Clarify that client.port is the port of whichever client was captured in client.address

CHANGELOG.md

@@ -36,6 +36,8 @@ release.
   ([#449](https://github.com/open-telemetry/semantic-conventions/pull/449))
 - Change `user_agent.original` from recommended to opt-in on HTTP client spans.
   ([#468](https://github.com/open-telemetry/semantic-conventions/pull/468))
+- Clarify that `client.port` is the port of whichever client was captured in `client.address`.
+  ([#471](https://github.com/open-telemetry/semantic-conventions/pull/471))
 
 ### Features
 

docs/http/http-spans.md

@@ -343,7 +343,7 @@ For an HTTP server span, `SpanKind` MUST be `Server`.
 | Attribute  | Type | Description  | Examples  | Requirement Level |
 |---|---|---|---|---|
 | [`client.address`](../general/attributes.md) | string | Client address - domain name if available without reverse DNS lookup; otherwise, IP address or Unix domain socket name. [1] | `83.164.160.102` | Recommended |
-| [`client.port`](../general/attributes.md) | int | The port of the original client behind all proxies, if known (e.g. from [Forwarded#for](https://developer.mozilla.org/docs/Web/HTTP/Headers/Forwarded#for) or a similar header). Otherwise, the immediate client peer port. [2] | `65123` | Recommended |
+| [`client.port`](../general/attributes.md) | int | The port of whichever client was captured in `client.address`. [2] | `65123` | Recommended |
 | [`http.route`](../attributes-registry/http.md) | string | The matched route, that is, the path template in the format used by the respective server framework. [3] | `/users/:userID?`; `{controller}/{action}/{id?}` | Conditionally Required: If and only if it's available |
 | [`network.local.address`](../attributes-registry/network.md) | string | Local socket address. Useful in case of a multi-IP host. | `10.1.2.80`; `/tmp/my.sock` | Opt-In |
 | [`network.local.port`](../attributes-registry/network.md) | int | Local socket port. Useful in case of a multi-port host. | `65123` | Opt-In |

model/trace/http.yaml

@@ -73,10 +73,7 @@ groups:
             Otherwise, the immediate client peer address.
         examples: ['83.164.160.102']
       - ref: client.port
-        brief: >
-            The port of the original client behind all proxies, if
-            known (e.g. from [Forwarded#for](https://developer.mozilla.org/docs/Web/HTTP/Headers/Forwarded#for) or a similar header).
-            Otherwise, the immediate client peer port.
+        brief: The port of whichever client was captured in `client.address`.
       - ref: url.path
         requirement_level: required
         sampling_relevant: true