docs: add response size limitation

CHANGELOG.md

@@ -6,6 +6,8 @@ The full list of changes can be found in the compare view for the respective rel
 
 ### Added
 
+- docs: add response body size limitation. [#781](https://github.com/open-telemetry/opentelemetry-proto/pull/781)
+
 ### Changed
 
 ### Fixed

docs/specification.md

@@ -161,6 +161,12 @@ The response MUST be the appropriate message (see below for
 the specific message to use in the [Full Success](#full-success),
 [Partial Success](#partial-success) and [Failure](#failures) cases).
 
+The client MUST limit the size of the response body when parsing it, including
+after decompression, to mitigate possible excessive memory usage caused by a
+misconfigured or malicious server. It is RECOMMENDED to limit the response body
+to 32 KiB. If the limit is exceeded, the client MUST treat the response as a
+non-retryable error and SHOULD record the fact that the response was discarded.
+
 ##### Full Success
 
 The success response indicates telemetry data is successfully accepted by the
@@ -479,6 +485,12 @@ The response body MUST be the appropriate serialized Protobuf message (see
 below for the specific message to use in the [Full Success](#full-success-1),
 [Partial Success](#partial-success-1) and [Failure](#failures-1) cases).
 
+The client MUST limit the size of the response body when parsing it, including
+after decompression, to mitigate possible excessive memory usage caused by a
+misconfigured or malicious server. It is RECOMMENDED to limit the response body
+to 32 KiB. If the limit is exceeded, the client MUST treat the response as a
+non-retryable error and SHOULD record the fact that the response was discarded.
+
 The server MUST set "Content-Type: application/x-protobuf" header if the
 response body is binary-encoded Protobuf payload. The server MUST set
 "Content-Type: application/json" if the response is JSON-encoded Protobuf