Update concepts-networking.md

Author: GennadNY

articles/postgresql/flexible-server/concepts-networking.md

@@ -200,14 +200,21 @@ An example that uses an FQDN as a host name is `hostname = servername.postgres.d
 
 Azure Database for PostgreSQL - Flexible Server enforces connecting your client applications to the PostgreSQL service by using Transport Layer Security (TLS). TLS is an industry-standard protocol that ensures encrypted network connections between your database server and client applications. TLS is an updated protocol of Secure Sockets Layer (SSL). 
 
-Azure Database for PostgreSQL supports TLS 1.2 and later. In [RFC 8996](https://datatracker.ietf.org/doc/rfc8996/), the Internet Engineering Task Force (IETF) explicitly states that TLS 1.0 and TLS 1.1 must not be used. Both protocols were deprecated by the end of 2019.
+There are several government entities worldwide that maintain guidelines for TLS with regard to network security, including Department of Health and Human Services (HHS) or the National Institute of Standards and Technology (NIST) in the United States. The level of security that TLS provides is most affected by the TLS protocol version and the supported cipher suites. A cipher suite is a set of algorithms, including a cipher, a key-exchange algorithm and a hashing algorithm, which are used together to establish a secure TLS connection. Most TLS clients and servers support multiple alternatives, so they have to negotiate when establishing a secure connection to select a common TLS version and cipher suite.
+
+Azure Database for PostgreSQL supports TLS version 1.2 and later. In [RFC 8996](https://datatracker.ietf.org/doc/rfc8996/), the Internet Engineering Task Force (IETF) explicitly states that TLS 1.0 and TLS 1.1 must not be used. Both protocols were deprecated by the end of 2019.
 
 All incoming connections that use earlier versions of the TLS protocol, such as TLS 1.0 and TLS 1.1, will be denied by default. 
 
 > [!NOTE]
 > SSL and TLS certificates certify that your connection is secured with state-of-the-art encryption protocols. By encrypting your  connection on the wire, you prevent unauthorized access to your data while in transit. This is why we strongly recommend using latest versions of TLS to encrypt your connections to Azure Database for PostgreSQL - Flexible Server. 
 > Although its not recommended, if needed, you have an option to disable TLS\SSL for connections to Azure Database for PostgreSQL - Flexible Server by updating  the **require_secure_transport** server parameter to OFF. You can also set TLS version by setting **ssl_min_protocol_version** and **ssl_max_protocol_version** server parameters.
 
+[Certificate authentication](https://www.postgresql.org/docs/current/auth-cert.html) is performed using **SSL client certificates** for authentication. In this scenario, PostgreSQL server compares the CN (common name) attribute of the client certificate presented, against the requested database user.
+**Azure Database for PostgreSQL - Flexible Server does not support SSL certificate based authentication at this time.**
+
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 ## Next steps
 
 * Learn how to create a flexible server by using the **Private access (VNet integration)** option in [the Azure portal](how-to-manage-virtual-network-portal.md) or [the Azure CLI](how-to-manage-virtual-network-cli.md).