wdiff draft-tschofenig-core-coap-tcp-tls-04.txt draft-tschofenig-core-coap-tcp-tls-05.txt

CORE C. Bormann, Ed.
Internet-Draft Universitaet Bremen TZI
Intended status: Standards Track S. Lemay
Expires: December 12, 2015 May 6, 2016 V. Solorzano Barboza
Zebra Technologies
H. Tschofenig
ARM Ltd.
June 10,
November 03, 2015

A TCP and TLS Transport for the Constrained Application Protocol (CoAP)
draft-tschofenig-core-coap-tcp-tls-04.txt
draft-tschofenig-core-coap-tcp-tls-05

Abstract

The Hypertext Transfer Protocol (HTTP) has been was designed with TCP as
an the
underlying transport protocol. The Constrained Application Protocol
(CoAP), which has been while inspired by HTTP, has on the other
hand been defined to make use of UDP. UDP
instead of TCP. Therefore, reliable delivery and a simple congestion
control and flow control mechanism are provided by the message layer
of the CoAP protocol.

A number of environments benefit from the use of CoAP directly over a
reliable byte stream that such as TCP, which already provides these
services. This document defines the use of CoAP over TCP as well as
CoAP over TLS.

Status of This Memo

This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering
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
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."

This Internet-Draft will expire on December 12, 2015. May 6, 2016.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Constrained Application Protocol . . . . . . . . . . . . . . 3
4. Message Format . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Discussion . . . . . . . . . . . . . . . . . . . . . . . 8 6
5. Message Transmission . . . . . . . . . . . . . . . . . . . . 8 6
6. CoAP URI . . . . . . . . . . . . . . . . . . . . . . . . . . 9 7
6.1. coap+tcp URI scheme . . . . . . . . . . . . . . . . . . . 9 7
6.2. coaps+tcp URI scheme . . . . . . . . . . . . . . . . . . 9 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 8
8.1. Service Name and Port Number Registration . . . . . . . . 10 8
8.2. URI Schemes . . . . . . . . . . . . . . . . . . . . . . . 11 9
8.3. ALPN Protocol ID . . . . . . . . . . . . . . . . . . . . 12 10
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 10
10.1. Normative References . . . . . . . . . . . . . . . . . . 12 10
10.2. Informative References . . . . . . . . . . . . . . . . . 13 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 11

1. Introduction

The Constrained Application Protocol (CoAP) [RFC7252] was designed
for Internet of Things (IoT) deployments, assuming that UDP can be
used freely - unimpeded -- UDP [RFC0768], or DTLS [RFC6347] over UDP, UDP; it is a
good choice for transferring small amounts of data in across networks
that follow the IP architecture. Some CoAP deployments, however, may
have to integrate well with existing enterprise infrastructure, where
the use of UDP-based protocols may not be well-received or may even
be blocked by firewalls. Middleboxes that are unaware of CoAP usage
for IoT can make the use of UDP brittle. brittle, resulting in lost or
malformed packets.

Where NATs are still present, CoAP over TCP can also help with their
traversal. NATs often calculate expiration timers based on the
transport layer protocol being used by application protocols. Many
NATs are built around the assumption that a transport layer protocol
such as TCP gives them additional information about the session life
cycle and keep TCP-based NAT bindings around for a longer period.
UDP
UDP, on the other hand hand, does not provide such information to a NAT
and timeouts tend to be much shorter, as research confirms
[HomeGateway].

Some environments may also benefit from the more sophisticated
congestion control capabilities provided by many TCP implementations.
(Note that there is ongoing work to add more elaborate congestion
control to CoAP as well, see [I-D.bormann-core-cocoa].)

Finally, CoAP may be integrated into a Web environment where the
front-end uses CoAP from IoT devices to a cloud infrastructure but
the CoAP messages are then transported in TCP between the back-end
services. A TCP-to-UDP gateway can be used at the cloud boundary to
talk to the UDP-based IoT.

To make both IoT devices work smoothly in these demanding environments,
CoAP needs to make use of a different transport protocol, namely TCP [RFC0793] and
[RFC0793], in some situations even secured by TLS [RFC5246].

The present document document describes a shim header that conveys length
information about each CoAP message included. message. Modifications to CoAP beyond
the replacement of the message layer (e.g., to introduce further
optimizations) are intentionally avoided.

2. Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].

3. Constrained Application Protocol

The interaction model of CoAP over TCP is very similar to the one for
CoAP over UDP UDP, with the key difference that using TCP voids the need
to provide certain transport layer protocol features, such as
reliable delivery, fragmentation and reassembly, as well as
congestion control, at the CoAP level. The protocol stack is
illustrated in Figure 1 (derived from [RFC7252], Figure 1).

+----------------------+
| Application |
+----------------------+
+----------------------+
| Requests/Responses | CoAP (RFC7252)
|----------------------|
| Message adapter | this document This Document
+----------------------+
+-----------+ ^
| TLS | |
+-----------+ v
+----------------------+
| TCP |
+----------------------+

Figure 1: The CoAP over TLS/TCP Protocol Stack

TCP offers features that are not available in UDP and consequently
have been provided in the message layer of CoAP.

Since TCP offers reliable delivery, there is no need to offer a
redundant acknowledgement at the CoAP messaging layer.

Hence,

Since there is no need to carry around acknowledgement semantics,
messages do not require a message type; no message layer
acknowledgement is expected or even possible. Because something
needs to be put into the two bits indicating the only message type transported when using CoAP over TCP (unless
alternative L3 below is chosen), we put the Non-Confirmable bits for a Non-
Confirmable message (NON). (NON) into the header. By the nature of TCP, a NON over TCP
is still
messages are always transmitted reliably. reliably over TCP. Figure 2 (derived
from [RFC7252], Figure 3) shows this message exchange graphically. A
UDP-to-TCP gateway will therefore discard all empty messages, such as
empty ACKs (after operating on them at the message layer), and re-pack re-
pack the contents of all non-empty CON, NON, or ACK messages (i.e.,
those ACK messages that have a piggy-backed response) into untyped
messages (that happen to look like NON messages. messages).

Similarly, there is no need to detect duplicate delivery of a
message. In UDP CoAP, the Message ID is used for relating
acknowledgements to Confirmable messages as well as for duplicate
detection. Since the Message ID thus is not meaningful over TCP, it
is elided (as indicated by the dashes in Figure 2).

Client Server
| |
| NON (no type) [------] |
+----------------->|
+-------------------->|
| |

Figure 2: NON Untyped Message Transmission over TCP.

As a result of removing the message layer in CoAP over TCP, there is
no longer a need to distinguish message types. Since the two-bit
field for the message needs to be filled with something, all messages
are marked with the bit combination indicating the NON type (no
message layer acknowledgement is expected or even possible).

A response is sent back as defined in [RFC7252], as illustrated in
Figure 3 (derived from [RFC7252], Figure 6).

Client Server
| |
| NON (no type) [------] |
| GET /temperature |
| (Token 0x74) |
+----------------->|
+------------------->|
| |
| NON (no type) [------] |
| 2.05 Content |
| (Token 0x74) |
| "22.5 C" |
|<-----------------+
|<-------------------+
| |

Figure 3: NON Request/Response. 3

4. Message Format

The CoAP message format defined in [RFC7252], as shown in Figure 4,
relies on the datagram transport (UDP, or DTLS over UDP) for keeping
the individual messages separate.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Ver| T | TKL | Code | Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Token (if any, TKL bytes) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options (if any) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1 1 1 1 1 1 1 1| Payload (if any) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 4: RFC 7252 defined CoAP Message Format.

In a stream oriented transport protocol such as TCP, some other a form of delimiting messages
message delimitation is needed. For this purpose, CoAP over TCP
introduces a length field. Figure 5 shows a 1-byte shim header
carrying length information prepending the CoAP message header.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Length Shim |Ver| T | |Ver|0 1| TKL | Code | Token (TKL
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Token (TKL bytes) ... | Options (if any) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1 1 1 1 1 1 1 1| Payload (if any) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 5: CoAP Header with prepended Shim Header.

-- Alternative L1 --

The 'Message Length' field is a 16-bit unsigned integer in network
byte order.

-- Alternative L2 --

The 'Message Length' field starts with an 8-bit unsigned integer.
Length encoding follows the same mechanism as "Major type 0" from the
CBOR specification [RFC7049]. The length field is indicated by the 5
least significant bits of the byte. Values are used as such:

o between 0b000_00001 and 0b000_10111 (1 to 23) indicates the actual
length of the following message

o 0b000_11000 (24) means an additional 8-bit unsigned Integer is
appended to the initial length field indicating the total length

o 0b000_11001 (25) means an additional 16-bit unsigned Integer (in
network byte order) is appended to the initial length field
indicating the total length

o 0b000_11010 (26) means an additional 32-bit unsigned Integer (in
network byte order) is appended to the initial length field
indicating the total length

The 3 most significant bits in the initial length field are reserved
for future use. If a recipient gets a message larger than it can
handle, it SHOULD if possible send back a 4.13 in accordance with
[RFC7252] section on error code.

-- Common for L1 and L2 Alternatives --

The "length" field It provides the length of the subsequent CoAP message
(including the CoAP header but excluding this message length field)
in bytes. T bytes (so its minimum value is always the code for NON (1).

-- Alternative L3 --

The initial byte of the frame contains two nibbles, in a similar way
to the CoAP option encoding (Section 3.1 of [RFC7252]). 2). The first
nibble is used to indicate the length of the options (including any
option delimiter), Message ID and the payload (if any); it does not include the
Code byte or the Token bytes. The first nibble is interpreted as a
4-bit unsigned integer. A value between 0 message
type are meaningless and 12 directly indicates
the length of the options/payload, in bytes. The other three values thus elided (what would have a special meaning:

13: An 8-bit unsigned integer follows the initial byte and indicates
the length of options/payload minus 13.

14: A 16-bit unsigned integer in network byte order follows the
initial byte and indicates the length of options/payload minus
269.

15: A 32-bit unsigned integer in network byte order follows the
initial byte and indicates the length of options/payload minus
65805.

The second nibble of the initial byte indicates been the token length.

Example: 01 43 7f
message type field is a frame just containing a 2.03 code always filled with what would be the
token 7f.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Len | TKL | Len+ bytes... | Code | TKL bytes ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options (if any) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1 1 1 1 1 1 1 1| Payload (if any) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 6: CoAP Header with prepended Shim Header (L3).

-- End L Alternatives

The Message ID is meaningless and thus elided. code for
NON (01)).

The semantics of the other CoAP header fields is are left unchanged.

4.1. Discussion

One might wish that, when CoAP is used over TLS, then the TLS record
layer length field could be used in place of the shim header length.
Each CoAP message would be transported in a separate TLS record layer
message, making the shim header that includes the length information
redundant.

However, RFC 5246 says that "Client message boundaries are not
preserved in the record layer (i.e., multiple client messages of the
same ContentType MAY be coalesced into a single TLSPlaintext record,
or a single message MAY be fragmented across several records)."
While the Record Layer provides length information about the
encapsulated application data and handshaking payloads, TLS
implementations typically do not support an API interface that would
provide access to the record layer delimiting information. An
additional problem with this approach is that this approach would
remove the potential optimization of packing several CoAP messages
into one record layer message, which is normally a way to amortize
the record layer and MAC overhead over all these messages.

In summary, we are not pursuing this idea for an optimization.

One other observation is that the message size limitations defined in
Section 4.6 of [RFC7252] are no longer strictly necessary.
Consenting [how?] implementations may want to interchange messages
with payload sizes larger than 1024 bytes, potentially also obviating
the need for the Block protocol [I-D.ietf-core-block]. It must be
noted that entirely getting rid of the block protocol is not a
generally applicable solution, as:

o a UDP-to-TCP gateway may simply not have the context to convert a
message with a Block option into the equivalent exchange without
any use of a Block option.

o large messages might also cause undesired head-of-line blocking.

The general assumption is therefore that the block protocol will
continue to be used over TCP, even if TCP-based applications
occasionally do exchange messages with payload sizes larger than
desirable in UDP.

5. Message Transmission

As CoAP exchanges messages asynchronously over the TCP connection,
the client can send multiple requests without waiting for responses.
For this reason, and due to the nature of TCP, responses are returned
during the same TCP connection as the request. In the event that the
connection gets terminated, all requests that have not yet elicited a
response yet are implicitly canceled; clients are free to may transmit the request
again once a connection is reestablished.

Furthermore, since TCP is bidirectional, requests can be sent from
both the connecting host or and the endpoint that accepted the
connection. In other words, who whoever initiated the TCP connection has
no bearing on the meaning of the CoAP terms client and server, which are
relating only to an individual request and response pair. server.

6. CoAP URI

CoAP [RFC7252] defines the "coap" and "coaps" URI schemes for
identifying CoAP resources and providing a means of locating the
resource. RFC 7252 defines these resources for use with CoAP over
UDP.

The present specification introduces two new URI schemes, namely
"coap+tcp" and "coaps+tcp". The rules from Section 6 of [RFC7252]
apply to these two new URI schemes.

[RFC7252], Section 8 (Multicast CoAP), does not apply to the URI
schemes defined in the present specification.

Resources made available via one of the "coap+tcp" or "coaps+tcp"
schemes have no shared identity with the other scheme or with the
"coap" or "coaps" scheme, even if their resource identifiers indicate
the same authority (the same host listening to the same port). The
schemes constitute distinct namespaces and, in combination with the
authority, are considered to be distinct origin servers.

6.1. coap+tcp URI scheme

coap-tcp-URI = "coap+tcp:" "//" host [ ":" port ] path-abempty
[ "?" query ]

The semantics defined in [RFC7252], Section 6.1, applies apply to this URI
scheme, with the following changes:

o The port subcomponent indicates the TCP port at which the CoAP
server is located. (If it is empty or not given, then the default
port 5683 is assumed, as with UDP.)

6.2. coaps+tcp URI scheme

coaps-tcp-URI = "coaps+tcp:" "//" host [ ":" port ] path-abempty
[ "?" query ]

The semantics defined in [RFC7252], Section 6.2, applies apply to this URI
scheme, with the following changes:

o The port subcomponent indicates the TCP port at which the TLS
server for the CoAP server is located. If it is empty or not
given, then the default port 443 is assumed (this is different
from the default port for "coaps", i.e., CoAP over DTLS over UDP).

o When CoAP is exchanged over TLS port 443 then the "TLS Application
Layer Protocol Negotiation Extension" [RFC7301] MUST be used to
allow demultiplexing at the server-side unless out-of-band
information ensures that the client only interacts with a server
that is able to demultiplex CoAP messages over port 443. This
would, for example, be true for many Internet of Things IoT deployments where clients
are pre-configured to only ever talk with specific servers. [[_1:
Shouldn't we simply always require ALPN? The protocol should not
be defined in such a way that it depends on some undefined pre-configuration pre-
configuration mechanism. --cabo]]

7. Security Considerations

This document defines how to convey CoAP over TCP and TLS. It does
not introduce new vulnerabilities beyond those described already in
the CoAP specification. CoAP [RFC7252] makes use of DTLS 1.2 and
this specification consequently uses TLS 1.2 [RFC5246]. CoAP MUST
NOT be used with older versions of TLS. Guidelines for use of cipher
suites and TLS extensions can be found in [I-D.ietf-dice-profile].

8. IANA Considerations

8.1. Service Name and Port Number Registration

IANA is requested to assign the port number 5683 and the service name
"coap+tcp", in accordance with [RFC6335].

Service Name.
coap+tcp

Transport Protocol.
tcp

Assignee.
IESG <iesg@ietf.org>

Contact.
IETF Chair <chair@ietf.org>

Description.

Constrained Application Protocol (CoAP)

Reference.
[RFCthis]

Port Number.
5683

Similarly, IANA is requested to assign the service name "coaps+tcp",
in accordance with [RFC6335]. However, no separate port number is
used for "coaps" over TCP; instead, the ALPN protocol ID defined in
Section 8.3 is used over port 443.

Service Name.
coaps+tcp

Transport Protocol.
tcp

Assignee.
IESG <iesg@ietf.org>

Contact.
IETF Chair <chair@ietf.org>

Description.
Constrained Application Protocol (CoAP)

Reference.
[RFC7301], [RFCthis]

Port Number.
443 (see also Section 8.3 of [RFCthis]})

8.2. URI Schemes

This document registers two new URI schemes, namely "coap+tcp" and
"coaps+tcp", for the use of CoAP over TCP and for CoAP over TLS over
TCP, respectively. The "coap+tcp" and "coaps+tcp" URI schemes can
thus be compared to the "http" and "https" URI schemes.

The syntax of the "coap" and "coaps" URI schemes is specified in
Section 6 of [RFC7252] and the present document re-uses their
semantics for "coap+tcp" and "coaps+tcp", respectively, with the
exception that TCP, or TLS over TCP is used as a transport protocol.

IANA is requested to add these new URI schemes to the registry
established with [RFC4395]. [RFC7595].

8.3. ALPN Protocol ID

This document requests a value from the "Application Layer Protocol
Negotiation (ALPN) Protocol IDs" created by [RFC7301]:

Protocol:
CoAP

Identification Sequence:
0x63 0x6f 0x61 0x70 ("coap")

Reference:
[RFCthis]

9. Acknowledgements

We would like to thank Stephen Berard, Geoffrey Cristallo, Olivier
Delaby, Michael Koster, Matthias Kovatsch, Szymon Sasin, Andrew
Summers, and Zach Shelby for their feedback.

10. References

10.1. Normative References

[I-D.ietf-dice-profile]
Tschofenig, H. and T. Fossati, "A TLS/DTLS Profile "TLS/DTLS Profiles for the
Internet of Things", draft-ietf-dice-profile-12 draft-ietf-dice-profile-17 (work in
progress), May October 2015.

[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC
793, DOI 10.17487/RFC0793, September 1981. 1981,
<http://www.rfc-editor.org/info/rfc793>.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997.

[RFC4395] Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
Registration Procedures for New URI Schemes", BCP 35, RFC
4395, February 2006. 1997,
<http://www.rfc-editor.org/info/rfc2119>.

[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/
RFC5246, August 2008. 2008,
<http://www.rfc-editor.org/info/rfc5246>.

[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252, DOI 10.17487/
RFC7252, June 2014. 2014,
<http://www.rfc-editor.org/info/rfc7252>.

[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014. 2014, <http://www.rfc-editor.org/info/rfc7301>.

[RFC7595] Thaler, D., Ed., Hansen, T., and T. Hardie, "Guidelines
and Registration Procedures for URI Schemes", BCP 35, RFC
7595, DOI 10.17487/RFC7595, June 2015,
<http://www.rfc-editor.org/info/rfc7595>.

10.2. Informative References

[HomeGateway]
Eggert, L., "An experimental study of home gateway
characteristics", Proceedings of the 10th annual
conference on Internet measurement, 2010.

[I-D.bormann-core-cocoa]
Bormann, C., Betzler, A., Gomez, C., and I. Demirkol,
"CoAP Simple Congestion Control/Advanced", draft-bormann-
core-cocoa-02
core-cocoa-03 (work in progress), July 2014. October 2015.

[I-D.ietf-core-block]
Bormann, C. and Z. Shelby, "Block-wise transfers in CoAP",
draft-ietf-core-block-17
draft-ietf-core-block-18 (work in progress), March September
2015.

[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, DOI
10.17487/RFC0768, August 1980. 1980,
<http://www.rfc-editor.org/info/rfc768>.

[RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165, RFC
6335, DOI 10.17487/RFC6335, August 2011. 2011,
<http://www.rfc-editor.org/info/rfc6335>.

[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012.

[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", RFC 7049, October 2013. 2012, <http://www.rfc-editor.org/info/rfc6347>.

Authors' Addresses
Carsten Bormann (editor)
Universitaet Bremen TZI
Postfach 330440
Bremen D-28359
Germany

Phone: +49-421-218-63921
Email: cabo@tzi.org

Simon Lemay
Zebra Technologies
820 W. Jackson Blvd.suite Blvd. Suite 700
Chicago 60607
United States of America

Phone: +1-847-634-6700
Email: slemay@zebra.com

Valik Solorzano Barboza
Zebra Technologies
820 W. Jackson Blvd. suite 700
Chicago 60607
United States of America

Phone: +1-847-634-6700
Email: vsolorzanobarboza@zebra.com

Hannes Tschofenig
ARM Ltd.
110 Fulbourn Rd
Cambridge CB1 9NJ
Great Britain

Email: Hannes.tschofenig@gmx.net
URI: http://www.tschofenig.priv.at