Create EN-US version of policy.md

Author: oweid

docs/en_US/config/policy.md

@@ -1,3 +1,129 @@
 # Policy
 
-The documentation for this page is missing. Please submit a [pull request](https://github.com/v2fly/v2fly-github-io/pulls) or refer to the Chinese documentation.
+Local policies can configure user-related permissions, such as connection timeout settings. Every connection handled by V2Ray corresponds to a user, and different policies are applied according to the user's level. Local policies can vary based on different levels.
+
+## PolicyObject
+
+`PolicyObject` corresponds to the `policy` entry in the configuration file.
+
+```json
+{
+    "levels": {
+        "0": {
+            "handshake": 4,
+            "connIdle": 300,
+            "uplinkOnly": 2,
+            "downlinkOnly": 5,
+            "statsUserUplink": false,
+            "statsUserDownlink": false,
+            "bufferSize": 10240
+        }
+    },
+    "system": {
+        "statsInboundUplink": false,
+        "statsInboundDownlink": false,
+        "statsOutboundUplink": false,
+        "statsOutboundDownlink": false
+    }
+}
+```
+
+> `level`: map{string: [LevelPolicyObject](#levelpolicyobject)}
+
+A key-value pair where each key is a number in string format (JSON requirement), such as `"0"`, `"1"`, etc. The quotation marks cannot be omitted. This number corresponds to the user level. Each value is a [LevelPolicyObject](#levelpolicyobject).
+
+:::tip
+Each inbound and outbound proxy can now set user levels, and V2Ray will apply different local policies based on the actual user level.
+:::
+
+> `system`: [SystemPolicyObject](#systempolicyobject)
+
+System policies for V2Ray
+
+## LevelPolicyObject
+
+```json
+{
+    "handshake": 4,
+    "connIdle": 300,
+    "uplinkOnly": 2,
+    "downlinkOnly": 5,
+    "statsUserUplink": false,
+    "statsUserDownlink": false,
+    "bufferSize": 10240
+}
+```
+
+> `handshake`: number
+
+Time limit for connection handshake. Unit is seconds. Default value is `4`. When an inbound proxy processes a new connection during the handshake phase (e.g., VMess reading header data, determining target server address), if the time used exceeds this limit, the connection will be terminated.
+
+> `connIdle`: number
+
+Connection idle time limit. Unit is seconds. Default value is `300`. When processing a connection in inbound/outbound proxies, if no data (including uplink and downlink) is transmitted within `connIdle` time, the connection will be terminated.
+
+> `uplinkOnly`: number
+
+Time limit after downlink connection closure. Unit is seconds. Default value is `2`. When the server (e.g., remote website) closes the downlink connection, the outbound proxy will terminate the connection after waiting for `uplinkOnly` seconds.
+
+> `downlinkOnly`: number
+
+Time limit after uplink connection closure. Unit is seconds. Default value is `5`. When the client (e.g., browser) closes the uplink connection, the inbound proxy will terminate the connection after waiting for `downlinkOnly` seconds.
+
+:::tip
+In HTTP browsing scenarios, you can set both `uplinkOnly` and `downlinkOnly` to `0` to improve connection closure efficiency.
+:::
+
+> `statsUserUplink`: true | false
+
+When set to `true`, enables uplink traffic statistics for all users at the current level.
+
+> `statsUserDownlink`: true | false
+
+When set to `true`, enables downlink traffic statistics for all users at the current level.
+
+> `bufferSize`: number
+
+Internal buffer size for each connection. Unit is kB. When set to `0`, internal buffer is disabled.
+
+Default values (V2Ray 4.4+):
+
+* On ARM, MIPS, MIPSLE platforms: default is `0`
+* On ARM64, MIPS64, MIPS64LE platforms: default is `4`
+* On other platforms: default is `512`
+
+Default values (V2Ray 4.3-):
+
+* On ARM, MIPS, MIPSLE, ARM64, MIPS64, MIPS64LE platforms: default is `16`
+* On other platforms: default is `2048`
+
+:::tip
+The `bufferSize` option overrides the `v2ray.ray.buffer.size` setting in [environment variables](env.md#buffer-size-per-connection).
+:::
+
+## SystemPolicyObject
+
+```json
+{
+    "statsInboundUplink": false,
+    "statsInboundDownlink": false,
+    "statsOutboundUplink": false,
+    "statsOutboundDownlink": false
+}
+```
+
+> `statsInboundUplink`: true | false
+
+When set to `true`, enables uplink traffic statistics for all inbound proxies.
+
+> `statsInboundDownlink`: true | false
+
+When set to `true`, enables downlink traffic statistics for all inbound proxies.
+
+> `statsOutboundUplink`: true | false
+
+(V2Ray 4.26.0+) When set to `true`, enables uplink traffic statistics for all outbound proxies.
+
+> `statsOutboundDownlink`: true | false
+
+(V2Ray 4.26.0+) When set to `true`, enables downlink traffic statistics for all outbound proxies.