Difference between IIS 6.0,7.0,7.5.8.0,8.5

• Anonymous authentication
• Basic access authentication
• Digest access authentication
• Integrated Windows Authentication
• UNC authentication
• .NET Passport Authentication (Removed in Windows Server 2008 and IIS 7.0)
• Certificate authentication

• Security modules – Used to perform many tasks related to security in the request-processing pipeline, such as specifying authentication schemes, performing URL authorization, and filtering requests.
• Content modules – Used to perform tasks related to content in the request-processing pipeline, such as processing requests for static files, returning a default page when a client does not specify a resource in a request, and listing the contents of a directory.
• Compression modules – Used to perform tasks related to compression in the request-processing pipeline, such as compressing responses, applying Gzip compression transfer coding to responses, and performing pre-compression of static content.
• Caching modules – Used to perform tasks related to caching in the request-processing pipeline, such as storing processed information in memory on the server and using cached content in subsequent requests for the same resource.
• Logging and Diagnostics modules – Used to perform tasks related to logging and diagnostics in the request-processing pipeline, such as passing information and processing status to HTTP. sys for logging, reporting events, and tracking requests currently executing in worker processes.

IIS 7.5 includes the following additional or enhanced security features:

• Client certificate mapping
• IP security
• Request filtering
• URL authorization- Improved WebDAV and FTP modules as well as command-line administration in PowerShell

IIS 8.0 offers new features targeted at performance and easier administration. The new features are:

• Application Initialization – a feature that allows an administrator to configure certain applications to start automatically with server startup. This reduces the wait time experiences by users who access the site for the first time after a server reboot.
• Splash page during application initialization – the administrator can configure a splash page to be displayed to the site visitor during an application initialization.
• ASP.net 4.5 support – With IIS 8.0, ASP.net 4.5 is included by default, and IIS also offers several configuration options for running it side-by-side with ASP.net 3.5.
• Centralized SSL certificate support – a feature that makes managing certificates easier by allowing the administrator to store and access the certificates on a file share.
• Multicore scaling on NUMA hardware – IIS 8.0 provides several configuration options that optimize performance on systems that run NUMA, such as running several worker processes under one app-pool, using soft or hard affinity and more.
• WebSocket Protocol Support
• Server Name Indication (SNI) – SNI is an extension to Transport Layer Security, which allows binding of multiple websites with different hostnames to one IP address (similar to how Host Headers are used for non-SSL sites).
• Dynamic IP Address Restrictions – a feature that enables an administrator to dynamically block IPs or IP ranges that hit the server with a large number of requests
• CPU Throttling – a set of controls that allow the server administrator to control CPU usage by each application pool in order to optimize performance in a multi-tenant environment

• Idle worker-Process page-out – a function to suspend idle site to reduce the memory footprint of idle sites
• Dynamic Site Activation – a feature that registers listening queues only to sites that have received requests
• Enhanced Logging – a feature to allow collection of Server variables, request headers and response headers in the IIS logs
• ETW logging – an ETW provider which allows collecting real-time logs using various Event-tracing tool
• Automatic Certificate Rebind – a feature that detects when a site certificate has been renewed, and automatically rebinds the site to it.