draft-ietf-6lo-routing-dispatch-03.txt   draft-ietf-6lo-routing-dispatch-04.txt 
6lo P. Thubert, Ed. 6lo P. Thubert, Ed.
Internet-Draft Cisco Internet-Draft Cisco
Intended status: Standards Track C. Bormann Intended status: Standards Track C. Bormann
Expires: July 18, 2016 Uni Bremen TZI Expires: July 26, 2016 Uni Bremen TZI
L. Toutain L. Toutain
IMT-TELECOM Bretagne IMT-TELECOM Bretagne
R. Cragie R. Cragie
ARM ARM
January 15, 2016 January 23, 2016
6LoWPAN Routing Header And Paging Dispatches 6LoWPAN Routing Header
draft-ietf-6lo-routing-dispatch-03 draft-ietf-6lo-routing-dispatch-04
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.
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This Internet-Draft will expire on July 18, 2016. This Internet-Draft will expire on July 26, 2016.
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.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Using the Page Dispatch . . . . . . . . . . . . . . . . . . . 5 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 The 6LoRH . . . . . . . . . . . . . . . . . 6 3.2. Placement Of 6LoRH headers . . . . . . . . . . . . . . . 6
4. 6LoWPAN Routing Header General Format . . . . . . . . . . . . 6 3.2.1. Relative To Non-6LoRH Headers . . . . . . . . . . . . 7
4.1. Elective Format . . . . . . . . . . . . . . . . . . . . . 7 3.2.2. Relative To Other 6LoRH Headers . . . . . . . . . . . 7
4.2. Critical Format . . . . . . . . . . . . . . . . . . . . . 7 4. 6LoWPAN Routing Header General Format . . . . . . . . . . . . 8
5. The Routing Header Type 3 (RH3) 6LoRH Header . . . . . . . . 8 4.1. Elective Format . . . . . . . . . . . . . . . . . . . . . 8
6. The RPL Packet Information 6LoRH . . . . . . . . . . . . . . 10 4.2. Critical Format . . . . . . . . . . . . . . . . . . . . . 9
6.1. Compressing the RPLInstanceID . . . . . . . . . . . . . . 11 4.3. Compressing Addresses . . . . . . . . . . . . . . . . . . 9
6.2. Compressing the SenderRank . . . . . . . . . . . . . . . 11 4.3.1. Coalescence . . . . . . . . . . . . . . . . . . . . . 10
6.3. The Overall RPI-6LoRH encoding . . . . . . . . . . . . . 12 4.3.2. DODAG Root Address Determination . . . . . . . . . . 10
7. The IP-in-IP 6LoRH Header . . . . . . . . . . . . . . . . . . 14 5. The Routing Header Type 3 (RH3) 6LoRH Header . . . . . . . . 11
8. Security Considerations . . . . . . . . . . . . . . . . . . . 15 5.1. RH3-6LoRH General Operation . . . . . . . . . . . . . . . 13
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 5.2. The Design Point of Popping Entries . . . . . . . . . . . 13
9.1. Reserving Space in 6LoWPAN Dispatch Page 1 . . . . . . . 15 5.3. Compression Reference . . . . . . . . . . . . . . . . . . 14
9.2. Nex 6LoWPAN Routing Header Type Registry . . . . . . . . 16 5.4. Popping Headers . . . . . . . . . . . . . . . . . . . . . 15
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 5.5. Forwarding . . . . . . . . . . . . . . . . . . . . . . . 16
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 6. The RPL Packet Information 6LoRH . . . . . . . . . . . . . . 16
11.1. Normative References . . . . . . . . . . . . . . . . . . 16 6.1. Compressing the RPLInstanceID . . . . . . . . . . . . . . 18
11.2. Informative References . . . . . . . . . . . . . . . . . 17 6.2. Compressing the SenderRank . . . . . . . . . . . . . . . 18
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 18 6.3. The Overall RPI-6LoRH encoding . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 7. The IP-in-IP 6LoRH Header . . . . . . . . . . . . . . . . . . 21
8. Security Considerations . . . . . . . . . . . . . . . . . . . 22
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
9.1. Reserving Space in 6LoWPAN Dispatch Page 1 . . . . . . . 22
9.2. New 6LoWPAN Routing Header Type Registry . . . . . . . . 23
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 23
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 23
11.1. Normative References . . . . . . . . . . . . . . . . . . 23
11.2. Informative References . . . . . . . . . . . . . . . . . 24
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 25
A.1. Examples Compressing The RPI . . . . . . . . . . . . . . 25
A.2. Example Of Downward Packet In Non-Storing Mode . . . . . 27
A.3. Example of RH3-6LoRH life-cycle . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30
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
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The terms Route-over and Mesh-under are defined in [RFC6775]. The terms Route-over and Mesh-under are defined in [RFC6775].
Other terms in use in LLNs are found in [RFC7228]. Other terms in use in LLNs are found in [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
The6LoWPAN 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 ([RFC4944],
[RFC6282]) by introducing a concept of "context" in the 6LoWPAN [RFC6282]) by introducing a concept of "context" in the 6LoWPAN
parser, a context being identified by a Page number. The parser, a context being identified by a Page number. The
specification defines 16 Pages. 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)
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information such as a compressed form of RH3, as well as other sorts information such as a compressed form of RH3, as well as other sorts
of routing information such as the RPI and IP-in-IP encapsulation. of routing information such as the RPI and IP-in-IP encapsulation.
The 6LoRH is expressed in a 6loWPAN packet as a Type-Length-Value The 6LoRH is expressed in a 6loWPAN packet as a Type-Length-Value
(TLV) field, which is extensible for future use. (TLV) field, which is extensible for future use.
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 The 6LoRH 3.2. Placement Of 6LoRH headers
3.2.1. Relative To Non-6LoRH Headers
Paging Dispatch is parsed and no subsequent Paging Dispatch has been Paging Dispatch is parsed and no subsequent Paging Dispatch has been
parsed, the parsing of the packet MUST follow this specification if parsed, the parsing of the packet MUST follow this specification if
the 6LoRH Bit Pattern Section 3.1 is found. the 6LoRH Bit Pattern 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.
One or more 6LoRH header(s) MAY be placed in a 6LoWPAN packet. A
6LoRH header MUST always be placed before the LOWPAN_IPHC as defined
in 6LoWPAN Header Compression [RFC6282].
Because a 6LoRH header requires a Page 1 context, it MUST always be 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 [RFC4944].
A 6LoRH header MUST always be placed before the LOWPAN_IPHC as
defined in 6LoWPAN Header Compression [RFC6282]. It is designed in
such a fashion that placing or removing a header that is encoded with
6LoRH does not modify the part of the packet that is encoded with
LoWPAN_IPHC, whether there is an IP-in-IP encapsulation or not. For
instance, the final destination of the packet is always the one in
the LOWPAN_IPHC whether there is a Routing Header or not.
3.2.2. Relative To Other 6LoRH Headers
IPv6 [RFC2460] defines chains of headers that are introduced by an
IPv6 header and terminated by either another IPv6 header (IP-in-IP)
or an Upper Layer Protocol ULP) header. When an outer header is
stripped from the packet, the whole chain goes with it. When one or
more header(s) are inserted by an intermediate router, that router
normally chains the headers and encapsulates the result in IP-in-IP.
With this specification, the chains of headers MUST be compressed in
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
encapsulations, the first IP-in-IP encapsulation, with all its chain
of headers, is encoded first in the compressed form.
In the compressed form of a packet that has RH3 or HbH headers after
the inner IPv6 header (e.g. if there is no IP-in-IP encapsulation),
these headers are placed in the 6LoRH form before the 6LOWPAN-IPHC
that represents the IPv6 header Section 3.2.1. If this packet gets
encapsulated and some other RH3 or HbH 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
uncompressed form.
In order to disambiguate the headers that follow the inner IPv6
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
header is placed last in the encoded chain. This means that the
6LoRH headers that are found after the last compressed IP-in-IP
header are to be inserted after the IPv6 header that is encoded with
the 6LOWPAN-IPHC when decompressing the packet.
With regards to the relative placement of the RH3 and the RPI in the
compressed form, it is a design point for this specification that the
RH3 entries are consumed as the packet progresses down the LLN
Section 5.2. In order to make this operation simpler in the
compressed form, it is REQUIRED that the in the compressed form, the
addresses along the source route path are encoded in the order of the
path, and that the compressed RH3 are placed before the compressed
RPI.
4. 6LoWPAN Routing Header General Format 4. 6LoWPAN Routing Header General Format
The 6LoRH reuses in Page 1 the Dispatch Value Bit Pattern of The 6LoRH usesthe Dispatch Value Bit Pattern of 10xxxxxx in Page 1.
10xxxxxx.
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
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
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Type Specific Extension. The meaning depends on the Type, which Type Specific Extension. The meaning depends on the Type, which
must be known in all of the nodes. The interpretation of the TSE must be known in all of the nodes. The interpretation of the TSE
depends on the Type field that follows. For instance, it may be depends on the Type field that follows. For instance, it may be
used to transport control bits, the number of elements in an used to transport control bits, the number of elements in an
array, or the length of the remainder of the 6LoRHC expressed in a array, or the length of the remainder of the 6LoRHC expressed in a
unit other than bytes. unit other than bytes.
Type: Type:
Type of the 6LoRHC Type of the 6LoRHC
4.3. Compressing Addresses
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
address, and then elide that matching piece. In order to reconstruct
the compress address, the receiving node will perform the process of
coalescence described in section Section 4.3.1.
One possible reference is the root of the RPL DODAG that is being
traversed. It is used to compress an outer IP-in-IP header, and if
the root is the source of the packet, the technique allows to fully
elide the source address in the compressed form of the IP header. If
the root is not the encapsulator, then the encapsulator address may
still be compressed using the root as reference. How the address of
the root is determined is discussed in Section 4.3.2.
Once the address of the source of the packet is determined, it
becomes the reference for the compression of the addresses that are
located in compressed RH3 headers that are present inside the IP-in-
IP encapsulation in the uncompressed form.
4.3.1. Coalescence
An IPv6 compressed address is coalesced with a reference address by
overriding the N rightmost bytes of the reference address with the
compressed address, where N is the length of the compressed address,
as indicated by the Type of the RH3-6LoRH header in Figure 7.
The reference address MAY be a compressed address as well, in which
case it MUST be compressed in a form that is of an equal or greater
length than the address that is being coalesced.
A compressed address is expanded by coalescing it with a reference
address. In the particular case of a Type 4 RH3-6LoRH, the address
is expressed in full and the coalescence is a complete override as
illustrated in Figure 5.
RRRRRRRRRRRRRRRRRRRR reference address, may be compressed or not
CCCCCCC compressed address, shorter or same as reference
RRRRRRRRRRRRRCCCCCCC Coalesced address, same compression as reference
Figure 5: Coalescing addresses.
4.3.2. DODAG Root Address Determination
Stateful Address compression requires that some state is installed in
the devices to store the compression information that is elided from
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
information from the context table.
With [RFC6282], the state is provided to the stack by the 6LoWPAN
Neighbor Discovery Protocol (NDP) [RFC6775]. NDP exchanges the
context through 6LoWPAN Context Option in Router Advertisement (RA)
messages. In the compressed form of the packet, the context can be
signaled in a Context Identifier Extension.
With this specification, the compression information is provided to
the stack by RPL, and RPL exchanges it through the DODAGID field in
the DAG Information Object (DIO) messages, as described in more
details below. In the compressed form of the packet, the context can
be signaled in by the InstanceID in the RPI.
With RPL [RFC6550], the address of DODAG root is known from the
DODAGID field of the DIO messages. For a Global Instance, the
RPLInstanceID that is present in the RPI is enough information to
identify the DODAG that this node participates to and its associated
root. But for a Local Instance, the address of the root MUST be
explicit, either in some device configuration or signaled in the
packet, as the source or the destination address, respectively.
When implicit, the address of the DODAG root MUST be determined as
follows:
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 RPL does
not expose that property and it can only be known by a configuration
applied to all nodes.
Else, the router that encapsulates the packet and compresses it with
this specification MUST also place an RPI in the packet as prescribed
by [RFC6550] to enable the identification of the DODAG. The RPI must
be present even in the case when the router also places an RH3 header
in the packet.
It is expected that the RPL implementation provides an abstract
context table, indexed by Global RPLInstanceID, that provides the
address of the root of the DODAG that this nodes participates to for
that particular Instance.
5. The Routing Header Type 3 (RH3) 6LoRH Header 5. The Routing Header Type 3 (RH3) 6LoRH Header
## Encoding {#RH3-6LoRH-encoding}
The Routing Header type 3 (RH3) 6LoRH (RH3-6LoRH) header is a The Routing Header type 3 (RH3) 6LoRH (RH3-6LoRH) header is a
Critical 6LoWPAN Routing Header that provides a compressed form for Critical 6LoWPAN Routing Header that provides a compressed form for
the RH3, as defined in [RFC6554] for use by RPL routers. Routers the RH3, as defined in [RFC6554] for use by RPL routers. Routers
that need to forward a packet with a RH3-6LoRH are expected to be RPL that need to forward a packet with a RH3-6LoRH are expected to be RPL
routers and are expected to support this specification. If a non-RPL routers and are expected to support this specification. If a non-RPL
router receives a packet with a RH3-6LoRH, this means that there was router receives a packet with a RH3-6LoRH, this means that there was
a routing error and the packet should be dropped so the Type cannot a routing error and the packet should be dropped so the Type cannot
be ignored. be ignored.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- -+- -+ ... +- -+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- -+- -+ ... +- -+
|1|0|0| Size |6LoRH Type 0..4| Hop1 | Hop2 | | HopN | |1|0|0| Size |6LoRH Type 0..4| Hop1 | Hop2 | | HopN |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- -+- -+ ... +- -+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- -+- -+ ... +- -+
Size indicates the number of compressed addresses Size indicates the number of compressed addresses
Figure 5: The RH3-6LoRH. Figure 6: The RH3-6LoRH.
The values for the RH3-6LoRH Type are an enumeration, 0 to 4. The The 6LoRH Type indicates the compression level used in a given
form of compression is indicated by the Type. The unit (as a number RH3-6LoRH header.
of bytes) in which the Size is expressed depends on the Type as
described in Figure 6:
+-----------+-----------+ One or more 6LoRH header(s) MAY be placed in a 6LoWPAN packet.
| Type | Size Unit |
+-----------+-----------+
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 8 |
| 4 | 16 |
+-----------+-----------+
Figure 6: The RH3-6LoRH Types. It results that all addresses in a given RH3-6LoRH header MUST be
compressed in an identical fashion, down to using the identical
number of bytes per address. In order to get different degrees of
compression, multiple consecutive RH3-6LoRH headers MUST be used.
Type 0 means that the address is compressed down to one byte, whereas
Type 4 means that the address is provided in full in the RH3-6LoRH
with no compression. The complete list of Types of RH3-6LoRH and the
corresponding compression level are provided in Figure 7:
+-----------+----------------------+
| 6LoRH | Length of compressed |
| Type | IPv6 address (bytes) |
+-----------+----------------------+
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 8 |
| 4 | 16 |
+-----------+----------------------+
Figure 7: The RH3-6LoRH Types.
In the case of a RH3-6LoRH header, the TSE field is used as a Size, In the case of a RH3-6LoRH header, the TSE field is used as a Size,
which encodes the number of hops minus 1; so a Size of 0 means one which encodes the number of hops minus 1; so a Size of 0 means one
hop, and the maximum that can be encoded is 32 hops. (If more than hop, and the maximum that can be encoded is 32 hops. (If more than
32 hops need to be expressed, a sequence of RH3-6LoRH elements can be 32 hops need to be expressed, a sequence of RH3-6LoRH elements can be
employed.) employed.) It results that the Length in bytes of a RH3-6LoRH header
is:
The Next Hop is indicated in the first entry of the first RH3-6LoRH 2 + Length_of_compressed_IPv6_address * (Size + 1)
header. Upon reception, the router checks whether the address
indicated as Next Hop is one of its own addresses, which MUST be the
case in a strict source-routing environment. In that case, the entry
is removed from the RH3-6LoRH header and the Size is decremented. If
that makes the Size zero, the whole RH3-6LoRH header is removed. If
there are no more RH3-6LoRH headers, the processing node is the last
router on the path, which may or may not be collocated with the final
destination.
The last hop in the last RH3-6LoRH is the last router on the way to 5.1. RH3-6LoRH General Operation
the destination in the LLN. In a classical RPL network, all nodes
are routers so the last hop is effectively the destination as well,
but in the general case, even when there is a RH3-6LoRH header
present, the address of the final destination is always indicated in
the LoWPAN_IPHC [RFC6282].
If some bits of the first address in the RH3-6LoRH header can be In the non-compressed form, when the root generates or forwards a
derived from the final destination in the LoWPAN_IPHC, then that packet in non-Storing Mode, it needs to include a Routing Header type
address may be compressed; otherwise it is expressed as a full IPv6 3 (RH3) [RFC6554] to signal a strict source-route path to a final
address of 128 bits. Next addresses only need to express the delta destination down the DODAG. All the hops along the path, but the
from the previous address. first one, are encoded in order in the RH3. The last entry in the
RH3 is the final destination and the destination in the IPv6 header
is the first hop along the source-route path. The intermediate hops
perform a swap and the Segment-Left field indicates the active entry
in the Routing Header [RFC2460]. The current destination of the
packet, which is the termination of the current segment, is indicated
at all times by the destination address of the IPv6 header.
All addresses in a given RH3-6LoRH header are compressed in an The handling of the RH3-6LoRH is different: there is no swap, and a
identical fashion, down to using the identical number of bytes per forwarding router that corresponds to the first entry in the first
address. In order to get different degrees of compression, multiple RH3-6LoRH upon reception of a packet effectively consumes that entry
consecutive RH3-6LoRH headers MUST be used when forwarding. This means that the size of a compressed source-
routed packet decreases as the packet progresses along its path and
that the routing information is lost along the way. This also means
that an RH3 encoded with 6LoRH is not recoverable and cannot be
protected.
When compressed with this specification, all the remaining hops MUST
be encoded in order in one or more consecutive RH3-6LoRH headers.
Whether or not there is a RH3-6LoRH header present, the address of
the final destination is indicated in the LoWPAN_IPHC at all times
along the path. Examples of this are provided in Appendix A.
The current destination (termination of the current segment) for a
compressed source-routed packet is indicated in the first entry of
the first RH3-6LoRH. In strict source-routing, that entry MUST match
an address of the router that receives the packet.
The last entry in the last RH3-6LoRH is the last router on the way to
the final destination in the LLN. It is typically a RPL parent of
the final destination, but it can also be a router acting at 6LR
[RFC6775] for the destination host.
5.2. The Design Point of Popping Entries
In order to save energy and to optimize the chances of transmission
success on lossy media, it is a design point for this specification
that the entries in the RH3 that have been used are removed from the
packet. This creates a discrepancy from the art of IPv6 where
Routing Header are mutable but recoverable.
With this specification, the packet can be expanded at any hop into a
valid IPv6 packet, including a RH3, and compressed back. But the
packet as decompressed along the way will not carry all the consumed
addresses that packet would have if it had been forwarded in the
uncompressed form.
It is noted that:
The value of keeping the whole RH in an IPv6 header is for the
receiver to reverse it to use the symmetrical path on the way
back.
It is generally not a good idea to reverse a routing header. The
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).
There is no use of reversing a RH in the present RPL
specifications.
P2P RPL reverses a path that was learned reactively, as a part of
the protocol operation, which is probably a cleaner way than a
reversed echo on the data path.
Reversing a header is discouraged by [RFC2460] for RH0 unless it
is authenticated, which requires an Authentication Header (AH).
There is no definition of an AH operation for RH3, 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
validation at the receiver with the sole value of enabling the
receiver to reversing it.
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
a better security than that provided by AH.
In summary, the benefit of saving energy and lowering the chances of
loss by sending smaller frames over the LLN are seen as overwhelming
compared to the value of possibly reversing the header.
5.3. Compression Reference
In order to optimize the compression of IP addresses present in the
RH3 headers, this specification requires that the 6LoWPAN layer
identifies an address that is used as reference for the compression.
With this specification, the Compression Reference for addresses
found in an RH3 header is the source of the IPv6 packet.
With RPL [RFC6550], an RH3 header may only be present in Non-Storing
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
[RFC2460]. In this case, the address used as Compression Reference
is that the address of the root, and it can be implicit when the
address of the root is.
The Compression Reference MUST be determined as follows:
The reference address may be obtained by configuration. The
configuration may indicate either the address in full, or the
identifier of a 6LoWPAN Context that carries the address [RFC6775],
for instance one of the 16 Context Identifiers used in LOWPAN-IPHC
[RFC6282].
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
reference for the compression.
Else, and if the IP-in-IP compression specified in this document is
used and the Encapsulator Address is provided, then the Encapsulator
Address is the reference.
5.4. Popping Headers
Upon reception, the router checks whether the address in the first
entry of the first RH3-6LoRH one of its own addresses. In that case,
router MUST consume that entry before forwarding, which is an action
of popping from a stack, where the stack is effectively the sequence
of entries in consecutive RH3-6LoRH headers.
Popping an entry of an RH3-6LoRH header is a recursive action
performed as follows:
If the Size of the RH3-6LoRH header is 1 or more, indicating that
there are at least 2 entries in the header, the router removes the
first entry and decrements the Size (by 1).
Else (meaning that this is the last entry in the RH3-6LoRH header),
and if there is no next RH3-6LoRH header after this then the
RH3-6LoRH is removed.
Else, if there is a next RH3-6LoRH of a Type with a larger or equal
value, meaning a same or lesser compression yielding same or larger
compressed forms, then the RH3-6LoRH is removed.
Else, the first entry of the next RH3-6LoRH is popped from the next
RH3-6LoRH and coalesced with the first entry of this RH3-6LoRH.
At the end of the process, if there is no more RH3-6LoRH in the
packet, then the processing node is the last router along the source
route path.
5.5. Forwarding
When receiving a packet with a RH3-6LoRH, a router determines the
IPv6 address of the current segment endpoint.
If strict source routing is enforced and thus router is not the
segment endpoint for the packet then this router MUST drop the
packet.
If this router is the current segment endpoint, then the router pops
its address as described in Section 5.4 and continues processing the
packet.
If there is still a RH3-6LoRH, then the router determines the new
segment endpoint and routes the packet towards that endpoint.
Otherwise the router uses the destination in the inner IP header to
forward or accept the packet.
The segment endpoint of a packet MUST be determined as follows:
The router first determines the Compression Reference as discussed in
Section 4.3.1.
The router then coalesces the Compression Reference with the first
entry of the first RH3-6LoRH header as discussed in Section 5.3. If
the type of the RH3-6LoRH header is type 4 then the coalescence is a
full override.
Since the Compression Reference is an uncompressed address, the
coalesced IPv6 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) [RFC6550], Section 11.2, specifies the RPL Packet Information (RPI)
as a set of fields that are placed by RPL routers in IP packets for as a set of fields that are placed by RPL routers in IP packets for
the purpose of Instance Identification, as well as Loop Avoidance and the purpose of Instance Identification, as well as Loop Avoidance and
Detection. Detection.
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 [RFC6552], indicates the
skipping to change at page 1, line 498 skipping to change at page 1, line 818
RPL Instances are discussed in [RFC6550], Section 5. A number of RPL Instances are discussed in [RFC6550], Section 5. A number of
simple use cases do not require more than one instance, and in such simple use cases do not require more than one instance, and in such
cases, the instance is expected to be the global Instance 0. A cases, the instance is expected to be the global Instance 0. A
global RPLInstanceID is encoded in a RPLInstanceID field as follows: global RPLInstanceID is encoded in a 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 7: 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 [RFC6550],
skipping to change at page 1, line 554 skipping to change at page 1, line 874
the RPLInstanceID is elided and/or the SenderRank is compressed. the RPLInstanceID is elided and/or the SenderRank is compressed.
Depending on these bits, the Length of the RPI-6LoRH may vary as Depending on these bits, the Length of the RPI-6LoRH may vary as
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 8: 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 [RFC6550],
section 11.2. section 11.2.
I bit: If it is set, the Instance ID is elided and the RPLInstanceID I bit: If it is set, the Instance ID is elided and the RPLInstanceID
is the Global RPLInstanceID 0. If it is not set, the octet is the Global RPLInstanceID 0. If it is not set, the octet
immediately following the type field contains the RPLInstanceID immediately following the type field contains the RPLInstanceID
as specified in [RFC6550], section 5.1. as specified in [RFC6550], section 5.1.
K bit: If it is set, the SenderRank is compressed into one octet, K bit: If it is set, the SenderRank is compressed into one octet,
with the least significant octet elided. If it is not set, the 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 9, the RPLInstanceID is the Global RPLInstanceID 0, and the In Figure 10, the RPLInstanceID is the Global RPLInstanceID 0, and
MinHopRankIncrease is a multiple of 256 so the least significant byte the MinHopRankIncrease is a multiple of 256 so the least significant
is all zeros and can be elided: byte is all zeros and can be elided:
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|0|O|R|F|1|1| 6LoRH Type=5 | SenderRank | |1|0|0|O|R|F|1|1| 6LoRH Type=5 | SenderRank |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
I=1, K=1 I=1, K=1
Figure 9: The most compressed RPI-6LoRH. Figure 10: The most compressed RPI-6LoRH.
In Figure 10, the RPLInstanceID is the Global RPLInstanceID 0, but In Figure 11, the RPLInstanceID is the Global RPLInstanceID 0, but
both bytes of the SenderRank are significant so it can not be both bytes of the SenderRank are significant so it can not be
compressed: compressed:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0|0|O|R|F|1|0| 6LoRH Type=5 | SenderRank | |1|0|0|O|R|F|1|0| 6LoRH Type=5 | SenderRank |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
I=1, K=0 I=1, K=0
Figure 10: Eliding the RPLInstanceID. Figure 11: Eliding the RPLInstanceID.
In Figure 11, the RPLInstanceID is not the Global RPLInstanceID 0, In Figure 12, the RPLInstanceID is not the Global RPLInstanceID 0,
and the MinHopRankIncrease is a multiple of 256: and the MinHopRankIncrease is a multiple of 256:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0|0|O|R|F|0|1| 6LoRH Type=5 | RPLInstanceID | SenderRank | |1|0|0|O|R|F|0|1| 6LoRH Type=5 | RPLInstanceID | SenderRank |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
I=0, K=1 I=0, K=1
Figure 11: Compressing SenderRank. Figure 12: Compressing SenderRank.
In Figure 12, the RPLInstanceID is not the Global RPLInstanceID 0, In Figure 13, the RPLInstanceID is not the Global RPLInstanceID 0,
and both bytes of the SenderRank are significant: and both bytes of the SenderRank are significant:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0|0|O|R|F|0|0| 6LoRH Type=5 | RPLInstanceID | Sender-... |1|0|0|O|R|F|0|0| 6LoRH Type=5 | RPLInstanceID | Sender-...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...-Rank | ...-Rank |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
I=0, K=0 I=0, K=0
Figure 12: Least compressed form of RPI-6LoRH. Figure 13: Least compressed form of RPI-6LoRH.
7. The IP-in-IP 6LoRH Header 7. The IP-in-IP 6LoRH Header
The IP-in-IP 6LoRH (IP-in-IP-6LoRH) header is an Elective 6LoWPAN The IP-in-IP 6LoRH (IP-in-IP-6LoRH) header is an Elective 6LoWPAN
Routing Header that provides a compressed form for the encapsulating Routing Header that provides a compressed form for the encapsulating
IPv6 Header in the case of an IP-in-IP encapsulation. IPv6 Header in the case of an IP-in-IP encapsulation.
An IP-in-IP encapsulation is used to insert a field such as a Routing An IP-in-IP encapsulation is used to insert a field such as a Routing
Header or an RPI at a router that is not the source of the packet. Header or an RPI at a router that is not the source of the packet.
In order to send an error back regarding the inserted field, the In order to send an error back regarding the inserted field, the
skipping to change at page 1, line 645 skipping to change at page 1, line 965
This field is not critical for routing so the Type can be ignored, This field is not critical for routing so the Type can be ignored,
and the TSE field contains the Length in bytes. and the TSE field contains the Length in bytes.
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 13: 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 [RFC2460] each hop. When the HL reaches 0, the packet is dropped per
[RFC2460].
If the Length of an IP-in-IP-6LoRH header is exactly 1, then the 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.
With this specification, an optimal compression of IP-in-IP
encapsulation can be achieved if an endpoint of the packet is the
root of the RPL DODAG associated to the Instance that is used to
forward the packet, and the root address is known implicitly as
opposed to signaled explicitly in the data packets.
If the Length of an IP-in-IP-6LoRH header is greater than 1, then an If the Length of an IP-in-IP-6LoRH header is greater than 1, then an
Encapsulator Address is placed in a compressed form after the Hop 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 Size of 3 performed on the Encapsulator Address. For instance, a Size 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
DODAG. The way the address of the root is determined is discussed in
Section 4.3.2.
When it cannot be elided, the destination IP address of the IP-in-IP When it cannot be elided, the destination IP address of the IP-in-IP
header is transported in a RH3-6LoRH header as the first address of header is transported in a RH3-6LoRH header as the first address of
the list. the list.
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
the destination address in the IPHC for packets going downwards. If the destination address in the IPHC for packets going downwards. If
the implicit value is correct, the destination IP address of the IP- the implicit value is correct, the destination IP address of the IP-
in-IP encapsulation can be elided. in-IP encapsulation can be elided.
skipping to change at page 16, line 5 skipping to change at page 23, line 5
9. IANA Considerations 9. 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.
9.2. Nex 6LoWPAN Routing Header Type Registry 9.2. New 6LoWPAN Routing Header Type Registry
This document creates an IANA registry for the 6LoWPAN Routing Header This document creates an IANA registry for the 6LoWPAN Routing Header
Type, and assigns the following values: Type, and assigns the following values:
0..4: RH3-6LoRH [RFCthis] 0..4: RH3-6LoRH [RFCthis]
5: RPI-6LoRH [RFCthis] 5: RPI-6LoRH [RFCthis]
6: IP-in-IP-6LoRH [RFCthis] 6: IP-in-IP-6LoRH [RFCthis]
skipping to change at page 16, line 43 skipping to change at page 23, line 43
Thubert, P., "6LoWPAN Paging Dispatch", draft-ietf-6lo- Thubert, P., "6LoWPAN Paging Dispatch", draft-ietf-6lo-
paging-dispatch-01 (work in progress), January 2016. paging-dispatch-01 (work in progress), January 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, DOI 10.17487/ Requirement Levels", BCP 14, RFC 2119,
RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>. December 1998, <http://www.rfc-editor.org/info/rfc2460>.
[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler, [RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
"Transmission of IPv6 Packets over IEEE 802.15.4 "Transmission of IPv6 Packets over IEEE 802.15.4
Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007, Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
<http://www.rfc-editor.org/info/rfc4944>. <http://www.rfc-editor.org/info/rfc4944>.
[RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
DOI 10.17487/RFC6282, September 2011, DOI 10.17487/RFC6282, September 2011,
<http://www.rfc-editor.org/info/rfc6282>. <http://www.rfc-editor.org/info/rfc6282>.
[RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550, DOI 10.17487/ Low-Power and Lossy Networks", RFC 6550,
RFC6550, March 2012, DOI 10.17487/RFC6550, March 2012,
<http://www.rfc-editor.org/info/rfc6550>. <http://www.rfc-editor.org/info/rfc6550>.
[RFC6552] Thubert, P., Ed., "Objective Function Zero for the Routing [RFC6552] Thubert, P., Ed., "Objective Function Zero for the Routing
Protocol for Low-Power and Lossy Networks (RPL)", RFC Protocol for Low-Power and Lossy Networks (RPL)",
6552, DOI 10.17487/RFC6552, March 2012, RFC 6552, DOI 10.17487/RFC6552, March 2012,
<http://www.rfc-editor.org/info/rfc6552>. <http://www.rfc-editor.org/info/rfc6552>.
[RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low- [RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low-
Power and Lossy Networks (RPL) Option for Carrying RPL Power and Lossy Networks (RPL) Option for Carrying RPL
Information in Data-Plane Datagrams", RFC 6553, DOI Information in Data-Plane Datagrams", RFC 6553,
10.17487/RFC6553, March 2012, DOI 10.17487/RFC6553, March 2012,
<http://www.rfc-editor.org/info/rfc6553>. <http://www.rfc-editor.org/info/rfc6553>.
[RFC6554] Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6 [RFC6554] Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6
Routing Header for Source Routes with the Routing Protocol Routing Header for Source Routes with the Routing Protocol
for Low-Power and Lossy Networks (RPL)", RFC 6554, DOI for Low-Power and Lossy Networks (RPL)", RFC 6554,
10.17487/RFC6554, March 2012, DOI 10.17487/RFC6554, March 2012,
<http://www.rfc-editor.org/info/rfc6554>. <http://www.rfc-editor.org/info/rfc6554>.
[RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and [RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and
Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January
2014, <http://www.rfc-editor.org/info/rfc7102>. 2014, <http://www.rfc-editor.org/info/rfc7102>.
[RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for [RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for
Constrained-Node Networks", RFC 7228, DOI 10.17487/ Constrained-Node Networks", RFC 7228,
RFC7228, May 2014, DOI 10.17487/RFC7228, May 2014,
<http://www.rfc-editor.org/info/rfc7228>. <http://www.rfc-editor.org/info/rfc7228>.
11.2. Informative References 11.2. Informative References
[I-D.ietf-6tisch-architecture] [I-D.ietf-6tisch-architecture]
Thubert, P., "An Architecture for IPv6 over the TSCH mode Thubert, P., "An Architecture for IPv6 over the TSCH mode
of IEEE 802.15.4", draft-ietf-6tisch-architecture-09 (work of IEEE 802.15.4", draft-ietf-6tisch-architecture-09 (work
in progress), November 2015. in progress), November 2015.
[I-D.robles-roll-useofrplinfo] [I-D.robles-roll-useofrplinfo]
skipping to change at page 18, line 22 skipping to change at page 25, line 22
RFC 6553, 6554 and IPv6-in-IPv6", draft-robles-roll- RFC 6553, 6554 and IPv6-in-IPv6", draft-robles-roll-
useofrplinfo-02 (work in progress), October 2015. useofrplinfo-02 (work in progress), October 2015.
[I-D.thubert-6lo-forwarding-fragments] [I-D.thubert-6lo-forwarding-fragments]
Thubert, P. and J. Hui, "LLN Fragment Forwarding and Thubert, P. and J. Hui, "LLN Fragment Forwarding and
Recovery", draft-thubert-6lo-forwarding-fragments-02 (work Recovery", draft-thubert-6lo-forwarding-fragments-02 (work
in progress), November 2014. in progress), November 2014.
[RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
Bormann, "Neighbor Discovery Optimization for IPv6 over Bormann, "Neighbor Discovery Optimization for IPv6 over
Low-Power Wireless Personal Area Networks (6LoWPANs)", RFC Low-Power Wireless Personal Area Networks (6LoWPANs)",
6775, DOI 10.17487/RFC6775, November 2012, RFC 6775, DOI 10.17487/RFC6775, November 2012,
<http://www.rfc-editor.org/info/rfc6775>. <http://www.rfc-editor.org/info/rfc6775>.
[RFC7554] Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using [RFC7554] Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using
IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the
Internet of Things (IoT): Problem Statement", RFC 7554, Internet of Things (IoT): Problem Statement", RFC 7554,
DOI 10.17487/RFC7554, May 2015, DOI 10.17487/RFC7554, May 2015,
<http://www.rfc-editor.org/info/rfc7554>. <http://www.rfc-editor.org/info/rfc7554>.
Appendix A. Examples Appendix A. Examples
The example in Figure 14 illustrates the 6LoRH compression of a A.1. Examples Compressing The RPI
The example in Figure 15 illustrates the 6LoRH compression of a
classical packet in Storing Mode in all directions, as well as in 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 [RFC4944], and the fragment
headers must be placed in Page 0 before switching to Page 1: headers must be placed in Page 0 before switching to Page 1:
+- ... -+- ... -+-+ ... -+-+ ... -+- ... +-+-+-+-+-+-+-+-+-+-+... +- ... -+- ... -+-+ ... -+- ... +-+-+ ... -+-+-+-+-+-+-+-+-+-+...
|Frag type|Frag hdr |11110001|IP-in-IP| RPI | RFC 6282 Dispatch |Frag type|Frag hdr |11110001| RPI- |IP-in-IP| LOWPAN-IPHC | ...
|RFC 4944 |RFC 4944 | Page 1 | 6LoRH | 6LoRH | + LOWPAN_IPHC |RFC 4944 |RFC 4944 | Page 1 | 6LoRH | 6LoRH | |
+- ... -+- ... -+-+ ... -+-+ ... -+- ... +-+-+-+-+-+-+-+-+-+-+... +- ... -+- ... -+-+ ... -+- ... +-+-+ ... -+-+-+-+-+-+-+-+-+-+...
<- RFC 6282 -> <- RFC 6282 ->
No RPL artifact No RPL artifact
Figure 14: Example Compressed Packet with RPI. Figure 15: Example Compressed Packet with RPI.
The example illustrated in Figure 15 is a classical packet in non- In Storing Mode, if the packet stays within the RPL domain, then it
is possible to save the IP-in-IP encapsulation, in which case only
the RPI is compressed with a 6LoRH, as illustrated in Figure 16 in
the case of a non-fragmented ICMP packet:
+- ... -+-+- ... -+-+-+-+ ... -+-+-+-+ ... -+-+-+-+-+-+-+-+-+-+-+...
|11110001| RPI-6LoRH | NH = 0 | NH = 58 | ICMP message ...
|Page 1 | type 5 | 6LOWPAN-IPHC | (ICMP) | (no compression)
+- ... -+-+- ... -+-+-+-+ ... -+-+-+-+ ... -+-+-+-+-+-+-+-+-+-+-+...
<- RFC 6282 ->
No RPL artifact
Figure 16: Example ICMP Packet with RPI in Storing Mode.
The format in Figure 16 is logically equivalent to the non-compressed
format illustrated in Figure 17:
+-+-+-+- ... -+-+-+-+ ... -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...
| IPv6 Header | Hop-by-Hop | RPI in | ICMP message ...
| NH = 58 | Header | RPL Option |
+-+-+-+- ... -+-+-+-+ ... -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...
Figure 17: Uncompressed ICMP Packet with RPI.
For a UDP packet, the transport header can be compressed with 6LoWPAN
HC [RFC6282] as illustrated in Figure 18:
+- ... -+- ... -+-+-+-+- ... +-+-+-+-+-+-+-+-+-+- ... +-+-+-+-+-+...
|11110001| RPI-6LoRH | NH = 1 |11110|C| P | Compressed |UDP ...
|Page 1 | type 5 | 6LOWPAN-IPHC | UDP | | | UDP header |Payload
+- ... -+- ... -+-+-+-+- ... +-+-+-+-+-+-+-+-+-+- ... +-+-+-+-+-+...
<- RFC 6282 ->
No RPL artifact
Figure 18: Uncompressed ICMP Packet with RPI.
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
resulting format would be as represented in Figure 19:
+-+-+-+-+-+-+- ... -+-+-- ... -+-+- ... -+-+-+-+-+-+-+ ... -+-+-+-+...
|11110001 | RPI-6LoRH | IP-in-IP | NH=1 |11110CPP| Compressed | UDP
|Page 1 | | 6LoRH | IPHC | UDP | UDP header | Payload
+-+-+-+-+-+-+- ... -+-+-- ... -+-+- ... -+-+-+-+-+-+-+ ... -+-+-+-+...
<- RFC 6282 ->
No RPL artifact
Figure 19: RPI inserted by the root in Storing Mode.
A.2. Example Of Downward Packet In Non-Storing Mode
The example illustrated in Figure 20 is a classical packet in non-
Storing mode for 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; in this particular example, addresses in routed path from the root. Say that we have 4 forwarding hops to
the DODAG are assigned to share a same /112 prefix, for instance reach a destination. In the non-compressed form, when the root
taken from a /64 subnet with the first 6 octets of the suffix set to generates the packet, the last 3 hops are encoded in a Routing Header
a constant such as all zeroes. In that case, all addresses but the type 3 (RH3) and the first hop is the destination of the packet. The
first can be compressed to 2 octets, which means that there will be 2 intermediate hops perform a swap and the hop count indicates the
RH3_6LoRH headers, one to store the first complete address and the current active hop [RFC2460], [RFC6554].
one to store the sequence of addresses compressed to 2 octets (in
this example, 3 of them):
+- ... -+- ... -+-+-+- ... -+-+-+-+-+ ... -+-+-+-+-+-+-+-+-+-+-+... When compressed with this specification, the 4 hops are encoded in
|11110001|IP-in-IP| RH3(128bits)| RH3(3*16bits)| RFC 6282 Dispatch RH3-6LoRH when the root generates the packet, and the final
|Page 1 | 6LoRH | 6LoRH | 6LoRH | + LOWPAN_IPHC destination is left in the LOWPAN-IPHC. There is no swap, and the
+- ... -+- ... +-+-+-+- ... -+-+-+-+-+ ... -+-+-+-+-+-+-+-+-+-+-+... forwarding node that corresponds to the first entry effectively
<- RFC 6282 -> consumes it when forwarding, which means that the size of the encoded
No RPL artifact packet decreases and that the hop information is lost.
Figure 15: Example Compressed Packet with RH3. If the last hop in a RH3-6LoRH is not the final destination then it
removes the RH3-6LoRH before forwarding.
Note: the RPI is not represented since most implementations actually In the particular example illustrated in Figure 20, all addresses in
refrain from placing it in a source routed packet though [RFC6550] the DODAG are assigned from a same /112 prefix and the last 2 octets
generally expects it. encoding an identifier such as a IEEE 802.15.4 short address. In
that case, all addresses can be compressed to 2 octets, using the
root address as reference. There will be one RH3_6LoRH header, with,
in this example, 3 compressed addresses:
+-+-+-+-+-+-+- ... +-+-+- ... -+-+-- ... -+-+- ... -+-+-+-+-+ ... +-...
|11110001 |RH3-6LoRH | RPI-6LoRH | IP-in-IP | NH=1 |11110CPP| UDP | UDP
|Page 1 |Type1 S=2 | | 6LoRH | IPHC | UDP | hdr |load
+-+-+-+-+-+-+- ... +-+-+- ... -+-+-- ... -+-+- ... -+-+-+-+-+ ... +-...
<-8bytes-> <- RFC 6282 ->
No RPL artifact
Figure 20: Example Compressed Packet with RH3.
One may note that the RPI is provided. This is because the address
of the root that is the source of the IP-in-IP header is elided and
inferred from the InstanceID in the RPI. Once found from a local
context, that address is used as Compression Reference to expand
addresses in the RH3-6LoRH.
With the RPL specifications available at the time of writing this
draft, the root is the only node that may incorporate a RH3 in an IP
packet. When the root forwards a packet that it did not generate, it
has to encapsulate the packet with IP-in-IP.
But if the root generates the packet towards a node in its DODAG,
then it should avoid the extra IP-in-IP as illustrated in Figure 21:
+- ... -+-+-+ ... +-+-+-+ ... -+-+-+-+-+-+-+-++-+- ... -+-+-+-+-+...
|11110001| RH3-6LoRH | NH=1 | 11110CPP | Compressed | UDP
|Page 1 | Type1 S=3 | LOWPAN-IPHC| LOWPAN-NHC| UDP header | Payload
+- ... -+-+-+ ... +-+-+-+ ... -+-+-+-+-+-+-+-++-+- ... -+-+-+-+-+...
<- RFC 6282 ->
Figure 21: compressed RH3 4*2bytes entries sourced by root.
Note: the RPI is not represented though RPL [RFC6550] generally
expects it. In this particular case, since the Compression Reference
for the RH3-6LoRH is the source address in the LOWPAN-IPHC, and the
routing is strict along the source route path, the RPI does not
appear to be absolutely necessary.
In Figure 21, all the nodes along the source route path share a same
/112 prefix. This is typical of IPv6 addresses derived from an
IEEE802.15.4 short address, as long as all the nodes share a same
PAN-ID. In that case, a type-1 RH3-6LoRH header can be used for
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
encoded. The Size of 3 indicates 4 hops, resulting in a RH3-6LoRH of
10 bytes.
A.3. Example of RH3-6LoRH life-cycle
This section illustrates the operation specified in Section 5.5 of
forwarding a packet with a compressed RH3 along an A->B->C->D source
route path. The operation of popping addresses is exemplified at
each hop.
Packet as received by node A
----------------------------
Type 3 RH3-6LoRH Size = 0 AAAA AAAA AAAA AAAA
Type 1 RH3-6LoRH Size = 0 BBBB
Type 2 RH3-6LoRH Size = 1 CCCC CCCC
DDDD DDDD
Step 1 popping BBBB the first entry of the next RH3-6LoRH
Step 2 next is if larger value (2 vs. 1) the RH3-6LoRH is removed
Type 3 RH3-6LoRH Size = 0 AAAA AAAA AAAA AAAA
Type 2 RH3-6LoRH Size = 1 CCCC CCCC
DDDD DDDD
Step 3: recursion ended, coalescing BBBB with the first entry
Type 3 RH3-6LoRH Size = 0 AAAA AAAA AAAA BBBB
Step 4: routing based on next segment endpoint to B
Figure 22: Processing at Node A.
Packet as received by node B
----------------------------
Type 3 RH3-6LoRH Size = 0 AAAA AAAA AAAA BBBB
Type 2 RH3-6LoRH Size = 1 CCCC CCCC
DDDD DDDD
Step 1 popping CCCC CCCC, the first entry of the next RH3-6LoRH
Step 2 removing the first entry and decrementing the Size (by 1)
Type 3 RH3-6LoRH Size = 0 AAAA AAAA AAAA BBBB
Type 2 RH3-6LoRH Size = 0 DDDD DDDD
Step 3: recursion ended, coalescing CCCC CCCC with the first entry
Type 3 RH3-6LoRH Size = 0 AAAA AAAA CCCC CCCC
Step 4: routing based on next segment endpoint to C
Figure 23: Processing at Node B.
Packet as received by node C
----------------------------
Type 3 RH3-6LoRH Size = 0 AAAA AAAA CCCC CCCC
Type 2 RH3-6LoRH Size = 0 DDDD DDDD
Step 1 popping DDDD DDDD, the first entry of the next RH3-6LoRH
Step 2 the RH3-6LoRH is removed
Type 3 RH3-6LoRH Size = 0 AAAA AAAA CCCC CCCC
Step 3: recursion ended, coalescing DDDD DDDDD with the first entry
Type 3 RH3-6LoRH Size = 0 AAAA AAAA DDDD DDDD
Step 4: routing based on next segment endpoint to D
Figure 24: Processing at Node C.
Packet as received by node D
----------------------------
Type 3 RH3-6LoRH Size = 0 AAAA AAAA DDDD DDDD
Step 1 the RH3-6LoRH is removed.
Step 2 no more header, routing based on inner IP header.
Figure 25: Processing at Node D.
Authors' Addresses Authors' Addresses
Pascal Thubert (editor) Pascal Thubert (editor)
Cisco Systems Cisco Systems
Building D - Regus Building D - Regus
45 Allee des Ormes 45 Allee des Ormes
BP1200 BP1200
MOUGINS - Sophia Antipolis 06254 MOUGINS - Sophia Antipolis 06254
FRANCE FRANCE
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