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ROLL Working Group M. Robles
Internet-Draft Aalto
Updates: 6553, 6550, 8138 (if approved) M. Richardson
Intended status: Standards Track SSW
Expires: September 12, 2019 P. Thubert
Cisco
March 11, 2019
Using RPL Option Type, Routing Header for Source Routes and IPv6-in-IPv6
encapsulation in the RPL Data Plane
draft-ietf-roll-useofrplinfo-25
Abstract
This document looks at different data flows through LLN (Low-Power
and Lossy Networks) where RPL (IPv6 Routing Protocol for Low-Power
and Lossy Networks) is used to establish routing. The document
enumerates the cases where RFC 6553 (RPL Option Type), RFC 6554
(Routing Header for Source Routes) and IPv6-in-IPv6 encapsulation is
required in data plane. This analysis provides the basis on which to
design efficient compression of these headers. This document updates
RFC 6553 adding a change to the RPL Option Type. Additionally, this
document updates RFC 6550 to indicate about this change and updates
RFC8138 as well to consider the new Option Type when RPL Option is
decompressed.
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 September 12, 2019.
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Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
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 . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology and Requirements Language . . . . . . . . . . . . 4
3. Updates to RFC6553, RFC6550 and RFC 8138 . . . . . . . . . . 5
3.1. Updates to RFC 6553 . . . . . . . . . . . . . . . . . . . 5
3.2. Updates to RFC 8138 . . . . . . . . . . . . . . . . . . . 8
3.3. Updates to RFC 6550: Indicating the new RPI in the
DODAG Configuration Option Flag. . . . . . . . . . . . . 8
4. Sample/reference topology . . . . . . . . . . . . . . . . . . 9
5. Use cases . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6. Storing mode . . . . . . . . . . . . . . . . . . . . . . . . 15
6.1. Storing Mode: Interaction between Leaf and Root . . . . . 16
6.1.1. SM: Example of Flow from RPL-aware-leaf to root . . . 17
6.1.2. SM: Example of Flow from root to RPL-aware-leaf . . . 18
6.1.3. SM: Example of Flow from root to not-RPL-aware-leaf . 18
6.1.4. SM: Example of Flow from not-RPL-aware-leaf to root . 19
6.2. Storing Mode: Interaction between Leaf and Internet. . . 20
6.2.1. SM: Example of Flow from RPL-aware-leaf to Internet . 20
6.2.2. SM: Example of Flow from Internet to RPL-aware-leaf . 21
6.2.3. SM: Example of Flow from not-RPL-aware-leaf to
Internet . . . . . . . . . . . . . . . . . . . . . . 22
6.2.4. SM: Example of Flow from Internet to non-RPL-aware-
leaf. . . . . . . . . . . . . . . . . . . . . . . . . 23
6.3. Storing Mode: Interaction between Leaf and Leaf . . . . . 24
6.3.1. SM: Example of Flow from RPL-aware-leaf to RPL-aware-
leaf . . . . . . . . . . . . . . . . . . . . . . . . 24
6.3.2. SM: Example of Flow from RPL-aware-leaf to non-RPL-
aware-leaf . . . . . . . . . . . . . . . . . . . . . 26
6.3.3. SM: Example of Flow from not-RPL-aware-leaf to RPL-
aware-leaf . . . . . . . . . . . . . . . . . . . . . 26
6.3.4. SM: Example of Flow from not-RPL-aware-leaf to not-
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RPL-aware-leaf . . . . . . . . . . . . . . . . . . . 28
7. Non Storing mode . . . . . . . . . . . . . . . . . . . . . . 29
7.1. Non-Storing Mode: Interaction between Leaf and Root . . . 30
7.1.1. Non-SM: Example of Flow from RPL-aware-leaf to root . 31
7.1.2. Non-SM: Example of Flow from root to RPL-aware-leaf . 31
7.1.3. Non-SM: Example of Flow from root to not-RPL-aware-
leaf . . . . . . . . . . . . . . . . . . . . . . . . 32
7.1.4. Non-SM: Example of Flow from not-RPL-aware-leaf to
root . . . . . . . . . . . . . . . . . . . . . . . . 33
7.2. Non-Storing Mode: Interaction between Leaf and Internet . 34
7.2.1. Non-SM: Example of Flow from RPL-aware-leaf to
Internet . . . . . . . . . . . . . . . . . . . . . . 34
7.2.2. Non-SM: Example of Flow from Internet to RPL-aware-
leaf . . . . . . . . . . . . . . . . . . . . . . . . 35
7.2.3. Non-SM: Example of Flow from not-RPL-aware-leaf to
Internet . . . . . . . . . . . . . . . . . . . . . . 36
7.2.4. Non-SM: Example of Flow from Internet to not-RPL-
aware-leaf . . . . . . . . . . . . . . . . . . . . . 37
7.3. Non-Storing Mode: Interaction between Leafs . . . . . . . 38
7.3.1. Non-SM: Example of Flow from RPL-aware-leaf to RPL-
aware-leaf . . . . . . . . . . . . . . . . . . . . . 38
7.3.2. Non-SM: Example of Flow from RPL-aware-leaf to not-
RPL-aware-leaf . . . . . . . . . . . . . . . . . . . 40
7.3.3. Non-SM: Example of Flow from not-RPL-aware-leaf to
RPL-aware-leaf . . . . . . . . . . . . . . . . . . . 41
7.3.4. Non-SM: Example of Flow from not-RPL-aware-leaf to
not-RPL-aware-leaf . . . . . . . . . . . . . . . . . 42
8. Operational Considerations of supporting
not-RPL-aware-leaves . . . . . . . . . . . . . . . . . . . . 42
9. Operational considerations of introducing 0x23 . . . . . . . 43
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 44
11. Security Considerations . . . . . . . . . . . . . . . . . . . 45
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 48
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 48
13.1. Normative References . . . . . . . . . . . . . . . . . . 48
13.2. Informative References . . . . . . . . . . . . . . . . . 49
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 51
1. Introduction
RPL (IPv6 Routing Protocol for Low-Power and Lossy Networks)
[RFC6550] is a routing protocol for constrained networks. RFC 6553
[RFC6553] defines the "RPL option" (RPI), carried within the IPv6
Hop-by-Hop header to quickly identify inconsistencies (loops) in the
routing topology. RFC 6554 [RFC6554] defines the "RPL Source Route
Header" (RH3), an IPv6 Extension Header to deliver datagrams within a
RPL routing domain, particularly in non-storing mode.
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These various items are referred to as RPL artifacts, and they are
seen on all of the data-plane traffic that occurs in RPL routed
networks; they do not in general appear on the RPL control plane
traffic at all which is mostly hop-by-hop traffic (one exception
being DAO messages in non-storing mode).
It has become clear from attempts to do multi-vendor
interoperability, and from a desire to compress as many of the above
artifacts as possible that not all implementors agree when artifacts
are necessary, or when they can be safely omitted, or removed.
An interim meeting went through the 24 cases defined here to discover
if there were any shortcuts, and this document is the result of that
discussion. This document clarifies examples that intend to
illustrate the result of the normative language in RFC8200 and
RFC6553. In other words, the examples are intended to be normative
explanation of the results of executing that language.
A Routing Header Dispatch for 6LoWPAN (6LoRH)([RFC8138]) defines a
mechanism for compressing RPL Option information and Routing Header
type 3 [RFC6554], as well as an efficient IPv6-in-IPv6 technique.
1.1. Overview
The rest of the document is organized as follows: Section 2 describes
the used terminology. Section 3 describes the updates to RFC6553,
RFC6550 and RFC 8138. Section 4 provides the reference topology used
for the uses cases. Section 5 describes the uses cases included.
Section 6 describes the storing mode cases and section 7 the non-
storing mode cases. Section 8 describes the operational
considerations of supporting not-RPL-aware-leaves. Section 9 depicts
operational considerations for the proposed change on RPL Option
type, section 10 the IANA considerations and then section 11
describes the security aspects.
2. Terminology and Requirements Language
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.
Terminology defined in [RFC7102] applies to this document: LBR, LLN,
RPL, RPL Domain and ROLL.
RPL-node: A device which implements RPL, thus the device is RPL-
aware. Please note that the device can be found inside the LLN or
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outside LLN. In this document a RPL-node which is a leaf of a
(Destination Oriented Directed Acyclic Graph) DODAG is called RPL-
aware-leaf (Raf).
RPL-not-capable: A device which does not implement RPL, thus the
device is not-RPL-aware. Please note that the device can be found
inside the LLN. In this document a not-RPL-aware node which is a
leaf of a DODAG is called not-RPL-aware-leaf (~Raf).
6LN: [RFC6775] defines it as: "A 6LoWPAN node is any host or router
participating in a LoWPAN. This term is used when referring to
situations in which either a host or router can play the role
described.". In this document, a 6LN acts as a leaf.
6LR, 6LBR are defined in [RFC6775].
Flag Day: A transition that involves having a network with different
values of RPL Option Type. Thus the network does not work correctly.
Hop-by-hop IPv6-in-IPv6 headers: The term "hop-by-hop IPv6-in-IPv6"
header refers to: adding a header that originates from a node to an
adjacent node, using the addresses (usually the GUA or ULA, but could
use the link-local addresses) of each node. If the packet must
traverse multiple hops, then it must be decapsulated at each hop, and
then re-encapsulated again in a similar fashion.
3. Updates to RFC6553, RFC6550 and RFC 8138
3.1. Updates to RFC 6553
This modification is required to be able to send, for example, IPv6
packets from a RPL-aware-leaf to a not-RPL-aware node through
Internet (see Section 6.2.1), without requiring IPv6-in-IPv6
encapsulation.
[RFC6553] states as shown below, that in the Option Type field of the
RPL Option header, the two high order bits must be set to '01' and
the third bit is equal to '1'. The first two bits indicate that the
IPv6 node must discard the packet if it doesn't recognize the option
type, and the third bit indicates that the Option Data may change in
route. The remaining bits serve as the option type.
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Hex Value Binary Value
act chg rest Description Reference
--------- --- --- ------- ----------------- ----------
0x63 01 1 00011 RPL Option [RFC6553]
Figure 1: Option Type in RPL Option.
Recent changes in [RFC8200] (section 4, page 8), states: "it is now
expected that nodes along a packet's delivery path only examine and
process the Hop-by-Hop Options header if explicitly configured to do
so". Processing of the Hop-by-Hop Options header (by IPv6
intermediate nodes) is now optional, but if they are configured to
process the header, and if such nodes encounter an option with the
first two bits set to 01, they will drop the packet (if they conform
to [RFC8200]). Host systems should do the same, irrespective of the
configuration.
Based on that, if an IPv6 (intermediate) node (RPL-not-capable)
receives a packet with an RPL Option, it should ignore the HBH RPL
option (skip over this option and continue processing the header).
This is relevant, as it was mentioned previously, in the case that
there is a flow from RPL-aware-leaf to Internet (see Section 6.2.1).
Thus, this document updates the Option Type field to: the two high
order bits MUST be set to '00' and the third bit is equal to '1'.
The first two bits indicate that the IPv6 node MUST skip over this
option and continue processing the header ([RFC8200] Section 4.2) if
it doesn't recognize the option type, and the third bit continues to
be set to indicate that the Option Data may change en route. The
remaining bits serve as the option type and remain as 0x3. This
ensures that a packet that leaves the RPL domain of an LLN (or that
leaves the LLN entirely) will not be discarded when it contains the
[RFC6553] RPL Hop-by-Hop option known as RPI.
This is a significant update to [RFC6553]. [RFCXXXX] represents this
document.
Hex Value Binary Value
act chg rest Description Reference
--------- --- --- ------- ----------------- ----------
0x23 00 1 00011 RPL Option [RFCXXXX]
Figure 2: Revised Option Type in RPL Option.
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This change creates a flag day for existing networks which are
currently using 0x63 as the RPI value. A move to 0x23 will not be
understood by those networks. It is suggested that implementations
accept both 0x63 and 0x23 when processing.
In the cases where a forwarding node is forwarding traffic that is
not addressed directly to it (such as when the outer IPv6-in-IPv6
header is not a Link-Local address), then RFC8200 forbids changing
the RPI type code when forwarding.
When forwarding traffic that is wrapped in Link-Local IPv6-in-IPv6
headers, the forwarding node is in effect originating new packets,
and it MAY make a choice as to whether to use the old (0x63) RPI Type
code, or the new (0x23) RPI Type code. In that situation,
implementations SHOULD use the same value as was received. This
allows to the network to be incrementally upgraded, and in some cases
may allow the DODAG root to know which parts of the network are
upgraded.
A network which is switching from straight 6lowpan compression
mechanism to those described in [RFC8138] will experience a flag day
in the data compression anyway, and if possible this change can be
deployed at the same time.
The change of RPI option type from 0x63 to 0x23, makes all [RFC8200]
Section 4.2 compliant nodes tolerant of the RPL artifacts. There is
therefore no longer a necessity to remove the artifacts when sending
traffic to the Internet. This change clarifies when to use an IPv6-
in-IPv6 header, and how to address them: The Hop-by-Hop Options
Header containing the RPI option SHOULD always be added when 6LRs
originate packets (without IPv6-in-IPv6 headers), and IPv6-in-IPv6
headers SHOULD always be added when a 6LR find that it needs to
insert a Hop-by-Hop Options Header containing the RPI option. The
IPv6-in-IPv6 header is to be addressed to the RPL root when on the
way up, and to the end-host when on the way down.
Non-constrained uses of RPL are not in scope of this document, and
applicability statements for those uses may provide different advice,
E.g. [I-D.ietf-anima-autonomic-control-plane].
In the non-storing case, dealing with non-RPL aware leaf nodes is
much easier as the 6LBR (DODAG root) has complete knowledge about the
connectivity of all DODAG nodes, and all traffic flows through the
root node.
The 6LBR can recognize non-RPL aware leaf nodes because it will
receive a DAO about that node from the 6LR immediately above that
non-RPL aware node. This means that the non-storing mode case can
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avoid ever using hop-by-hop IPv6-in-IPv6 headers for traffic
originating from the root to leafs.
The non-storing mode case does not require the type change from 0x63
to 0x23, as the root can always create the right packet. The type
change does not adversely affect the non-storing case.
3.2. Updates to RFC 8138
RPI-6LoRH header provides a compressed form for the RPL RPI [RFC8138]
in section 6. A node that is decompressing this header MUST
decompress using the RPL RPI option type that is currently active:
that is, a choice between 0x23 (new) and 0x63 (old). The node will
know which to use based upon the presence of the DODAG Configuration
Option described in the next section. E.g. If the network is in
0x23 mode (by DIO option), then it should be decompressed to 0x23.
[RFC8138] section 7 documents how to compress the IPv6-in-IPv6
header.
There are potential significant advantages to having a single code
path that always processes IPv6-in-IPv6 headers with no options.
In Storing Mode, for the examples of Flow from RPL-aware-leaf to non-
RPL-aware-leaf and non-RPL-aware-leaf to non-RPL-aware-leaf comprise
an IPv6-in-IPv6 and RPI compression headers. The use of the IPv6-in-
IPv6 header is MANDATORY in this case, and it SHOULD be compressed
with [RFC8138] section 7.
+--+-----+---+--------------+-----------+-----------+-----------+
|1 | 0|0 |TSE| 6LoRH Type 6 | Hop Limit | RPI-6LoRH |LOWPAN IPHC|
+--+-----+---+--------------+-----------+-----------+-----------+
Figure 3: IPv6-in-IPv6 (RPI).
3.3. Updates to RFC 6550: Indicating the new RPI in the DODAG
Configuration Option Flag.
In order to avoid a Flag Day caused by lack of interoperation between
new RPI (0x23) and old RPI (0x63) nodes, this section defines a flag
in the DIO Configuration Option, to indicate when then new RPI value
can be safely used. Without this, there could be a mix of new nodes
(which understand 0x23 and 0x63), and old nodes (which understand
0x63 only). A new node would not know if it was safe to use 0x23.
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This is done via a DODAG Configuration Option flag which will
propagate through the network. If the flag is received with a value
zero (which is the default), then new nodes will remain in RFC6553
Compatible Mode; originating traffic with the old-RPI (0x63) value.
As stated in [RFC6550] the DODAG Configuration option is present in
DIO messages. The DODAG Configuration option distributes
configuration information. It is generally static, and does not
change within the DODAG. This information is configured at the DODAG
root and distributed throughout the DODAG with the DODAG
Configuration option. Nodes other than the DODAG root do not modify
this information when propagating the DODAG Configuration option.
The DODAG Configuration Option has a Flag field which is modified by
this document. Currently, the DODAG Configuration Option in
[RFC6550] states: "the unused bits MUST be initialize to zero by the
sender and MUST be ignored by the receiver".
Bit number three of the flag field in the DODAG Configuration option
is to be used as follows:
+------------+-----------------+---------------+
| Bit number | Description | Reference |
+------------+-----------------+---------------+
| 3 | RPI 0x23 enable | This document |
+------------+-----------------+---------------+
Figure 4: DODAG Configuration Option Flag to indicate the RPI-flag-
day.
In case of rebooting, the node (6LN or 6LR) does not remember if the
flag is set, so DIO messages would be set with the flag unset until a
DIO is received with the flag set.
4. Sample/reference topology
A RPL network in general is composed of a 6LBR (6LoWPAN Border
Router), Backbone Router (6BBR), 6LR (6LoWPAN Router) and 6LN
(6LoWPAN Node) as leaf logically organized in a DODAG structure.
Figure 4 shows the reference RPL Topology for this document. The
letters above the nodes are there so that they may be referenced in
subsequent sections. In the figure, 6LR represents a full router
node. The 6LN is a RPL aware router, or host (as a leaf).
Additionally, for simplification purposes, it is supposed that the
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6LBR has direct access to Internet, thus the 6BBR is not present in
the figure.
The 6LN leaves (Raf - "RPL aware leaf"-) marked as (F, H and I) are
RPL nodes with no children hosts.
The leafs marked as ~Raf "not-RPL aware leaf" (G and J) are devices
which do not speak RPL at all (not-RPL-aware), but uses Router-
Advertisements, 6LowPAN DAR/DAC and efficient-ND only to participate
in the network [RFC6775]. In the document these leafs (G and J) are
also referred to as an IPv6 node.
The 6LBR ("A") in the figure is the root of the Global DODAG.
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+------------+
| INTERNET ----------+
| | |
+------------+ |
|
|
|
A |
+-------+
|6LBR |
+-----------|(root) |-------+
| +-------+ |
| |
| |
| |
| |
| B |C
+---|---+ +---|---+
| 6LR | | 6LR |
+-------->| |--+ +--- ---+
| +-------+ | | +-------+ |
| | | |
| | | |
| | | |
| | | |
| D | E | |
+-|-----+ +---|---+ | |
| 6LR | | 6LR | | |
| | +------ | | |
+---|---+ | +---|---+ | |
| | | | |
| | +--+ | |
| | | | |
| | | | |
| | | I | J |
F | | G | H | |
+-----+-+ +-|-----+ +---|--+ +---|---+ +---|---+
| Raf | | ~Raf | | Raf | | Raf | | ~Raf |
| 6LN | | 6LN | | 6LN | | 6LN | | 6LN |
+-------+ +-------+ +------+ +-------+ +-------+
Figure 5: A reference RPL Topology.
RPL defines the RPL Control messages (control plane), a new ICMPv6
[RFC4443] message with Type 155. DIS (DODAG Information
Solicitation), DIO (DODAG Information Object) and DAO (Destination
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Advertisement Object) messages are all RPL Control messages but with
different Code values. A RPL Stack is shown in Figure 5.
+--------------+
| Upper Layers |
| |
+--------------+
| RPL |
| |
+--------------+
| ICMPv6 |
| |
+--------------+
| IPv6 |
| |
+--------------+
| 6LoWPAN |
| |
+--------------+
| PHY-MAC |
| |
+--------------+
Figure 6: RPL Stack.
RPL supports two modes of Downward traffic: in storing mode (RPL-SM),
it is fully stateful; in non-storing (RPL-NSM), it is fully source
routed. A RPL Instance is either fully storing or fully non-storing,
i.e. a RPL Instance with a combination of storing and non-storing
nodes is not supported with the current specifications at the time of
writing this document.
5. Use cases
In the data plane a combination of RFC6553, RFC6554 and IPv6-in-IPv6
encapsulation are going to be analyzed for a number of representative
traffic flows.
This document assumes that the LLN is using the no-drop RPI option
(0x23).
The uses cases describe the communication between RPL-aware-nodes,
with the root (6LBR), and with Internet. This document also describe
the communication between nodes acting as leaves that do not
understand RPL, but are part of the LLN. these nodes are named as
not-RPL-aware-leaf, mentioned previously. (e.g. Section 6.1.4 Flow
from not-RPL-aware-leaf to root) This document describes also how is
the communication inside of the LLN when it has the final destination
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addressed outside of the LLN e.g. with destination to Internet.
(e.g. Section 6.2.3 Flow from not-RPL-aware-leaf to Internet)
The uses cases comprise as follow:
Interaction between Leaf and Root:
RPL-aware-leaf to root
root to RPL-aware-leaf
not-RPL-aware-leaf to root
root to not-RPL-aware-leaf
Interaction between Leaf and Internet:
RPL-aware-leaf to Internet
Internet to RPL-aware-leaf
not-RPL-aware-leaf to Internet
Internet to not-RPL-aware-leaf
Interaction between Leafs:
RPL-aware-leaf to RPL-aware-leaf (storing and non-storing)
RPL-aware-leaf to not-RPL-aware-leaf (non-storing)
not-RPL-aware-leaf to RPL-aware-leaf (storing and non-storing)
not-RPL-aware-leaf to not-RPL-aware-leaf (non-storing)
This document is consistent with the rule that a Header cannot be
inserted or removed on the fly inside an IPv6 packet that is being
routed. This is a fundamental precept of the IPv6 architecture as
outlined in [RFC8200]. Extensions may not be added or removed except
by the sender or the receiver.
However, unlike [RFC6553], the Hop-by-Hop Option Header used for the
RPI artifact has the first two bits set to '00'. This means that the
RPI artifact will be ignored when received by a host or router that
does not understand that option ( Section 4.2 [RFC8200]).
This means that when the no-drop RPI option code 0x23 is used, a
packet that leaves the RPL domain of an LLN (or that leaves the LLN
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entirely) will not be discarded when it contains the [RFC6553] RPL
Hop-by-Hop option known as RPI. Thus, the RPI Hop-by-Hop option is
left in place even if the end host does not understand it.
NOTE: There is some possible security risk when the RPI information
is released to the Internet. At this point this is a theoretical
situation; no clear attack has been described. At worst, it is clear
that the RPI option would waste some network bandwidth when it
escapes. This is traded off against the savings in the LLN by not
having to encapsulate the packet in order to remove the artifact.
As the rank information in the RPI artifact is changed at each hop,
it will typically be zero when it arrives at the DODAG root. The
DODAG root SHOULD force it to zero when passing the packet out to the
Internet. The Internet will therefore not see any SenderRank
information.
Despite being legal to leave the RPI artifact in place, an
intermediate router that needs to add an extension header (RH3 or RPI
Option) MUST still encapsulate the packet in an (additional) outer IP
header. The new header is placed after this new outer IP header.
A corollary is that an RH3 or RPI Option can only be removed by an
intermediate router if it is placed in an encapsulating IPv6 Header,
which is addressed TO the intermediate router. When it does so, the
whole encapsulating header must be removed. (A replacement may be
added). This sometimes can result in outer IP headers being
addressed to the next hop router using link-local address.
Both RPI and RH3 headers may be modified in very specific ways by
routers on the path of the packet without the need to add to remove
an encapsulating header. Both headers were designed with this
modification in mind, and both the RPL RH3 and the RPL option are
marked mutable but recoverable: so an IPsec AH security header can be
applied across these headers, but it can not secure the values which
mutate.
RPI MUST be present in every single RPL data packet. There is one
exception in non-storing mode: when a packet is going down from the
root the RPI MAY be omitted. The rational is that in a downward non-
storing mode, the entire route is written, so there can be no loops
by construction, nor any confusion about which forwarding table to
use (as the root has already made all routing decisions). However,
there are still cases, such as in 6tisch, where the instanceID
portion of the RPI header may still be needed [RFC8180] to pick an
appropriate priority or channel at each hop.
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Prior to [RFC8138], there was significant interest in removing the
RPI for downward flows in non-storing mode. The exception covered a
very small number of cases, and causes significant interoperability
challenges, yet costed significant code and testing complexity. The
ability to compress the RPI down to three bytes or less removes much
of the pressure to optimize this any further
[I-D.ietf-anima-autonomic-control-plane].
The earlier examples are more extensive to make sure that the process
is clear, while later examples are more concise.
6. Storing mode
In storing mode (fully stateful), the sender can determine if the
destination is inside the LLN by looking if the destination address
is matched by the DIO's Prefix Information Option (PIO) option.
The following table (Figure 7) itemizes which headers are needed in
each of the following scenarios. It indicate if an IPv6-in-IPv6
header must be inserted, and whether the destination address of the
IPv6-in-IPv6 header is the next hop, or the final target address.
There are these possible situations: hop-by-hop necessary (indicated
by "hop"), or final target address possible (indicated by "tgt"). In
all cases hop by hop may be used rather than the final target
address.
In cases where no IPv6-in-IPv6 header is needed, the column states as
"No".
In all cases the RPI headers are needed, since it identifies
inconsistencies (loops) in the routing topology. In all cases the
RH3 is not needed because it is not used in storing mode.
In each case, 6LR_i are the intermediate routers from source to
destination. "1 <= i <= n", n is the number of routers (6LR) that
the packet go through from source (6LN) to destination.
The leaf can be a router 6LR or a host, both indicated as 6LN (see
Figure 5).
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+---------------------+--------------+------------+--------------+
| Interaction between | Use Case |IPv6-in-IPv6| v6-in-v6 dst |
+---------------------+--------------+------------+--------------+
| | Raf to root | No | No |
+ +--------------+------------+--------------+
| Leaf - Root | root to Raf | No | No |
+ +--------------+------------+--------------+
| | root to ~Raf | No | No |
+ +--------------+------------+--------------+
| | ~Raf to root | must | root |
+---------------------+--------------+------------+--------------+
| | Raf to Int | No | No |
+ +--------------+------------+--------------+
| Leaf - Internet | Int to Raf | must | tgt (Raf) |
+ +--------------+------------+--------------+
| | ~Raf to Int | must | root |
+ +--------------+------------+--------------+
| | Int to ~Raf | must | hop |
+---------------------+--------------+------------+--------------+
| | Raf to Raf | No | No |
+ +--------------+------------+--------------+
| | Raf to ~Raf | No | No |
+ Leaf - Leaf +--------------+------------+--------------+
| | ~Raf to Raf | must | tgt (Raf) |
+ +--------------+------------+--------------+
| | ~Raf to ~Raf | Yes | hop |
+---------------------+--------------+------------+--------------+
Figure 7: Table of IPv6-in-IPv6 encapsulation in Storing mode.
6.1. Storing Mode: Interaction between Leaf and Root
In this section is described the communication flow in storing mode
(SM) between,
RPL-aware-leaf to root
root to RPL-aware-leaf
not-RPL-aware-leaf to root
root to not-RPL-aware-leaf
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6.1.1. SM: Example of Flow from RPL-aware-leaf to root
In storing mode, RFC 6553 (RPI) is used to send RPL Information
instanceID and rank information.
As stated in Section 16.2 of [RFC6550] a RPL-aware-leaf node does not
generally issue DIO messages; a leaf node accepts DIO messages from
upstream. (When the inconsistency in routing occurs, a leaf node
will generate a DIO with an infinite rank, to fix it). It may issue
DAO and DIS messages though it generally ignores DAO and DIS
messages.
In this case the flow comprises:
RPL-aware-leaf (6LN) --> 6LR_i --> root(6LBR)
For example, a communication flow could be: Node F --> Node E -->
Node B --> Node A root(6LBR)
As it was mentioned in this document 6LRs, 6LBR are always full-
fledged RPL routers.
The 6LN (Node F) inserts the RPI header, and sends the packet to 6LR
(Node E) which decrements the rank in RPI and sends the packet up.
When the packet arrives at 6LBR (Node A), the RPI is removed and the
packet is processed.
No IPv6-in-IPv6 header is required.
The RPI header can be removed by the 6LBR because the packet is
addressed to the 6LBR. The 6LN must know that it is communicating
with the 6LBR to make use of this scenario. The 6LN can know the
address of the 6LBR because it knows the address of the root via the
DODAGID in the DIO messages.
+-------------------+-----+-------+------+
| Header | 6LN | 6LR_i | 6LBR |
+-------------------+-----+-------+------+
| Inserted headers | RPI | -- | -- |
| Removed headers | -- | -- | RPI |
| Re-added headers | -- | -- | -- |
| Modified headers | -- | RPI | -- |
| Untouched headers | -- | -- | -- |
+-------------------+-----+-------+------+
Table 1: Storing: Summary of the use of headers from RPL-aware-leaf
to root
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6.1.2. SM: Example of Flow from root to RPL-aware-leaf
In this case the flow comprises:
root (6LBR) --> 6LR_i --> RPL-aware-leaf (6LN)
For example, a communication flow could be: Node A root(6LBR) -->
Node B --> Node D --> Node F
In this case the 6LBR inserts RPI header and sends the packet down,
the 6LR is going to increment the rank in RPI (it examines the
instanceID to identify the right forwarding table), the packet is
processed in the 6LN and the RPI removed.
No IPv6-in-IPv6 header is required.
+-------------------+------+-------+------+
| Header | 6LBR | 6LR_i | 6LN |
+-------------------+------+-------+------+
| Inserted headers | RPI | -- | -- |
| Removed headers | -- | -- | RPI |
| Re-added headers | -- | -- | -- |
| Modified headers | -- | RPI | -- |
| Untouched headers | -- | -- | -- |
+-------------------+------+-------+------+
Table 2: Storing: Summary of the use of headers from root to RPL-
aware-leaf
6.1.3. SM: Example of Flow from root to not-RPL-aware-leaf
In this case the flow comprises:
root (6LBR) --> 6LR_i --> not-RPL-aware-leaf (IPv6)
For example, a communication flow could be: Node A root(6LBR) -->
Node B --> Node E --> Node G
As the RPI extension can be ignored by the not-RPL-aware leaf, this
situation is identical to the previous scenario.
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+-------------------+------+-------+----------------+
| Header | 6LBR | 6LR_i | IPv6 |
+-------------------+------+-------+----------------+
| Inserted headers | RPI | -- | -- |
| Removed headers | -- | -- | -- |
| Re-added headers | -- | -- | -- |
| Modified headers | -- | RPI | -- |
| Untouched headers | -- | -- | RPI (Ignored) |
+-------------------+------+-------+----------------+
Table 3: Storing: Summary of the use of headers from root to not-RPL-
aware-leaf
6.1.4. SM: Example of Flow from not-RPL-aware-leaf to root
In this case the flow comprises:
not-RPL-aware-leaf (IPv6) --> 6LR_1 --> 6LR_i --> root (6LBR)
For example, a communication flow could be: Node G --> Node E -->
Node B --> Node A root(6LBR)
When the packet arrives from IPv6 node (Node G) to 6LR_1 (Node E),
the 6LR_1 will insert a RPI header, encapsuladed in a IPv6-in-IPv6
header. The IPv6-in-IPv6 header can be addressed to the next hop
(Node B), or to the root (Node A). The root removes the header and
processes the packet.
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+---------+-----+---------------+------------------+----------------+
| Header | IPv | 6LR_1 | 6LR_i | 6LBR |
| | 6 | | | |
+---------+-----+---------------+------------------+----------------+
| Inserte | -- | IPv6-in- | IPv6-in- | -- |
| d | | IPv6(RPI) | IPv6(RPI)(1) | |
| headers | | | | |
| Removed | -- | -- | -- | IPv6-in- |
| headers | | | | IPv6(RPI) |
| Re- | -- | -- | IPv6-in- | -- |
| added | | | IPv6(RPI)(1) | |
| headers | | | | |
| Modifie | -- | -- | IPv6-in- | -- |
| d | | | IPv6(RPI)(2) | |
| headers | | | | |
| Untouch | -- | -- | -- | -- |
| ed | | | | |
| headers | | | | |
+---------+-----+---------------+------------------+----------------+
Table 4: Storing: Summary of the use of headers from not-RPL-aware-
leaf to root. (1) Case where the IPv6-in-IPv6 header is addressed to
the next hop (Node B). (2) Case where the IPv6-in-IPv6 header is
addressed to the root (Node A)
6.2. Storing Mode: Interaction between Leaf and Internet.
In this section is described the communication flow in storing mode
(SM) between,
RPL-aware-leaf to Internet
Internet to RPL-aware-leaf
not-RPL-aware-leaf to Internet
Internet to not-RPL-aware-leaf
6.2.1. SM: Example of Flow from RPL-aware-leaf to Internet
RPL information from RFC 6553 may go out to Internet as it will be
ignored by nodes which have not been configured to be RPI aware.
In this case the flow comprises:
RPL-aware-leaf (6LN) --> 6LR_i --> root (6LBR) --> Internet
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For example, the communication flow could be: Node F --> Node D -->
Node B --> Node A root(6LBR) --> Internet
No IPv6-in-IPv6 header is required.
Note: In this use case it is used a node as leaf, but this use case
can be also applicable to any RPL-node type (e.g. 6LR)
+-------------------+------+-------+------+----------------+
| Header | 6LN | 6LR_i | 6LBR | Internet |
+-------------------+------+-------+------+----------------+
| Inserted headers | RPI | -- | -- | -- |
| Removed headers | -- | -- | -- | -- |
| Re-added headers | -- | -- | -- | -- |
| Modified headers | -- | RPI | -- | -- |
| Untouched headers | -- | -- | RPI | RPI (Ignored) |
+-------------------+------+-------+------+----------------+
Table 5: Storing: Summary of the use of headers from RPL-aware-leaf
to Internet
6.2.2. SM: Example of Flow from Internet to RPL-aware-leaf
In this case the flow comprises:
Internet --> root (6LBR) --> 6LR_i --> RPL-aware-leaf (6LN)
For example, a communication flow could be: Internet --> Node A
root(6LBR) --> Node B --> Node D --> Node F
When the packet arrives from Internet to 6LBR the RPI header is added
in a outer IPv6-in-IPv6 header and sent to 6LR, which modifies the
rank in the RPI. When the packet arrives at 6LN the RPI header is
removed and the packet processed.
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+---------+--------+---------------+---------------+----------------+
| Header | Intern | 6LBR | 6LR_i | 6LN |
| | et | | | |
+---------+--------+---------------+---------------+----------------+
| Inserte | -- | IPv6-in- | -- | -- |
| d | | IPv6(RPI) | | |
| headers | | | | |
| Removed | -- | -- | -- | IPv6-in- |
| headers | | | | IPv6(RPI) |
| Re- | -- | -- | -- | -- |
| added | | | | |
| headers | | | | |
| Modifie | -- | -- | IPv6-in- | -- |
| d | | | IPv6(RPI) | |
| headers | | | | |
| Untouch | -- | -- | -- | -- |
| ed | | | | |
| headers | | | | |
+---------+--------+---------------+---------------+----------------+
Table 6: Storing: Summary of the use of headers from Internet to RPL-
aware-leaf
6.2.3. SM: Example of Flow from not-RPL-aware-leaf to Internet
In this case the flow comprises:
not-RPL-aware-leaf (IPv6) --> 6LR_1 --> 6LR_i -->root (6LBR) -->
Internet
For example, a communication flow could be: Node G --> Node E -->
Node B --> Node A root(6LBR) --> Internet
The 6LR_1 (i=1) node will add an IPv6-in-IPv6(RPI) header addressed
either to the root, or hop-by-hop such that the root can remove the
RPI header before passing upwards. The IPv6-in-IPv6 addressed to the
root cause less processing overhead. On the other hand, with hop-by-
hop the intermediate routers can check the routing tables for a
better routing path, thus it could be more efficient and faster.
Implementation should decide which approach to take.
The originating node will ideally leave the IPv6 flow label as zero
so that the packet can be better compressed through the LLN. The
6LBR will set the flow label of the packet to a non-zero value when
sending to the Internet.
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+-------+----+-------------+---------------+---------------+--------+
| Heade | IP | 6LR_1 | 6LR_i | 6LBR | Intern |
| r | v6 | | [i=2,..,n]_ | | et |
+-------+----+-------------+---------------+---------------+--------+
| Inser | -- | IPv6-in- | IPv6-in- | -- | -- |
| ted h | | IPv6(RPI) | IPv6(RPI)(2) | | |
| eader | | | | | |
| s | | | | | |
| Remov | -- | -- | IPv6-in- | IPv6-in- | -- |
| ed he | | | IPv6(RPI)(2) | IPv6(RPI)(1) | |
| aders | | | | | |
| Re- | -- | -- | -- | -- | -- |
| added | | | | | |
| heade | | | | | |
| rs | | | | | |
| Modif | -- | -- | IPv6-in- | -- | -- |
| ied h | | | IPv6(RPI)(1) | | |
| eader | | | | | |
| s | | | | | |
| Untou | -- | -- | -- | -- | -- |
| ched | | | | | |
| heade | | | | | |
| rs | | | | | |
+-------+----+-------------+---------------+---------------+--------+
Table 7: Storing: Summary of the use of headers from not-RPL-aware-
leaf to Internet. (1) Case when packet is addressed to the root.
(2) Case when the packet is addressed hop-by-hop.
6.2.4. SM: Example of Flow from Internet to non-RPL-aware-leaf.
In this case the flow comprises:
Internet --> root (6LBR) --> 6LR_i --> not-RPL-aware-leaf (IPv6)
For example, a communication flow could be: Internet --> Node A
root(6LBR) --> Node B --> Node E --> Node G
The 6LBR will have to add an RPI header within an IPv6-in-IPv6
header. The IPv6-in-IPv6 is addressed to the not-RPL-aware-leaf,
leaving the RPI inside.
The final node should be able to remove one or more IPv6-in-IPv6
headers which are all addressed to it. Furhter details about this
are mentioned in [I-D.thubert-roll-unaware-leaves], which specifies
RPL routing for a 6LN acting as a plain host and not aware of RPL.
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The 6LBR may set the flow label on the inner IPv6-in-IPv6 header to
zero in order to aid in compression.
+--------+---------+---------------+---------------+----------------+
| Header | Interne | 6LBR | 6LR_i | IPv6 |
| | t | | | |
+--------+---------+---------------+---------------+----------------+
| Insert | -- | IPv6-in- | -- | -- |
| ed hea | | IPv6(RPI) | | |
| ders | | | | |
| Remove | -- | -- | -- | IPv6-in- |
| d head | | | | IPv6(RPI)- RPI |
| ers | | | | (Ignored) |
| Re- | -- | -- | -- | -- |
| added | | | | |
| header | | | | |
| s | | | | |
| Modifi | -- | -- | IPv6-in- | -- |
| ed hea | | | IPv6(RPI) | |
| ders | | | | |
| Untouc | -- | -- | -- | -- |
| hed he | | | | |
| aders | | | | |
+--------+---------+---------------+---------------+----------------+
Table 8: Storing: Summary of the use of headers from Internet to non-
RPL-aware-leaf
6.3. Storing Mode: Interaction between Leaf and Leaf
In this section is described the communication flow in storing mode
(SM) between,
RPL-aware-leaf to RPL-aware-leaf
RPL-aware-leaf to not-RPL-aware-leaf
not-RPL-aware-leaf to RPL-aware-leaf
not-RPL-aware-leaf to not-RPL-aware-leaf
6.3.1. SM: Example of Flow from RPL-aware-leaf to RPL-aware-leaf
In [RFC6550] RPL allows a simple one-hop optimization for both
storing and non-storing networks. A node may send a packet destined
to a one-hop neighbor directly to that node. See section 9 in
[RFC6550].
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When the nodes are not directly connected, then in storing mode, the
flow comprises:
6LN --> 6LR_ia --> common parent (6LR_x) --> 6LR_id --> 6LN
For example, a communication flow could be: Node F --> Node D -->
Node B --> Node E --> Node H
6LR_ia (Node D) are the intermediate routers from source to the
common parent (6LR_x) (Node B) In this case, "1 <= ia <= n", n is the
number of routers (6LR) that the packet go through from 6LN (Node F)
to the common parent (6LR_x).
6LR_id (Node E) are the intermediate routers from the common parent
(6LR_x) (Node B) to destination 6LN (Node H). In this case, "1 <= id
<= m", m is the number of routers (6LR) that the packet go through
from the common parent (6LR_x) to destination 6LN.
It is assumed that the two nodes are in the same RPL Domain (that
they share the same DODAG root). At the common parent (Node B), the
direction of RPI is changed (from increasing to decreasing the rank).
While the 6LR nodes will update the RPI, no node needs to add or
remove the RPI, so no IPv6-in-IPv6 headers are necessary. This may
be done regardless of where the destination is, as the included RPI
will be ignored by the receiver.
+---------------+--------+--------+---------------+--------+--------+
| Header | 6LN | 6LR_ia | 6LR_x (common | 6LR_id | 6LN |
| | src | | parent) | | dst |
+---------------+--------+--------+---------------+--------+--------+
| Inserted | RPI | -- | -- | -- | -- |
| headers | | | | | |
| Removed | -- | -- | -- | -- | RPI |
| headers | | | | | |
| Re-added | -- | -- | -- | -- | -- |
| headers | | | | | |
| Modified | -- | RPI | RPI | RPI | -- |
| headers | | | | | |
| Untouched | -- | -- | -- | -- | -- |
| headers | | | | | |
+---------------+--------+--------+---------------+--------+--------+
Table 9: Storing: Summary of the use of headers for RPL-aware-leaf to
RPL-aware-leaf
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6.3.2. SM: Example of Flow from RPL-aware-leaf to non-RPL-aware-leaf
In this case the flow comprises:
6LN --> 6LR_ia --> common parent (6LR_x) --> 6LR_id --> not-RPL-aware
6LN (IPv6)
For example, a communication flow could be: Node F --> Node D -->
Node B --> Node E --> Node G
6LR_ia are the intermediate routers from source (6LN) to the common
parent (6LR_x) In this case, "1 <= ia <= n", n is the number of
routers (6LR) that the packet go through from 6LN to the common
parent (6LR_x).
6LR_id (Node E) are the intermediate routers from the common parent
(6LR_x) (Node B) to destination not-RPL-aware 6LN (IPv6) (Node G).
In this case, "1 <= id <= m", m is the number of routers (6LR) that
the packet go through from the common parent (6LR_x) to destination
6LN.
This situation is identical to the previous situation Section 6.3.1
+-----------+------+--------+---------------+--------+--------------+
| Header | 6LN | 6LR_ia | 6LR_x(common | 6LR_id | IPv6 |
| | src | | parent) | | |
+-----------+------+--------+---------------+--------+--------------+
| Inserted | RPI | -- | -- | -- | -- |
| headers | | | | | |
| Removed | -- | -- | -- | -- | -- |
| headers | | | | | |
| Re-added | -- | -- | -- | -- | -- |
| headers | | | | | |
| Modified | -- | RPI | RPI | RPI | -- |
| headers | | | | | |
| Untouched | -- | -- | -- | -- | RPI(Ignored) |
| headers | | | | | |
+-----------+------+--------+---------------+--------+--------------+
Table 10: Storing: Summary of the use of headers for RPL-aware-leaf
to non-RPL-aware-leaf
6.3.3. SM: Example of Flow from not-RPL-aware-leaf to RPL-aware-leaf
In this case the flow comprises:
not-RPL-aware 6LN (IPv6) --> 6LR_ia --> common parent (6LR_x) -->
6LR_id --> 6LN
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For example, a communication flow could be: Node G --> Node E -->
Node B --> Node D --> Node F
6LR_ia (Node E) are the intermediate routers from source (not-RPL-
aware 6LN (IPv6)) (Node G) to the common parent (6LR_x) (Node B). In
this case, "1 <= ia <= n", n is the number of routers (6LR) that the
packet go through from source to the common parent.
6LR_id (Node D) are the intermediate routers from the common parent
(6LR_x) (Node B) to destination 6LN (Node F). In this case, "1 <= id
<= m", m is the number of routers (6LR) that the packet go through
from the common parent (6LR_x) to destination 6LN.
The 6LR_ia (ia=1) (Node E) receives the packet from the the IPv6 node
(Node G) and inserts and the RPI header encapsulated in IPv6-in-IPv6
header. The IPv6-in-IPv6 header is addressed to the destination 6LN
(Node F).
+-------+----+------------+-------------+-------------+-------------+
| Heade | IP | 6LR_ia | common | 6LR_id | 6LN |
| r | v6 | | parent | | |
| | | | (6LRx) | | |
+-------+----+------------+-------------+-------------+-------------+
| Inser | -- | IPv6-in- | -- | -- | -- |
| ted h | | IPv6(RPI) | | | |
| eader | | | | | |
| s | | | | | |
| Remov | -- | -- | -- | -- | IPv6-in- |
| ed he | | | | | IPv6(RPI) |
| aders | | | | | |
| Re- | -- | -- | -- | -- | -- |
| added | | | | | |
| heade | | | | | |
| rs | | | | | |
| Modif | -- | -- | IPv6-in- | IPv6-in- | -- |
| ied h | | | IPv6(RPI) | IPv6(RPI) | |
| eader | | | | | |
| s | | | | | |
| Untou | -- | -- | -- | -- | -- |
| ched | | | | | |
| heade | | | | | |
| rs | | | | | |
+-------+----+------------+-------------+-------------+-------------+
Table 11: Storing: Summary of the use of headers from not-RPL-aware-
leaf to RPL-aware-leaf
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6.3.4. SM: Example of Flow from not-RPL-aware-leaf to not-RPL-aware-
leaf
In this case the flow comprises:
not-RPL-aware 6LN (IPv6 src)--> 6LR_1--> 6LR_ia --> 6LR_id --> not-
RPL-aware 6LN (IPv6 dst)
For example, a communication flow could be: Node G --> Node E -->
Node B --> Node A (root) --> Node C --> Node J
Internal nodes 6LR_ia (e.g: Node E or Node B) are the intermediate
routers from the not-RPL-aware source (Node G) to the root (6LBR)
(Node A). In this case, "1 < ia <= n", n is the number of routers
(6LR) that the packet go through from IPv6 src to the root.
6LR_id (C) are the intermediate routers from the root (Node A) to the
destination Node J. In this case, "1 <= id <= m", m is the number of
routers (6LR) that the packet go through from the root to destination
(IPv6 dst).
Note that this flow is identical to Section 6.3.3, except for where
the IPv6-in-IPv6 header is inserted.
The 6LR_1 (Node E) receives the packet from the the IPv6 node (Node
G) and inserts the RPI header (RPI), encapsulated in an IPv6-in-IPv6
header. The IPv6-in-IPv6 header is addressed to the final
destination (Node J).
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+-------+----+------------+-------------+-------------+-------------+
| Heade | IP | 6LR_1 | 6LR_ia | 6LR_m | IPv6 dst |
| r | v6 | | | | |
| | sr | | | | |
| | c | | | | |
+-------+----+------------+-------------+-------------+-------------+
| Inser | -- | IPv6-in- | -- | -- | -- |
| ted h | | IPv6(RPI) | | | |
| eader | | | | | |
| s | | | | | |
| Remov | -- | -- | -- | -- | IPv6-in- |
| ed he | | | | | IPv6(RPI), |
| aders | | | | | RPI Ignored |
| Re- | -- | -- | -- | -- | -- |
| added | | | | | |
| heade | | | | | |
| rs | | | | | |
| Modif | -- | -- | IPv6-in- | IPv6-in- | -- |
| ied h | | | IPv6(RPI) | IPv6(RPI) | |
| eader | | | | | |
| s | | | | | |
| Untou | -- | -- | -- | -- | -- |
| ched | | | | | |
| heade | | | | | |
| rs | | | | | |
+-------+----+------------+-------------+-------------+-------------+
Table 12: Storing: Summary of the use of headers from not-RPL-aware-
leaf to non-RPL-aware-leaf
7. Non Storing mode
In Non Storing Mode (Non SM) (fully source routed), the 6LBR (DODAG
root) has complete knowledge about the connectivity of all DODAG
nodes, and all traffic flows through the root node. Thus, there is
no need for all nodes to know about the existence of non-RPL aware
nodes. Only the 6LBR needs to act if compensation is necessary for
non-RPL aware receivers.
The following table (Figure 8) summarizes what headers are needed in
the following scenarios, and indicates when the RPI, RH3 and IPv6-in-
IPv6 header are to be inserted. There are these possible situations:
target destination address possible (indicated by "tgt"), to a 6LR,
to a 6LN or to the root. In cases where no IPv6-in-IPv6 header is
needed, the column states as "No".
The leaf can be a router 6LR or a host, both indicated as 6LN
(Figure 3). In the Figure the (1) indicates a 6tisch case [RFC8180],
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where the instanceID portion of the RPI header may still be needed to
pick an appropriate priority or channel at each hop.
+-----------------+--------------+-----+-----+----------+----------+
| Interaction | Use Case | RPI | RH3 | v6-in-v6 | v6-in-v6 |
| between | | | | | dst |
+-----------------+--------------+-----+-----+----------+----------+
| | Raf to root | Yes | No | No | No |
+ +--------------+-----+-----+----------+----------+
| Leaf - Root | root to Raf | Opt | Yes | No | No |
+ +--------------+-----+-----+----------+----------+
| | root to ~Raf |No(1)| Yes | must | 6LR |
+ +--------------+-----+-----+----------+----------+
| | ~Raf to root | Yes | No | must | root |
+-----------------+--------------+-----+-----+----------+----------+
| | Raf to Int | Yes | No | must | root |
+ +--------------+-----+-----+----------+----------+
| Leaf - Internet | Int to Raf |No(1)| Yes | must | tgt |
+ +--------------+-----+-----+----------+----------+
| | ~Raf to Int | Yes | No | must | root |
+ +--------------+-----+-----+----------+----------+
| | Int to ~Raf |No(1)| Yes | must | 6LR |
+-----------------+--------------+-----+-----+----------+----------+
| | Raf to Raf | Yes | Yes | must | root/tgt |
+ +--------------+-----+-----+----------+----------+
| | Raf to ~Raf | Yes | Yes | must | root/6LR |
+ Leaf - Leaf +--------------+-----+-----+----------+----------+
| | ~Raf to Raf | Yes | Yes | must | root/6LN |
+ +--------------+-----+-----+----------+----------+
| | ~Raf to ~Raf | Yes | Yes | must | root/6LR |
+-----------------+--------------+-----+-----+----------+----------+
(1)-6tisch networks may need the RPI information.
Figure 8: Table that shows headers needed in Non-Storing mode: RPI,
RH3, IPv6-in-IPv6 encapsulation.
7.1. Non-Storing Mode: Interaction between Leaf and Root
In this section is described the communication flow in Non Storing
Mode (Non-SM) between,
RPL-aware-leaf to root
root to RPL-aware-leaf
not-RPL-aware-leaf to root
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root to not-RPL-aware-leaf
7.1.1. Non-SM: Example of Flow from RPL-aware-leaf to root
In non-storing mode the leaf node uses default routing to send
traffic to the root. The RPI header must be included since it
contains the rank information, which is used to avoid/detect loops.
RPL-aware-leaf (6LN) --> 6LR_i --> root(6LBR)
For example, a communication flow could be: Node F --> Node D -->
Node B --> Node A (root)
6LR_i are the intermediate routers from source to destination. In
this case, "1 <= i <= n", n is the number of routers (6LR) that the
packet go through from source (6LN) to destination (6LBR).
This situation is the same case as storing mode.
+-------------------+-----+-------+------+
| Header | 6LN | 6LR_i | 6LBR |
+-------------------+-----+-------+------+
| Inserted headers | RPI | -- | -- |
| Removed headers | -- | -- | RPI |
| Re-added headers | -- | -- | -- |
| Modified headers | -- | RPI | -- |
| Untouched headers | -- | -- | -- |
+-------------------+-----+-------+------+
Table 13: Non Storing: Summary of the use of headers from RPL-aware-
leaf to root
7.1.2. Non-SM: Example of Flow from root to RPL-aware-leaf
In this case the flow comprises:
root (6LBR) --> 6LR_i --> RPL-aware-leaf (6LN)
For example, a communication flow could be: Node A (root) --> Node B
--> Node D --> Node F
6LR_i are the intermediate routers from source to destination. In
this case, "1 <= i <= n", n is the number of routers (6LR) that the
packet go through from source (6LBR) to destination (6LN).
The 6LBR inserts an RH3, and a RPI header. No IPv6-in-IPv6 header is
necessary as the traffic originates with an RPL aware node, the 6LBR.
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The destination is known to RPL-aware because, the root knows the
whole topology in non-storing mode.
+-------------------+-----------------+-------+------------------+
| Header | 6LBR | 6LR_i | 6LN |
+-------------------+-----------------+-------+------------------+
| Inserted headers | (opt: RPI), RH3 | -- | -- |
| Removed headers | -- | -- | RH3, (opt: RPI) |
| Re-added headers | -- | -- | -- |
| Modified headers | -- | RH3 | -- |
| Untouched headers | -- | -- | -- |
+-------------------+-----------------+-------+------------------+
Table 14: Non Storing: Summary of the use of headers from root to
RPL-aware-leaf
7.1.3. Non-SM: Example of Flow from root to not-RPL-aware-leaf
In this case the flow comprises:
root (6LBR) --> 6LR_i --> not-RPL-aware-leaf (IPv6)
For example, a communication flow could be: Node A (root) --> Node B
--> Node E --> Node G
6LR_i are the intermediate routers from source to destination. In
this case, "1 <= i <= n", n is the number of routers (6LR) that the
packet go through from source (6LBR) to destination (IPv6).
In 6LBR the RH3 is added, it is modified at each intermediate 6LR
(6LR_1 and so on) and it is fully consumed in the last 6LR (6LR_n),
but left there. If RPI is left by the previous 6LR, then the IPv6
node which does not understand the RPI, will ignore it (following
RFC8200), thus encapsulation is not necessary. Due to the complete
knowledge of the topology at the root, the 6LBR may optionally
address the IPv6-in-IPv6 header to the last 6LR, such that it is
removed prior to the IPv6 node. Please see Section 8 for
clarification of use of IPv6-in-IPv6 encapsulation.
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+---------------+-------------+--------------+------------+---------+
| Header | 6LBR | 6LR_i(i=1) | 6LR_n(i=n) | IPv6 |
+---------------+-------------+--------------+------------+---------+
| Inserted | (opt: RPI), | -- | -- | -- |
| headers | RH3 | | | |
| Removed | -- | -- | RH3 | -- |
| headers | | | | |
| Re-added | -- | -- | -- | -- |
| headers | | | | |
| Modified | -- | (opt: RPI), | (opt: RPI) | -- |
| headers | | RH3 | | |
| Untouched | -- | -- | -- | opt: |
| headers | | | | RPI |
+---------------+-------------+--------------+------------+---------+
Table 15: Non Storing: Summary of the use of headers from root to
not-RPL-aware-leaf
7.1.4. Non-SM: Example of Flow from not-RPL-aware-leaf to root
In this case the flow comprises:
not-RPL-aware-leaf (IPv6) --> 6LR_1 --> 6LR_i --> root (6LBR)
For example, a communication flow could be: Node G --> Node E -->
Node B --> Node A (root)
6LR_i are the intermediate routers from source to destination. In
this case, "1 < i <= n", n is the number of routers (6LR) that the
packet go through from source (IPv6) to destination (6LBR). For
example, 6LR_1 (i=1) is the router that receives the packets from the
IPv6 node.
In this case the RPI is added by the first 6LR (6LR1) (Node E),
encapsulated in an IPv6-in-IPv6 header, and is modified in the
following 6LRs. The RPI and entire packet is consumed by the root.
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+---------+-----+----------------+----------------+-----------------+
| Header | IPv | 6LR_1 | 6LR_i | 6LBR |
| | 6 | | | |
+---------+-----+----------------+----------------+-----------------+
| Inserte | -- | IPv6-in- | -- | -- |
| d | | IPv6(RPI) | | |
| headers | | | | |
| Removed | -- | -- | -- | IPv6-in- |
| headers | | | | IPv6(RPI) |
| Re- | -- | -- | -- | -- |
| added | | | | |
| headers | | | | |
| Modifie | -- | -- | IPv6-in- | -- |
| d | | | IPv6(RPI) | |
| headers | | | | |
| Untouch | -- | -- | -- | -- |
| ed | | | | |
| headers | | | | |
+---------+-----+----------------+----------------+-----------------+
Table 16: Non Storing: Summary of the use of headers from not-RPL-
aware-leaf to root
7.2. Non-Storing Mode: Interaction between Leaf and Internet
This section will describe the communication flow in Non Storing Mode
(Non-SM) between:
RPL-aware-leaf to Internet
Internet to RPL-aware-leaf
not-RPL-aware-leaf to Internet
Internet to not-RPL-aware-leaf
7.2.1. Non-SM: Example of Flow from RPL-aware-leaf to Internet
In this case the flow comprises:
RPL-aware-leaf (6LN) --> 6LR_i --> root (6LBR) --> Internet
For example, a communication flow could be: Node F --> Node D -->
Node B --> Node A --> Internet
6LR_i are the intermediate routers from source to destination. In
this case, "1 <= i <= n", n is the number of routers (6LR) that the
packet go through from source (6LN) to 6LBR.
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This case is identical to storing-mode case.
The IPv6 flow label should be set to zero to aid in compression, and
the 6LBR will set it to a non-zero value when sending towards the
Internet.
+-------------------+------+-------+------+----------------+
| Header | 6LN | 6LR_i | 6LBR | Internet |
+-------------------+------+-------+------+----------------+
| Inserted headers | RPI | -- | -- | -- |
| Removed headers | -- | -- | -- | -- |
| Re-added headers | -- | -- | -- | -- |
| Modified headers | -- | RPI | -- | -- |
| Untouched headers | -- | -- | RPI | RPI (Ignored) |
+-------------------+------+-------+------+----------------+
Table 17: Non Storing: Summary of the use of headers from RPL-aware-
leaf to Internet
7.2.2. Non-SM: Example of Flow from Internet to RPL-aware-leaf
In this case the flow comprises:
Internet --> root (6LBR) --> 6LR_i --> RPL-aware-leaf (6LN)
For example, a communication flow could be: Internet --> Node A
(root) --> Node B --> Node D --> Node F
6LR_i are the intermediate routers from source to destination. In
this case, "1 <= i <= n", n is the number of routers (6LR) that the
packet go through from 6LBR to destination(6LN).
The 6LBR must add an RH3 header. As the 6LBR will know the path and
address of the target node, it can address the IPv6-in-IPv6 header to
that node. The 6LBR will zero the flow label upon entry in order to
aid compression.
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+-----------+----------+--------------+--------------+--------------+
| Header | Internet | 6LBR | 6LR_i | 6LN |
+-----------+----------+--------------+--------------+--------------+
| Inserted | -- | IPv6-in-IPv6 | -- | -- |
| headers | | (RH3,RPI) | | |
| Removed | -- | -- | -- | IPv6-in-IPv6 |
| headers | | | | (RH3,RPI) |
| Re-added | -- | -- | -- | -- |
| headers | | | | |
| Modified | -- | -- | IPv6-in-IPv6 | -- |
| headers | | | (RH3,RPI) | |
| Untouched | -- | -- | -- | -- |
| headers | | | | |
+-----------+----------+--------------+--------------+--------------+
Table 18: Non Storing: Summary of the use of headers from Internet to
RPL-aware-leaf
7.2.3. Non-SM: Example of Flow from not-RPL-aware-leaf to Internet
In this case the flow comprises:
not-RPL-aware-leaf (IPv6) --> 6LR_1 --> 6LR_i -->root (6LBR) -->
Internet
For example, a communication flow could be: Node G --> Node E -->
Node B --> Node A --> Internet
6LR_i are the intermediate routers from source to destination. In
this case, "1 < i <= n", n is the number of routers (6LR) that the
packet go through from source(IPv6) to 6LBR. e.g 6LR_1 (i=1).
In this case the flow label is recommended to be zero in the IPv6
node. As RPL headers are added in the IPv6 node packet, the first
6LR (6LR_1) will add a RPI header inside a new IPv6-in-IPv6 header.
The IPv6-in-IPv6 header will be addressed to the root. This case is
identical to the storing-mode case (see Section 6.2.3).
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+---------+-----+------------+-------------+-------------+----------+
| Header | IPv | 6LR_1 | 6LR_i | 6LBR | Internet |
| | 6 | | [i=2,..,n]_ | | |
+---------+-----+------------+-------------+-------------+----------+
| Inserte | -- | IPv6-in- | -- | -- | -- |
| d | | IPv6 (RPI) | | | |
| headers | | | | | |
| Removed | -- | -- | -- | IPv6-in- | -- |
| headers | | | | IPv6 (RPI) | |
| Re- | -- | -- | -- | -- | -- |
| added | | | | | |
| headers | | | | | |
| Modifie | -- | -- | IPv6-in- | -- | -- |
| d | | | IPv6 (RPI) | | |
| headers | | | | | |
| Untouch | -- | -- | -- | -- | -- |
| ed | | | | | |
| headers | | | | | |
+---------+-----+------------+-------------+-------------+----------+
Table 19: Non Storing: Summary of the use of headers from not-RPL-
aware-leaf to Internet
7.2.4. Non-SM: Example of Flow from Internet to not-RPL-aware-leaf
In this case the flow comprises:
Internet --> root (6LBR) --> 6LR_i --> not-RPL-aware-leaf (IPv6)
For example, a communication flow could be: Internet --> Node A
(root) --> Node B --> Node E --> Node G
6LR_i are the intermediate routers from source to destination. In
this case, "1 < i <= n", n is the number of routers (6LR) that the
packet go through from 6LBR to not-RPL-aware-leaf (IPv6).
The 6LBR must add an RH3 header inside an IPv6-in-IPv6 header. The
6LBR will know the path, and will recognize that the final node is
not an RPL capable node as it will have received the connectivity DAO
from the nearest 6LR. The 6LBR can therefore make the IPv6-in-IPv6
header destination be the last 6LR. The 6LBR will set to zero the
flow label upon entry in order to aid compression.
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+---------+--------+------------+------------+---------------+------+
| Header | Intern | 6LBR | 6LR_1 | 6LR_i(i=2,.., | IPv6 |
| | et | | | n) | |
+---------+--------+------------+------------+---------------+------+
| Inserte | -- | IPv6-in- | -- | -- | -- |
| d | | IPv6 (RH3, | | | |
| headers | | RPI) | | | |
| Removed | -- | -- | -- | IPv6-in-IPv6 | -- |
| headers | | | | (RH3,RPI)(1) | |
| Re- | -- | -- | -- | -- | -- |
| added | | | | | |
| headers | | | | | |
| Modifie | -- | -- | IPv6-in- | IPv6-in-IPv6 | -- |
| d | | | IPv6 | (RH3, RPI) | |
| headers | | | (RH3,RPI) | | |
| Untouch | -- | -- | -- | -- | -- |
| ed | | | | | |
| headers | | | | | |
+---------+--------+------------+------------+---------------+------+
Table 20: NonStoring: Summary of the use of headers from Internet to
non-RPL-aware-leaf (1) The last 6LR before the IPv6 node.
7.3. Non-Storing Mode: Interaction between Leafs
In this section is described the communication flow in Non Storing
Mode (Non-SM) between,
RPL-aware-leaf to RPL-aware-leaf
RPL-aware-leaf to not-RPL-aware-leaf
not-RPL-aware-leaf to RPL-aware-leaf
not-RPL-aware-leaf to not-RPL-aware-leaf
7.3.1. Non-SM: Example of Flow from RPL-aware-leaf to RPL-aware-leaf
In this case the flow comprises:
6LN src --> 6LR_ia --> root (6LBR) --> 6LR_id --> 6LN dst
For example, a communication flow could be: Node F --> Node D -->
Node B --> Node A (root) --> Node B --> Node E --> Node H
6LR_ia are the intermediate routers from source to the root In this
case, "1 <= ia <= n", n is the number of routers (6LR) that the
packet go through from 6LN to the root.
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6LR_id are the intermediate routers from the root to the destination.
In this case, "1 <= ia <= m", m is the number of the intermediate
routers (6LR).
This case involves only nodes in same RPL Domain. The originating
node will add a RPI header to the original packet, and send the
packet upwards.
The originating node should put the RPI into an IPv6-in-IPv6 header
addressed to the root, so that the 6LBR can remove that header. If
it does not, then additional resources are wasted on the way down to
carry the useless RPI option.
The 6LBR will need to insert an RH3 header, which requires that it
add an IPv6-in-IPv6 header. It should be able to remove the RPI, as
it was contained in an IPv6-in-IPv6 header addressed to it.
Otherwise, there may be a RPI header buried inside the inner IP
header, which should get ignored.
Networks that use the RPL P2P extension [RFC6997] are essentially
non-storing DODAGs and fall into this scenario or scenario
Section 7.1.2, with the originating node acting as 6LBR.
+---------+------------+-------+-------------+--------+-------------+
| Header | 6LN src | 6LR_i | 6LBR | 6LR_id | 6LN dst |
| | | a | | | |
+---------+------------+-------+-------------+--------+-------------+
| Inserte | IPv6-in- | -- | IPv6-in- | -- | -- |
| d | IPv6 | | IPv6 | | |
| headers | (RPI1) | | (RH3->6LN, | | |
| | | | opt RPI2) | | |
| Removed | -- | -- | IPv6-in- | -- | IPv6-in- |
| headers | | | IPv6 (RPI1) | | IPv6 (RH3, |
| | | | | | opt RPI2) |
| Re- | -- | -- | -- | -- | -- |
| added | | | | | |
| headers | | | | | |
| Modifie | -- | RPI1 | -- | RPI2 | -- |
| d | | | | | |
| headers | | | | | |
| Untouch | -- | -- | -- | -- | -- |
| ed | | | | | |
| headers | | | | | |
+---------+------------+-------+-------------+--------+-------------+
Table 21: Non Storing: Summary of the use of headers for RPL-aware-
leaf to RPL-aware-leaf
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7.3.2. Non-SM: Example of Flow from RPL-aware-leaf to not-RPL-aware-
leaf
In this case the flow comprises:
6LN --> 6LR_ia --> root (6LBR) --> 6LR_id --> not-RPL-aware (IPv6)
For example, a communication flow could be: Node F --> Node D -->
Node B --> Node A (root) --> Node B --> Node E --> Node G
6LR_ia are the intermediate routers from source to the root In this
case, "1 <= ia <= n", n is the number of intermediate routers (6LR)
6LR_id are the intermediate routers from the root to the destination.
In this case, "1 <= ia <= m", m is the number of the intermediate
routers (6LR).
As in the previous case, the 6LN will insert a RPI (RPI_1) header
which must be in an IPv6-in-IPv6 header addressed to the root so that
the 6LBR can remove this RPI. The 6LBR will then insert an RH3
inside a new IPv6-in-IPv6 header addressed to the 6LR_id. The RPI is
optional from 6LBR to 6LR_id (RPI_2).
+---------+-----------+-----------+------------+------------+-------+
| Header | 6LN | 6LR_1 | 6LBR | 6LR_id | IPv6 |
+---------+-----------+-----------+------------+------------+-------+
| Inserte | IPv6-in- | -- | IPv6-in- | -- | -- |
| d | IPv6 | | IPv6 (RH3, | | |
| headers | (RPI1) | | opt RPI_2) | | |
| Removed | -- | -- | IPv6-in- | IPv6-in- | -- |
| headers | | | IPv6 | IPv6 (RH3, | |
| | | | (RPI_1) | opt RPI_2) | |
| Re- | -- | -- | -- | -- | -- |
| added | | | | | |
| headers | | | | | |
| Modifie | -- | IPv6-in- | -- | IPv6-in- | -- |
| d | | IPv6 | | IPv6 (RH3, | |
| headers | | (RPI_1) | | opt RPI_2) | |
| Untouch | -- | -- | -- | -- | opt |
| ed | | | | | RPI_2 |
| headers | | | | | |
+---------+-----------+-----------+------------+------------+-------+
Table 22: Non Storing: Summary of the use of headers from RPL-aware-
leaf to not-RPL-aware-leaf
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7.3.3. Non-SM: Example of Flow from not-RPL-aware-leaf to RPL-aware-
leaf
In this case the flow comprises:
not-RPL-aware 6LN (IPv6) --> 6LR_ia --> root (6LBR) --> 6LR_id -->
6LN
For example, a communication flow could be: Node G --> Node E -->
Node B --> Node A (root) --> Node B --> Node E --> Node H
6LR_ia are the intermediate routers from source to the root. In this
case, "1 <= ia <= n", n is the number of intermediate routers (6LR)
6LR_id are the intermediate routers from the root to the destination.
In this case, "1 <= ia <= m", m is the number of the intermediate
routers (6LR).
This scenario is mostly identical to the previous one. The RPI is
added by the first 6LR (6LR_1) inside an IPv6-in-IPv6 header
addressed to the root. The 6LBR will remove this RPI, and add it's
own IPv6-in-IPv6 header containing an RH3 header and optional RPI
(RPI_2).
+---------+-----+------------+------------+------------+------------+
| Header | IPv | 6LR_1 | 6LBR | 6LR_id | 6LN |
| | 6 | | | | |
+---------+-----+------------+------------+------------+------------+
| Inserte | -- | IPv6-in- | IPv6-in- | -- | -- |
| d | | IPv6 | IPv6 (RH3, | | |
| headers | | (RPI_1) | opt RPI_2) | | |
| Removed | -- | -- | IPv6-in- | -- | IPv6-in- |
| headers | | | IPv6 | | IPv6 (RH3, |
| | | | (RPI_1) | | opt RPI_2) |
| Re- | -- | -- | -- | -- | -- |
| added | | | | | |
| headers | | | | | |
| Modifie | -- | -- | -- | IPv6-in- | -- |
| d | | | | IPv6 (RH3, | |
| headers | | | | opt RPI_2) | |
| Untouch | -- | -- | -- | -- | -- |
| ed | | | | | |
| headers | | | | | |
+---------+-----+------------+------------+------------+------------+
Table 23: Non Storing: Summary of the use of headers from not-RPL-
aware-leaf to RPL-aware-leaf
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7.3.4. Non-SM: Example of Flow from not-RPL-aware-leaf to not-RPL-
aware-leaf
In this case the flow comprises:
not-RPL-aware 6LN (IPv6 src)--> 6LR_ia --> root (6LBR) --> 6LR_id -->
not-RPL-aware (IPv6 dst)
For example, a communication flow could be: Node G --> Node E -->
Node B --> Node A (root) --> Node C --> Node J
6LR_ia are the intermediate routers from source to the root. In this
case, "1 <= ia <= n", n is the number of intermediate routers (6LR)
6LR_id are the intermediate routers from the root to the destination.
In this case, "1 <= ia <= m", m is the number of the intermediate
routers (6LR).
This scenario is the combination of the previous two cases.
+----------+-----+-------------+--------------+--------------+------+
| Header | IPv | 6LR_1 | 6LBR | 6LR_id | IPv6 |
| | 6 | | | | dst |
| | src | | | | |
+----------+-----+-------------+--------------+--------------+------+
| Inserted | -- | IPv6-in- | IPv6-in-IPv6 | -- | -- |
| headers | | IPv6 | (RH3, opt | | |
| | | (RPI_1) | RPI_2) | | |
| Removed | -- | -- | IPv6-in-IPv6 | IPv6-in-IPv6 | -- |
| headers | | | (RPI_1) | (RH3, opt | |
| | | | | RPI_2) | |
| Re-added | -- | -- | -- | -- | -- |
| headers | | | | | |
| Modified | -- | -- | -- | -- | -- |
| headers | | | | | |
| Untouche | -- | -- | -- | -- | -- |
| d | | | | | |
| headers | | | | | |
+----------+-----+-------------+--------------+--------------+------+
Table 24: Non Storing: Summary of the use of headers from not-RPL-
aware-leaf to not-RPL-aware-leaf
8. Operational Considerations of supporting not-RPL-aware-leaves
Roughly half of the situations described in this document involve
leaf ("host") nodes that do not speak RPL. These nodes fall into two
further categories: ones that drop a packet that have RPI or RH3
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headers, and ones that continue to process a packet that has RPI and/
or RH3 headers.
[RFC8200] provides for new rules that suggest that nodes that have
not been configured (explicitly) to examine Hop-by-Hop headers,
should ignore those headers, and continue processing the packet.
Despite this, and despite the switch from 0x63 to 0x23, there may be
hosts that are pre-RFC8200, or simply intolerant. Those hosts will
drop packets that continue to have RPL artifacts in them. In
general, such hosts can not be easily supported in RPL LLNs.
There are some specific cases where it is possible to remove the RPL
artifacts prior to forwarding the packet to the leaf host. The
critical thing is that the artifacts have been inserted by the RPL
root inside an IPv6-in-IPv6 header, and that the header has been
addressed to the 6LR immediately prior to the leaf node. In that
case, in the process of removing the IPv6-in-IPv6 header, the
artifacts can also be removed.
The above case occurs whenever traffic originates from the outside
the LLN (the "Internet" cases above), and non-storing mode is used.
In non-storing mode, the RPL root knows the exact topology (as it
must be create the RH3 header), and therefore knows what the 6LR
prior to the leaf --- the 6LR_n.
Traffic originating from the RPL root (such as when the data
collection system is co-located on the RPL root), does not require an
IPv6-in-IPv6 header (in either mode), as the packet is originating at
the root, and the root can insert the RPI and RH3 headers directly
into the packet, as it is formed. Such a packet is slightly smaller,
but only can be sent to nodes (whether RPL aware or not), that will
tolerate the RPL artifacts.
An operator that finds itself with a lot of traffic from the RPL root
to RPL-not-aware-leaves, will have to do IPv6-in-IPv6 encapsulation
if the leaf is not tolerant of the RPL artifacts. Such an operator
could otherwise omit this unnecessary header if it was certain of the
properties of the leaf.
As storing mode can not know the final path of the traffic,
intolerant (that drop packets with RPL artifacts) leaf nodes can not
be supported.
9. Operational considerations of introducing 0x23
This section describes the operational considerations of introducing
the new RPI value of 0x23.
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Related to the deployment of RPL, there are no known multivendor
deployments outside of the research groups! All known deployments of
RPL are in market verticals, with a single vendor providing all
components. Research groups typically are using Contiki, RiotOS, or
OpenWSN, and these are easily adapted to 0x23 functionality.
During bootstrapping the node get the DIO with the information of RPL
Option Type, indicating the new RPI in the DODAG Configuration Option
Flag. The DODAG root is in charge to configure the current network
to the new value, through DIO messages and when all the nodes are set
with the new value. The DODAG should change to a new DODAG version.
In case of rebooting, the node does not remember the RPL Option Type.
Thus, the DIO is sent with a flag indicating the new RPI value.
The migration path to the change from 0x63 to 0x23 in networks that
accepts both values is changed when the DIO is sent with the flag
indicating the new RPI value. Namely, it remains at 0x63 until it is
sure that the network is capable of 0x23, then it abruptly change to
0x23. This options allows to send packets to non-RPL nodes, which
should ignore the option and continue processing the packets.
In case that a node join to a network that only process 0x63, it
would produce a flag day as was mentioned previously. Indicating the
new RPI in the DODAG Configuration Option Flag is a way to avoid the
flag day in a network. It is recommended that a network process both
options to enable interoperability.
10. IANA Considerations
This document updates the registration made in [RFC6553] Destination
Options and Hop-by-Hop Options registry from 0x63 to 0x23.
[RFCXXXX] represents this document.
Hex Value Binary Value
act chg rest Description Reference
--------- --- --- ------- ----------------- ----------
0x23 00 1 00011 RPL Option [RFCXXXX]
0x63 01 1 00011 RPL Option(DEPRECATED) [RFC6553][RFCXXXX]
Figure 9: Option Type in RPL Option.
The DODAG Configuration Option Flags in the DODAG Configuration
option is updated as follows:
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+------------+-----------------+---------------+
| Bit number | Description | Reference |
+------------+-----------------+---------------+
| 3 | RPI 0x23 enable | This document |
+------------+-----------------+---------------+
Figure 10: DODAG Configuration Option Flag to indicate the RPI-flag-
day.
11. Security Considerations
The security considerations covered in [RFC6553] and [RFC6554] apply
when the packets are in the RPL Domain.
The IPv6-in-IPv6 mechanism described in this document is much more
limited than the general mechanism described in [RFC2473]. The
willingness of each node in the LLN to decapsulate packets and
forward them could be exploited by nodes to disguise the origin of an
attack.
While a typical LLN may be a very poor origin for attack traffic (as
the networks tend to be very slow, and the nodes often have very low
duty cycles) given enough nodes, they could still have a significant
impact, particularly if the attack was on another LLN! Additionally,
some uses of RPL involve large backbone ISP scale equipment
[I-D.ietf-anima-autonomic-control-plane], which may be equipped with
multiple 100Gb/s interfaces.
Blocking or careful filtering of IPv6-in-IPv6 traffic entering the
LLN as described above will make sure that any attack that is mounted
must originate from compromised nodes within the LLN. The use of
BCP38 filtering at the RPL root on egress traffic will both alert the
operator to the existence of the attack, as well as drop the attack
traffic. As the RPL network is typically numbered from a single
prefix, which is itself assigned by RPL, BCP38 filtering involves a
single prefix comparison and should be trivial to automatically
configure.
There are some scenarios where IPv6-in-IPv6 traffic should be allowed
to pass through the RPL root, such as the IPv6-in-IPv6 mediated
communications between a new Pledge and the Join Registrar/
Coordinator (JRC) when using [I-D.ietf-anima-bootstrapping-keyinfra]
and [I-D.ietf-6tisch-dtsecurity-secure-join]. This is the case for
the RPL root to do careful filtering: it occurs only when the Join
Coordinator is not co-located inside the RPL root.
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With the above precautions, an attack using IPv6-in-IPv6 tunnels will
be by a node within the LLN on another node within the LLN. Such an
attack could, of course, be done directly. An attack of this kind is
meaningful only if the source addresses are either fake or if the
point is to amplify return traffic. Such an attack, could also be
done without the use of IPv6-in-IPv6 headers using forged source
addresses. If the attack requires bi-directional communication, then
IPv6-in-IPv6 provides no advantages.
[RFC2473] suggests that tunnel entry and exit points can be secured,
via the "Use IPsec". The suggested solution has all the problems
that [RFC5406] goes into. In an LLN such a solution would degenerate
into every node having a tunnel with every other node. It would
provide a small amount of origin address authentication at a very
high cost; doing BCP38 at every node (linking layer-3 addresses to
layer-2 addresses, and to already present layer-2 cryptographic
mechanisms) would be cheaper should RPL be run in an environment
where hostile nodes are likely to be a part of the LLN.
The RH3 header usage described here can be abused in equivalent ways
with an IPv6-in-IPv6 header to add the needed RH3 header. As such,
the attacker's RH3 header will not be seen by the network until it
reaches the end host, which will decapsulate it. An end-host should
be suspicious about a RH3 header which has additional hops which have
not yet been processed, and SHOULD ignore such a second RH3 header.
In addition, the LLN will likely use [RFC8138] to compress the IPv6-
in-IPv6 and RH3 headers. As such, the compressor at the RPL-root
will see the second RH3 header and MAY choose to discard the packet
if the RH3 header has not been completely consumed. A consumed
(inert) RH3 header could be present in a packet that flows from one
LLN, crosses the Internet, and enters another LLN. As per the
discussion in this document, such headers do not need to be removed.
However, there is no case described in this document where an RH3 is
inserted in a non-storing network on traffic that is leaving the LLN,
but this document should not preclude such a future innovation. It
should just be noted that an incoming RH3 must be fully consumed, or
very carefully inspected.
The RPI header, if permitted to enter the LLN, could be used by an
attacker to change the priority of a packet by selecting a different
RPLInstanceID, perhaps one with a higher energy cost, for instance.
It could also be that not all nodes are reachable in an LLN using the
default instanceID, but a change of instanceID would permit an
attacker to bypass such filtering. Like the RH3, a RPI header is to
be inserted by the RPL root on traffic entering the LLN by first
inserting an IPv6-in-IPv6 header. The attacker's RPI header
therefore will not be seen by the network. Upon reaching the
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destination node the RPI header has no further meaning and is just
skipped; the presence of a second RPI header will have no meaning to
the end node as the packet has already been identified as being at
it's final destination.
The RH3 and RPI headers could be abused by an attacker inside of the
network to route packets on non-obvious ways, perhaps eluding
observation. This usage is in fact part of [RFC6997] and can not be
restricted at all. This is a feature, not a bug.
[RFC7416] deals with many other threats to LLNs not directly related
to the use of IPv6-in-IPv6 headers, and this document does not change
that analysis.
Nodes within the LLN can use the IPv6-in-IPv6 mechanism to mount an
attack on another part of the LLN, while disguising the origin of the
attack. The mechanism can even be abused to make it appear that the
attack is coming from outside the LLN, and unless countered, this
could be used to mount a Distributed Denial Of Service attack upon
nodes elsewhere in the Internet. See [DDOS-KREBS] for an example of
such attacks already seen in the real world.
If an attack comes from inside of LLN, it can be alleviated with SAVI
(Source Address Validation Improvement) using [RFC8505] with
[I-D.ietf-6lo-ap-nd]. The attacker will not be able to source with
an address that is not registered, and the registration checks for
topological correctness. Notice that there is an L2 authentication
in most of the cases. If an attack comes from outside LLN IPv6-in-
IPv6 can be used to hide inner routing headers, but RH3 is protected
by its definition.
Nodes outside of the LLN will need to pass IPv6-in-IPv6 traffic
through the RPL root to perform this attack. To counter, the RPL
root SHOULD either restrict ingress of IPv6-in-IPv6 packets (the
simpler solution), or it SHOULD do a deep packet inspection wherein
it walks the IP header extension chain until it can inspect the
upper-layer-payload as described in [RFC7045]. In particular, the
RPL root SHOULD do BCP38 ([RFC2827]) processing on the source
addresses of all IP headers that it examines in both directions.
Note: there are some situations where a prefix will spread across
multiple LLNs via mechanisms such as the one described in
[I-D.ietf-6lo-backbone-router]. In this case the BCP38 filtering
needs to take this into account, either by exchanging detailed
routing information on each LLN, or by moving the BCP38 filtering
further towards the Internet, so that the details of the multiple
LLNs do not matter.
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12. Acknowledgments
We are very thankful to the grant by the Finnish Foundation for
Technology Promotion (Tekniikan Edistaemissaeaetioen - TES), and the
grant by the FP7 Marie Curie Initial Training Network (ITN) METRICS
project (grant agreement No. 607728)
A special BIG thanks to C. M. Heard for the help with the
Section 3. Much of the redaction in that section is based on his
comments.
Additionally, the authors would like to acknowledge the review,
feedback, and comments of (alphabetical order): Robert Cragie, Simon
Duquennoy, Ralph Droms, Cenk Guendogan, Rahul Jadhav, Matthias
Kovatsch, Peter van der Stok, Xavier Vilajosana and Thomas Watteyne.
13. References
13.1. 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>.
[RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP Source
Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827,
May 2000, <https://www.rfc-editor.org/info/rfc2827>.
[RFC6550] 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>.
[RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low-
Power and Lossy Networks (RPL) Option for Carrying RPL
Information in Data-Plane Datagrams", RFC 6553,
DOI 10.17487/RFC6553, March 2012,
<https://www.rfc-editor.org/info/rfc6553>.
[RFC6554] Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6
Routing Header for Source Routes with the Routing Protocol
for Low-Power and Lossy Networks (RPL)", RFC 6554,
DOI 10.17487/RFC6554, March 2012,
<https://www.rfc-editor.org/info/rfc6554>.
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[RFC7045] Carpenter, B. and S. Jiang, "Transmission and Processing
of IPv6 Extension Headers", RFC 7045,
DOI 10.17487/RFC7045, December 2013,
<https://www.rfc-editor.org/info/rfc7045>.
[RFC8138] Thubert, P., Ed., Bormann, C., Toutain, L., and R. Cragie,
"IPv6 over Low-Power Wireless Personal Area Network
(6LoWPAN) Routing Header", RFC 8138, DOI 10.17487/RFC8138,
April 2017, <https://www.rfc-editor.org/info/rfc8138>.
[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>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
13.2. Informative References
[DDOS-KREBS]
Goodin, D., "Record-breaking DDoS reportedly delivered by
>145k hacked cameras", September 2016,
<http://arstechnica.com/security/2016/09/botnet-of-145k-
cameras-reportedly-deliver-internets-biggest-ddos-ever/>.
[I-D.ietf-6lo-ap-nd]
Thubert, P., Sarikaya, B., Sethi, M., and R. Struik,
"Address Protected Neighbor Discovery for Low-power and
Lossy Networks", draft-ietf-6lo-ap-nd-11 (work in
progress), February 2019.
[I-D.ietf-6lo-backbone-router]
Thubert, P., Perkins, C., and E. Levy-Abegnoli, "IPv6
Backbone Router", draft-ietf-6lo-backbone-router-11 (work
in progress), February 2019.
[I-D.ietf-6tisch-dtsecurity-secure-join]
Richardson, M., "6tisch Secure Join protocol", draft-ietf-
6tisch-dtsecurity-secure-join-01 (work in progress),
February 2017.
[I-D.ietf-anima-autonomic-control-plane]
Eckert, T., Behringer, M., and S. Bjarnason, "An Autonomic
Control Plane (ACP)", draft-ietf-anima-autonomic-control-
plane-18 (work in progress), August 2018.
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[I-D.ietf-anima-bootstrapping-keyinfra]
Pritikin, M., Richardson, M., Behringer, M., Bjarnason,
S., and K. Watsen, "Bootstrapping Remote Secure Key
Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-
keyinfra-19 (work in progress), March 2019.
[I-D.thubert-roll-unaware-leaves]
Thubert, P., "Routing for RPL Leaves", draft-thubert-roll-
unaware-leaves-06 (work in progress), November 2018.
[RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473,
December 1998, <https://www.rfc-editor.org/info/rfc2473>.
[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", STD 89,
RFC 4443, DOI 10.17487/RFC4443, March 2006,
<https://www.rfc-editor.org/info/rfc4443>.
[RFC5406] Bellovin, S., "Guidelines for Specifying the Use of IPsec
Version 2", BCP 146, RFC 5406, DOI 10.17487/RFC5406,
February 2009, <https://www.rfc-editor.org/info/rfc5406>.
[RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
Bormann, "Neighbor Discovery Optimization for IPv6 over
Low-Power Wireless Personal Area Networks (6LoWPANs)",
RFC 6775, DOI 10.17487/RFC6775, November 2012,
<https://www.rfc-editor.org/info/rfc6775>.
[RFC6997] Goyal, M., Ed., Baccelli, E., Philipp, M., Brandt, A., and
J. Martocci, "Reactive Discovery of Point-to-Point Routes
in Low-Power and Lossy Networks", RFC 6997,
DOI 10.17487/RFC6997, August 2013,
<https://www.rfc-editor.org/info/rfc6997>.
[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>.
[RFC7416] Tsao, T., Alexander, R., Dohler, M., Daza, V., Lozano, A.,
and M. Richardson, Ed., "A Security Threat Analysis for
the Routing Protocol for Low-Power and Lossy Networks
(RPLs)", RFC 7416, DOI 10.17487/RFC7416, January 2015,
<https://www.rfc-editor.org/info/rfc7416>.
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[RFC8180] Vilajosana, X., Ed., Pister, K., and T. Watteyne, "Minimal
IPv6 over the TSCH Mode of IEEE 802.15.4e (6TiSCH)
Configuration", BCP 210, RFC 8180, DOI 10.17487/RFC8180,
May 2017, <https://www.rfc-editor.org/info/rfc8180>.
[RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C.
Perkins, "Registration Extensions for IPv6 over Low-Power
Wireless Personal Area Network (6LoWPAN) Neighbor
Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018,
<https://www.rfc-editor.org/info/rfc8505>.
Authors' Addresses
Maria Ines Robles
Aalto University
Innopoli
Espoo 02150
Finland
Email: mariainesrobles@gmail.com
Michael C. Richardson
Sandelman Software Works
470 Dawson Avenue
Ottawa, ON K1Z 5V7
CA
Email: mcr+ietf@sandelman.ca
URI: http://www.sandelman.ca/mcr/
Pascal Thubert
Cisco Systems, Inc
Village d'Entreprises Green Side 400, Avenue de Roumanille
Batiment T3, Biot - Sophia Antipolis 06410
France
Email: pthubert@cisco.com
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