Added introduction, architecture section
Updated license header on new files.
Change-Id: Ic44db303ab935099698f8c6547904802381fce5c
diff --git a/overview/architecture.rst b/overview/architecture.rst
index 450b00c..3182ce5 100644
--- a/overview/architecture.rst
+++ b/overview/architecture.rst
@@ -1,9 +1,55 @@
-Architecture
+..
+ SPDX-FileCopyrightText: © 2020 Open Networking Foundation <support@opennetworking.org>
+ SPDX-License-Identifier: Apache-2.0
+
+SD-Core Architecture
====================
+ * SD-Core is a flexible, agile, scalable and configurable dual-mode 4G/5G core
+ network platform that builds upon and enhances ONF’s OMEC and free 5GC core
+ network platforms to support LTE, 5G NSA and 5G SA services.
+
+ * The SD-Core control plane provides the flexibility of simultaneous supports
+ for 5G standalone, 5G non-standalone and 4G/LTE deployments.
+
+ * SD-Core provides a rich set of APIs to Runtime Operation Control (ROC).
+
+ * Operators can use these APIs to provision the subscribers in the mobile core;
+ * Control runtime configuration of network functions
+ * Provide telemetry data to third party applications
+ * Third party applications can leverage telemetry data to create applications
+ for closed loop control.
+
+.. image:: ../_static/images/SD-Core-Architecture.png
+ :width: 700px
+
+Multiple Distributed User Planes
+--------------------------------
+
+SD-Core has three User Plane Functions (UPFs) designed to be deployed throughout
+the network edge. Each UPF is optimized to handle specific classes of application
+and take advantage of various hardware acceleration options. Deployments can
+intermix the UPF variants.
+
+ * P4-Based UPF optimized for private enterprise deployments, and providing fine-grained
+ visibility for verifiable performance and secure operations
+ * Containerized Dual-Core UPF optimized for private enterprise deployments, capable of
+ processing LTE and 5G traffic simultaneously
+ * Containerized Dual-Core UPF optimized for various MNO use cases, capable of processing
+ LTE and 5G traffic simultaneously
+
+
+SD-Core architecture is modular and apis are provided to manage connectivity service.
+
+ - Connectivity service is designed in such a way that it can be consumed easily and its
+ easy to configure. Please refer ``configuration section``. Configuration APIs are same
+ for 4G & 5G service.
+ - Metrics are exposed from SD-Core which helps network admins and application developers.
+ - Application filtering is supported to restrict the access to applications.
+
Architecture Diagram showing SD-Core box
----------------------------------------
-- Diagram should show ROC interface, Prom interface, UPF interface, gNB/eNB interface
+- Diagram should show ROC interface, prometheus interface, UPF interface, gNB/eNB interface
Architecture Diagram of SD-Core 4G block
----------------------------------------