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roll-useofrplinfo-04.txt
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ROLL Working Group M. Robles
Internet-Draft Ericsson
Intended status: Informational M. Richardson
Expires: October 7, 2016 SSW
P. Thubert
Cisco
April 5, 2016
When to use RFC 6553, 6554 and IPv6-in-IPv6
draft-ietf-roll-useofrplinfo-04
Abstract
This document looks at different data flows through LLN networks
where RPL is used to establish routing. The document enumerates the
cases where RFC 6553, RFC 6554 and IPv6-in-IPv6 encapsulation is
required. This analysis provides the basis on which to design
efficient compression of these headers.
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 http://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 October 7, 2016.
Copyright Notice
Copyright (c) 2016 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
(http://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
Robles, et al. Expires October 7, 2016 [Page 1]
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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
2. Terminology and Requirements Language . . . . . . . . . . . . 3
3. Sample/reference topology . . . . . . . . . . . . . . . . . . 3
4. Use cases . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Storing mode . . . . . . . . . . . . . . . . . . . . . . . . 8
5.1. Example of Flow from RPL-aware-leaf to root . . . . . . . 9
5.2. Example of Flow from root to RPL-aware-leaf . . . . . . . 9
5.3. Example of Flow from root to not-RPL-aware-leaf . . . . . 10
5.4. Example of Flow from not-RPL-aware-leaf to root . . . . . 11
5.5. Example of Flow from RPL-aware-leaf to Internet . . . . . 11
5.6. Example of Flow from Internet to RPL-aware-leaf . . . . . 12
5.7. Example of Flow from not-RPL-aware-leaf to Internet . . . 12
5.8. Example of Flow from Internet to non-RPL-aware-leaf . . . 13
5.9. Example of Flow from RPL-aware-leaf to RPL-aware-leaf . . 14
5.10. Example of Flow from RPL-aware-leaf to non-RPL-aware-leaf 15
5.11. Example of Flow from not-RPL-aware-leaf to RPL-aware-leaf 17
5.12. Example of Flow from not-RPL-aware-leaf to not-RPL-aware-
leaf . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6. Non Storing mode . . . . . . . . . . . . . . . . . . . . . . 19
6.1. Example of Flow from RPL-aware-leaf to root . . . . . . . 19
6.2. Example of Flow from root to RPL-aware-leaf . . . . . . . 20
6.3. Example of Flow from root to not-RPL-aware-leaf . . . . . 20
6.4. Example of Flow from not-RPL-aware-leaf to root . . . . . 21
6.5. Example of Flow from RPL-aware-leaf to Internet . . . . . 22
6.6. Example of Flow from Internet to RPL-aware-leaf . . . . . 22
6.7. Example of Flow from not-RPL-aware-leaf to Internet . . . 23
6.8. Example of Flow from Internet to non-RPL-aware-leaf . . . 23
6.9. Example of Flow from RPL-aware-leaf to RPL-aware-leaf . . 24
6.10. Example of Flow from RPL-aware-leaf to not-RPL-aware-leaf 25
6.11. Example of Flow from not-RPL-aware-leaf to RPL-aware-leaf 26
6.12. Example of Flow from not-RPL-aware-leaf to not-RPL-aware-
leaf . . . . . . . . . . . . . . . . . . . . . . . . . . 26
7. Observations about the problem . . . . . . . . . . . . . . . 27
7.1. Storing mode . . . . . . . . . . . . . . . . . . . . . . 27
7.2. Non-Storing mode . . . . . . . . . . . . . . . . . . . . 28
8. 6LoRH Compression cases . . . . . . . . . . . . . . . . . . . 28
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
10. Security Considerations . . . . . . . . . . . . . . . . . . . 29
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 29
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 29
12.1. Normative References . . . . . . . . . . . . . . . . . . 29
12.2. Informative References . . . . . . . . . . . . . . . . . 30
Robles, et al. Expires October 7, 2016 [Page 2]
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Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30
1. Introduction
RPL [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.
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 should not be defining anything new, but
it may clarify what is correct and incorrect behaviour.
The related document A Routing Header Dispatch for 6LoWPAN (6LoRH)
[I-D.ietf-roll-routing-dispatch] defines a method to compress RPL
Option information and Routing Header type 3 (RFC6554) and an
efficient IP-in-IP technique. Uses cases proposed for the
[Second6TischPlugtest] involving 6loRH.
2. Terminology and Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Terminology defined in [RFC7102]
3. Sample/reference topology
A RPL network 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 (Destination Oriented
Directed Acyclic Graph).
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RPL defines the RPL Control messages (control plane ), a new ICMPv6
message with Type 155. DIS, DIO and DAO messages are all RPL Control
messages but with different Code values.
RPL supports two modes of Downward traffic: in storing mode, it is
fully stateful or an in non-storing, 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.
+--------------+
| Upper Layers |
| |
+--------------+
| RPL |
| |
+--------------+
| ICMPv6 |
| |
+--------------+
| IPv6 |
| |
+--------------+
| 6LoWPAN |
| |
+--------------+
| PHY-MAC |
| |
+--------------+
Figure 1: RPL Stack.
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+---------+
+---+Internet |
| +---------+
|
+----+--+
|DODAG | node:01
+---------+Root +----------+
| |6LBR | |
| +----+--+ |
| | |
| | |
... ... ...
| | |
+-----+-+ +--+---+ +--+---+
|6LR | | | | |
+-----+ | | | | |
| | 11 | | 12 | | 13 +------+
| +-----+-+ +-+----+ +-+----+ |
| | | | |
| | | | |
| 21 | 22 | 23 | 24 | 25
+-+---+ +-+---+ +--+--+ +- --+ +---+-+
|Leaf | | | | | |Leaf| |Leaf |
| 6LR | | | | | | 6LN| | 6LR |
+-----+ +-----+ +-----+ +----+ +-----+
Figure 2: A reference RPL Topology.
The numbers in or above the nodes are there so that they may be
referenced in subsequent sections. The leaf marked 6LN (24) is a
device which does not speak RPL at all, but uses Router-
Advertisements, 6LowPAN DAR/DAC and efficient-ND only to participate
in the network.
This document is in part motivated by the work that is ongoing at the
6TiSCH working group. The 6TiSCH architecture
[I-D.ietf-6tisch-architecture] draft explains the network
architecture of a 6TiSCH network. This architecture is used for the
remainder of this document.
The scope of the 6TiSCH Architecture is a Backbone Link that
federates multiple LLNs (mesh) as a single IPv6 Multi-Link Subnet.
Each LLN in the subnet is anchored at a Backbone Router (6BBR). The
Backbone Routers interconnect the LLNs over the Backbone Link and
emulate that the LLN nodes are present on the Backbone thus creating
a so-called: Multi-Link Subnet. An LLN node can move freely from an
LLN anchored at a Backbone Router to another LLN anchored at the same
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or a different Backbone Router inside the Multi-Link Subnet and
conserve its addresses.
|
+-----+
| | Border Router to the RPL domain
| | (may be a RPL virtual root)
+-----+
|
| Backbone
+-------------------+-------------------+
| | |
+-----+ +-----+ +-----+
| | Backbone | | Backbone | | Backbone
| | router | | router | | router
+|---|+ +-|||-+ +-[_]-+
| | PCI-exp / | \ USB | Ethernet
( ) ( ) ( )( )( ) (6LBR == RPL DODAG root)
o o o o o o o o o o o o
o o o o o o o o o o o o o o o o
o o o o o o o o o o 6LR == RPL router) o o
o o o o o o o z
o o o o o o (6LoWPAN Host)
<----------------------- RPL Instance ------------------------>
Figure 3: RPL domain architecture
4. Use cases
In data plane context a combination of RFC6553, RFC6554 and IPv6-in-
IPv6 encapsulation is going to be analyzed for the following traffic
flows:
RPL-aware-leaf to root
root to RPL-aware-leaf
not-RPL-aware-leaf to root
root to not-RPL-aware-leaf
RPL-aware-leaf to Internet
Internet to RPL-aware-leaf
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not-RPL-aware-leaf to Internet
Internet to not-RPL-aware-leaf
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
This document assumes a 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
[RFC2460] is that Extensions may not be added or removed except by
the sender or the receiver.
A second important thing is that packets with a Hop-by-Hop option
which are marked with option type 01 ([RFC2460] section 4.2) must be
discarded if received by a host or router which does not understand
that option. This means that in general, any packet that leaves the
RPL domain of an LLN (or leaves the LLN entirely) is likely to be
discarded if it still contains an [RFC6553] RPL Option Header known
as the RPI.
The combination of these two rules means that the arrangement of
headers must be done so that traffic intended to exit the RPL domain
can have the RPI option removed prior to leaving the RPL domain.
An intermediate router that needs to add a header must encapsulate
the packet in an (additional) outer IP header where the new header
can be placed.
This also means that a Header can only be removed by an intermediate
router if it is placed in an encapsulating IPv6 Header, and in that
case, the whole encapsulating header must be removed - a replacement
may be added. Further, an intermediate router can only remove such
an outer header if that outer header has the router as the
destination!
Both RPI and RH3 headers may be modified 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 RH and the RPL option are marked mutable but recoverable, so
an IPsec AH security header can be applied across these headers, but
it may not secure all the values in those headers.
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RPI should be present in every single RPL data packet. There is one
exception in non-storing mode: when a packet is going down from the
route. 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. There may be cases (such as in
6tisch) where the instanceID may still be needed to pick an
appropriate priority or channel at each hop.
The applicability for storing (RPL-SN) and non-Storing (RPL-NSN)
modes for the previous cases is showed as follows:
In tables, the term "RPL aware leaf" is has been shortened to "Raf",
and "not-RPL aware leaf" has been shortened to "~Raf" to make the
table fit in available space.
The earlier examples are more complete to make sure that the process
is clear, while later examples are more consise.
5. Storing mode
This table summarizes what headers are needed in the following
scenarios, and indicates the IPIP header must be inserted on a hop-
by-hop basis, and when it can target the destination node directly.
There are three possible situations: hop-by-hop necessary (indicated
by "hop"), or destination address possible (indicated by "dst"). In
all cases hop by hop can be used. In cases where no IPIP header is
needed, the column is left blank.
+--------------+-------+-------+-----------+-----------+
| Use Case | RPI | RH3 | IP-in-IP | IPIP dst |
+--------------+-------+-------+-----------+-----------+
| Raf to root | Yes | No | No | -- |
| root to Raf | Yes | No | No | -- |
| root to ~Raf | Yes | No | Yes | hop |
| ~Raf to root | Yes | No | Yes | root |
| Raf to Int | Yes | No | Yes | root |
| Int to Raf | Yes | No | Yes | raf |
| ~Raf to Int | Yes | No | Yes | root |
| Int to ~Raf | Yes | No | Yes | hop |
| Raf to Raf | Yes | No | No | -- |
| Raf to ~Raf | Yes | No | Yes | hop |
| ~Raf to Raf | Yes | No | Yes | dst |
| ~Raf to ~Raf | Yes | No | Yes | hop |
+--------------+-------+-------+-----------+-----------+
Table 1: Headers needed in Storing mode: RPI, RH3, IP-in-IP
encapsulation
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5.1. Example of Flow from RPL-aware-leaf to root
As states 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 storing mode, it is suitable to use RFC 6553 (RPI) to send RPL
Information instanceID and rank information.
In this case the flow comprises:
RPL-aware-leaf (6LN) --> 6LR --> 6LR,... --> root (6LBR)
Note: In this document 6LRs, 6LBR are always full-fledge RPL routers,
and are the RPL root node.
The 6LN inserts the RPI header, and send the packet to 6LR which
decrement the rank in RPI and send the packet up. When the packet
arrives to 6LBR, the RPI is removed and the packet is processed.
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 in order to be able 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 | 6LBR |
+-------------------+-----+------+------+
| Inserted headers | RPI | -- | -- |
| Removed headers | -- | -- | RPI |
| Re-added headers | -- | -- | -- |
| Modified headers | -- | RPI | -- |
| Untouched headers | -- | -- | -- |
+-------------------+-----+------+------+
Storing: Summary of the use of headers from RPL-aware-leaf to root
5.2. Example of Flow from root to RPL-aware-leaf
In this case the flow comprises:
root (6LBR)--> 6LR --> RPL-aware-leaf (6LN)
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In this case the 6LBR insert RPI header and send the packet down, the
6LR is going to increment the rank in RPI (examines instanceID for
multiple tables), the packet is processed in 6LN and RPI removed.
No IPIP header is required.
+-------------------+------+-------+------+
| Header | 6LBR | 6LR | 6LN |
+-------------------+------+-------+------+
| Inserted headers | RPI | -- | -- |
| Removed headers | -- | -- | RPI |
| Re-added headers | -- | -- | -- |
| Modified headers | -- | RPI | -- |
| Untouched headers | -- | -- | -- |
+-------------------+------+-------+------+
Storing: Summary of the use of headers from root to RPL-aware-leaf
5.3. Example of Flow from root to not-RPL-aware-leaf
In this case the flow comprises:
root (6LBR)--> 6LR --> not-RPL-aware-leaf (6LN)
It includes IPv6-in-IPv6 encapsulation to transmit information not
related with the RPL domain. In the 6LBR the RPI header is inserted
into an IPv6-in-IPv6 header addressed to the last 6LR, which removes
the header before pass the packet to the IPv6 node.
The question in this scenario is how the root knows how to address
the IPv6-in-IPv6 header. It can not know that the destination isn't
RPL aware, so it must insert an IPv6 that can be removed on the last
RPL aware node. Since the root can not know in a storing network
where the last RPL aware node is, the IPv6-in-IPv6 header must added
hop-by-hop along the path from root to leaf.
An alternative option is to add an attribute in the RPL Target Option
to indicate that the target is not RPL aware: future work may explore
this possibility.
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+-------------------+-----------+-----------+------+
| Header | 6LBR | 6LR | IPv6 |
+-------------------+-----------+-----------+------+
| Inserted headers | IPIP(RPI) | -- | -- |
| Removed headers | -- | IPIP(RPI) | -- |
| Re-added headers | -- | -- | -- |
| Modified headers | -- | -- | -- |
| Untouched headers | -- | -- | -- |
+-------------------+-----------+-----------+------+
Storing: Summary of the use of headers from root to not-RPL-aware-
leaf
5.4. Example of Flow from not-RPL-aware-leaf to root
In this case the flow comprises:
not-RPL-aware-leaf (6LN) --> 6LR --> root (6LBR)
When the packet arrives from IPv6 node to 6LR, the 6LR will insert an
RPI header, encapsuladed in a IPv6-in-IPv6 header. The IPv6-in-IPv6
header can be addressed to the next hop, or to the root. The root
removes the header and process the packet.
+-------------------+------+------------+-----------+
| Header | IPv6 | 6LR | 6LBR |
+-------------------+------+------------+-----------+
| Inserted headers | -- | IPIP(RPI) | -- |
| Removed headers | -- | -- | IPIP(RPI) |
| Re-added headers | -- | -- | -- |
| Modified headers | -- | -- | -- |
| Untouched headers | -- | -- | -- |
+-------------------+------+------------+-----------+
Storing: Summary of the use of headers from not-RPL-aware-leaf to
root
5.5. Example of Flow from RPL-aware-leaf to Internet
RPL information from RFC 6553 should not go out to Internet as it
will cause the packet to be discarded at the first non-RPI aware
router. The 6LBR must be able to take this information out before
sending the packet upwards to the Internet. This requires the RPI
header be placed in an IPIP header that the root can remove.
In this case the flow comprises:
RPL-aware-leaf (6LN) --> 6LR --> root (6LBR) --> Internet
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The 6LN will insert the RPI in a IPv6-in-IPv6 in a outer header,
which may be addressed to the 6LBR (root), or alternatively, it could
be addressed hop-by-hop.
+-------------------+-----------+------+-----------+----------+
| Header | 6LN | 6LR | 6LBR | Internet |
+-------------------+-----------+------+-----------+----------+
| Inserted headers | IPIP(RPI) | -- | -- | -- |
| Removed headers | -- | -- | IPIP(RPI) | -- |
| Re-added headers | -- | -- | -- | -- |
| Modified headers | -- | RPI | -- | -- |
| Untouched headers | -- | -- | -- | -- |
+-------------------+-----------+------+-----------+----------+
Storing: Summary of the use of headers from RPL-aware-leaf to
Internet
5.6. Example of Flow from Internet to RPL-aware-leaf
In this case the flow comprises:
Internet --> root (6LBR) --> 6LR --> RPL-aware-leaf (6LN)
When the packet arrives from Internet to 6LBR the RPI header is added
in a outer IPv6-in-IPv6 header and send to 6LR, which modifies the
rank in the RPI. When the packet arrives 6LN the RPI header is
removed and the packet processed.
+-------------------+----------+------------+------+------------+
| Header | Internet | 6LBR | 6LR | 6LN |
+-------------------+----------+------------+------+------------+
| Inserted headers | -- | IPIP(RPI) | -- | -- |
| Removed headers | -- | -- | -- | IPIP(RPI) |
| Re-added headers | -- | -- | -- | -- |
| Modified headers | -- | -- | RPI | -- |
| Untouched headers | -- | -- | -- | -- |
+-------------------+----------+------------+------+------------+
Storing: Summary of the use of headers from Internet to RPL-aware-
leaf
5.7. Example of Flow from not-RPL-aware-leaf to Internet
In this case the flow comprises:
not-RPL-aware-leaf (6LN) --> 6LR --> root (6LBR) --> Internet
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The 6LR node will add an IPIP(RPI) header addressed either to the
root, or hop-by-hop such that the root can remove the RPI header
before passing upwards.
The originating node will ideally leave the IPv6 flow label as zero
so that it can be better compressed through the LLN, and the 6LBR
will set the flow label to a non-zero value when sending to the
Internet.
+-------------------+------+------------+------------+----------+
| Header | 6LN | 6LR | 6LBR | Internet |
+-------------------+------+------------+------------+----------+
| Inserted headers | -- | IPIP(RPI) | -- | -- |
| Removed headers | -- | -- | IPIP(RPI) | -- |
| Re-added headers | -- | -- | -- | -- |
| Modified headers | -- | -- | -- | -- |
| Untouched headers | -- | -- | -- | -- |
+-------------------+------+------------+------------+----------+
Storing: Summary of the use of headers from not-RPL-aware-leaf to
Internet
5.8. Example of Flow from Internet to non-RPL-aware-leaf
In this case the flow comprises:
Internet --> root (6LBR) --> 6LR --> not-RPL-aware-leaf (6LN)
The 6LBR will have to add an RPI header within an IPIP header. The
IPIP will need to be addressed hop-by-hop along the path as in
storing mode, the 6LBR has no idea if the 6LN is RPL aware or not,
nor what the closest attached 6LR node is.
The 6LBR MAY set the flow label on the inner IPIP header to zero in
order to aid in compression, as the packet will not emerge again from
the LLN.
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+-------------------+----------+------------+------------+------+
| Header | Internet | 6LBR | 6LR | IPv6 |
+-------------------+----------+------------+------------+------+
| Inserted headers | -- | IPIP(RPI) | -- | -- |
| Removed headers | -- | -- | IPIP(RPI) | -- |
| Re-added headers | -- | -- | -- | -- |
| Modified headers | -- | -- | -- | -- |
| Untouched headers | -- | -- | -- | -- |
+-------------------+----------+------------+------------+------+
Storing: Summary of the use of headers from Internet to non-RPL-
aware-leaf
5.9. 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. Section 9 in [RFC6550].
In this case the flow comprises:
6LN --> 6LR --> common parent (6LR) --> 6LR --> 6LN
This case is assumed in the same RPL Domain. In the common parent,
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 IPIP headers are necessary. The ability to do
this depends upon the sending know that the destination is: a) inside
the LLN, and b) RPL capable.
The sender can determine if the destination is inside the LLN by
looking if the destination address is matched by the DIO's PIO
option. This check may be modified by the use of backbone routers,
but in this case it is assumed that the backbone routers are RPL
capable and so can process the RPI header correctly.
The other check, that the destination is RPL capable is not currently
discernible by the sender. This information is necessary to
distinguish this test case from Section 5.10.
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+-------------+-------+---------------+---------------+-----+-------+
| Header | 6LN | 6LR | 6LR (common | 6LR | 6LN |
| | src | | parent) | | dst |
+-------------+-------+---------------+---------------+-----+-------+
| Inserted | RPI | -- | -- | -- | -- |
| headers | | | | | |
| Removed | -- | -- | -- | -- | RPI |
| headers | | | | | |
| Re-added | -- | -- | -- | -- | -- |
| headers | | | | | |
| Modified | -- | RPI | RPI | -- | -- |
| headers | | (decreasing | (increasing | | |
| | | rank) | rank) | | |
| Untouched | -- | -- | -- | -- | -- |
| headers | | | | | |
+-------------+-------+---------------+---------------+-----+-------+
Storing: Summary of the use of headers for RPL-aware-leaf to RPL-
aware-leaf
5.10. Example of Flow from RPL-aware-leaf to non-RPL-aware-leaf
In this case the flow comprises:
6LN --> 6LR --> common parent (6LR) --> 6LR --> not-RPL-aware 6LN
The sender, being aware out of band, that the receiver is not RPL
aware, sends adds an RPI header inside an IPIP header. The IPIP
header needs to be addressed on a hop-by-hop basis so that the last
6LR can remove the RPI header.
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,---.
/ \
( 6LR2 ) IP3,RPI,IP,ULP
,-" .
,-" `---' `.
,' `.
,---. ,-" `,---.
/ +" / \
( 6LR1 ) Remove the IP3,RPI( 6LR3 )
\ / \ /
/---' `---'|
/ IP2,RPI,IP,ULP \
/ |
/ \
,---+-. |
/ \ +--+----+
( 6LN ) | |
\ / | IPv6 | IP,ULP
`-----' | |
IP1,RPI,IP,ULP +-------+
Figure 4: Solution IPv6-in-IPv6 in each hop
Alternatively, if the definition of the Option Type field of RPL
Option '01' were changed so that it isn't a "discard if not
recognized", then no IPIP header would be necessary. This change is
an incompatible on-the-wire change and would require some kind of
flag day, possibly a change that is done simultaenously with an
updated 6LoRH compress.
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+-----------+-----------+-----------+------------+-----------+------+
| Header | 6LN | 6LR | 6LR | 6LR | IPv6 |
| | | | (common | | |
| | | | parent) | | |
+-----------+-----------+-----------+------------+-----------+------+
| Inserted | IPIP(RPI) | -- | -- | -- | -- |
| headers | | | | | |
| Removed | -- | -- | -- | IPIP(RPI) | -- |
| headers | | | | | |
| Re-added | -- | -- | -- | -- | -- |
| headers | | | | | |
| Modified | -- | IPIP(RPI) | IPIP(RPI) | -- | -- |
| headers | | | | | |
| Untouched | -- | -- | -- | -- | -- |
| headers | | | | | |
+-----------+-----------+-----------+------------+-----------+------+
Storing: Summary of the use of headers from RPL-aware-leaf to not-
RPL-aware-leaf
5.11. Example of Flow from not-RPL-aware-leaf to RPL-aware-leaf
In this case the flow comprises:
not-RPL-aware 6LN --> 6LR --> common parent (6LR) --> 6LR --> 6LN
The 6LR receives the packet from the the IPv6 node and inserts and
the RPI header encapsulated in IPv6-in-IPv6 header. The IPIP header
could be addresses to the 6LN if the destination is known to the RPL
aware, otherwise must send the packet using a hop-by-hop IPIP header.
Similar considerations apply from section Section 5.10.
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+-----------+------+-----------+------------+-----------+-----------+
| Header | IPv6 | 6LR | common | 6LR | 6LN |
| | | | parent | | |
| | | | (6LR) | | |
+-----------+------+-----------+------------+-----------+-----------+
| Inserted | -- | IPIP(RPI) | -- | -- | -- |
| headers | | | | | |
| Removed | -- | -- | -- | -- | IPIP(RPI) |
| headers | | | | | |
| Re-added | -- | -- | -- | -- | -- |
| headers | | | | | |
| Modified | -- | -- | IPIP(RPI) | IPIP(RPI) | -- |
| headers | | | | | |
| Untouched | -- | -- | -- | -- | -- |
| headers | | | | | |
+-----------+------+-----------+------------+-----------+-----------+
Storing: Summary of the use of headers from not-RPL-aware-leaf to
RPL-aware-leaf
5.12. Example of Flow from not-RPL-aware-leaf to not-RPL-aware-leaf
In this case the flow comprises:
not-RPL-aware 6LN (IPv6 node)--> 6LR --> root (6LBR) --> 6LR --> not-
RPL-aware 6LN (IPv6 node)
This flow combines the problems of the two previous sections. There
is no choice at the first 6LR: it must insert an RPI, and to do that
it must add an IPIP header. That IPIP header must be addressed on a
hop-by-hop basis.