Link to proposal for gRPC metrics

docs/rpc/rpc-metrics.md

@@ -61,6 +61,8 @@ metrics can be filtered for finer grain analysis.
 >   for at least six months after it starts emitting both sets of conventions.
 > * SHOULD drop the environment variable in the next major version.
 
+Maintainers of gRPC have decided to create a different [spec](https://github.com/grpc/proposal/blob/master/A66-otel-stats.md) due to limitations on what information can be recorded by the various implementations of gRPC and differences in concepts such as a `call` and an `attempt` compared to other RPC systems.
+
 ## Metric instruments
 
 The following metric instruments MUST be used to describe RPC operations. They
@@ -223,7 +225,7 @@ measurements.
 | [`network.type`](../attributes-registry/network.md) | string | [OSI network layer](https://osi-model.com/network-layer/) or non-OSI equivalent. [2] | `ipv4`; `ipv6` | Recommended |
 | [`rpc.method`](../attributes-registry/rpc.md) | string | The name of the (logical) method being called, must be equal to the $method part in the span name. [3] | `exampleMethod` | Recommended |
 | [`rpc.service`](../attributes-registry/rpc.md) | string | The full (logical) name of the service being called, including its package name, if applicable. [4] | `myservice.EchoService` | Recommended |
-| [`rpc.system`](../attributes-registry/rpc.md) | string | A string identifying the remoting system. See below for a list of well-known identifiers. | `grpc` | Required |
+| [`rpc.system`](../attributes-registry/rpc.md) | string | A string identifying the remoting system. See below for a list of well-known identifiers. | `connect_rpc` | Required |
 | [`server.address`](../attributes-registry/server.md) | string | Server domain name if available without reverse DNS lookup; otherwise, IP address or Unix domain socket name. [5] | `example.com`; `10.1.2.80`; `/tmp/my.sock` | Recommended |
 | [`server.port`](../attributes-registry/server.md) | int | Server port number. [6] | `80`; `8080`; `443` | Recommended |
 
@@ -263,7 +265,6 @@ different processes could be listening on TCP port 12345 and UDP port 12345.
 
 | Value  | Description |
 |---|---|
-| `grpc` | gRPC |
 | `java_rmi` | Java RMI |
 | `dotnet_wcf` | .NET WCF |
 | `apache_dubbo` | Apache Dubbo |
@@ -285,7 +286,6 @@ One process can expose multiple RPC endpoints and thus have multiple RPC service
 More specific Semantic Conventions are defined for the following RPC technologies:
 
 * [Connect](connect-rpc.md): Semantic Conventions for *Connect RPC*.
-* [gRPC](grpc.md): Semantic Conventions for *gRPC*.
 * [JSON-RPC](json-rpc.md): Semantic Conventions for *JSON-RPC*.
 
 [DocumentStatus]: https://github.com/open-telemetry/opentelemetry-specification/tree/v1.26.0/specification/document-status.md