draft-ietf-lpwan-coap-static-context-hc-06.txt   draft-ietf-lpwan-coap-static-context-hc-07.txt 
lpwan Working Group A. Minaburo lpwan Working Group A. Minaburo
Internet-Draft Acklio Internet-Draft Acklio
Intended status: Informational L. Toutain Intended status: Standards Track L. Toutain
Expires: August 9, 2019 Institut MINES TELECOM; IMT Atlantique Expires: November 25, 2019 Institut MINES TELECOM; IMT Atlantique
R. Andreasen R. Andreasen
Universidad de Buenos Aires Universidad de Buenos Aires
February 05, 2019 May 24, 2019
LPWAN Static Context Header Compression (SCHC) for CoAP LPWAN Static Context Header Compression (SCHC) for CoAP
draft-ietf-lpwan-coap-static-context-hc-06 draft-ietf-lpwan-coap-static-context-hc-07
Abstract Abstract
This draft defines the way SCHC header compression can be applied to This draft defines the way SCHC header compression can be applied to
CoAP headers. The CoAP header structure differs from IPv6 and UDP CoAP headers. The CoAP header structure differs from IPv6 and UDP
protocols since CoAP protocols since CoAP
use a flexible header with a variable number of options themselves of uses a flexible header with a variable number of options themselves
a variable length. The CoAP protocol is asymmetric in its format of variable length. The CoAP protocol is asymmetric in its message
messages, the format of the header packet in the request messages is format, the format of the header packet in the request messages is
different than in the response messages. Most of the compression different from that in the response messages. Most of the
mechanisms have been introduced in compression mechanisms have been introduced in
[I-D.ietf-lpwan-ipv6-static-context-hc], this document explains how [I-D.ietf-lpwan-ipv6-static-context-hc], this document explains how
to use the SCHC compression for CoAP. to use the SCHC compression for CoAP.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 9, 2019. This Internet-Draft will expire on November 25, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 29 skipping to change at page 2, line 29
3. CoAP Compression with SCHC . . . . . . . . . . . . . . . . . 4 3. CoAP Compression with SCHC . . . . . . . . . . . . . . . . . 4
4. Compression of CoAP header fields . . . . . . . . . . . . . . 6 4. Compression of CoAP header fields . . . . . . . . . . . . . . 6
4.1. CoAP version field . . . . . . . . . . . . . . . . . . . 6 4.1. CoAP version field . . . . . . . . . . . . . . . . . . . 6
4.2. CoAP type field . . . . . . . . . . . . . . . . . . . . . 6 4.2. CoAP type field . . . . . . . . . . . . . . . . . . . . . 6
4.3. CoAP code field . . . . . . . . . . . . . . . . . . . . . 6 4.3. CoAP code field . . . . . . . . . . . . . . . . . . . . . 6
4.4. CoAP Message ID field . . . . . . . . . . . . . . . . . . 6 4.4. CoAP Message ID field . . . . . . . . . . . . . . . . . . 6
4.5. CoAP Token fields . . . . . . . . . . . . . . . . . . . . 7 4.5. CoAP Token fields . . . . . . . . . . . . . . . . . . . . 7
5. CoAP options . . . . . . . . . . . . . . . . . . . . . . . . 7 5. CoAP options . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1. CoAP Content and Accept options. . . . . . . . . . . . . 7 5.1. CoAP Content and Accept options. . . . . . . . . . . . . 7
5.2. CoAP option Max-Age field, CoAP option Uri-Host and Uri- 5.2. CoAP option Max-Age field, CoAP option Uri-Host and Uri-
Port fields . . . . . . . . . . . . . . . . . . . . . . . 7 Port fields . . . . . . . . . . . . . . . . . . . . . . . 8
5.3. CoAP option Uri-Path and Uri-Query fields . . . . . . . . 8 5.3. CoAP option Uri-Path and Uri-Query fields . . . . . . . . 8
5.3.1. Variable length Uri-Path and Uri-Query . . . . . . . 8 5.3.1. Variable length Uri-Path and Uri-Query . . . . . . . 8
5.3.2. Variable number of path or query elements . . . . . . 9 5.3.2. Variable number of path or query elements . . . . . . 9
5.4. CoAP option Size1, Size2, Proxy-URI and Proxy-Scheme 5.4. CoAP option Size1, Size2, Proxy-URI and Proxy-Scheme
fields . . . . . . . . . . . . . . . . . . . . . . . . . 9 fields . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.5. CoAP option ETag, If-Match, If-None-Match, Location-Path 5.5. CoAP option ETag, If-Match, If-None-Match, Location-Path
and Location-Query fields . . . . . . . . . . . . . . . . 9 and Location-Query fields . . . . . . . . . . . . . . . . 9
6. Other RFCs . . . . . . . . . . . . . . . . . . . . . . . . . 9 6. Other RFCs . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.1. Block . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6.1. Block . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.2. Observe . . . . . . . . . . . . . . . . . . . . . . . . . 10 6.2. Observe . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.3. No-Response . . . . . . . . . . . . . . . . . . . . . . . 10 6.3. No-Response . . . . . . . . . . . . . . . . . . . . . . . 10
6.4. Time Scale . . . . . . . . . . . . . . . . . . . . . . . 10 6.4. Time Scale . . . . . . . . . . . . . . . . . . . . . . . 10
6.5. OSCORE . . . . . . . . . . . . . . . . . . . . . . . . . 10 6.5. OSCORE . . . . . . . . . . . . . . . . . . . . . . . . . 11
7. Examples of CoAP header compression . . . . . . . . . . . . . 12 7. Examples of CoAP header compression . . . . . . . . . . . . . 12
7.1. Mandatory header with CON message . . . . . . . . . . . . 12 7.1. Mandatory header with CON message . . . . . . . . . . . . 12
7.2. OSCORE Compression . . . . . . . . . . . . . . . . . . . 13 7.2. OSCORE Compression . . . . . . . . . . . . . . . . . . . 13
7.3. Example OSCORE Compression . . . . . . . . . . . . . . . 17 7.3. Example OSCORE Compression . . . . . . . . . . . . . . . 17
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
9. Security considerations . . . . . . . . . . . . . . . . . . . 27 9. Security considerations . . . . . . . . . . . . . . . . . . . 28
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 27 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 28
11. Normative References . . . . . . . . . . . . . . . . . . . . 27 11. Normative References . . . . . . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29
1. Introduction 1. Introduction
CoAP [rfc7252] is an implementation of the REST architecture for CoAP [rfc7252] is an implementation of the REST architecture for
constrained devices. Nevertheless, if limited, the size of a CoAP constrained devices. Although CoAP was designed for constrained
header may be too large for LPWAN constraints and some compression devices, the size of a CoAP header may still be too large for LPWAN
may be needed to reduce the header size. constraints and some compression may be needed to reduce the header
size.
[I-D.ietf-lpwan-ipv6-static-context-hc] defines a header compression [I-D.ietf-lpwan-ipv6-static-context-hc] defines a header compression
mechanism for LPWAN network based on a static context. The context mechanism for LPWAN network based on a static context. The context
is said static since the field description composing the Rules and is said static since the field description composing the Rules are
the context are not learned during the packet exchanges but are not learned during the packet exchanges but are previously defined.
previously defined. The context(s) is(are) known by both ends before The context(s) is(are) known by both ends before transmission.
transmission.
A context is composed of a set of rules that are referenced by Rule A context is composed of a set of rules that are referenced by Rule
IDs (identifiers). A rule contains an ordered list of the fields IDs (identifiers). A rule contains an ordered list of the fields
descriptions containing a field ID (FID), its length (FL) and its descriptions containing a field ID (FID), its length (FL) and its
position (FP), a direction indicator (DI) (upstream, downstream and position (FP), a direction indicator (DI) (upstream, downstream and
bidirectional) and some associated Target Values (TV). Target Value bidirectional) and some associated Target Values (TV). Target Value
indicates the value that can be expected. TV can also be a list of indicates the value that can be expected. TV can also be a list of
values. A Matching Operator (MO) is associated to each header field values. A Matching Operator (MO) is associated to each header field
description. The rule is selected if all the MOs fit the TVs for all description. The rule is selected if all the MOs fit the TVs for all
fields. In that case, a Compression/Decompression Action (CDA) fields. In that case, a Compression/Decompression Action (CDA)
associated to each field defines the link between the compressed and associated to each field defines the link between the compressed and
decompressed value for each of the header fields. Compression decompressed value for each of the header fields. Compression
results mainly in 4 actions: send the field value, send nothing, send results mainly in 4 actions: send the field value, send nothing, send
less significant bits of a field, send an index. Values sent are less significant bits of a field, send an index. Values sent are
called Compression Residues and follows the rule ID. called Compression Residues and follows the rule ID.
2. SCHC Compression Process 2. SCHC Compression Process
The SCHC Compression rules can be applied to CoAP flows. SCHC The SCHC Compression rules can be applied to CoAP flows. SCHC
Compression of the CoAP header may be done in conjunction with the Compression of the CoAP header MAY be done in conjunction with the
above layers (IPv6/UDP) or independently. The SCHC adaptation layers above layers (IPv6/UDP) or independently. The SCHC adaptation layers
as described in [I-D.ietf-lpwan-ipv6-static-context-hc] may be used as described in [I-D.ietf-lpwan-ipv6-static-context-hc] may be used
as as shown in the Figure 1. as shown in Figure 1.
^ +------------+ ^ +------------+ ^ +------------+ ^ +------------+ ^ +------------+ ^ +------------+
| | CoAP | | | CoAP | inner | | CoAP | | | CoAP | | | CoAP | inner | | CoAP |
| +------------+ v +------------+ x | OSCORE | | +------------+ v +------------+ x | OSCORE |
| | UDP | | DTLS | outer | +------------+ | | UDP | | DTLS | outer | +------------+
| +------------+ +------------+ | | UDP | | +------------+ +------------+ | | UDP |
| | IPv6 | | UDP | | +------------+ | | IPv6 | | UDP | | +------------+
v +------------+ +------------+ | | IPv6 | v +------------+ +------------+ | | IPv6 |
| IPv6 | v +------------+ | IPv6 | v +------------+
+------------+ +------------+
Figure 1: rule scope for CoAP Figure 1: rule scope for CoAP
Figure 1 shows some examples for CoAP architecture and the SCHC Figure 1 shows some examples for CoAP architecture and the SCHC
rule's scope. A rule can covers all headers from IPv6 to CoAP, SCHC rule's scope. A rule can cover all headers from IPv6 to CoAP, in
C/D is done in the device and at the LPWAN boundary. If an end-to- which case SCHC C/D is performed at the device and at the LPWAN
end encryption mechanisms is used between the device and the boundary. If an end-to-end encryption mechanisms is used between the
application. CoAP must be compressed independently of the other device and the application, CoAP MAY be compressed independently of
layers. The rule ID and the compression residue are encrypted using the other layers. The rule ID and the compression residue are
a mechanism such as DTLS. Only the other end can decipher the encrypted using a mechanism such as DTLS. Only the other end can
information. decipher the information.
Layers below may also be compressed using other SCHC rules (this is Layers below may also be compressed using other SCHC rules (this is
out of the scope of this document). OSCORE out of the scope of this document). OSCORE
[I-D.ietf-core-object-security] can also define 2 rules to compress [I-D.ietf-core-object-security] can also define 2 rules to compress
the CoAP message. A first rule focuses on the inner header and is the CoAP message. A first rule focuses on the inner header and is
end to end, a second rule may compress the outer header and the layer end to end, a second rule may compress the outer header and the
above. SCHC C/D for inner header is done by both ends, SCHC C/D for layers below. SCHC C/D for inner header is done by both ends, SCHC
outer header and other headers is done between the device and the C/D for outer header and other headers is done between the device and
LPWAN boundary. the LPWAN boundary.
3. CoAP Compression with SCHC 3. CoAP Compression with SCHC
CoAP differs from IPv6 and UDP protocols on the following aspects: CoAP differs from IPv6 and UDP protocols on the following aspects:
o IPv6 and UDP are symmetrical protocols. The same fields are found o IPv6 and UDP are symmetrical protocols. The same fields are found
in the request and in the response, only the location in the in the request and in the response, only the location in the
header may vary (e.g. source and destination fields). A CoAP header may vary (e.g. source and destination fields). A CoAP
request is different from a response. For example, the URI-path request is different from a response. For example, the URI-path
option is mandatory in the request and is not found in the option is mandatory in the request and is not found in the
response, a request may contain an Accept option and the response response, a request may contain an Accept option and the response
a Content option. a Content option.
[I-D.ietf-lpwan-ipv6-static-context-hc] defines the use of a [I-D.ietf-lpwan-ipv6-static-context-hc] defines the use of a
message direction (DI) when processing the rule which allows the message direction (DI) in the Field Description, which allows a
description of message header format in both directions. single Rule to process message headers differently in both
directions.
o Even when a field is "symmetric" (i.e. found in both directions) o Even when a field is "symmetric" (i.e. found in both directions)
the values carried in each direction are different. Combined with the values carried in each direction are different. Combined with
a matching list in the TV, this will allow to reduce the range of a matching list in the TV, this allows reducing the range of
expected values in a particular direction and therefore reduce the expected values in a particular direction and therefore reduce the
size of a compression residue. For instance, if a client sends size of the compression residue. For instance, if a client sends
only CON request, the type can be elided by compression and the only CON request, the type can be elided by compression and the
answer may use one bit to carry either the ACK or RST type. Same answer may use one single bit to carry either the ACK or RST type.
behavior can be applied to the CoAP Code field (0.0X code are The same behavior can be applied to the CoAP Code field (0.0X code
present in the request and Y.ZZ in the answer). The direction are present in the request and Y.ZZ in the answer). The direction
allows to split in two parts the possible values for each allows splitting in two parts the possible values for each
direction. direction.
o In IPv6 and UDP header fields have a fixed size. In CoAP, Token o In IPv6 and UDP, header fields have a fixed size. In CoAP, Token
size may vary from 0 to 8 bytes, length is given by a field in the size may vary from 0 to 8 bytes, the length being given by a field
header. More systematically, the CoAP options are described using in the header. More systematically, the CoAP options are
the Type-Length-Value. described using the Type-Length-Value.
[I-D.ietf-lpwan-ipv6-static-context-hc] offers the possibility to [I-D.ietf-lpwan-ipv6-static-context-hc] offers the possibility to
define a function for the Field Length in the Field Description. define a function for the Field Length in the Field Description.
o In CoAP headers, a field can be duplicated several times, for o In CoAP headers, a field can be present several times. This is
instances, elements of an URI (path or queries). The position typical for elements of an URI (path or queries). The position
defined in a rule, associated to a Field ID, can be used to defined in a rule, associated to a Field ID, can be used to
identify the proper element. identify the proper instance.
[I-D.ietf-lpwan-ipv6-static-context-hc] allows a Field id to [I-D.ietf-lpwan-ipv6-static-context-hc] allows a Field ID to
appears several times in the rule, the Field Position (FP) removes appears several times in the rule, the Field Position (FP) removes
ambiguities for the matching operation. ambiguities for the matching operation.
o Field size defined in the CoAP protocol can be too large regarding o Field sizes defined in the CoAP protocol can be too large
LPWAN traffic constraints. This is particularly true for the regarding LPWAN traffic constraints. This is particularly true
message ID field or Token field. The use of MSB MO can be used to for the message ID field or Token field. The MSB MO can be used
reduce the information carried on LPWANs. to reduce the information carried on LPWANs.
o CoAP also obeys to the client/server paradigm and the compression o CoAP also obeys the client/server paradigm and the compression
rate can be different if the request is issued from an LPWAN node ratio can be different if the request is issued from an LPWAN
or from an non LPWAN device. For instance a Device (Dev) aware of device or from an non LPWAN device. For instance a Device (Dev)
LPWAN constraints can generate a 1 byte token, but a regular CoAP aware of LPWAN constraints can generate a 1 byte token, but a
client will certainly send a larger token to the Thing. SCHC regular CoAP client will certainly send a larger token to the Dev.
compression will not modify the values to offer a better SCHC compression will not modify the values to offer a better
compression rate. Nevertheless a proxy placed before the compression rate. Nevertheless, a proxy placed before the
compressor may change some field values to offer a better compressor may change some field values to offer a better
compression rate and maintain the necessary context for compression ratio and maintain the necessary context for
interoperability with existing CoAP implementations. interoperability with existing CoAP implementations.
4. Compression of CoAP header fields 4. Compression of CoAP header fields
This section discusses of the compression of the different CoAP This section discusses the compression of the different CoAP header
header fields. fields.
4.1. CoAP version field 4.1. CoAP version field
This field is bidirectional and must be elided during the SCHC This field is bidirectional and MUST be elided during the SCHC
compression, since it always contains the same value. In the future, compression, since it always contains the same value. In the future,
if new version of CoAP are defined, new rules ID will be defined if new versions of CoAP are defined, new rules will be defined to
avoiding ambiguities between versions. avoid ambiguities between versions.
4.2. CoAP type field 4.2. CoAP type field
[rfc7252] defines 4 types of messages: CON, NON, ACK and RST. The [rfc7252] defines 4 types of messages: CON, NON, ACK and RST. The
latter two ones are a response of the two first ones. If the device last two are a response to the first two. If the device plays a
plays a specific role, a rule can exploit these property with the specific role, a rule can exploit these properties with the mapping
mapping list: [CON, NON] for one direction and [ACK, RST] for the list: [CON, NON] for one direction and [ACK, RST] for the other
other direction. Compression residue is reduced to 1 bit. direction. Compression residue is reduced to 1 bit.
The field must be elided if for instance a client is sending only NON The field SHOULD be elided if for instance a client is sending only
or CON messages. NON or CON messages.
In any case, a rule must be defined to carry RST to a client. In any case, a rule MUST be defined to carry RST to a client.
4.3. CoAP code field 4.3. CoAP code field
The compression of the CoAP code field follows the same principle as The compression of the CoAP code field follows the same principle as
for the CoAP type field. If the device plays a specific role, the for the CoAP type field. If the device plays a specific role, the
set of code values can be split in two parts, the request codes with set of code values can be split in two parts, the request codes with
the 0 class and the response values. the 0 class and the response values.
If the device implement only a CoAP client, the request code can be If the device only implements a CoAP client, the request code can be
reduced to the set of request the client is able to process. reduced to the set of requests the client is able to process.
All the response codes should be compressed with a SCHC rule. All the response codes MUST be compressed with a SCHC rule.
4.4. CoAP Message ID field 4.4. CoAP Message ID field
This field is bidirectional and is used to manage acknowledgments. This field is bidirectional and is used to manage acknowledgments.
Server memorizes the value for a EXCHANGE_LIFETIME period (by default The server memorizes the value for a EXCHANGE_LIFETIME period (by
247 seconds) for CON messages and a NON_LIFETIME period (by default default 247 seconds) for CON messages and a NON_LIFETIME period (by
145 seconds) for NON messages. During that period, a server default 145 seconds) for NON messages. During that period, a server
receiving the same Message ID value will process the message as a receiving the same Message ID value will process the message as a
retransmission. After this period, it will be processed as a new retransmission. After this period, it will be processed as a new
messages. message.
In case the Device is a client, the size of the message ID field may In case the Device is a client, the size of the message ID field may
the too large regarding the number of messages sent. Client may use be too large regarding the number of messages sent. The client
only small message ID values, for instance 4 bit long. Therefore a SHOULD use only small message ID values, for instance 4 bit long.
MSB can be used to limit the size of the compression residue. Therefore, a MSB can be used to limit the size of the compression
residue.
In case the Device is a server, client may be located outside of the In case the Device is a server, the client may be located outside of
LPWAN area and view the device as a regular device connected to the the LPWAN area and view the Device as a regular device connected to
internet. The client will generate Message ID using the 16 bits the internet. The client will generate Message ID using the 16 bits
space offered by this field. A CoAP proxy can be set before the SCHC space offered by this field. A CoAP proxy can be set before the SCHC
C/D to reduce the value of the Message ID, to allow its compression C/D to reduce the value of the Message ID, to allow its compression
with the MSB matching operator and LSB CDA. with the MSB matching operator and LSB CDA.
4.5. CoAP Token fields 4.5. CoAP Token fields
Token is defined through two CoAP fields, Token Length in the Token is defined through two CoAP fields, Token Length in the
mandatory header and Token Value directly following the mandatory mandatory header and Token Value directly following the mandatory
CoAP header. CoAP header.
Token Length is processed as any protocol field. If the value Token Length is processed as any protocol field. If the value
remains the same during all the transaction, the size can be stored remains the same during all the transaction, the size can be stored
in the context and elided during the transmission. Otherwise it will in the context and elided during the transmission. Otherwise, it
have to the send as a compression residue. will have to the sent as a compression residue.
Token Value size should not be defined directly in the rule in the Token Value size cannot be defined directly in the rule in the Field
Field Length (FL). Instead a specific function designed as "TKL" Length (FL). Instead, a specific function designated as "TKL" MUST
must be used and length do not have to the sent with the residue. be used and length does not have to the sent with the residue.
During the decompression, this function returns the value contained During the decompression, this function returns the value contained
in the Token Length field. in the Token Length field.
5. CoAP options 5. CoAP options
5.1. CoAP Content and Accept options. 5.1. CoAP Content and Accept options.
These field are both unidirectional and must not be set to These fields are both unidirectional and MUST NOT be set to
bidirectional in a rule entry. bidirectional in a rule entry.
If single value is expected by the client, it can be stored in the TV If a single value is expected by the client, it can be stored in the
and elided during the transmission. Otherwise, if several possible TV and elided during the transmission. Otherwise, if several
values are expected by the client, a matching-list should be used to possible values are expected by the client, a matching-list SHOULD be
limit the size of the residue. If is not possible, the value has to used to limit the size of the residue. If is not possible, the value
be sent as a residue (fixed or variable length). has to be sent as a residue (fixed or variable length).
5.2. CoAP option Max-Age field, CoAP option Uri-Host and Uri-Port 5.2. CoAP option Max-Age field, CoAP option Uri-Host and Uri-Port
fields fields
This field is unidirectional and must not be set to bidirectional in These fields is unidirectional and MUST NOT be set to bidirectional
a rule entry. It is used only by the server to inform of the caching in a rule entry. It is used only by the server to inform of the
duration and is never found in client requests. caching duration and is never found in client requests.
If the duration is known by both ends, value can be elided on the If the duration is known by both ends, the value can be elided on the
LPWAN. LPWAN.
A matching list can be used if some well-known values are defined. A matching list can be used if some well-known values are defined.
Otherwise these options should be sent as a residue (fixed or Otherwise these options SHOULD be sent as a residue (fixed or
variable length). variable length).
5.3. CoAP option Uri-Path and Uri-Query fields 5.3. CoAP option Uri-Path and Uri-Query fields
This fields are unidirectional and must not be set to bidirectional These fields are unidirectional and MUST NOT be set to bidirectional
in a rule entry. They are used only by the client to access to a in a rule entry. They are used only by the client to access a
specific resource and are never found in server responses. specific resource and are never found in server responses.
Uri-Path and Uri-Query elements are a repeatable options, the Field Uri-Path and Uri-Query elements are a repeatable options, the Field
Position (FP) gives the position in the path. Position (FP) gives the position in the path.
A Mapping list can be used to reduce size of variable Paths or A Mapping list can be used to reduce the size of variable Paths or
Queries. In that case, to optimize the compression, several elements Queries. In that case, to optimize the compression, several elements
can be regrouped into a single entry. Numbering of elements do not can be regrouped into a single entry. Numbering of elements do not
change, MO comparison is set with the first element of the matching. change, MO comparison is set with the first element of the matching.
FID FL FP DI TV MO CDA FID FL FP DI TV MO CDA
URI-Path 1 up ["/a/b", equal not-sent URI-Path 1 up ["/a/b", equal not-sent
"/c/d"] "/c/d"]
URI-Path 3 up ignore value-sent URI-Path 3 up ignore value-sent
Figure 2: complex path example Figure 2: complex path example
In Figure 2 a single bit residue can be used to code one of the 2 In Figure 2 a single bit residue can be used to code one of the 2
paths. If regrouping was not allowed, a 2 bits residue is needed. paths. If regrouping were not allowed, a 2 bits residue would be
needed.
5.3.1. Variable length Uri-Path and Uri-Query 5.3.1. Variable length Uri-Path and Uri-Query
When the length is known at the rule creation, the Field Length must When the length is not known at the rule creation, the Field Length
be set to variable, and the unit is set to bytes. SHOULD be set to variable, and the unit is set to bytes.
The MSB MO can be apply to a Uri-Path or Uri-Query element. Since The MSB MO can be applied to a Uri-Path or Uri-Query element. Since
MSB value is given in bit, the size must always be a multiple of 8 MSB value is given in bit, the size MUST always be a multiple of 8
bits and the LSB CDA must not carry any value. bits.
The length sent at the beginning of a variable length residue The length sent at the beginning of a variable length residue
indicates the size of the LSB in bytes. indicates the size of the LSB in bytes.
For instance for a CoMi path /c/X6?k="eth0" the rule can be set to: For instance for a CORECONF path /c/X6?k="eth0" the rule can be set
to:
FID FL FP DI TV MO CDA FID FL FP DI TV MO CDA
URI-Path 1 up "c" equal not-sent URI-Path 1 up "c" equal not-sent
URI-Path 2 up ignore value-sent URI-Path 2 up ignore value-sent
URI-Query 1 up "k=" MSB (16) LSB URI-Query 1 up "k=" MSB (16) LSB
Figure 3: CoMi URI compression Figure 3: CORECONF URI compression
Figure 3 shows the parsing and the compression of the URI. where c is Figure 3 shows the parsing and the compression of the URI, where c is
not sent. The second element is sent with the length (i.e. 0x2 X 6) not sent. The second element is sent with the length (i.e. 0x2 X 6)
followed by the query option (i.e. 0x05 "eth0"). followed by the query option (i.e. 0x05 "eth0").
5.3.2. Variable number of path or query elements 5.3.2. Variable number of path or query elements
The number of Uri-path or Uri-Query element in a rule is fixed at the The number of Uri-path or Uri-Query elements in a rule is fixed at
rule creation time. If the number varies, several rules should be the rule creation time. If the number varies, several rules SHOULD
created to cover all the possibilities. Another possibilities is to be created to cover all the possibilities. Another possibility is to
define the length of Uri-Path to variable and send a compression define the length of Uri-Path to variable and send a compression
residue with a length of 0 to indicate that this Uri-Path is empty. residue with a length of 0 to indicate that this Uri-Path is empty.
This add 4 bits to the compression residue. This adds 4 bits to the compression residue.
5.4. CoAP option Size1, Size2, Proxy-URI and Proxy-Scheme fields 5.4. CoAP option Size1, Size2, Proxy-URI and Proxy-Scheme fields
These fields are unidirectional and must not be set to bidirectional These fields are unidirectional and MUST NOT be set to bidirectional
in a rule entry. They are used only by the client to access to a in a rule entry. They are used only by the client to access a
specific resource and are never found in server response. specific resource and are never found in server response.
If the field value must be sent, TV is not set, MO is set to "ignore" If the field value has to be sent, TV is not set, MO is set to
and CDA is set to "value-sent. A mapping can also be used. "ignore" and CDA is set to "value-sent". A mapping MAY also be used.
Otherwise the TV is set to the value, MO is set to "equal" and CDA is Otherwise, the TV is set to the value, MO is set to "equal" and CDA
set to "not-sent" is set to "not-sent".
5.5. CoAP option ETag, If-Match, If-None-Match, Location-Path and 5.5. CoAP option ETag, If-Match, If-None-Match, Location-Path and
Location-Query fields Location-Query fields
These fields are unidirectional. These fields are unidirectional.
These fields values cannot be stored in a rule entry. They must These fields values cannot be stored in a rule entry. They MUST
always be sent with the compression residues. always be sent with the compression residues.
6. Other RFCs 6. Other RFCs
6.1. Block 6.1. Block
Block [rfc7959] allows a fragmentation at the CoAP level. SCHC Block [rfc7959] allows a fragmentation at the CoAP level. SCHC also
includes also a fragmentation protocol. They are compatible. If a includes a fragmentation protocol. They are compatible. If a block
block option is used, its content must be sent as a compression option is used, its content MUST be sent as a compression residue.
residue.
6.2. Observe 6.2. Observe
[rfc7641] defines the Observe option. The TV is not set, MO is set [rfc7641] defines the Observe option. The TV is not set, MO is set
to "ignore" and the CDA is set to "value-sent". SCHC does not limit to "ignore" and the CDA is set to "value-sent". SCHC does not limit
the maximum size for this option (3 bytes). To reduce the the maximum size for this option (3 bytes). To reduce the
transmission size either the device implementation should limit the transmission size, either the device implementation MAY limit the
delta between two consecutive value or a proxy can modify the delta between two consecutive values, or a proxy can modify the
incrementation. increment.
Since RST message may be sent to inform a server that the client does Since an RST message may be sent to inform a server that the client
not require Observe response, a rule must allow the transmission of does not require Observe response, a rule MUST allow the transmission
this message. of this message.
6.3. No-Response 6.3. No-Response
[rfc7967] defines an No-Response option limiting the responses made [rfc7967] defines a No-Response option limiting the responses made by
by a server to a request. If the value is not known by both ends, a server to a request. If the value is known by both ends, then TV
then TV is set to this value, MO is set to "equal" and CDA is set to is set to this value, MO is set to "equal" and CDA is set to "not-
"not-sent". sent".
Otherwise, if the value is changing over time, TV is not set, MO is Otherwise, if the value is changing over time, TV is not set, MO is
set to "ignore" and CDA to "value-sent". A matching list can also be set to "ignore" and CDA to "value-sent". A matching list can also be
used to reduce the size. used to reduce the size.
6.4. Time Scale 6.4. Time Scale
Time scale [I-D.toutain-core-time-scale] option allows a client to The time scale [I-D.toutain-core-time-scale] option allows a client
inform the server that it is in a slow network and that message ID to inform the server that it is in a constrained network and that
should be kept for a duration given by the option. message ID MUST be kept for a duration given by the option.
If the value is not known by both ends, then TV is set to this value, If the value is known by both ends, then TV is set to this value, MO
MO is set to "equal" and CDA is set to "not-sent". is set to "equal" and CDA is set to "not-sent".
Otherwise, if the value is changing over time, TV is not set, MO is Otherwise, if the value is changing over time, TV is not set, MO is
set to "ignore" and CDA to "value-sent". A matching list can also be set to "ignore" and CDA to "value-sent". A matching list can also be
used to reduce the size. used to reduce the size.
6.5. OSCORE 6.5. OSCORE
OSCORE [I-D.ietf-core-object-security] defines end-to-end protection OSCORE [I-D.ietf-core-object-security] defines end-to-end protection
for CoAP messages. This section describes how SCHC rules can be for CoAP messages. This section describes how SCHC rules can be
applied to compress OSCORE-protected messages. applied to compress OSCORE-protected messages.
skipping to change at page 11, line 46 skipping to change at page 12, line 4
This draft recommends to implement a parser that is able to identify This draft recommends to implement a parser that is able to identify
the OSCORE Option and the fields it contains. the OSCORE Option and the fields it contains.
Conceptually, it discerns up to 4 distinct pieces of information Conceptually, it discerns up to 4 distinct pieces of information
within the OSCORE option: the flag bits, the piv, the kid context, within the OSCORE option: the flag bits, the piv, the kid context,
and the kid. It is thus recommended that the parser split the OSCORE and the kid. It is thus recommended that the parser split the OSCORE
option into the 4 subsequent fields: option into the 4 subsequent fields:
o CoAP OSCORE_flags, o CoAP OSCORE_flags,
o CoAP OSCORE_piv, o CoAP OSCORE_piv,
o CoAP OSCORE_kidctxt, o CoAP OSCORE_kidctxt,
o CoAP OSCORE_kid. o CoAP OSCORE_kid.
These fields are superposed on the OSCORE Option format in Figure 4, These fields are shown superimposed on the OSCORE Option format in
the CoAP OSCORE_kidctxt field including the size bits s. Their size Figure 4, the CoAP OSCORE_kidctxt field including the size bits s.
may be reduced using the MSB matching operator. Their size SHOULD be reduced using the MSB matching operator.
7. Examples of CoAP header compression 7. Examples of CoAP header compression
7.1. Mandatory header with CON message 7.1. Mandatory header with CON message
In this first scenario, the LPWAN compressor receives from outside In this first scenario, the LPWAN compressor at the Network Gateway
client a POST message, which is immediately acknowledged by the side receives from a client on the Internet a POST message, which is
Device. For this simple scenario, the rules are described Figure 5. immediately acknowledged by the Device. For this simple scenario,
the rules are described Figure 5.
Rule ID 1 Rule ID 1
+-------------+--+--+--+------+---------+-------------++------------+ +-------------+--+--+--+------+---------+-------------++------------+
| Field. |FL|FP|DI|Target| Match | CDA || Sent | | Field |FL|FP|DI|Target| Match | CDA || Sent |
| | | | |Value | Opera. | || [bits] | | | | | |Value | Opera. | || [bits] |
+-------------+--+--+--+------+---------+-------------++------------+ +-------------+--+--+--+------+---------+-------------++------------+
|CoAP version | | |bi| 01 |equal |not-sent || | |CoAP version | | |bi| 01 |equal |not-sent || |
|CoAP version | | |bi| 01 |equal |not-sent || | |CoAP version | | |bi| 01 |equal |not-sent || |
|CoAP Type | | |dw| CON |equal |not-sent || | |CoAP Type | | |dw| CON |equal |not-sent || |
|CoAP Type | | |up|[ACK, | | || | |CoAP Type | | |up|[ACK, | | || |
| | | | | RST] |match-map|matching-sent|| T | | | | | | RST] |match-map|matching-sent|| T |
|CoAP TKL | | |bi| 0 |equal |not-sent || | |CoAP TKL | | |bi| 0 |equal |not-sent || |
|CoAP Code | | |bi| ML1 |match-map|matching-sent|| CC CCC | |CoAP Code | | |bi| ML1 |match-map|matching-sent|| CC CCC |
|CoAP MID | | |bi| 0000 |MSB(7 ) |LSB(9) || M-ID| |CoAP MID | | |bi| 0000 |MSB(7 ) |LSB(9) || M-ID|
skipping to change at page 18, line 32 skipping to change at page 19, line 5
Original msg length: 10 Original msg length: 10
Figure 11: CoAP CONTENT Response Figure 11: CoAP CONTENT Response
The SCHC Rules for the Inner Compression include all fields that are The SCHC Rules for the Inner Compression include all fields that are
already present in a regular CoAP message, what is important is the already present in a regular CoAP message, what is important is the
order of appearance and inclusion of only those CoAP fields that go order of appearance and inclusion of only those CoAP fields that go
into the Plaintext, Figure 12. into the Plaintext, Figure 12.
Rule ID 0 Rule ID 0
+---------------+--+--+-----------+-----------+-----------++------+ <<<<<<< Updated upstream
| Field |FP|DI| Target | MO | CDA || Sent | +---------------+--+--+-----------+-----------+-----------++------+
| | | | Value | | ||[bits]| | Field |FP|DI| Target | MO | CDA || Sent |
+---------------+--+--+-----------+-----------+-----------++------+ | | | | Value | | ||[bits]|
|CoAP Code | |up| 1 | equal |not-sent || | +---------------+--+--+-----------+-----------+-----------++------+
|CoAP Code | |dw|[69,132] | match-map |match-sent || c | |CoAP Code | |up| 1 | equal |not-sent || |
|CoAP Uri-Path | |up|temperature| equal |not-sent || | |CoAP Code | |dw|[69,132] | match-map |match-sent || c |
|COAP Option-End| |dw| 0xFF | equal |not-sent || | |CoAP Uri-Path | |up|temperature| equal |not-sent || |
+---------------+--+--+-----------+-----------+-----------++------+ |COAP Option-End| |dw| 0xFF | equal |not-sent || |
+---------------+--+--+-----------+-----------+-----------++------+
=======
+----------------+--+--+-----------+-----------+-----------++--------+
| Field |FP|DI| Target | MO | CDA || Sent |
| | | | Value | | || [bits] |
+----------------+--+--+-----------+-----------+-----------++--------+
|CoAP Code | |up| 1 | equal |not-sent || |
|CoAP Code | |dw|[69,132] | match-map |match-sent || c |
|CoAP Uri-Path | |up|temperature| equal |not-sent || |
|COAP Option-End | |dw| 0xFF | equal |not-sent || |
+----------------+--+--+-----------+-----------+-----------++--------+
>>>>>>> Stashed changes
Figure 12: Inner SCHC Rules Figure 12: Inner SCHC Rules
Figure 13 shows the Plaintext obtained for our example GET Request Figure 13 shows the Plaintext obtained for our example GET Request
and follows the process of Inner Compression and Encryption until we and follows the process of Inner Compression and Encryption until we
end up with the Payload to be added in the outer OSCORE Message. end up with the Payload to be added in the outer OSCORE Message.
In this case the original message has no payload and its resulting In this case the original message has no payload and its resulting
Plaintext can be compressed up to only 1 byte (size of the Rule ID). Plaintext can be compressed up to only 1 byte (size of the Rule ID).
The AEAD algorithm preserves this length in its first output, but The AEAD algorithm preserves this length in its first output, but
also yields a fixed-size tag which cannot be compressed and must be also yields a fixed-size tag which cannot be compressed and has to be
included in the OSCORE message. This translates into an overhead in included in the OSCORE message. This translates into an overhead in
total message length, which limits the amount of compression that can total message length, which limits the amount of compression that can
be achieved and plays into the cost of adding security to the be achieved and plays into the cost of adding security to the
exchange. exchange.
________________________________________________________ ________________________________________________________
| | | |
| OSCORE Plaintext | | OSCORE Plaintext |
| | | |
| 0x01bb74656d7065726174757265 (13 bytes) | | 0x01bb74656d7065726174757265 (13 bytes) |
skipping to change at page 20, line 7 skipping to change at page 20, line 48
| encrypted_plaintext = 0xa2 (1 byte) | | encrypted_plaintext = 0xa2 (1 byte) |
| tag = 0xc54fe1b434297b62 (8 bytes) | | tag = 0xc54fe1b434297b62 (8 bytes) |
| | | |
| ciphertext = 0xa2c54fe1b434297b62 (9 bytes) | | ciphertext = 0xa2c54fe1b434297b62 (9 bytes) |
|_________________________________________________| |_________________________________________________|
Figure 13: Plaintext compression and encryption for GET Request Figure 13: Plaintext compression and encryption for GET Request
In Figure 14 we repeat the process for the example CONTENT Response. In Figure 14 we repeat the process for the example CONTENT Response.
In this case the misalignment produced by the compression residue (1 In this case the misalignment produced by the compression residue (1
bit) makes it so that 7 bits of padding must be applied after the bit) makes it so that 7 bits of padding have to be applied after the
payload, resulting in a compressed Plaintext that is the same size as payload, resulting in a compressed Plaintext that is the same size as
before compression. This misalignment also causes the hexcode from before compression. This misalignment also causes the hexcode from
the payload to differ from the original, even though it has not been the payload to differ from the original, even though it has not been
compressed. On top of this, the overhead from the tag bytes is compressed. On top of this, the overhead from the tag bytes is
incurred as before. incurred as before.
________________________________________________________ ________________________________________________________
| | | |
| OSCORE Plaintext | | OSCORE Plaintext |
| | | |
skipping to change at page 21, line 49 skipping to change at page 22, line 4
v v
_________________________________________________________ _________________________________________________________
| | | |
| encrypted_plaintext = 0x10c6d7c26cc1 (6 bytes) | | encrypted_plaintext = 0x10c6d7c26cc1 (6 bytes) |
| tag = 0xe9aef3f2461e0c29 (8 bytes) | | tag = 0xe9aef3f2461e0c29 (8 bytes) |
| | | |
| ciphertext = 0x10c6d7c26cc1e9aef3f2461e0c29 (14 bytes) | | ciphertext = 0x10c6d7c26cc1e9aef3f2461e0c29 (14 bytes) |
|_________________________________________________________| |_________________________________________________________|
Figure 14: Plaintext compression and encryption for CONTENT Response Figure 14: Plaintext compression and encryption for CONTENT Response
The Outer SCHC Rules (Figure 17) MUST process the OSCORE Options
The Outer SCHC Rules (Figure 17) must process the OSCORE Options
fields. In Figure 15 and Figure 16 we show a dump of the OSCORE fields. In Figure 15 and Figure 16 we show a dump of the OSCORE
Messages generated from our example messages once they have been Messages generated from our example messages once they have been
provided with the Inner Compressed Ciphertext in the payload. These provided with the Inner Compressed Ciphertext in the payload. These
are the messages that are to go through Outer SCHC Compression. are the messages that are to go through Outer SCHC Compression.
Protected message: Protected message:
================== ==================
0x4102000182d7080904636c69656e74ffa2c54fe1b434297b62 0x4102000182d7080904636c69656e74ffa2c54fe1b434297b62
(25 bytes) (25 bytes)
skipping to change at page 24, line 5 skipping to change at page 24, line 5
certain options. certain options.
The piv field lends itself to having a number of bits masked off with The piv field lends itself to having a number of bits masked off with
MO MSB and CDA LSB. This could prove useful in applications where MO MSB and CDA LSB. This could prove useful in applications where
the message frequency is low such as that found in LPWAN the message frequency is low such as that found in LPWAN
technologies. Note that compressing the sequence numbers effectively technologies. Note that compressing the sequence numbers effectively
reduces the maximum amount of sequence numbers that can be used in an reduces the maximum amount of sequence numbers that can be used in an
exchange. Once this amount is exceeded, the SCHC Context would need exchange. Once this amount is exceeded, the SCHC Context would need
to be re-established. to be re-established.
The size s included in the kid context field may be masked off with The size s included in the kid context field MAY be masked off with
CDA MSB. The rest of the field could have additional bits masked CDA MSB. The rest of the field could have additional bits masked
off, or have the whole field be fixed with MO equal and CDA not-sent. off, or have the whole field be fixed with MO equal and CDA not-sent.
The same holds for the kid field. The same holds for the kid field.
Figure 17 shows a possible set of Outer Rules to compress the Outer Figure 17 shows a possible set of Outer Rules to compress the Outer
Header. Header.
Rule ID 0 Rule ID 0
+-------------------+--+--+--------------+--------+---------++------+ <<<<<<< Updated upstream
| Field |FP|DI| Target | MO | CDA || Sent | +-------------------+--+--+--------------+--------+---------++------+
| | | | Value | | ||[bits]| | Field |FP|DI| Target | MO | CDA || Sent |
+-------------------+--+--+--------------+--------+---------++------+ | | | | Value | | ||[bits]|
|CoAP version | |bi| 01 |equal |not-sent || | +-------------------+--+--+--------------+--------+---------++------+
|CoAP Type | |up| 0 |equal |not-sent || | |CoAP version | |bi| 01 |equal |not-sent || |
|CoAP Type | |dw| 2 |equal |not-sent || | |CoAP Type | |up| 0 |equal |not-sent || |
|CoAP TKL | |bi| 1 |equal |not-sent || | |CoAP Type | |dw| 2 |equal |not-sent || |
|CoAP Code | |up| 2 |equal |not-sent || | |CoAP TKL | |bi| 1 |equal |not-sent || |
|CoAP Code | |dw| 68 |equal |not-sent || | |CoAP Code | |up| 2 |equal |not-sent || |
|CoAP MID | |bi| 0000 |MSB(12) |LSB ||MMMM | |CoAP Code | |dw| 68 |equal |not-sent || |
|CoAP Token | |bi| 0x80 |MSB(5) |LSB ||TTT | |CoAP MID | |bi| 0000 |MSB(12) |LSB ||MMMM |
|CoAP OSCORE_flags | |up| 0x09 |equal |not-sent || | |CoAP Token | |bi| 0x80 |MSB(5) |LSB ||TTT |
|CoAP OSCORE_piv | |up| 0x00 |MSB(4) |LSB ||PPPP | |CoAP OSCORE_flags | |up| 0x09 |equal |not-sent || |
|COAP OSCORE_kid | |up|0x636c69656e70|MSB(52) |LSB ||KKKK | |CoAP OSCORE_piv | |up| 0x00 |MSB(4) |LSB ||PPPP |
|COAP OSCORE_kidctxt| |bi| b'' |equal |not-sent || | |COAP OSCORE_kid | |up|0x636c69656e70|MSB(52) |LSB ||KKKK |
|CoAP OSCORE_flags | |dw| b'' |equal |not-sent || | |COAP OSCORE_kidctxt| |bi| b'' |equal |not-sent || |
|CoAP OSCORE_piv | |dw| b'' |equal |not-sent || | |CoAP OSCORE_flags | |dw| b'' |equal |not-sent || |
|CoAP OSCORE_kid | |dw| b'' |equal |not-sent || | |CoAP OSCORE_piv | |dw| b'' |equal |not-sent || |
|COAP Option-End | |dw| 0xFF |equal |not-sent || | |CoAP OSCORE_kid | |dw| b'' |equal |not-sent || |
+-------------------+--+--+--------------+--------+---------++------+ |COAP Option-End | |dw| 0xFF |equal |not-sent || |
+-------------------+--+--+--------------+--------+---------++------+
=======
+-------------------+--+--+--------------+---------+-----------++--------+
| Field |FP|DI| Target | MO | CDA || Sent |
| | | | Value | | || [bits] |
+-------------------+--+--+--------------+---------+-----------++--------+
|CoAP version | |bi| 01 |equal |not-sent || |
|CoAP Type | |up| 0 |equal |not-sent || |
|CoAP Type | |dw| 2 |equal |not-sent || |
|CoAP TKL | |bi| 1 |equal |not-sent || |
|CoAP Code | |up| 2 |equal |not-sent || |
|CoAP Code | |dw| 68 |equal |not-sent || |
|CoAP MID | |bi| 0000 |MSB(12) |LSB ||MMMM |
|CoAP Token | |bi| 0x80 |MSB(5) |LSB ||TTT |
|CoAP OSCORE_flags | |up| 0x09 |equal |not-sent || |
|CoAP OSCORE_piv | |up| 0x00 |MSB(4) |LSB ||PPPP |
|COAP OSCORE_kid | |up|0x636c69656e70|MSB(52) |LSB ||KKKK |
|COAP OSCORE_kidctxt| |bi| b'' |equal |not-sent || |
|CoAP OSCORE_flags | |dw| b'' |equal |not-sent || |
|CoAP OSCORE_piv | |dw| b'' |equal |not-sent || |
|CoAP OSCORE_kid | |dw| b'' |equal |not-sent || |
|COAP Option-End | |dw| 0xFF |equal |not-sent || |
+-------------------+--+--+--------------+---------+-----------++--------+
>>>>>>> Stashed changes
Figure 17: Outer SCHC Rules Figure 17: Outer SCHC Rules
These Outer Rules are applied to the example GET Request and CONTENT These Outer Rules are applied to the example GET Request and CONTENT
Response. The resulting messages are shown in Figure 18 and Response. The resulting messages are shown in Figure 18 and
Figure 19. Figure 19.
Compressed message: Compressed message:
================== ==================
0x001489458a9fc3686852f6c4 (12 bytes) 0x001489458a9fc3686852f6c4 (12 bytes)
skipping to change at page 26, line 5 skipping to change at page 27, line 5
Compressed msg length: 16 bytes Compressed msg length: 16 bytes
Figure 19: SCHC-OSCORE Compressed CONTENT Response Figure 19: SCHC-OSCORE Compressed CONTENT Response
For contrast, we compare these results with what would be obtained by For contrast, we compare these results with what would be obtained by
SCHC compressing the original CoAP messages without protecting them SCHC compressing the original CoAP messages without protecting them
with OSCORE. To do this, we compress the CoAP messages according to with OSCORE. To do this, we compress the CoAP messages according to
the SCHC rules in Figure 20. the SCHC rules in Figure 20.
Rule ID 1 Rule ID 1
+---------------+--+--+-----------+---------+-----------++--------+ <<<<<<< Updated upstream
| Field |FP|DI| Target | MO | CDA || Sent | +---------------+--+--+-----------+---------+-----------++--------+
| | | | Value | | || [bits] | | Field |FP|DI| Target | MO | CDA || Sent |
+---------------+--+--+-----------+---------+-----------++--------+ | | | | Value | | || [bits] |
|CoAP version | |bi| 01 |equal |not-sent || | +---------------+--+--+-----------+---------+-----------++--------+
|CoAP Type | |up| 0 |equal |not-sent || | |CoAP version | |bi| 01 |equal |not-sent || |
|CoAP Type | |dw| 2 |equal |not-sent || | |CoAP Type | |up| 0 |equal |not-sent || |
|CoAP TKL | |bi| 1 |equal |not-sent || | |CoAP Type | |dw| 2 |equal |not-sent || |
|CoAP Code | |up| 2 |equal |not-sent || | |CoAP TKL | |bi| 1 |equal |not-sent || |
|CoAP Code | |dw| [69,132] |equal |not-sent || | |CoAP Code | |up| 2 |equal |not-sent || |
|CoAP MID | |bi| 0000 |MSB(12) |LSB ||MMMM | |CoAP Code | |dw| [69,132] |equal |not-sent || |
|CoAP Token | |bi| 0x80 |MSB(5) |LSB ||TTT | |CoAP MID | |bi| 0000 |MSB(12) |LSB ||MMMM |
|CoAP Uri-Path | |up|temperature|equal |not-sent || | |CoAP Token | |bi| 0x80 |MSB(5) |LSB ||TTT |
|COAP Option-End| |dw| 0xFF |equal |not-sent || | |CoAP Uri-Path | |up|temperature|equal |not-sent || |
+---------------+--+--+-----------+---------+-----------++--------+ |COAP Option-End| |dw| 0xFF |equal |not-sent || |
+---------------+--+--+-----------+---------+-----------++--------+
=======
+---------------+--+--+-----------+---------+-----------++------------+
| Field |FP|DI| Target | MO | CDA || Sent |
| | | | Value | | || [bits] |
+---------------+--+--+-----------+---------+-----------++------------+
|CoAP version | |bi| 01 |equal |not-sent || |
|CoAP Type | |up| 0 |equal |not-sent || |
|CoAP Type | |dw| 2 |equal |not-sent || |
|CoAP TKL | |bi| 1 |equal |not-sent || |
|CoAP Code | |up| 2 |equal |not-sent || |
|CoAP Code | |dw| [69,132] |equal |not-sent || |
|CoAP MID | |bi| 0000 |MSB(12) |LSB ||MMMM |
|CoAP Token | |bi| 0x80 |MSB(5) |LSB ||TTT |
|CoAP Uri-Path | |up|temperature|equal |not-sent || |
|COAP Option-End| |dw| 0xFF |equal |not-sent || |
+---------------+--+--+-----------+---------+-----------++------------+
>>>>>>> Stashed changes
Figure 20: SCHC-CoAP Rules (No OSCORE) Figure 20: SCHC-CoAP Rules (No OSCORE)
This yields the results in Figure 21 for the Request, and Figure 22 This yields the results in Figure 21 for the Request, and Figure 22
for the Response. for the Response.
Compressed message: Compressed message:
================== ==================
0x0114 0x0114
0x01 = Rule ID 0x01 = Rule ID
skipping to change at page 27, line 41 skipping to change at page 29, line 10
10. Acknowledgements 10. Acknowledgements
Thanks to all the persons that have give us feedback Thanks to all the persons that have give us feedback
11. Normative References 11. Normative References
[I-D.ietf-core-object-security] [I-D.ietf-core-object-security]
Selander, G., Mattsson, J., Palombini, F., and L. Seitz, Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
"Object Security for Constrained RESTful Environments "Object Security for Constrained RESTful Environments
(OSCORE)", draft-ietf-core-object-security-15 (work in (OSCORE)", draft-ietf-core-object-security-16 (work in
progress), August 2018. progress), March 2019.
[I-D.ietf-lpwan-ipv6-static-context-hc] [I-D.ietf-lpwan-ipv6-static-context-hc]
Minaburo, A., Toutain, L., Gomez, C., Barthel, D., and J. Minaburo, A., Toutain, L., Gomez, C., Barthel, D., and J.
Zuniga, "LPWAN Static Context Header Compression (SCHC) Zuniga, "LPWAN Static Context Header Compression (SCHC)
and fragmentation for IPv6 and UDP", draft-ietf-lpwan- and fragmentation for IPv6 and UDP", draft-ietf-lpwan-
ipv6-static-context-hc-18 (work in progress), December ipv6-static-context-hc-18 (work in progress), December
2018. 2018.
[I-D.toutain-core-time-scale] [I-D.toutain-core-time-scale]
Minaburo, A. and L. Toutain, "CoAP Time Scale Option", Minaburo, A. and L. Toutain, "CoAP Time Scale Option",
 End of changes. 77 change blocks. 
213 lines changed or deleted 269 lines changed or added

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