ROLL Working Group                                             M. Robles
Internet-Draft                                                  Ericsson
Intended status: Informational                             M. Richardson
Expires: September 22, October 6, 2016                                             SSW
                                                              P. Thubert
                                                                   Cisco
                                                          March 21,
                                                           April 4, 2016

              When to use RFC 6553, 6554 and IPv6-in-IPv6
                    draft-ietf-roll-useofrplinfo-02
                    draft-ietf-roll-useofrplinfo-03

Abstract

   This document states 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 to set
   required.  This analysis provides the bases basis on which to help
   defining the design
   efficient compression of RPL routing information in LLN
   environments. these headers.

Status of This Memo

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   This Internet-Draft will expire on September 22, October 6, 2016.

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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 . . . . . . .   8   9
     5.2.  Example of Flow from root to RPL-aware-leaf . . . . . . .   9  10
     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 . . . . .  10  11
     5.5.  Example of Flow from RPL-aware-leaf to Internet . . . . .  11  12
     5.6.  Example of Flow from Internet to RPL-aware-leaf . . . . .  11  12
     5.7.  Example of Flow from not-RPL-aware-leaf to Internet . . .  12  13
     5.8.  Example of Flow from Internet to non-RPL-aware-leaf . . .  13  14
     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 . . . . .  21  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 . . .  24  23
     6.9.  Example of Flow from RPL-aware-leaf to RPL-aware-leaf . .  25  24
     6.10. Example of Flow from RPL-aware-leaf to not-RPL-aware-leaf  26  25
     6.11. Example of Flow from not-RPL-aware-leaf to RPL-aware-leaf  27  26
     6.12. Example of Flow from not-RPL-aware-leaf to not-RPL-aware-
           leaf  . . . . . . . . . . . . . . . . . . . . . . . . . .  27  26
   7.  Problem statement  Observations about the problem  . . . . . . . . . . . . . . .  27
     7.1.  Storing mode  . . . . . . . . . . . . . . . . . . . . . .  27
     7.2.  Non-Storing mode  . . . . . . . . . . . . . . . . . . . .  28
   8.  6LoRH Compression cases . . . . . . . . . . . . . . . . . . .  29  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

   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  30

1.  Introduction

   RPL [RFC6550] is a routing protocol for constrained networks.  RFC
   6553 [RFC6553] defines the "RPL option", option" (RPI), carried within the
   IPv6 Hop-
   by-Hop Hop-by-Hop header to quickly identify inconsistencies (loops) in
   the routing topology.  RFC 6554 [RFC6554] defines the "RPL Source
   Route Header", Header" (RH3), an IPv6 Extension Header to deliver datagrams
   within a RPL routing
   domain.

   Several discussions domain, particularly in non-storing mode.

   These various items are referred to as RPL artifacts, and they are
   seen on all of the ROLL/6lo/6TiSCH Mailing Lists took place
   focusing data-plane traffic that occurs in the definition of how to compress RPL Information routed
   networks; they do not in
   constrained environment.  ROLL Virtual Interim Meeting (02-2015)
   concluded that there general appear on the RPL control plane
   traffic at all which is a need to define how mostly hop-by-hop traffic (one exception
   being DAO messages in non-storing mode).

   It has become clear from attempts to use [RFC6553],
   [RFC6554] do multi-vendor
   interoperability, and IPv6-in-IPv6 encapsulation 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 able safely omitted, or removed.

   An interim meeting went through the 24 cases defined here to set 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 environment for compression and incorrect behaviour.

   The related document A Routing Header Dispatch for 6LoWPAN (6LoRH) [I-D.ietf-6lo-routing-dispatch]
   [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: When the packet travel inside
   the RPL domain, the IP 6loRH.

2.  Terminology and Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in IP 6LoRH is not be presented in the packet
   and when the packet travel outside a RPL domain, Ip in IP 6LoRH is
   present in the packet.

   This document is going to be focused in data plane messages and how
   can be transmitted within the above mentioned RFCs.

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 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).

   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.

                                    +---------+
                                +---+Internet |
                                |   +---------+
                                |
                           +----+--+
                           |DODAG  |  node:01
                 +---------+Root   +----------+
                 |         |6LBR   |          |
                 |         +----+--+          |
                 |              |             |
                 |              |             |
                ...            ...           ...
                 |              |             |
           +-----+-+         +--+---+      +--+---+
           |6LR    |         |      |      |      |
     +-----+       |         |      |      |      |
     |     |   11  |         |   12 |      |   13 +------+
     |     +-----+-+         +-+----+      +-+----+      |
     |           |             |             |           |
     |           |             |             |           |
     | 21        | 22          | 23          | 24        | 25
   +-+---+     +-+---+      +--+--+       +- --+     +---+-+
   |Leaf |     |     |      |     |       |Leaf|     |Leaf |
   |     |     |
   |6LN  | 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
   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:

      -Flow from

      RPL-aware-leaf to root

      -Flow from

      root to RPL-aware-leaf

      -Flow from

      not-RPL-aware-leaf to root

      -Flow from

      root to not-RPL-aware-leaf

      -Flow from

      RPL-aware-leaf to Internet

      -Flow from

      Internet to RPL-aware-leaf

      -Flow from
      not-RPL-aware-leaf to Internet

      -Flow from

      Internet to not-RPL-aware-leaf
      -Flow from

      RPL-aware-leaf to RPL-aware-leaf

      -Flow from

      RPL-aware-leaf to not-RPL-aware-leaf

      -Flow from

      not-RPL-aware-leaf to RPL-aware-leaf

      -Flow from

      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.

   This document recognizes that some headers  Further, an intermediate router can only remove such as a Routing Header
   or a Hop-by-Hop
   an outer header may be modified by routers on the path of the 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.

   The
   Both headers were designed with this modification in mind, and both
   the RPL RH and the RPL option are marked mutable but recoverable . recoverable, so
   an IPsec AH security header can be applied across these headers, but
   it may not secure all the values in those headers.

   RPI should be present in every single RPL data packet.  There is an one
   exception in non-storing mode, mode: when a packet is going down from the
   route:
   route.  In a downward non-storing mode, the entire route is written,
   so there are can be no loops of by construction, nor any confusion about
   which forwarding table to use (purpose of instanceID). 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      | RPL- RPI (RFC     | RPL- RH3 (RFC     | RPL-SN IP-in-IP | RPL- IPIP dst | RPL-
   | RPL-NSN               | 6553)        | 6554)        | SN          | SN          | IP-in-
   +---------------+--------------+--------------+----------+----------+
   | NSN Raf to root   | NSN Yes          | IP-in- No           | No       | --       | RPI
   | RH3 root to Raf   | IP Yes          | RPI No           | RH3 No       | IP --       |
   | root to ~Raf  | (RFC Yes          | (RFC No           | Yes      | hop      |
   | ~Raf to root  | Yes          | No           | 6553 Yes      | 6554 root     |
   | Raf to        | Yes          | No           | Yes      | root     | )
   | ) Internet      |              |              |          |          |
   +---------------+------+------+---------+--------+--------+---------+
   | RPL-aware- Internet to   | Yes          | No           | No      | Yes      | No     | No      |
   | leaf to root raf      |
   | Raf           |              |              |          |          |
   | root ~Raf to RPL-       | Yes          | No           | No      | Yes    | Yes      | No      |
   | aware-leaf root     |
   | Internet      |              |              |          |          |
   | not-RPL- Internet to   | Yes          | No           | Yes      | Yes hop      | No
   | Yes ~Raf          |              | aware-leaf to              |          |          |
   | Raf to Raf    | Yes          | No           | No       | root --       |
   | Raf to ~Raf   | Yes          | No           | Yes      | hop      |
   | root ~Raf to not- Raf   | Yes          | No           | Yes      | Yes dst      | Yes
   | ~Raf to ~Raf  | Yes          | No           | RPL-aware- Yes      | hop      |
   +---------------+--------------+--------------+----------+----------+

        Table 1: Headers needed in Storing mode: RPI, RH3, IP-in-IP
                               encapsulation

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 |
                 +-------------------+-----+------+------+
                 | leaf Inserted headers  | RPI | --   | --   |
                 | Removed headers   | --  | --   | RPL-aware- RPI  | Yes
                 | No Re-added headers  | Yes --  | Yes --   | No --   | Yes
                 | Modified headers  | leaf to       |      |      |         |        |        |         |
   | Internet --  | RPI  | --   |
                 | Untouched headers | --  | --   | --   | Internet
                 +-------------------+-----+------+------+

    Storing: Summary of the use of headers from RPL-aware-leaf to   | Yes  | No   | Yes     | Yes    | Yes    | Yes     |
   | RPL-aware-    |      |      |         |        |        |         |
   | leaf          |      |      |         |        |        |         |
   | not-RPL-      | Yes  | No   | Yes     | Yes    | No     | Yes     |
   | aware-leaf root

5.2.  Example of Flow from root to |      |      |         |        |        |         |
   | Internet      |      |      |         |        |        |         |
   | Internet RPL-aware-leaf

   In this case the flow comprises:

   root (6LBR)--> 6LR --> RPL-aware-leaf (6LN)

   In this case the 6LBR insert RPI header and send the packet down, the
   6LR is going to   | Yes  | increment the rank in RPI (examines instanceID for
   multiple tables), the packet is processed in 6LN and RPI removed.

   No IPIP header is required.

                +-------------------+------+-------+------+
                | Yes Header            | Yes 6LBR | Yes 6LR   | Yes 6LN  |
                +-------------------+------+-------+------+
                | not-RPL- Inserted headers  | RPI  | --    | --   |
                | Removed headers   | --   | --    | aware-leaf RPI  |
                | Re-added headers  | --   | --    | --   |
                | Modified headers  | RPL-aware- --   | Yes RPI   | No --   | No
                | Yes Untouched headers | Yes --   | Yes --    | --   | leaf
                +-------------------+------+-------+------+

    Storing: Summary of the use of headers from root to RPL-  |      |      |         |        |        |         |
   | aware-leaf    |      |      |         |        |        |         |
   | RPL-aware-    | Yes  | No   | Yes     | Yes    | Yes    | Yes     |
   | leaf RPL-aware-leaf

5.3.  Example of Flow from root to not-  |      |      |         |        |        |         |
   | RPL-aware-    |      |      |         |        |        |         |
   | leaf          |      |      |         |        |        |         |
   | not-RPL-      | Yes  | No   | Yes     | Yes    | Yes    | Yes     |
   | aware-leaf 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.

           +-------------------+-----------+-----------+------+
           | Header            | 6LBR      | 6LR       | IPv6 |
           +-------------------+-----------+-----------+------+
           | Inserted headers  | IPIP(RPI) | RPL-aware-    |      | --        | --   |
           | Removed headers   | --        | IPIP(RPI) | leaf --   |
           | Re-added headers  | --        | --        | --   |
           | Modified headers  | not-RPL- --        | Yes --        | No --   | Yes
           | Yes Untouched headers | Yes --        | Yes --        | --   | aware-leaf
           +-------------------+-----------+-----------+------+

    Storing: Summary of the use of headers from root to |      |      |         |        |        |         |
   | not-RPL-      |      |      |         |        |        |         |
   | aware-leaf    |      |      |         |        |        |         |
   +---------------+------+------+---------+--------+--------+---------+

   Table 1: Posibility to transmit in Storing or Non-Storing mode: RPI,
                        RH3, IP-in-IP encapsulation

5.  Storing mode

5.1. not-RPL-aware-
                                   leaf

5.4.  Example of Flow from RPL-aware-leaf not-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
   (In inconsistency a leaf node generates DIO with infinite rank, to
   fix it).  It may issue DAO and DIS messages though it generally
   ignores DAO and DIS messages.

   In storing mode is suitable the use of RFC 6553 to send RPL
   Information through HBH field checking the routing table to find out
   where to send the message.

   In this case the flow comprises:

   RPL-aware-leaf

   not-RPL-aware-leaf (6LN) --> 6LR --> 6LR,... --> root (6LBR) Note: In
   this document 6LRs, 6LBR are always full-fledge RPL routers

   The 6LN inserts the RPI header, and send

   When the packet arrives from IPv6 node to 6LR which
   decrement 6LR, the rank in 6LR will insert an
   RPI and send the packet up.  When header, encapsuladed in a IPv6-in-IPv6 header.  The IPv6-in-IPv6
   header can be addressed to the packet
   arrives next hop, or to 6LBR, the RPI is removed root.  The root
   removes the header and process the packet is processed.

                 +-------------------+-----+------+------+ packet.

           +-------------------+------+------------+-----------+
           | Header            | 6LN IPv6 | 6LR        | 6LBR      |
                 +-------------------+-----+------+------+
           +-------------------+------+------------+-----------+
           | Inserted headers  | RPI | --   | IPIP(RPI)  | --        |
           | Removed headers   | --   | --         | RPI IPIP(RPI) |
           | Re-added headers  | --   | --         | --        |
           | Modified headers  | --   | RPI --         | --        |
           | Untouched headers | --   | --         | --        |
                 +-------------------+-----+------+------+
           +-------------------+------+------------+-----------+

     Storing: Summary of the use of headers from RPL-aware-leaf not-RPL-aware-leaf to
                                   root

5.2.

5.5.  Example of Flow from root to RPL-aware-leaf

   In this case to Internet

   RPL information from RFC 6553 should not go out to Internet as it
   will cause the flow comprises:

   root (6LBR)--> 6LR --> RPL-aware-leaf (6LN)

   In this case packet to be discarded at the first non-RPI aware
   router.  The 6LBR insert RPI header and send must be able to take this information out before
   sending the packet down, the
   6LR is going upwards to increment the rank in RPI (examines instanceID for
   multiple tables), Internet.  This requires the packet is processed 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

   The 6LN and will insert the RPI removed.

                +-------------------+------+-------+------+ 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            | 6LBR 6LN       | 6LR  | 6LN 6LBR      |
                +-------------------+------+-------+------+ Internet |
      +-------------------+-----------+------+-----------+----------+
      | Inserted headers  | RPI IPIP(RPI) | --   | --        | --       |
      | Removed headers   | --        | --   | RPI IPIP(RPI) | --       |
      | Re-added headers  | --        | --   | --        | --       |
      | Modified headers  | --        | RPI  | --        | --       |
      | Untouched headers | --        | --   | --        |
                +-------------------+------+-------+------+ --       |
      +-------------------+-----------+------+-----------+----------+

       Storing: Summary of the use of headers from root to RPL-aware-leaf

5.3. to
                                 Internet

5.6.  Example of Flow from root Internet to not-RPL-aware-leaf RPL-aware-leaf

   In this case the flow comprises:

   Internet --> root (6LBR)--> (6LBR) --> 6LR --> not-RPL-aware-leaf RPL-aware-leaf (6LN)

   It includes IPv6-in-IPv6 encapsulation to transmit information not
   related with the RPL domain.  In
   When the packet arrives from Internet to 6LBR the RPI header is inserted
   into an added
   in a outer IPv6-in-IPv6 header addressed and send to the last 6LR, which removes modifies the header before pass
   rank in the RPI.  When the packet to arrives 6LN the IPv6 node.

   +-------------------+-------------------+-------------------+------+ RPI header is
   removed and the packet processed.

     +-------------------+----------+------------+------+------------+
     | Header            | Internet | 6LBR       | 6LR  | IPv6 6LN        |
   +-------------------+-------------------+-------------------+------+
     +-------------------+----------+------------+------+------------+
     | Inserted headers  | IPv6-in-IPv6(RPI) --       | IPIP(RPI)  | --   | --         |
     | Removed headers   | --       | IPv6-in-IPv6(RPI) --         | --   | IPIP(RPI)  |
     | Re-added headers  | --       | --         | --   | --         |
     | Modified headers  | --       | --         | RPI  | --         |
     | Untouched headers | --       | --         | --   |
   +-------------------+-------------------+-------------------+------+ --         |
     +-------------------+----------+------------+------+------------+

    Storing: Summary of the use of headers from root Internet to not-RPL-aware- RPL-aware-
                                   leaf

5.4.

5.7.  Example of Flow from not-RPL-aware-leaf to root Internet

   In this case the flow comprises:

   not-RPL-aware-leaf (6LN) --> 6LR --> root (6LBR)

   When the packet arrives from IPv6 --> Internet

   The 6LR node to 6LR.  This router insert
   the RPI encapsuladed in a IPv6-in-IPv6 will add an IPIP(RPI) header addressed either to the root.
   The
   root, or hop-by-hop such that the root removes 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 process the packet

   +-------------------+------+--------------------+-------------------+ 6LBR
   will set the flow label to a non-zero value when sending to the
   Internet.

     +-------------------+------+------------+------------+----------+
     | Header            | IPv6 6LN  | 6LR        | 6LBR       |
   +-------------------+------+--------------------+-------------------+ Internet |
     +-------------------+------+------------+------------+----------+
     | Inserted headers  | --   | IPv6-in-IPv6(RPI) IPIP(RPI)  | --         | --       |
     | Removed headers   | --   | --         | IPv6-in-IPv6(RPI) 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.
                                 Internet

5.8.  Example of Flow from RPL-aware-leaf to Internet

   RPL information from RFC 6553 should not go out to Internet.  The
   router should take this information out before send the packet to
   Internet.  The HBH Option is going to be analyzed in each node to the
   root. non-RPL-aware-leaf

   In this case the flow comprises:

   RPL-aware-leaf (6LN) --> 6LR

   Internet --> root (6LBR) --> Internet

   6LN insert 6LR --> not-RPL-aware-leaf (6LN)

   The 6LBR will have to add an RPI in a IPv6-in-IPv6 in a outer header, and send the
   packet header within an IPIP header.  The
   IPIP will need to 6LR, which modified be addressed hop-by-hop along the rank path as in
   storing mode, the RPI.  When 6LBR has no idea if the packet
   arrives 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 6LBR, zero in
   order to aid in compression, as the RPI is removed.

   +----------+-------------------+-----+-------------------+----------+ packet will not emerge again from
   the LLN.

     +-------------------+----------+------------+------------+------+
     | Header            | 6LN               | 6LR Internet | 6LBR       | Internet 6LR        | IPv6 |
   +----------+-------------------+-----+-------------------+----------+
     +-------------------+----------+------------+------------+------+
     | Inserted | IPv6-in-IPv6(RPI) headers  | --       | -- IPIP(RPI)  | --         |
   | headers  |                   |     |                   | --   |
     | Removed headers   | --       | --         | IPv6-in-IPv6(RPI) IPIP(RPI)  | --   |
     | headers  |                   |     |                   |          |
   | Re-added headers  | --       | --         | --         | --   |
     | headers  |                   |     |                   |          |
   | Modified headers  | --       | RPI --         | --         | --   |
     | Untouched headers |                   |     |                   |          |
   | Untouche | --       | --         | --         | --   |
   | d        |                   |     |                   |          |
   | headers  |                   |     |                   |          |
   +----------+-------------------+-----+-------------------+----------+
     +-------------------+----------+------------+------------+------+

     Storing: Summary of the use of headers from RPL-aware-leaf to Internet

5.6. to non-RPL-
                                aware-leaf

5.9.  Example of Flow from Internet 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:

   Internet

   6LN --> root (6LBR) 6LR --> common parent (6LR) --> 6LR --> RPL-aware-leaf (6LN)

   When 6LN

   This case is assumed in the packet arrives from Internet to 6LBR same RPL Domain.  In the common parent,
   the direction of RPI header is added
   in a outer IPv6-in-IPv6 header and send changed (from increasing to 6LR, which modifies decreasing the
   rank in
   rank).

   While the RPI.  When 6LR nodes will update the packet arrives 6LN 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
   removed and RPL capable is not currently
   discernible by the packet processed.

   +----------+----------+-------------------+-----+-------------------+ sender.  This information is necessary to
   distinguish this test case from Section 5.10.

   +-------------+-------+---------------+---------------+-----+-------+
   | Header      | Internet 6LN   | 6LBR 6LR           | 6LR (common   | 6LR | 6LN   |
   +----------+----------+-------------------+-----+-------------------+
   |             | src   |               | parent)       |     | dst   |
   +-------------+-------+---------------+---------------+-----+-------+
   | Inserted    | RPI   | --            | IPv6-in-IPv6(RPI) --            | --  | --    |
   | headers     |       |               |               |     |       |
   | Removed     | --    | --            | --            | IPv6-in-IPv6(RPI) --  | RPI   |
   | headers     |       |               |               |     |       |
   | Re-added    | --    | --            | --            | --  | --    |
   | headers     |       |               |               |     |       |
   | Modified    | --    | -- RPI           | RPI           | --  | --    |
   | headers     |       | (decreasing   | (increasing   |     |       | Untouche
   | --             | --       | -- rank)         | rank)         | --     |       | d
   | Untouched   | --    | --            | --            | --  | --    |
   | headers     |       |               |               |     |
   +----------+----------+-------------------+-----+-------------------+       |
   +-------------+-------+---------------+---------------+-----+-------+

     Storing: Summary of the use of headers from Internet for RPL-aware-leaf to RPL-aware-
                                   leaf

5.7. RPL-
                                aware-leaf

5.10.  Example of Flow from not-RPL-aware-leaf RPL-aware-leaf to Internet non-RPL-aware-leaf

   In this case the flow comprises:

   not-RPL-aware-leaf (6LN) = IPv6 node

   6LN --> 6LR --> root (6LBR) common parent (6LR) -->
   Internet

   In the IPv6 node 6LR --> not-RPL-aware 6LN

   The sender, being aware out of band, that the flow label receiver is assumed not RPL
   aware, sends adds an RPI header inside an IPIP header.  The IPIP
   header needs to be zero, addressed on a hop-by-hop basis so that the packet is
   transmited to last
   6LR which encapsule can remove the RPI header in an outer IPv6-in-
   IPv6 header and send to 6LBR, which removes this header and send header.

                                ,---.
                               /     \
                              (  6LR2 ) IP3,RPI,IP,ULP
                             ,-"      .
                          ,-"   `---'  `.
                        ,'               `.
              ,---.  ,-"                   `,---.
             /     +"                      /     \
            ( 6LR1  )   Remove the
   packet to Internet and might set 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 flow label field.

   +----------+-----+-------------------+-------------------+----------+ 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.

   +-----------+-----------+-----------+------------+-----------+------+
   | Header    | IPv 6LN       | 6LR       | 6LBR 6LR        | Internet 6LR       | IPv6 |
   |           |           |           | (common    |           |      | 6
   |           |           |           |
   +----------+-----+-------------------+-------------------+----------+ parent)    |           |      |
   +-----------+-----------+-----------+------------+-----------+------+
   | Inserted  | IPIP(RPI) | --        | IPv6-in-IPv6(RPI) --         | --        | --   |
   | headers   |           |           |            |           |      |
   | Removed   | --        | --        | IPv6-in-IPv6(RPI) --         | IPIP(RPI) | --   |
   | headers   |           |           |            |           |      |
   | Re-added  | --        | --        | --         | --        | --   |
   | headers   |           |           |            |           |      |
   | Modified  | --        | -- IPIP(RPI) | IPIP(RPI)  | --        | --   |
   | headers   |           |           |            |           |      | Untouche
   | -- Untouched | --        | --        | --         | --        | d        |     |                   |                   | --   |
   | headers   |           |           |            |           |
   +----------+-----+-------------------+-------------------+----------+      |
   +-----------+-----------+-----------+------------+-----------+------+

    Storing: Summary of the use of headers from not-RPL-aware-leaf RPL-aware-leaf to
                                 Internet

5.8. not-
                              RPL-aware-leaf

5.11.  Example of Flow from Internet not-RPL-aware-leaf to non-RPL-aware-leaf RPL-aware-leaf

   In this case the flow comprises:

   Internet

   not-RPL-aware 6LN --> root (6LBR) 6LR --> common parent (6LR) --> 6LR --> not-RPL-aware-leaf (6LN)

   6LBR get 6LN

   The 6LR receives the packet from Internet the the IPv6 node and add a inserts and
   the RPI header encapsulated in a IPv6-in-IPv6 header.  The IPIP header addressed
   could be addresses to 6LR and send the packet down.
   The flow label 6LN if the destination is set known to zero on inner IP.  The last 6LR removes the
   RPI header.  The IPv6 node might set RPL
   aware, otherwise must send the flow label since may arrive
   with zero value.  The RPI should be in IP-in-IP packet using a hop-by-hop IPIP header.

   +----------+---------+-------------------+-------------------+------+
   Similar considerations apply from section Section 5.10.

   +-----------+------+-----------+------------+-----------+-----------+
   | Header    | Interne IPv6 | 6LBR 6LR       | common     | 6LR       | IPv6 6LN       |
   |           |      |           | parent     |           |           |
   | t           |      |           | (6LR)      |           |
   +----------+---------+-------------------+-------------------+------+           |
   +-----------+------+-----------+------------+-----------+-----------+
   | Inserted  | --   | IPv6-in-IPv6(RPI) IPIP(RPI) | --         | --        | --        |
   | headers   |      |           |            |           |           |
   | Removed   | --   | --        | IPv6-in-IPv6(RPI) --         | --        | IPIP(RPI) |
   | headers   |      |           |            |           |           |
   | Re-added  | --   | --        | --         | --        | --        |
   | headers   |      |           |            |           |           |
   | Modified  | --   | --        | -- IPIP(RPI)  | IPIP(RPI) | --        |
   | headers   |      |           |            |           |           | Untouche
   | -- Untouched | --   | --        | --         | --        | d        |         |                   |                   | --        |
   | headers   |      |           |            |           |
   +----------+---------+-------------------+-------------------+------+           |
   +-----------+------+-----------+------------+-----------+-----------+

     Storing: Summary of the use of headers from Internet not-RPL-aware-leaf to non-RPL-
                                aware-leaf

5.9.
                              RPL-aware-leaf

5.12.  Example of Flow from RPL-aware-leaf to RPL-aware-leaf

   In [RFC6550] RPL allows a simple one-hop P2P optimization for both
   storing and non-storing networks.  A node may send a P2P packet
   destined to a one-hop neighbor directly not-RPL-aware-leaf to that node.  Section 9 in
   [RFC6550]. not-RPL-aware-leaf

   In this case the flow comprises:

   not-RPL-aware 6LN --> (IPv6 node)--> 6LR --> common parent (6LR) root (6LBR) --> 6LR --> not-
   RPL-aware 6LN (IPv6 node)

   This case is assumed in the same RPL Domain.  In the common parent, flow combines the direction problems of RPI the two previous sections.  There
   is changed (from increasing to decreasing no choice at the
   rank).

   +-------------+-------+---------------+---------------+-----+-------+ 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.

   +-------------+--------+-----------+-----------+-----------+--------+
   | Header      | 6LN IPv6   | 6LR       | 6LR (common       | 6LR       | 6LN IPv6   |
   |             | src    |           | parent) (common   |           | dst    |
   +-------------+-------+---------------+---------------+-----+-------+
   | Inserted             | RPI        |           | parent)   |           |        |
   +-------------+--------+-----------+-----------+-----------+--------+
   | Inserted    | --     | IPIP(RPI) | --        | --        | --     |
   | headers     |        |           |           |           |        |
   | Removed     | --     | --        | --        | -- IPIP(RPI) | 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 not-RPL-aware-leaf to non-RPL-aware-leaf

   In this case the flow comprises:

   6LN --> 6LR --> common parent (6LR) --> 6LR --> not-RPL-aware 6LN

   Somehow, the sender has
                            not-RPL-aware-leaf

6.  Non Storing mode

          +------------------+------+------+-------+-----------+
          | Use Case         | RPI  | RH3  | IPIP  | IPIP dst  |
          +------------------+------+------+-------+-----------+
          | Raf to know that the receiver is not RPL aware,
   and needs to know 6LR, and not even the root knows where the 6LR is
   (in storing mode).

   This case FAILS.

   Possible solutions, which are not mutually exclusive:

   1 - An IPv6-in-IPv6 header can be used on a hop-by-hop basis, using
   either link-local addresses, or even IPv6 Global Unicast Addresses,
   but each IPv6-in-IPv6 header needs to be added/removed at each hop.

                                ,---.
                               /     \
                              (  6LR2 ) IP3,RPI,IP,ULP
                             ,-"      .
                          ,-"   `---'  `.
                        ,'               `.
              ,---.  ,-"                   `,---.
             /     +"                      /     \
            ( 6LR1  )   Remove the IP3,RPI(  6LR3 )
             \     /                       \     /
              /---'                         `---'|
             /    IP2,RPI,IP,ULP                 \
            /                                     |
           /                                      \
      ,---+-.                                      |
     /       \                                  +--+----+
    (  6LN    )      | Yes  |
     \       / No   |  IPv6 No    |  IP,ULP
      `-----' --        |
          |
           IP1,RPI,IP,ULP                       +-------+

                Figure 4: Solution IPv6-in-IPv6 in each hop

   2- If the definition of the Option Type field of RPL Option '01' were
   changed so that it isn't a "discard if not recognized".  This change
   is an incompatible on-the-wire change.  However, this change could
   perhaps be done with the updated 6LoRH compression work, as that is
   also an incompatible on-the-wire change for which we presently have
   no way root to signal.

   +-------+------------+------------+-------------+-------------+-----+
   | Heade | 6LN        | 6LR        | 6LR (common | 6LR         | IPv |
   | r     | Raf      | Yes  | parent) Yes  | No    | 6 --        |
   +-------+------------+------------+-------------+-------------+-----+
          | Inser root to ~Raf     | IPv6-in- No   | -- Yes  | -- Yes   | --        | --
          | ~Raf to root     | ted h Yes  | IPv6(RPI) No   | Yes   | root      |
          | Raf to Internet  | Yes  | eader No   | Yes   | root      |
          | Internet to Raf  | opt  | Yes  | s Yes   | dst       |
          | ~Raf to Internet | Yes  | No   | Yes   | Remov root      | --
          | -- Internet to ~Raf | -- opt  | IPv6-in- Yes  | -- Yes   | 6LR       | ed he
          | Raf to Raf       | Yes  | Yes  | IPv6(RPI) Yes   | root/dst  |
          | aders Raf to ~Raf      | Yes  | Yes  | Yes   | root/6LN  |
          | ~Raf to Raf      | Re- Yes  | -- Yes  | -- Yes   | -- root/6LN  | --          | --  |
   | added |            |            |             |             |     |
   | heade
          | ~Raf to ~Raf     | Yes  | Yes  | Yes   | root/6LN  |
          +------------------+------+------+-------+-----------+

      Table 2: Headers needed in Non-Storing mode: RPI, RH3, IP-in-IP
                               encapsulation

6.1.  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 to avoid/detect
   loops.

   RPL-aware-leaf (6LN) --> 6LR --> root (6LBR)

   This situation is the same case as storing mode.

                 +-------------------+-----+-----+------+
                 | rs Header            | 6LN | 6LR | 6LBR |
                 +-------------------+-----+-----+------+
                 | Inserted headers  | RPI | Modif --  | --   | IPv6-in-
                 | IPv6-in- Removed headers   | --  | --  |
   | ied h |            | IPv6(RPI)  | IPv6(RPI)   |             |     |
   | eader |            |            |             |             |     |
   | s     |            | RPI  |
                 | Re-added headers  | --  | --  | Untou RPI  | --
                 | -- Modified headers  | --  | --  | --   |
                 | ched  |            |            |             |             |     |
   | heade |            |            |             |             |     |
   | rs    |            | Untouched headers | --  | --  | --   |
   +-------+------------+------------+-------------+-------------+-----+
                 +-------------------+-----+-----+------+

     Non Storing: Summary of the use of headers from RPL-aware-leaf to not-
                              RPL-aware-leaf

5.11.
                                   root

6.2.  Example of Flow from not-RPL-aware-leaf root to RPL-aware-leaf

   In this case the flow comprises:

   not-RPL-aware 6LN --> 6LR --> common parent (6LR) -->

   root (6LBR)--> 6LR --> 6LN RPL-aware-leaf (6LN)

   The 6LR that get the packet from IPv6 node, 6LBR will insert the an RH3, and may optionally insert an RPI header.
   No IPIP header
   encapsulated in IPv6-in-IPv6 header with destination to 6LN, the
   common parent change the direction of RPI and finally it is removed
   by 6LN.

   +-------+----+------------+-------------+-------------+-------------+
   | Heade | IP necessary as the traffic originates with an RPL
   aware node.

         +-------------------+-----------------+------+----------+
         | 6LR Header            | common 6LBR            | 6LR  | 6LN      |
         +-------------------+-----------------+------+----------+
         | r     | v6 |            | parent      |             |             |
   |       |    |            | (6LR)       |             | Inserted headers  |
   +-------+----+------------+-------------+-------------+-------------+ (opt: RPI), RH3 | Inser --   | --       | IPv6-in-
         | -- Removed headers   | --              | --   |
   | ted h |    | IPv6(RPI)  |             |             |             |
   | eader |    |            | RH3,RPI  |
         | Re-added headers  | --              | s --   | --       |
         | Modified headers  | --              | RH3  | --       | Remov
         | -- Untouched headers | --              | --   | --       | IPv6-in-    |
   | ed he |    |            |             |             | IPv6(RPI)   |
   | aders
         +-------------------+-----------------+------+----------+

    Non Storing: Summary of the use of headers from root to RPL-aware-
                                   leaf

6.3.  Example of Flow from root to not-RPL-aware-leaf

   In this case the flow comprises:

   root (6LBR)--> 6LR --> not-RPL-aware-leaf (IPv6 node)

   In 6LBR the RH3 is added, and modified in 6LR where it is fully
   consumed, but left there.  If the RPI is left present, the IPv6 node
   which does not understand it will drop it, therefore the RPI should
   be removed before reaching the IPv6-only node.  To permit removal, an
   IPIP header (hop-by-hop) or addressed to the last 6LR is necessary.
   Due the complete knowledge of the topology at the root, the 6LBR is
   able to address the IPIP header to the last 6LR.

   Omitting the RPI entirely is therefore a better solution, as no IPIP
   header is necessary.

                 +-------------------+------+-----+------+
                 | Header            | 6LBR | 6LR | IPv6 |
                 +-------------------+------+-----+------+
                 | Inserted headers  | Re- RH3  | --  | --   | --
                 | -- Removed headers   | --   | --  | added |    |            |             |             |             |
   | heade |    | --   |
                 | Re-added headers  | --   | --  | rs --   |
                 | Modified headers  | --   | RH3 | --   |
                 | Modif Untouched headers | --   | --  | IPv6-in-    | IPv6-in-    | --   |
                 +-------------------+------+-----+------+

     Non Storing: Summary of the use of headers from root to not-RPL-
                                aware-leaf

6.4.  Example of Flow from not-RPL-aware-leaf to root

   In this case the flow comprises:

   IPv6-node --> 6LR1 --> 6LR2 --> root (6LBR)

   In this case the RPI is added by the first 6LR, encapsulated in an
   IPIP header, and is not modified in the followings 6LRs.  The RPI and
   entire packet is consumed by the root.

       +-------------------+------+------------+------+------------+
       | ied h | Header            | IPv6 | IPv6(RPI) 6LR1       | IPv6(RPI) 6LR2 | 6LBR       |
       +-------------------+------+------------+------+------------+
       | eader Inserted headers  | --   | IPIP(RPI)  | --   | --         |
       | Removed headers   | s --   | --         | --   | IPIP(RPI)  |
       | Re-added headers  | --   | Untou --         | --   | --         |
       | Modified headers  | --   | --         | --   | --         | ched
       | Untouched headers | --   | IPIP(RPI)  | --   | --         |
   | heade |    |            |             |             |             |
   | rs    |    |            |             |             |             |
   +-------+----+------------+-------------+-------------+-------------+
       +-------------------+------+------------+------+------------+

   Non Storing: Summary of the use of headers from not-RPL-aware-leaf to
                              RPL-aware-leaf

5.12.
                                   root

6.5.  Example of Flow from not-RPL-aware-leaf RPL-aware-leaf to not-RPL-aware-leaf Internet

   In this case the flow comprises:

   not-RPL-aware 6LN (IPv6 node)-->

   RPL-aware-leaf (6LN) --> 6LR --> root (6LBR) --> 6LR --> not-
   RPL-aware 6LN (IPv6 node)

   The problem to solve is how to indicate where to send the packet when
   get into LLN.  One approach is Internet

   This case requires that the 6LBR should know in which 6LR RPI be added, but remoted by the IPv6 node is attached. 6LBR.
   The 6LN must therefore add the RPI information is encapsulated in a
   IPv6-in-IPv6 inside an IPIP header, each IPv6-in-IPv6 header needs addressed
   to the root.  This case is identical to storing-mode case.

   The IPv6 flow label should be added/
   removed at each hop..

   +---------+-----+----------------+---------+-----------------+------+ set to zero to aid in compression, and
   the 6LBR will set it to a non-zero value when sending towards the
   Internet.

     +-------------------+-----------+------+------------+----------+
     | Header            | IPv 6LN       | 6LR  | 6LR 6LBR       | 6LR Internet | IPv6
     +-------------------+-----------+------+------------+----------+
     | Inserted headers  | IPIP(RPI) | 6 --   | --         | (common --       |
     | dst Removed headers   | --        | --   | src IPIP(RPI)  | --       | parent)
     | Re-added headers  | --        |
   +---------+-----+----------------+---------+-----------------+------+ --   | Inserte --         | --       | IPv6-in-
     | -- Modified headers  | --        | --   | --         | d --       |
     | IPv6(RPI) Untouched headers | --        | RPI  | --         | --       |
     +-------------------+-----------+------+------------+----------+

     Non Storing: Summary of the use of headers from RPL-aware-leaf to
                                 Internet

6.6.  Example of Flow from Internet to RPL-aware-leaf

   In this case the flow comprises:

   Internet --> root (6LBR) --> 6LR --> RPL-aware-leaf (6LN)

   The 6LBR must add an RH3 header.  As the 6LBR will know the path and
   address of the target not, it can address the IPIP header to that
   node.  The 6LBR will zero the flow label upon entry in order to aid
   compression.

   The RPI may be added or not.

   +----------------+----------+--------------------+------------+-----+
   | Header         | Internet | 6LBR               | 6LR        | 6LN |
   +----------------+----------+--------------------+------------+-----+
   | Removed Inserted       | --       | -- IPIP(RH3,opt:RPI)  | --         | IPv6-in-        | --  |
   | headers        |          |                    |            | IPv6(RPI)       |     |
   | Re- Removed        | --       | --                 | -- IPIP(RH3)  | --  | --
   | headers        | added          |                    |            |     |
   | Re-added       | --       | headers --                 | --         | --  |
   | headers        |          |                    | Modifie            | --     | --
   | -- Modified       | --       | --                 | IPIP(RH3)  | d       |     |                |         |                 | --  |
   | headers        |          |                    |            |     |
   |
   | Untouch | -- Untouched      | --       | --                 | --         | --  |
   | ed      |     |                |         |                 |      |
   | headers        |          |                    |            |     |      |
   +---------+-----+----------------+---------+-----------------+------+
   +----------------+----------+--------------------+------------+-----+

     Non Storing: Summary of the use of headers from not-RPL-aware-leaf Internet to
                            not-RPL-aware-leaf

6.  Non Storing mode

6.1. RPL-
                                aware-leaf

6.7.  Example of Flow from RPL-aware-leaf to root

   In non-storing mode the leaf node uses Hop-By-Hop option (RFC 6553)
   to indicate the routing information to send messages to the DODAG
   root, this message is going not-RPL-aware-leaf to be analyzed in each node until arrive
   the DODAG root. Internet

   In this case not need to use IPv6-in-IPv6 because no header is not
   going to be removed, neither RH3, the flow comprises:

   RPL-aware-leaf

   not-RPL-aware-leaf (6LN) --> 6LR --> root (6LBR)

   This --> Internet

   In this case the flow label is recommended to be zero in the same IPv6
   node.  As RPL headers are added in the IPv6 node, the first 6LN will
   add an RPI header inside a new IPIP header.  The IPIP header will be
   addressed to the root.  This case as storing mode.

                 +-------------------+-----+------+------+ is identical to the storing-mode
   case.

     +-------------------+------+-----------+------------+----------+
     | Header            | 6LN IPv6 | 6LR       | 6LBR       |
                 +-------------------+-----+------+------+ Internet |
     +-------------------+------+-----------+------------+----------+
     | Inserted headers  | RPI --   | IPIP(RPI) | --         | --       |
     | Removed headers   | --   | --        | RPI IPIP(RPI)  | --       |
     | Re-added headers  | --   | --        | --         | --       |
     | Modified headers  | --   | RPI --        | --         | --       |
     | Untouched headers | --   | --        | --         |
                 +-------------------+-----+------+------+ --       |
     +-------------------+------+-----------+------------+----------+

   Non Storing: Summary of the use of headers from RPL-aware-leaf not-RPL-aware-leaf to
                                   root

6.2.
                                 Internet

6.8.  Example of Flow from root Internet to RPL-aware-leaf non-RPL-aware-leaf

   In this case the flow comprises:

   Internet --> root (6LBR)--> (6LBR) --> 6LR --> RPL-aware-leaf not-RPL-aware-leaf (6LN)
   The 6LBR might instert RPI header, must add an RH3 header inside an IPIP header.  The 6LBR will
   know the path, and will recognize that the rute final node is indicated not an RPL
   capable node as it will have received the connectivity DAO from the
   nearest 6LR.  The 6LBR can therefore make the IPIP header destination
   be the last 6LR.  The 6LBR will zero the flow label upon entry in RH3. 6LR
   updated RH3 and 6LN remove these headers.

      +-------------------+----------------------+------+----------+
   order to aid compression.

   +--------------+----------+-------------------+--------------+------+
   | Header       | Internet | 6LBR              | 6LR          | 6LN IPv6 |
      +-------------------+----------------------+------+----------+
   +--------------+----------+-------------------+--------------+------+
   | Inserted headers     | (optional: RPI), RH3 --       | IPIP(RH3,opt:RPI) | --           | --   |
   | Removed headers      |          |                   |              |      |
   | Removed      | --       | --                | RH3,RPI IPIP(RH3,    | --   |
   | Re-added headers      |          |                   | RPI)         |      |
   | Re-added     | --       | --                | --           | --   |
   | Modified headers      |          |                   |              |      |
   | Modified     | --       | RH3 --                | --           | --   |
   | Untouched headers      |          |                   |              |      |
   | Untouched    | --       | --                | --           |
      +-------------------+----------------------+------+----------+

    Non Storing: --   |
   | headers      |          |                   |              |      |
   +--------------+----------+-------------------+--------------+------+

    NonStoring: Summary of the use of headers from root Internet to RPL-aware-
                                   leaf

6.3. non-RPL-
                                aware-leaf

6.9.  Example of Flow from root RPL-aware-leaf to not-RPL-aware-leaf RPL-aware-leaf

   In this case the flow comprises:

   6LN --> 6LR --> root (6LBR)--> (6LBR) --> 6LR --> not-RPL-aware-leaf (IPv6 node)

   In 6LBR 6LN

   This case involves only nodes in same RPL Domain.  The originating
   node will add an RPI header to the RH3 is added, original packet, and modified in 6LR where is fully
   consumed, but left there.  If send the
   packet upwards.

   The originating node could put the RPI is present, into an IPIP header addressed
   to the IPv6 node which
   does not understand it root, so that the 6LBR can remove that header.

   The 6LBR will drop it.  To avoid need to insert an RH3 header, which requires that it
   add an IPIP header.  It may be able to remove the RPI should be
   removed before reach IPv6 node or if it is recommended that RPI was
   contained in an IPIP header addressed to it.  Otherwise, there may be
   omitted.  An IPv6-in-IPv6
   an RPI header buried inside the inner IP header, which should be necessary in this case.
   The DAO from 6LR about IPv6 could say if get
   ignored.

   Networks that use the final IPv6 is not RPL (RPI) capable.

                 +-------------------+------+-----+------+ P2P extension [RFC6997] are essentially
   non-storing DODAGs and fall into this scenario.

   +----------------+-----------+----------------+-----+---------------+
   | Header         | 6LN src   | 6LBR           | 6LR | IPv6 6LN dst       |
                 +-------------------+------+-----+------+
   +----------------+-----------+----------------+-----+---------------+
   | Inserted headers       | RH3 IPIP(RPI) | IPIP(RH3 to    | --  | --            |
   | Removed headers        | --           | -- 6LN,RPI)       | --     |               | Re-added headers
   | Removed        | --        | --             | --  | IPIP(RH3,RPI) |
   | Modified headers        | --           | RH3                | --     |               | Untouched headers
   | Re-added       | --        | --             | --  |
                 +-------------------+------+-----+------+

     Non Storing: Summary --            |
   | headers        |           |                |     |               |
   | Modified       | --        | --             | --  | --            |
   | headers        |           |                |     |               |
   | Untouched      | --        | --             | --  | --            |
   | headers        |           |                |     |               |
   +----------------+-----------+----------------+-----+---------------+

   Non Storing: Summary of the use of headers from root for RPL-aware-leaf to not-RPL- RPL-
                                aware-leaf

6.4.

6.10.  Example of Flow from not-RPL-aware-leaf RPL-aware-leaf to root not-RPL-aware-leaf

   In this case the flow comprises:

   IPv6-node --> 6LR1

   6LN --> 6LR2 6LR --> root (6LBR)

   In this case --> 6LR --> not-RPL-aware 6LN

   As in the previous case, the 6LN will insert an RPI is encapsulated header which MUST
   be in an IPIP header addressed to the first 6LR, and is not
   modified in root so that the followings 6LRs.

   +-------------+------+-------------------+------+-------------------+ 6LBR can
   remove this RPI.  The 6LBR will then insert an RH3 inside a new IPIP
   header addressed to the 6LN above the destination node.

   +---------------+-----------+---------------+----------------+------+
   | Header        | IPv6 6LN       | 6LR1 6LBR          | 6LR2 6LR            | 6LBR IPv6 |
   +-------------+------+-------------------+------+-------------------+
   +---------------+-----------+---------------+----------------+------+
   | Inserted      | -- IPIP(RPI) | IPv6-in-IPv6(RPI) IPIP(RH3, opt | --             | --   |
   | headers       |           | RPI)          |                |      |
   | Removed       | --        | -- IPIP(RPI)     | -- IPIP(RH3, opt  | IPv6-in-IPv6(RPI) --   |
   | headers       |           |               | RPI)           |      |
   | Re-added      | --        | --            | --             | --   |
   | headers       |           |               |                |      |
   | Modified      | --        | --            | --             | --   |
   | headers       |           |               |                |      |
   | Untouched     | --        | IPv6-in-IPv6(RPI) --            | --             | --   |
   | headers       |           |               |                |      |
   +-------------+------+-------------------+------+-------------------+
   +---------------+-----------+---------------+----------------+------+

     Non Storing: Summary of the use of headers from not-RPL-aware-leaf RPL-aware-leaf to
                                   root

6.5.
                            not-RPL-aware-leaf

6.11.  Example of Flow from RPL-aware-leaf not-RPL-aware-leaf to Internet RPL-aware-leaf

   In this case the flow comprises:

   RPL-aware-leaf (6LN)

   not-RPL-aware 6LN --> 6LR --> root (6LBR) --> Internet 6LR --> 6LN

   This case requires that the network is awareness of what scenario is external mostly identical to the LLN.  Internet node never sees previous one.  The RPI or IPv6-in-IPv6 header.  In is
   added by the 6LBR first 6LR inside an IPIP header addressed to the flow label is computed if it is zero.  RPI remains
   unmodified.

   +----------+-------------------+-----+-------------------+----------+ root.
   The 6LBR will remove this RPI, and add it's own IPIP header
   containing an RH3 header.

    +-------------------+------+------------+-----------+------------+
    | Header            | 6LN IPv6 | 6LR        | 6LBR      | Internet 6LN        |
   +----------+-------------------+-----+-------------------+----------+
    +-------------------+------+------------+-----------+------------+
    | Inserted | IPV6-in-IPv6(RPI) headers  | --   | -- IPIP(RPI)  | IPIP(RH3) | --         |
    | Removed headers   | --   | IPIP(RPI)  | --        | IPIP(RH3)  |
    | Removed Re-added headers  | --   | --         | IPV6-in-IPv6(RPI) --        | --         |
    | Modified headers  |                   |     |                   |          |
   | Re-added | --   | --         | --        | --         |
    | Untouched headers |                   |     |                   |          |
   | Modified | --   | --         | --        | --         |
   | headers  |                   |     |                   |          |
   | Untouche | --                | RPI | --                | --       |
   | d        |                   |     |                   |          |
   | headers  |                   |     |                   |          |
   +----------+-------------------+-----+-------------------+----------+
    +-------------------+------+------------+-----------+------------+

   Non Storing: Summary of the use of headers from RPL-aware-leaf not-RPL-aware-leaf to
                                 Internet

6.6.
                              RPL-aware-leaf

6.12.  Example of Flow from Internet not-RPL-aware-leaf to RPL-aware-leaf not-RPL-aware-leaf

   In this case the flow comprises:

   Internet

   not-RPL-aware 6LN --> 6LR --> root (6LBR) --> 6LR --> RPL-aware-leaf (6LN)

   If the last RH3 entry is the 6LR, then the IPv6-in-IPv6 will be
   removed there, if the last entry not-RPL-aware
   6LN

   This scenario is the 6LN, then the RH3 will go all
   the way to the leaf.  In 6LBR combination of the flow label should be set to zero.

   +---------+--------+-------------------------+----------------+-----+ previous two cases.

   +--------------+------+-----------+-----------+--------------+------+
   | Header       | Intern | 6LBR IPv6 | 6LR       | 6LN |
   |         | et     | 6LBR      | 6LR          | IPv6 |
   +---------+--------+-------------------------+----------------+-----+
   +--------------+------+-----------+-----------+--------------+------+
   | Inserte Inserted     | --   | IPv6-in- IPIP(RPI) | -- IPIP(RH3) | --           |
   | d       |        | IPv6(RH3,optional:RPI)  |                | --   |
   | headers      |      |           |           |              |      |
   | Removed      | --   | --        | IPv6-in-IPv6 IPIP(RPI) | IPIP(RH3,    | --   |
   | headers      |      |           | can be removed |     |
   |         |        |                         | if RH3         |     |
   |           |        |                         | consumed opt RPI)     |      |
   | Re- Re-added     | --   | --        | --        | --           |
   | added   |        |                         |                | --   |
   | headers      |      |           |           |              |      | Modifie
   | -- Modified     | --   | IPv6-in-       | --        | --        | d       |        |                         | IPv6(RH3) --           | --   |
   | headers      |      |           |           |              |      | Untouch
   | -- Untouched    | --   | --        | --        | --           | ed      |        |                         |                | --   |
   | headers      |      |           |           |              |
   +---------+--------+-------------------------+----------------+-----+      |
   +--------------+------+-----------+-----------+--------------+------+

   Non Storing: Summary of the use of headers from Internet to RPL-
                                aware-leaf

6.7.  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

   In this case the flow label is recommended to be zero in

7.  Observations about the IPv6
   node. no RPL headers are added in problem

7.1.  Storing mode

   In the IPv6 node, since completely general storing case, which includes not-RPL aware
   leaf nodes, it is ignorant
   of RPL.  Internet node does not see special headers.  In 6LBR possible for a sending node to know if the
   flow label
   destination is computed if RPL aware, and therefore it is zero.

   +----------+-----+-------------------+-------------------+----------+
   | Header   | IPv | 6LR               | 6LBR              | Internet |
   |          | 6   |                   |                   |          |
   +----------+-----+-------------------+-------------------+----------+
   | Inserted | --  | IPv6-in-IPv6(RPI) | --                | --       |
   | headers  |     |                   |                   |          |
   | Removed  | --  | --                | IPv6-in-IPv6(RPI) | --       |
   | headers  |     |                   |                   |          |
   | Re-added | --  | --                | --                | --       |
   | headers  |     |                   |                   |          |
   | Modified | --  | --                | --                | --       |
   | headers  |     |                   |                   |          |
   | Untouche | --  | --                | --                | --       |
   | d        |     |                   |                   |          |
   | headers  |     |                   |                   |          |
   +----------+-----+-------------------+-------------------+----------+

   Non Storing: Summary of the use of headers from not-RPL-aware-leaf to
                                 Internet

6.8.  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)

   In this case the flow label in 6LBR should be set zero in 6LBR, where
   RH3 is inserted and optionally RHI.  RH3 must end at 6LR.

   In Non-Storing mode, root knows that the non-RPL-aware-leaf is
   attached to the parent 6LR, and builds RH3 with IPv6-in-IPv6 with
   this 6LR as destination.

   +---------+--------+-------------------------+---------------+------+
   | Header  | Intern | 6LBR                    | 6LR           | IPv6 |
   |         | et     |                         |               |      |
   +---------+--------+-------------------------+---------------+------+
   | Inserte | --     | IPv6-in-                | --            | --   |
   | d       |        | IPv6(RH3,optional:RPI)  |               |      |
   | headers |        |                         |               |      |
   | Removed | --     | --                      | IPv6-in-      | --   |
   | headers |        |                         | IPv6(RH3,     |      |
   |         |        |                         | RPI)          |      |
   | Re-     | --     | --                      | --            | --   |
   | added   |        |                         |               |      |
   | headers |        |                         |               |      |
   | Modifie | --     | --                      | --            | --   |
   | d       |        |                         |               |      |
   | headers |        |                         |               |      |
   | Untouch | --     | --                      | --            | --   |
   | ed      |        |                         |               |      |
   | headers |        |                         |               |      |
   +---------+--------+-------------------------+---------------+------+

    NonStoring: Summary of the use of headers from Internet to non-RPL-
                                aware-leaf

6.9.  Example of Flow from RPL-aware-leaf to RPL-aware-leaf

   In this case the flow comprises:

   6LN --> 6LR --> root (6LBR) --> 6LR --> 6LN

   This case comprises in the same RPL Domain.  In the 6LN the RPI
   header is inserted.  In the 6LBR the RH3 header is inserted in a
   IPv6-in-IPv6 header and removed at the 6LN destination.

   In case of the flow goes from RPL-aware-Leaf to RPL-aware-Leaf, the
   RPI should be set in a IP-in-IP header, to avoid repetition of RPI
   header.

   +---------+---------------+---------------+-----+-------------------+
   | Header  | 6LN src       | 6LBR          | 6LR | 6LN dst           |
   +---------+---------------+---------------+-----+-------------------+
   | Inserte | IPv6-in-      | IPv6-in-      | --  | --                |
   | d       | IPv6(RPI)     | IPv6(RH3 to   |     |                   |
   | headers |               | 6LN,RPI)      |     |                   |
   |         |               | {IP,payload}  |     |                   |
   | Removed | --            | --            | --  | IPv6-in-          |
   | headers |               |               |     | IPv6(RH3,RPI)     |
   |         |               |               |     | {IP,RPI,payload}  |
   | Re-     | --            | --            | --  | --                |
   | added   |               |               |     |                   |
   | headers |               |               |     |                   |
   | Modifie | --            | --            | --  | --                |
   | d       |               |               |     |                   |
   | headers |               |               |     |                   |
   | Untouch | --            | --            | --  | --                |
   | ed      |               |               |     |                   |
   | headers |               |               |     |                   |
   +---------+---------------+---------------+-----+-------------------+

   Non Storing: Summary of the use of headers for RPL-aware-leaf to RPL-
                                aware-leaf

6.10.  Example of Flow from RPL-aware-leaf to not-RPL-aware-leaf

   In this case the flow comprises:

   6LN --> 6LR --> root (6LBR) --> 6LR --> not-RPL-aware 6LN

   The 6LN insert the RPI in a IPv6-in-IPv6 header, which is addressed
   to 6LBR.  The 6LBR remove this RPI header and insert a RH3 header
   with an optional RPI.  These headers are removed by 6LR before send
   the packet to the IPv6 node.

   +------------+-------------------+-------------+-------------+------+
   | Header     | 6LN               | 6LBR        | 6LR         | IPv6 |
   +------------+-------------------+-------------+-------------+------+
   | Inserted   | IPv6-in-IPv6(RPI) | IPIP(RH3,   | --          | --   |
   | headers    |                   | opt RPI)    |             |      |
   | Removed    | --                | IPIP(RPI)   | IPIP(RH3,   | --   |
   | headers    |                   |             | opt RPI)    |      |
   | Re-added   | --                | --          | --          | --   |
   | headers    |                   |             |             |      |
   | Modified   | --                | --          | --          | --   |
   | headers    |                   |             |             |      |
   | Untouched  | --                | --          | --          | --   |
   | headers    |                   |             |             |      |
   +------------+-------------------+-------------+-------------+------+

     Non Storing: Summary of the use of headers from RPL-aware-leaf to
                            not-RPL-aware-leaf

6.11.  Example of Flow from not-RPL-aware-leaf to RPL-aware-leaf

   In this case the flow comprises:

   not-RPL-aware 6LN --> 6LR --> root (6LBR) --> 6LR --> 6LN

   RPI is added in 6LR until the root and then removed, then RH3 is
   added and removed at destination.

    +-------------------+------+------------+-----------+------------+
    | Header            | IPv6 | 6LR        | 6LBR      | 6LN        |
    +-------------------+------+------------+-----------+------------+
    | Inserted headers  | --   | IPIP(RPI)  | IPIP(RH3) | --         |
    | Removed headers   | --   | IPIP(RPI)  | --        | IPIP(RH3)  |
    | Re-added headers  | --   | --         | --        | --         |
    | Modified headers  | --   | --         | --        | --         |
    | Untouched headers | --   | --         | --        | --         |
    +-------------------+------+------------+-----------+------------+

   Non Storing: Summary of the use of headers from not-RPL-aware-leaf to
                              RPL-aware-leaf

6.12.  Example of Flow from not-RPL-aware-leaf to not-RPL-aware-leaf

   In this case the flow comprises:

   not-RPL-aware 6LN --> 6LR --> root (6LBR) --> 6LR --> not-RPL-aware
   6LN
   RPI is added in 6LR until the root and then might be removed, then
   RH3 is added.  These headers are removed at 6LR before go to
   destination.

   +--------------+------+-----------+-----------+--------------+------+
   | Header       | IPv6 | 6LR       | 6LBR      | 6LR          | IPv6 |
   +--------------+------+-----------+-----------+--------------+------+
   | Inserted     | --   | IPIP(RPI) | IPIP(RH3) | --           | --   |
   | headers      |      |           |           |              |      |
   | Removed      | --   | --        | IPIP(RPI) | IPIP(RH3,    | --   |
   | headers      |      |           |           | opt RPI)     |      |
   | Re-added     | --   | --        | --        | --           | --   |
   | headers      |      |           |           |              |      |
   | Modified     | --   | --        | --        | --           | --   |
   | headers      |      |           |           |              |      |
   | Untouched    | --   | --        | --        | --           | --   |
   | headers      |      |           |           |              |      |
   +--------------+------+-----------+-----------+--------------+------+

   Non Storing: Summary of the must always use of headers from not-RPL-aware-leaf hop-by-hop
   IPIP encapsulation, and it can never omit the IPIP encapsulation.
   See table Table 1

   The simplest fully general stiaution for storing mode is to
                            not-RPL-aware-leaf

7.  Problem statement always
   put in hop-by-hop IPIP headers.  [I-D.ietf-roll-routing-dispatch]
   shows that this hop-by-hop IPIP header can be compressed down to
   {TBD} bytes.

   There are cases from above potential significant advantages to having a single code
   path that always processes IPIP headers with no options.

   If all RPL aware nodes can be told/configured that there are not clear how to send no non-
   RPL aware leaf nodes, then the
   information.  It requires furhter analysis on how to proceed to send only case where an IPIP header is
   needed is when communicating outside the information LLN.  The 6LBR knows well
   when the communication is from source the outside, and the 6LN can tell by
   comparing the destination address to destination.

   From the above cases, we have prefix provided in storing mode:

   - Flow from RPL-aware-leaf to non-RPL-aware-leaf: Somehow, the sender
   has to know PIO.
   If it is known that there are no communications outside the receiver is not RPL aware,
   domain (noting that the RPL domain may well extend to outside the
   LLN), then RPI headers can be included in all packets, and needs IPIP
   headers are *never* needed.  This may be significantly advantageous
   in relatively closed systems such as in building or industrial
   automation.  Again, there are advantages to know
   6LR, having a single code
   path.

   In order to support the above two cases with full generality, the
   different situations (always do IPIP vs never use IPIP) should be
   signaled in the RPL protocol itself.

7.2.  Non-Storing mode

   This 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 nodes, and not even all traffic flows through the root knows where
   node.

   The 6LBR can recognize non-RPL aware leaf nodes because it will
   receive a DAO about that node from the 6LR 6LN immediately above that
   node.  This means that the non-storing mode case can avoid ever using
   hop-by-hop IPIP headers.

   It is located.

   - Flow from not-RPL-aware-leaf unclear what it would mean for an RH3 header to not-RPL-aware-leaf: be present in a
   hop-by-hop IPIP header.  The problem to
   solve is how receiving node ought to indicate where consume the IPIP
   header, and therefore consume the RH3 as well, and then attempt to
   send the packet when get into LLN.
   One approach is again.  But intermediate 6LN nodes would not know how
   to forward the 6LBR should packet, so the RH3 would need to be aware in which 6LR retained.  This is the IPv6
   node attached.

   As was mentioned above in the document,
   a possible solution could new kind of IPv6 packet processing.  Therefore it may be
   adapted to all cases: An IPv6-in-IPv6 that on
   the outbound leg of non-storing RPL networks, that hop-by-hop IPIP
   header can NOT be used on a hop-by-
   hop basis, using either link-local addresses, or even IPv6 Global
   Unicast Addresses, but each IPv6-in-IPv6 used.

   [I-D.ietf-roll-routing-dispatch] shows how the destination=root, and
   destination=6LN IPIP header can be compressed down to {TBD} bytes.

   Unlike in the storing mode case, there are no need for all nodes to
   know about the existence of non-RPL aware nodes.  Only the 6LBR needs
   to be added/
   removed at each hop. change when there are non-RPL aware nodes.  Further, in the non-
   storing case, the 6LBR is informed by the DAOs when there are non-RPL
   aware nodes.

8.  6LoRH Compression cases

   The [I-D.ietf-6lo-routing-dispatch] [I-D.ietf-roll-routing-dispatch] proposes a compression method
   for RPI, RH3 and IPv6-in-IPv6.

   The uses cases mentioned in this draft MUST use 6LoRH.  Examples of

   In Storing Mode, for the use examples of 6LoRH are found in Apendix A Flow from RPL-aware-leaf to non-
   RPL-aware-leaf and non-RPL-aware-leaf to non-RPL-aware-leaf comprise
   an IP-in-IP and RPI compression headers.  The type of
   [I-D.ietf-6lo-routing-dispatch]. this case is
   critical since IP-in-IP is encapsulating a RPI header.

   +--+-----+---+--------------+-----------+-------------+-------------+
   |1 | 0|0 |TSE| 6LoRH Type 6 | Hop Limit | RPI - 6LoRH | LOWPAN IPHC |
   +--+-----+---+--------------+-----------+-------------+-------------+

                    Figure 5: Critical IP-in-IP (RPI).

9.  IANA Considerations

   There are no IANA considerations related to this document.

10.  Security Considerations

   The security considerations covering of [RFC6553] and [RFC6554] apply
   when the packets get into RPL Domain.

11.  Acknowledgments

   This work is partially funded by the FP7 Marie Curie Initial Training
   Network (ITN) METRICS project (grant agreement No.  607728).

   The authors would like to acknowledge the review, feedback, and
   comments of Thomas Watteyne, Xavier Vilajosana, Robert Cragie and
   Simon Duquennoy.

12.  References

12.1.  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,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

   [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,
              <http://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,
              <http://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,
              <http://www.rfc-editor.org/info/rfc6554>.

12.2.  Informative References

   [I-D.ietf-6lo-routing-dispatch]
              Thubert, P., Bormann, C., Toutain, L., and R. Cragie,
              "6LoWPAN Routing Header", draft-ietf-6lo-routing-
              dispatch-05 (work in progress), February 2016.

   [I-D.ietf-6tisch-architecture]
              Thubert, P., "An Architecture for IPv6 over the TSCH mode
              of IEEE 802.15.4", draft-ietf-6tisch-architecture-09 (work
              in progress), November 2015.

   [I-D.ietf-roll-routing-dispatch]
              Thubert, P., Bormann, C., Toutain, L., and R. Cragie,
              "6LoWPAN Routing Header", draft-ietf-roll-routing-
              dispatch-00 (work in progress), March 2016.

   [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,
              <http://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, <http://www.rfc-editor.org/info/rfc7102>.

   [Second6TischPlugtest]
              "2nd 6Tisch Plugtest", <http://www.ietf.org/mail-
              archive/web/6tisch/current/pdfgDMQcdCkRz.pdf>.

Authors' Addresses

   Maria Ines Robles
   Ericsson
   Hirsalantie 11
   Jorvas  02420
   Finland

   Email: maria.ines.robles@ericsson.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/

   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