OTLP Exporter: Make gzip compression the default

specification/protocol/exporter.md

@@ -15,21 +15,16 @@ The following configuration options MUST be available to configure the OTLP expo
 | Insecure | Whether to enable client transport security for the exporter's gRPC connection. This option only applies to OTLP/gRPC - OTLP/HTTP always uses the scheme provided for the `endpoint`. Implementations MAY choose to not implement the `insecure` option if it is not required or supported by the underlying gRPC client implementation. | `false` | `OTEL_EXPORTER_OTLP_INSECURE` `OTEL_EXPORTER_OTLP_SPAN_INSECURE` `OTEL_EXPORTER_OTLP_METRIC_INSECURE` |
 | Certificate File | The trusted certificate to use when verifying a server's TLS credentials. Should only be used for a secure connection. | n/a | `OTEL_EXPORTER_OTLP_CERTIFICATE` `OTEL_EXPORTER_OTLP_TRACES_CERTIFICATE` `OTEL_EXPORTER_OTLP_METRICS_CERTIFICATE` |
 | Headers | Key-value pairs to be used as headers associated with gRPC or HTTP requests. See [Specifying headers](./exporter.md#specifying-headers-via-environment-variables) for more details. | n/a | `OTEL_EXPORTER_OTLP_HEADERS` `OTEL_EXPORTER_OTLP_TRACES_HEADERS` `OTEL_EXPORTER_OTLP_METRICS_HEADERS` |
-| Compression | Compression key for supported compression types. Supported compression: `gzip`| No value [2] | `OTEL_EXPORTER_OTLP_COMPRESSION` `OTEL_EXPORTER_OTLP_TRACES_COMPRESSION` `OTEL_EXPORTER_OTLP_METRICS_COMPRESSION` |
+| Compression | Compression method used to compress HTTP(S) messages. Supported values: `gzip`, `none` | `gzip` [2]  | `OTEL_EXPORTER_OTLP_COMPRESSION` `OTEL_EXPORTER_OTLP_TRACES_COMPRESSION` `OTEL_EXPORTER_OTLP_METRICS_COMPRESSION` |
 | Timeout | Maximum time the OTLP exporter will wait for each batch export. | 10s | `OTEL_EXPORTER_OTLP_TIMEOUT` `OTEL_EXPORTER_OTLP_TRACES_TIMEOUT` `OTEL_EXPORTER_OTLP_METRICS_TIMEOUT` |
 | Protocol | The transport protocol. Options MAY include `grpc`, `http/protobuf`, and `http/json`. See [Specify Protocol](./exporter.md#specify-protocol) for more details. | `http/protobuf` [2] | `OTEL_EXPORTER_OTLP_PROTOCOL` `OTEL_EXPORTER_OTLP_TRACES_PROTOCOL` `OTEL_EXPORTER_OTLP_METRICS_PROTOCOL` |
 
 **[1]**: SDKs SHOULD default endpoint variables to use `https` scheme unless as they have good reasons to choose
 `http` scheme for the default (e.g., for backward compatibility reasons in a stable SDK release).
 
-**[2]**: If no compression value is explicitly specified, SIGs can default to the value they deem
-most useful among the supported options. This is especially important in the presence of technical constraints,
-e.g. directly sending telemetry data from mobile devices to backend servers.
-
-Supported values for `OTEL_EXPORTER_OTLP_*COMPRESSION` options:
-
-- `none` if compression is disabled.
-- `gzip` is the only specified compression method for now.
+**[2]**: SDKs SHOULD default the `OTEL_EXPORTER_OTLP_*COMPRESSION` options to use `gzip` compression
+unless as they have good reasons to choose `none` for the default (e.g., due to the presence
+of platform-specific technical constraints).
 
 <a name="per-signal-urls"></a>