Readme edits per MPSG

README.md

@@ -6,13 +6,112 @@
 
 # What is Project Connected Home over IP?
 
-Visit [connectedhomeip.com](https://connectedhomeip.com) to learn more.
-
-# Current Status of Project Connected Home over IP
+Project Connected Home over IP is a new Working Group within the Zigbee
+Alliance. This Working Group plans to develop and promote the adoption of a new,
+royalty-free connectivity standard to increase compatibility among smart home
+products, with security as a fundamental design tenet.
+
+The goal of the Connected Home over IP project is to simplify development for
+manufacturers and increase compatibility for consumers. The project is built
+around a shared belief that smart home devices should be secure, reliable, and
+seamless to use. By building upon Internet Protocol (IP), the project aims to
+enable communication across smart home devices, mobile apps, and cloud services
+and to define a specific set of IP-based networking technologies for device
+certification.
 
 The Zigbee Alliance officially opened the Project Connected Home over IP
-(Project CHIP) Working Group on January 17 and is in the process of drafting the
-specification.
+(Project CHIP) Working Group on January 17, 2020 and is in the process of
+drafting the specification.
+
+Visit [connectedhomeip.com](https://connectedhomeip.com) to learn more and read
+the latest news and updates about the project.
+
+# Project Overview
+
+## Development Goals
+
+Project Connected Home over IP is developed with the following goals and
+principles in mind:
+
+**Unifying:** Project CHIP will produce a new specification, building with and
+on top of market-tested, existing technologies.
+
+**Interoperable:** The specification permits communication between any Project
+CHIP-certified device, subject to users’ permission.
+
+**Secure:** The specification leverages modern security practices and protocols.
+
+**User Control:** The end user is in control of authorization for interaction
+with devices.
+
+**Federated:** No single entity serves as a throttle or a
+single-point-of-failure for root of trust.
+
+**Robust:** The set of protocols specify a complete lifecycle of a device —
+starting with the seamless out-of-box experience, through operational protocols,
+to device and system management specifications required for proper function in
+the presence of change.
+
+**Low Overhead:** The protocols are practically implementable on low
+compute-resource devices, such as MCUs.
+
+**Pervasive:** The protocols are broadly deployable and accessible, thanks to
+leveraging IP and being implementable on low-capability devices.
+
+**Ecosystem-Flexible:** The protocol must be flexible enough to accommodate
+deployment in ecosystems with differing policies.
+
+**Easy to Use:** The protocol should aim to provide smooth, cohesive, integrated
+provisioning and out-of-box experience.
+
+**Open:** The Project’s design and technical processes should be open and
+transparent to the general public, including to non-members wherever possible.
+
+## Architecture Overview
+
+![CHIP Architecture Overview](docs/images/CHIP_IP_pyramid.png)
+
+The Project, as illustrated above, defines the application layer that will be
+deployed on devices and controllers as well as the supported IPv6-based networks
+to help achieve our interoperability architectural goal. Project CHIP will
+initially support Wi-Fi and Thread for core, operational communications and
+Bluetooth Low Energy (BLE) to simplify device commissioning and setup.
+
+The Application Layer can be further broken down seven main components:
+
+![CHIP Stack Architecture](docs/images/CHIP_Arch_Pyramid.png)
+
+1. **Application:** High order business logic of a device. For example, an
+   application that is focused on lighting might contain logic to handle turning
+   on/off the bulb as well its color characteristics.
+
+2. **Data Model:** Data primitives that help describe the various
+   functionalities of the devices. The Application operates on these data
+   structures when there is intent to interact with the device.
+
+3. **Interaction Model:** Represents a set of actions that can be performed on
+   the devices to interact with it. For example, reading or writing attributes
+   on a device would correspond to interactions with the devices. These actions
+   operate on the structures defined by the data model.
+
+4. **Action Framing:** Once an action is constructed using the Interaction
+   Model, it is framed into a prescriptive packed binary format to enable being
+   well represented on the “wire”.
+
+5. **Security:** An encoded action frame is then sent down to the Security Layer
+   to encrypt and sign the payload to ensure that data is secured and
+   authenticated by both sender and receiver of a packet.
+
+6. **Message Framing & Routing:** With an interaction encrypted and signed, the
+   Message Layer constructs the payload format with required and optional header
+   fields; which specify properties of the message as well some routing
+   information.
+
+7. **IP Framing & Transport Management:** After the final payload has been
+   constructed, it is sent to the underlying transport protocol for IP
+   management of the data.
+
+# Current Status of Project Connected Home over IP
 
 The Project’s design and technical processes are intended to be open and
 transparent to the general public, including to Work Group non-members wherever
@@ -27,9 +126,17 @@ Project to consumers and manufacturers as quickly as possible. As a result, what
 you observe in this repository is an implementation-first approach to the
 technical specification, vetting integrations in practice.
 
+The Project repository is growing and evolving to implement the overall
+architecture. The repository currently contains the security foundations,
+message framing and dispatch, an implementation of the interaction model and
+data model. The code examples show simple interactions, and are supported on
+multiple transports -- Wi-Fi and Thread -- starting with resource-constrained
+(i.e., memory, processing) silicon platforms to help ensure the Project’s
+scalability.
+
 # How to Contribute
 
-We would love for you to contribute to Project Connected Home over IP. Read our
+We welcome your contributions to Project Connected Home over IP. Read our
 contribution guidelines
 [here](https://github.com/project-chip/connectedhomeip/blob/master/CONTRIBUTING.md).