< draft-ietf-roll-routing-dispatch-01.txt   draft-ietf-roll-routing-dispatch-02.txt >
roll P. Thubert, Ed. roll P. Thubert, Ed.
Internet-Draft Cisco Internet-Draft Cisco
Intended status: Standards Track C. Bormann Intended status: Standards Track C. Bormann
Expires: March 20, 2017 Uni Bremen TZI Expires: April 22, 2017 Uni Bremen TZI
L. Toutain L. Toutain
IMT-TELECOM Bretagne IMT-TELECOM Bretagne
R. Cragie R. Cragie
ARM ARM
September 16, 2016 October 19, 2016
6LoWPAN Routing Header 6LoWPAN Routing Header
draft-ietf-roll-routing-dispatch-01 draft-ietf-roll-routing-dispatch-02
Abstract Abstract
This specification introduces a new 6LoWPAN dispatch type for use in This specification introduces a new 6LoWPAN dispatch type for use in
6LoWPAN Route-Over topologies, that initially covers the needs of RPL 6LoWPAN Route-Over topologies, that initially covers the needs of RPL
(RFC6550) data packets compression. Using this dispatch type, this (RFC6550) data packets compression. Using this dispatch type, this
specification defines a method to compress RPL Option (RFC6553) specification defines a method to compress RPL Option (RFC6553)
information and Routing Header type 3 (RFC6554), an efficient IP-in- information and Routing Header type 3 (RFC6554), an efficient IP-in-
IP technique and is extensible for more applications. IP technique and is extensible for more applications.
skipping to change at page 1, line 40 skipping to change at page 1, line 40
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 20, 2017. This Internet-Draft will expire on April 22, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 1, line 67 skipping to change at page 1, line 67
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Using the Page Dispatch . . . . . . . . . . . . . . . . . . . 6 3. Using the Page Dispatch . . . . . . . . . . . . . . . . . . . 6
3.1. New Routing Header Dispatch (6LoRH) . . . . . . . . . . . 6 3.1. New Routing Header Dispatch (6LoRH) . . . . . . . . . . . 6
3.2. Placement Of 6LoRH headers . . . . . . . . . . . . . . . 7 3.2. Placement Of 6LoRH headers . . . . . . . . . . . . . . . 7
3.2.1. Relative To Non-6LoRH Headers . . . . . . . . . . . . 7 3.2.1. Relative To Non-6LoRH Headers . . . . . . . . . . . . 7
3.2.2. Relative To Other 6LoRH Headers . . . . . . . . . . . 7 3.2.2. Relative To Other 6LoRH Headers . . . . . . . . . . . 7
4. 6LoWPAN Routing Header General Format . . . . . . . . . . . . 8 4. 6LoWPAN Routing Header General Format . . . . . . . . . . . . 8
4.1. Elective Format . . . . . . . . . . . . . . . . . . . . . 8 4.1. Elective Format . . . . . . . . . . . . . . . . . . . . . 9
4.2. Critical Format . . . . . . . . . . . . . . . . . . . . . 9 4.2. Critical Format . . . . . . . . . . . . . . . . . . . . . 9
4.3. Compressing Addresses . . . . . . . . . . . . . . . . . . 9 4.3. Compressing Addresses . . . . . . . . . . . . . . . . . . 10
4.3.1. Coalescence . . . . . . . . . . . . . . . . . . . . . 10 4.3.1. Coalescence . . . . . . . . . . . . . . . . . . . . . 10
4.3.2. DODAG Root Address Determination . . . . . . . . . . 10 4.3.2. DODAG Root Address Determination . . . . . . . . . . 11
5. The SRH 6LoRH Header . . . . . . . . . . . . . . . . . . . . 11 5. The SRH 6LoRH Header . . . . . . . . . . . . . . . . . . . . 12
5.1. Encoding . . . . . . . . . . . . . . . . . . . . . . . . 11 5.1. Encoding . . . . . . . . . . . . . . . . . . . . . . . . 12
5.2. SRH-6LoRH General Operation . . . . . . . . . . . . . . . 13 5.2. SRH-6LoRH General Operation . . . . . . . . . . . . . . . 13
5.2.1. Uncompressed SRH Operation . . . . . . . . . . . . . 13 5.2.1. Uncompressed SRH Operation . . . . . . . . . . . . . 13
5.2.2. 6LoRH-Compressed SRH Operation . . . . . . . . . . . 13 5.2.2. 6LoRH-Compressed SRH Operation . . . . . . . . . . . 14
5.2.3. Inner LOWPAN_IPHC Compression . . . . . . . . . . . . 14 5.2.3. Inner LOWPAN_IPHC Compression . . . . . . . . . . . . 14
5.3. The Design Point of Popping Entries . . . . . . . . . . . 14 5.3. The Design Point of Popping Entries . . . . . . . . . . . 15
5.4. Compression Reference for SRH-6LoRH header entries . . . 15 5.4. Compression Reference for SRH-6LoRH header entries . . . 16
5.5. Popping Headers . . . . . . . . . . . . . . . . . . . . . 16 5.5. Popping Headers . . . . . . . . . . . . . . . . . . . . . 17
5.6. Forwarding . . . . . . . . . . . . . . . . . . . . . . . 17 5.6. Forwarding . . . . . . . . . . . . . . . . . . . . . . . 17
6. The RPL Packet Information 6LoRH . . . . . . . . . . . . . . 17 6. The RPL Packet Information 6LoRH . . . . . . . . . . . . . . 18
6.1. Compressing the RPLInstanceID . . . . . . . . . . . . . . 19 6.1. Compressing the RPLInstanceID . . . . . . . . . . . . . . 19
6.2. Compressing the SenderRank . . . . . . . . . . . . . . . 19 6.2. Compressing the SenderRank . . . . . . . . . . . . . . . 20
6.3. The Overall RPI-6LoRH encoding . . . . . . . . . . . . . 20 6.3. The Overall RPI-6LoRH encoding . . . . . . . . . . . . . 20
7. The IP-in-IP 6LoRH Header . . . . . . . . . . . . . . . . . . 22 7. The IP-in-IP 6LoRH Header . . . . . . . . . . . . . . . . . . 23
8. Management Considerations . . . . . . . . . . . . . . . . . . 23 8. Management Considerations . . . . . . . . . . . . . . . . . . 24
9. Security Considerations . . . . . . . . . . . . . . . . . . . 24 9. Security Considerations . . . . . . . . . . . . . . . . . . . 25
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
10.1. Reserving Space in 6LoWPAN Dispatch Page 1 . . . . . . . 25 10.1. Reserving Space in 6LoWPAN Dispatch Page 1 . . . . . . . 25
10.2. New Critical 6LoWPAN Routing Header Type Registry . . . 25 10.2. New Critical 6LoWPAN Routing Header Type Registry . . . 26
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 25 10.3. New Elective 6LoWPAN Routing Header Type Registry . . . 26
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 26
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 26
12.1. Normative References . . . . . . . . . . . . . . . . . . 26 12.1. Normative References . . . . . . . . . . . . . . . . . . 26
12.2. Informative References . . . . . . . . . . . . . . . . . 27 12.2. Informative References . . . . . . . . . . . . . . . . . 28
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 28 Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 28
A.1. Examples Compressing The RPI . . . . . . . . . . . . . . 28 A.1. Examples Compressing The RPI . . . . . . . . . . . . . . 28
A.2. Example Of Downward Packet In Non-Storing Mode . . . . . 30 A.2. Example Of Downward Packet In Non-Storing Mode . . . . . 30
A.3. Example of SRH-6LoRH life-cycle . . . . . . . . . . . . . 31 A.3. Example of SRH-6LoRH life-cycle . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 33 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 34
1. Introduction 1. Introduction
The design of Low Power and Lossy Networks (LLNs) is generally The design of Low Power and Lossy Networks (LLNs) is generally
focused on saving energy, a very constrained resource in most cases. focused on saving energy, a very constrained resource in most cases.
The other constraints, such as the memory capacity and the duty The other constraints, such as the memory capacity and the duty
cycling of the LLN devices, derive from that primary concern. Energy cycling of the LLN devices, derive from that primary concern. Energy
is often available from primary batteries that are expected to last is often available from primary batteries that are expected to last
for years, or is scavenged from the environment in very limited for years, or is scavenged from the environment in very limited
quantities. Any protocol that is intended for use in LLNs must be quantities. Any protocol that is intended for use in LLNs must be
designed with the primary concern of saving energy as a strict designed with the primary concern of saving energy as a strict
requirement. requirement.
Controlling the amount of data transmission is one possible venue to Controlling the amount of data transmission is one possible venue to
save energy. In a number of LLN standards, the frame size is limited save energy. In a number of LLN standards, the frame size is limited
to much smaller values than the IPv6 maximum transmission unit (MTU) to much smaller values than the IPv6 maximum transmission unit (MTU)
of 1280 bytes. In particular, an LLN that relies on the classical 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 Physical Layer (PHY) of IEEE 802.15.4 [IEEE802154] is limited to 127
bytes per frame. The need to compress IPv6 packets over IEEE bytes per frame. The need to compress IPv6 packets over IEEE
802.15.4 led to the 6LoWPAN Header Compression [RFC6282] work 802.15.4 led to the "6LoWPAN Header Compression" [RFC6282] work
(6LoWPAN-HC). (6LoWPAN_HC).
Innovative Route-over techniques have been and are still being Innovative Route-over techniques have been and are still being
developed for routing inside a LLN. In a general fashion, such developed for routing inside a LLN. In a general fashion, such
techniques require additional information in the packet to provide techniques require additional information in the packet to provide
loop prevention and to indicate information such as flow loop prevention and to indicate information such as flow
identification, source routing information, etc. identification, source routing information, etc.
For reasons such as security and the capability to send ICMP errors 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 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 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 packet must be placed in an extra IP-in-IP encapsulation.
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, RFC 6554 and IPv6-in-IPv6
[I-D.ietf-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 This is the case when the additional routing information is inserted
may be compressed down to 2 octets in stateless compression and down by a router on the path of a packet, for instance the root of a mesh,
to 3 octets in stateful compression when context information must be as opposed to the source node, with the non-storing mode of the "IPv6
added. Routing Protocol for Low-Power and Lossy Networks" [RFC6550] (RPL).
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, RFC 6554 and IPv6-in-IPv6"
[I-D.ietf-roll-useofrplinfo] details different cases where IPv6
headers defined in the "RPL Option for Carrying RPL Information in
Data-Plane Datagrams" [RFC6553] and the "Routing Header for Source
Routes with RPL" [RFC6554], and IPv6-in-IPv6 encapsulation, are
inserted or removed from packets in a LLN environments operating RPL.
When using RFC 6282 [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
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 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 | | 0 | 1 | 1 | TF |NH | HLIM |CID|SAC| SAM | M |DAC| DAM |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
Figure 1: LOWPAN_IPHC base Encoding (RFC6282). Figure 1: LOWPAN_IPHC base Encoding (RFC6282).
The Stateless Compression of an IPv6 addresses can only happen if the The Stateless Compression of an IPv6 addresses can only happen if the
IPv6 address can de deduced from the MAC addresses, meaning that 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 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 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 (i.e., operated at Layer-3) network. A better compression, which
does not involve variable compressions depending on the hop in the does not involve variable compressions depending on the hop in the
mesh, can be achieved based on the fact that the outer encapsulation mesh, can be achieved based on the fact that the outer encapsulation
is usually between the source (or destination) of the inner packet is usually between the source (or destination) of the inner packet
and the root. Also, the inner IP header can only be compressed by and the root. Also, the inner IP header can only be compressed by
[RFC6282] if all the fields preceding it are also compressed. This RFC 6282 [RFC6282] if all the fields preceding it are also
specification makes the inner IP header the first header to be compressed. This specification makes the inner IP header the first
compressed by [RFC6282], and keeps the inner packet encoded the same header to be compressed by RFC 6282 [RFC6282], and keeps the inner
way whether it is encapsulated or not, thus preserving existing packet encoded the same way whether it is encapsulated or not, thus
implementations. preserving existing implementations.
As an example, the Routing Protocol for Low Power and Lossy Networks As an example, RPL [RFC6550] is designed to optimize the routing
[RFC6550] (RPL) is designed to optimize the routing operations in operations in constrained LLNs. As part of this optimization, RPL
constrained LLNs. As part of this optimization, RPL requires the requires the addition of RPL Packet Information (RPI) in every
addition of RPL Packet Information (RPI) in every packet, as defined packet, as defined in Section 11.2 of RFC 6550 [RFC6550].
in Section 11.2 of [RFC6550].
The RPL Option for Carrying RPL Information in Data-Plane Datagrams The "RPL Option for Carrying RPL Information in Data-Plane Datagrams"
[RFC6553] specification indicates how the RPI can be placed in a RPL [RFC6553] specification indicates how the RPI can be placed in a RPL
Option (RPL-OPT) that is placed in an IPv6 Hop-by-Hop header. Option (RPL-OPT) that is placed in an IPv6 Hop-by-Hop header.
This representation demands a total of 8 bytes, while in most cases 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 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 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 in packets entering the domain and be removed from packets that leave
the domain. In both cases, this operation implies an IP-in-IP the domain. In both cases, this operation implies an IP-in-IP
encapsulation. encapsulation.
Additionally, in the case of the Non-Storing Mode of Operation (MOP), Additionally, in the case of the Non-Storing Mode of Operation (MOP),
RPL requires a Source Routing Header (SRH) in all packets that are RPL requires a Source Routing Header (SRH) in all packets that are
routed down a RPL graph. for that purpose, the [IPv6 Routing Header routed down a RPL graph. for that purpose, the "IPv6 Routing Header
for Source Routes with RPL] (#RFC6554) specification defines the type for Source Routes with RPL" [RFC6554] specification defines the type
3 Routing Header for IPv6 (RH3). 3 Routing Header for IPv6 (RH3).
------+--------- ^ ------+--------- ^
| Internet | | Internet |
| | Native IPv6 | | Native IPv6
+-----+ | +-----+ |
| | Border Router (RPL Root) ^ | ^ | | Border Router (RPL Root) ^ | ^
| | | | | | | | | |
+-----+ | | | IPv6 in +-----+ | | | IPv6 in
| | | | IPv6 | | | | IPv6
o o o o | | | plus o o o o | | | plus
o o o o o o o o o | | | o o o o o o o o o | | | RPL SRH
o o o o o o o o o o | | | RPL SRH 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 v v v o o o o o o o o v v v
o o o o o o o o
LLN LLN
Figure 2: IP-in-IP Encapsulation within the LLN. Figure 2: IP-in-IP Encapsulation within the LLN.
With Non-Storing RPL, even if the source is a node in the same LLN, 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 the packet must first reach up the graph to the root so that the root
can insert the SRH to go down the graph. In any fashion, whether the can insert the SRH to go down the graph. In any fashion, whether the
packet was originated in a node in the LLN or outside the LLN, and 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 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- 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 routing operation also implies an IP-in-IP encapsulation at the root
in order to insert the SRH. in order to insert the SRH.
6TiSCH [I-D.ietf-6tisch-architecture] specifies the operation of IPv6 "The 6TiSCH Architecture" [I-D.ietf-6tisch-architecture] specifies
over the TimeSlotted Channel Hopping [RFC7554] (TSCH) mode of the operation of IPv6 over the "TimeSlotted Channel Hopping"
operation of IEEE 802.15.4. The architecture requires the use of [RFC7554] (TSCH) mode of operation of IEEE 802.15.4. The
both RPL and the 6lo adaptation layer over IEEE 802.15.4. Because it architecture requires the use of both RPL and the 6lo adaptation
inherits the constraints on frame size from the MAC layer, 6TiSCH layer over IEEE 802.15.4. Because it inherits the constraints on
cannot afford to allocate 8 bytes per packet on the RPI. Hence the frame size from the MAC layer, 6TiSCH cannot afford to allocate 8
requirement for 6LoWPAN header compression of the RPI. 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- An extensible compression technique is required that simplifies IP-
in-IP encapsulation when it is needed, and optimally compresses in-IP encapsulation when it is needed, and optimally compresses
existing routing artifacts found in RPL LLNs. existing routing artifacts found in RPL LLNs.
This specification extends the 6lo adaptation layer framework This specification extends the 6lo adaptation layer framework (RFC
([RFC4944],[RFC6282]) so as to carry routing information for route- 4944 [RFC4944] and RFC 6282 [RFC6282]) so as to carry routing
over networks based on RPL. The specification includes the formats information for route-over networks based on RPL. The specification
necessary for RPL and is extensible for additional formats. includes the formats necessary for RPL and is extensible for
additional formats.
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in RFC
[RFC2119]. 2119 [RFC2119].
The Terminology used in this document is consistent with and The Terminology used in this document is consistent with and
incorporates that described in `Terminology in Low power And Lossy incorporates that described in Terminology in Low power And Lossy
Networks' [RFC7102] and [RFC6550]. Networks [RFC7102] and RPL [RFC6550].
The terms Route-over and Mesh-under are defined in [RFC6775]. The terms Route-over and Mesh-under are defined in RFC 6775
[RFC6775].
Other terms in use in LLNs are found in [RFC7228]. Other terms in use in LLNs are found in "Terminology for Constrained-
Node Networks" [RFC7228].
The term "byte" is used in its now customary sense as a synonym for The term "byte" is used in its now customary sense as a synonym for
"octet". "octet".
3. Using the Page Dispatch 3. Using the Page Dispatch
The 6LoWPAN Paging Dispatch [I-D.ietf-6lo-paging-dispatch] The 6LoWPAN Paging Dispatch [I-D.ietf-6lo-paging-dispatch]
specification extends the 6lo adaptation layer framework ([RFC4944], specification extends the 6lo adaptation layer framework (RFC 4944
[RFC6282]) by introducing a concept of "context" in the 6LoWPAN [RFC4944] and RFC 6282 [RFC6282]) by introducing a concept of
parser, a context being identified by a Page number. The "context" in the 6LoWPAN parser, a context being identified by a Page
specification defines 16 Pages. number. The specification defines 16 Pages.
This draft operates within Page 1, which is indicated by a Dispatch This draft operates within Page 1, which is indicated by a Dispatch
Value of binary 11110001. Value of binary 11110001.
3.1. New Routing Header Dispatch (6LoRH) 3.1. New Routing Header Dispatch (6LoRH)
This specification introduces a new 6LoWPAN Routing Header (6LoRH) to This specification introduces a new 6LoWPAN Routing Header (6LoRH) to
carry IPv6 routing information. The 6LoRH may contain source routing carry IPv6 routing information. The 6LoRH may contain source routing
information such as a compressed form of SRH, as well as other sorts information such as a compressed form of SRH, as well as other sorts
of routing information such as the RPI and IP-in-IP encapsulation. of routing information such as the RPI and IP-in-IP encapsulation.
skipping to change at page 1, line 289 skipping to change at page 1, line 299
6LoRH is present. 6LoRH is present.
This specification uses the bit pattern 10xxxxxx in Page 1 for the This specification uses the bit pattern 10xxxxxx in Page 1 for the
new 6LoRH Dispatch. Section 4 describes how RPL artifacts in data new 6LoRH Dispatch. Section 4 describes how RPL artifacts in data
packets can be compressed as 6LoRH headers. packets can be compressed as 6LoRH headers.
3.2. Placement Of 6LoRH headers 3.2. Placement Of 6LoRH headers
3.2.1. Relative To Non-6LoRH Headers 3.2.1. Relative To Non-6LoRH Headers
Paging Dispatch is parsed and no subsequent Paging Dispatch has been In a zone of a packet where Page 1 is active (that is, once the Page
parsed, the parsing of the packet MUST follow this specification if 1 Paging Dispatch is parsed, and until another Paging Dispatch is
the 6LoRH Bit Pattern Section 3.1 is found. parsed as described in the 6LoWPAN Paging Dispatch specification
[I-D.ietf-6lo-paging-dispatch]), the parsing of the packet MUST
follow this specification if the 6LoRH Bit Pattern (see Section 3.1)
is found.
With this specification, the 6LoRH Dispatch is only defined in Page With this specification, the 6LoRH Dispatch is only defined in Page
context is active. context is active.
Because a 6LoRH header requires a Page 1 context, it MUST always be Because a 6LoRH header requires a Page 1 context, it MUST always be
placed after any Fragmentation Header and/or Mesh Header [RFC4944]. placed after any Fragmentation Header and/or Mesh Header as defined
in RFC 4944 [RFC4944].
A 6LoRH header MUST always be placed before the LOWPAN_IPHC as A 6LoRH header MUST always be placed before the LOWPAN_IPHC as
defined in 6LoWPAN Header Compression [RFC6282]. It is designed in defined in RFC 6282 [RFC6282]. It is designed in such a fashion that
such a fashion that placing or removing a header that is encoded with placing or removing a header that is encoded with 6LoRH does not
6LoRH does not modify the part of the packet that is encoded with modify the part of the packet that is encoded with LOWPAN_IPHC,
LoWPAN_IPHC, whether there is an IP-in-IP encapsulation or not. For whether there is an IP-in-IP encapsulation or not. For instance, the
instance, the final destination of the packet is always the one in final destination of the packet is always the one in the LOWPAN_IPHC
the LOWPAN_IPHC whether there is a Routing Header or not. whether there is a Routing Header or not.
3.2.2. Relative To Other 6LoRH Headers 3.2.2. Relative To Other 6LoRH Headers
IPv6 [RFC2460] defines chains of headers that are introduced by an The "Internet Protocol, Version 6 (IPv6) Specification" [RFC2460]
IPv6 header and terminated by either another IPv6 header (IP-in-IP) defines chains of headers that are introduced by an IPv6 header and
or an Upper Layer Protocol ULP) header. When an outer header is terminated by either another IPv6 header (IP-in-IP) or an Upper Layer
stripped from the packet, the whole chain goes with it. When one or Protocol (ULP) header. When an outer header is stripped from the
more header(s) are inserted by an intermediate router, that router packet, the whole chain goes with it. When one or more header(s) are
normally chains the headers and encapsulates the result in IP-in-IP. inserted by an intermediate router, that router normally chains the
headers and encapsulates the result in IP-in-IP.
With this specification, the chains of headers MUST be compressed in With this specification, the chains of headers MUST be compressed in
the same order as they appear in the uncompressed form of the packet. the same order as they appear in the uncompressed form of the packet.
This means that if there is more than one nested IP-in-IP This means that if there is more than one nested IP-in-IP
encapsulations, the first IP-in-IP encapsulation, with all its chain encapsulations, the first IP-in-IP encapsulation, with all its chain
of headers, is encoded first in the compressed form. of headers, is encoded first in the compressed form.
In the compressed form of a packet that has SRH or HbH headers after In the compressed form of a packet that has a Source Route or a Hop-
the inner IPv6 header (e.g. if there is no IP-in-IP encapsulation), by-Hop (HbH) Options Header [RFC2460] after the inner IPv6 header
these headers are placed in the 6LoRH form before the 6LOWPAN-IPHC (e.g. if there is no IP-in-IP encapsulation), these headers are
that represents the IPv6 header Section 3.2.1. If this packet gets placed in the 6LoRH form before the 6LOWPAN_IPHC that represents the
encapsulated and some other SRH or HbH headers are added as part of IPv6 header (see Section 3.2.1). If this packet gets encapsulated
the encapsulation, placing the 6LoRH headers next to one another may and some other SRH or HbH Options Headers are added as part of the
encapsulation, placing the 6LoRH headers next to one another may
present an ambiguity on which header belong to which chain in the present an ambiguity on which header belong to which chain in the
uncompressed form. uncompressed form.
In order to disambiguate the headers that follow the inner IPv6 In order to disambiguate the headers that follow the inner IPv6
header in the uncompressed form from the headers that follow the header in the uncompressed form from the headers that follow the
outer IP-in-IP header, it is REQUIRED that the compressed IP-in-IP outer IP-in-IP header, it is REQUIRED that the compressed IP-in-IP
header is placed last in the encoded chain. This means that the header is placed last in the encoded chain. This means that the
6LoRH headers that are found after the last compressed IP-in-IP 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 header are to be inserted after the IPv6 header that is encoded with
the 6LOWPAN-IPHC when decompressing the packet. the 6LOWPAN_IPHC when decompressing the packet.
With regards to the relative placement of the SRH and the RPI in the With regards to the relative placement of the SRH and the RPI in the
compressed form, it is a design point for this specification that the compressed form, it is a design point for this specification that the
SRH entries are consumed as the packet progresses down the LLN SRH entries are consumed as the packet progresses down the LLN (see
Section 5.3. In order to make this operation simpler in the Section 5.3). In order to make this operation simpler in the
compressed form, it is REQUIRED that the in the compressed form, the compressed form, it is REQUIRED that in the compressed form, the
addresses along the source route path are encoded in the order of the addresses along the source route path are encoded in the order of the
path, and that the compressed SRH are placed before the compressed path, and that the compressed SRH are placed before the compressed
RPI. RPI.
4. 6LoWPAN Routing Header General Format 4. 6LoWPAN Routing Header General Format
The 6LoRH uses the Dispatch Value Bit Pattern of 10xxxxxx in Page 1. The 6LoRH uses the Dispatch Value Bit Pattern of 10xxxxxx in Page 1.
The Dispatch Value Bit Pattern is split in two forms of 6LoRH: The Dispatch Value Bit Pattern is split in two forms of 6LoRH:
Elective (6LoRHE) that may skipped if not understood Elective (6LoRHE) that may skipped if not understood
Critical (6LoRHC) that may not be ignored Critical (6LoRHC) that may not be ignored
for each form, a Type field is used to encode the type of 6LoRH. For each form, a Type field is used to encode the type of 6LoRH.
Note that there is a different registry for the Type field of each Note that there is a different registry for the Type field of each
form of 6LoRH, This means that that a value for the Type that is form of 6LoRH.
defined for one form of 6LoRH may be redefined in the future for the
other form. This means that a value for the Type that is defined for one form of
6LoRH may be redefined in the future for the other form.
4.1. Elective Format 4.1. Elective Format
The 6LoRHE uses the Dispatch Value Bit Pattern of 101xxxxx. A 6LoRHE The 6LoRHE uses the Dispatch Value Bit Pattern of 101xxxxx. A 6LoRHE
may be ignored and skipped in parsing. If it is ignored, the 6LoRHE may be ignored and skipped in parsing. If it is ignored, the 6LoRHE
is forwarded with no change inside the LLN. is forwarded with no change inside the LLN.
0 1 0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+
skipping to change at page 1, line 418 skipping to change at page 1, line 436
the TSE depends on the Type field that follows. For instance, the TSE depends on the Type field that follows. For instance,
it may be used to transport control bits, the number of it may be used to transport control bits, the number of
elements in an array, or the length of the remainder of the elements in an array, or the length of the remainder of the
6LoRHC expressed in a unit other than bytes. 6LoRHC expressed in a unit other than bytes.
Type: Type of the 6LoRHC Type: Type of the 6LoRHC
4.3. Compressing Addresses 4.3. Compressing Addresses
The general technique used in this draft to compress an address is The general technique used in this draft to compress an address is
first to determine a reference that as a long prefix match with this first to determine a reference that has a long prefix match with this
address, and then elide that matching piece. In order to reconstruct address, and then elide that matching piece. In order to reconstruct
the compress address, the receiving node will perform the process of the compressed address, the receiving node will perform the process
coalescence described in section Section 4.3.1. of coalescence described in Section 4.3.1.
One possible reference is the root of the RPL DODAG that is being One possible reference is the root of the RPL DODAG that is being
traversed. It is used by 6LoRH as the reference to compress an outer traversed. It is used by 6LoRH as the reference to compress an outer
IP header, in case of an IP-in-IP encapsulation. If the root is the IP header, in case of an IP-in-IP encapsulation. If the root is the
source of the packet, this technique allows to fully elide the source source of the packet, this technique allows to fully elide the source
address in the compressed form of the IP header. If the root is not address in the compressed form of the IP header. If the root is not
the encapsulator, then the encapsulator address may still be the encapsulator, then the encapsulator address may still be
compressed using the root as reference. How the address of the root compressed using the root as reference. How the address of the root
is determined is discussed in Section 4.3.2. is determined is discussed in Section 4.3.2.
skipping to change at page 1, line 469 skipping to change at page 1, line 487
Figure 5: Coalescing addresses. Figure 5: Coalescing addresses.
4.3.2. DODAG Root Address Determination 4.3.2. DODAG Root Address Determination
Stateful Address compression requires that some state is installed in Stateful Address compression requires that some state is installed in
the devices to store the compression information that is elided from the devices to store the compression information that is elided from
the packet. That state is stored in an abstract context table and the packet. That state is stored in an abstract context table and
some form of index is found in the packet to obtain the compression some form of index is found in the packet to obtain the compression
information from the context table. information from the context table.
With [RFC6282], the state is provided to the stack by the 6LoWPAN With RFC 6282 [RFC6282], the state is provided to the stack by the
Neighbor Discovery Protocol (NDP) [RFC6775]. NDP exchanges the "6LoWPAN Neighbor Discovery Protocol (NDP)" [RFC6775]. NDP exchanges
context through 6LoWPAN Context Option in Router Advertisement (RA) the context through 6LoWPAN Context Option in Router Advertisement
messages. In the compressed form of the packet, the context can be (RA) messages. In the compressed form of the packet, the context can
signaled in a Context Identifier Extension. be signaled in a Context Identifier Extension.
With this specification, the compression information is provided to With this specification, the compression information is provided to
the stack by RPL, and RPL exchanges it through the DODAGID field in the stack by RPL, and RPL exchanges it through the DODAGID field in
the DAG Information Object (DIO) messages, as described in more the DAG Information Object (DIO) messages, as described in more
details below. In the compressed form of the packet, the context can detail below. In the compressed form of the packet, the context can
be signaled in by the RPLInstanceID in the RPI. be signaled in by the RPLInstanceID in the RPI.
With RPL [RFC6550], the address of the DODAG root is known from the With RPL [RFC6550], the address of the DODAG root is known from the
DODAGID field of the DIO messages. For a Global Instance, the DODAGID field of the DIO messages. For a Global Instance, the
RPLInstanceID that is present in the RPI is enough information to RPLInstanceID that is present in the RPI is enough information to
identify the DODAG that this node participates to and its associated identify the DODAG that this node participates to and its associated
root. But for a Local Instance, the address of the root MUST be root. But for a Local Instance, the address of the root MUST be
explicit, either in some device configuration or signaled in the explicit, either in some device configuration or signaled in the
packet, as the source or the destination address, respectively. packet, as the source or the destination address, respectively.
When implicit, the address of the DODAG root MUST be determined as When implicit, the address of the DODAG root MUST be determined as
follows: follows:
If the whole network is a single DODAG then the root can be well- If the whole network is a single DODAG then the root can be well-
known and does not need to be signaled in the packets. But since RPL known and does not need to be signaled in the packets. But since RPL
does not expose that property, it can only be known by a does not expose that property, it can only be known by a
configuration applied to all nodes. configuration applied to all nodes.
Else, the router that encapsulates the packet and compresses it with Else, the router that encapsulates the packet and compresses it with
this specification MUST also place an RPI in the packet as prescribed this specification MUST also place an RPI in the packet as prescribed
by [RFC6550] to enable the identification of the DODAG. The RPI must by RPL to enable the identification of the DODAG. The RPI must be
be present even in the case when the router also places an SRH header present even in the case when the router also places an SRH header in
in the packet. the packet.
It is expected that the RPL implementation maintains an abstract It is expected that the RPL implementation maintains an abstract
context table, indexed by Global RPLInstanceID, that provides the context table, indexed by Global RPLInstanceID, that provides the
address of the root of the DODAG that this nodes participates to for address of the root of the DODAG that this nodes participates to for
that particular RPL Instance. that particular RPL Instance.
5. The SRH 6LoRH Header 5. The SRH 6LoRH Header
5.1. Encoding 5.1. Encoding
A Source Routing Header 6LoRH (SRH-6LoRH) header provides a A Source Routing Header 6LoRH (SRH-6LoRH) header provides a
compressed form for the SRH, as defined in [RFC6554] for use by RPL compressed form for the SRH, as defined in RFC 6554 [RFC6554] for use
routers. by RPL routers.
One or more SRH-6LoRH header(s) MAY be placed in a 6LoWPAN packet. One or more SRH-6LoRH header(s) MAY be placed in a 6LoWPAN packet.
If a non-RPL router receives a packet with a SRH-6LoRH header, there If a non-RPL router receives a packet with a SRH-6LoRH header, there
was a routing or a configuration error (see Section 8). was a routing or a configuration error (see Section 8).
The desired reaction for the non-RPL router is to drop the packet as The desired reaction for the non-RPL router is to drop the packet as
opposed to skip the header and forward the packet. opposed to skip the header and forward the packet.
The Dispatch Value Bit Pattern for the SRH-6LoRH header indicates The Dispatch Value Bit Pattern for the SRH-6LoRH header indicates
skipping to change at page 1, line 542 skipping to change at page 1, line 560
|1|0|0| Size |6LoRH Type 0..4| Hop1 | Hop2 | | HopN | |1|0|0| Size |6LoRH Type 0..4| Hop1 | Hop2 | | HopN |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- -+- -+ ... +- -+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- -+- -+ ... +- -+
Where N = Size + 1 Where N = Size + 1
Figure 6: The SRH-6LoRH. Figure 6: The SRH-6LoRH.
The 6LoRH Type of a SRH-6LoRH header indicates the compression level The 6LoRH Type of a SRH-6LoRH header indicates the compression level
used for that header. used for that header.
It results that all addresses in a given SRH-6LoRH header MUST be The fields following the 6LoRH Type are compressed addresses
compressed in an identical fashion, down to using the identical indicating the consecutive hops, and are ordered from the first to
number of bytes per address. In order to get different degrees of the last hop.
compression, multiple consecutive SRH-6LoRH headers MUST be used.
All the addresses in a given SRH-6LoRH header MUST be compressed in
an identical fashion, so the Length of the compressed for is the same
for all.
In order to get different degrees of compression, multiple
consecutive SRH-6LoRH headers MUST be used.
Type 0 means that the address is compressed down to one byte, whereas Type 0 means that the address is compressed down to one byte, whereas
Type 4 means that the address is provided in full in the SRH-6LoRH Type 4 means that the address is provided in full in the SRH-6LoRH
with no compression. The complete list of Types of SRH-6LoRH and the with no compression. The complete list of Types of SRH-6LoRH and the
corresponding compression level are provided in Figure 7: corresponding compression level are provided in Figure 7:
+-----------+----------------------+ +-----------+----------------------+
| 6LoRH | Length of compressed | | 6LoRH | Length of compressed |
| Type | IPv6 address (bytes) | | Type | IPv6 address (bytes) |
+-----------+----------------------+ +-----------+----------------------+
skipping to change at page 1, line 608 skipping to change at page 1, line 632
SRH-6LoRH upon reception of a packet effectively consumes that entry SRH-6LoRH upon reception of a packet effectively consumes that entry
when forwarding. This means that the size of a compressed source- when forwarding. This means that the size of a compressed source-
routed packet decreases as the packet progresses along its path and routed packet decreases as the packet progresses along its path and
that the routing information is lost along the way. This also means that the routing information is lost along the way. This also means
that an SRH encoded with 6LoRH is not recoverable and cannot be that an SRH encoded with 6LoRH is not recoverable and cannot be
protected. protected.
When compressed with this specification, all the remaining hops MUST When compressed with this specification, all the remaining hops MUST
be encoded in order in one or more consecutive SRH-6LoRH headers. be encoded in order in one or more consecutive SRH-6LoRH headers.
Whether or not there is a SRH-6LoRH header present, the address of Whether or not there is a SRH-6LoRH header present, the address of
the final destination is indicated in the LoWPAN_IPHC at all times the final destination is indicated in the LOWPAN_IPHC at all times
along the path. Examples of this are provided in Appendix A. along the path. Examples of this are provided in Appendix A.
The current destination (termination of the current segment) for a The current destination (termination of the current segment) for a
compressed source-routed packet is indicated in the first entry of compressed source-routed packet is indicated in the first entry of
the first SRH-6LoRH. In strict source-routing, that entry MUST match the first SRH-6LoRH. In strict source-routing, that entry MUST match
an address of the router that receives the packet. an address of the router that receives the packet.
The last entry in the last SRH-6LoRH is the last router on the way to The last entry in the last SRH-6LoRH is the last router on the way to
the final destination in the LLN. This router can be the final the final destination in the LLN. This router can be the final
destination if it is found desirable to carry a whole IP-in-IP destination if it is found desirable to carry a whole IP-in-IP
skipping to change at page 1, line 631 skipping to change at page 1, line 655
host, and advertising the host as an external route to RPL. host, and advertising the host as an external route to RPL.
If the SRH-6LoRH header is contained in an IP-in-IP encapsulation, If the SRH-6LoRH header is contained in an IP-in-IP encapsulation,
the last router removes the whole chain of headers. Otherwise, it the last router removes the whole chain of headers. Otherwise, it
removes the SRH-6LoRH header only. removes the SRH-6LoRH header only.
5.2.3. Inner LOWPAN_IPHC Compression 5.2.3. Inner LOWPAN_IPHC Compression
6LoWPAN ND [RFC6282] is designed to support more than one IPv6 6LoWPAN ND [RFC6282] is designed to support more than one IPv6
address per node and per Interface Identifier (IID), an IID being address per node and per Interface Identifier (IID), an IID being
typically derived from a MAC address to optimize the LOWPAN-IPHC typically derived from a MAC address to optimize the LOWPAN_IPHC
compression. compression.
Link local addresses are compressed with stateless address Link local addresses are compressed with stateless address
compression (S/DAC=0). The other addresses are derived from compression (S/DAC=0). The other addresses are derived from
different prefixes and they can be compressed with stateful address different prefixes and they can be compressed with stateful address
compression based on a context (S/DAC=1). compression based on a context (S/DAC=1).
But stateless compression is only defined for the specific link-local But stateless compression is only defined for the specific link-local
prefix as opposed to the prefix in an encapsulating header. And with prefix as opposed to the prefix in an encapsulating header. And with
stateful compression, the compression reference is found in a stateful compression, the compression reference is found in a
skipping to change at page 1, line 686 skipping to change at page 1, line 710
RH may have been used to stay away from the shortest path for some RH may have been used to stay away from the shortest path for some
reason that is only valid on the way in (segment routing). reason that is only valid on the way in (segment routing).
There is no use of reversing a RH in the present RPL There is no use of reversing a RH in the present RPL
specifications. specifications.
P2P RPL reverses a path that was learned reactively, as a part of P2P RPL reverses a path that was learned reactively, as a part of
the protocol operation, which is probably a cleaner way than a the protocol operation, which is probably a cleaner way than a
reversed echo on the data path. reversed echo on the data path.
Reversing a header is discouraged by [RFC2460] for RH0 unless it Reversing a header is discouraged by RFC 2460 [RFC2460] for RH0
is authenticated, which requires an Authentication Header (AH). unless it is authenticated, which requires an Authentication
There is no definition of an AH operation for SRH, and there is no Header (AH). There is no definition of an AH operation for SRH,
indication that the need exists in LLNs. and there is no indication that the need exists in LLNs.
It is noted that AH does not protect the RH on the way. AH is a It is noted that AH does not protect the RH on the way. AH is a
validation at the receiver with the sole value of enabling the validation at the receiver with the sole value of enabling the
receiver to reversing it. receiver to reversing it.
A RPL domain is usually protected by L2 security and that secures A RPL domain is usually protected by L2 security and that secures
both RPL itself and the RH in the packets, at every hop. This is both RPL itself and the RH in the packets, at every hop. This is
a better security than that provided by AH. a better security than that provided by AH.
In summary, the benefit of saving energy and lowering the chances of In summary, the benefit of saving energy and lowering the chances of
skipping to change at page 1, line 717 skipping to change at page 1, line 741
identifies an address that is used as reference for the compression. identifies an address that is used as reference for the compression.
With this specification, the Compression Reference for the first With this specification, the Compression Reference for the first
address found in an SRH header is the source of the IPv6 packet, and address found in an SRH header is the source of the IPv6 packet, and
then the reference for each subsequent entry is the address of its then the reference for each subsequent entry is the address of its
predecessor once it is uncompressed. predecessor once it is uncompressed.
With RPL [RFC6550], an SRH header may only be present in Non-Storing With RPL [RFC6550], an SRH header may only be present in Non-Storing
mode, and it may only be placed in the packet by the root of the mode, and it may only be placed in the packet by the root of the
DODAG, which must be the source of the resulting IPv6 packet DODAG, which must be the source of the resulting IPv6 packet
[RFC2460]. In this case, the address used as Compression Reference [RFC2460]. In this case, the address used as Compression Reference
is that the address of the root, and it can be implicit when the is the address of the root.
address of the root is.
The Compression Reference MUST be determined as follows: The Compression Reference MUST be determined as follows:
The reference address may be obtained by configuration. The The reference address may be obtained by configuration. The
configuration may indicate either the address in full, or the configuration may indicate either the address in full, or the
identifier of a 6LoWPAN Context that carries the address [RFC6775], identifier of a 6LoWPAN Context that carries the address [RFC6775],
for instance one of the 16 Context Identifiers used in LOWPAN-IPHC for instance one of the 16 Context Identifiers used in LOWPAN_IPHC
[RFC6282]. [RFC6282].
Else, and if there is no IP-in-IP encapsulation, the source address Else, and if there is no IP-in-IP encapsulation, the source address
in the IPv6 header that is compressed with LOWPAN-IPHC is the in the IPv6 header that is compressed with LOWPAN_IPHC is the
reference for the compression. reference for the compression.
Else, and if the IP-in-IP compression specified in this document is Else, and if the IP-in-IP compression specified in this document is
used and the Encapsulator Address is provided, then the Encapsulator used and the Encapsulator Address is provided, then the Encapsulator
Address is the reference. Address is the reference.
Else, meaning that the IP-in-IP compression specified in this
document is used and the encapsulator is implicitly the root, the
address of the root is the reference.
5.5. Popping Headers 5.5. Popping Headers
Upon reception, the router checks whether the address in the first Upon reception, the router checks whether the address in the first
entry of the first SRH-6LoRH one of its own addresses. In that case, entry of the first SRH-6LoRH one of its own addresses. In that case,
router MUST consume that entry before forwarding, which is an action router MUST consume that entry before forwarding, which is an action
of popping from a stack, where the stack is effectively the sequence of popping from a stack, where the stack is effectively the sequence
of entries in consecutive SRH-6LoRH headers. of entries in consecutive SRH-6LoRH headers.
Popping an entry of an SRH-6LoRH header is a recursive action Popping an entry of an SRH-6LoRH header is a recursive action
performed as follows: performed as follows:
skipping to change at page 1, line 768 skipping to change at page 1, line 794
value, meaning a same or lesser compression yielding same or larger value, meaning a same or lesser compression yielding same or larger
compressed forms, then the SRH-6LoRH is removed. compressed forms, then the SRH-6LoRH is removed.
Else, the first entry of the next SRH-6LoRH is popped from the next Else, the first entry of the next SRH-6LoRH is popped from the next
SRH-6LoRH and coalesced with the first entry of this SRH-6LoRH. SRH-6LoRH and coalesced with the first entry of this SRH-6LoRH.
At the end of the process, if there is no more SRH-6LoRH in the At the end of the process, if there is no more SRH-6LoRH in the
packet, then the processing node is the last router along the source packet, then the processing node is the last router along the source
route path. route path.
An example of this operation is provided in Appendix A.3.
5.6. Forwarding 5.6. Forwarding
When receiving a packet with a SRH-6LoRH, a router determines the When receiving a packet with a SRH-6LoRH, a router determines the
IPv6 address of the current segment endpoint. IPv6 address of the current segment endpoint.
If strict source routing is enforced and this router is not the If strict source routing is enforced and this router is not the
segment endpoint for the packet then this router MUST drop the segment endpoint for the packet then this router MUST drop the
packet. packet.
If this router is the current segment endpoint, then the router pops If this router is the current segment endpoint, then the router pops
skipping to change at page 1, line 800 skipping to change at page 1, line 828
Section 4.3.1. Section 4.3.1.
The router then coalesces the Compression Reference with the first The router then coalesces the Compression Reference with the first
entry of the first SRH-6LoRH header as discussed in Section 5.4. If entry of the first SRH-6LoRH header as discussed in Section 5.4. If
the type of the SRH-6LoRH header is type 4 then the coalescence is a the type of the SRH-6LoRH header is type 4 then the coalescence is a
full override. full override.
Since the Compression Reference is an uncompressed address, the Since the Compression Reference is an uncompressed address, the
coalesced IPv6 address is also expressed in the full 128bits. coalesced IPv6 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 6. The RPL Packet Information 6LoRH
[RFC6550], Section 11.2, specifies the RPL Packet Information (RPI) RPL [RFC6550], Section 11.2, specifies the RPL Packet Information
as a set of fields that are placed by RPL routers in IP packets to (RPI) as a set of fields that are placed by RPL routers in IP packets
identify the RPL Instance, detect anomalies and trigger corrective to identify the RPL Instance, detect anomalies and trigger corrective
actions. actions.
In particular, the SenderRank, which is the scalar metric computed by In particular, the SenderRank, which is the scalar metric computed by
a specialized Objective Function such as [RFC6552], indicates the a specialized Objective Function such as described in RFC 6552
Rank of the sender and is modified at each hop. The SenderRank field [RFC6552], indicates the Rank of the sender and is modified at each
is used to validate that the packet progresses in the expected hop. The SenderRank field is used to validate that the packet
direction, either upwards or downwards, along the DODAG. progresses in the expected direction, either upwards or downwards,
along the DODAG.
RPL defines the RPL Option for Carrying RPL Information in Data-Plane RPL defines the "RPL Option for Carrying RPL Information in Data-
Datagrams [RFC6553] to transport the RPI, which is carried in an IPv6 Plane Datagrams" [RFC6553] to transport the RPI, which is carried in
Hop-by-Hop Options Header [RFC2460], typically consuming eight bytes an IPv6 Hop-by-Hop Options Header [RFC2460], typically consuming
per packet. eight bytes per packet.
With [RFC6553], the RPL option is encoded as six octets, which must With RFC 6553 [RFC6553], the RPL option is encoded as six octets,
be placed in a Hop-by-Hop header that consumes two additional octets which must be placed in a Hop-by-Hop header that consumes two
for a total of eight octets. To limit the header's range to just the additional octets for a total of eight octets. To limit the header's
RPL domain, the Hop-by-Hop header must be added to (or removed from) range to just the RPL domain, the Hop-by-Hop header must be added to
packets that cross the border of the RPL domain. (or removed from) packets that cross the border of the RPL domain.
The 8-byte overhead is detrimental to LLN operation, in particular The 8-byte overhead is detrimental to LLN operation, in particular
with regards to bandwidth and battery constraints. These bytes may with regards to bandwidth and battery constraints. These bytes may
cause a containing frame to grow above maximum frame size, leading to cause a containing frame to grow above maximum frame size, leading to
Layer 2 or 6LoWPAN [RFC4944] fragmentation, which in turn leads to Layer 2 or 6LoWPAN [RFC4944] fragmentation, which in turn leads to
even more energy expenditure and issues discussed in LLN Fragment even more energy expenditure and issues discussed in "LLN Fragment
Forwarding and Recovery [I-D.thubert-6lo-forwarding-fragments]. Forwarding and Recovery" [I-D.thubert-6lo-forwarding-fragments].
An additional overhead comes from the need, in certain cases, to add 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 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 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. 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 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 stripped from the Hop-by-Hop header to be routed outside the RPL
domain. domain.
For that reason, this specification defines an IP-in-IP-6LoRH header 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 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 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 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 inserted the IP-in-IP-6LoRH header then this situation alone does not
mandate an IP-in-IP-6LoRH header. mandate an IP-in-IP-6LoRH header.
Note: A typical packet in RPL non-storing mode going down the RPL Note: it was found that some implementations omit the RPI for packets
graph requires an IP-in-IP encapsulation of the SRH, whereas the RPI going down the RPL graph in Non-Storing Mode, even though RPL
is usually (and quite illegally) omitted. With this specification, indicates that the RPI should be placed in the packet. With this
the RPI is important to indicate the RPLInstanceID so the RPI should specification, the RPI is important to indicate the RPLInstanceID so
not be omitted. To impact of placing an IP-in-IP encapsulation and the RPI should not be omitted.
an RPI in the packet, 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 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 IP-in-IP-6LoRH header. In that case, the source and destination of
the packet are specified by the LOWPAN_IPHC. the packet are specified by the LOWPAN_IPHC.
As with [RFC6553], the fields in the RPI include an 'O', an 'R', and As with RFC 6553 [RFC6553], the fields in the RPI include an 'O', an
an 'F' bit, an 8-bit RPLInstanceID (with some internal structure), 'R', and an 'F' bit, an 8-bit RPLInstanceID (with some internal
and a 16-bit SenderRank. structure), and a 16-bit SenderRank.
The remainder of this section defines the RPI-6LoRH header, which is The remainder of this section defines the RPI-6LoRH header, which is
a Critical 6LoWPAN Routing Header that is designed to transport the a Critical 6LoWPAN Routing Header that is designed to transport the
RPI in 6LoWPAN LLNs. RPI in 6LoWPAN LLNs.
6.1. Compressing the RPLInstanceID 6.1. Compressing the RPLInstanceID
RPL Instances are discussed in [RFC6550], Section 5. A number of RPL Instances are discussed in Section 5 of the RPL specification
simple use cases do not require more than one RPL Instance, and in [RFC6550]. A number of simple use cases do not require more than one
such cases, the RPL Instance is expected to be the Global Instance 0. RPL Instance, and in such cases, the RPL Instance is expected to be
A global RPLInstanceID is encoded in a RPLInstanceID field as the Global Instance 0. A global RPLInstanceID is encoded in a
follows: RPLInstanceID field as follows:
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|0| ID | Global RPLInstanceID in 0..127 |0| ID | Global RPLInstanceID in 0..127
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
Figure 8: RPLInstanceID Field Format for Global Instances. Figure 8: RPLInstanceID Field Format for Global Instances.
For the particular case of the Global Instance 0, the RPLInstanceID For the particular case of the Global Instance 0, the RPLInstanceID
field is all zeros. This specification allows to elide a field is all zeros. This specification allows to elide a
RPLInstanceID field that is all zeros, and defines a I flag that, RPLInstanceID field that is all zeros, and defines a I flag that,
when set, signals that the field is elided. when set, signals that the field is elided.
6.2. Compressing the SenderRank 6.2. Compressing the SenderRank
The SenderRank is the result of the DAGRank operation on the rank of The SenderRank is the result of the DAGRank operation on the rank of
the sender; here the DAGRank operation is defined in [RFC6550], the sender; here the DAGRank operation is defined in Section 3.5.1 of
Section 3.5.1, as: the RPL specification [RFC6550] as:
DAGRank(rank) = floor(rank/MinHopRankIncrease) DAGRank(rank) = floor(rank/MinHopRankIncrease)
If MinHopRankIncrease is set to a multiple of 256, the least If MinHopRankIncrease is set to a multiple of 256, the least
significant 8 bits of the SenderRank will be all zeroes; by eliding significant 8 bits of the SenderRank will be all zeroes; by eliding
those, the SenderRank can be compressed into a single byte. This those, the SenderRank can be compressed into a single byte. This
idea is used in [RFC6550] by defining DEFAULT_MIN_HOP_RANK_INCREASE idea is used in RFC 6550 [RFC6550] by defining
as 256 and in [RFC6552] that defaults MinHopRankIncrease to DEFAULT_MIN_HOP_RANK_INCREASE as 256 and in RFC 6552 [RFC6552] that
DEFAULT_MIN_HOP_RANK_INCREASE. defaults MinHopRankIncrease to DEFAULT_MIN_HOP_RANK_INCREASE.
This specification allows to encode the SenderRank as either one or 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 two bytes, and defines a K flag that, when set, signals that a single
byte is used. byte is used.
6.3. The Overall RPI-6LoRH encoding 6.3. The Overall RPI-6LoRH encoding
The RPI-6LoRH header provides a compressed form for the RPL RPI. 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 Routers that need to forward a packet with a RPI-6LoRH header are
expected to be RPL routers that support this specification. expected to be RPL routers that support this specification.
skipping to change at page 1, line 949 skipping to change at page 1, line 974
described hereafter. described hereafter.
0 1 2 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 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 | |1|0|0|O|R|F|I|K| 6LoRH Type=5 | Compressed fields |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... -+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... -+-+-+
Figure 9: The Generic RPI-6LoRH Format. Figure 9: The Generic RPI-6LoRH Format.
O, R, and F bits: The O, R, and F bits are defined in [RFC6550], O, R, and F bits: The O, R, and F bits are defined in section 11.2
section 11.2. of RFC 6550 [RFC6550].
I flag: If it is set, the RPLInstanceID is elided and the I flag: If it is set, the RPLInstanceID is elided and the
RPLInstanceID is the Global RPLInstanceID 0. If it is not set, RPLInstanceID is the Global RPLInstanceID 0. If it is not set,
the octet immediately following the type field contains the the octet immediately following the type field contains the
RPLInstanceID as specified in [RFC6550], section 5.1. RPLInstanceID as specified in section 5.1 of RFC 6550
[RFC6550],.
K flag: If it is set, the SenderRank is compressed into one octet, K flag: If it is set, the SenderRank is compressed into one octet,
with the least significant octet elided. If it is not set, the with the least significant octet elided. If it is not set, the
SenderRank, is fully inlined as two octets. SenderRank, is fully inlined as two octets.
In Figure 10, the RPLInstanceID is the Global RPLInstanceID 0, and In Figure 10, the RPLInstanceID is the Global RPLInstanceID 0, and
the MinHopRankIncrease is a multiple of 256 so the least significant the MinHopRankIncrease is a multiple of 256 so the least significant
byte is all zeros and can be elided: byte is all zeros and can be elided:
0 1 2 0 1 2
skipping to change at page 1, line 1046 skipping to change at page 1, line 1072
0 1 2 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 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 | |1|0|1| Length | 6LoRH Type 6 | Hop Limit | Encaps. Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+
Figure 14: The IP-in-IP-6LoRH. Figure 14: The IP-in-IP-6LoRH.
The Length of an IP-in-IP-6LoRH header is expressed in bytes and MUST 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 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 each hop. When the HL reaches 0, the packet is dropped per RFC 2460
[RFC2460]. [RFC2460].
If the Length of an IP-in-IP-6LoRH header is exactly 1, then the 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 Encapsulator Address is elided, which means that the Encapsulator is
a well-known router, for instance the root in a RPL graph. a well-known router, for instance the root in a RPL graph.
The most efficient compression of an IP-in-IP encapsulation that can The most efficient compression of an IP-in-IP encapsulation that can
be achieved with this specification is obtained when an endpoint of be achieved with this specification is obtained when an endpoint of
the packet is the root of the RPL DODAG associated to the RPL the packet is the root of the RPL DODAG associated to the RPL
Instance that is used to forward the packet, and the root address is Instance that is used to forward the packet, and the root address is
skipping to change at page 1, line 1071 skipping to change at page 1, line 1097
Encapsulator Address is placed in a compressed form after the Hop Encapsulator Address is placed in a compressed form after the Hop
Limit field. The value of the Length indicates which compression is Limit field. The value of the Length indicates which compression is
performed on the Encapsulator Address. For instance, a Length of 3 performed on the Encapsulator Address. For instance, a Length of 3
indicates that the Encapsulator Address is compressed to 2 bytes. indicates that the Encapsulator Address is compressed to 2 bytes.
The reference for the compression is the address of the root of the 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 DODAG. The way the address of the root is determined is discussed in
Section 4.3.2. Section 4.3.2.
With RPL, the destination address in the IP-in-IP header is With RPL, the destination address in the IP-in-IP header is
implicitly the root in the RPL graph for packets going upwards, and, implicitly the root in the RPL graph for packets going upwards, and,
in storing mode, it is the destination address in the IPHC for in storing mode, it is the destination address in the LOWPAN_IPHC for
packets going downwards. In non-storing mode, there is no implicit packets going downwards. In non-storing mode, there is no implicit
value for packets going downwards. value for packets going downwards.
If the implicit value is correct, the destination IP address of the If the implicit value is correct, the destination IP address of the
IP-in-IP encapsulation can be elided. Else, the destination IP IP-in-IP encapsulation can be elided. Else, the destination IP
address of the IP-in-IP header is transported in a SRH-6LoRH header address of the IP-in-IP header is transported in a SRH-6LoRH header
as the first entry of the first of these headers. as the first entry of the first of these headers.
If the final destination of the packet is a leaf that does not If the final destination of the packet is a leaf that does not
support this specification, then the chain of 6LoRH headers must be support this specification, then the chain of 6LoRH headers must be
stripped by the RPL/6LR router to which the leaf is attached. In 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 that example, the destination IP address of the IP-in-IP header
cannot be elided. cannot be elided.
In the special case where a 6LoRH header is used to route 6LoWPAN In the special case where a 6LoRH header is used to route 6LoWPAN
fragments, the destination address is not accessible in the IPHC on fragments, the destination address is not accessible in the
all fragments and can be elided only for the first fragment and for LOWPAN_IPHC on all fragments and can be elided only for the first
packets going upwards. fragment and for packets going upwards.
8. Management Considerations 8. Management Considerations
Though it is possible to decompress a packet at any hop, this Though it is possible to decompress a packet at any hop, this
specification is optimized to enable that a packet is forwarded in specification is optimized to enable that a packet is forwarded in
its compressed form all the way, and it makes sense to deploy its compressed form all the way, and it makes sense to deploy
homogeneous networks, where all nodes, or no node at all, use the homogeneous networks, where all nodes, or no node at all, use the
compression technique detailed therein. compression technique detailed therein.
This specification does not provide a method to discover the This specification does not provide a method to discover the
skipping to change at page 1, line 1125 skipping to change at page 1, line 1151
Critical 6LoWPAN Routing Header that it does not understand is an Critical 6LoWPAN Routing Header that it does not understand is an
administrative error whereby the wrong device is placed in a network, administrative error whereby the wrong device is placed in a network,
or the device is mis-configured. or the device is mis-configured.
When a mismatch situation is detected, it is expected that the device When a mismatch situation is detected, it is expected that the device
raises some management alert, indicating the issue, e.g. that it has raises some management alert, indicating the issue, e.g. that it has
to drop a packet with a Critical 6LoRH. to drop a packet with a Critical 6LoRH.
9. Security Considerations 9. Security Considerations
The security considerations of [RFC4944], [RFC6282], and [RFC6553] The security considerations of RFC 4944 [RFC4944], RFC 6282
apply. [RFC6282], and RFC 6553 [RFC6553] apply.
Using a compressed format as opposed to the full in-line format is 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 logically equivalent and is believed to not create an opening for a
new threat when compared to [RFC6550], [RFC6553] and [RFC6554], new threat when compared to RFC 6550 [RFC6550], RFC 6553 [RFC6553]
noting that, even though intermediate hops are removed from the SRH and RFC 6554 [RFC6554], noting that, even though intermediate hops
header as they are consumed, a node may still identify that the rest are removed from the SRH header as they are consumed, a node may
of the source routed path includes a loop or not (see Security still identify that the rest of the source routed path includes a
section of [RFC6554]. It must be noted that if the attacker is not loop or not (see Security section of RFC 6554). It must be noted
part of the loop, then there is always a node at the beginning of the that if the attacker is not part of the loop, then there is always a
loop that can detect it and remove it. node at the beginning of the loop that can detect it and remove it.
10. IANA Considerations 10. IANA Considerations
This specification reserves Dispatch Value Bit Patterns within the This specification reserves Dispatch Value Bit Patterns within the
6LoWPAN Dispatch Page 1 as follows: 6LoWPAN Dispatch Page 1 as follows:
101xxxxx: for Elective 6LoWPAN Routing Headers 101xxxxx: for Elective 6LoWPAN Routing Headers
100xxxxx: for Critical 6LoWPAN Routing Headers. 100xxxxx: for Critical 6LoWPAN Routing Headers.
Additionally this document creates two IANA registries, one for the Additionally this document creates two IANA registries, one for the
Critical 6LoWPAN Routing Header Type and one for the Elective 6LoWPAN Critical 6LoWPAN Routing Header Type and one for the Elective 6LoWPAN
Routing Header Type, each with 32 possible values from 0 to 31, as Routing Header Type, each with 32 possible values from 0 to 31, as
described below. described below.
Future assignments in these registries are to be coordinated via IANA Future assignments in these registries are to be coordinated via IANA
under the policy of "RFC Required" [RFC5226] to enable any type of under the policy of "RFC Required" (per RFC 5226 [RFC5226]) to enable
RFC to obtain a value in the registry. any type of RFC to obtain a value in the registry.
10.2. New Critical 6LoWPAN Routing Header Type Registry 10.2. New Critical 6LoWPAN Routing Header Type Registry
This document creates an IANA registry for the Critical 6LoWPAN This document creates an IANA registry for the Critical 6LoWPAN
Routing Header Type, and assigns the following values: Routing Header Type, and assigns the following values:
0..4: SRH-6LoRH [RFCthis] 0..4: SRH-6LoRH [RFCthis]
5: RPI-6LoRH [RFCthis] 5: RPI-6LoRH [RFCthis]
<- under the policy of "IETF Review" [RFC5226] to ensure adequate 10.3. New Elective 6LoWPAN Routing Header Type Registry
community review. -> ## New Elective 6LoWPAN Routing Header Type
Registry
This document creates an IANA registry for the Elective 6LoWPAN This document creates an IANA registry for the Elective 6LoWPAN
Routing Header Type, and assigns the following value: Routing Header Type, and assigns the following value:
6: IP-in-IP-6LoRH [RFCthis] 6: IP-in-IP-6LoRH [RFCthis]
<- under the policy of "IETF Review" [RFC5226] to ensure adequate
community review. ->
11. Acknowledgments 11. Acknowledgments
The authors wish to thank Tom Phinney, Thomas Watteyne, Tengfei The authors wish to thank Tom Phinney, Thomas Watteyne, Tengfei
Chang, Martin Turon, James Woodyatt, Samita Chakrabarti, Jonathan Chang, Martin Turon, James Woodyatt, Samita Chakrabarti, Jonathan
Hui, Gabriel Montenegro and Ralph Droms for constructive reviews to Hui, Gabriel Montenegro and Ralph Droms for constructive reviews to
the design in the 6lo Working Group. The overall discussion involved the design in the 6lo Working Group. The overall discussion involved
participants to the 6MAN, 6TiSCH and ROLL WGs, thank you all. participants to the 6MAN, 6TiSCH and ROLL WGs, thank you all.
Special thanks to the chairs of the ROLL WG, Michael Richardson and Special thanks to the chairs of the ROLL WG, Michael Richardson and
Ines Robles, Brian Haberman, Internet Area A-D, and Alvaro Retana and Ines Robles, Brian Haberman, Internet Area A-D, and Alvaro Retana and
Adrian Farrel, Routing Area A-Ds, for driving this complex effort Adrian Farrel, Routing Area A-Ds, for driving this complex effort
across Working Groups and Areas. across Working Groups and Areas.
12. References 12. References
12.1. Normative References 12.1. Normative References
[I-D.ietf-6lo-paging-dispatch] [I-D.ietf-6lo-paging-dispatch]
Thubert, P. and R. Cragie, "6LoWPAN Paging Dispatch", Thubert, P. and R. Cragie, "6LoWPAN Paging Dispatch",
draft-ietf-6lo-paging-dispatch-04 (work in progress), draft-ietf-6lo-paging-dispatch-05 (work in progress),
September 2016. October 2016.
[IEEE802154] [IEEE802154]
IEEE standard for Information Technology, "IEEE std. IEEE standard for Information Technology, "IEEE std.
802.15.4, Part. 15.4: Wireless Medium Access Control (MAC) 802.15.4, Part. 15.4: Wireless Medium Access Control (MAC)
and Physical Layer (PHY) Specifications for Low-Rate and Physical Layer (PHY) Specifications for Low-Rate
Wireless Personal Area Networks", 2015. Wireless Personal Area Networks", 2015.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
skipping to change at page 28, line 19 skipping to change at page 28, line 51
<http://www.rfc-editor.org/info/rfc7554>. <http://www.rfc-editor.org/info/rfc7554>.
Appendix A. Examples Appendix A. Examples
A.1. Examples Compressing The RPI A.1. Examples Compressing The RPI
The example in Figure 15 illustrates the 6LoRH compression of a The example in Figure 15 illustrates the 6LoRH compression of a
classical packet in Storing Mode in all directions, as well as in classical packet in Storing Mode in all directions, as well as in
non-Storing mode for a packet going up the DODAG following the non-Storing mode for a packet going up the DODAG following the
default route to the root. In this particular example, a default route to the root. In this particular example, a
fragmentation process takes place per [RFC4944], and the fragment fragmentation process takes place per RFC 4944 [RFC4944], and the
headers must be placed in Page 0 before switching to Page 1: fragment headers must be placed in Page 0 before switching to Page 1:
+- ... -+- ... -+-+ ... -+- ... +-+-+ ... -+-+-+-+-+-+-+-+-+-+... +- ... -+- ... -+-+ ... -+- ... +-+-+ ... -+-+-+-+-+-+-+-+-+-+...
|Frag type|Frag hdr |11110001| RPI- |IP-in-IP| LOWPAN-IPHC | ... |Frag type|Frag hdr |11110001| RPI- |IP-in-IP| LOWPAN_IPHC | ...
|RFC 4944 |RFC 4944 | Page 1 | 6LoRH | 6LoRH | | |RFC 4944 |RFC 4944 | Page 1 | 6LoRH | 6LoRH | |
+- ... -+- ... -+-+ ... -+- ... +-+-+ ... -+-+-+-+-+-+-+-+-+-+... +- ... -+- ... -+-+ ... -+- ... +-+-+ ... -+-+-+-+-+-+-+-+-+-+...
<- RFC 6282 -> <- RFC 6282 ->
No RPL artifact No RPL artifact
+- ... -+- ... -+-+ ... -+-+ ... -+- ... +-+-+-+-+-+-+-+-+-+-+... +- ... -+- ... -+-+ ... -+-+ ... -+- ... +-+-+-+-+-+-+-+-+-+-+...
|Frag type|Frag hdr | |Frag type|Frag hdr |
|RFC 4944 |RFC 4944 | Payload (cont) |RFC 4944 |RFC 4944 | Payload (cont)
+- ... -+- ... -+-+ ... -+-+ ... -+- ... +-+-+-+-+-+-+-+-+-+-+... +- ... -+- ... -+-+ ... -+-+ ... -+- ... +-+-+-+-+-+-+-+-+-+-+...
skipping to change at page 29, line 7 skipping to change at page 29, line 31
Figure 15: Example Compressed Packet with RPI. Figure 15: Example Compressed Packet with RPI.
In Storing Mode, if the packet stays within the RPL domain, then it 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 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 RPI is compressed with a 6LoRH, as illustrated in Figure 16 in
the case of a non-fragmented ICMP packet: the case of a non-fragmented ICMP packet:
+- ... -+-+- ... -+-+-+-+ ... -+-+-+-+ ... -+-+-+-+-+-+-+-+-+-+-+... +- ... -+-+- ... -+-+-+-+ ... -+-+-+-+ ... -+-+-+-+-+-+-+-+-+-+-+...
|11110001| RPI-6LoRH | NH = 0 | NH = 58 | ICMP message ... |11110001| RPI-6LoRH | NH = 0 | NH = 58 | ICMP message ...
|Page 1 | type 5 | 6LOWPAN-IPHC | (ICMP) | (no compression) |Page 1 | type 5 | 6LOWPAN_IPHC | (ICMP) | (no compression)
+- ... -+-+- ... -+-+-+-+ ... -+-+-+-+ ... -+-+-+-+-+-+-+-+-+-+-+... +- ... -+-+- ... -+-+-+-+ ... -+-+-+-+ ... -+-+-+-+-+-+-+-+-+-+-+...
<- RFC 6282 -> <- RFC 6282 ->
No RPL artifact No RPL artifact
Figure 16: Example ICMP Packet with RPI in Storing Mode. Figure 16: Example ICMP Packet with RPI in Storing Mode.
The format in Figure 16 is logically equivalent to the non-compressed The format in Figure 16 is logically equivalent to the non-compressed
format illustrated in Figure 17: format illustrated in Figure 17:
+-+-+-+- ... -+-+-+-+ ... -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+... +-+-+-+- ... -+-+-+-+ ... -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...
| IPv6 Header | Hop-by-Hop | RPI in | ICMP message ... | IPv6 Header | Hop-by-Hop | RPI in | ICMP message ...
| NH = 58 | Header | RPL Option | | NH = 58 | Header | RPL Option |
+-+-+-+- ... -+-+-+-+ ... -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+... +-+-+-+- ... -+-+-+-+ ... -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...
Figure 17: Uncompressed ICMP Packet with RPI. Figure 17: Uncompressed ICMP Packet with RPI.
For a UDP packet, the transport header can be compressed with 6LoWPAN For a UDP packet, the transport header can be compressed with 6LoWPAN
HC [RFC6282] as illustrated in Figure 18: HC [RFC6282] as illustrated in Figure 18:
+- ... -+- ... -+-+-+-+- ... +-+-+-+-+-+-+-+-+-+- ... +-+-+-+-+-+... +-+ ... -+-+-...-+-+- ... -+-+-+-+ ... -+-+-+ ... -+-+-+-+-+...
|11110001| RPI-6LoRH | NH = 1 |11110|C| P | Compressed |UDP ... |11110001| RPI- | NH=1 |11110CPP| Compressed | UDP
|Page 1 | type 5 | 6LOWPAN-IPHC | UDP | | | UDP header |Payload |Page 1 | 6LoRH | LOWPAN_IPHC | UDP | UDP header | Payload
+- ... -+- ... -+-+-+-+- ... +-+-+-+-+-+-+-+-+-+- ... +-+-+-+-+-+... +-+ ... -+-+-...-+-+- ... -+-+-+-+ ... -+-+-+ ... -+-+-+-+-+...
<- RFC 6282 -> <- RFC 6282 ->
No RPL artifact No RPL artifact
Figure 18: Uncompressed ICMP Packet with RPI. Figure 18: Uncompressed ICMP Packet with RPI.
If the packet is received from the Internet in Storing Mode, then the If the packet is received from the Internet in Storing Mode, then the
root is supposed to encapsulate the packet to insert the RPI. The root is supposed to encapsulate the packet to insert the RPI. The
resulting format would be as represented in Figure 19: resulting format would be as represented in Figure 19:
+-+-+-+-+-+-+- ... -+-+-- ... -+-+- ... -+-+-+-+-+-+-+ ... -+-+-+-+... +-+ ... -+-+-...-+-+-- ... -+-+-+-+- ... -+-+ ... -+-+-+ ... -+-+-+...
|11110001 | RPI-6LoRH | IP-in-IP | NH=1 |11110CPP| Compressed | UDP |11110001| RPI- | IP-in-IP | NH=1 |11110CPP| Compressed | UDP
|Page 1 | | 6LoRH | IPHC | UDP | UDP header | Payload |Page 1 | 6LoRH | 6LoRH | LOWPAN_IPHC | UDP | UDP header | Payld
+-+-+-+-+-+-+- ... -+-+-- ... -+-+- ... -+-+-+-+-+-+-+ ... -+-+-+-+... +-+ ... -+-+-...-+-+-- ... -+-+-+-+- ... -+-+ ... -+-+-+ ... -+-+-+...
<- RFC 6282 -> <- RFC 6282 ->
No RPL artifact No RPL artifact
Figure 19: RPI inserted by the root in Storing Mode. Figure 19: RPI inserted by the root in Storing Mode.
A.2. Example Of Downward Packet In Non-Storing Mode A.2. Example Of Downward Packet In Non-Storing Mode
The example illustrated in Figure 20 is a classical packet in non- The example illustrated in Figure 20 is a classical packet in non-
Storing mode for a packet going down the DODAG following a source Storing mode for a packet going down the DODAG following a source
routed path from the root. Say that we have 4 forwarding hops to routed path from the root. Say that we have 4 forwarding hops to
reach a destination. In the non-compressed form, when the root reach a destination. In the non-compressed form, when the root
generates the packet, the last 3 hops are encoded in a Routing Header generates the packet, the last 3 hops are encoded in a Routing Header
type 3 (SRH) and the first hop is the destination of the packet. The type 3 (SRH) and the first hop is the destination of the packet. The
intermediate hops perform a swap and the hop count indicates the intermediate hops perform a swap and the hop count indicates the
current active hop [RFC2460], [RFC6554]. current active hop as defiend in RFC 2460 [RFC2460] and RFC 6554
[RFC6554].
When compressed with this specification, the 4 hops are encoded in When compressed with this specification, the 4 hops are encoded in
SRH-6LoRH when the root generates the packet, and the final SRH-6LoRH when the root generates the packet, and the final
destination is left in the LOWPAN-IPHC. There is no swap, and the destination is left in the LOWPAN_IPHC. There is no swap, and the
forwarding node that corresponds to the first entry effectively forwarding node that corresponds to the first entry effectively
consumes it when forwarding, which means that the size of the encoded consumes it when forwarding, which means that the size of the encoded
packet decreases and that the hop information is lost. packet decreases and that the hop information is lost.
If the last hop in a SRH-6LoRH is not the final destination then it If the last hop in a SRH-6LoRH is not the final destination then it
removes the SRH-6LoRH before forwarding. removes the SRH-6LoRH before forwarding.
In the particular example illustrated in Figure 20, all addresses in In the particular example illustrated in Figure 20, all addresses in
the DODAG are assigned from a same /112 prefix and the last 2 octets the DODAG are assigned from a same /112 prefix and the last 2 octets
encoding an identifier such as a IEEE 802.15.4 short address. In 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 that case, all addresses can be compressed to 2 octets, using the
root address as reference. There will be one SRH_6LoRH header, with, root address as reference. There will be one SRH_6LoRH header, with,
in this example, 3 compressed addresses: in this example, 3 compressed addresses:
+-+-+-+-+-+-+- ... +-+-+- ... -+-+-- ... -+-+- ... -+-+-+-+-+ ... +-... +-+-+-+-+-+-+- ... +-+-+- ... -+-+-- ... -+-+- ... -+-+-+-+-+ ... +-...
|11110001 |SRH-6LoRH | RPI-6LoRH | IP-in-IP | NH=1 |11110CPP| UDP | UDP |11110001 |SRH-6LoRH | RPI-6LoRH | IP-in-IP | NH=1 |11110CPP| UDP | UDP
|Page 1 |Type1 S=2 | | 6LoRH | IPHC | UDP | hdr |load |Page 1 |Type1 S=2 | | 6LoRH |LOWPAN_IPHC | UDP | hdr |load
+-+-+-+-+-+-+- ... +-+-+- ... -+-+-- ... -+-+- ... -+-+-+-+-+ ... +-... +-+-+-+-+-+-+- ... +-+-+- ... -+-+-- ... -+-+- ... -+-+-+-+-+ ... +-...
<-8bytes-> <- RFC 6282 -> <-8bytes-> <- RFC 6282 ->
No RPL artifact No RPL artifact
Figure 20: Example Compressed Packet with SRH. Figure 20: Example Compressed Packet with SRH.
One may note that the RPI is provided. This is because the address 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 of the root that is the source of the IP-in-IP header is elided and
inferred from the RPLInstanceID in the RPI. Once found from a local inferred from the RPLInstanceID in the RPI. Once found from a local
context, that address is used as Compression Reference to expand context, that address is used as Compression Reference to expand
addresses in the SRH-6LoRH. addresses in the SRH-6LoRH.
With the RPL specifications available at the time of writing this With the RPL specifications available at the time of writing this
draft, the root is the only node that may incorporate a SRH in an IP draft, the root is the only node that may incorporate a SRH in an IP
packet. When the root forwards a packet that it did not generate, it packet. When the root forwards a packet that it did not generate, it
has to encapsulate the packet with IP-in-IP. has to encapsulate the packet with IP-in-IP.
But if the root generates the packet towards a node in its DODAG, 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: then it should avoid the extra IP-in-IP as illustrated in Figure 21:
+- ... -+-+-+ ... +-+-+-+ ... -+-+-+-+-+-+-+-++-+- ... -+-+-+-+-+... +- ... -+-+-+ ... +-+-+-+ ... -+-+-+-+-+-+-+-++-+- ... -+-+-+-+-+...
|11110001| SRH-6LoRH | NH=1 | 11110CPP | Compressed | UDP |11110001| SRH-6LoRH | NH=1 | 11110CPP | Compressed | UDP
|Page 1 | Type1 S=3 | LOWPAN-IPHC| LOWPAN-NHC| UDP header | Payload |Page 1 | Type1 S=3 | LOWPAN_IPHC| LOWPAN-NHC| UDP header | Payload
+- ... -+-+-+ ... +-+-+-+ ... -+-+-+-+-+-+-+-++-+- ... -+-+-+-+-+... +- ... -+-+-+ ... +-+-+-+ ... -+-+-+-+-+-+-+-++-+- ... -+-+-+-+-+...
<- RFC 6282 -> <- RFC 6282 ->
Figure 21: compressed SRH 4*2bytes entries sourced by root. Figure 21: compressed SRH 4*2bytes entries sourced by root.
Note: the RPI is not represented though RPL [RFC6550] generally Note: the RPI is not represented though RPL [RFC6550] generally
expects it. In this particular case, since the Compression Reference expects it. In this particular case, since the Compression Reference
for the SRH-6LoRH is the source address in the LOWPAN-IPHC, and the for the SRH-6LoRH is the source address in the LOWPAN_IPHC, and the
routing is strict along the source route path, the RPI does not routing is strict along the source route path, the RPI does not
appear to be absolutely necessary. appear to be absolutely necessary.
In Figure 21, all the nodes along the source route path share a same In Figure 21, all the nodes along the source route path share a same
/112 prefix. This is typical of IPv6 addresses derived from an /112 prefix. This is typical of IPv6 addresses derived from an
IEEE802.15.4 short address, as long as all the nodes share a same IEEE802.15.4 short address, as long as all the nodes share a same
PAN-ID. In that case, a type-1 SRH-6LoRH header can be used for PAN-ID. In that case, a type-1 SRH-6LoRH header can be used for
encoding. The IPv6 address of the root is taken as reference, and encoding. The IPv6 address of the root is taken as reference, and
only the last 2 octets of the address of the intermediate hops is only the last 2 octets of the address of the intermediate hops is
encoded. The Size of 3 indicates 4 hops, resulting in a SRH-6LoRH of encoded. The Size of 3 indicates 4 hops, resulting in a SRH-6LoRH of
 End of changes. 88 change blocks. 
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