ETSI TS 118 110 V1.1.0 (2016-03)

ETSI TS 118 110 V1.1.0 (2016-03)






TECHNICAL SPECIFICATION
oneM2M;
MQTT Protocol Binding
(oneM2M TS-0010 version 1.5.1 Release 1)

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oneM2M TS-0010 version 1.5.1 Release 1 2 ETSI TS 118 110 V1.1.0 (2016-03)



Reference
RTS/oneM2M-000010v110
Keywords
IoT, M2M, protocol

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oneM2M TS-0010 version 1.5.1 Release 1 3 ETSI TS 118 110 V1.1.0 (2016-03)
Contents
Intellectual Property Rights . 5
Foreword . 5
1 Scope . 6
2 References . 6
2.1 Normative references . 6
2.2 Informative references . 7
3 Definitions and abbreviations . 7
3.1 Definitions . 7
3.2 Abbreviations . 7
4 Conventions . 7
5 Introduction . 8
5.1 Use of MQTT . 8
5.2 Binding overview . 8
5.2.1 Introduction. 8
5.2.2 Scenarios . 9
5.2.2.1 MQTT server co-located within a node . 9
5.2.2.2 MQTT server located independently from nodes . 10
5.2.3 Configurations . 10
5.2.3.1 AE to IN . 10
5.2.3.2 AE to MN . 11
5.2.3.3 MN to IN . 12
5.2.3.4 AE to MN to IN . 12
5.2.3.5 AE to IN (Independent scenario) . 13
5.2.3.6 AE to MN (Independent scenario) . 13
5.2.3.7 MN to IN (Independent scenario) . 13
5.2.3.8 AE to MN to IN (Independent scenario) . 14
6 Protocol Binding . 14
6.1 Introduction . 14
6.2 Use of MQTT . 15
6.3 Connecting to MQTT . 15
6.4 Sending and Receiving Messages . 16
6.4.1 Request and Response Messages . 16
6.4.2 Sending a Request . 17
6.4.3 Listening for and responding to a Request . 17
6.4.4 Initial Registration . 18
6.4.5 Request/Response Message Flow . 19
6.5 Primitive Mapping . 20
6.5.1 Request primitives . 20
6.5.2 Response primitives . 21
6.5.3 Serialization Format Negotiation . 22
6.6 Format used in pointOfAccess strings . 22
7 Security. 22
7.1 Introduction . 22
7.2 Authorization . 23
7.3 Authentication . 23
7.4 Authorization by the MQTT Server . 24
7.5 General Considerations . 25
Annex A (informative): Overview of MQTT . . 26
A.0 Introduction . 26
A.1 MQTT features . 26
A.2 MQTT implementations . 27
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A.3 MQTT Details . 27
A.3.1 Addressing a message - Topics and Subscriptions . 27
A.3.2 Reliability . 28
A.3.3 Retained Messages . 28
History . 29

ETSI

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oneM2M TS-0010 version 1.5.1 Release 1 5 ETSI TS 118 110 V1.1.0 (2016-03)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (https://ipr.etsi.org/).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This Technical Specification (TS) has been produced by ETSI Partnership Project oneM2M (oneM2M).
ETSI

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1 Scope
The present document specifies the binding of Mca and Mcc primitives (message flows) onto the MQTT protocol. It
specifies
1) How a CSE or AE connects to MQTT.
2) How an Originator (CSE or AE) formulates a Request as an MQTT message, and transmits it to its intended
Receiver.
3) How a Receiver listens for incoming Requests.
4) How that Receiver can formulate and transmit a Response.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
The following referenced documents are necessary for the application of the present document.
[1] OASIS MQTT Version 3.1.1 (29 October 2014). OASIS Standard. Edited by Andrew Banks and
Rahul Gupta.
NOTE: Available at http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html.
[2] ETSI TS 118 101: "oneM2M; Functional Architecture (oneM2M TS-0001)".
[3] ETSI TS 118 104: "oneM2M; Service Layer Core Protocol Specification (oneM2M TS-0004)".
[4] IETF RFC 793 (September 1981): "Transmission Control Protocol - DARPA Ineternet Program -
Protocol Specification", J. Postel.
NOTE: Available at http://www.ietf.org/rfc/rfc793.txt.
[5] IETF RFC 5246 (August 2008): "The Transport Layer Security (TLS) Protocol Version 1.2",
T. Dierks.
NOTE: Available at http://tools.ietf.org/html/rfc5246.
[6] IETF RFC 6455 (December 2011): "The WebSocket Protocol", I. Fette.
NOTE: Available at http://tools.ietf.org/html/rfc6455.
[7] ETSI TS 118 103: "oneM2M; Security Solutions (oneM2M TS-0003)".
[8] IETF RFC 3986 (January 2005): " Uniform Resource Identifier (URI): Generic Syntax", T.
Berners-Lee.
NOTE: Available at https://tools.ietf.org/html/rfc3986.


ETSI

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2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] oneM2M Drafting Rules.
NOTE: Available at http://ftp.onem2m.org/Others/Rules_Pages/oneM2M-Drafting-Rules-V1_0_1.doc
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
originator [2]: actor that initiates a Request
NOTE: An Originator can either be an Application or a CSE.
receiver [2]: actor that receives the Request
NOTE: A Receiver can be a CSE or an Application.
resource [2]: uniquely addressable entity in oneM2M System such as by the use of a Uniform Resource Identifier
(URI)
NOTE: A resource can be accessed and manipulated by using the specified procedures.
3.2 Abbreviations
For the purposes of the present document, the abbreviations given in ETSI TS 118 101 [2] and the following apply:
ADN Application Dedicated Node
ADN-AE AE which resides in the Application Dedicated Node
AE Application Entity
ASN Application Service Node
CSE Common Service Entity
IN Infrastructure Node
IN-AE Application Entity that is registered with the CSE in the Infrastructure Node
IN-CSE CSE which resides in the Infrastructure Node
MN Middle Node
MN-CSE CSE which resides in the Middle Node
TLS Transport Level Security
4 Conventions
The keywords "Shall", "Shall not", "May", "Need not", "Should", "Should not" in the present document are to be
interpreted as described in the oneM2M Drafting Rules [i.1].
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5 Introduction
5.1 Use of MQTT
This binding makes use of MQTT to provide reliable two-way communications between two parties (AEs and CSEs). It
uses the following features of MQTT:
• Durable Sessions, providing Store and Forward in cases where network connectivity is not available.
• MQTT's "QoS 1" message reliability level. This provides reliability without incurring the overhead implied by
QoS 2.
• NAT traversal (neither of the two parties is required to have prior knowledge of the other party's IP address).
• Dynamic topic creation and wild-carded subscription filters.
It does not use the following features:
• One-to-many publish/subscribe.
• Retained Messages.
• Will Messages.
• QoS 0 or QoS 2 message reliability levels.
5.2 Binding overview
5.2.1 Introduction
The MQTT protocol binding specifies how the Mca or Mcc request and response messages are transported across the
MQTT protocol. Both communicating parties (AEs and CSEs) typically make use of an MQTT client library, and the
communications are mediated via the MQTT server. There is no need for the client libraries or the server to be
provided by the same supplier, since the protocol they use to talk to each other is defined by the MQTT specification
[1].
Furthermore, the binding does not assume that the MQTT client libraries or server implementations are necessarily
aware that they are being used to carry Mca, Mcc or any other oneM2M-defined primitives.
The binding is defined in terms of the MQTT protocol flows that take place between the client libraries and the MQTT
server in order to effect the transport of an Mca or Mcc message.
There are two scenarios depending on the location of MQTT server: MQTT server co-located within a node, and MQTT
server located independently from nodes.
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5.2.2 Scenarios
5.2.2.1 MQTT server co-located within a node

Figure 5.2.2.1-1: MQTT server co-located scenario
Figure 5.2.2.1-1 shows a protocol segment view of the MQTT server co-located scenario. In this scenario, all oneM2M
nodes (ADN, ASN, MN, IN) include a MQTT client. MQTT servers are provided within MN and IN.
In this scenario, the protocol segments are illustrated as follows.
Table 5.2.2.1-1
Protocol Segment oneM2M Message Transported MQTT Interaction
PS1 Mca (AE of ADN to CSE of IN) Client in ADN to Server in IN
PS2 Mca (AE of ADN to CSE of MN) Client in ADN to Server in MN
PS3 Mcc (CSE of ASN to CSE of MN) Client in ASN to Server in MN
PS4 Mcc (CSE of ASN to CSE of IN) Client in ASN to Server in IN
PS5 Mcc (CSE of MN to CSE of MN) Client in MN to Server in MN
PS6 Mcc (CSE of MN to CSE of IN) Client in MN to Server in IN
PS7 Mcc' (CSE of IN to CSE of IN) Client in IN to Server in IN

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5.2.2.2 MQTT server located independently from nodes

Figure 5.2.2.2-1: MQTT server independently located scenario
Figure 5.2.2.2-1 shows a protocol segment view in which the MQTT server is located independently from the oneM2M
nodes. In this scenario, all oneM2M nodes (ADN, ASN, MN, IN) include a MQTT client. MQTT servers exists
independently, which means the servers are located outside of the nodes.
In this scenario, the protocol segments are illustrated as follows.
Table 5.2.2.2-1
Protocol Segment oneM2M Message Transported MQTT Interaction
PS1 Mca (AE of ADN to CSE of IN) Client in ADN to Server
PS2 Mca (AE of ADN to CSE of MN) Client in ADN to Server
PS3 Mcc (CSE of ASN to CSE of MN) Client in ASN to Server
PS4 Mcc (CSE of ASN to CSE of IN) Client in ASN to Server
PS5 Mcc (CSE of MN to CSE of MN) Client in MN to Server
Mcc (CSE of MN to CSE of ASN)
Mca (CSE of MN to AE of ADN)
PS6 Mcc (CSE of MN to CSE of MN) Client in MN to Server
PS7 Mcc (CSE of IN to CSE of MN) Client in IN to Server
Mcc (CSE of IN to CSE of ASN)
Mca (CSE of IN to AE of ADN)
PS8 Mcc' (CSE of IN to CSE of IN) Client in IN to Server

The next four clauses show the four configurations in which the MQTT binding can be used in the co-located scenario,
followed by similar configurations in the independently-located scenario.
NOTE: Other configurations are possible, but they are currently out of scope.
5.2.3 Configurations
5.2.3.1 AE to IN
This configuration, illustrated in figure 5.2.3.1-1, allows an AE to connect to an IN via MQTT.
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Figure 5.2.3.1-1: Using MQTT between AE and IN-CSE
The MQTT server is co-located with the IN-CSE and allows connection of the ADN-AEs (typically devices) and/or
IN-AEs. It can store and forward messages if there is a gap in the connectivity with the devices. Note that the AEs each
establish their own separate TCP/IP connection with the MQTT server. Thus the server shall have an accessible IP
address, but AEs need not have.
5.2.3.2 AE to MN
This configuration, illustrated in figure 5.2.3.2-1, allows an ADN-AE to connect to an IN via MQTT.

Figure 5.2.3.2-1: Using MQTT between AE and MN-CSE
This configuration is very similar to the AE-IN configuration shown in clause 5.2.3.1, except that the MQTT server is
hosted on the MN rather than the IN. Onwards connection to the IN-CSE is via a different transport protocol.
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5.2.3.3 MN to IN
This configuration, illustrated in figure 5.2.3.3-1, allows an MN to connect to an IN via MQTT.

Figure 5.2.3.3-1: Mcc using MQTT between MN and IN
The MQTT server is co-located with the IN-CSE and allows connection of the MNs (typically in-field gateway boxes).
It can store and forward messages if there is a gap in the connectivity with the gateways. Note that the MNs each
establish their own separate TCP/IP connections with the MQTT server. Thus the server shall have an accessible IP
address, but MNs need not have.
5.2.3.4 AE to MN to IN
This configuration, illustrated in figure 5.2.3.4-1, is a combination of the previous two.

Figure 5.2.3.4-1: Mca and Mcc both using MQTT
In this configuration the two MQTT servers are independent from each other (that is to say they do not have a shared
topic space). Any interactions between the ADN-AE and the IN-CSE are mediated by the MN-CSE.
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5.2.3.5 AE to IN (Independent scenario)
This configuration, illustrated in figure 5.2.3.5-1, allows an AE to connect to an IN via MQTT.

Figure 5.2.3.5-1: Using MQTT between AE and IN-CSE
The MQTT server is an independent entity, located outside of the nodes. In order to deliver Mca messages, MQTT
clients within ADN-AE/IN-AE and IN-CSE connect to the MQTT server. After the clients establish TCP/IP connection
with the MQTT server, Mca messages between ADN-AE/IN-AE and IN-CSE can be transported via the MQTT server.
5.2.3.6 AE to MN (Independent scenario)
This configuration, illustrated in figure 5.2.3.6-1, allows an ADN-AE to connect to an IN via MQTT.

Figure 5.2.3.6-1: Using MQTT between AE and MN-CSE
In this configuration, the MQTT server is an independent entity, located outside of the nodes. MQTT clients within
ADN-AE and MN-CSE are connected to the MQTT server, and the MQTT server stores and forwards the Mca
messages between ADN-AE and MN-CSE. In addition, this figure shows that the onwards connection to the IN-CSE is
via a different transport protocol.
5.2.3.7 MN to IN (Independent scenario)
This configuration, illustrated in figure 5.2.3.7-1, allows an MN to connect to an IN via MQTT.
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Figure 5.2.3.7-1: Mcc using MQTT between MN and IN
In this configuration, the MQTT server is an independent entity, located outside of nodes. Mcc message delivery
between MN-CSE and IN-CSE are performed via the independently located MQTT server. As introduced in the
previous clauses, in order to send messages, each MQTT client within MN-CSE and IN-CSE connects to the MQTT
server and Mcc messages are transported via MQTT server.
5.2.3.8 AE to MN to IN (Independent scenario)
This configuration, illustrated in figure 5.2.3.8-1, is a combination of the previous two.

Figure 5.2.3.8-1: Mca and Mcc both using MQTT
In this configuration, the MQTT clients of ADN-AE and MN-CSE and IN-CSE connect to the independently located
MQTT server. Any interactions such as Mca or Mcc message delivery among the ADN-AE and the MN-CSE and the
IN-CSE are mediated by the MQTT server.
6 Protocol Binding
6.1 Introduction
In this clause the use of MQTT is profiled and the key elements of the binding are defined:
1) How a CSE or AE connects to MQTT.
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2) How an Originator (CSE or AE) formulates a Request as an MQTT message, and transmits it to its intended
Receiver.
3) How a Receiver listens for incoming Requests, and how it formulates and transmits a Response.
4) How the Mca and Mcc CRUD operations map to MQTT messages.
For more information on MQTT itself see clause A or refer to the MQTT specification [1].
6.2 Use of MQTT
MQTT includes reliability features which allow recovery from loss of network connectivity without requiring explicit
involvement of the applications that are using it, however to do this it requires an underlying network protocol that
provides ordered, lossless, bi-directional connections. The MQTT specification [1] does not mandate a particular
underlying protocol, so this binding specification restricts the choice of underlying protocol: it shall be one of the
following:
• Raw TCP/IP [4].
• TCP/IP with Transport Level Security (TLS) [5].
• WebSocket [6] - either with or without the use of TLS.
6.3 Connecting to MQTT
In order to communicate, the two client parties (AE and CSE or CSE and CSE) shall connect to a common MQTT
server. The MQTT server shall be hosted in one of the two nodes or shall exist as an independent external entity,
following one of the configuration patterns shown in clause 5.2.
Once each party has located the address of the MQTT server, it then connects to it using the standard MQTT
CONNECT protocol packet. The following additional considerations apply:
• The CONNECT packet contains a Client Id as described in clause A.3.2. The Client Ids have to be unique at
least among all clients that connect to a given MQTT server instance (this is a requirement imposed by the
MQTT protocol). This condition will be satisfied if an AE uses its AE-ID and a CSE uses its CSE-ID. See
clause 7 of ETSI TS 118 101 [2] for a discussion of these Identifiers. The prefix A:: or C:: shall be added to
the ID to show whether it is an AE-ID or a CSE-ID as these ID spaces are not distinct.

The AE-ID or CSE-ID may not be known during the initial registration process, in which case the client shall
use some other appropriate unique ID.
• A client shall set the "Clean Session" flag in the CONNECT packet to false. This means that MQTT Session
state related to that client will be retained by the MQTT Server in the event of a disconnection (deliberate or
otherwise) of that client.
• A client shall not set the "Will Flag", so Will Messages are not enabled.
• A client may choose to provide a non-zero MQTT KeepAlive value or to provide a KeepAlive of 0 (this
disables the MQTT KeepAlive).
• The MQTT server may require that a client provides a User Name and a password (or other credential). For
more information see clause 7.
A client might choose to keep the MQTT connection open permanently (restarting it as soon as possible after any
unforeseen connection loss), it might choose to connect only when it wants to act as an Originator, or it might choose to
connect based on the associated with a relevant oneM2M resource.
Once a client has connected to the MQTT server it can then communicate (subject to authorization policies) with any
other client connected to its server. There is no need for it to create another connection if it wants to communicate with
a different counter-party.
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When a client determines that it no longer wishes to participate in an MQTT Session with its MQTT Server it shall
perform the following steps:
• Disconnect from that server, if it is
...