently defined: The following bits are currently defined:
+------------+------------------------------+---------------+ +------------+------------------------------+---------------+
| Bit number | Description | Reference | | Bit number | Description | Reference |
+------------+------------------------------+---------------+ +------------+------------------------------+---------------+
| 0 | DODAGID field is present (D) | This document | | 0 | DODAGID field is present (D) | This document |
+------------+------------------------------+---------------+ +------------+------------------------------+---------------+
DCO-ACK Base Flags DCO-ACK Base Flags
7. Security Considerations 7. Security Considerations
This document introduces the ability for a common ancestor node to This document introduces the ability for a common ancestor node to
invalidate a route on behalf of the target node. The common ancestor invalidate a route on behalf of the target node. The common ancestor
node is directed to do so by the target node using the 'I' bit in node is directed to do so by the target node using the 'I' flag in
DCO's Transit Information Option. However, the common ancestor node DCO's Transit Information Option. However, the common ancestor node
is in a position to unilaterally initiate the route invalidation is in a position to unilaterally initiate the route invalidation
since it possesses all the required state information namely, the since it possesses all the required state information, namely, the
Target address and the correspond Path Sequence. Thus a rogue common Target address and the corresponding Path Sequence. Thus a rogue
ancestor node could initiate such an invalidation and impact the common ancestor node could initiate such an invalidation and impact
traffic to the target node. This document assumes that the security the traffic to the target node.
mechanisms as defined in [RFC6550] are followed, which means that the
common ancestor node is part of the RPL network because it has the This document also introduces an I-flag which is set by the target
required credentials. node and used by the ancestor node to initiate a DCO if the ancestor
nodes sees an update in the route adjacency. However, this flag
could be spoofed by a malicious 6LR in the path and can cause
invalidation of an existing active path. Note that invalidation will
happen only if the other conditions such as Path Sequence condition
is also met. Having said that a malicious 6LR may spoof a DAO on
behalf of the (sub) child with the I-flag set and can cause route
invalidation on behalf of the (sub) child node.
This document assumes that the security mechanisms as defined in
[RFC6550] are followed, which means that the common ancestor node and
all the 6LRs are part of the RPL network because they have the
required credentials. A non-secure RPL network needs to take into
consideration the risks highlighted in this section.
All RPL messages support a secure version of messages which allows All RPL messages support a secure version of messages which allows
integrity protection using either a MAC or a signature. Optionally, integrity protection using either a MAC or a signature. Optionally,
secured RPL messages also have encryption protection for secured RPL messages also have encryption protection for
confidentiality. confidentiality.
The document adds new messages (DCO, DCO-ACK) which are syntactically The document adds new messages (DCO, DCO-ACK) which are syntactically
similar to existing RPL messages such as DAO, DAO-ACK. Secure similar to existing RPL messages such as DAO, DAO-ACK. Secure
versions of DCO and DCO-ACK are added similar to other RPL messages versions of DCO and DCO-ACK are added similar to other RPL messages
(such as DAO, DAO-ACK). (such as DAO, DAO-ACK).
RPL supports three security modes as mentioned in Section 10.1 of RPL supports three security modes as mentioned in Section 10.1 of
[RFC6550]: [RFC6550]:
1. Unsecured: In this mode, it is expected that the RPL control 1. Unsecured: In this mode, it is expected that the RPL control
messages are secured by other security mechanisms, such as link- messages are secured by other security mechanisms, such as link-
layer security. In this mode, the RPL control messages, layer security. In this mode, the RPL control messages,
including DCO, DCO-ACK, do not have Security sections. A DCO and including DCO, DCO-ACK, do not have Security sections. Also note
DCO-ACK message which is not encrypted at link-layer MUST not be that unsecured mode does not imply that all messages are sent
handled by the RPL layer. Also all the DCO and DCO-ACK messages without any protection.
that are transmitted MUST be link-layer encrypted.
2. Preinstalled: In this mode, RPL uses secure messages. Thus 2. Preinstalled: In this mode, RPL uses secure messages. Thus
secure versions of DCO, DCO-ACK MUST be used in this mode. secure versions of DCO, DCO-ACK MUST be used in this mode.
3. Authenticated: In this mode, RPL uses secure messages. Thus 3. Authenticated: In this mode, RPL uses secure messages. Thus
secure versions of DCO, DCO-ACK MUST be used in this mode. secure versions of DCO, DCO-ACK MUST be used in this mode.
8. Normative References 8. 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,
skipping to change at page 18, line 17 skipping to change at page 18, line 46
A.1. Example DCO Messaging A.1. Example DCO Messaging
In Figure 1, node (D) switches its parent from (B) to (C). This In Figure 1, node (D) switches its parent from (B) to (C). This
example assumes that Node D has already established its own route via example assumes that Node D has already established its own route via
Node B-G-A-6LBR using pathseq=x. The example uses DAO and DCO Node B-G-A-6LBR using pathseq=x. The example uses DAO and DCO
messaging convention and specifies only the required parameters to messaging convention and specifies only the required parameters to
explain the example namely, the parameter 'tgt', which stands for explain the example namely, the parameter 'tgt', which stands for
Target Option and value of this parameter specifies the address of Target Option and value of this parameter specifies the address of
the target node. The parameter 'pathseq', which specifies the Path the target node. The parameter 'pathseq', which specifies the Path
Sequence value carried in the Transit Information Option. The Sequence value carried in the Transit Information Option. The
parameter 'I_flag' specifies the 'I' bit in the Transit Information parameter 'I_flag' specifies the 'I' flag in the Transit Information
Option. sequence of actions is as follows: Option. sequence of actions is as follows:
1. Node D switches its parent from node B to node C 1. Node D switches its parent from node B to node C
2. D sends a regular DAO(tgt=D,pathseq=x+1,I_flag=1) in the updated 2. D sends a regular DAO(tgt=D,pathseq=x+1,I_flag=1) in the updated
path to C path to C
3. C checks for a routing entry on behalf of D, since it cannot find 3. C checks for a routing entry on behalf of D, since it cannot find
an entry on behalf of D it creates a new routing entry and an entry on behalf of D it creates a new routing entry and
forwards the reachability information of the target D to H in a forwards the reachability information of the target D to H in a
DAO(tgt=D,pathseq=x+1,I_flag=1). DAO(tgt=D,pathseq=x+1,I_flag=1).
4. Similar to C, node H checks for a routing entry on behalf of D, 4. Similar to C, node H checks for a routing entry on behalf of D,
cannot find an entry and hence creates a new routing entry and cannot find an entry and hence creates a new routing entry and
forwards the reachability information of the target D to A in a forwards the reachability information of the target D to A in a
DAO(tgt=D,pathseq=x+1,I_flag=1). DAO(tgt=D,pathseq=x+1,I_flag=1).
5. Node A receives the DAO(tgt=D,pathseq=x+1,I_flag=1), and checks 5. Node A receives the DAO(tgt=D,pathseq=x+1,I_flag=1), and checks
for a routing entry on behalf of D. It finds a routing entry but for a routing entry on behalf of D. It finds a routing entry but
skipping to change at page 18, line 33 skipping to change at page 19, line 15
3. C checks for a routing entry on behalf of D, since it cannot find 3. C checks for a routing entry on behalf of D, since it cannot find
an entry on behalf of D it creates a new routing entry and an entry on behalf of D it creates a new routing entry and
forwards the reachability information of the target D to H in a forwards the reachability information of the target D to H in a
DAO(tgt=D,pathseq=x+1,I_flag=1). DAO(tgt=D,pathseq=x+1,I_flag=1).
4. Similar to C, node H checks for a routing entry on behalf of D, 4. Similar to C, node H checks for a routing entry on behalf of D,
cannot find an entry and hence creates a new routing entry and cannot find an entry and hence creates a new routing entry and
forwards the reachability information of the target D to A in a forwards the reachability information of the target D to A in a
DAO(tgt=D,pathseq=x+1,I_flag=1). DAO(tgt=D,pathseq=x+1,I_flag=1).
5. Node A receives the DAO(tgt=D,pathseq=x+1,I_flag=1), and checks 5. Node A receives the DAO(tgt=D,pathseq=x+1,I_flag=1), and checks
for a routing entry on behalf of D. It finds a routing entry but for a routing entry on behalf of D. It finds a routing entry but
checks that the next hop for target D is different (i.e. Node checks that the next hop for target D is different (i.e., Node
G). Node A checks the I_flag and generates G). Node A checks the I_flag and generates
DCO(tgt=D,pathseq=x+1) to previous next hop for target D which is DCO(tgt=D,pathseq=x+1) to previous next hop for target D which is
G. Subsequently, Node A updates the routing entry and forwards G. Subsequently, Node A updates the routing entry and forwards
the reachability information of target D upstream the reachability information of target D upstream
DAO(tgt=D,pathseq=x+1,I_flag=1). DAO(tgt=D,pathseq=x+1,I_flag=1).
6. Node G receives the DCO(tgt=D,pathseq=x+1). It checks if the 6. Node G receives the DCO(tgt=D,pathseq=x+1). It checks if the
received path sequence is latest as compared to the stored path received path sequence is latest as compared to the stored path
sequence. If it is latest, Node G invalidates routing entry of sequence. If it is latest, Node G invalidates routing entry of
target D and forwards the (un)reachability information downstream target D and forwards the (un)reachability information downstream
to B in DCO(tgt=D,pathseq=x+1). to B in DCO(tgt=D,pathseq=x+1).
skipping to change at page 21, line 17 skipping to change at page 22, line 17
Bangalore, Karnataka 560037 Bangalore, Karnataka 560037
India India
Phone: +91-080-49160700 Phone: +91-080-49160700
Email: rabinarayans@huawei.com Email: rabinarayans@huawei.com
Zhen Cao Zhen Cao
Huawei Huawei
W Chang'an Ave W Chang'an Ave
Beijing Beijing
China P.R. China
Email: zhencao.ietf@gmail.com Email: zhencao.ietf@gmail.com
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