Internet DRAFT - draft-thubert-roll-eliding-dio-information
draft-thubert-roll-eliding-dio-information
ROLL P. Thubert, Ed.
Internet-Draft Cisco Systems
Updates: 6550 (if approved) R.A. Jadhav
Intended status: Standards Track Huawei Tech
Expires: 28 September 2020 L. Zhao
Cisco Systems
D. Barthel
Orange Labs
27 March 2020
Eliding and Querying RPL Information
draft-thubert-roll-eliding-dio-information-04
Abstract
This document presents a method to safely elide a group of RPL
options in a DIO message by synchronizing the state associated with
each of these options between parent and child using a new sequence
counter in DIO messages. A child that missed a DIO message with an
update of any of those protected options detects it by the change of
sequence counter and queries the update with a DIS Message. The
draft also provides a method to fully elide the options in a DAO
message.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 28 September 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
Thubert, et al. Expires 28 September 2020 [Page 1]
Internet-Draft Eliding RPL Info March 2020
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Simplified BSD License text
as described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. BCP 14 . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. References . . . . . . . . . . . . . . . . . . . . . . . 4
2.3. Glossary . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Updating RFC 6550 . . . . . . . . . . . . . . . . . . . . . . 5
4. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Updated DIO Base Object . . . . . . . . . . . . . . . . . 6
4.2. Updated DIS Base Object . . . . . . . . . . . . . . . . . 6
4.3. Updated DAO Base Object . . . . . . . . . . . . . . . . . 7
4.4. New Abbreviated Option Option . . . . . . . . . . . . . . 8
5. RCSS Operation . . . . . . . . . . . . . . . . . . . . . . . 8
5.1. Updating the RCSS . . . . . . . . . . . . . . . . . . . . 9
5.2. RCSS Freshness and Parent selection . . . . . . . . . . . 10
5.3. RCSS of an Option . . . . . . . . . . . . . . . . . . . . 10
6. Synchronizing Options . . . . . . . . . . . . . . . . . . . . 12
7. Abbreviating the DAO Message . . . . . . . . . . . . . . . . 12
8. Security Considerations . . . . . . . . . . . . . . . . . . . 13
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
9.1. New DODAG Information Solicitation Flags . . . . . . . . 14
9.2. New DODAG Advertisement Object Flag . . . . . . . . . . . 14
9.3. New RPL Control Message Option . . . . . . . . . . . . . 14
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15
11. Normative References . . . . . . . . . . . . . . . . . . . . 15
12. Informative References . . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction
Classical Link State protocols synchronize their Link State Database
(LSDB) by sequencing every change. Each interested node maintains
the last sequence of the LSDB it is synchronizing with. If the last
known sequence number is older than the current, the node needs to
learn one by one all the state changes between the last known and the
current state.
Thubert, et al. Expires 28 September 2020 [Page 2]
Internet-Draft Eliding RPL Info March 2020
"RPL: IPv6 Routing Protocol for Low-Power and Lossy Networks" (LLNs)
[RPL] does not operate that way. With RPL, the routing information
is repeated over and over in DODAG Information Object (DIO) and
Destination Advertisement Object (DAO) messages. There is no concept
of synchronization. Still there is a concept of sequence to ensure
that the most recent information is recognized and overrides a
previous one. A stale state may exist in dead branches of the
network and eventually time out.
The RPL way was designed to enable routing from most nodes to most
nodes most of the time in a Low-Power Lossy Network (LLN) where the
quality of the links and the cost of communications does not permit
to maintain a permanent synchronization. This principle was applied
to both the routing and non-routing information such as configuration
settings, prefix information, and node capabilities.
This non-routing state is carried in RPL Messages as options. Some
of the DIO options may be needed to decide whether a node can join a
network as a leaf or as a router, and may affect the parent selection
or the address selection. It is thus critical that each node
maintains its state to the freshest and selects parents that are also
synchronized to the freshest.
[RPL] allows a parent to elide options in the DIO messages that it
sends repeatedly, to conserve battery and save bandwidth. When it
does so, a newcomer child that missed DIOs that contained the
configuration option may operate on default or partial information.
If it is pessimistic, it may query all possible information even when
it is not needed. Likewise, a node that slept may have missed a DIO
with a change in some critical information and may not be even aware
of it, so it may fail to query for the update and operate on
deprecated parameters.
This document uses a new sequence counter called the RPL
Configuration State Sequence (RCSS) to synchronize the state in a
child node with that of its parent, and recursively with that of the
whole network, to the latest setting from the Root.
The protected options are:
* The Route Information Option (RIO) defined in section 6.7.5 of
[RPL]
* The DODAG Configuration Option (DCO) defined in section 6.7.6 of
[RPL]
* The Prefix Information Option (PIO) defined in section 6.7.10 of
[RPL]
* The Extended MOP Option (MOPex) defined in [MOPEX]
* The Capability Option and TLVs defined in [CAPABILITIES]
Thubert, et al. Expires 28 September 2020 [Page 3]
Internet-Draft Eliding RPL Info March 2020
Any change in those options causes an increment of the RCSS and
enables a network-wide synchronization to the new state. If the
change impacts the routing substantially, the Root should decide to
increment the Version Number at the same time to fully rebuild the
DODAG with the new settings of the options. It must be noted that
rebuilding the DODAG does not guarantee that the non-routing state is
fully synchronized unless all the options were present in all the DIO
messages since the new Version is used.
2. Terminology
2.1. BCP 14
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here.
2.2. References
The Terminology used in this document is consistent with and
incorporates that described in Terms Used in Routing for Low-Power
and Lossy Networks [RFC7102].
Other terms in use in LLNs are found in Terminology for
Constrained-Node Networks [RFC7228].
A glossary of classical RPL acronyms is given in Section 2.3.
The term "byte" is used in its now customary sense as a synonym for
"octet".
"RPL", "RPL Packet Information" (RPI) and "RPL Instance", DIO, DAO
and DIS messages are defined in the "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks" [RPL] specification.
This document uses the terms RPL Leaf, RPL Aware Leaf (RAL), RPL-
Aware Node (RAN) and RPL-Unaware Leaf (RUL) as defined in section 2
of [USE_OF_RPL_INFO].
A RPL-Unaware Leaf (RUL) thus refers to a host that does not
understand RPL but uses a RPL router (without necessarily knowing it)
as default gateway and depends on that router to obtain reachability
for its addresses inside the RPL domain. Conversely, the term RPL-
Aware Node (RAN) is used to refer to a node that participates to RPL
and advertises its addresses or prefixes by itself.
Thubert, et al. Expires 28 September 2020 [Page 4]
Internet-Draft Eliding RPL Info March 2020
2.3. Glossary
This document often uses the following acronyms:
DODAG: Destination-Oriented Directed Acyclic Graph
LLN: Low-Power and Lossy Network
RPI: RPL Packet Information (an Option in the Hop-By_Hop Header)
RAL: RPL-Aware Leaf
RAN: RPL-Aware Node
RS: Router Solicitation
RCSS: RPL Configuration State Sequence
RPL: IPv6 Routing Protocol for LLNs (pronounced ripple)
RUL: RPL-Unaware Leaf
3. Updating RFC 6550
This document adds a new field called RCSS to the DIO message. The
RCSS is a sequence counter that is set by the Root and incremented as
specified in Section 7 of [RPL], more in Section 5.
This document also introduces a new RPL Control Message Option called
the Abbreviated Option Option (AOO). The AOO is the compressed
replacement of a protected option that indicates the RCSS of the last
change of that option, but elides its content, more in Section 4.4.
This document modifies the DIS Base Object to enable the individual
query of the protected options by a node that missed a change, more
in Section 4.2.
This document also enables to abbreviate a full DAO message when all
the options are unchanged from the most recent DAO message that was
positively acknowledged. In that case the DAO is resent with the
same DAOSequence and all the options are elided. A new flag in the
DAO Base Object indicates that this is an abbreviated DAO message,
more in Section 7.
The abbreviated DAO renews the lifetime of a DAO state but does not
change any information therein.
Thubert, et al. Expires 28 September 2020 [Page 5]
Internet-Draft Eliding RPL Info March 2020
4. Message Formats
4.1. Updated DIO Base Object
The format of the DIO Base Object is defined in section 6.3.1 of
[RPL]. This specification uses the 8th octet, which was reserved in
[RPL], to transport the RCSS.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RPLInstanceID |Version Number | Rank |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|G|0| MOP | Prf | DTSN | Flags | RCSS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ DODAGID +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option(s)...
+-+-+-+-+-+-+-+-+
Figure 1: Updated DIO Base Object
Updated fields:
RCSS:
One Byte, the RPL Configuration State Sequence
4.2. Updated DIS Base Object
The DIS Base Object is use by a child to query from a parent the most
recent changes in protected options. This specification adds flags
to indicate which options are requested and the freshest RCSS to
which the querying node was synchronized.
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R|D|P[M|O| Flg | LastSync RCSS | Option(s)...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Updated DIS Base Object
Thubert, et al. Expires 28 September 2020 [Page 6]
Internet-Draft Eliding RPL Info March 2020
Updated fields:
R:
One Bit, indicates that the RIO is requested
D:
One Bit, indicates that the DCO is requested
P:
One Bit, indicates that the PIO(s) is(are) requested
M:
One Bit, indicates that the MOPex is requested
O:
One Bit, indicates that the GCO is requested
Last Synchronized RCSS:
One Byte, the freshest RCSS to which the sender was synchronized
4.3. Updated DAO Base Object
The format of the DAO Base Object is defined in section 6.4.1 of
[RPL]. This specification adds the 'A' flag to indicate that the DAO
options are elided.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RPLInstanceID |K|D|A| Flags | Reserved | DAOSequence |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ DODAGID* +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option(s)...
+-+-+-+-+-+-+-+-+
Figure 3: Updated DAO Base Object
Updated fields:
A:
One Bit, indicates DAO in abbreviated version
Thubert, et al. Expires 28 September 2020 [Page 7]
Internet-Draft Eliding RPL Info March 2020
4.4. New Abbreviated Option Option
The Abbreviated Option Option (AOO) is a generic replacement for an
option that only indicates the sender's value of the RCSS for that
option. The format of the AOO is represented in Figure 4:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length | Abbrev. opt. | Last Mod RCSS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Abbreviated Option Option Format
Option fields:
Option Type:
One byte indicating "Abbreviated Option", see Table 3 in
Section 9.3
Option Length:
MUST be set to 2 indicating Option data of 2 bytes
Abbreviated Option:
The Option Type of the option being abbreviated
Last Modification RCSS:
The RCSS at which the option was last modified
5. RCSS Operation
Settings and updates to network-wide parameters are initiated by the
Root and propagated down the DODAG in RPL Control Message Options in
DIO messages. The DIO messages arrive asynchronously via different
parents and may confuse a child when they are not ordered.
The RCSS is a sequence number that is operated as specified in
section 7.2 of [RPL]. The RCSS sequences the atomic state that is
transported in the protected options in one or a burst of DIO
Messages. The same value of the RCSS is used in the initial burst
and in the subsequent DIO messages that are sent with no change in
the protected options.
The Root of the DODAG is autoritative to set and update the RCSS and
the options that it protects. The scope of an RCSS is one DODAG
within one RPL Instance.
Thubert, et al. Expires 28 September 2020 [Page 8]
Internet-Draft Eliding RPL Info March 2020
The RCSS and the sequenced state in the protected options are
propagated together down the DODAG without a change, more in
Section 5.1.
The RCSS allows a child to remain synchronized to a most recent
settings of the network-wide parameters that are propagated in the
protected options. The child recognizes stale DIO message(s) and
only uses parents with a consistent state, more in Section 5.2.
By extension, the RCSS is also defined for each protected option. A
child associates an option with the values of the RCSS indicated in
DIO Messages in which the option was advertised and uses it to assess
the relative freshness of different versions of an option, more in
Section 5.3.
Unchanged options may be sent in full, elided, or in the abbreviated
form specified in Section 4.4. Which form to use depends on the
RCSS, more in Section 5.3
If the link MTU does not permit to send a single DIO message with all
the options packaged then the options may be spread over multiple
consecutive DIO messages with the same RCSS that are sent in a rapid
sequence.
5.1. Updating the RCSS
The RCSS is incremented by the Root using a lollipop technique as
specified in section 7.2 of [RPL]. RCSS values are comparable if
they are within a window of comparison of SEQUENCE_WINDOW increments
or one indicates a reboot. A reboot of the Root is detected when the
RCSS moves from the circular to the straight part of the lollipop.
During the straight part of the lollipop, a second reboot of the Root
might not be recognized and a same value of the RCSS may reappear
with different settings in the protected options. For that reason
the protected options MUST be provided in full with each increment on
the RCSS during the straight part of the lollipop.
The straight part should be kept short with a RECOMMENDED initial
value of 252 or above. The Root SHOULD jump rapidly away from the
straight part once the network has sufficiently settled by resetting
the RCSS to 0, which places the RCSS in the circular region of the
lollipop, where the protected options MAY be elided or abbreviated.
When a field is modified in one of the protected options, the Root
MUST send a DIO with the RCSS incremented and the modified protected
option(s) in full. The Root MAY also update the Version Number to
form a new DODAG altogether.
Thubert, et al. Expires 28 September 2020 [Page 9]
Internet-Draft Eliding RPL Info March 2020
5.2. RCSS Freshness and Parent selection
A child node maintains the freshest RCSS received from its parents in
each of the RPL Instances that it participates to, and uses that RCSS
for its own DIO messages once it has synchronized all the protected
options to that RCSS.
A child and a candidate parent are out-of-sync when the RCSS values
that they maintain for a RPL Instance are not comparable. A child
MUST NOT use a parent that is out-of-sync unless no other parent is
available, in which case it MAY align its RCSS and synchronize to
that parent.
When a child receives from a candidate parent a DIO with an RCSS that
is fresher than the one it is using, the child MUST synchronize the
state relative to the protected options with that parent. The child
node MUST refrain from using that parent and the new state including
the RCSS, until it has synchronized all of the protected options to
that RCSS. When it is fully synchronized, the child may then use
that parent and the new RCSS.
Using a back-level parent may cause packets to be dropped,
misunderstood or misrouted. The child SHOULD refrain from using a
parent that exposes an older RCSS if the change causes an
incompatibility issue.
5.3. RCSS of an Option
By extension, the RCSS of an option is maintained by all nodes and is
defined for all but the Root as the freshest RCSS indicated by a DIO
message from a candidate parent in which the option was present, in
the abbreviated form or in full. A child maintains a state for the
RCSS of each of the protected options and synchronizes its state for
the options by comparing that RCSS with the one found in new DIO
messages for the option.
Protected options may be sent in full, elided, or in the abbreviated
form. Which form to use depends on the RCSS of the option that a
parent maintains:
* A parent MAY use either form when the RCSS is not changed from a
previous DIO; eliding options is PREFERRED in stable conditions to
save resources.
* When a protected option is updated, the RCSS is mechanically
incremented, and the new option MUST be sent in full on the first
DIO that advertises that new RCSS and the corresponding AOO SHOULD
NOT be added.
Thubert, et al. Expires 28 September 2020 [Page 10]
Internet-Draft Eliding RPL Info March 2020
* When the RCSS is updated but a protected option is unchanged, the
parent SHOULD NOT fully elide the option as it may cause multiple
children to synchronize it to no avail. The use of AOO is
RECOMMENDED unless it may cause a desynchronization for that
option, in which case the option SHOULD be placed in full, more in
Section 5.3.
When a child receives a DIO from a candidate parent, for each option:
If the Option is advertised in the abbreviated form, then the RCSS
that the DIO advertises for the option is the Last Modification
RCSS of the AOO, else
If the Option is advertised in full, then the RCSS that the DIO
advertises for the option is the RCSS of the DIO, else
If the Option is elided, then the RCSS is unspecified but it is at
most as fresh as the RCSS of the DIO, and the RCSS of the DIO is
assumed for the comparison
This means that if an Option is advertised in both the abbreviated
form and in full in a same DIO message then the RCSS in the AOO has
precedence.
To keep the RCSS comparable for each option, the RCSS of an option
must lazily progress along with the global RCSS even if there was no
change in the options. Each parent including the Root MUST advertise
a new RCSS for each of the protected options at least once within a
sliding window of SEQUENCE_WINDOW increments.
When an option was not changed for a new RCSS, one parent may
advertise it in the abbreviated form while another sends the option
in full only, e.g., in response to a DIS message. A fresher RCSS
indicates that the option is either the same or carries a more recent
update than the one with an older RCSS.
The RCSS of an option may be obtained from a DIO message that carries
the option in full even if the RCSS of the DIO is not the freshest
across parents, as long as the RCSS of the DIO is fresher than the
current one for that option.
If the current value of the maintained RCSS for a given option is not
fresher or as fresh as that advertised in a DIO message, then the
child MUST update its state for that option as specified in
Section 6.
Thubert, et al. Expires 28 September 2020 [Page 11]
Internet-Draft Eliding RPL Info March 2020
6. Synchronizing Options
As the value of the RCSS progresses, a child MUST NOT attempt to
synchronize its state with a parent that advertises a value of RCSS
that is out-of-sync with self, or that is already back level vs. the
most recent known RCSS for each protected option, unless it lost
reachability to all the candidate parents that advertise a fresher
and not out-of-sync value of RCSS.
A child can synchronize any of the protected options to the latest
RCSS by sending a DIS Message to a candidate parent that advertises
that RCSS in DIO messages. The child MUST set the desired
combination of 'R', 'D', 'P', 'M' and 'O' flags to indicate the
option(s) that it needs updated. The child MUST signal in the Last
Synchronized RCSS field of the DIS the freshest value of RCSS for
which it was fully synchronized, or a conventional value of OUT-OF-
SYNC-RCSS of 129 if it was never synchronized or is out-of-sync with
the parent.
The DIO message that is sent in response MUST contain in full all the
options that are requested and that were updated since the Last
Synchronized RCSS in the DIS Message. This means all of the
protected options if the child was never synchronized or is out-of-
sync with the parent. The other options MUST be added in the
abbreviated form.
The options MAY be spread over more than one DIO message sent in a
quick sequence. It is possible that the DIS is not received by the
parent or that a DIO that carries all or subset of the requested
options is lost in return. In that case the child MUST resend a DIS
with the bits associated to the options that are still missing after
a reasonable technology-dependent time before it retries the request.
The child MAY use any parent that advertises the RCSS to get any of
the options up to that level.
7. Abbreviating the DAO Message
When a node receives a positive DAO-ACK upon a DAO message for a
given DAOSequence, The DAO-ACK indicates that the DAO was fully
processed by its destination (parent or Root).
Until there is a change in one of the DAO options since that
DAOSequence, the next DAO messages merely refresh the lifetime of the
routes. In that case, increasing the DAOSequence creates undesirable
churn up the DODAG for no added value. This specification enables a
node to refresh the state in a destination that is associated to one
or more DAO message(s) that were acknowledged by that destination
without resending the DAO message(s) in full.
Thubert, et al. Expires 28 September 2020 [Page 12]
Internet-Draft Eliding RPL Info March 2020
Instead, the node MAY use a single abbreviated DAO message that is
sent to the same destination and with the same DAOSequence as the DAO
message(s) that it refreshes, and with the 'A' flag set (see
Section 4.3) to signal it is an abbreviated DAO.
This can be more than one message if the node could not package all
its state in a single message, e.g., due to MTU restrictions. In
that case the DAO state that is refreshed is the aggregation of the
DAO messages that were acknowledged for the provided DAOSequence by
that destination.
Upon the abbreviated DAO, the destination refreshes the state
associated to the original DAO message(s) received with that
DAOSequence, typically by extending the lifetimes of the routes that
were advertised with the same duration.
A node MAY also unset 'K' flag in the abbreviated DAP message and not
expect a DAO-ACK, if the node can assume the risk that the DAO is
lost, e.g., if the routes will be refreshed again before the lifetime
expires.
Only the DAO message(s) with the last (freshest) DAOSequence can be a
abbreviated. A nod MUST NOT use an abbreviated DAO with a
DAOSequence that is not the freshest and it MUST NOT use the
abbreviated form of the DAO until the destination has acknowledged
all state associated with that DAOSequence. If a destination
receives an abbreviated DAO with a DAOSequence that is not the
freshest from that node, or the destination does not have a state for
that node, then MUST send a DAO-ACK with a DAO Status indicating an
error. The destination MAY use a new Status of 'Out-of-Sync' in
which case the node MUST resent the DAO Message(s) in full with its
freshest DAOSequence and the destination synchronizes to that level.
It is RECOMMENDED to use an abbreviated DAO messages whenever
possible, because a smaller DAO message consumes less energy and
bandwidth and has better chances of delivery. In Non-Storing Mode
the benefits increases with the number of hops to the Root, and in
Storing Mode with the amount of state that is implicitely refreshed.
8. Security Considerations
TBD
9. IANA Considerations
Thubert, et al. Expires 28 September 2020 [Page 13]
Internet-Draft Eliding RPL Info March 2020
9.1. New DODAG Information Solicitation Flags
5 new bits are allocated in the Registry for the DODAG Information
Solicitation (DIS) Flags defined for [RPL].
+------------+----------------------------+-----------+
| Bit Number | Capability description | Reference |
+============+============================+===========+
| 0 | 'R' bit "RIO requested" | THIS RFC |
+------------+----------------------------+-----------+
| 1 | 'D' bit "DCO requested" | THIS RFC |
+------------+----------------------------+-----------+
| 2 | 'P' bit "PIO(s) requested" | THIS RFC |
+------------+----------------------------+-----------+
| 3 | 'M' bit "MOPex requested" | THIS RFC |
+------------+----------------------------+-----------+
| 4 | 'O' bit "GCO irequested" | THIS RFC |
+------------+----------------------------+-----------+
Table 1: New DIS Flags
9.2. New DODAG Advertisement Object Flag
1 new bit is allocated in the Registry for the Destination
Advertisement Object(DAO) Flags defined for[RPL].
+------------+---------------------------+-----------+
| Bit Number | Capability description | Reference |
+============+===========================+===========+
| 2 | 'A' bit "DAO abbreviated" | THIS RFC |
+------------+---------------------------+-----------+
Table 2: New DAO Flag
9.3. New RPL Control Message Option
A new entry is required for the new option of type "Abbreviated
Option", from the "RPL Control Message Options" space defined for
[RPL].
+----------+--------------------+-----------+
| Code | Description | Reference |
+==========+====================+===========+
| TBD IANA | Abbreviated Option | THIS RFC |
+----------+--------------------+-----------+
Table 3: New Option Type
Thubert, et al. Expires 28 September 2020 [Page 14]
Internet-Draft Eliding RPL Info March 2020
10. Acknowledgments
11. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RPL] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550,
DOI 10.17487/RFC6550, March 2012,
<https://www.rfc-editor.org/info/rfc6550>.
[RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for
Constrained-Node Networks", RFC 7228,
DOI 10.17487/RFC7228, May 2014,
<https://www.rfc-editor.org/info/rfc7228>.
[RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and
Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January
2014, <https://www.rfc-editor.org/info/rfc7102>.
[USE_OF_RPL_INFO]
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-38,
23 March 2020, <https://tools.ietf.org/html/draft-ietf-
roll-useofrplinfo-38>.
[CAPABILITIES]
Jadhav, R., Thubert, P., Richardson, M., and R. Sahoo,
"RPL Capabilities", Work in Progress, Internet-Draft,
draft-ietf-roll-capabilities-02, 11 March 2020,
<https://tools.ietf.org/html/draft-ietf-roll-capabilities-
02>.
[MOPEX] Jadhav, R., Thubert, P., and M. Richardson, "Mode of
Operation extension", Work in Progress, Internet-Draft,
Thubert, et al. Expires 28 September 2020 [Page 15]
Internet-Draft Eliding RPL Info March 2020
draft-jadhav-roll-mopex-02, 6 March 2020,
<https://tools.ietf.org/html/draft-jadhav-roll-mopex-02>.
12. Informative References
Authors' Addresses
Pascal Thubert (editor)
Cisco Systems, Inc
Building D
45 Allee des Ormes - BP1200
06254 Mougins - Sophia Antipolis
France
Phone: +33 497 23 26 34
Email: pthubert@cisco.com
Rahul Arvind Jadhav
Huawei Tech
Kundalahalli Village, Whitefield,
Bangalore 560037
Karnataka
India
Phone: +91-080-49160700
Email: rahul.ietf@gmail.com
Li Zhao
Cisco Systems, Inc
Xinsi Building
No. 926 Yi Shan Rd
SHANGHAI
200233
China
Email: liz3@cisco.com
Dominique Barthel
Orange Labs
28 chemin du Vieux Chêne
38243 Meylan
France
Email: dominique.barthel@orange.com
Thubert, et al. Expires 28 September 2020 [Page 16]
