diff --git a/.golangci.yml b/.golangci.yml
index e853e72..a800bb5 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -84,3 +84,7 @@ issues:
     - path: params.go
       linters:
         - goconst # allow string literals for WKT names
+    - path: protocol.go
+      linters:
+        - gochecknoglobals # allow Protocol global helpers
+      text: "(allProtocols|protocolToString) is a global variable"
diff --git a/protocol.go b/protocol.go
index 5cf497f..9ad131b 100644
--- a/protocol.go
+++ b/protocol.go
@@ -16,10 +16,10 @@ package vanguard
 
 import (
 	"bytes"
-	"fmt"
 	"io"
 	"net/http"
 	"net/textproto"
+	"strconv"
 	"strings"
 	"time"
 
@@ -33,13 +33,6 @@ const envelopeLen = 5
 type Protocol int
 
 const (
-	// The ordinal value of the protocol (other than the zero value) reflects
-	// the preference order. So Connect is the highest preferred protocol,
-	// then gRPC, etc.
-
-	// protocolUnknown is not a valid value. Since it is the zero value, this
-	// requires that all Protocol values must be explicitly initialized.
-	protocolUnknown = Protocol(0)
 	// ProtocolConnect indicates the Connect protocol. This protocol supports
 	// unary and streaming endpoints. However, bidirectional streams are only
 	// supported when combined with HTTP/2.
@@ -65,31 +58,31 @@ const (
 	//
 	// This protocol only supports unary and server-stream endpoints.
 	ProtocolREST
+)
 
-	// protocolMin is the minimum valid value for a Protocol.
-	protocolMin = ProtocolConnect
-	// protocolMax is the maximum valid value for a Protocol.
-	protocolMax = ProtocolREST
-
-	protocolNameConnect = "Connect"
-	protocolNameGRPC    = "gRPC"
-	protocolNameGRPCWeb = "gRPC-Web"
-	protocolNameREST    = "REST"
+var (
+	// allProtocols are all supported protocols in descending order of
+	// preference. The first protocol is the default protocol.
+	allProtocols = [...]Protocol{
+		ProtocolConnect,
+		ProtocolGRPC,
+		ProtocolGRPCWeb,
+		ProtocolREST,
+	}
+	protocolToString = map[Protocol]string{
+		ProtocolConnect: "Connect",
+		ProtocolGRPC:    "gRPC",
+		ProtocolGRPCWeb: "gRPC-Web",
+		ProtocolREST:    "REST",
+	}
 )
 
 func (p Protocol) String() string {
-	switch p {
-	case ProtocolConnect:
-		return protocolNameConnect
-	case ProtocolGRPC:
-		return protocolNameGRPC
-	case ProtocolGRPCWeb:
-		return protocolNameGRPCWeb
-	case ProtocolREST:
-		return protocolNameREST
-	default:
-		return fmt.Sprintf("unknown protocol (%d)", p)
+	s, ok := protocolToString[p]
+	if !ok {
+		return strconv.Itoa(int(p))
 	}
+	return s
 }
 
 func (p Protocol) serverHandler(op *operation) serverProtocolHandler {
diff --git a/protocol_connect.go b/protocol_connect.go
index 894aa59..d673bef 100644
--- a/protocol_connect.go
+++ b/protocol_connect.go
@@ -37,11 +37,6 @@ import (
 )
 
 const (
-	protocolNameConnectUnary     = protocolNameConnect + " unary"
-	protocolNameConnectUnaryGet  = protocolNameConnectUnary + " (GET)"
-	protocolNameConnectUnaryPost = protocolNameConnectUnary + " (POST)"
-	protocolNameConnectStream    = protocolNameConnect + " stream"
-
 	// TODO: Extract more constants for header names and values.
 	contentTypeJSON = "application/json"
 )
@@ -154,7 +149,7 @@ func (c connectUnaryGetClientProtocol) prepareMarshalledResponse(_ *operation, _
 }
 
 func (c connectUnaryGetClientProtocol) String() string {
-	return protocolNameConnectUnaryGet
+	return c.protocol().String() + " unary (GET)"
 }
 
 // connectUnaryPostClientProtocol implements the Connect protocol for
@@ -239,7 +234,7 @@ func (c connectUnaryPostClientProtocol) encodeEnd(op *operation, end *responseEn
 }
 
 func (c connectUnaryPostClientProtocol) String() string {
-	return protocolNameConnectUnaryPost
+	return c.protocol().String() + " unary (POST)"
 }
 
 // connectUnaryServerProtocol implements the Connect protocol for
@@ -402,7 +397,7 @@ func (c connectUnaryServerProtocol) requestLine(op *operation, msg proto.Message
 }
 
 func (c connectUnaryServerProtocol) String() string {
-	return protocolNameConnectUnary
+	return c.protocol().String() + " unary"
 }
 
 // connectStreamClientProtocol implements the Connect protocol for
@@ -488,7 +483,7 @@ func (c connectStreamClientProtocol) encodeEnvelope(env envelope) envelopeBytes
 }
 
 func (c connectStreamClientProtocol) String() string {
-	return protocolNameConnectStream
+	return c.protocol().String() + " stream"
 }
 
 // connectStreamServerProtocol implements the Connect protocol for
@@ -585,7 +580,7 @@ func (c connectStreamServerProtocol) decodeEndFromMessage(_ *operation, buffer *
 }
 
 func (c connectStreamServerProtocol) String() string {
-	return protocolNameConnectStream
+	return c.protocol().String() + " stream"
 }
 
 func connectExtractUnaryTrailers(headers http.Header) http.Header {
diff --git a/protocol_grpc.go b/protocol_grpc.go
index 60bad54..2c97f25 100644
--- a/protocol_grpc.go
+++ b/protocol_grpc.go
@@ -93,7 +93,7 @@ func (g grpcClientProtocol) encodeEnvelope(env envelope) envelopeBytes {
 }
 
 func (g grpcClientProtocol) String() string {
-	return protocolNameGRPC
+	return g.protocol().String()
 }
 
 // grpcServerProtocol implements the gRPC protocol for
@@ -148,7 +148,7 @@ func (g grpcServerProtocol) decodeEndFromMessage(_ *operation, _ *bytes.Buffer)
 }
 
 func (g grpcServerProtocol) String() string {
-	return protocolNameGRPC
+	return g.protocol().String()
 }
 
 // grpcClientProtocol implements the gRPC protocol for
@@ -209,7 +209,7 @@ func (g grpcWebClientProtocol) encodeEnvelope(env envelope) envelopeBytes {
 }
 
 func (g grpcWebClientProtocol) String() string {
-	return protocolNameGRPCWeb
+	return g.protocol().String()
 }
 
 // grpcServerProtocol implements the gRPC-Web protocol for
@@ -275,7 +275,7 @@ func (g grpcWebServerProtocol) decodeEndFromMessage(_ *operation, buffer *bytes.
 }
 
 func (g grpcWebServerProtocol) String() string {
-	return protocolNameGRPCWeb
+	return g.protocol().String()
 }
 
 func grpcExtractRequestMeta(contentTypeShort, contentTypePrefix string, headers http.Header) (requestMeta, error) {
diff --git a/protocol_rest.go b/protocol_rest.go
index f968e65..a101481 100644
--- a/protocol_rest.go
+++ b/protocol_rest.go
@@ -244,7 +244,7 @@ func (r restClientProtocol) prepareMarshalledResponse(op *operation, base []byte
 }
 
 func (r restClientProtocol) String() string {
-	return protocolNameREST
+	return r.protocol().String()
 }
 
 // restServerProtocol implements the REST protocol for
@@ -392,7 +392,7 @@ func (r restServerProtocol) requestLine(op *operation, req proto.Message) (urlPa
 }
 
 func (r restServerProtocol) String() string {
-	return protocolNameREST
+	return r.protocol().String()
 }
 
 // Decode timeout as a float in seconds from X-Server-Timeout header.
diff --git a/transcoder.go b/transcoder.go
index 6080577..0acc481 100644
--- a/transcoder.go
+++ b/transcoder.go
@@ -86,7 +86,8 @@ func (t *Transcoder) registerService(svc *Service, svcOpts serviceOptions) error
 		return fmt.Errorf("service %s was configured with no target protocols", svc.schema.FullName())
 	}
 	for protocol := range svcOpts.protocols {
-		if protocol <= protocolUnknown || protocol > protocolMax {
+		_, isKnown := protocolToString[protocol]
+		if !isKnown {
 			return fmt.Errorf("protocol %d is not a valid value", protocol)
 		}
 	}
@@ -422,7 +423,7 @@ func (o *operation) validate(transcoder *Transcoder) error {
 	if _, supportsProtocol := o.methodConf.protocols[clientProtoHandler.protocol()]; supportsProtocol {
 		o.server.protocol = clientProtoHandler.protocol().serverHandler(o)
 	} else {
-		for protocol := protocolMin; protocol <= protocolMax; protocol++ {
+		for _, protocol := range allProtocols {
 			if _, supportsProtocol := o.methodConf.protocols[protocol]; supportsProtocol {
 				o.server.protocol = protocol.serverHandler(o)
 				break