diff --git a/benchmarks/Microsoft.AspNetCore.SignalR.Microbenchmarks/HubConnectionContextBenchmark.cs b/benchmarks/Microsoft.AspNetCore.SignalR.Microbenchmarks/HubConnectionContextBenchmark.cs
index 6431052e45..0f13aba113 100644
--- a/benchmarks/Microsoft.AspNetCore.SignalR.Microbenchmarks/HubConnectionContextBenchmark.cs
+++ b/benchmarks/Microsoft.AspNetCore.SignalR.Microbenchmarks/HubConnectionContextBenchmark.cs
@@ -92,7 +92,7 @@ namespace Microsoft.AspNetCore.SignalR.Microbenchmarks
             _instance = instance;
         }
 
-        public IHubProtocol GetProtocol(string protocolName, IList<string> supportedProtocols)
+        public IHubProtocol GetProtocol(string protocolName, IReadOnlyList<string> supportedProtocols)
         {
             return _instance;
         }
diff --git a/src/Microsoft.AspNetCore.SignalR.Common/CancelInvocationMessage.cs b/src/Microsoft.AspNetCore.SignalR.Common/Protocol/CancelInvocationMessage.cs
similarity index 100%
rename from src/Microsoft.AspNetCore.SignalR.Common/CancelInvocationMessage.cs
rename to src/Microsoft.AspNetCore.SignalR.Common/Protocol/CancelInvocationMessage.cs
diff --git a/src/Microsoft.AspNetCore.SignalR.Common/CloseMessage.cs b/src/Microsoft.AspNetCore.SignalR.Common/Protocol/CloseMessage.cs
similarity index 100%
rename from src/Microsoft.AspNetCore.SignalR.Common/CloseMessage.cs
rename to src/Microsoft.AspNetCore.SignalR.Common/Protocol/CloseMessage.cs
diff --git a/src/Microsoft.AspNetCore.SignalR.Common/CompletionMessage.cs b/src/Microsoft.AspNetCore.SignalR.Common/Protocol/CompletionMessage.cs
similarity index 100%
rename from src/Microsoft.AspNetCore.SignalR.Common/CompletionMessage.cs
rename to src/Microsoft.AspNetCore.SignalR.Common/Protocol/CompletionMessage.cs
diff --git a/src/Microsoft.AspNetCore.SignalR.Common/HandshakeProtocol.cs b/src/Microsoft.AspNetCore.SignalR.Common/Protocol/HandshakeProtocol.cs
similarity index 100%
rename from src/Microsoft.AspNetCore.SignalR.Common/HandshakeProtocol.cs
rename to src/Microsoft.AspNetCore.SignalR.Common/Protocol/HandshakeProtocol.cs
diff --git a/src/Microsoft.AspNetCore.SignalR.Common/HandshakeRequestMessage.cs b/src/Microsoft.AspNetCore.SignalR.Common/Protocol/HandshakeRequestMessage.cs
similarity index 100%
rename from src/Microsoft.AspNetCore.SignalR.Common/HandshakeRequestMessage.cs
rename to src/Microsoft.AspNetCore.SignalR.Common/Protocol/HandshakeRequestMessage.cs
diff --git a/src/Microsoft.AspNetCore.SignalR.Common/HandshakeResponseMessage.cs b/src/Microsoft.AspNetCore.SignalR.Common/Protocol/HandshakeResponseMessage.cs
similarity index 100%
rename from src/Microsoft.AspNetCore.SignalR.Common/HandshakeResponseMessage.cs
rename to src/Microsoft.AspNetCore.SignalR.Common/Protocol/HandshakeResponseMessage.cs
diff --git a/src/Microsoft.AspNetCore.SignalR.Common/HubInvocationMessage.cs b/src/Microsoft.AspNetCore.SignalR.Common/Protocol/HubInvocationMessage.cs
similarity index 100%
rename from src/Microsoft.AspNetCore.SignalR.Common/HubInvocationMessage.cs
rename to src/Microsoft.AspNetCore.SignalR.Common/Protocol/HubInvocationMessage.cs
diff --git a/src/Microsoft.AspNetCore.SignalR.Common/HubMessage.cs b/src/Microsoft.AspNetCore.SignalR.Common/Protocol/HubMessage.cs
similarity index 100%
rename from src/Microsoft.AspNetCore.SignalR.Common/HubMessage.cs
rename to src/Microsoft.AspNetCore.SignalR.Common/Protocol/HubMessage.cs
diff --git a/src/Microsoft.AspNetCore.SignalR.Common/HubMethodInvocationMessage.cs b/src/Microsoft.AspNetCore.SignalR.Common/Protocol/HubMethodInvocationMessage.cs
similarity index 100%
rename from src/Microsoft.AspNetCore.SignalR.Common/HubMethodInvocationMessage.cs
rename to src/Microsoft.AspNetCore.SignalR.Common/Protocol/HubMethodInvocationMessage.cs
diff --git a/src/Microsoft.AspNetCore.SignalR.Common/HubProtocolConstants.cs b/src/Microsoft.AspNetCore.SignalR.Common/Protocol/HubProtocolConstants.cs
similarity index 100%
rename from src/Microsoft.AspNetCore.SignalR.Common/HubProtocolConstants.cs
rename to src/Microsoft.AspNetCore.SignalR.Common/Protocol/HubProtocolConstants.cs
diff --git a/src/Microsoft.AspNetCore.SignalR.Common/HubProtocolExtensions.cs b/src/Microsoft.AspNetCore.SignalR.Common/Protocol/HubProtocolExtensions.cs
similarity index 100%
rename from src/Microsoft.AspNetCore.SignalR.Common/HubProtocolExtensions.cs
rename to src/Microsoft.AspNetCore.SignalR.Common/Protocol/HubProtocolExtensions.cs
diff --git a/src/Microsoft.AspNetCore.SignalR.Common/IHubProtocol.cs b/src/Microsoft.AspNetCore.SignalR.Common/Protocol/IHubProtocol.cs
similarity index 100%
rename from src/Microsoft.AspNetCore.SignalR.Common/IHubProtocol.cs
rename to src/Microsoft.AspNetCore.SignalR.Common/Protocol/IHubProtocol.cs
diff --git a/src/Microsoft.AspNetCore.SignalR.Common/PingMessage.cs b/src/Microsoft.AspNetCore.SignalR.Common/Protocol/PingMessage.cs
similarity index 100%
rename from src/Microsoft.AspNetCore.SignalR.Common/PingMessage.cs
rename to src/Microsoft.AspNetCore.SignalR.Common/Protocol/PingMessage.cs
diff --git a/src/Microsoft.AspNetCore.SignalR.Common/StreamItemMessage.cs b/src/Microsoft.AspNetCore.SignalR.Common/Protocol/StreamItemMessage.cs
similarity index 99%
rename from src/Microsoft.AspNetCore.SignalR.Common/StreamItemMessage.cs
rename to src/Microsoft.AspNetCore.SignalR.Common/Protocol/StreamItemMessage.cs
index 350275c17a..cf885e837f 100644
--- a/src/Microsoft.AspNetCore.SignalR.Common/StreamItemMessage.cs
+++ b/src/Microsoft.AspNetCore.SignalR.Common/Protocol/StreamItemMessage.cs
@@ -1,7 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-
 namespace Microsoft.AspNetCore.SignalR.Protocol
 {
     public class StreamItemMessage : HubInvocationMessage
diff --git a/src/Microsoft.AspNetCore.SignalR.Core/HubConnectionContext.cs b/src/Microsoft.AspNetCore.SignalR.Core/HubConnectionContext.cs
index 55fed6489b..9724db8259 100644
--- a/src/Microsoft.AspNetCore.SignalR.Core/HubConnectionContext.cs
+++ b/src/Microsoft.AspNetCore.SignalR.Core/HubConnectionContext.cs
@@ -273,7 +273,7 @@ namespace Microsoft.AspNetCore.SignalR
             Task.Factory.StartNew(_abortedCallback, this);
         }
 
-        internal async Task<bool> HandshakeAsync(TimeSpan timeout, IList<string> supportedProtocols, IHubProtocolResolver protocolResolver,
+        internal async Task<bool> HandshakeAsync(TimeSpan timeout, IReadOnlyList<string> supportedProtocols, IHubProtocolResolver protocolResolver,
             IUserIdProvider userIdProvider, bool enableDetailedErrors)
         {
             try
diff --git a/src/Microsoft.AspNetCore.SignalR.Core/HubConnectionHandler.cs b/src/Microsoft.AspNetCore.SignalR.Core/HubConnectionHandler.cs
index 5e128d4e7e..e9bcbf64bb 100644
--- a/src/Microsoft.AspNetCore.SignalR.Core/HubConnectionHandler.cs
+++ b/src/Microsoft.AspNetCore.SignalR.Core/HubConnectionHandler.cs
@@ -2,6 +2,8 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Generic;
+using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Connections;
 using Microsoft.AspNetCore.SignalR.Core;
@@ -61,7 +63,8 @@ namespace Microsoft.AspNetCore.SignalR
 
             var connectionContext = new HubConnectionContext(connection, keepAlive, _loggerFactory);
 
-            if (!await connectionContext.HandshakeAsync(handshakeTimeout, supportedProtocols, _protocolResolver, _userIdProvider, _enableDetailedErrors))
+            var resolvedSupportedProtocols = (supportedProtocols as IReadOnlyList<string>) ?? supportedProtocols.ToList();
+            if (!await connectionContext.HandshakeAsync(handshakeTimeout, resolvedSupportedProtocols, _protocolResolver, _userIdProvider, _enableDetailedErrors))
             {
                 return;
             }
diff --git a/src/Microsoft.AspNetCore.SignalR.Core/Internal/IHubProtocolResolver.cs b/src/Microsoft.AspNetCore.SignalR.Core/IHubProtocolResolver.cs
similarity index 72%
rename from src/Microsoft.AspNetCore.SignalR.Core/Internal/IHubProtocolResolver.cs
rename to src/Microsoft.AspNetCore.SignalR.Core/IHubProtocolResolver.cs
index 861acbe5d8..5444720d4f 100644
--- a/src/Microsoft.AspNetCore.SignalR.Core/Internal/IHubProtocolResolver.cs
+++ b/src/Microsoft.AspNetCore.SignalR.Core/IHubProtocolResolver.cs
@@ -4,11 +4,11 @@
 using System.Collections.Generic;
 using Microsoft.AspNetCore.SignalR.Protocol;
 
-namespace Microsoft.AspNetCore.SignalR.Internal
+namespace Microsoft.AspNetCore.SignalR
 {
     public interface IHubProtocolResolver
     {
         IReadOnlyList<IHubProtocol> AllProtocols { get; }
-        IHubProtocol GetProtocol(string protocolName, IList<string> supportedProtocols);
+        IHubProtocol GetProtocol(string protocolName, IReadOnlyList<string> supportedProtocols);
     }
 }
diff --git a/src/Microsoft.AspNetCore.SignalR.Core/Internal/DefaultHubProtocolResolver.cs b/src/Microsoft.AspNetCore.SignalR.Core/Internal/DefaultHubProtocolResolver.cs
index c44b303878..614d3c65df 100644
--- a/src/Microsoft.AspNetCore.SignalR.Core/Internal/DefaultHubProtocolResolver.cs
+++ b/src/Microsoft.AspNetCore.SignalR.Core/Internal/DefaultHubProtocolResolver.cs
@@ -36,7 +36,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal
             }
         }
 
-        public IHubProtocol GetProtocol(string protocolName, IList<string> supportedProtocols)
+        public virtual IHubProtocol GetProtocol(string protocolName, IReadOnlyList<string> supportedProtocols)
         {
             protocolName = protocolName ?? throw new ArgumentNullException(nameof(protocolName));