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Runtime configuration options for networking

HTTP/2 protocol

  • Configures whether support for the HTTP/2 protocol is enabled.
  • If you omit this setting, support for the HTTP/2 protocol is enabled. This is equivalent to setting the value to true.
Setting name Values
runtimeconfig.json System.Net.Http.SocketsHttpHandler.Http2Support false - disabled
true - enabled
Environment variable DOTNET_SYSTEM_NET_HTTP_SOCKETSHTTPHANDLER_HTTP2SUPPORT 0 - disabled
1 - enabled

This configuration setting doesn't have a specific MSBuild property. However, you can add a RuntimeHostConfigurationOption MSBuild item instead. Use the runtimeconfig.json setting name as the value of the Include attribute. For an example, see MSBuild properties.

HTTP/3 protocol

  • Starting in .NET 7, HTTP/3 is enabled by default.
Setting name Values
runtimeconfig.json System.Net.SocketsHttpHandler.Http3Support false - disabled
true - enabled
Environment variable DOTNET_SYSTEM_NET_HTTP_SOCKETSHTTPHANDLER_HTTP3SUPPORT 0 - disabled
1 - enabled

This configuration setting doesn't have a specific MSBuild property. However, you can add a RuntimeHostConfigurationOption MSBuild item instead. Use the runtimeconfig.json setting name as the value of the Include attribute. For an example, see MSBuild properties.

SPN creation in HttpClient (.NET 6 and later)

  • Impacts generation of service principal names (SPN) for Kerberos and NTLM authentication when Host header is missing and the target isn't running on the default port.
  • .NET 6 and later versions don't include the port in the SPN by default. However, the behavior is configurable.
Setting name Values
runtimeconfig.json System.Net.Http.UsePortInSpn true - include port number in SPN, for example, HTTP/host:port
false - don't include port in SPN, for example, HTTP/host
Environment variable DOTNET_SYSTEM_NET_HTTP_USEPORTINSPN 1 - include port number in SPN, for example, HTTP/host:port
0 - don't include port in SPN, for example, HTTP/host

This configuration setting doesn't have a specific MSBuild property. However, you can add a RuntimeHostConfigurationOption MSBuild item instead. Use the runtimeconfig.json setting name as the value of the Include attribute. For an example, see MSBuild properties.

HTTP/2 dynamic window scaling

  • Configures whether the HTTP/2 dynamic window scaling algorithm is disabled for flow control. The algorithm is enabled by default.
  • When set to true, the dynamic window scaling algorithm is disabled.
Setting name Values
runtimeconfig.json System.Net.SocketsHttpHandler.Http2FlowControl.DisableDynamicWindowSizing false - enabled (default)
true - disabled
Environment variable DOTNET_SYSTEM_NET_HTTP_SOCKETSHTTPHANDLER_HTTP2FLOWCONTROL_DISABLEDYNAMICWINDOWSIZING 0 - enabled (default)
1 - disabled

This configuration setting doesn't have a specific MSBuild property. However, you can add a RuntimeHostConfigurationOption MSBuild item instead. Use the runtimeconfig.json setting name as the value of the Include attribute. For an example, see MSBuild properties.

HTTP/2 stream receive window size

  • Configures the maximum size of the HTTP/2 stream receive window.
  • Defaults to 16 MB. Values below 65,535 are clamped to 65,535. There's no hard upper limit, but increasing this setting beyond the default is only beneficial on networks that are both high throughput and high latency.
Setting name Values
Environment variable DOTNET_SYSTEM_NET_HTTP_SOCKETSHTTPHANDLER_FLOWCONTROL_MAXSTREAMWINDOWSIZE Integer (default: 16 MB; minimum: 65,535)

HTTP/2 stream window scale threshold

  • Configures the multiplier that controls how aggressively the HTTP/2 stream-receive window grows. Higher values result in a more conservative window growth, which reduces peak throughput.
  • Defaults to 1.0. Values below 0 are reset to the default. There's no hard upper limit, but values much above the default progressively limit per-request throughput.

Note

This setting is intended for advanced diagnostics and internal tuning. Most developers don't need to change it.

Setting name Values
Environment variable DOTNET_SYSTEM_NET_HTTP_SOCKETSHTTPHANDLER_FLOWCONTROL_STREAMWINDOWSCALETHRESHOLDMULTIPLIER Float (default: 1.0; minimum: 0)

HTTP activity propagation

Configures whether distributed tracing activity propagation is enabled for HttpClient. When enabled, outgoing HTTP requests propagate trace context headers (such as traceparent) for distributed tracing tools like OpenTelemetry.

Setting name Values
runtimeconfig.json System.Net.Http.EnableActivityPropagation true - enabled (default)
false - disabled
Environment variable DOTNET_SYSTEM_NET_HTTP_ENABLEACTIVITYPROPAGATION 1 - enabled (default)
0 - disabled

This configuration setting doesn't have a specific MSBuild property. However, you can add a RuntimeHostConfigurationOption MSBuild item instead. Use the runtimeconfig.json setting name as the value of the Include attribute. For an example, see MSBuild properties.

Pending connection timeout on request completion

Configures the timeout (in milliseconds) for completing a pending connection attempt after its initiating HTTP request finishes. When a connection is still being established after the request completes, this timeout determines how long to wait before abandoning the connection attempt.

  • Defaults to 5000 (5 seconds).
  • Set to -1 to wait indefinitely until the connection completes.
  • Set to 0 to cancel the pending connection immediately when the request completes.
  • There's no hard upper limit, but very large values are impractical.
Setting name Values
runtimeconfig.json System.Net.SocketsHttpHandler.PendingConnectionTimeoutOnRequestCompletion Integer (default: 5000)
Environment variable DOTNET_SYSTEM_NET_HTTP_SOCKETSHTTPHANDLER_PENDINGCONNECTIONTIMEOUTONREQUESTCOMPLETION Integer (default: 5000)

This configuration setting doesn't have a specific MSBuild property. However, you can add a RuntimeHostConfigurationOption MSBuild item instead. Use the runtimeconfig.json setting name as the value of the Include attribute. For an example, see MSBuild properties.

Proxy pre-authentication

When enabled, SocketsHttpHandler proactively sends Basic proxy authentication credentials on the first request instead of waiting for a 407 challenge response from the proxy. This is useful for proxies that don't send 407 challenge responses.

Setting name Values
runtimeconfig.json System.Net.Http.SocketsHttpHandler.ProxyPreAuthenticate false - disabled (default)
true - enabled
Environment variable DOTNET_SYSTEM_NET_HTTP_SOCKETSHTTPHANDLER_PROXYPREAUTHENTICATE 0 - disabled (default)
1 - enabled

This configuration setting doesn't have a specific MSBuild property. However, you can add a RuntimeHostConfigurationOption MSBuild item instead. Use the runtimeconfig.json setting name as the value of the Include attribute. For an example, see MSBuild properties.

Maximum connections per server

Configures the maximum number of simultaneous TCP connections that SocketsHttpHandler opens to a single server. The handler ignores values less than 1 and uses the default.

  • Defaults to unlimited (int.MaxValue).
Setting name Values
runtimeconfig.json System.Net.SocketsHttpHandler.MaxConnectionsPerServer Integer (default: unlimited)
Environment variable DOTNET_SYSTEM_NET_HTTP_SOCKETSHTTPHANDLER_MAXCONNECTIONSPERSERVER Integer (default: unlimited)

This configuration setting doesn't have a specific MSBuild property. However, you can add a RuntimeHostConfigurationOption MSBuild item instead. Use the runtimeconfig.json setting name as the value of the Include attribute. For an example, see MSBuild properties.

Socket inline completions

Configures whether socket continuations are allowed to run on the event thread instead of being dispatched to the System.Threading.ThreadPool. Enabling this setting can improve performance in some scenarios. However, it might degrade performance if expensive work holds the I/O thread for longer than needed.

Note

Test to make sure enabling this setting helps performance in your specific scenario.

Setting name Values
Environment variable DOTNET_SYSTEM_NET_SOCKETS_INLINE_COMPLETIONS 0 - disabled (default)
1 - enabled

Socket thread count

Configures the number of threads used for socket I/O. When not overridden, the value is calculated based on processor count and architecture. Practical values are in the range [1, ProcessorCount]. Values outside this range aren't rejected but are unlikely to improve performance.

Note

This setting is intended for extreme load scenarios. Most developers don't need to change it.

Setting name Values
Environment variable DOTNET_SYSTEM_NET_SOCKETS_THREAD_COUNT Integer

IPv6

Configures whether Internet Protocol version 6 (IPv6) is disabled.

Setting name Values
runtimeconfig.json System.Net.DisableIPv6 false - enabled (default)
true - disabled
Environment variable DOTNET_SYSTEM_NET_DISABLEIPV6 0 - enabled (default)
1 - disabled

This configuration setting doesn't have a specific MSBuild property. However, you can add a RuntimeHostConfigurationOption MSBuild item instead. Use the runtimeconfig.json setting name as the value of the Include attribute. For an example, see MSBuild properties.

TLS session resumption

Control whether TLS session resumption disables TLS session resumption for SslStream. Session resumption allows TLS reconnections to skip a full handshake by reusing previously negotiated session parameters, which reduces latency.

Setting name Values
runtimeconfig.json System.Net.Security.DisableTlsResume false - enabled (default)
true - disabled
Environment variable DOTNET_SYSTEM_NET_SECURITY_DISABLETLSRESUME 0 - enabled (default)
1 - disabled

This configuration setting doesn't have a specific MSBuild property. However, you can add a RuntimeHostConfigurationOption MSBuild item instead. Use the runtimeconfig.json setting name as the value of the Include attribute. For an example, see MSBuild properties.

Server AIA downloads

When enabled, the TLS client automatically downloads intermediate certificates from Authority Information Access (AIA) extension URLs in server certificates. This allows the client to build a complete certificate chain even when the server doesn't send the full chain.

Setting name Values
runtimeconfig.json System.Net.Security.EnableServerAiaDownloads false - disabled (default)
true - enabled
Environment variable DOTNET_SYSTEM_NET_SECURITY_ENABLESERVERAIADOWNLOADS 0 - disabled (default)
1 - enabled

This configuration setting doesn't have a specific MSBuild property. However, you can add a RuntimeHostConfigurationOption MSBuild item instead. Use the runtimeconfig.json setting name as the value of the Include attribute. For an example, see MSBuild properties.

QUIC configuration caching

Disables caching of MsQuic configuration objects. When enabled (default), the system caches and reuses configuration objects across connections, which reduces the overhead of TLS and QUIC setup for repeated connections with the same parameters.

Setting name Values
runtimeconfig.json System.Net.Quic.DisableConfigurationCache false - caching enabled (default)
true - caching disabled
Environment variable DOTNET_SYSTEM_NET_QUIC_DISABLE_CONFIGURATION_CACHE 0 - caching enabled (default)
1 - caching disabled

This configuration setting doesn't have a specific MSBuild property. However, you can add a RuntimeHostConfigurationOption MSBuild item instead. Use the runtimeconfig.json setting name as the value of the Include attribute. For an example, see MSBuild properties.

App-local MsQuic (Windows)

When enabled, the QUIC implementation uses the MsQuic library from the application directory instead of the system-provided library bundled with the .NET assembly.

Setting name Values
runtimeconfig.json System.Net.Quic.AppLocalMsQuic false - use system MsQuic (default)
true - use app-local MsQuic

This configuration setting doesn't have a specific MSBuild property. However, you can add a RuntimeHostConfigurationOption MSBuild item instead. Use the runtimeconfig.json setting name as the value of the Include attribute. For an example, see MSBuild properties.

HttpListener kernel response buffering (Windows)

When enabled, HttpListener buffers response data in the kernel via HTTP.sys. Kernel buffering can significantly improve throughput over high-latency connections for applications that use synchronous I/O or asynchronous I/O with at most one outstanding write at a time. Don't enable this setting for applications with multiple concurrent outstanding writes.

Note

Enabling kernel response buffering can result in higher CPU and memory usage by HTTP.sys.

Setting name Values
runtimeconfig.json System.Net.HttpListener.EnableKernelResponseBuffering false - disabled (default)
true - enabled

This configuration setting doesn't have a specific MSBuild property. However, you can add a RuntimeHostConfigurationOption MSBuild item instead. Use the runtimeconfig.json setting name as the value of the Include attribute. For an example, see MSBuild properties.

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