Update sdk-environment-variables.md

specification/sdk-environment-variables.md

@@ -126,7 +126,7 @@ See [OpenTelemetry Protocol Exporter Configuration Options](./protocol/exporter.
 
 | Name                            | Description                                                      | Default                                                                                          |
 |---------------------------------|------------------------------------------------------------------|--------------------------------------------------------------------------------------------------|
-| OTEL_EXPORTER_JAEGER_PROTOCOL   | The transport protocol. Options MAY include [`http/thrift.binary`][jaeger_http], [`grpc`][jaeger_grpc], [`udp/thrift.compact`][jaeger_udp], [`udp/thrift.binary`][jaeger_udp] | `http/thrift.binary` [1] |
+| OTEL_EXPORTER_JAEGER_PROTOCOL   | The transport protocol. The value MUST be one of: [`http/thrift.binary`][jaeger_http], [`grpc`][jaeger_grpc], [`udp/thrift.compact`][jaeger_udp], [`udp/thrift.binary`][jaeger_udp] | `http/thrift.binary` [1] |
 | OTEL_EXPORTER_JAEGER_ENDPOINT (`http/thrift.binary` protocol) | Full URL of the [Jaeger HTTP endpoint][jaeger_collector] | `http://localhost:14268/api/traces`                                        |
 | OTEL_EXPORTER_JAEGER_ENDPOINT (`grpc` protocol) | URL of the [Jaeger gRPC endpoint][jaeger_collector] | `http://localhost:14250`                                                                      |
 | OTEL_EXPORTER_JAEGER_TIMEOUT (`http/thrift.binary`, `grpc` protocols) | Maximum time the Jaeger exporter will wait for each batch export | 10s                                                        |