1. Kochhar LexServe Pvt. Ltd.
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A considerate solution of IIS for trouble handling with Applications and Websites. By Manish Kumar Web Server Administrator Kochhar LexServe Pvt. Ltd.
TechEd 2002

2. Agenda IIS 6.0 – an overview Considerations Resources Q&A
Reliability – a new process model
Security
Performance and scalability
Improving manageability
Considerations
Resources
Q&A
TechEd 2002

3. Reliability A New Architecture for IIS 6.0 W3SVC
GOAL: permit complete application isolation from other Web applications and the core Web server
Web Service functionality in INETINFO split out to do this:
HTTP.sys: kernel mode listener and request router
W3SVC: now the configuration and process manager
W3Core: where Web applications are processed
Multiple W3Core DLLs loaded into W3WP.exe files
Two process model modes
[Default] worker process isolation mode
IIS 5.0 isolation mode
W3SVC
W3Core
Web
app
HTTP.SYS
kernel
TechEd 2002

4. Reliability A Reminder – Process Model for IIS 5.0
DLLHOST.exe
Pooled OOP Apps
INETINFO.exe
metabase
ftp, smtp, nntp
ASPNET_WP.exe
DLLHOST.exe
.Net App Domain
W3SVC
DLLHOST.exe
.Net App Domain
Isolated OOP App
.Net App Domain
DLLHOST.exe
Isolated OOP App
ASP.NET
In-proc
Apps
Isolated OOP App
ISAPI Filters
User mode
Kernel mode
Winsock
TechEd 2002

5. Reliability IIS 6.0 Worker Process Isolation Mode
Application Pool
Application Pool
Application Pool
INETINFO.exe
SVCHOST.exe
W3WP.exe
W3WP.exe
W3WP.exe
W3Core
metabase
W3SVC
W3Core
W3Core
ASP.net Apps
All Apps
(no OOP)
All Apps
(no OOP)
ftp, smtp, nntp
.Net App Domain
W3 Config Mgr
W3 Process Mgr
.Net App Domain
.Net App Domain
ISAPI Filters
ISAPI Filters
User mode
Kernel mode
HTTP.SYS
TechEd 2002

6. Reliability Application Pools
Can create one or more application pools
Each served by one or more W3WP.exe files
Each W3WP.exe serves only one pool
Requests routed directly to pool by HTTP.sys
Isolate applications based on:
Site/Customer
Functionality
Reliability
TechEd 2002

7. Reliability Periodic Process Recycling
What is it?
Periodically restart applications based on:
[Default] uptime
number of requests
Scheduled time
Memory consumption
On-demand
Why use it?
Refresh applications to ensure availability
Prevent bad applications from taking over the system
Effect on applications
In-process state or cache lost on recycle
Possible multi-instance issues
TechEd 2002

8. Reliability Self-Healing Architecture
Health check (pinging) - What is it?
Designed to detect W3WP.exe thread deadlock
Will engage if there are no threads in W3WP.exe available to respond in time
How does it work?
W3SVC will “ping” each W3WP.exe
Process has a configured time limit to respond
If (no response in time limit)
Default: kill process, publish event, and start new process
Or: can be configured to take a configured action on process => “Orphaning”
ASP and ASP.NET uses the ping to request a recycle if they are unhealthy
TechEd 2002

9. Reliability Crash Detection and Recovery
W3SVC detects W3WP.exe “crash”
W3SVC will start new W3WP.exe if there is demand
Requests queued in HTTP.sys while new W3WP started
Net effect: no Interruption in service
Rapid fail protection
Only allow x crashes in y minutes
Automatically stop pool if this value is exceeded – 503s to requests for this pool
TechEd 2002

10. Reliability Application Considerations
Design applications to be recycled
Persist state/caches external to host process
For ASP.NET, use External session state service or Microsoft® SQL Server™ to store state
Be aware of multi-instance issues
May be encountered during:
Recycles – overlap by default, but can disable overlap recycle or recycling altogether
Two application pools loading the same application code
If unable to change code, assign all URLs to the same pool
“IIS 5-isms” – dependencies on IIS 5.0 behaviors
Running as LocalSystem
Global data filters
If the above cannot be worked around, run IIS 6.0 in IIS 5.0 isolation mode
Loads W3Core into INETINFO, same IIS 5.0 OOP
TechEd 2002

11. Security on IIS 6.0 Secure on Installation
Clean installation
IIS not installed on a clean install by default
Use Configure Your Server Wizard to install application server role – installs:
IIS 6.0
FPSE (not enabled)
ASP.NET (not enabled)
Upgrade installation
W3SVC disabled unless URLScan is installed before upgrade
TechEd 2002

12. Security on IIS 6.0 Attack Surface Reduced
Restriction list
Only execute requests for “allowed” extensions and CGIs
No extensions or CGIs allowed by default
404.2 returned if request for “prohibited” extension or CGI
Use Web Service Extensions node in MMC to “allow” and “prohibit” extensions and CGIs
Known file extensions
Only serve requests that are defined in MIMEMAP
404.3 for requests not in MIMEMAP
Considerations
If using Visual Studio® .NET – define .tmp files in MIMEMAP
Visual Studio .NET to fix this in SP1
TechEd 2002

13. Security in IIS 6.0 Configurable Worker Process Identity
Worker process can be started as:
Network service (default)
Local system
Local service
Configured ID
IIS_WPG
New user group
IIS resources put into an ACL in this group
Will get 503s if configurable account is not part of IIS_WPG
Considerations
Passport Active Directory® mapping requires local system
Kerberos might require additional configuration for this ID
TechEd 2002

14. Security in IIS 6.0 Secure Changes from IIS 5.0
Sub authentication is not installed by default on clean installations
Effect = passwords might expire for IWAM and IUSR accounts
Solution = must install SubAuth or come up with own synchronization scheme
URLs restricted to maximum length of 16 KB with more restrictive parsing
No special chars, etc.
Content in Inetpub is now overwrite protected
Command-line tools limited to the administrators group only
TechEd 2002

15. Security in IIS 6.0 Recommendations
Do a clean installation vs. upgrade – more secure by default
No lockdown tool yet for IIS 6.0 to handle upgrade case
Run application pool W3WP.exe files as Network Service (default)
Only “allow” extensions that are vital to all applications
Prohibit everything else to reduce attack surface
Check IIS hit logs and HTTPERR log
IIS hit logs – substatus codes logged for W3C and binary-formatted files
HTTPERR – detail on reason for 503s and connection terminations
TechEd 2002

16. Performance in IIS 6.0 Caching Responses in HTTP.SYS
Cached dynamic content served straight from HTTP.SYS
Could run double speed when served from kernel – no user-mode transition
Your applications will not see requests if served from cache
Static files cached by default
Smart caching - only “hot” static content cached
Invalidation API callback
Also leverage “Expires” header to automatically set “staleness” timeout for cached responses
Considerations
Use for dynamic responses if they can be “stale” for a period of time
Lessens load on Web server if response from cache can be served
ASP.NET => use OutputCache Location=“Server” directive to mark response as cacheable
TechEd 2002 4

17. Performance in IIS 6.0 Capacity Planning Tracing
Hooks at key positions during request lifetime, from start of request to final send of response:
HTTP Start, Route, Cache Hit, End
ISAPI Filter Start/Stop (filter name, notification)
ISAPI Extension Start/Stop
ASP Start/Stop
ASP.net Start/Stop
Useful in debugging as well – Where is my request blocked?
Customer example
Uses this to find high CPU-usage pages
Also used to diagnose where the delay is
TechEd 2002 4

18. Performance in IIS 6.0 Web Gardens and Processor Affinity
Application Pool
Web Gardens
Application pool with more than one worker process
Connection-based routing within Garden
Processor affinitization
Bind application pool processes to one or more CPUs
Mask-based configuration
Considerations
Possible multi-instance issues
Recycling – possible all-at-once
Affinitization
Create virtual silos of work on large MP boxes
Affinitize based on MP architecture (bind to CPUs on same pod)
W3WP.exe
W3WP.exe
SVCHOST.exe
W3WP.exe
W3Core
W3Core
W3Core
W3SVC
All Apps
(no OOP)
All Apps
(no OOP)
All Apps
(no OOP)
W3 Config Mgr
W3 Process Mgr
ISAPI Filters
ISAPI Filters
ISAPI Filters
HTTP.SYS
kernel
TechEd 2002

19. Performance in IIS 6.0 Idle Timeout and Demand Start
Time out and shut down idle processes if process is idle for given period of time
Frees resources for active applications
Applications still available even if worker process idles out and is shutdown!
Demand start
Only start worker process if there is demand for the application pool
Considerations
Use idle timeout to free resources for other heavy-use applications
Consider disabling idle timeout if application startup takes a long time
Note: will cause idle processes to terminate
Loss of in-memory cache
TechEd 2002

20. Manageability in IIS 6.0 Metabase Improvements
XML Metabase
Metabase now stored in XML
Auto-versioning: like an automatic backup
Edit while running
Make changes directly to the Metabase.xml file while IIS is running
Any editor can be used – Notepad .NET, PERL, etc.
Considerations
Safer and more secure to use ADSI or UI to make changes to metabase
Note: Metabase.bin still exists, but only as a stub file for legacy backup applications
ADSI UI
Admin Base Objects
Metabase.xml
MBSchema.xml
TechEd 2002

21. Manageability in IIS 6.0 Metabase Improvements – Import/Export
Export/import metabase configuration to/from XML
Options include:
Export/Import inherited properties
Export/Import node only (or entire subtree)
Password-encrypted exported file
Use with ASP.NET XCOPY deployment of applications
Export IIS 6.0 metabase configuration for .NET application
Store in .NET application directory
Import application metabase configuration file after XCOPY
Admin Base Objects
ADSI UI
Metabase.xml
MBSchema.xml
TechEd 2002

22. Manageability in IIS 6.0 WMI Provider and New Command Line Tools
Query support
Associations
Scriptable
New command-line tools
Task-based approach
Supported tools – currently in %windir%\system32
Based on WMI Provider
Example: use IISCNFG.vbs as part of .NET application migration strategy between two IIS 6.0 boxes
Command Line Tools
ADSI
WMI UI
Admin Base Objects
Metabase.xml
MBSchema.xml
TechEd 2002

23. Summary IIS 6.0 was made better by making Web applications more:
Secure
Reliable
Scalable
Manageable
TechEd 2002

24. Resources IIS 6.0 Overview on TechNet: IIS 6.0 Technical Overview:
IIS 6.0 Technical Overview:
TechEd 2002

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