Change default OTLP port number

Contributes to #1148

Note that a separate port is used for OTLP/HTTP for now. There is currently work
in progress to confirm that we can use the same port. Once we have the confirmation
I will update the spec again to use one port.

CHANGELOG.md

@@ -9,6 +9,8 @@ release.
 
 New:
 
+- Change default OTLP port number
+  ([#1221](https://github.com/open-telemetry/opentelemetry-specification/pull/1221))
 - Add performance benchmark specification
   ([#748](https://github.com/open-telemetry/opentelemetry-specification/pull/748))
 - Enforce that the Baggage API must be fully functional, even without an installed SDK.

specification/protocol/otlp.md

@@ -289,7 +289,7 @@ some in beta.
 
 #### Default Port
 
-The default network port for OTLP/gRPC is 55680.
+The default network port for OTLP/gRPC is 4317.
 
 ### OTLP/HTTP
 
@@ -445,7 +445,7 @@ connections SHOULD be configurable.
 
 #### Default Port
 
-The default network port for OTLP/HTTP is 55681. There is currently an [open
+The default network port for OTLP/HTTP is 4318. There is currently an [open
 issue](https://github.com/open-telemetry/opentelemetry-collector/issues/1256) to
 use the same port for OTLP/gRPC and OTLP/HTTP. In that case this spec will be
 updated to use the same default port for OTLP/gRPC and OTLP/HTTP.