J.D. Meier, Srinath Vasireddy, Ashish Babbar, and Alex Mackman
Microsoft Corporation

May 2004

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patterns & practices Library

How to Use This Checklist

This checklist is a companion to Chapter 10, "Improving Web Services Performance"

Design Considerations

Check	Description
	Design chunky interfaces to reduce round trips.
	Prefer message-based programming over remote procedure call (RPC) style.
	Use literal message encoding for parameter formatting.
	Prefer primitive types for Web service parameters.
	Avoid maintaining server state between calls.
	Consider input validation for costly Web methods.
	Consider your approach to caching.
	Consider approaches for bulk data transfer and attachments.
	Avoid calling local Web Services.

Connections

Check	Description
	Configure the maxconnection attribute.
	Prioritize and allocate connections across discrete Web services.
	Use a single identity for outbound calls.
	Consider UnsafeAuthenticatedConnectionSharing with Windows Integrated Authentication.
	Use PreAuthenticate with Basic authentication.

Threading

Check	Description
	Tune the thread pool using the formula for reducing contention.
	Consider minIoThreads and minWorkerThreads for intermittent burst load.

One Way (Fire and Forget) Communication

Check	Description
	Consider using the OneWay attribute if you do not require a response.

Asynchronous Web Methods

Check	Description
	Use asynchronous Web methods for I/O operations.
	Do not use asynchronous Web methods when you depend on worker threads.

Asynchronous Invocation

Check	Description
	Consider calling Web services asynchronously when you have additional parallel work.
	Use asynchronous invocation to call multiple unrelated Web services.
	Call Web services asynchronously for UI responsiveness.

Timeouts

Check	Description
	Set your proxy timeout appropriately.
	Set your ASP.NET timeout greater than your Web service timeout.
	Abort connections for ASP.NET pages that timeout before a Web services call completes.
	Consider the responseDeadlockInterval attribute.

WebMethods

Check	Description
	Prefer primitive parameter types.
	Consider buffering.
	Consider caching responses.
	Enable session state only for Web methods that need it.

Serialization

Check	Description
	Reduce serialization with XmlIgnore.
	Reduce round trips.
	Consider XML compression.

Caching

Check	Description
	Consider output caching for less volatile data.
	Consider providing cache-related information to clients.
	Consider perimeter caching.

State Management

Check	Description
	Use session state only where it is needed.
	Avoid server affinity.

Attachments

Check	Description
	Prefer Base64 encoding. Direct Internet Message Encapsulation (DIME) is a supported part of Web Services Enhancements (WSE), but Microsoft® is not investing in this approach long-term. DIME is limited because the attachments are outside the SOAP envelope.

COM Interop

Check	Description
	Avoid single-threaded apartment (STA) COM objects.