Clarify OTLP/HTTP port handling. (#1985)

Clarifies that default ports for the URL schemes, not default OTLP/HTTP port should be used if no port is given in URL.

See open-telemetry/opentelemetry-specification#1975 (comment)

CHANGELOG.md

@@ -34,6 +34,9 @@ release.
 
 ### OpenTelemetry Protocol
 
+- Specify the behavior of the OTLP endpoint variables for OTLP/HTTP more strictly
+  ([#1975](https://github.com/open-telemetry/opentelemetry-specification/pull/1975),
+  [#1985](https://github.com/open-telemetry/opentelemetry-specification/pull/1985))
 - Make OTLP/HTTP the recommended default transport ([#1969](https://github.com/open-telemetry/opentelemetry-specification/pull/1969))
 
 ### SDK Configuration
@@ -105,8 +108,6 @@ release.
 ### OpenTelemetry Protocol
 
 - Add environment variables for configuring the OTLP exporter protocol (`grpc`, `http/protobuf`, `http/json`) ([#1880](https://github.com/open-telemetry/opentelemetry-specification/pull/1880))
-- Specify the behavior of the OTLP endpoint variables for OTLP/HTTP more strictly
-  ([#1975](https://github.com/open-telemetry/opentelemetry-specification/pull/1975)).
 - Allow implementations to use their own default for OTLP compression, with `none` denotating no compression
   ([#1923](https://github.com/open-telemetry/opentelemetry-specification/pull/1923))
 - Clarify OTLP server components MUST support none/gzip compression

specification/protocol/exporter.md

@@ -51,6 +51,11 @@ for each signal as follow:
    Non-normatively, this could be implemented by ensuring that the base URL ends with
    a slash and then appending the relative URLs as strings.
 
+An SDK MUST NOT modify the URL in ways other than specified above. That also means,
+if the port is empty or not given, TCP port 80 is the default for the `http` scheme
+and TCP port 443 is the default for the `https` scheme, as per the usual rules
+for these schemes ([RFC 7230](https://datatracker.ietf.org/doc/html/rfc7230#section-2.7.1)).
+
 #### Example 1
 
 The following configuration sends all signals to the same collector:
@@ -74,7 +79,7 @@ export OTEL_EXPORTER_OTLP_METRICS_ENDPOINT=https://collector.example.com/v1/metr
 This will send traces directly to the root path `http://collector:4318/`
 (`/v1/traces` is only automatically added when using the non-signal-specific
 environment variable) and metrics
-to `https://collector.example.com/v1/metrics`.
+to `https://collector.example.com/v1/metrics`, using the default https port (443).
 
 #### Example 3
 
@@ -86,9 +91,10 @@ export OTEL_EXPORTER_OTLP_METRICS_ENDPOINT=https://collector.example.com/v1/metr
 ```
 
 Traces are sent to `http://collector:4318/mycollector/v1/traces`
-and metrics to `https://collector.example.com/v1/metrics/`
-(other signals, would they be defined, would be sent to their specific paths
-relative to `http://collector:4318/mycollector/`).
+and metrics to `https://collector.example.com/v1/metrics/`, using the default
+https port (443).
+Other signals, (if there were any) would be sent to their specific paths
+relative to `http://collector:4318/mycollector/`.
 
 ### Specify Protocol