draft-ietf-6lowpan-hc-15.txt   rfc6282.txt 
Network Working Group J. Hui, Ed. Internet Engineering Task Force (IETF) J. Hui, Ed.
Internet-Draft Arch Rock Corporation Request for Comments: 6282 Arch Rock Corporation
Updates: 4944 (if approved) P. Thubert Updates: 4944 P. Thubert
Intended status: Standards Track Cisco Category: Standards Track Cisco
Expires: August 28, 2011 February 24, 2011 ISSN: 2070-1721 September 2011
Compression Format for IPv6 Datagrams in Low Power and Lossy Networks Compression Format for IPv6 Datagrams
(6LoWPAN) over IEEE 802.15.4-Based Networks
draft-ietf-6lowpan-hc-15
Abstract Abstract
This document updates RFC 4944, "Transmission of IPv6 Packets over This document updates RFC 4944, "Transmission of IPv6 Packets over
IEEE 802.15.4 Networks". This document specifies an IPv6 header IEEE 802.15.4 Networks". This document specifies an IPv6 header
compression format for IPv6 packet delivery in Low Power and Lossy compression format for IPv6 packet delivery in Low Power Wireless
Networks (6LoWPANs). The compression format relies on shared context Personal Area Networks (6LoWPANs). The compression format relies on
to allow compression of arbitrary prefixes. How the information is shared context to allow compression of arbitrary prefixes. How the
maintained in that shared context is out of scope. This document information is maintained in that shared context is out of scope.
specifies compression of multicast addresses and a framework for This document specifies compression of multicast addresses and a
compressing next headers. UDP header compression is specified within framework for compressing next headers. UDP header compression is
this framework. specified within this framework.
Status of this Memo
This Internet-Draft is submitted in full conformance with the Status of This Memo
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering This is an Internet Standards Track document.
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
This Internet-Draft will expire on August 28, 2011. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6282.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2011 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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction ....................................................3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 1.1. Requirements Language ......................................4
2. Specific Updates to RFC 4944 . . . . . . . . . . . . . . . . . 4 2. Specific Updates to RFC 4944 ....................................4
3. IPv6 Header Compression . . . . . . . . . . . . . . . . . . . 5 3. IPv6 Header Compression .........................................5
3.1. LOWPAN_IPHC Encoding Format . . . . . . . . . . . . . . . 6 3.1. LOWPAN_IPHC Encoding Format ................................6
3.1.1. Base Format . . . . . . . . . . . . . . . . . . . . . 6 3.1.1. Base Format .........................................6
3.1.2. Context Identifier Extension . . . . . . . . . . . . . 9 3.1.2. Context Identifier Extension .......................10
3.2. IPv6 Header Encoding . . . . . . . . . . . . . . . . . . . 10 3.2. IPv6 Header Encoding ......................................11
3.2.1. Traffic Class and Flow Label Compression . . . . . . . 10 3.2.1. Traffic Class and Flow Label Compression ...........11
3.2.2. Deriving IIDs from the Encapsulating Header . . . . . 11 3.2.2. Deriving IIDs from the Encapsulating Header ........12
3.2.3. Stateless Multicast Address Compression . . . . . . . 12 3.2.3. Stateless Multicast Address Compression ............13
3.2.4. Stateful Multicast Address Compression . . . . . . . . 13 3.2.4. Stateful Multicast Address Compression .............14
4. IPv6 Next Header Compression . . . . . . . . . . . . . . . . . 14 4. IPv6 Next Header Compression ...................................15
4.1. LOWPAN_NHC Format . . . . . . . . . . . . . . . . . . . . 14 4.1. LOWPAN_NHC Format .........................................15
4.2. IPv6 Extension Header Compression . . . . . . . . . . . . 15 4.2. IPv6 Extension Header Compression .........................15
4.3. UDP Header Compression . . . . . . . . . . . . . . . . . . 16 4.3. UDP Header Compression ....................................17
4.3.1. Compressing UDP ports . . . . . . . . . . . . . . . . 17 4.3.1. Compressing UDP Ports ..............................17
4.3.2. Compressing UDP checksum . . . . . . . . . . . . . . . 17 4.3.2. Compressing UDP Checksum ...........................18
4.3.3. UDP LOWPAN_NHC Format . . . . . . . . . . . . . . . . 19 4.3.3. UDP LOWPAN_NHC Format ..............................20
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 5. IANA Considerations ............................................20
6. Security Considerations . . . . . . . . . . . . . . . . . . . 20 6. Security Considerations ........................................21
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 21 7. Acknowledgements ...............................................22
8. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 8. References .....................................................22
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23 8.1. Normative References ......................................22
9.1. Normative References . . . . . . . . . . . . . . . . . . . 23 8.2. Informative References ....................................23
9.2. Informative References . . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25
1. Introduction 1. Introduction
The [IEEE 802.15.4] standard specifies an MTU of 127 bytes, yielding The [IEEE802.15.4] standard specifies an MTU of 127 bytes, yielding
about 80 octets of actual Media Access Control (MAC) payload with about 80 octets of actual Media Access Control (MAC) payload with
security enabled, on a wireless link with a link throughput of 250 security enabled, on a wireless link with a link throughput of 250
kbps or less. The 6LoWPAN adaptation format [RFC4944] was specified kbps or less. The 6LoWPAN adaptation format [RFC4944] was specified
to carry IPv6 datagrams over such constrained links, taking into to carry IPv6 datagrams over such constrained links, taking into
account limited bandwidth, memory, or energy resources that are account limited bandwidth, memory, or energy resources that are
expected in applications such as wireless sensor networks. [RFC4944] expected in applications such as wireless sensor networks. [RFC4944]
defines a Mesh Addressing header to support sub-IP forwarding, a defines a Mesh Addressing header to support sub-IP forwarding, a
Fragmentation header to support the IPv6 minimum MTU requirement Fragmentation header to support the IPv6 minimum MTU requirement
[RFC2460], and stateless header compression for IPv6 datagrams [RFC2460], and stateless header compression for IPv6 datagrams
(LOWPAN_HC1 and LOWPAN_HC2) to reduce the relatively large IPv6 and (LOWPAN_HC1 and LOWPAN_HC2) to reduce the relatively large IPv6 and
UDP headers down to (in the best case) several bytes. UDP headers down to (in the best case) several bytes.
LOWPAN_HC1 and LOWPAN_HC2 are insufficient for most practical uses of LOWPAN_HC1 and LOWPAN_HC2 are insufficient for most practical uses of
IPv6 in Low Power and Lossy Networks (6LoWPANs). LOWPAN_HC1 is most IPv6 in 6LoWPANs. LOWPAN_HC1 is most effective for link-local
effective for link-local unicast communication, where IPv6 addresses unicast communication, where IPv6 addresses carry the link-local
carry the link-local prefix and an Interface Identifier (IID) prefix and an Interface Identifier (IID) directly derived from IEEE
directly derived from IEEE 802.15.4 addresses. In this case, both 802.15.4 addresses. In this case, both addresses may be completely
addresses may be completely elided. However, though link-local elided. However, though link-local addresses are commonly used for
addresses are commonly used for local protocol interactions such as local protocol interactions such as IPv6 Neighbor Discovery
IPv6 Neighbor Discovery [RFC4861], DHCPv6 [RFC3315] or routing [RFC4861], DHCPv6 [RFC3315], or routing protocols, they are usually
protocols, they are usually not used for application-layer data not used for application-layer data traffic, so the actual value of
traffic, so the actual value of this compression mechanism is this compression mechanism is limited.
limited.
Routable addresses must be used when communicating with devices Routable addresses must be used when communicating with devices
external to the 6LoWPAN or in a route-over configuration where IP external to the 6LoWPAN or in a route-over configuration where IP
forwarding occurs within the 6LoWPAN. For routable addresses, forwarding occurs within the 6LoWPAN. For routable addresses,
LOWPAN_HC1 requires both IPv6 source and destination addresses to LOWPAN_HC1 requires both IPv6 source and destination addresses to
carry the prefix in-line. In cases where the Mesh Addressing header carry the prefix in-line. In cases where the Mesh Addressing header
is not used, the IID of a routable address must be carried in-line. is not used, the IID of a routable address must be carried in-line.
However, LOWPAN_HC1 requires 64-bits for the IID when carried in-line However, LOWPAN_HC1 requires 64 bits for the IID when carried in-line
and cannot be shortened even when it is derived from the IEEE and cannot be shortened even when it is derived from the IEEE
802.15.4 16-bit short address. When the destination is an IPv6 802.15.4 16-bit short address. When the destination is an IPv6
multicast address, LOWPAN_HC1 requires the full 128-bit address to be multicast address, LOWPAN_HC1 requires the full 128-bit address to be
carried in-line. carried in-line.
As a result, this document defines an encoding format, LOWPAN_IPHC, As a result, this document defines an encoding format, LOWPAN_IPHC,
for effective compression of Unique Local, Global, and multicast IPv6 for effective compression of Unique Local, Global, and multicast IPv6
Addresses based on shared state within contexts. In addition, this Addresses based on shared state within contexts. In addition, this
document also introduces a number of additional improvements over the document also introduces a number of additional improvements over the
header compression format defined in [RFC4944]. header compression format defined in [RFC4944].
LOWPAN_IPHC allows for compression of some commonly-used IPv6 Hop LOWPAN_IPHC allows for compression of some commonly used IPv6 Hop
Limit values. If the 6LoWPAN is a mesh-under stub, a Hop Limit of 1 Limit values. If the 6LoWPAN is a mesh-under stub, a Hop Limit of 1
for inbound and a default value such as 64 for outbound are usually for inbound and a default value such as 64 for outbound are usually
enough for application layer data traffic. Additionally, a hop-limit enough for application-layer data traffic. Additionally, a Hop Limit
value of 255 is often used to verify that a communication occurs over value of 255 is often used to verify that a communication occurs over
a single-hop. This specification enables compression of the IPv6 Hop a single-hop. This specification enables compression of the IPv6 Hop
Limit field in those common cases, whereas LOWPAN_HC1 does not. Limit field in those common cases, whereas LOWPAN_HC1 does not.
This document also defines LOWPAN_NHC, an encoding format for This document also defines LOWPAN_NHC, an encoding format for
arbitrary next headers. LOWPAN_IPHC indicates whether the following arbitrary next headers. LOWPAN_IPHC indicates whether the following
header is encoded using LOWPAN_NHC. If so, the bits immediately header is encoded using LOWPAN_NHC. If so, the bits immediately
following the compressed IPv6 header start the LOWPAN_NHC encoding. following the compressed IPv6 header start the LOWPAN_NHC encoding.
In contrast, LOWPAN_HC1 could be extended to support compression of In contrast, LOWPAN_HC1 could be extended to support compression of
next headers using LOWPAN_HC2, but only for UDP, TCP, and ICMPv6. next headers using LOWPAN_HC2, but only for UDP, TCP, and ICMPv6.
Furthermore, the LOWPAN_HC2 octet sits between the LOWPAN_HC1 octet Furthermore, the LOWPAN_HC2 octet sits between the LOWPAN_HC1 octet
and uncompressed IPv6 header fields. This specification moves the and uncompressed IPv6 header fields. This specification moves the
next header encoding bits to follow all IPv6-related bits, allowing next header encoding bits to follow all IPv6-related bits, allowing
for a properly layered structure and direct support for IPv6 for a properly layered structure and direct support for IPv6
extension headers. extension headers.
Using LOWPAN_NHC, this document defines a compression mechanism for Using LOWPAN_NHC, this document defines a compression mechanism for
UDP. While [RFC4944] defines a compression mechanism for UDP, that UDP. While [RFC4944] defines a compression mechanism for UDP, that
mechanism does not enable checksum compression when rendered possible mechanism does not enable checksum compression when rendered possible
by additional upper layer mechanisms such as upper layer Message by additional upper-layer mechanisms such as upper-layer Message
Integrity Check (MIC). This specification adds the capability to Integrity Check (MIC). This specification adds the capability to
elide the UDP checksum over the 6LoWPAN, which enables saving of a elide the UDP checksum over the 6LoWPAN, which enables saving of a
further two octets. further two octets.
Also using LOWPAN_NHC, this document defines encoding formats for Also, using LOWPAN_NHC, this document defines encoding formats for
IPv6-in-IPv6 encapsulation as well as IPv6 Extension Headers. With IPv6-in-IPv6 encapsulation as well as IPv6 Extension Headers. With
LOWPAN_HC1 and LOWPAN_HC2, chains of next headers cannot be encoded LOWPAN_HC1 and LOWPAN_HC2, chains of next headers cannot be encoded
efficiently. efficiently.
1.1. Requirements Language 1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
2. Specific Updates to RFC 4944 2. Specific Updates to RFC 4944
This document specifies a header compression format that is intended This document specifies a header compression format that is intended
to replace that defined in Section 10 of [RFC4944]. Implementation to replace that defined in Section 10 of [RFC4944]. Implementation
of Section 10 of [RFC4944] is now NOT RECOMMENDED. New of Section 10 of [RFC4944] is now NOT RECOMMENDED. New
implementations MAY implement decompression according to Section 10 implementations MAY implement decompression according to Section 10
of [RFC4944], but SHOULD NOT send packets compressed according to of [RFC4944] but SHOULD NOT send packets compressed according to
Section 10 of [RFC4944]. Section 10 of [RFC4944].
A compliant implementation of [RFC4944] as updated by this document A compliant implementation of [RFC4944] as updated by this document
MUST be able to properly process a packet received that makes use of MUST be able to properly process a packet received that makes use of
the provisions of this document. A compliant implementation MAY the provisions of this document. A compliant implementation MAY
implement additional LOWPAN_NHC types (Section 4) that may be implement additional LOWPAN_NHC types (Section 4) that may be
registered (Section 5) in the future. It is out of scope of this registered (Section 5) in the future. It is out of scope of this
document how a compressor learns that a decompressor has additional document how a compressor learns that a decompressor has additional
capabilities. capabilities.
skipping to change at page 5, line 29 skipping to change at page 5, line 27
fragment MUST NOT be compressed. fragment MUST NOT be compressed.
The header compression format defined in this document preempts the The header compression format defined in this document preempts the
ESC dispatch value defined in Section 5.1 of [RFC4944]. Instead, the ESC dispatch value defined in Section 5.1 of [RFC4944]. Instead, the
value of 01 000000 is reserved as a replacement value for ESC, to be value of 01 000000 is reserved as a replacement value for ESC, to be
finally assigned with the first assignment of extension bytes. finally assigned with the first assignment of extension bytes.
3. IPv6 Header Compression 3. IPv6 Header Compression
In this section, we define the LOWPAN_IPHC encoding format for In this section, we define the LOWPAN_IPHC encoding format for
compressing the IPv6 header. To enable effective compression compressing the IPv6 header. To enable effective compression,
LOWPAN_IPHC relies on information pertaining to the entire 6LoWPAN. LOWPAN_IPHC relies on information pertaining to the entire 6LoWPAN.
LOWPAN_IPHC assumes the following will be the common case for 6LoWPAN LOWPAN_IPHC assumes the following will be the common case for 6LoWPAN
communication: Version is 6; Traffic Class and Flow Label are both communication: Version is 6; Traffic Class and Flow Label are both
zero; Payload Length can be inferred from lower layers from either zero; Payload Length can be inferred from lower layers from either
the 6LoWPAN Fragmentation header or the IEEE 802.15.4 header; Hop the 6LoWPAN Fragmentation header or the IEEE 802.15.4 header; Hop
Limit will be set to a well-known value by the source; addresses Limit will be set to a well-known value by the source; addresses
assigned to 6LoWPAN interfaces will be formed using the link-local assigned to 6LoWPAN interfaces will be formed using the link-local
prefix or a small set of routable prefixes assigned to the entire prefix or a small set of routable prefixes assigned to the entire
6LoWPAN; addresses assigned to 6LoWPAN interfaces are formed with an 6LoWPAN; addresses assigned to 6LoWPAN interfaces are formed with an
IID derived directly from either the 64-bit extended or 16-bit short IID derived directly from either the 64-bit extended or the 16-bit
IEEE 802.15.4 addresses. short IEEE 802.15.4 addresses.
+-------------------------------------+---------------------------- +-------------------------------------+----------------------------
| Dispatch + LOWPAN_IPHC (2-3 octets) | In-line IPv6 Header Fields | Dispatch + LOWPAN_IPHC (2-3 octets) | In-line IPv6 Header Fields
+-------------------------------------+---------------------------- +-------------------------------------+----------------------------
Figure 1: LOWPAN_IPHC Header Figure 1: LOWPAN_IPHC Header
The LOWPAN_IPHC encoding utilizes 13 bits, 5 of which are taken from The LOWPAN_IPHC encoding utilizes 13 bits, 5 of which are taken from
the rightmost bits of the dispatch type. The encoding may be the rightmost bits of the dispatch type. The encoding may be
extended by another octet to support additional contexts. Any extended by another octet to support additional contexts. Any
skipping to change at page 6, line 19 skipping to change at page 6, line 16
(the dispatch octet and the LOWPAN_IPHC encoding) with link-local (the dispatch octet and the LOWPAN_IPHC encoding) with link-local
communication. communication.
When routing over multiple IP hops, LOWPAN_IPHC can compress the IPv6 When routing over multiple IP hops, LOWPAN_IPHC can compress the IPv6
header down to 7 octets (1-octet dispatch, 1-octet LOWPAN_IPHC, header down to 7 octets (1-octet dispatch, 1-octet LOWPAN_IPHC,
1-octet Hop Limit, 2-octet Source Address, and 2-octet Destination 1-octet Hop Limit, 2-octet Source Address, and 2-octet Destination
Address). The Hop Limit may not be compressed because it needs to Address). The Hop Limit may not be compressed because it needs to
decremented at each hop and may take any value. Stateful address decremented at each hop and may take any value. Stateful address
compression must be applied to the source and destination IPv6 compression must be applied to the source and destination IPv6
addresses because they do not statelessly match the source and addresses because they do not statelessly match the source and
destination link layer addresses on intermediate hops. destination link-layer addresses on intermediate hops.
3.1. LOWPAN_IPHC Encoding Format 3.1. LOWPAN_IPHC Encoding Format
This section specifies the format of the LOWPAN_IPHC encoding that This section specifies the format of the LOWPAN_IPHC encoding that
describes how an IPv6 header is compressed. The encoding can be 2 describes how an IPv6 header is compressed. The encoding can be 2
octets long for the base encoding or 3 octets long when an additional octets long for the base encoding or 3 octets long when an additional
context encoding is present. The IPv6 header fields that are not context encoding is present. The IPv6 header fields that are not
fully elided are placed immediately after the LOWPAN_IPHC, either in fully elided are placed immediately after the LOWPAN_IPHC, either in
a compressed form if the field is partially elided, or literally. a compressed form if the field is partially elided or literally.
3.1.1. Base Format 3.1.1. Base Format
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 2: LOWPAN_IPHC base Encoding Figure 2: LOWPAN_IPHC base Encoding
skipping to change at page 6, line 44 skipping to change at page 6, line 41
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| 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 2: LOWPAN_IPHC base Encoding Figure 2: LOWPAN_IPHC base Encoding
TF: Traffic Class, Flow Label: As specified in [RFC3168], the 8-bit TF: Traffic Class, Flow Label: As specified in [RFC3168], the 8-bit
IPv6 Traffic Class field is split into two fields: 2-bit Explicit IPv6 Traffic Class field is split into two fields: 2-bit Explicit
Congestion Notification (ECN) and 6-bit Differentiated Services Congestion Notification (ECN) and 6-bit Differentiated Services
Code Point (DSCP). Code Point (DSCP).
00: ECN + DSCP + 4-bit Pad + Flow Label (4 bytes) 00: ECN + DSCP + 4-bit Pad + Flow Label (4 bytes)
01: ECN + 2-bit Pad + Flow Label (3 bytes), DSCP is elided
10: ECN + DSCP (1 byte), Flow Label is elided 01: ECN + 2-bit Pad + Flow Label (3 bytes), DSCP is elided.
10: ECN + DSCP (1 byte), Flow Label is elided.
11: Traffic Class and Flow Label are elided. 11: Traffic Class and Flow Label are elided.
NH: Next Header: NH: Next Header:
0: Full 8 bits for Next Header are carried in-line. 0: Full 8 bits for Next Header are carried in-line.
1: The Next Header field is compressed and the next header is 1: The Next Header field is compressed and the next header is
encoded using LOWPAN_NHC, which is discussed in Section 4.1. encoded using LOWPAN_NHC, which is discussed in Section 4.1.
HLIM: Hop Limit: HLIM: Hop Limit:
00: The Hop Limit field is carried in-line. 00: The Hop Limit field is carried in-line.
01: The Hop Limit field is compressed and the hop limit is 1. 01: The Hop Limit field is compressed and the hop limit is 1.
10: The Hop Limit field is compressed and the hop limit is 64. 10: The Hop Limit field is compressed and the hop limit is 64.
11: The Hop Limit field is compressed and the hop limit is 255. 11: The Hop Limit field is compressed and the hop limit is 255.
CID: Context Identifier Extension: CID: Context Identifier Extension:
0: No additional 8-bit Context Identifier Extension is used. If 0: No additional 8-bit Context Identifier Extension is used. If
context-based compression is specified in either SAC or DAC, context-based compression is specified in either Source Address
Compression (SAC) or Destination Address Compression (DAC),
context 0 is used. context 0 is used.
1: An additional 8-bit Context Identifier Extension field 1: An additional 8-bit Context Identifier Extension field
immediately follows the DAM field. immediately follows the Destination Address Mode (DAM) field.
SAC: Source Address Compression SAC: Source Address Compression
0: Source address compression uses stateless compression. 0: Source address compression uses stateless compression.
1: Source address compression uses stateful, context-based 1: Source address compression uses stateful, context-based
compression. compression.
SAM: Source Address Mode: SAM: Source Address Mode:
If SAC=0: If SAC=0:
00: 128 bits. The full address is carried in-line. 00: 128 bits. The full address is carried in-line.
01: 64 bits. The first 64-bits of the address are elided. 01: 64 bits. The first 64-bits of the address are elided.
The value of those bits is the link-local prefix padded with The value of those bits is the link-local prefix padded with
zeros. The remaining 64 bits are carried in-line. zeros. The remaining 64 bits are carried in-line.
10: 16 bits. The first 112 bits of the address are elided. 10: 16 bits. The first 112 bits of the address are elided.
The value of the first 64 bits is the link-local prefix The value of the first 64 bits is the link-local prefix
padded with zeros. The following 64 bits are 0000:00ff: padded with zeros. The following 64 bits are 0000:00ff:
fe00:XXXX, where XXXX are the 16 bits carried in-line. fe00:XXXX, where XXXX are the 16 bits carried in-line.
11: 0 bits. The address is fully elided. The first 64 bits 11: 0 bits. The address is fully elided. The first 64 bits
of the address are the link-local prefix padded with zeros. of the address are the link-local prefix padded with zeros.
The remaining 64 bits are computed from the encapsulating The remaining 64 bits are computed from the encapsulating
header (e.g. 802.15.4 or IPv6 source address) as specified header (e.g., 802.15.4 or IPv6 source address) as specified
in Section 3.2.2. in Section 3.2.2.
If SAC=1: If SAC=1:
00: The UNSPECIFIED address, :: 00: The UNSPECIFIED address, ::
01: 64 bits. The address is derived using context information 01: 64 bits. The address is derived using context information
and the 64 bits carried in-line. Bits covered by context and the 64 bits carried in-line. Bits covered by context
information are always used. Any IID bits not covered by information are always used. Any IID bits not covered by
context information are taken directly from the context information are taken directly from the
corresponding bits carried in-line. Any remaining bits are corresponding bits carried in-line. Any remaining bits are
zero. zero.
10: 16 bits. The address is derived using context information 10: 16 bits. The address is derived using context information
and the 16 bits carried in-line. Bits covered by context and the 16 bits carried in-line. Bits covered by context
information are always used. Any IID bits not covered by information are always used. Any IID bits not covered by
skipping to change at page 8, line 12 skipping to change at page 8, line 34
corresponding bits carried in-line. Any remaining bits are corresponding bits carried in-line. Any remaining bits are
zero. zero.
10: 16 bits. The address is derived using context information 10: 16 bits. The address is derived using context information
and the 16 bits carried in-line. Bits covered by context and the 16 bits carried in-line. Bits covered by context
information are always used. Any IID bits not covered by information are always used. Any IID bits not covered by
context information are taken directly from their context information are taken directly from their
corresponding bits in the 16-bit to IID mapping given by corresponding bits in the 16-bit to IID mapping given by
0000:00ff:fe00:XXXX, where XXXX are the 16 bits carried in- 0000:00ff:fe00:XXXX, where XXXX are the 16 bits carried in-
line. Any remaining bits are zero. line. Any remaining bits are zero.
11: 0 bits. The address is fully elided and is derived using 11: 0 bits. The address is fully elided and is derived using
context information and the encapsulating header (e.g. context information and the encapsulating header (e.g.,
802.15.4 or IPv6 source address). Bits covered by context 802.15.4 or IPv6 source address). Bits covered by context
information are always used. Any IID bits not covered by information are always used. Any IID bits not covered by
context information are computed from the encapsulating context information are computed from the encapsulating
header as specified in Section 3.2.2. Any remaining bits header as specified in Section 3.2.2. Any remaining bits
are zero. are zero.
M: Multicast Compression M: Multicast Compression
0: Destination address is not a multicast address. 0: Destination address is not a multicast address.
1: Destination address is a multicast address. 1: Destination address is a multicast address.
DAC: Destination Address Compression DAC: Destination Address Compression
0: Destination address compression uses stateless compression. 0: Destination address compression uses stateless compression.
1: Destination address compression uses stateful, context-based 1: Destination address compression uses stateful, context-based
compression. compression.
DAM: Destination Address Mode: DAM: Destination Address Mode:
If M=0 and DAC=0 This case matches SAC=0 but for the destination If M=0 and DAC=0 This case matches SAC=0 but for the destination
address: address:
00: 128 bits. The full address is carried in-line. 00: 128 bits. The full address is carried in-line.
01: 64 bits. The first 64-bits of the address are elided. 01: 64 bits. The first 64-bits of the address are elided.
The value of those bits is the link-local prefix padded with The value of those bits is the link-local prefix padded with
zeros. The remaining 64 bits are carried in-line. zeros. The remaining 64 bits are carried in-line.
10: 16 bits. The first 112 bits of the address are elided. 10: 16 bits. The first 112 bits of the address are elided.
The value of the first 64 bits is the link-local prefix The value of the first 64 bits is the link-local prefix
padded with zeros. The following 64 bits are 0000:00ff: padded with zeros. The following 64 bits are 0000:00ff:
fe00:XXXX, where XXXX are the 16 bits carried in-line. fe00:XXXX, where XXXX are the 16 bits carried in-line.
11: 0 bits. The address is fully elided. The first 64 bits 11: 0 bits. The address is fully elided. The first 64 bits
of the address are the link-local prefix padded with zeros. of the address are the link-local prefix padded with zeros.
The remaining 64 bits are computed from the encapsulating The remaining 64 bits are computed from the encapsulating
header (e.g. 802.15.4 or IPv6 destination address) as header (e.g., 802.15.4 or IPv6 destination address) as
specified in Section 3.2.2. specified in Section 3.2.2.
If M=0 and DAC=1: If M=0 and DAC=1:
00: Reserved. 00: Reserved.
01: 64 bits. The address is derived using context information 01: 64 bits. The address is derived using context information
and the 64 bits carried in-line. Bits covered by context and the 64 bits carried in-line. Bits covered by context
information are always used. Any IID bits not covered by information are always used. Any IID bits not covered by
context information are taken directly from the context information are taken directly from the
corresponding bits carried in-line. Any remaining bits are corresponding bits carried in-line. Any remaining bits are
zero. zero.
10: 16 bits. The address is derived using context information 10: 16 bits. The address is derived using context information
and the 16 bits carried in-line. Bits covered by context and the 16 bits carried in-line. Bits covered by context
information are always used. Any IID bits not covered by information are always used. Any IID bits not covered by
skipping to change at page 9, line 12 skipping to change at page 10, line 4
corresponding bits carried in-line. Any remaining bits are corresponding bits carried in-line. Any remaining bits are
zero. zero.
10: 16 bits. The address is derived using context information 10: 16 bits. The address is derived using context information
and the 16 bits carried in-line. Bits covered by context and the 16 bits carried in-line. Bits covered by context
information are always used. Any IID bits not covered by information are always used. Any IID bits not covered by
context information are taken directly from their context information are taken directly from their
corresponding bits in the 16-bit to IID mapping given by corresponding bits in the 16-bit to IID mapping given by
0000:00ff:fe00:XXXX, where XXXX are the 16 bits carried in- 0000:00ff:fe00:XXXX, where XXXX are the 16 bits carried in-
line. Any remaining bits are zero. line. Any remaining bits are zero.
11: 0 bits. The address is fully elided and is derived using 11: 0 bits. The address is fully elided and is derived using
context information and the encapsulating header (e.g. context information and the encapsulating header (e.g.
802.15.4 or IPv6 destination address). Bits covered by 802.15.4 or IPv6 destination address). Bits covered by
context information are always used. Any IID bits not context information are always used. Any IID bits not
covered by context information are computed from the covered by context information are computed from the
encapsulating header as specified in Section 3.2.2. Any encapsulating header as specified in Section 3.2.2. Any
remaining bits are zero. remaining bits are zero.
If M=1 and DAC=0: If M=1 and DAC=0:
00: 128 bits. The full address is carried in-line. 00: 128 bits. The full address is carried in-line.
01: 48 bits. The address takes the form FFXX::00XX:XXXX:XXXX.
10: 32 bits. The address takes the form FFXX::00XX:XXXX. 01: 48 bits. The address takes the form ffXX::00XX:XXXX:XXXX.
11: 8 bits. The address takes the form FF02::00XX.
10: 32 bits. The address takes the form ffXX::00XX:XXXX.
11: 8 bits. The address takes the form ff02::00XX.
If M=1 and DAC=1: If M=1 and DAC=1:
00: 48 bits. This format is designed to match Unicast-Prefix- 00: 48 bits. This format is designed to match Unicast-Prefix-
based IPv6 Multicast Addresses as defined in [RFC3306] and based IPv6 Multicast Addresses as defined in [RFC3306] and
[RFC3956]. The multicast address takes the form FFXX:XXLL: [RFC3956]. The multicast address takes the form ffXX:XXLL:
PPPP:PPPP:PPPP:PPPP:XXXX:XXXX. where the X are the nibbles PPPP:PPPP:PPPP:PPPP:XXXX:XXXX. where the X are the nibbles
that are carried in-line, in the order in which they appear that are carried in-line, in the order in which they appear
in this format. P denotes nibbles used to encode the prefix in this format. P denotes nibbles used to encode the prefix
itself. L denotes nibbles used to encode the prefix length. itself. L denotes nibbles used to encode the prefix length.
The prefix information P and L is taken from the specified The prefix information P and L is taken from the specified
context. context.
01: reserved 01: reserved
10: reserved 10: reserved
11: reserved 11: reserved
3.1.2. Context Identifier Extension 3.1.2. Context Identifier Extension
This specification expects that a conceptual context is shared This specification expects that a conceptual context is shared
between the node that compresses a packet and the node(s) that need between the node that compresses a packet and the node(s) that needs
to expand it. How the contexts are shared and maintained is out of to expand it. How the contexts are shared and maintained is out of
scope. What information is contained within a context information is scope. What information is contained within a context information is
out of scope. Actions in response to unknown and/or invalid contexts out of scope. Actions in response to unknown and/or invalid contexts
are out of scope. The specification enables a node to use up to 16 are out of scope. The specification enables a node to use up to 16
contexts. The context used to encode the source address does not contexts. The context used to encode the source address does not
have to be the same as the context used to encode the destination have to be the same as the context used to encode the destination
address. address.
If the CID field is set to '1' in the LOWPAN_IPHC encoding, then an If the CID field is set to '1' in the LOWPAN_IPHC encoding, then an
additional octet extends the LOWPAN_IPHC encoding following the DAM additional octet extends the LOWPAN_IPHC encoding following the DAM
skipping to change at page 10, line 16 skipping to change at page 11, line 20
identifier is 4 bits for each address, supporting up to 16 contexts. identifier is 4 bits for each address, supporting up to 16 contexts.
Context 0 is the default context. The encoding is shown in Figure 3. Context 0 is the default context. The encoding is shown in Figure 3.
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
| SCI | DCI | | SCI | DCI |
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
Figure 3: LOWPAN_IPHC Encoding Figure 3: LOWPAN_IPHC Encoding
SCI: Source Context Identifier Identifies the prefix that is used SCI: Source Context Identifier. Identifies the prefix that is used
when the IPv6 source address is statefully compressed. when the IPv6 source address is statefully compressed.
DCI: Destination Context Identifier Identifies the prefix that is
DCI: Destination Context Identifier. Identifies the prefix that is
used when the IPv6 destination address is statefully compressed. used when the IPv6 destination address is statefully compressed.
3.2. IPv6 Header Encoding 3.2. IPv6 Header Encoding
Fields carried in-line (in part or in whole) appear in the same order Fields carried in-line (in part or in whole) appear in the same order
as they do in the IPv6 header format [RFC2460]. The Version field is as they do in the IPv6 header format [RFC2460]. The Version field is
always elided. Unicast IPv6 addresses may be compressed to 64 or 16 always elided. Unicast IPv6 addresses may be compressed to 64 or 16
bits or completely elided. Multicast IPv6 addresses may be bits or completely elided. Multicast IPv6 addresses may be
compressed to 8, 32, or 48 bits. The IPv6 Payload Length field MUST compressed to 8, 32, or 48 bits. The IPv6 Payload Length field MUST
always be elided and inferred from lower layers using the 6LoWPAN always be elided and inferred from lower layers using the 6LoWPAN
Fragmentation header or the IEEE 802.15.4 header. Fragmentation header or the IEEE 802.15.4 header.
3.2.1. Traffic Class and Flow Label Compression 3.2.1. Traffic Class and Flow Label Compression
The Traffic Class field in the IPv6 header comprises 6 bits of The Traffic Class field in the IPv6 header comprises 6 bits of
diffserv extension [RFC2474] and 2 bits of Explicit Congestion Diffserv extension [RFC2474] and 2 bits of Explicit Congestion
Notification (ECN) [RFC3168]. The TF field in the LOWPAN_IPHC Notification (ECN) [RFC3168]. The TF field in the LOWPAN_IPHC
encoding indicates whether the Traffic Class and Flow Label are encoding indicates whether the Traffic Class and Flow Label are
carried in-line in the compressed IPv6 header. When Flow Label is carried in-line in the compressed IPv6 header. When Flow Label is
included while the Traffic Class is compressed, an additional 4 bits included while the Traffic Class is compressed, an additional 4 bits
are included to maintain byte-alignment. Two of the 4 bits contain are included to maintain byte alignment. Two of the 4 bits contain
the ECN bits from the Traffic Class field. the ECN bits from the Traffic Class field.
To ensure that the ECN bits appear in the same location for all To ensure that the ECN bits appear in the same location for all
encodings that include them, the Traffic Class field is rotated right encodings that include them, the Traffic Class field is rotated right
by 2 bits in the compressed IPv6 header. The encodings are shown by 2 bits in the compressed IPv6 header. The encodings are shown
below: below:
1 2 3 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|ECN| DSCP | rsv | Flow Label | |ECN| DSCP | rsv | Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: TF = 00: Traffic Class and Flow Label carried in-line. Figure 4: TF = 00: Traffic Class and Flow Label carried in-line
1 2 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|ECN|rsv| Flow Label | |ECN|rsv| Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: TF = 01: Flow Label carried in-line. Figure 5: TF = 01: Flow Label carried in-line
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|ECN| DSCP | |ECN| DSCP |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
Figure 6: TF = 10: Traffic Class carried in-line. Figure 6: TF = 10: Traffic Class carried in-line
3.2.2. Deriving IIDs from the Encapsulating Header 3.2.2. Deriving IIDs from the Encapsulating Header
LOWPAN_IPHC elides the IIDs of source or destination addresses when LOWPAN_IPHC elides the IIDs of source or destination addresses when
SAM = 3 or DAM = 3, respectively. In this mode, the IID is derived SAM = 3 or DAM = 3, respectively. In this mode, the IID is derived
from the encapsulating header. When the encapsulating header carries from the encapsulating header. When the encapsulating header carries
IPv6 addresses, bits for the source and destination addresses are IPv6 addresses, bits for the source and destination addresses are
copied from the source and destination addresses of the encapsulating copied from the source and destination addresses of the encapsulating
IPv6 header. IPv6 header.
The remainder of this section defines the mapping from IEEE 802.15.4 The remainder of this section defines the mapping from IEEE 802.15.4
[IEEE 802.15.4] link-layer addresses to IIDs for both short and [IEEE802.15.4] link-layer addresses to IIDs for both short and
extended IEEE 802.15.4 addresses. IID bits not covered by the extended IEEE 802.15.4 addresses. IID bits not covered by the
context information MAY be elided if they match the link-layer context information MAY be elided if they match the link-layer
address mapping and MUST NOT be elided if they do not. address mapping and MUST NOT be elided if they do not.
An extended IEEE 802.15.4 address takes the form of an IEEE EUI-64 An extended IEEE 802.15.4 address takes the form of an IEEE EUI-64
address. Generating an IID from an extended address is identical to address. Generating an IID from an extended address is identical to
that defined in Appendix A of [RFC4291]. The only change needed to that defined in Appendix A of [RFC4291]. The only change needed to
transform an IEEE EUI-64 identifier to an interface identifier is to transform an IEEE EUI-64 identifier to an interface identifier is to
invert the universal/local bit. invert the universal/local bit.
skipping to change at page 12, line 33 skipping to change at page 13, line 31
This mapping from a short IEEE 802.15.4 address to 64-bit IIDs is This mapping from a short IEEE 802.15.4 address to 64-bit IIDs is
also used to reconstruct any part of an IID not covered by context also used to reconstruct any part of an IID not covered by context
information. information.
3.2.3. Stateless Multicast Address Compression 3.2.3. Stateless Multicast Address Compression
LOWPAN_IPHC supports stateless compression of multicast addresses LOWPAN_IPHC supports stateless compression of multicast addresses
when M = 1 and DAC = 0. An IPv6 multicast address may be compressed when M = 1 and DAC = 0. An IPv6 multicast address may be compressed
down to 48, 32, or 8 bits using stateless compression. The format down to 48, 32, or 8 bits using stateless compression. The format
supports compression of the Solicited-Node Multicast Address (FF02:: supports compression of the Solicited-Node Multicast Address (ff02::
1:FFXX:XXXX) as well as any IPv6 multicast address where the upper 1:ffXX:XXXX) as well as any IPv6 multicast address where the upper
bits of the multicast group identifier are zero. The 8-bit bits of the multicast group identifier are zero. The 8-bit
compressed form only carries the least-significant bits of the compressed form only carries the least-significant bits of the
multicast group identifier. The 48 and 32-bit compressed forms carry multicast group identifier. The 48- and 32-bit compressed forms
the multicast scope and flags in-line, in addition to the least- carry the multicast scope and flags in-line, in addition to the
significant bits of the multicast group identifier. least-significant bits of the multicast group identifier.
1 2 3 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Scope | Group Identifier | | Flags | Scope | Group Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group Identifier | | Group Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: DAM = 01. 48-bit Compressed Multicast Address (FFfs::00gg: Figure 7: DAM = 01. 48-bit Compressed Multicast Address
gggg:gggg) (ffFS::00GG:GGGG:GGGG)
1 2 3 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Scope | Group Identifier | | Flags | Scope | Group Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: DAM = 10. 32-bit Compressed Multicast Address (FFfs::00gg: Figure 8: DAM = 10. 32-bit Compressed Multicast Address
gggg). (ffFS::00GG:GGGG)
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
| Group ID | | Group ID |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
Figure 9: DAM = 11. 8-bit Compressed Multicast Address (FF02::gg). Figure 9: DAM = 11. 8-bit Compressed Multicast Address (ff02::GG)
3.2.4. Stateful Multicast Address Compression 3.2.4. Stateful Multicast Address Compression
LOWPAN_IPHC supports stateful compression of multicast addresses when LOWPAN_IPHC supports stateful compression of multicast addresses when
M = 1 and DAC = 1. This document currently defines DAM = 00: M = 1 and DAC = 1. This document currently defines DAM = 00:
context-based compression of Unicast-Prefix-based IPv6 Multicast context-based compression of Unicast-Prefix-based IPv6 Multicast
Addresses [RFC3306][RFC3956]. In particular, the Prefix Length and Addresses [RFC3306][RFC3956]. In particular, the Prefix Length and
Network Prefix can be taken from a context. As a result, LOWPAN_IPHC Network Prefix can be taken from a context. As a result, LOWPAN_IPHC
can compress a Unicast-Prefix-based IPv6 Multicast Address down to 6 can compress a Unicast-Prefix-based IPv6 Multicast Address down to 6
octets by only carrying the 4-bit Flags, 4-bit Scope, 8-bit RIID, and octets by only carrying the 4-bit Flags, 4-bit Scope, 8-bit
32-bit Group Identifier in-line. Rendezvous Point Interface ID (RIID), and 32-bit Group Identifier in-
line.
1 2 3 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Scope | Rsvd / RIID | Group Identifier | | Flags | Scope | Rsvd / RIID | Group Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group Identifier | | Group Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: DAM = 00. Unicast-Prefix-based IPv6 Multicast Address Figure 10: DAM = 00. Unicast-Prefix-based IPv6 Multicast
Compression Address Compression
Note that the Reserved field MUST carry the reserved bits from the Note that the Reserved field MUST carry the reserved bits from the
multicast address format as described in [RFC3306]. When a multicast address format as described in [RFC3306]. When a
Rendezvous Point is encoded in the multicast address as described in Rendezvous Point is encoded in the multicast address as described in
[RFC3956], the Reserved field carries the RIID bits in-line. [RFC3956], the Reserved field carries the RIID bits in-line.
4. IPv6 Next Header Compression 4. IPv6 Next Header Compression
LOWPAN_IPHC elides the IPv6 Next Header field when the NH bit is set LOWPAN_IPHC elides the IPv6 Next Header field when the NH bit is set
to 1. This also indicates the use of 6LoWPAN next header to 1. This also indicates the use of 6LoWPAN next header
skipping to change at page 15, line 14 skipping to change at page 15, line 43
+----------------+--------------------------- +----------------+---------------------------
| var-len NHC ID | compressed next header... | var-len NHC ID | compressed next header...
+----------------+--------------------------- +----------------+---------------------------
Figure 12: LOWPAN_NHC Encoding Figure 12: LOWPAN_NHC Encoding
4.2. IPv6 Extension Header Compression 4.2. IPv6 Extension Header Compression
A necessary property of encoding headers using LOWPAN_NHC is that the A necessary property of encoding headers using LOWPAN_NHC is that the
immediately preceding header must either be encoded using LOWPAN_IPHC immediately preceding header must be encoded using either LOWPAN_IPHC
or LOWPAN_NHC. In other words, all headers encoded using the 6LoWPAN or LOWPAN_NHC. In other words, all headers encoded using the 6LoWPAN
encoding format defined in this document must be contiguous. As a encoding format defined in this document must be contiguous. As a
result, this document defines a set of LOWPAN_NHC encodings for result, this document defines a set of LOWPAN_NHC encodings for
selected IPv6 Extension Headers such that the UDP Header Compression selected IPv6 Extension Headers such that the UDP Header Compression
defined in Section 4.3 may be used in the presence of those extension defined in Section 4.3 may be used in the presence of those extension
headers. headers.
The LOWPAN_NHC encodings for IPv6 Extension Headers are composed of a The LOWPAN_NHC encodings for IPv6 Extension Headers are composed of a
single LOWPAN_NHC octet followed by the IPv6 Extension Header. The single LOWPAN_NHC octet followed by the IPv6 Extension Header. The
format of the LOWPAN_NHC octet is shown in Figure 13. The first 7 format of the LOWPAN_NHC octet is shown in Figure 13. The first 7
skipping to change at page 15, line 37 skipping to change at page 16, line 20
or not the following header utilizes LOWPAN_NHC encoding. or not the following header utilizes LOWPAN_NHC encoding.
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
| 1 | 1 | 1 | 0 | EID |NH | | 1 | 1 | 1 | 0 | EID |NH |
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
Figure 13: IPv6 Extension Header Encoding Figure 13: IPv6 Extension Header Encoding
EID: IPv6 Extension Header ID: EID: IPv6 Extension Header ID:
0: IPv6 Hop-by-Hop Options Header[RFC2460]
1: IPv6 Routing Header[RFC2460] 0: IPv6 Hop-by-Hop Options Header [RFC2460]
2: IPv6 Fragment Header[RFC2460]
3: IPv6 Destination Options Header[RFC2460] 1: IPv6 Routing Header [RFC2460]
4: IPv6 Mobility Header [RFC3775]
2: IPv6 Fragment Header [RFC2460]
3: IPv6 Destination Options Header [RFC2460]
4: IPv6 Mobility Header [RFC6275]
5: Reserved 5: Reserved
6: Reserved 6: Reserved
7: IPv6 Header 7: IPv6 Header
NH: Next Header: NH: Next Header:
0: Full 8 bits for Next Header are carried in-line. 0: Full 8 bits for Next Header are carried in-line.
1: The Next Header field is elided and the next header is encoded 1: The Next Header field is elided and the next header is encoded
using LOWPAN_NHC, which is discussed in Section 4.1. using LOWPAN_NHC, which is discussed in Section 4.1.
For the most part, the IPv6 Extension Header is carried unmodified in For the most part, the IPv6 Extension Header is carried unmodified in
the bytes immediately following the LOWPAN_NHC octet, with two the bytes immediately following the LOWPAN_NHC octet, with two
important exceptions: Length Field and Next Header Field. important exceptions: Length field and Next Header field.
The Next Header Field contained in IPv6 Extension Headers is elided The Next Header field contained in IPv6 Extension Headers is elided
when the NH bit is set in the LOWPAN_NHC encoding octet. Note that when the NH bit is set in the LOWPAN_NHC encoding octet. Note that
doing so allows LOWPAN_NHC to utilize no more overhead than the non- doing so allows LOWPAN_NHC to utilize no more overhead than the non-
encoded IPv6 Extension Header. encoded IPv6 Extension Header.
The Length Field contained in a compressed IPv6 Extension Header The Length field contained in a compressed IPv6 Extension Header
indicates the number of octets that pertain to the (compressed) indicates the number of octets that pertain to the (compressed)
extension header following the Length Field. Note that this changes extension header following the Length field. Note that this changes
the Length Field definition in [RFC2460] from indicating the header the Length field definition in [RFC2460] from indicating the header
size in 8-octet units, not including the first 8 octets. Changing size in 8-octet units, not including the first 8 octets. Changing
the Length Field to be in units of octets removes wasteful internal the Length field to be in units of octets removes wasteful internal
fragmentation. fragmentation.
IPv6 Hop-by-Hop and Destination Options Headers may use a trailing IPv6 Hop-by-Hop and Destination Options Headers may use a trailing
Pad1 or PadN to achieve 8-octet alignment. When there is a single Pad1 or PadN to achieve 8-octet alignment. When there is a single
trailing Pad1 or PadN option of 7 octets or less and the containing trailing Pad1 or PadN option of 7 octets or less and the containing
header is a multiple of 8 octets, the trailing Pad1 or PadN option header is a multiple of 8 octets, the trailing Pad1 or PadN option
MAY be elided by the compressor. A decompressor MUST ensure that the MAY be elided by the compressor. A decompressor MUST ensure that the
containing header is padded out to a multiple of 8 octets in length, containing header is padded out to a multiple of 8 octets in length,
using a Pad1 or PadN option if necessary. Note that Pad1 and PadN using a Pad1 or PadN option if necessary. Note that Pad1 and PadN
options that appear in locations other than the end MUST be carried options that appear in locations other than the end MUST be carried
in-line as they are used to align subsequent options. in-line as they are used to align subsequent options.
Note that specifying units in octets means that LOWPAN_NHC MUST NOT Note that specifying units in octets means that LOWPAN_NHC MUST NOT
be used to encode IPv6 Extension Headers that have more than 255 be used to encode IPv6 Extension Headers that have more than 255
octets following the Length Field after compression. octets following the Length field after compression.
When the identified next header is an IPv6 Header (EID=7), the NH bit When the identified next header is an IPv6 Header (EID=7), the NH bit
of the LOWPAN_NHC encoding is unused and MUST be set to zero. The of the LOWPAN_NHC encoding is unused and MUST be set to zero. The
following bytes MUST be encoded using LOWPAN_IPHC as defined in following bytes MUST be encoded using LOWPAN_IPHC as defined in
Section 3. Section 3.
4.3. UDP Header Compression 4.3. UDP Header Compression
This document defines a compression format for UDP headers using This document defines a compression format for UDP headers using
LOWPAN_NHC. The UDP compression format is shown in Figure 14. Bits LOWPAN_NHC. The UDP compression format is shown in Figure 14. Bits
0 through 4 represent the NHC ID and '11110' indicates the specific 0 through 4 represent the NHC ID and '11110' indicates the specific
UDP header compression encoding defined in this section. UDP header compression encoding defined in this section.
4.3.1. Compressing UDP ports 4.3.1. Compressing UDP Ports
This specification allows a particular range of ports number (0xF0B0 This specification allows a particular range of ports number (0xf0b0
to 0xF0BF) to be compressed down to 4 bits. This is a stateless to 0xf0bf) to be compressed down to 4 bits. This is a stateless
compression that is inherited from [RFC4944], as opposed to a new compression that is inherited from [RFC4944], as opposed to a new
stateful compression. stateful compression.
The range of ports compressible down to 4 bits is not in a reserved The range of ports compressible down to 4 bits is not in a reserved
range. A network stack implementation that is designed to range. A network stack implementation that is designed to
communicate over a 6LoWPAN should avoid using those ports as dynamic communicate over a 6LoWPAN should avoid using those ports as dynamic
ports whenever possible. ports whenever possible.
Considering that this represents only 16 contiguous ports, it can be Considering that this represents only 16 contiguous ports, it can be
expected that many incompatible applications will use the same value expected that many incompatible applications will use the same value
of port numbers for their own end-to-end needs. Thus a port number of port numbers for their own end-to-end needs. Thus, a port number
in the (0xF0B0 to 0xF0BF) range provides very little information in the (0xf0b0 to 0xf0bf) range provides very little information
about the application at the remote end. about the application at the remote end.
The overloading of the 0xF0Bx ports increases the risk of getting the The overloading of the 0xf0bX ports increases the risk of getting the
wrong type of payload and misinterpreting the content compared to wrong type of payload and misinterpreting the content compared to
ports that are reserved at IANA. As a result, it is recommended that ports that are reserved at IANA. As a result, it is recommended that
the use of those ports be associated with a mechanism such as a the use of those ports be associated with a mechanism such as a
Transport Layer Security (TLS) [RFC5246] Message Integrity Check Transport Layer Security (TLS) [RFC5246] Message Integrity Check
(MIC) that makes sure that the content is what is expected and is (MIC) that makes sure that the content is what is expected and is
checked. checked.
4.3.2. Compressing UDP checksum 4.3.2. Compressing UDP Checksum
The UDP checksum operation is mandatory with IPv6 [RFC2460] for all The UDP checksum operation is mandatory with IPv6 [RFC2460] for all
packets. For that reason [RFC4944] disallows the compression of the packets. For that reason, [RFC4944] disallows the compression of the
UDP checksum. UDP checksum.
With this specification, a compressor in the source transport With this specification, a compressor in the source transport
endpoint MAY elide the UDP Checksum if it is authorized by the Upper endpoint MAY elide the UDP Checksum if it is authorized by the upper
Layer. The compressor MUST NOT set the C bit unless it has received layer. The compressor MUST NOT set the C bit unless it has received
such authorization. Requiring Upper Layer authorization ensures that such authorization. Requiring upper-layer authorization ensures that
the intended transport peer will have sufficient means to deal with the intended transport peer will have sufficient means to deal with
any data corruption that occurs before reaching the destination. The any data corruption that occurs before reaching the destination. The
Upper Layer MAY only provide the authorization in the following upper layer MUST NOT provide the authorization unless one of the
cases: following cases is satisfied:
Tunneling: In this case, 6LoWPAN is deployed as a wireless pseudo- Tunneling: In this case, 6LoWPAN is deployed as a wireless pseudo-
fieldbus by tunneling existing field protocols over UDP. If the fieldbus by tunneling existing field protocols over UDP. If the
tunneled Protocol Data Unit (PDU) possesses its own addressing, tunneled Protocol Data Unit (PDU) possesses its own addressing,
security and integrity check (e.g. IPsec Encapsulating Security security and integrity check (e.g., IPsec Encapsulating Security
Payload tunnel mode [RFC4303] or IP over UDP encapsulation), the Payload tunnel mode [RFC4303] or IP over UDP encapsulation), the
tunneling mechanism MAY authorize to elide the UDP checksum in tunneling mechanism MAY authorize eliding the UDP checksum in
order to save on the encapsulation overhead. order to save on the encapsulation overhead.
Message Integrity Check: In this case, either IPsec Authentication Message Integrity Check: In this case, either IPsec Authentication
Header [RFC4302] or some other form of integrity check in the UDP Header [RFC4302] or some other form of integrity check in the UDP
payload that covers at least the same information as the UDP payload that covers at least the same information as the UDP
checksum (pseudo-header, data) and has at least the same strength. checksum (pseudo-header, data) and has at least the same strength.
The Upper Layer MUST NOT provide the authorization when neither of
the above two cases applies.
To help ensure that the UDP Checksum will be properly restored when To help ensure that the UDP Checksum will be properly restored when
expanding a 6LoWPAN packet, an additional integrity check (e.g. L2 expanding a 6LoWPAN packet, an additional integrity check (e.g., a
Message Integrity Check) MUST be used whenever transmitting link Layer 2 (L2) Message Integrity Check) MUST be used whenever
frames that carry a compressed UDP datagram that elides the checksum. transmitting link frames that carry a compressed UDP datagram that
Without this additional integrity check, a UDP packet may be elides the checksum. Without this additional integrity check, a UDP
delivered to an unintended destination since corruption in data packet may be delivered to an unintended destination since corruption
covered by the pseudo-header can go undetected. in data covered by the pseudo-header can go undetected.
A compressor MUST verify the UDP Checksum before it is elided and A compressor MUST verify the UDP Checksum before it is elided and
SHOULD ensure that the additional integrity check is in place before MUST ensure that the additional integrity check is in place before
verifying and eliding the checksum. If verification of the UDP verifying and eliding the checksum. If verification of the UDP
Checksum fails, the compressor MUST drop the packet. Checksum fails, the compressor MUST drop the packet.
A decompressor that expands a 6LoWPAN packet with the C bit set MUST A decompressor that expands a 6LoWPAN packet with the C bit set MUST
compute the UDP Checksum on behalf of the source node and place that compute the UDP Checksum on behalf of the source node and place that
value in the restored UDP header as specified in the incumbent value in the restored UDP header as specified in the incumbent
standards [RFC0768], [RFC2460]. The decompressor MUST unambiguously standards [RFC0768], [RFC2460]. The decompressor MUST unambiguously
determine that an additional integrity check was put in place by the determine that an additional integrity check was put in place by the
compressor and verify the integrity check, and SHOULD do so after compressor and verify the integrity check and SHOULD do so after
restoring the UDP Checksum. If the decompressor cannot unambiguously restoring the UDP Checksum. If the decompressor cannot unambiguously
determine the presence of an integrity check or verification fails, determine the presence of an integrity check or verification fails,
the decompressor MUST drop the packet. the decompressor MUST drop the packet.
The recommended ordering of computing and verify the UDP Checksum and The recommended ordering of computing and verifying the UDP Checksum
additional integrity check ensures that data is never stored and additional integrity check ensures that data is never stored
unprotected in memory. In practice, functionality separation between unprotected in memory. In practice, functionality separation between
layers may preclude the recommended ordering. However, implementors layers may preclude the recommended ordering. However, implementors
should take special note and understand the risks when dealing with should take special note and understand the risks when dealing with
unprotected data covered by the pseudo-header. unprotected data covered by the pseudo-header.
To allow intermediate nodes to compress the UDP Checksum, a To allow intermediate nodes to compress the UDP Checksum, a
forwarding node MAY infer Upper Layer authorization for an incoming forwarding node MAY infer upper-layer authorization for an incoming
packet if it has the C bit set and it can unambiguously determine packet if it has the C bit set and it can unambiguously determine
that an integrity check covering the same data as the UDP Checksum that an integrity check covering the same data as the UDP Checksum
was in place while the UDP Checksum was elided. A forwarding node was in place while the UDP Checksum was elided. A forwarding node
MUST NOT infer authorization if it cannot unambiguously determine the MUST NOT infer authorization if it cannot unambiguously determine the
presence of and verify an integrity check while the UDP Checksum was presence of and verify an integrity check while the UDP Checksum was
elided. elided.
4.3.3. UDP LOWPAN_NHC Format 4.3.3. UDP LOWPAN_NHC Format
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
skipping to change at page 19, line 15 skipping to change at page 20, line 15
4.3.3. UDP LOWPAN_NHC Format 4.3.3. UDP LOWPAN_NHC Format
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
| 1 | 1 | 1 | 1 | 0 | C | P | | 1 | 1 | 1 | 1 | 0 | C | P |
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
Figure 14: UDP Header Encoding Figure 14: UDP Header Encoding
C: Checksum: C: Checksum:
0: All 16 bits of Checksum are carried in-line. 0: All 16 bits of Checksum are carried in-line.
1: All 16 bits of Checksum are elided. The Checksum is recovered 1: All 16 bits of Checksum are elided. The Checksum is recovered
by recomputing it on the 6LoWPAN termination point. by recomputing it on the 6LoWPAN termination point.
P: Ports: P: Ports:
00: All 16 bits for both Source Port and Destination Port are 00: All 16 bits for both Source Port and Destination Port are
carried in-line. carried in-line.
01: All 16 bits for Source Port are carried in-line. First 8 01: All 16 bits for Source Port are carried in-line. First 8
bits of Destination Port is 0xF0 and elided. The remaining 8 bits of Destination Port is 0xf0 and elided. The remaining 8
bits of Destination Port are carried in-line. bits of Destination Port are carried in-line.
10: First 8 bits of Source Port are 0xF0 and elided. The
10: First 8 bits of Source Port are 0xf0 and elided. The
remaining 8 bits of Source Port are carried in-line. All 16 remaining 8 bits of Source Port are carried in-line. All 16
bits for Destination Port are carried in-line. bits for Destination Port are carried in-line.
11: First 12 bits of both Source Port and Destination Port are 11: First 12 bits of both Source Port and Destination Port are
0xF0B and elided. The remaining 4 bits for each are carried 0xf0b and elided. The remaining 4 bits for each are carried
in-line. in-line.
Fields carried in-line (in part or in whole) appear in the same order Fields carried in-line (in part or in whole) appear in the same order
as they do in the UDP header format [RFC0768]. The UDP Length field as they do in the UDP header format [RFC0768]. The UDP Length field
MUST always be elided and is inferred from lower layers using the MUST always be elided and is inferred from lower layers using the
6LoWPAN Fragmentation header or the IEEE 802.15.4 header. 6LoWPAN Fragmentation header or the IEEE 802.15.4 header.
5. IANA Considerations 5. IANA Considerations
This document defines a new IPv6 header compression format for This document defines a new IPv6 header compression format for
6LoWPAN. The document allocates the following 32 Dispatch type field 6LoWPAN. The document allocates the following 32 Dispatch type field
values for LOWPAN_IPHC: values for LOWPAN_IPHC:
01 100000 01 100000
through through
01 111111 01 111111
This assignment preempts the assignment of 01 111111 for ESC This assignment preempts the assignment of 01 111111 for ESC
[RFC4944], which is possible as no extension bytes have been [RFC4944]; this preemption is possible because extension bytes that
allocated yet that would enable the use of ESC. Instead, the value: would enable the use of ESC have not been allocated yet. Instead,
the value:
01 000000 01 000000
is reserved as a replacement value for ESC, to be finally assigned is reserved as a replacement value for ESC, to be finally assigned
with the first assignment of extension bytes. with the first assignment of extension bytes.
This document also creates a new IANA registry for the LOWPAN_NHC This document also creates a new IANA registry for the LOWPAN_NHC
header type, with the following initial content: header type, with the following initial content:
00000000 to 11011111: (unassigned) 00000000 to 11011111: (unassigned)
1110000N: IPv6 Hop-by-Hop Options Header [RFCthis] 1110000N: IPv6 Hop-by-Hop Options Header [RFC6282]
1110001N: IPv6 Routing Header [RFCthis] 1110001N: IPv6 Routing Header [RFC6282]
1110010N: IPv6 Fragment Header [RFCthis] 1110010N: IPv6 Fragment Header [RFC6282]
1110011N: IPv6 Destination Options Header [RFCthis] 1110011N: IPv6 Destination Options Header [RFC6282]
1110100N: IPv6 Mobility Header [RFCthis] 1110100N: IPv6 Mobility Header [RFC6282]
1110101N: (Reserved for future extension headers) 1110111N: IPv6 Header [RFC6282]
1110110N: (Reserved for future extension headers) 11110CPP: UDP Header [RFC6282]
1110111N: IPv6 Header [RFCthis]
11110CPP: UDP Header [RFCthis]
11111000 to 11111110: (unassigned) 11111000 to 11111110: (unassigned)
11111111: (unassigned, reserved for extensions)
Capital letters in bit positions represent class-specific bit Capital letters in bit positions represent class-specific bit
assignments. N indicates whether or not additional LOWPAN_NHC assignments. N indicates whether or not additional LOWPAN_NHC
encodings follow, as defined in Section 4.2. CPP represents encodings follow, as defined in Section 4.2. CPP represents
variables specific to UDP header compression defined in Section 4.3. variables specific to UDP header compression defined in Section 4.3.
The policy for this registry [RFC5226] is IETF Review. In this The policy for this registry [RFC5226] is IETF Review. In this
process, new values SHOULD be assigned in a way that preserves the process, new values SHOULD be assigned in a way that preserves the
NHC ID abstraction of Section 4 (i.e., k one-bits followed by one NHC ID abstraction of Section 4 (i.e., k one-bits followed by one
zero-bit identify the general class of NHC, followed by class- zero-bit identify the general class of NHC, followed by class-
skipping to change at page 20, line 50 skipping to change at page 21, line 48
6. Security Considerations 6. Security Considerations
The definition of LOWPAN_IPHC permits the compression of header The definition of LOWPAN_IPHC permits the compression of header
information on communication that could take place in its absence, information on communication that could take place in its absence,
albeit in a less efficient form. It recognizes that a IEEE 802.15.4 albeit in a less efficient form. It recognizes that a IEEE 802.15.4
PAN may have associated with it a number of prefixes through shared PAN may have associated with it a number of prefixes through shared
context. How the shared context is assigned and managed is beyond context. How the shared context is assigned and managed is beyond
the scope of this document. the scope of this document.
The overloading of the 0xF0Bx ports increases the risk of getting the The overloading of the 0xf0bX ports increases the risk of getting the
wrong type of payload and misinterpreting the content compared to wrong type of payload and misinterpreting the content compared to
ports that reserved at IANA. It is thus recommended that the use of ports that reserved at IANA. It is thus recommended that the use of
those ports be associated with a mechanism such as a Transport Layer those ports be associated with a mechanism such as a Transport Layer
Security (TLS) [RFC5246] Message Integrity Check (MIC) that validates Security (TLS) [RFC5246] Message Integrity Check (MIC) that validates
that the content is expected and checked for integrity. that the content is expected and checked for integrity.
7. Acknowledgements 7. Acknowledgements
Thanks to Julien Abeille, Robert Assimiti, Dominique Barthel, Carsten Thanks to Julien Abeille, Robert Assimiti, Dominique Barthel, Carsten
Bormann, Robert Cragie, Stephen Dawson-Haggerty, Mathilde Durvy, Erik Bormann, Robert Cragie, Stephen Dawson-Haggerty, Mathilde Durvy, Erik
Nordmark, Christos Polyzois, Joseph Reddy, Shoichi Sakane, Zach Nordmark, Christos Polyzois, Joseph Reddy, Shoichi Sakane, Zach
Shelby, Dario Tedeschi, Tony Viscardi, and Jay Werb for useful design Shelby, Dario Tedeschi, Tony Viscardi, and Jay Werb for useful design
consideration and implementation feedback. Special thanks to David consideration and implementation feedback. Special thanks to David
Black, Lars Eggert and Carsten Bormann for their contribution in Black, Lars Eggert, and Carsten Bormann for their contribution in
closing the security issues around UDP compression. closing the security issues around UDP compression.
8. Changes 8. References
(This section to be removed by the RFC editor.)
Draft 15:
- Edits in response to IESG comments.
Draft 14:
- Edits in response to IESG comments.
Draft 13:
- Specify that address bits not covered by the context or IID are
zero.
Draft 12:
- Specify that 16-bit to IID mapping is used to derive IID bits
when SAC/DAC=1 and the context does not cover those bits.
Draft 11:
- Removed incorrect and unnecessary text in specifying how to
derive the IID bits not covered by the context.
- Adjust formatting to reduce orphans and widows.
Draft 10:
- Specify that the IID has the form 0000:00ff:fe00:XXXX when SAC/
DAC=0 and SAM/DAM=10.
Draft 09:
- Indicate that a mechanism to learn decompressor's capabilities
to decode additional (future) NHCs is out of scope.
- Clarify how to derive IID bits not covered by the context when
only 16 bits are carried inline.
- Clarify the value of the Length field for compressed extension
headers.
- Added an IANA registry for LOWPAN_NHC types.
Draft 08:
- Clarified that the lower bits of an IPv6 address may be derived
from an IPv6 header, not just an 802.15.4 header. Change text
from "derived from link-layer header" to "derived from
encapsulating header".
Draft 07:
- Added section on mapping link-layer addresses to IIDs.
- Added text on restricting compressed headers to first fragment
when using fragment headers defined in Section 5.3 of [RFC4944].
- Minor editorial edits.
Draft 06:
- Reworked introduction.
- Added section on updates to [RFC4944].
- Fixed description of number of bits used for IPHC encoding.
- Specify M=0 only for non-multicast addresses and M=1 only for
multicast addresses.
- Move 128-bit multicast encoding to DAC=0.
- Redefined ESC dispatch value to 01 000000.
- Many detailed edits.
Draft 05:
- Added LOWPAN_NHC encodings for IPv6 Extension Headers.
- Specify use of context 0 when CID is 0.
- Indicate that first 64-bits is link-local prefix padded with
zeros when link-local prefix is elided.
- Made prefix-based multicast encoding format more explicit for
clarity.
- Changed wording around stateful compression to allow for using
the in-line bits as an additional index to identify the compressed
address.
- Removed support for compressing unspecified address.
- Full 128-bit addr in-line only in stateless encoding.
Draft 04:
- Fixed typos leftover from the changes in 03.
- Gave more details on UDP checksum compression.
- Clarify that the context information is out of scope.
- Added security concern on 0xF0Bx port overloading.
Draft 03:
- Decoupled meaning of SAM bits from the destination address.
- Have separate bit to indicate multicast address compression.
- More extensive support for multicast address compression,
including Unicast-Prefix-based Multicast Addresses.
Draft 02:
- Updated wording with compression mode to clarify that a
compression mode does not enforce what kind of destination address
is being used. Specifically changed Destination Dependent Field
to Compression Mode.
- Specify that the configuration and management of contexts is out
of scope of this document.
Draft 01:
- HC back to 1 byte by default by stealing a few bits from the
dispatch field.
- Added better support for multicast address compression.
- Fixed alignment for UDP port compression.
- Better support for Traffic Class and Flow Label compression.
- Pascal joined as an author.
9. References
9.1. Normative References 8.1. Normative References
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980. August 1980.
[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, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol,
(IPv6) Specification", RFC 2460, December 1998. Version 6 (IPv6) Specification", RFC 2460,
December 1998.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS "Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474, Field) in the IPv4 and IPv6 Headers", RFC 2474,
December 1998. December 1998.
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The
of Explicit Congestion Notification (ECN) to IP", Addition of Explicit Congestion Notification (ECN) to
RFC 3168, September 2001. IP", RFC 3168, September 2001.
[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
in IPv6", RFC 3775, June 2004. Architecture", RFC 4291, February 2006.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing [RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D.
Architecture", RFC 4291, February 2006. Culler, "Transmission of IPv6 Packets over IEEE
802.15.4 Networks", RFC 4944, September 2007.
[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler, [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing
"Transmission of IPv6 Packets over IEEE 802.15.4 an IANA Considerations Section in RFCs", BCP 26,
Networks", RFC 4944, September 2007. RFC 5226, May 2008.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko,
IANA Considerations Section in RFCs", BCP 26, RFC 5226, "Mobility Support in IPv6", RFC 6275, July 2011.
May 2008.
9.2. Informative References 8.2. Informative References
[IEEE 802.15.4] [IEEE802.15.4] IEEE Computer Society, "IEEE Std. 802.15.4-2006",
IEEE Computer Society, "IEEE Std. 802.15.4-2006", October 2006.
October 2006.
[RFC3306] Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6 [RFC3306] Haberman, B. and D. Thaler, "Unicast-Prefix-based
Multicast Addresses", RFC 3306, August 2002. IPv6 Multicast Addresses", RFC 3306, August 2002.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins,
and M. Carney, "Dynamic Host Configuration Protocol for C., and M. Carney, "Dynamic Host Configuration
IPv6 (DHCPv6)", RFC 3315, July 2003. Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003.
[RFC3956] Savola, P. and B. Haberman, "Embedding the Rendezvous [RFC3956] Savola, P. and B. Haberman, "Embedding the Rendezvous
Point (RP) Address in an IPv6 Multicast Address", Point (RP) Address in an IPv6 Multicast Address",
RFC 3956, November 2004. RFC 3956, November 2004.
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302, [RFC4302] Kent, S., "IP Authentication Header", RFC 4302,
December 2005. December 2005.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, December 2005. RFC 4303, December 2005.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H.
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, Soliman, "Neighbor Discovery for IP version 6
September 2007. (IPv6)", RFC 4861, September 2007.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer
(TLS) Protocol Version 1.2", RFC 5246, August 2008. Security (TLS) Protocol Version 1.2", RFC 5246,
August 2008.
Authors' Addresses Authors' Addresses
Jonathan W. Hui (editor) Jonathan W. Hui (editor)
Arch Rock Corporation Arch Rock Corporation
501 2nd St. Ste. 410 501 2nd St. Ste. 410
San Francisco, California 94107 San Francisco, California 94107
USA USA
Phone: +415 692 0828 Phone: +415 692 0828
Email: jhui@archrock.com EMail: jhui@archrock.com
Pascal Thubert Pascal Thubert
Cisco Systems Cisco Systems
Village d'Entreprises Green Side Village d'Entreprises Green Side
400, Avenue de Roumanille 400, Avenue de Roumanille
Batiment T3 Batiment T3
Biot - Sophia Antipolis 06410 Biot - Sophia Antipolis 06410
FRANCE FRANCE
Phone: +33 4 97 23 26 34 Phone: +33 4 97 23 26 34
Email: pthubert@cisco.com EMail: pthubert@cisco.com
 End of changes. 147 change blocks. 
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