doc: Updating TLS md (#672)

tls_protocol_version_and_ciphers.md

@@ -1,9 +1,21 @@
-# IoT Node SDK support for TLS 1.2
+# IoT Node SDK TLS
 
-## TLS Version
+When using the Azure IoT Node SDK in your application, you may wish to control which version of TLS is used and which ciphers are used by TLS.
 
-The Node SDK fully supports TLS 1.2 in all of its APIs.
+## How to restrict TLS version
+
+To restrict the TLS version one will need to set the NODE_OPTIONS environment variable to use the min version of the desired tls value
+
+```
+NODE_OPTIONS='--tls-min-v1.2'
+```
 
 ## TLS Cipher Suites
 
-Coming Soon
+Additionally if you would like to specify a list of ciphers can be restricted by adding a NODE_OPTIONS environment variable
+
+```
+NODE_OPTIONS='--tls-cipher-list=[cipher1]'
+```
+
+for more information see [Modifying the Default TLS Cipher suite](https://nodejs.org/api/tls.html#tls_modifying_the_default_tls_cipher_suite)