UTA B. Yang
Internet-Draft China Mobile
Intended status: Informational October 19, 2018
Expires: April 22, 2019

Requirements for DTLS 1.3 in Constrained IoT Devices
draft-yang-uta-dtls13-for-iot-00

Abstract

The purpose of this document is to summarize several typical terminals and service types in using DTLS 1.3 for constrained IoT devices, especially those of cellular networks, analyses the existing problems on TLS/DTLS solution on constrained devices and provides some suggestions are given.

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Table of Contents

1. Introduction

There are many kinds of IoT devices, thus many classification methods accrodingly. From the communication throughput aspect, IoT devices can be divided into low-speed, high-speed devices. From the geographical location aspects, they can be divided into: mobile devices, fixed devices. From the processing capacity, they can be divided into simple mobile devices, smart mobile devices.

IoT Services can be divided into personal application, family application, vertical industry application according to different usage situations.

Different types of devices and services have different communication and service characteristics, but in general, saving resources and communication security are common requirements.

[RFC 7925] introduced the IoT profiles in using TLS/DTLS 1.2. [RFC 8446] introduced a new and clean TLS 1.3. [draft-tschofenig-uta-tls13-profile-01] offered communication security services for IoT applications and is reasonably implementable on many constrained devices.

This document summarizes several terminal and service types in using DTLS 1.3 for constrained IoT devices, especially those of cellular networks, analyses the existing problems on TLS/DTLS solution on constrained devices and provides some suggestions are given.

2. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

3. IoT Services Scenarios and Devices

In different scenarios, IoT services show different characteristics, and their device and security requirements are considerably different. This section lists several typical IoT usage scenarios to analyze its device features and security requirements.

As can be seen from the above four scenarios, it is of great value for any Internet of Things application to save the cost of security functions from the device apect.

4. Suggestions and Considerations

For the application of DTLS 1.3 profile on IoT, protocol level optimization focused on features of device capacity and the network connection, the communication processing overhead of DTLS 1.3 can be reduced, the life cycle of the devices can be prolonged, the cost of device manufacturing and maintenance can be reduced, and the service experience can be improved. This section provides the following suggestions and considerations for DTLS 1.3 IoT implementation.

4.1. Shorten Message Size of Handshaking

In TLS 1.3, the size of handshaking message can be very large. If TCP is used, it will not have a significant impact, but when transmission of large messages on the UDP, it means fragmentation, loss, retransmission, disordering and waiting, which shall contribute to the long latency for DTLS handshake process. This effect is more significant when the device communication traffic rate is low and the network coverage is poor. Simplifying handshaking message size shall reduce the probability of fragmentation and fragmentation. The observations may include:

4.2. Problems Introduced by NAT

Because of the large number of IoT devices, NAT is used in most IoT networks. The problems introduced by NAT include:

4.3. Long-time Dormancy Devices

Long-time dormant devices such as Watt-hour meter and water meters, because of the huge number devices with each have low communication frequency, greatly increase the burden in storing PSK in network side and device side. The storage of PSK also increases the risk of PSK leakage. If DTLS 1.3 session initiation process is used each time, a large number of interactions will occur, and the net service traffic is much less than the TLS protocol overhead. We need to consider improving the DTLS mechanism for such devices.

5. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC7925] Tschofenig, H. and T. Fossati, "Transport Layer Security (TLS) / Datagram Transport Layer Security (DTLS) Profiles for the Internet of Things", RFC 7925, DOI 10.17487/RFC7925, July 2016.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018.

Author's Address

Yang Boyle China Mobile China EMail: boyxd@hotmail.com