Update Configuration reference

Signed-off-by: Yevhen Fastiuk <[email protected]>

Author: fastiuk

src/sonic-yang-models/doc/Configuration.md

@@ -1474,6 +1474,35 @@ These configuration options are used to modify the way that
 ntp binds to the ports on the switch and which port it uses to
 make ntp update requests from.
 
+***NTP Admin state***
+
+If this option is set to `enabled` then ntp client will try to sync system time with configured NTP servers.
+Otherwise, NTP client feature will be disabled.
+```
+{
+    "NTP": {
+        "global": {
+            "admin_state": "enabled"
+        }
+    }
+}
+```
+
+***NTP Server role***
+
+This option is used to control NTP server state on the switch.
+If this option is set to `enabled` switch will act as NTP server.
+By default `server_role` is `disabled`.
+```
+{
+    "NTP": {
+        "global": {
+            "server_role": "enabled"
+        }
+    }
+}
+```
+
 ***NTP VRF***
 
 If this option is set to `default` then ntp will run within the default vrf
@@ -1511,6 +1540,36 @@ for that address.
 }
 ```
 
+***NTP Authentication***
+
+If this option is set to `enabled` then ntp will try to verify NTP servers it connects to.
+This option **has no effect** if key is not set for NTP server.
+By default it is `disabled`
+```
+{
+    "NTP": {
+        "global": {
+            "authentication": "enabled"
+        }
+    }
+}
+```
+
+***NTP DHCP leases***
+
+If this option is set to `enabled` then ntp client will try to use NTP servers provided by DHCP server.
+If this option is set to `disabled` you will be able to use the user-configured NTP servers.
+By default it is `enabled`
+```
+{
+    "NTP": {
+        "global": {
+            "dhcp": "enabled"
+        }
+    }
+}
+```
+
 ### NTP and SYSLOG servers
 
 These information are configured in individual tables. Domain name or IP
@@ -1521,18 +1580,77 @@ attributes in those objects.
 ```
 {
     "NTP_SERVER": {
-        "2.debian.pool.ntp.org": {},
-        "1.debian.pool.ntp.org": {},
-        "3.debian.pool.ntp.org": {},
-        "0.debian.pool.ntp.org": {}
+        "2.debian.pool.ntp.org": {
+            "association_type": "pool",
+            "iburst": "on",
+            "admin_state": "enabled",
+            "version": 4
+        },
+        "1.debian.pool.ntp.org": {
+            "association_type": "pool",
+            "iburst": "off",
+            "admin_state": "enabled",
+            "version": 3
+        },
+        "3.debian.pool.ntp.org": {
+            "association_type": "pool",
+            "iburst": "on",
+            "admin_state": "disabled",
+            "version": 4
+        },
+        "0.debian.pool.ntp.org": {
+            "association_type": "pool",
+            "iburst": "off",
+            "admin_state": "disabled",
+            "version": 3
+        }
     },
 
     "NTP_SERVER": {
-        "23.92.29.245": {},
-        "204.2.134.164": {}
+        "23.92.29.245": {
+            "association_type": "server",
+            "iburst": "on",
+            "admin_state": "enabled",
+            "version": 4,
+            "key": 3,
+            "trusted": "yes"
+        },
+        "204.2.134.164": {
+            "association_type": "server",
+            "iburst": "on",
+            "admin_state": "enabled",
+            "version": 3
+        }
+    }
+}
+```
+* `association_type` - is used to control the type of the server. It can be `server` or `pool`.
+* `iburst` - agressive server polling `{on, off}`.
+* `version` - NTP protool version to use `[3..4]`.
+* `key` - authentication key id `[1..65535]` to use to auth the server.
+* `admin_state` - enable or disable specific server.
+* `trusted` - trust this server when auth is enabled.
+
+***NTP keys***
+```
+{
+    "NTP_KEY": {
+        "1": {
+            "type": "md5",
+            "value": "bXlwYXNzd29yZA==",
+            "trusted": "yes"
+        },
+        "42": {
+            "type": "sha1",
+            "value": "dGhlYW5zd2Vy",
+            "trusted": "no"
+        }
     }
 }
 ```
+* `type` - key type to use `{md5, sha1, sha256, sha384, sha512}`.
+* `value` - base64 encoded key value.
+* `trusted` - trust this NTP key `{yes, no}`.
 
 ***Syslog server***
 ```