Embellished Jans Lock intro page. (#6844)

Signed-off-by: Mustafa Baser <mbaser@mail.com>

docs/admin/lock/README.md

@@ -11,10 +11,48 @@ tags:
 
 # Jans Lock Overview
 
-Lock enables domains to enforce policies based on real time OAuth data. Lock
-pushes token data from Auth Server to [OPA](https://openpolicyagent.org), enabling
-authorization based on real time information from the OAuth infrastructure. In
-order to use Lock, admins will have to do a few things:
+Jans Lock enables domains to enforce access policies based on real time OAuth
+data.
+
+Centralized policy management is a best practice for authorization for distributed
+networks. If security policies are buried in the code of numerous applications,
+they are hard to inventory and harder to update. For decades, application
+security architects have conceptualized distributed authorization in line with
+[RFC 2409](https://datatracker.ietf.org/doc/html/rfc2904#section-4.4)
+and [XACML](https://docs.oasis-open.org/xacml/3.0/xacml-3.0-core-spec-cos01-en.html),
+which describe several common components:
+
+|Abbr.	| Term | Description |
+| ----- | :--: | ----------- |
+| PDP	| Policy Decision Point	|  Service which evaluates access requests against authorization policies before issuing access decisions |
+| PEP	| Policy Enforcement Point | Service, website or API which queries the PDP for authorization |
+| PAP	| Policy Administration Point	|  User interface where admins manage authorization policies |
+| PIP	| Policy Information Point | The "data" about people, clients and resources |
+| PRP	| Policy Retrieval Point | Repository where policies are stored |
+
+In the old days of "WAM" (web access management), each web server would query
+a centralized PDP over the network. This is ok for course grain authorization.
+But for fine grain authorization, it is too slow--each decision requires a round
+trip HTTP request/response. A more performant design is to move the PDP to the
+edge of the network. Policy definition and administration is still a centralized
+activity. Once a policy is defined, it can be executed anywhere on the network.
+Although multiple PDP instances exist, they must provide the same access control
+decisions given the same inputs.
+
+Another critical optimization was to move the PIP to the edge, so the PDP
+has all the data it needs to make a decision. This aligns with a principle that
+each microservice is well-encapsulated--all logic and data is encapsulated into
+a single deployment unit.
+
+![Jans Lock Toplogy](../../assets/lock-design-diagram-02.png)
+
+To empower this cloud native authorization pattern, Janssen leverages a
+component governed under the Linux Foundation: [OPA](https://openpolicyagent.org),
+a project at the [CNCF](https://cncf.io). OPA is a popular PDP, whose popularity
+grew significantly in response to the need for granular policies for Kubernetes
+access control. The Jans Lock solution pushes token data from Auth Server to OPA,
+enabling authorization based on real time information from the OAuth
+infrastructure. In order to use Lock, admins will have to do a few things:
 
   * [Enable Lock in Auth Server](./lock_token_stream.md)
   * [Configure a Lock client instance](./lock_client.md)