Communications technology is being embedded into our environment. Different types of devices in our buildings, vehicles, equipment and other objects have a need to communicate. It is expected that most of these devices will employ the Internet Protocol suite. However, there is a lot of variation in the capabilities between different types of devices, and it is not always easy to embed all the necessary features. The Light-Weight Implementation Guidance (LWIG) Working Group focuses on helping the implementors of the smallest devices. The goal is to be able to build minimal yet interoperable IP-capable devices for the most constrained environments.
Building a small implementation does not have to be hard. Many small devices use stripped down versions of general purpose operating systems and their TCP/IP stacks. However, there are implementations that go even further in minimization and can exist in as few as a couple of kilobytes of code, as on some devices this level of optimization is necessary. Technical and cost considerations may limit the computing power, battery capacity, available memory, or communications bandwidth that can be provided. To overcome these limitations the implementors have to employ the right hardware and software mechanisms. For instance, certain types of memory management or even fixed memory allocation may be required. It is also useful to understand what is necessary from the point of view of the communications protocols and the application employing them. For instance, a device that only acts as a client or only requires one connection can simplify its TCP implementation.
The purpose of the LWIG working group is to collect experiences from implementors of IP stacks in constrained devices. The group shall focus only on techniques that have been used in actual implementations and do not impact interoperability with other devices. The techniques shall also not affect conformance to the relevant specifications. The output of this work is a document that describes implementation techniques for reducing complexity, memory footprint, or power usage. The topics for this working group will be chosen from these protocols: IPv4, IPv6, UDP, TCP, ICMPv4/v6, MLD/IGMP, ND, DNS, DHCPv4/v6, IPsec, 6LOWPAN, COAP, RPL, SNMP and NETCONF protocols. This document will be helpful for the implementors of new devices or for the implementors of new general-purpose small IP stacks. It is also expected that the document increases our knowledge of what existing small implementations do, and helps in the further optimization of the existing implementations. On areas where the considerations for small implementations have already been documented the group shall make an effort to refer to those documents instead of developing its own.
Generic hardware design advice and software implementation techniques are outside the scope of this work, as such expertise is not within the IETF domain. Protocol implementation experience, however, is within the IETF domain. The group shall also not develop any new protocols or protocol behavior modifications beyond what is already allowed by existing RFCs, because it is important to ensure that different types of devices can work together. The group shall not develop assumptions or profiles about the operating environment of the devices, because, in general, it is not possible to guarantee any special configuration. Finally, while implementation techniques relating to security mechanisms are within scope, mere removal of security functionality from a protocol is not an acceptable recommendation.
Given that the group works on both IP and transport layer protocols it is necessary to ensure that expertise in both aspects is present in the group. Participation from the implementors of existing small IP stacks is also required.
Submit the Terminology for Constrained-Node Networks document to the IESG for publication as Informational RFC