Siva's IIS Blog

IIS Memory Management (Part 3)

2008-04-11T13:59:00Z

…am back again to write about the way Application Logic functions in the Application Services Layer Middle-Tier in a 3-Tier Architecture. J

Role of IIS in Application Layer and IIS 6.0 Architecture - An overview...

My previous blog was about the 3-Tier Architecture in a brief thought process. My vision now is to let you know specifically the role of IIS in the Application Layer (the middle-tier). In simple words, IIS plays the role as a medium between the User Interface and the Application Logic which in-turn redirects the client requests to the concerned application service that resides on the application server. But, was that actually “in simple words”?? ...I guess not..!! J …

Let me try to be more precise to detail about the role of IIS in Application Layer and share a simple diagram (a rough paint of mine)… J

Time to recollect the 3-tier architecture discussed in my prev blog and to relate it with the diagram above (and ofcourse, my imaginary domain name (techdumbo.com))... :-)

Typically, to relate on a practical note, you may consider that an end-user is keying in the URL (http://www.techdumbo.com) in his browser window (Internet Explorer). User level forms / the default pages on that website get processed immediately in the Presentation Layer. He is then displayed with a series of forms where-in he could select the kind of data he requires. He selects the data criteria and submits the form. This request is then processed through ASP pages to (black arrow) the Business Logic. Application Service in this layer now analyzes the data criteria selected by the end-user, processes it to the Data Layer using the connection providers, specifically to the SQL Database Engine. Data Layer then verifies / authenticates / validates the criteria and sends back the data to (white arrow) the Presentation Layer.

So… here is the key!! How the application specific ASPX pages are are displayed in end-users browser window? As soon the user key-in http://www.techdumbo.com, the DNS client service is initiated and the client request to this URL is redirected to the DNS server in that particular client site. DNS server then checks for the domain name techdumbo.com and find appropriate host record matching www.techdumbo.com, fetch the related IP address to that host record, and forward the client request to the Web Server that holds the same IP address. This Web Server is nothing but an Application Server with Windows 2003, IIS component and the Application Service installed and configured in it. Thus, the client browser fetches the Default Document from the Web Server.

Default Document?? …now… what does it mean in IIS context? Maybe it still needs clarity for beginners. Fine! Logon to the IIS console (start – run – inetmgr.exe), then right-click on the Default Web Site properties, go to Documents tab. Here is what we map the website URL to a default document that an administrator could add manually, which usually becomes default.aspx / index.aspx / or so on… depends on the Application Development process. By configuring default.aspx as the default document in this tab for instance, when an end-user hits the URL http://www.techdumbo.com, in-turn the IIS server sends him the default.aspx to the client browser, that is, Internet Explorer window. Hope this helps! J

This process is just fine and we understand how IIS helps an end-user as an interface component to serve the web pages being in Application Layer. However, it is a must to understand the concept of Application Pool in IIS 6.0. Yes! It is time to write about IIS 6.0 Architecture. J

IIS 6.0 Architecture – An overview…

The basic difference between IIS 5.0 and IIS 6.0 lies primarily on the way application service is isolated from IIS services. IIS 6.0 is based on the concept of Worker Process mode for Application Isolation. When I say Worker Process, you could imagine a process named w3wp.exe in Task Manager that could be noticed on the same IIS server box configured in IIS 6.0 Worker Process mode. This is nothing but an IIS Application Pool process which takes accountability on executing the Application Logic scripts on the IIS Server. To recollect precisely, we still can have multiple websites created on the same IIS 6.0 console. This means, each website can be mapped to a specific application pool on the IIS console. To help you understand better, go to start – run – inetmgr.exe. Here in the IIS console, you will find Default Web Site listed automatically. And, you will also find Default Application Pool listed just above the website hive. Right-click on the Default Web Site and click on Properties. Here in Home Directory tab, you will find that the website is mapped to Default App Pool.

This way, the application (documents that you might find in the path specified in home directory tab) which is configured to execute on this specific website will be using Default App Pool. In-turn, we can be more specific by stating that the application uses the memory space as utilized by the w3wp.exe process in Windows. As many application pools you create, that many w3wp.exe is found in Task Manager, which again means, that many Isolated Memory Space is created for each application hosted on the same IIS 6.0 web server.

However, you should also remember that the term Isolation does not mean isolating just the applications hosted on the IIS server. The key point here is about isolating the applications from IIS services. Yes! IIS Service primarily runs on inetinfo.exe (this could also be found in the Task Manager). This service takes effect as soon as the IIS Admin Service is started in services.msc, which initiates the metabase configuration to be effective on the current IIS component installation.

Metabase? Now, what does this mean? In simple terms, this is just like how Registry acts for Windows OS; Metabase acts for IIS component in Windows OS. IIS uses the metabase as soon as the IIS Admin Service is initialized and sets the configuration accordingly as specified in the metabase. In IIS 6.0, you will be able to find the metabase in %systemroot%\System32\Inetsrv\Metabase.xml.

Having said about metabase, you could imagine the importance of inetinfo.exe process which handles the IIS Admin Service / SMTP / FTP / NNTP. If Inetinfo.exe crashes, then it impacts on all these services too. To prevent and secure this specific process from sharing memory space with w3wp.exe (the application pool), IIS 6.0, by design, uses the Application Pool technology and segregates the applications hosted from IIS services. Hence, if there is an impact due to any reason against w3wp.exe in IIS 6.0, it affects ONLY that specific application hosted on the IIS web server, whereas, the other applications which are hosted and using other w3wp.exe processes and inetinfo.exe process continue to be with the same functionality. This can be simplified by the term IIS Isolation Mode. Hope this helps you to understand the concept better! J

With this explanation in mind, take a look at the diagrammatic representation as shared by the Microsoft Technet team and do refer to the technet link for an in-depth details on IIS 6.0 Architecture:

Reference: http://www.microsoft.com/technet/prodtechnol/WindowsServer2003/Library/IIS/93ddbb51-5826-4ebd-a434-24c5fd103d3a.mspx?mfr=true

...but, is there any other mode that IIS 6.0 supports? Yes! It is IIS 5.0 Isolation Mode. This mode is used in-order to provide compatible platform for those scripts which are still dependent on IIS 5.0 design. This feature is more about providing backward compatibility to those scripts / applications which still depends on IIS 5.0 architecture. However, when we tend to migrate to the latest version of IIS, we always can count on to avail the best of its feature, that is, IIS Application Isolation Worker Process Mode. You could find this option by right-clicking on the root hive in IIS 6.0 console and click on Properties.

I believe this info to be sufficient for the time being. Let me share more about the design behind these processes to execute in User Mode and Kernel Mode Memory space, more specifically, what exactly do we mean by User Mode and Kernel Mode memory space and how these are related to the applications hosted on a web server with the physical memory configured on the server hardware?...in my successive blogs. J

As always… should you have a thought to share, pls click here. :-)

Cheers,

Siva

Netmon Trace & HTTP Requests

2008-03-27T15:47:00Z

While browsing on the technet portal for details on Netmon drivers for Vista, happened to visit a blog about Netmon and HTTP Request analysis. I would definitely call it an impressive blog which gets in-depth on how to analyze HTTP requests and packets using Netmon.

It has always been a challenge when we end-up using packet tracing / capturing / analyzing tools. With an appropriate guide on how to use such a tool considering our requirement as a specific criteria, we would surely make a great difference in the results.

For such a thought, I suggest you to visit this blog. Pls keep in mind that the blog contains info specifically on NETMON usage for HTTP packets:

Click here to visit the original blog on Technet – “Understanding HTTP Flow with Netmon 3”

I guess this is a must read for those administrators who spend a good time on webserver packet analysis!!

Have a happy tracing!! J

Cheers,

Siva

IIS Memory Management (Part 2)

2008-03-27T13:24:00Z

Hello everybody, I am back again to continue blogging on this topic; IIS Memory Management and this time, it is about In-Process & Out-Process Application Mode in IIS & 3-Tier Architecture in Web Application Services. Yes, it is indeed important to understand the varied application modes in IIS and how it is related in 3-Tier Web Application Architecture, before we get into the actual Memory Management scenarios. :-)

As always, here we go with My Thoughts:

Application Mode:

IIS can be tuned in such-a-way that the application running on a webserver, could share the User Mode Memory space of the IIS service components. And, this configuration, which can be customized by an administrator on the IIS admin console, results as the Application Mode configured currently on that specific webserver; either In-Process or Out-Process. More specifically, you will find Application Mode configuration in the Home Directory tab of the website properties on the IIS Admin Console (inetmgr.exe)...

Did this explanation help you to understand the exact meaning of IIS Application Mode? Hmm.. I guess not! :-( ...what is lagging behind in this definition? I am pretty sure that the explanation is valid. As a beginner, I would immediately think of certain questions raised in my mind from that of the above detail as listed below:

What is an Application?
Is IIS not an Application?
When user is browsing a website, is it not the IIS as an application serving their requests?
what is User Mode Memory?
what is Kernel Mode Memory?
What is In-Process?
What is Out-Process?
If my server has 4 GB of RAM, the physical memory, it is the Operating System which deals on the processes and the memory allocation for each process. So, why would IIS come into picture on the memory utilization?
Where exactly does this "application mode" helps in IIS Memory Management?

... Okay.. enough for now!! :-) ...

Let me now try to answer these thoughtful queries and help you understand the definition better.

Source: http://technet.microsoft.com/en-us/library/bb727121.aspx

Reference: http://microsoft.apress.com/index.php?id=50

In a typical scenario, we have in most cases, three-tier architecture lay on the scope of any project design; the Presentation Layer which deals with the User Interface components, the Business Logic which deals with the Application & Webserver Components and the Data Layer which holds the actual data, typically on a database server.

This application server and IIS service (usually hosted on the same server hardware, depending on the load / traffic analysis, we also tend to split the design by having a separate server for IIS and the application) takes the user input from a client browser, sends the query data to the application server, and the application then establishes connectivity to the customer database, which is a database server, fetches the records, again returns the output on the client browser.

Still not clear about the above explanation…??? Okay, here we go with a bit in-depth… :-)

I believe it is for sure, going to be easy to understand this concept with a simple instance. Let us now think about a scenario as such, a list of Customer Contact Information, stored centrally in an organization and that can be retrieved from anywhere across the globe by the sales team. As soon an employee visits, http://www.myURL.com/cust-contact.aspx website, we must think as what exactly happens and how the data is processed?

Presentation Layer (User Services):

Initially, the client browser locates (forget about DNS resolution for now, let us focus on IIS) the webserver which holds the ASPX pages. These client-side ASPX pages (cust-contact.aspx) will load client components and display a form to enter the criteria to search the entire customer database. User selects a Customer ID and clicks on Search. With this, we move on to the Business Logic (Application Layer) which is the Middle-Tier.

Application Layer (Business Services):

Based on the user input, the specific Customer ID, is the data which now Business Logic would be interested more about. To process the data to the data layer, the application server components might use a technology like, DAO / ADO / OLE DB, based on the product requirements and design, and establishes connectivity to the database server. Once the datasource is connected to the data access layer successfully, it then submits the query statements based on the programming modules from the application logic to customer database. The records are then retrieved from the customer database and again displayed on the client browser using HTTP port. Ofcourse, TCP ports might differ on the connectivity from Application Layer to the Data Layer. Whereas, between the client browser and the application web interface, most of the process takes place using HTTP modules, again, this process is totally based on the project requirements.

Data Access Layer (Data Services):

This initiates a process as soon the application logic starts the programming modules to establish connectivity with the customer database. It verifies the connection provider, the user / group authentication parameters, network path, database server instance and the database name. Once it confirms all these information, will then take the code submitted by the application layer which includes the user input (customer ID), and fetches the records from the customer database. Data is then returned to the Application Logic, which in-turn processes the data to the client browser.

Well, this concept about 3-tier architecture is fine! But, where do we get IIS as a stand-point on the entirety? Precisely, what is the role of IIS here in the above scenario?

Fine, let me now get into the specifics of IIS in the above scenario:

The Windows Server OS with IIS component installed in it, which stores all the ASPX pages can be termed as a Webserver. IIS plays an important role as part of Business Logic (Application Layer) by providing a virtual path for users to browse the ASPX pages hosted on the Application Server. IIS is the webserver, which is part of the Application Layer, where-in we create a website (or, maybe the Default Web Site) in IIS admin console. Once created, we copy all the related ASPX pages (that includes the programming module of the application logic) to the path, that is shown in Home Directory tab of the website properties in IIS admin console (incase if it happens to be the Default Web Site, then the path by design in any IIS installation is C:\Inetpub\WWWRoot).

Again, on the same Application Layer, the source code modules which processes and establishes connectivity with the data layer, processes the client requests to the database and fetches the records from the database to the client browser, can be termed as the Application hosted on the webserver (in some cases, you might even find certain application related executable images (.exe files) in task manager which are part of the actual Application Logic by itself.

All these transaction happens on HTTP port, which means, the TCP Port 80 used by IIS to host a website by default. While browsing the website on a client browser, on the same client machine, when you execute netstat –a (or) netstat –n command using cmd.exe, you will find that your client IP (local IP) is using PORT 80 to connect to the remote website (foreign address). This TCP Port can be customized / changed based on the requirements from the Security Team in an organization, during the project design phase.

Thus, IIS and the term Application differ in the Application Layer.

Hope this abstract gives a practical note on IIS as a webserver! We started off with In-Process & Out-Process Application Modes and have come a long way till this level of understanding varied layers on a Web Services Architecture. It is always a suggestive approach to gain knowledge on the above concept, before we dig into the actuals of Application Modes, as such, these are unswervingly inter-related.

Well, I suggest now to wait for my next blog to know more about the way IIS and Application Logic functions in the Application Services Layer (Middle-Tier) in a 3-Tier Architecture.

Should you have a thought to share, pls click here. :-)

Cheers,

Siva

IIS Memory Management (Part 1)

2008-03-27T13:14:00Z

My thoughts:

Here we go, with a simple terminology Memory Management. Is it something simple in reality? I guess not! (which is why, I have segregated this topic into multiple blog posts) Memory Management in any product has its own significant approach on handling process threads and client requests. Process Threads? Okay!! Let us not deviate to System Internals for now! :-) ...

...instead, allow me to rephrase it as IIS as a webserver has its own method of handling client requests! When we say Client Requests, it could mean a lot, such as, the load on the server, total number of sessions, total number of visits / pageviews, and so on! However, this area of Memory Management gets maximum importance as soon we think about dynamic websites.

Now, what is a dynamic website? Well, answer is not just "Websites with dynamic web content!". :-) ... On a practical note, a dynamic website is one which has an effectual usage of the server memory space, while serving client requests to fetch or process a data, (which in most cases designed as a third normal form; resulting in primary key - foreign key database architecture) based on the criteria opted by the end-user. In such a situation, to trigger this kind of data manipulation / processing / transaction that occurs on the server memory space, we use programming languages like ASP.NET.

This results in creating dynamic webpages where-in the webserver takes the complete load on an end-to-end scenario, which again means, memory utilization on the IIS processes, that is, inetinfo.exe / mtx.exe (IIS 4.0) / dllhost.exe (IIS 5.0) / w3wp.exe (IIS 6.0), as I have shared in my blog about IIS Version Comparison. This design on its entirety shall be termed as a dynamic website.

Hope you find this blog a good start on IIS Memory Management!

You may click here to find additional reference on this topic.

Watch out for my next blog - IIS Memory Management (Part 2) ... :-)

Cheers,

Siva

IIS Version Comparison & Architecture

2008-03-27T10:01:00Z

IIS Version Comparison - An Overview:

We often tend to think specifically about a new feature in a product, as an enhancement against a new version released. Do you think if that is all about releasing a new version? Not really! Well, it is a must to think about feature and also the architecture with design-level changes, with variations on the product-specific system files, which would have been incorporated in the new version.

As many of us are aware of, IIS (Internet Information Service) indeed has come out with a drastic change in the way of handling applications conceptually and practically through In-Process and Out-Process technology.

BTW, What exactly do you mean by In-Process and Out-Process applications? To know about this concept with an in-depth architectural overview, please wait for my successive posts.

For now, I suggest you to take a look at the comparison chart on various IIS versions shared by Microsoft Technet team, which gives you a high-level data on various versions of IIS and their feature specifications.

What I have shared above is just a screenshot of the chart. You may additionally refer to the source link I have mentioned below to gain a copy of the comparison chart from Technet and document it in your process on a need basis. That was to gather an elevated detail about the varied versions and their features, which in-turn, mapped to the terminologies that would be used from this posting onwards. Did not include IIS 7.0 in this comparison analysis, as I have planned to go with dedicated blogs on IIS 7.0. :-)

You may click here to view the content source for this blog and the IIS Comparison Chart.

IIS 4.0 Architecture - An Overview:

Anyone still using IIS 4.0?? Doubt it!? Well, it is all about end-to-end product knowledge. Nothing wrong to know the basics of some technology. :-) ... Hence, let me now share some notes about IIS 4.0 to understand the basic design, which will help us gradually to discuss further about the consecutive releases of IIS product till IIS 7.0.

My thoughts:

Again, I am gonna pick out the source information from Technet - which is indeed a great place to gather technical information. To speak about IIS architecture, we must first need to know the version stand-point. Though we have IIS 2.0, 3.0 - let me start with IIS 4.0 and touchbase on IIS 7.0, being honest with you, my basic knowledge span over from IIS 4.0. :-)

IIS 4.0:

Well, here is something very little which I would like to share on this version of IIS. It is confined to 32 BIT Architecture Model (did we have 64 BIT those days!?) and the Application Isolation Mode was mapped to MTX.EXE. Which means, your application mode, when configured as Out-Process Isolation, the User Mode Memory will be allocated on the executable image MTX.EXE. Whereas, the same MTX.EXE will not be in picture at all, in-case if you go by configuring your application as an In-Process Isolation Mode. In such a situation, the application memory will be sharing the memory space with Inetinfo.exe, which is the back-end process for executing IIS Admin Service. If you refer to IIS 5.0 Architecture (an upcoming blog of mine), I guess you will then be able to visualize on MTX.EXE as compared with DLLHOST.EXE. Ofcourse, many other feature enhancements have been made on IIS 5.0! :-)

For beginners: You will be able to find inetinfo.exe in Start -> Run -> Services.msc -> Properties of IIS Admin Service. If IIS is successfully installed and configured on a Windows OS, you will also find inetinfo.exe as a process in Task Manager of that webserver.

Wanna know more about these terminologies; Out-Process Isolation Mode / In-Process Isolation Mode / User Mode / Kernel Mode Memory Space / IIS 5.0 / IIS 6.0 Architecture?

Suggest you to wait for my next blog on this topic - IIS Memory Management...

Got a thought to share on this aspect? Pls click here... :-)

Cheers,

Siva