wdiff draft-ietf-6lo-routing-dispatch-03.txt draft-ietf-6lo-routing-dispatch-04.txt

6lo P. Thubert, Ed.
Internet-Draft Cisco
Intended status: Standards Track C. Bormann
Expires: July 18, 26, 2016 Uni Bremen TZI
L. Toutain
IMT-TELECOM Bretagne
R. Cragie
ARM
January 15, 23, 2016

6LoWPAN Routing Header And Paging Dispatches
draft-ietf-6lo-routing-dispatch-03
draft-ietf-6lo-routing-dispatch-04

Abstract

This specification introduces a new 6LoWPAN dispatch type for use in
6LoWPAN Route-Over topologies, that initially covers the needs of RPL
(RFC6550) data packets compression. Using this dispatch type, this
specification defines a method to compress RPL Option (RFC6553)
information and Routing Header type 3 (RFC6554), an efficient IP-in-
IP technique and is extensible for more applications.

Status of This Memo

This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Drafts is at http://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
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This Internet-Draft will expire on July 18, 26, 2016.

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described in the Simplified BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 6
3. Using the Page Dispatch . . . . . . . . . . . . . . . . . . . 5 6
3.1. New Routing Header Dispatch (6LoRH) . . . . . . . . . . . 6
3.2. Placement Of The 6LoRH headers . . . . . . . . . . . . . . . 6
3.2.1. Relative To Non-6LoRH Headers . . . . 6 . . . . . . . . 7
3.2.2. Relative To Other 6LoRH Headers . . . . . . . . . . . 7
4. 6LoWPAN Routing Header General Format . . . . . . . . . . . . 6 8
4.1. Elective Format . . . . . . . . . . . . . . . . . . . . . 7 8
4.2. Critical Format . . . . . . . . . . . . . . . . . . . . . 7 9
4.3. Compressing Addresses . . . . . . . . . . . . . . . . . . 9
4.3.1. Coalescence . . . . . . . . . . . . . . . . . . . . . 10
4.3.2. DODAG Root Address Determination . . . . . . . . . . 10
5. The Routing Header Type 3 (RH3) 6LoRH Header . . . . . . . . 8 11
5.1. RH3-6LoRH General Operation . . . . . . . . . . . . . . . 13
5.2. The Design Point of Popping Entries . . . . . . . . . . . 13
5.3. Compression Reference . . . . . . . . . . . . . . . . . . 14
5.4. Popping Headers . . . . . . . . . . . . . . . . . . . . . 15
5.5. Forwarding . . . . . . . . . . . . . . . . . . . . . . . 16
6. The RPL Packet Information 6LoRH . . . . . . . . . . . . . . 10 16
6.1. Compressing the RPLInstanceID . . . . . . . . . . . . . . 11 18
6.2. Compressing the SenderRank . . . . . . . . . . . . . . . 11 18
6.3. The Overall RPI-6LoRH encoding . . . . . . . . . . . . . 12 19
7. The IP-in-IP 6LoRH Header . . . . . . . . . . . . . . . . . . 14 21
8. Security Considerations . . . . . . . . . . . . . . . . . . . 15 22
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 22
9.1. Reserving Space in 6LoWPAN Dispatch Page 1 . . . . . . . 15 22
9.2. Nex New 6LoWPAN Routing Header Type Registry . . . . . . . . 16 23
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 23
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 23
11.1. Normative References . . . . . . . . . . . . . . . . . . 16 23
11.2. Informative References . . . . . . . . . . . . . . . . . 17 24
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses 25
A.1. Examples Compressing The RPI . . . . . . . . . . . . . . 25
A.2. Example Of Downward Packet In Non-Storing Mode . . . . . 27
A.3. Example of RH3-6LoRH life-cycle . . . . 19

1. Introduction

The design of Low Power and Lossy Networks (LLNs) is generally
focused on saving energy, a . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30

1. Introduction

The design of Low Power and Lossy Networks (LLNs) is generally
focused on saving energy, a very constrained resource in most cases.
The other constraints, such as the memory capacity and the duty
cycling of the LLN devices, derive from that primary concern. Energy
is often available from primary batteries that are expected to last
for years, or is scavenged from the environment in very limited
quantities. Any protocol that is intended for use in LLNs must be
designed with the primary concern of saving energy as a strict
requirement.

Controlling the amount of data transmission is one possible venue to
save energy. In a number of LLN standards, the frame size is limited
to much smaller values than the IPv6 maximum transmission unit (MTU)
of 1280 bytes. In particular, an LLN that relies on the classical
Physical Layer (PHY) of IEEE 802.15.4 [IEEE802154] is limited to 127
bytes per frame. The need to compress IPv6 packets over IEEE
802.15.4 led to the 6LoWPAN Header Compression [RFC6282] work
(6LoWPAN-HC).

Innovative Route-over techniques have been and are still being
developed for routing inside a LLN. In a general fashion, such
techniques require additional information in the packet to provide
loop prevention and to indicate information such as flow
identification, source routing information, etc.

For reasons such as security and the capability to send ICMP errors
back to the source, an original packet must not be tampered with, and
any information that must be inserted in or removed from an IPv6
packet must be placed in an extra IP-in-IP encapsulation. This is
the case when the additional routing information is inserted by a
router on the path of a packet, for instance a mesh root, as opposed
to the source node. This is also the case when some routing
information must be removed from a packet that flows outside the LLN.
When to use RFC 6553, 6554 and IPv6-in-IPv6
[I-D.robles-roll-useofrplinfo] details different cases where RFC
6553, RFC 6554 and IPv6-in-IPv6 encapsulation is required to set the
bases to help defining the compression of RPL routing information in
LLN environments.

When using [RFC6282] the outer IP header of an IP-in-IP encapsulation
may be compressed down to 2 octets in stateless compression and down
to 3 octets in stateful compression when context information must be
added.

0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| 0 | 1 | 1 | TF |NH | HLIM |CID|SAC| SAM | M |DAC| DAM |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

Figure 1: LOWPAN_IPHC base Encoding (RFC6282).

The Stateless Compression of an IPv6 addresses can only happen if the
IPv6 address can de deduced from the MAC addresses, meaning that the
IP end point is also the MAC-layer endpoint. This is generally not
the case in a RPL network which is generally a multi-hop route-over
(i.e., operated at Layer-3) network. A better compression, which
does not involve variable compressions depending on the hop in the
mesh, can be achieved based on the fact that the outer encapsulation
is usually between the source (or destination) of the inner packet
and the root. Also, the inner IP header can only be compressed by
[RFC6282] if all the fields preceding it are also compressed. This
specification makes the inner IP header the first header to be
compressed by [RFC6282], and keeps the inner packet encoded the same
way whether it is encapsulated or not, thus preserving existing
implementations.

As an example, the Routing Protocol for Low Power and Lossy Networks
[RFC6550] (RPL) is designed to optimize the routing operations in
constrained LLNs. As part of this optimization, RPL requires the
addition of RPL Packet Information (RPI) in every packet, as defined
in Section 11.2 of [RFC6550].

The RPL Option for Carrying RPL Information in Data-Plane Datagrams
[RFC6553] specification indicates how the RPI can be placed in a RPL
Option for use in an IPv6 Hop-by-Hop header.

This representation demands a total of 8 bytes, while in most cases
the actual RPI payload requires only 19 bits. Since the Hop-by-Hop
header must not flow outside of the RPL domain, it must be inserted
in packets entering the domain and be removed from packets that leave
the domain. In both cases, this operation implies an IP-in-IP
encapsulation.

Figure 2: IP-in-IP Encapsulation within the LLN.

Additionally, in the case of the Non-Storing Mode of Operation (MOP),
RPL requires a Routing Header type 3 (RH3) as defined in the IPv6
Routing Header for Source Routes with RPL [RFC6554] specification,
for all packets that are routed down a RPL graph. With Non-Storing
RPL, even if the source is a node in the same LLN, the packet must
first reach up the graph to the root so that the root can insert the
RH3 to go down the graph. In any fashion, whether the packet was
originated in a node in the LLN or outside the LLN, and regardless of
whether the packet stays within the LLN or not, as long as the source
of the packet is not the root itself, the source-routing operation
also implies an IP-in-IP encapsulation at the root in order to insert
the RH3.

6TiSCH [I-D.ietf-6tisch-architecture] specifies the operation of IPv6
over the TimeSlotted Channel Hopping [RFC7554] (TSCH) mode of
operation of IEEE 802.15.4. The architecture requires the use of
both RPL and the 6lo adaptation layer over IEEE 802.15.4. Because it
inherits the constraints on frame size from the MAC layer, 6TiSCH
cannot afford to allocate 8 bytes per packet on the RPI. Hence the
requirement for 6LoWPAN header compression of the RPI.

An extensible compression technique is required that simplifies IP-
in-IP encapsulation when it is needed, and optimally compresses
existing routing artifacts found in RPL LLNs.

This specification extends the 6lo adaptation layer framework
([RFC4944],[RFC6282]) so as to carry routing information for route-
over networks based on RPL. The specification includes the formats
necessary for RPL and is extensible for additional formats.

2. Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].

The Terminology used in this document is consistent with and
incorporates that described in `Terminology in Low power And Lossy
Networks' [RFC7102] and [RFC6550].

The terms Route-over and Mesh-under are defined in [RFC6775].

Other terms in use in LLNs are found in [RFC7228].

The term "byte" is used in its now customary sense as a synonym for
"octet".

3. Using the Page Dispatch

The6LoWPAN

The 6LoWPAN Paging Dispatch [I-D.ietf-6lo-paging-dispatch]
specification extends the 6lo adaptation layer framework ([RFC4944],
[RFC6282]) by introducing a concept of "context" in the 6LoWPAN
parser, a context being identified by a Page number. The
specification defines 16 Pages.

This draft operates within Page 1, which is indicated by a Dispatch
Value of binary 11110001.

3.1. New Routing Header Dispatch (6LoRH)

This specification introduces a new 6LoWPAN Routing Header (6LoRH) to
carry IPv6 routing information. The 6LoRH may contain source routing
information such as a compressed form of RH3, as well as other sorts
of routing information such as the RPI and IP-in-IP encapsulation.

The 6LoRH is expressed in a 6loWPAN packet as a Type-Length-Value
(TLV) field, which is extensible for future use.

This specification uses the bit pattern 10xxxxxx in Page 1 for the
new 6LoRH Dispatch. Section 4 describes how RPL artifacts in data
packets can be compressed as 6LoRH headers.

3.2. Placement Of The 6LoRH headers
3.2.1. Relative To Non-6LoRH Headers

Paging Dispatch is parsed and no subsequent Paging Dispatch has been
parsed, the parsing of the packet MUST follow this specification if
the 6LoRH Bit Pattern Section 3.1 is found.

With this specification, the 6LoRH Dispatch is only defined in Page
context is active.

One or more 6LoRH header(s) MAY be placed in a 6LoWPAN packet. A
6LoRH header MUST always be placed before the LOWPAN_IPHC as defined
in 6LoWPAN Header Compression [RFC6282].

Because a 6LoRH header requires a Page 1 context, it MUST always be
placed after any Fragmentation Header and/or Mesh Header [RFC4944].

4. 6LoWPAN Routing Header General Format

The

A 6LoRH reuses in Page 1 header MUST always be placed before the Dispatch Value Bit Pattern of
10xxxxxx.

The Dispatch Value Bit Pattern LOWPAN_IPHC as
defined in 6LoWPAN Header Compression [RFC6282]. It is split designed in two forms of 6LoRH:

Elective (6LoRHE)
such a fashion that may skipped if not understood

Critical (6LoRHC) placing or removing a header that may is encoded with
6LoRH does not be ignored

4.1. Elective Format

The 6LoRHE uses modify the Dispatch Value Bit Pattern part of 101xxxxx. A 6LoRHE
may be ignored and skipped in parsing. If it is ignored, the 6LoRHE packet that is forwarded encoded with no change inside
LoWPAN_IPHC, whether there is an IP-in-IP encapsulation or not. For
instance, the LLN.

0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+
|1|0|1| Length | Type | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+
<-- Length -->

Figure 3: Elective 6LoWPAN Routing Header.

Length:
Length final destination of the 6LoRHE expressed packet is always the one in bytes, excluding
the first 2
bytes. This enables a node to skip LOWPAN_IPHC whether there is a 6LoRHE Routing Header or not.

3.2.2. Relative To Other 6LoRH Headers

IPv6 [RFC2460] defines chains of headers that are introduced by an
IPv6 header and terminated by either another IPv6 header (IP-in-IP)
or an Upper Layer Protocol ULP) header. When an outer header is
stripped from the packet, the whole chain goes with it. When one or
more header(s) are inserted by an intermediate router, that it does
not support and/or cannot parse, for instance if router
normally chains the Type is not
recognized.

Type:
Type of headers and encapsulates the 6LoRHE

4.2. Critical Format

The 6LoRHC uses result in IP-in-IP.

With this specification, the Dispatch Value Bit Pattern chains of 100xxxxx.

A node which does not support the 6LoRHC Type headers MUST silently discard be compressed in
the same order as they appear in the uncompressed form of the packet.

Note: The situation where a node receives a message with a Critical
6LoWPAN Routing Header
This means that it does not understand if there is a critical
administrative error whereby more than one nested IP-in-IP
encapsulations, the wrong device first IP-in-IP encapsulation, with all its chain
of headers, is placed encoded first in a network.
It makes no sense to overburden the constrained device with code that
would send an ICMP error to compressed form.

In the source. Rather, it is expected compressed form of a packet that has RH3 or HbH headers after
the device will raise some management alert indicating that it cannot
operate in this network for that reason. As a result, inner IPv6 header (e.g. if there is no
provision for IP-in-IP encapsulation),
these headers are placed in the exchange of error messages for 6LoRH form before the 6LOWPAN-IPHC
that represents the IPv6 header Section 3.2.1. If this situation, so
it should be avoided by judicious use of administrative control and/ packet gets
encapsulated and some other RH3 or capability indications by HbH headers are added as part of
the device manufacturer.

0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+
|1|0|0| TSE | Type | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+
<-- Length implied by Type/TSE -->

Figure 4: Critical 6LoWPAN Routing Header.

TSE:
Type Specific Extension. The meaning depends on encapsulation, placing the Type, 6LoRH headers next to one another may
present an ambiguity on which
must be known header belong to which chain in all of the nodes. The interpretation of
uncompressed form.

In order to disambiguate the TSE
depends on headers that follow the Type field inner IPv6
header in the uncompressed form from the headers that follows. For instance, follow the
outer IP-in-IP header, it may be
used to transport control bits, is REQUIRED that the number of elements compressed IP-in-IP
header is placed last in an
array, or the length of encoded chain. This means that the remainder
6LoRH headers that are found after the last compressed IP-in-IP
header are to be inserted after the IPv6 header that is encoded with
the 6LOWPAN-IPHC when decompressing the packet.

With regards to the relative placement of the 6LoRHC expressed RH3 and the RPI in a
unit other than bytes.

Type:
Type of the 6LoRHC

5. The Routing Header Type 3 (RH3) 6LoRH Header

The Routing Header type 3 (RH3) 6LoRH (RH3-6LoRH) header
compressed form, it is a
Critical 6LoWPAN Routing Header that provides a compressed form design point for this specification that the RH3,
RH3 entries are consumed as defined the packet progresses down the LLN
Section 5.2. In order to make this operation simpler in [RFC6554] for use by RPL routers. Routers the
compressed form, it is REQUIRED that need to forward a packet with a RH3-6LoRH the in the compressed form, the
addresses along the source route path are expected to be RPL
routers encoded in the order of the
path, and are expected to support this specification. If a non-RPL
router receives a packet with a RH3-6LoRH, this means that there was
a routing error and the packet should compressed RH3 are placed before the compressed
RPI.

4. 6LoWPAN Routing Header General Format

The 6LoRH usesthe Dispatch Value Bit Pattern of 10xxxxxx in Page 1.

The Dispatch Value Bit Pattern is split in two forms of 6LoRH:

Elective (6LoRHE) that may skipped if not understood

Critical (6LoRHC) that may not be dropped so ignored

4.1. Elective Format

The 6LoRHE uses the Type cannot Dispatch Value Bit Pattern of 101xxxxx. A 6LoRHE
may be ignored. ignored and skipped in parsing. If it is ignored, the 6LoRHE
is forwarded with no change inside the LLN.

0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- -+- -+ ... +- -+
|1|0|0| Size |6LoRH Type 0..4| Hop1 | Hop2
|1|0|1| Length | Type | HopN |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- -+- -+ ... +- -+

Size indicates the number of compressed addresses
<-- Length -->

Figure 5: The RH3-6LoRH.

The values 3: Elective 6LoWPAN Routing Header.

Length:
Length of the 6LoRHE expressed in bytes, excluding the first 2
bytes. This enables a node to skip a 6LoRHE header that it does
not support and/or cannot parse, for instance if the RH3-6LoRH Type are an enumeration, 0 to 4. The
form of compression is indicated by not
recognized.

Type:
Type of the Type. 6LoRHE

4.2. Critical Format

The unit (as a number 6LoRHC uses the Dispatch Value Bit Pattern of bytes) in 100xxxxx.

A node which does not support the Size 6LoRHC Type MUST silently discard
the packet.

Note: The situation where a node receives a message with a Critical
6LoWPAN Routing Header that it does not understand is expressed depends on a critical
administrative error whereby the Type as
described wrong device is placed in Figure 6:

+-----------+-----------+
| Type | Size Unit |
+-----------+-----------+
| a network.
It makes no sense to overburden the constrained device with code that
would send an ICMP error to the source. Rather, it is expected that
the device will raise some management alert indicating that it cannot
operate in this network for that reason. As a result, there is no
provision for the exchange of error messages for this situation, so
it should be avoided by judicious use of administrative control and/
or capability indications by the device manufacturer.

0 | 1 |
|
0 1 | 2 |
| 2 | 4 |
| 3 | 4 5 6 7 8 |
| 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+
|1|0|0| TSE | 16 Type |
+-----------+-----------+ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+
<-- Length implied by Type/TSE -->

Figure 6: 4: Critical 6LoWPAN Routing Header.

TSE:
Type Specific Extension. The RH3-6LoRH Types.

In meaning depends on the case Type, which
must be known in all of the nodes. The interpretation of a RH3-6LoRH header, the TSE
depends on the Type field is that follows. For instance, it may be
used as a Size,
which encodes to transport control bits, the number of hops minus 1; so elements in an
array, or the length of the remainder of the 6LoRHC expressed in a Size
unit other than bytes.

Type:
Type of 0 means one
hop, and the maximum that can be encoded is 32 hops. (If more than
32 hops need to be expressed, a sequence of RH3-6LoRH elements can be
employed.) 6LoRHC

4.3. Compressing Addresses

The Next Hop is indicated general technique used in the this draft to compress an address is
first entry of to determine a reference that as a long prefix match with this
address, and then elide that matching piece. In order to reconstruct
the first RH3-6LoRH
header. Upon reception, compress address, the router checks whether receiving node will perform the address
indicated as Next Hop process of
coalescence described in section Section 4.3.1.

One possible reference is one the root of its own addresses, which MUST be the
case in a strict source-routing environment. In RPL DODAG that case, the entry is removed from the RH3-6LoRH header being
traversed. It is used to compress an outer IP-in-IP header, and if
the Size root is decremented. If
that makes the Size zero, source of the whole RH3-6LoRH header is removed. If
there are no more RH3-6LoRH headers, packet, the processing node is technique allows to fully
elide the last
router on source address in the path, which may or may not be collocated with compressed form of the final
destination.

The last hop in IP header. If
the last RH3-6LoRH root is not the last router on encapsulator, then the way to encapsulator address may
still be compressed using the destination in root as reference. How the LLN. In a classical RPL network, all nodes
are routers so address of
the last hop root is effectively the destination as well,
but in the general case, even when there determined is a RH3-6LoRH header
present, discussed in Section 4.3.2.

Once the address of the final destination source of the packet is always indicated in determined, it
becomes the LoWPAN_IPHC [RFC6282].

If some bits reference for the compression of the first address addresses that are
located in compressed RH3 headers that are present inside the RH3-6LoRH header can be
derived from the final destination IP-in-
IP encapsulation in the LoWPAN_IPHC, then that uncompressed form.

4.3.1. Coalescence

An IPv6 compressed address may be compressed; otherwise it is expressed as coalesced with a full IPv6 reference address by
overriding the N rightmost bytes of 128 bits. Next addresses only need to express the delta
from reference address with the previous address.

All addresses in a given RH3-6LoRH header are
compressed in an
identical fashion, down to using address, where N is the identical number of bytes per
address. In order to get different degrees length of compression, multiple
consecutive RH3-6LoRH headers MUST be used

6. The RPL Packet Information 6LoRH

[RFC6550], Section 11.2, specifies the RPL Packet Information (RPI) compressed address,
as a set of fields that are placed indicated by RPL routers in IP packets for the purpose Type of Instance Identification, as well as Loop Avoidance and
Detection.

In particular, the SenderRank, RH3-6LoRH header in Figure 7.

The reference address MAY be a compressed address as well, in which
case it MUST be compressed in a form that is of an equal or greater
length than the scalar metric computed address that is being coalesced.

A compressed address is expanded by coalescing it with a specialized Objective Function such as [RFC6552], indicates reference
address. In the
Rank particular case of a Type 4 RH3-6LoRH, the sender address
is expressed in full and the coalescence is modified at each hop. The SenderRank field a complete override as
illustrated in Figure 5.

RRRRRRRRRRRRRRRRRRRR reference address, may be compressed or not

CCCCCCC compressed address, shorter or same as reference

RRRRRRRRRRRRRCCCCCCC Coalesced address, same compression as reference

Figure 5: Coalescing addresses.

4.3.2. DODAG Root Address Determination

Stateful Address compression requires that some state is used installed in
the devices to validate store the compression information that is elided from
the packet progresses packet. That state is stored in an abstract context table and
some form of index is found in the expected
direction, either upwards or downwards, along packet to obtain the DODAG.

RPL defines compression
information from the RPL context table.

With [RFC6282], the state is provided to the stack by the 6LoWPAN
Neighbor Discovery Protocol (NDP) [RFC6775]. NDP exchanges the
context through 6LoWPAN Context Option for Carrying RPL Information in Data-Plane
Datagrams [RFC6553] to transport Router Advertisement (RA)
messages. In the RPI, which is carried compressed form of the packet, the context can be
signaled in an IPv6
Hop-by-Hop Options Header [RFC2460], typically consuming eight bytes
per packet. a Context Identifier Extension.

With [RFC6553], this specification, the RPL option compression information is encoded provided to
the stack by RPL, and RPL exchanges it through the DODAGID field in
the DAG Information Object (DIO) messages, as six octets, which must described in more
details below. In the compressed form of the packet, the context can
be placed signaled in by the InstanceID in the RPI.

With RPL [RFC6550], the address of DODAG root is known from the
DODAGID field of the DIO messages. For a Hop-by-Hop header Global Instance, the
RPLInstanceID that consumes two additional octets is present in the RPI is enough information to
identify the DODAG that this node participates to and its associated
root. But for a total Local Instance, the address of eight octets. To limit the header's range to just root MUST be
explicit, either in some device configuration or signaled in the
RPL domain,
packet, as the Hop-by-Hop header must be added to (or removed from)
packets that cross source or the border destination address, respectively.

When implicit, the address of the RPL domain.

The 8-byte overhead DODAG root MUST be determined as
follows:

If the whole network is detrimental a single DODAG then the root can be well-
known and does not need to LLN operation, be signaled in particular
with regards to bandwidth the packets. But RPL does
not expose that property and battery constraints. These bytes may
cause it can only be known by a containing frame configuration
applied to grow above maximum frame size, leading to
Layer 2 or 6LoWPAN [RFC4944] fragmentation, which all nodes.

Else, the router that encapsulates the packet and compresses it with
this specification MUST also place an RPI in turn leads the packet as prescribed
by [RFC6550] to enable the identification of the DODAG. The RPI must
be present even more energy expenditure and issues discussed in LLN Fragment
Forwarding and Recovery [I-D.thubert-6lo-forwarding-fragments].

An additional overhead comes from the need, in certain cases, to add case when the router also places an IP-in-IP encapsulation to carry RH3 header
in the Hop-by-Hop header. This packet.

It is
needed when expected that the router RPL implementation provides an abstract
context table, indexed by Global RPLInstanceID, that inserts provides the Hop-by-Hop header is not
address of the
source root of the packet, so DODAG that an error can be returned this nodes participates to the router.
This for
that particular Instance.

5. The Routing Header Type 3 (RH3) 6LoRH Header

## Encoding {#RH3-6LoRH-encoding}

The Routing Header type 3 (RH3) 6LoRH (RH3-6LoRH) header is also a
Critical 6LoWPAN Routing Header that provides a compressed form for
the case when RH3, as defined in [RFC6554] for use by RPL routers. Routers
that need to forward a packet originated by with a RPL node must be
stripped from the Hop-by-Hop header RH3-6LoRH are expected to be routed outside the RPL
domain.

For that reason,
routers and are expected to support this specification defines an IP-in-IP-6LoRH header
in Section 7, but it must be noted that removal of specification. If a non-RPL
router receives a 6LoRH header
does not require manipulation of the packet in the LOWPAN_IPHC, with a RH3-6LoRH, this means that there was
a routing error and
thus, if the source address in packet should be dropped so the LOWPAN_IPHC is Type cannot
be ignored.

0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- -+- -+ ... +- -+
|1|0|0| Size |6LoRH Type 0..4| Hop1 | Hop2 | | HopN |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- -+- -+ ... +- -+

Size indicates the node that
inserted number of compressed addresses

Figure 6: The RH3-6LoRH.

The 6LoRH Type indicates the IP-in-IP-6LoRH header then this situation alone does not
mandate an IP-in-IP-6LoRH compression level used in a given
RH3-6LoRH header.

Note: A typical packet

One or more 6LoRH header(s) MAY be placed in RPL non-storing mode going a 6LoWPAN packet.

It results that all addresses in a given RH3-6LoRH header MUST be
compressed in an identical fashion, down to using the RPL
graph requires an IP-in-IP encapsulation identical
number of bytes per address. In order to get different degrees of
compression, multiple consecutive RH3-6LoRH headers MUST be used.

Type 0 means that the RH3, whereas the RPI
is usually (and quite illegally) omitted, unless it address is important compressed down to
indicate one byte, whereas
Type 4 means that the RPLInstanceID. To match this structure, an optimized
IP-in-IP 6LoRH header address is defined provided in full in Section 7.

As a result, a RPL packet may bear only an RPI-6LoRH header and no
IP-in-IP-6LoRH header. In that case, the source and destination RH3-6LoRH
with no compression. The complete list of Types of RH3-6LoRH and the packet
corresponding compression level are specified by the LOWPAN_IPHC.

As with [RFC6553], the fields provided in the RPI include an 'O', an 'R', and
an 'F' bit, an 8-bit RPLInstanceID (with some internal structure),
and a 16-bit SenderRank.

The remainder of this section defines the RPI-6LoRH header, which is
a Critical 6LoWPAN Routing Header that is designed to transport the
RPI in 6LoWPAN LLNs.

6.1. Compressing the RPLInstanceID

RPL Instances are discussed in [RFC6550], Section 5. A number Figure 7:

+-----------+----------------------+
| 6LoRH | Length of
simple use cases do not require more than one instance, and in such
cases, the instance is expected to be the global Instance 0. A
global RPLInstanceID is encoded in a RPLInstanceID field as follows: compressed |
| Type | IPv6 address (bytes) |
+-----------+----------------------+
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 8 |
| 4 5 6 7
+-+-+-+-+-+-+-+-+
|0| ID | Global RPLInstanceID in 0..127
+-+-+-+-+-+-+-+-+ 16 |
+-----------+----------------------+

Figure 7: RPLInstanceID Field Format for Global Instances.

For The RH3-6LoRH Types.

In the particular case of the global Instance 0, the RPLInstanceID
field is all zeros. This specification allows to elide a
RPLInstanceID field that is all zeros, and defines a I flag that,
when set, signals that RH3-6LoRH header, the TSE field is elided.

6.2. Compressing the SenderRank

The SenderRank is used as a Size,
which encodes the result number of the DAGRank operation on the rank hops minus 1; so a Size of 0 means one
hop, and the sender; here the DAGRank operation is defined in [RFC6550],
Section 3.5.1, as:

DAGRank(rank) = floor(rank/MinHopRankIncrease)

If MinHopRankIncrease maximum that can be encoded is set 32 hops. (If more than
32 hops need to be expressed, a multiple of 256, the least
significant 8 bits sequence of the SenderRank will be all zeroes; by eliding
those, the SenderRank RH3-6LoRH elements can be compressed into a single byte. This
idea is used in [RFC6550] by defining DEFAULT_MIN_HOP_RANK_INCREASE
as 256 and in [RFC6552]
employed.) It results that defaults MinHopRankIncrease to
DEFAULT_MIN_HOP_RANK_INCREASE.

This specification allows to encode the SenderRank as either one or
two bytes, and defines a K flag that, when set, signals that Length in bytes of a single
byte is used.

6.3. The Overall RPI-6LoRH encoding

The RPI-6LoRH RH3-6LoRH header provides a compressed form for
is:

2 + Length_of_compressed_IPv6_address * (Size + 1)

5.1. RH3-6LoRH General Operation

In the RPL RPI.
Routers that need to forward non-compressed form, when the root generates or forwards a
packet with a RPI-6LoRH header are
expected in non-Storing Mode, it needs to be RPL routers that support this specification. If a
non-RPL router receives include a packet with Routing Header type
3 (RH3) [RFC6554] to signal a RPI-6LoRH header, there was strict source-route path to a
routing error and final
destination down the packet should be dropped. Thus DODAG. All the Type field
MUST NOT be ignored.

Since hops along the I flag is not set, path, but the TSE field does not need to be a
length expressed
first one, are encoded in order in bytes. In that case the field is fully reused
for control bits that encode the O, R and F flags from RH3. The last entry in the RPI, as
well as
RH3 is the I final destination and K flags that indicate the compression format.

The Type for destination in the RPI-6LoRH is 5.

The RPI-6LoRH IPv6 header
is immediately followed by the RPLInstanceID
field, unless that field is fully elided, and then first hop along the SenderRank,
which is either compressed into one byte or fully in-lined as two
bytes. source-route path. The I intermediate hops
perform a swap and K flags the Segment-Left field indicates the active entry
in the RPI-6LoRH header indicate whether Routing Header [RFC2460]. The current destination of the RPLInstanceID
packet, which is elided and/or the SenderRank termination of the current segment, is compressed.
Depending on these bits, indicated
at all times by the Length destination address of the RPI-6LoRH may vary as
described hereafter.

0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... -+-+-+
|1|0|0|O|R|F|I|K| 6LoRH Type=5 | Compressed fields |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... -+-+-+

Figure 8: The Generic RPI-6LoRH Format.

O, R, and F bits: IPv6 header.

The O, R, and F bits are defined in [RFC6550],
section 11.2.

I bit: If it is set, handling of the Instance ID RH3-6LoRH is elided different: there is no swap, and a
forwarding router that corresponds to the RPLInstanceID
is first entry in the Global RPLInstanceID 0. If it is not set, first
RH3-6LoRH upon reception of a packet effectively consumes that entry
when forwarding. This means that the octet
immediately following size of a compressed source-
routed packet decreases as the type field contains packet progresses along its path and
that the RPLInstanceID
as specified in [RFC6550], section 5.1.

K bit: If it routing information is set, lost along the SenderRank way. This also means
that an RH3 encoded with 6LoRH is not recoverable and cannot be
protected.

When compressed into one octet, with this specification, all the least significant octet elided. If it is remaining hops MUST
be encoded in order in one or more consecutive RH3-6LoRH headers.
Whether or not set, the
SenderRank, there is fully inlined as two octets.

In Figure 9, a RH3-6LoRH header present, the RPLInstanceID address of
the final destination is indicated in the Global RPLInstanceID 0, and LoWPAN_IPHC at all times
along the
MinHopRankIncrease is a multiple path. Examples of 256 so the least significant byte
is all zeros and can be elided:

0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0|0|O|R|F|1|1| 6LoRH Type=5 | SenderRank |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
I=1, K=1

Figure 9: this are provided in Appendix A.

The most current destination (termination of the current segment) for a
compressed RPI-6LoRH. source-routed packet is indicated in the first entry of
the first RH3-6LoRH. In Figure 10, strict source-routing, that entry MUST match
an address of the RPLInstanceID router that receives the packet.

The last entry in the last RH3-6LoRH is the Global RPLInstanceID 0, but
both bytes last router on the way to
the final destination in the LLN. It is typically a RPL parent of
the SenderRank are significant so final destination, but it can not also be
compressed:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0|0|O|R|F|1|0| 6LoRH Type=5 | SenderRank |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
I=1, K=0

Figure 10: Eliding a router acting at 6LR
[RFC6775] for the RPLInstanceID. destination host.

5.2. The Design Point of Popping Entries

In Figure 11, order to save energy and to optimize the RPLInstanceID chances of transmission
success on lossy media, it is not a design point for this specification
that the Global RPLInstanceID 0,
and entries in the MinHopRankIncrease is RH3 that have been used are removed from the
packet. This creates a multiple discrepancy from the art of 256:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0|0|O|R|F|0|1| 6LoRH Type=5 | RPLInstanceID | SenderRank |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
I=0, K=1

Figure 11: Compressing SenderRank.

In Figure 12, the RPLInstanceID is not the Global RPLInstanceID 0,
and both bytes of the SenderRank are significant:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0|0|O|R|F|0|0| 6LoRH Type=5 | RPLInstanceID | Sender-...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...-Rank |
+-+-+-+-+-+-+-+-+
I=0, K=0

Figure 12: Least compressed form of RPI-6LoRH.

7. The IP-in-IP 6LoRH Header

The IP-in-IP 6LoRH (IP-in-IP-6LoRH) header is an Elective 6LoWPAN IPv6 where
Routing Header that provides are mutable but recoverable.

With this specification, the packet can be expanded at any hop into a
valid IPv6 packet, including a RH3, and compressed form for back. But the encapsulating
IPv6 Header
packet as decompressed along the way will not carry all the consumed
addresses that packet would have if it had been forwarded in the case
uncompressed form.

It is noted that:

The value of keeping the whole RH in an IP-in-IP encapsulation.

An IP-in-IP encapsulation IPv6 header is used for the
receiver to insert a field such as a Routing
Header or an RPI at a router that is not reverse it to use the source of symmetrical path on the packet.
In order way
back.

It is generally not a good idea to send an error back regarding reverse a routing header. The
RH may have been used to stay away from the inserted field, shortest path for some
reason that is only valid on the
address way in (segment routing).

There is no use of reversing a RH in the router that performs the insertion must be provided.

The encapsulation can also enable the last router prior to
Destination to remove present RPL
specifications.

P2P RPL reverses a field such path that was learned reactively, as a part of
the RPI, but this can be done
in protocol operation, which is probably a cleaner way than a
reversed echo on the compressed form data path.

Reversing a header is discouraged by removing the RPI-6LoRH, so [RFC2460] for RH0 unless it
is authenticated, which requires an IP-in-IP-
6LoRH encapsulation Authentication Header (AH).
There is not required no definition of an AH operation for RH3, and there is no
indication that sole purpose.

This field the need exists in LLNs.

It is noted that AH does not critical for routing so the Type can be ignored,
and protect the TSE field contains RH on the Length in bytes.

0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+
|1|0|1| Length | 6LoRH Type 6 | Hop Limit | Encaps. Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+

Figure 13: The IP-in-IP-6LoRH.

The Length of an IP-in-IP-6LoRH header way. AH is expressed in bytes and MUST
be at least 1, to indicate a Hop Limit (HL), that is decremented
validation at
each hop. When the HL reaches 0, the packet is dropped per [RFC2460]

If receiver with the Length sole value of an IP-in-IP-6LoRH header is exactly 1, then enabling the
Encapsulator Address
receiver to reversing it.

A RPL domain is elided, which means usually protected by L2 security and that secures
both RPL itself and the Encapsulator RH in the packets, at every hop. This is
a well-known router, for instance better security than that provided by AH.

In summary, the root in a RPL graph.

If benefit of saving energy and lowering the Length chances of an IP-in-IP-6LoRH header is greater than 1, then an
Encapsulator Address is placed in a compressed form after
loss by sending smaller frames over the LLN are seen as overwhelming
compared to the Hop
Limit field. The value of possibly reversing the Length indicates which compression is
performed on header.

5.3. Compression Reference

In order to optimize the Encapsulator Address. For instance, a Size compression of 3
indicates that IP addresses present in the Encapsulator Address is compressed to 2 bytes.

When it cannot be elided,
RH3 headers, this specification requires that the destination IP 6LoWPAN layer
identifies an address of the IP-in-IP
header that is transported in a RH3-6LoRH header used as reference for the first address of
the list. compression.
With RPL, this specification, the destination address Compression Reference for addresses
found in the IP-in-IP an RH3 header is
implicitly the root in source of the IPv6 packet.

With RPL graph for packets going upwards, [RFC6550], an RH3 header may only be present in Non-Storing
mode, and
the destination address it may only be placed in the IPHC for packets going downwards. If
the implicit value is correct, packet by the destination IP address root of the IP-
in-IP encapsulation can
DODAG, which must be elided.

If the final destination source of the resulting IPv6 packet
[RFC2460]. In this case, the address used as Compression Reference
is a leaf that does not
support this specification, then the chain address of 6LoRH headers must be
stripped by the RPL/6LR router to which the leaf is attached. In
that example, root, and it can be implicit when the destination IP
address of the IP-in-IP header
cannot root is.

The Compression Reference MUST be elided.

In determined as follows:

The reference address may be obtained by configuration. The
configuration may indicate either the special case where address in full, or the
identifier of a 6LoRH header is used to route 6LoWPAN
fragments, Context that carries the destination address is not accessible in [RFC6775],
for instance one of the IPHC on
all fragments 16 Context Identifiers used in LOWPAN-IPHC
[RFC6282].

Else, and can be elided only for if there is no IP-in-IP encapsulation, the first fragment and for
packets going upwards.

8. Security Considerations

The security considerations of [RFC4944], [RFC6282], and [RFC6553]
apply.

Using a compressed format as opposed to source address
in the full in-line format IPv6 header that is
logically equivalent and compressed with LOWPAN-IPHC is believed to not create an opening for a
new threat when compared to [RFC6550], [RFC6553] and [RFC6554].

9. IANA Considerations

This specification reserves Dispatch Value Bit Patterns within the
6LoWPAN Dispatch Page 1 as follows:

101xxxxx: for Elective 6LoWPAN Routing Headers

100xxxxx: for Critical 6LoWPAN Routing Headers.

9.2. Nex 6LoWPAN Routing Header Type Registry

This document creates an IANA registry
reference for the 6LoWPAN Routing Header
Type, compression.

Else, and assigns if the following values:

0..4: RH3-6LoRH [RFCthis]

5: RPI-6LoRH [RFCthis]

6: IP-in-IP-6LoRH [RFCthis]

10. Acknowledgments

The authors wish to thank Tom Phinney, Thomas Watteyne, Tengfei
Chang, Martin Turon, James Woodyatt, Samita Chakrabarti, Jonathan
Hui, Gabriel Montenegro IP-in-IP compression specified in this document is
used and Ralph Droms for constructive reviews to the design Encapsulator Address is provided, then the Encapsulator
Address is the reference.

5.4. Popping Headers

Upon reception, the router checks whether the address in the 6lo Working Group. The overall discussion involved
participants to first
entry of the 6MAN, 6TiSCH and ROLL WGs, thank you all.
Special thanks to first RH3-6LoRH one of its own addresses. In that case,
router MUST consume that entry before forwarding, which is an action
of popping from a stack, where the chairs stack is effectively the sequence
of entries in consecutive RH3-6LoRH headers.

Popping an entry of an RH3-6LoRH header is a recursive action
performed as follows:

If the ROLL WG, Michael Richardson and
Ines Robles, Size of the RH3-6LoRH header is 1 or more, indicating that
there are at least 2 entries in the header, the router removes the
first entry and Brian Haberman, Internet Area A-D, decrements the Size (by 1).

Else (meaning that this is the last entry in the RH3-6LoRH header),
and Adrian
Farrel, Routing Area A-D, for driving if there is no next RH3-6LoRH header after this complex effort across
Working Groups then the
RH3-6LoRH is removed.

Else, if there is a next RH3-6LoRH of a Type with a larger or equal
value, meaning a same or lesser compression yielding same or larger
compressed forms, then the RH3-6LoRH is removed.

Else, the first entry of the next RH3-6LoRH is popped from the next
RH3-6LoRH and Areas.

11. References

11.1. Normative References

[I-D.ietf-6lo-paging-dispatch]
Thubert, P., "6LoWPAN Paging Dispatch", draft-ietf-6lo-
paging-dispatch-01 (work coalesced with the first entry of this RH3-6LoRH.

At the end of the process, if there is no more RH3-6LoRH in progress), January 2016.

[IEEE802154]
IEEE standard for Information Technology, "IEEE std.
802.15.4, Part. 15.4: Wireless Medium Access Control (MAC) the
packet, then the processing node is the last router along the source
route path.

5.5. Forwarding

When receiving a packet with a RH3-6LoRH, a router determines the
IPv6 address of the current segment endpoint.

If strict source routing is enforced and Physical Layer (PHY) Specifications for Low-Rate
Wireless Personal Area Networks", 2015.

[RFC2119] Bradner, S., "Key words thus router is not the
segment endpoint for use the packet then this router MUST drop the
packet.

If this router is the current segment endpoint, then the router pops
its address as described 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. Section 5.4 and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>.

[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., continues processing the
packet.

If there is still a RH3-6LoRH, then the router determines the new
segment endpoint and D. Culler,
"Transmission routes the packet towards that endpoint.

Otherwise the router uses the destination in the inner IP header to
forward or accept the packet.

The segment endpoint of a packet MUST be determined as follows:

The router first determines the Compression Reference as discussed in
Section 4.3.1.

The router then coalesces the Compression Reference with the first
entry of the first RH3-6LoRH header as discussed in Section 5.3. If
the type of the RH3-6LoRH header is type 4 then the coalescence is a
full override.

Since the Compression Reference is an uncompressed address, the
coalesced IPv6 Packets over IEEE 802.15.4
Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
<http://www.rfc-editor.org/info/rfc4944>.

[RFC6282] Hui, J., Ed. address is also expressed in the full 128bits.

An example of this operation is provided in Appendix A.3.

6. The RPL Packet Information 6LoRH

[RFC6550], Section 11.2, specifies the RPL Packet Information (RPI)
as a set of fields that are placed by RPL routers in IP packets for
the purpose of Instance Identification, as well as Loop Avoidance and P. Thubert, "Compression Format
Detection.

In particular, the SenderRank, which is the scalar metric computed by
a specialized Objective Function such as [RFC6552], indicates the
Rank of the sender and is modified at each hop. The SenderRank field
is used to validate that the packet progresses in the expected
direction, either upwards or downwards, along the DODAG.

RPL defines the RPL Option for IPv6 Carrying RPL Information in Data-Plane
Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
DOI 10.17487/RFC6282, September 2011, [RFC6553] to transport the RPI, which is carried in an IPv6
Hop-by-Hop Options Header [RFC2460], typically consuming eight bytes
per packet.

With [RFC6553], the RPL option is encoded as six octets, which must
be placed in a Hop-by-Hop header that consumes two additional octets
for a total of eight octets. To limit the header's range to just the
RPL domain, the Hop-by-Hop header must be added to (or removed from)
packets that cross the border of the RPL domain.

The 8-byte overhead is detrimental to LLN operation, in particular
with regards to bandwidth and battery constraints. These bytes may
cause a containing frame to grow above maximum frame size, leading to
Layer 2 or 6LoWPAN [RFC4944] fragmentation, which in turn leads to
even more energy expenditure and issues discussed in LLN Fragment
Forwarding and Recovery [I-D.thubert-6lo-forwarding-fragments].

An additional overhead comes from the need, in certain cases, to add
an IP-in-IP encapsulation to carry the Hop-by-Hop header. This is
needed when the router that inserts the Hop-by-Hop header is not the
source of the packet, so that an error can be returned to the router.
This is also the case when a packet originated by a RPL node must be
stripped from the Hop-by-Hop header to be routed outside the RPL
domain.

For that reason, this specification defines an IP-in-IP-6LoRH header
in Section 7, but it must be noted that removal of a 6LoRH header
does not require manipulation of the packet in the LOWPAN_IPHC, and
thus, if the source address in the LOWPAN_IPHC is the node that
inserted the IP-in-IP-6LoRH header then this situation alone does not
mandate an IP-in-IP-6LoRH header.

Note: A typical packet in RPL non-storing mode going down the RPL
graph requires an IP-in-IP encapsulation of the RH3, whereas the RPI
is usually (and quite illegally) omitted, unless it is important to
indicate the RPLInstanceID. To match this structure, an optimized
IP-in-IP 6LoRH header is defined in Section 7.

As a result, a RPL packet may bear only an RPI-6LoRH header and no
IP-in-IP-6LoRH header. In that case, the source and destination of
the packet are specified by the LOWPAN_IPHC.

As with [RFC6553], the fields in the RPI include an 'O', an 'R', and
an 'F' bit, an 8-bit RPLInstanceID (with some internal structure),
and a 16-bit SenderRank.

The remainder of this section defines the RPI-6LoRH header, which is
a Critical 6LoWPAN Routing Header that is designed to transport the
RPI in 6LoWPAN LLNs.

6.1. Compressing the RPLInstanceID

RPL Instances are discussed in [RFC6550], Section 5. A number of
simple use cases do not require more than one instance, and in such
cases, the instance is expected to be the global Instance 0. A
global RPLInstanceID is encoded in a RPLInstanceID field as follows:

0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|0| ID | Global RPLInstanceID in 0..127
+-+-+-+-+-+-+-+-+

Figure 8: RPLInstanceID Field Format for Global Instances.

For the particular case of the global Instance 0, the RPLInstanceID
field is all zeros. This specification allows to elide a
RPLInstanceID field that is all zeros, and defines a I flag that,
when set, signals that the field is elided.

6.2. Compressing the SenderRank

The SenderRank is the result of the DAGRank operation on the rank of
the sender; here the DAGRank operation is defined in [RFC6550],
Section 3.5.1, as:

DAGRank(rank) = floor(rank/MinHopRankIncrease)

If MinHopRankIncrease is set to a multiple of 256, the least
significant 8 bits of the SenderRank will be all zeroes; by eliding
those, the SenderRank can be compressed into a single byte. This
idea is used in [RFC6550] by defining DEFAULT_MIN_HOP_RANK_INCREASE
as 256 and in [RFC6552] that defaults MinHopRankIncrease to
DEFAULT_MIN_HOP_RANK_INCREASE.

This specification allows to encode the SenderRank as either one or
two bytes, and defines a K flag that, when set, signals that a single
byte is used.

6.3. The Overall RPI-6LoRH encoding

The RPI-6LoRH header provides a compressed form for the RPL RPI.
Routers that need to forward a packet with a RPI-6LoRH header are
expected to be RPL routers that support this specification. If a
non-RPL router receives a packet with a RPI-6LoRH header, there was a
routing error and the packet should be dropped. Thus the Type field
MUST NOT be ignored.

Since the I flag is not set, the TSE field does not need to be a
length expressed in bytes. In that case the field is fully reused
for control bits that encode the O, R and F flags from the RPI, as
well as the I and K flags that indicate the compression format.

The Type for the RPI-6LoRH is 5.

The RPI-6LoRH header is immediately followed by the RPLInstanceID
field, unless that field is fully elided, and then the SenderRank,
which is either compressed into one byte or fully in-lined as two
bytes. The I and K flags in the RPI-6LoRH header indicate whether
the RPLInstanceID is elided and/or the SenderRank is compressed.
Depending on these bits, the Length of the RPI-6LoRH may vary as
described hereafter.

Figure 9: The Generic RPI-6LoRH Format.

O, R, and F bits: The O, R, and F bits are defined in [RFC6550],
section 11.2.

I bit: If it is set, the Instance ID is elided and the RPLInstanceID
is the Global RPLInstanceID 0. If it is not set, the octet
immediately following the type field contains the RPLInstanceID
as specified in [RFC6550], section 5.1.

K bit: If it is set, the SenderRank is compressed into one octet,
with the least significant octet elided. If it is not set, the
SenderRank, is fully inlined as two octets.

In Figure 10, the RPLInstanceID is the Global RPLInstanceID 0, and
the MinHopRankIncrease is a multiple of 256 so the least significant
byte is all zeros and can be elided:

Figure 10: The most compressed RPI-6LoRH.

In Figure 11, the RPLInstanceID is the Global RPLInstanceID 0, but
both bytes of the SenderRank are significant so it can not be
compressed:

Figure 11: Eliding the RPLInstanceID.

In Figure 12, the RPLInstanceID is not the Global RPLInstanceID 0,
and the MinHopRankIncrease is a multiple of 256:

Figure 12: Compressing SenderRank.

In Figure 13, the RPLInstanceID is not the Global RPLInstanceID 0,
and both bytes of the SenderRank are significant:

Figure 13: Least compressed form of RPI-6LoRH.

7. The IP-in-IP 6LoRH Header

The IP-in-IP 6LoRH (IP-in-IP-6LoRH) header is an Elective 6LoWPAN
Routing Header that provides a compressed form for the encapsulating
IPv6 Header in the case of an IP-in-IP encapsulation.

An IP-in-IP encapsulation is used to insert a field such as a Routing
Header or an RPI at a router that is not the source of the packet.
In order to send an error back regarding the inserted field, the
address of the router that performs the insertion must be provided.

The encapsulation can also enable the last router prior to
Destination to remove a field such as the RPI, but this can be done
in the compressed form by removing the RPI-6LoRH, so an IP-in-IP-
6LoRH encapsulation is not required for that sole purpose.

This field is not critical for routing so the Type can be ignored,
and the TSE field contains the Length in bytes.

Figure 14: The IP-in-IP-6LoRH.

The Length of an IP-in-IP-6LoRH header is expressed in bytes and MUST
be at least 1, to indicate a Hop Limit (HL), that is decremented at
each hop. When the HL reaches 0, the packet is dropped per
[RFC2460].

If the Length of an IP-in-IP-6LoRH header is exactly 1, then the
Encapsulator Address is elided, which means that the Encapsulator is
a well-known router, for instance the root in a RPL graph.

With this specification, an optimal compression of IP-in-IP
encapsulation can be achieved if an endpoint of the packet is the
root of the RPL DODAG associated to the Instance that is used to
forward the packet, and the root address is known implicitly as
opposed to signaled explicitly in the data packets.

If the Length of an IP-in-IP-6LoRH header is greater than 1, then an
Encapsulator Address is placed in a compressed form after the Hop
Limit field. The value of the Length indicates which compression is
performed on the Encapsulator Address. For instance, a Size of 3
indicates that the Encapsulator Address is compressed to 2 bytes.

The reference for the compression is the address of the root of the
DODAG. The way the address of the root is determined is discussed in
Section 4.3.2.

When it cannot be elided, the destination IP address of the IP-in-IP
header is transported in a RH3-6LoRH header as the first address of
the list.

With RPL, the destination address in the IP-in-IP header is
implicitly the root in the RPL graph for packets going upwards, and
the destination address in the IPHC for packets going downwards. If
the implicit value is correct, the destination IP address of the IP-
in-IP encapsulation can be elided.

If the final destination of the packet is a leaf that does not
support this specification, then the chain of 6LoRH headers must be
stripped by the RPL/6LR router to which the leaf is attached. In
that example, the destination IP address of the IP-in-IP header
cannot be elided.

In the special case where a 6LoRH header is used to route 6LoWPAN
fragments, the destination address is not accessible in the IPHC on
all fragments and can be elided only for the first fragment and for
packets going upwards.

8. Security Considerations

The security considerations of [RFC4944], [RFC6282], and [RFC6553]
apply.

Using a compressed format as opposed to the full in-line format is
logically equivalent and is believed to not create an opening for a
new threat when compared to [RFC6550], [RFC6553] and [RFC6554].

9. IANA Considerations

This specification reserves Dispatch Value Bit Patterns within the
6LoWPAN Dispatch Page 1 as follows:

101xxxxx: for Elective 6LoWPAN Routing Headers

100xxxxx: for Critical 6LoWPAN Routing Headers.

9.2. New 6LoWPAN Routing Header Type Registry

This document creates an IANA registry for the 6LoWPAN Routing Header
Type, and assigns the following values:

0..4: RH3-6LoRH [RFCthis]

5: RPI-6LoRH [RFCthis]

6: IP-in-IP-6LoRH [RFCthis]

10. Acknowledgments

The authors wish to thank Tom Phinney, Thomas Watteyne, Tengfei
Chang, Martin Turon, James Woodyatt, Samita Chakrabarti, Jonathan
Hui, Gabriel Montenegro and Ralph Droms for constructive reviews to
the design in the 6lo Working Group. The overall discussion involved
participants to the 6MAN, 6TiSCH and ROLL WGs, thank you all.
Special thanks to the chairs of the ROLL WG, Michael Richardson and
Ines Robles, and Brian Haberman, Internet Area A-D, and Adrian
Farrel, Routing Area A-D, for driving this complex effort across
Working Groups and Areas.

11. References

11.1. Normative References

[I-D.ietf-6lo-paging-dispatch]
Thubert, P., "6LoWPAN Paging Dispatch", draft-ietf-6lo-
paging-dispatch-01 (work in progress), January 2016.

[IEEE802154]
IEEE standard for Information Technology, "IEEE std.
802.15.4, Part. 15.4: Wireless Medium Access Control (MAC)
and Physical Layer (PHY) Specifications for Low-Rate
Wireless Personal Area Networks", 2015.

[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, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>.

[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
"Transmission of IPv6 Packets over IEEE 802.15.4
Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
<http://www.rfc-editor.org/info/rfc4944>.

[RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
DOI 10.17487/RFC6282, September 2011,
<http://www.rfc-editor.org/info/rfc6282>.

[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: 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>.

[RFC6552] Thubert, P., Ed., "Objective Function Zero for the Routing
Protocol for Low-Power and Lossy Networks (RPL)",
RFC 6552, DOI 10.17487/RFC6552, March 2012,
<http://www.rfc-editor.org/info/rfc6552>.

[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>.

[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>.

[RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for
Constrained-Node Networks", RFC 7228,
DOI 10.17487/RFC7228, May 2014,
<http://www.rfc-editor.org/info/rfc7228>.

11.2. Informative References

[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.robles-roll-useofrplinfo]
Robles, I., Richardson, M., and P. Thubert, "When to use
RFC 6553, 6554 and IPv6-in-IPv6", draft-robles-roll-
useofrplinfo-02 (work in progress), October 2015.

[I-D.thubert-6lo-forwarding-fragments]
Thubert, P. and J. Hui, "LLN Fragment Forwarding and
Recovery", draft-thubert-6lo-forwarding-fragments-02 (work
in progress), November 2014.

[RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
Bormann, "Neighbor Discovery Optimization for IPv6 over
Low-Power Wireless Personal Area Networks (6LoWPANs)",
RFC 6775, DOI 10.17487/RFC6775, November 2012,
<http://www.rfc-editor.org/info/rfc6775>.

[RFC7554] Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using
IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the
Internet of Things (IoT): Problem Statement", RFC 7554,
DOI 10.17487/RFC7554, May 2015,
<http://www.rfc-editor.org/info/rfc7554>.

Appendix A. Examples

A.1. Examples Compressing The RPI

The example in Figure 15 illustrates the 6LoRH compression of a
classical packet in Storing Mode in all directions, as well as in
non-Storing mode for a packet going up the DODAG following the
default route to the root. In this particular example, a
fragmentation process takes place per [RFC4944], and the fragment
headers must be placed in Page 0 before switching to Page 1:

+- ... -+- ... -+-+ ... -+- ... +-+-+ ... -+-+-+-+-+-+-+-+-+-+...
|Frag type|Frag hdr |11110001| RPI- |IP-in-IP| LOWPAN-IPHC | ...
|RFC 4944 |RFC 4944 | Page 1 | 6LoRH | 6LoRH | |
+- ... -+- ... -+-+ ... -+- ... +-+-+ ... -+-+-+-+-+-+-+-+-+-+...
<- RFC 6282 ->
No RPL artifact

Figure 15: Example Compressed Packet with RPI.

In Storing Mode, if the packet stays within the RPL domain, then it
is possible to save the IP-in-IP encapsulation, in which case only
the RPI is compressed with a 6LoRH, as illustrated in Figure 16 in
the case of a non-fragmented ICMP packet:

Figure 16: Example ICMP Packet with RPI in Storing Mode.

The format in Figure 16 is logically equivalent to the non-compressed
format illustrated in Figure 17:

+-+-+-+- ... -+-+-+-+ ... -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...
| IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550, DOI 10.17487/
RFC6550, March 2012,
<http://www.rfc-editor.org/info/rfc6550>.

Figure 17: Uncompressed ICMP Packet with RPI.

For a UDP packet, the Routing
Protocol for Low-Power and Lossy Networks (RPL)", transport header can be compressed with 6LoWPAN
HC [RFC6282] as illustrated in Figure 18:

+- ... -+- ... -+-+-+-+- ... +-+-+-+-+-+-+-+-+-+- ... +-+-+-+-+-+...
|11110001| RPI-6LoRH | NH = 1 |11110|C| P | Compressed |UDP ...
|Page 1 | type 5 | 6LOWPAN-IPHC | UDP | | | UDP header |Payload
+- ... -+- ... -+-+-+-+- ... +-+-+-+-+-+-+-+-+-+- ... +-+-+-+-+-+...
<- RFC
6552, DOI 10.17487/RFC6552, March 2012,
<http://www.rfc-editor.org/info/rfc6552>.

[RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low-
Power and Lossy Networks (RPL) Option for Carrying 6282 ->
No RPL
Information artifact

Figure 18: Uncompressed ICMP Packet with RPI.

If the packet is received from the Internet in Data-Plane Datagrams", Storing Mode, then the
root is supposed to encapsulate the packet to insert the RPI. The
resulting format would be as represented in Figure 19:

+-+-+-+-+-+-+- ... -+-+-- ... -+-+- ... -+-+-+-+-+-+-+ ... -+-+-+-+...
|11110001 | RPI-6LoRH | IP-in-IP | NH=1 |11110CPP| Compressed | UDP
|Page 1 | | 6LoRH | IPHC | UDP | UDP header | Payload
+-+-+-+-+-+-+- ... -+-+-- ... -+-+- ... -+-+-+-+-+-+-+ ... -+-+-+-+...
<- 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 6282 ->
No RPL artifact

Figure 19: RPI inserted by the root in Storing Mode.

A.2. Example Of Downward Packet In Non-Storing Mode

The example illustrated in Figure 20 is a classical packet in non-
Storing mode for Source Routes with a packet going down 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>.

[RFC7102] Vasseur, JP., "Terms Used DODAG following a source
routed path from the root. Say that we have 4 forwarding hops to
reach a destination. In the non-compressed form, when the root
generates the packet, the last 3 hops are encoded in a Routing for Low-Power and
Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January
2014, <http://www.rfc-editor.org/info/rfc7102>.

[RFC7228] Bormann, C., Ersue, M., Header
type 3 (RH3) and A. Keranen, "Terminology for
Constrained-Node Networks", RFC 7228, DOI 10.17487/
RFC7228, May 2014,
<http://www.rfc-editor.org/info/rfc7228>.

11.2. Informative References

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

[I-D.robles-roll-useofrplinfo]
Robles, I., Richardson, M., and P. Thubert, "When to use
RFC 6553, 6554 the packet. The
intermediate hops perform a swap and IPv6-in-IPv6", draft-robles-roll-
useofrplinfo-02 (work the hop count indicates the
current active hop [RFC2460], [RFC6554].

When compressed with this specification, the 4 hops are encoded in progress), October 2015.

[I-D.thubert-6lo-forwarding-fragments]
Thubert, P. and J. Hui, "LLN Fragment Forwarding
RH3-6LoRH when the root generates the packet, and
Recovery", draft-thubert-6lo-forwarding-fragments-02 (work the final
destination is left in progress), November 2014.

[RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
Bormann, "Neighbor Discovery Optimization for IPv6 over
Low-Power Wireless Personal Area Networks (6LoWPANs)", RFC
6775, DOI 10.17487/RFC6775, November 2012,
<http://www.rfc-editor.org/info/rfc6775>.

[RFC7554] Watteyne, T., Ed., Palattella, M., the LOWPAN-IPHC. There is no swap, and L. Grieco, "Using
IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the
Internet of Things (IoT): Problem Statement", RFC 7554,
DOI 10.17487/RFC7554, May 2015,
<http://www.rfc-editor.org/info/rfc7554>.

Appendix A. Examples

The example in Figure 14 illustrates
forwarding node that corresponds to the first entry effectively
consumes it when forwarding, which means that the 6LoRH compression size of a
classical the encoded
packet decreases and that the hop information is lost.

If the last hop in Storing Mode a RH3-6LoRH is not the final destination then it
removes the RH3-6LoRH before forwarding.

In the particular example illustrated in Figure 20, all directions, as well as addresses in
non-Storing mode for a packet going up
the DODAG following are assigned from a same /112 prefix and the
default route last 2 octets
encoding an identifier such as a IEEE 802.15.4 short address. In
that case, all addresses can be compressed to 2 octets, using the root. In
root address as reference. There will be one RH3_6LoRH header, with,
in this particular example, a
fragmentation process takes place per [RFC4944], 3 compressed addresses:

+-+-+-+-+-+-+- ... +-+-+- ... -+-+-- ... -+-+- ... -+-+-+-+-+ ... +-...
|11110001 |RH3-6LoRH | RPI-6LoRH | IP-in-IP | NH=1 |11110CPP| UDP | UDP
|Page 1 |Type1 S=2 | | 6LoRH | IPHC | UDP | hdr |load
+-+-+-+-+-+-+- ... +-+-+- ... -+-+-- ... -+-+- ... -+-+-+-+-+ ... +-...
<-8bytes-> <- RFC 6282 ->
No RPL artifact

Figure 20: Example Compressed Packet with RH3.

One may note that the RPI is provided. This is because the address
of the root that is the source of the IP-in-IP header is elided and
inferred from the fragment
headers must be placed InstanceID in Page 0 before switching the RPI. Once found from a local
context, that address is used as Compression Reference to Page 1: expand
addresses in the RH3-6LoRH.

With the RPL specifications available at the time of writing this
draft, the root is the only node that may incorporate a RH3 in an IP
packet. When the root forwards a packet that it did not generate, it
has to encapsulate the packet with IP-in-IP.

But if the root generates the packet towards a node in its DODAG,
then it should avoid the extra IP-in-IP as illustrated in Figure 21:

Figure 14: Example Compressed Packet with RPI.

The example illustrated in

Figure 15 21: compressed RH3 4*2bytes entries sourced by root.

Note: the RPI is a classical packet in non-
Storing mode not represented though RPL [RFC6550] generally
expects it. In this particular case, since the Compression Reference
for a packet going down the DODAG following a source
routed path from RH3-6LoRH is the root; in this particular example, addresses source address in the DODAG are assigned LOWPAN-IPHC, and the
routing is strict along the source route path, the RPI does not
appear to be absolutely necessary.

In Figure 21, all the nodes along the source route path share a same
/112 prefix, prefix. This is typical of IPv6 addresses derived from an
IEEE802.15.4 short address, as long as all the nodes share a same
PAN-ID. In that case, a type-1 RH3-6LoRH header can be used for instance
encoding. The IPv6 address of the root is taken from as reference, and
only the last 2 octets of the address of the intermediate hops is
encoded. The Size of 3 indicates 4 hops, resulting in a RH3-6LoRH of
10 bytes.

A.3. Example of RH3-6LoRH life-cycle

This section illustrates the operation specified in Section 5.5 of
forwarding a packet with a /64 subnet compressed RH3 along an A->B->C->D source
route path. The operation of popping addresses is exemplified at
each hop.

Packet as received by node A
----------------------------
Type 3 RH3-6LoRH Size = 0 AAAA AAAA AAAA AAAA
Type 1 RH3-6LoRH Size = 0 BBBB
Type 2 RH3-6LoRH Size = 1 CCCC CCCC
DDDD DDDD

Step 1 popping BBBB the first entry of the next RH3-6LoRH
Step 2 next is if larger value (2 vs. 1) the RH3-6LoRH is removed

Type 3 RH3-6LoRH Size = 0 AAAA AAAA AAAA AAAA
Type 2 RH3-6LoRH Size = 1 CCCC CCCC
DDDD DDDD

Step 3: recursion ended, coalescing BBBB with the first 6 octets of the suffix set entry
Type 3 RH3-6LoRH Size = 0 AAAA AAAA AAAA BBBB

Step 4: routing based on next segment endpoint to
a constant such B

Figure 22: Processing at Node A.

Packet as all zeroes. In that case, all addresses but received by node B
----------------------------
Type 3 RH3-6LoRH Size = 0 AAAA AAAA AAAA BBBB
Type 2 RH3-6LoRH Size = 1 CCCC CCCC
DDDD DDDD

Step 1 popping CCCC CCCC, the first can be compressed to 2 octets, which means that there will be entry of the next RH3-6LoRH
Step 2
RH3_6LoRH headers, one to store removing the first complete address entry and decrementing the
one Size (by 1)

Type 3 RH3-6LoRH Size = 0 AAAA AAAA AAAA BBBB
Type 2 RH3-6LoRH Size = 0 DDDD DDDD

Step 3: recursion ended, coalescing CCCC CCCC with the first entry
Type 3 RH3-6LoRH Size = 0 AAAA AAAA CCCC CCCC

Step 4: routing based on next segment endpoint to store C

Figure 23: Processing at Node B.

Packet as received by node C
----------------------------

Type 3 RH3-6LoRH Size = 0 AAAA AAAA CCCC CCCC
Type 2 RH3-6LoRH Size = 0 DDDD DDDD

Step 1 popping DDDD DDDD, the sequence first entry of addresses compressed to the next RH3-6LoRH
Step 2 octets (in
this example, the RH3-6LoRH is removed

Type 3 of them):

Step 3: recursion ended, coalescing DDDD DDDDD with the first entry
Type 3 RH3-6LoRH Size = 0 AAAA AAAA DDDD DDDD

Step 4: routing based on next segment endpoint to D

Figure 15: Example Compressed 24: Processing at Node C.

Packet with RH3.

Note: as received by node D
----------------------------
Type 3 RH3-6LoRH Size = 0 AAAA AAAA DDDD DDDD

Step 1 the RPI RH3-6LoRH is not represented since most implementations actually
refrain from placing it in a source routed packet though [RFC6550]
generally expects it. removed.
Step 2 no more header, routing based on inner IP header.

Figure 25: Processing at Node D.

Authors' Addresses

Pascal Thubert (editor)
Cisco Systems
Building D - Regus
45 Allee des Ormes
BP1200
MOUGINS - Sophia Antipolis 06254
FRANCE

Phone: +33 4 97 23 26 34
Email: pthubert@cisco.com
Carsten Bormann
Universitaet Bremen TZI
Postfach 330440
Bremen D-28359
Germany

Phone: +49-421-218-63921
Email: cabo@tzi.org

Laurent Toutain
Institut MINES TELECOM; TELECOM Bretagne
2 rue de la Chataigneraie
CS 17607
Cesson-Sevigne Cedex 35576
France

Email: Laurent.Toutain@telecom-bretagne.eu

Robert Cragie
ARM Ltd.
110 Fulbourn Road
Cambridge CB1 9NJ
UK

Email: robert.cragie@gridmerge.com