I am always on the lookout for increased performance in WebGIS applications, especially with 9.2.  Part of this search is an understanding of the basic components that I need to use to develop these applications.  I shared part of this at the last ESRI UC.

At the last ESRI User Conference, I gave a presentation on Developing Web Applications with ArcGIS Server .NET.  At the session, I had a few slides that discussed Best Practices one of which was to Understand the network.  More specifically, at most, browser uses 2 simultaneous connections per domain. 

Well, recently, we found more specifics on this in the form of a MS Article ID: 183110 published January 23, 2006.  In summary:

WinInet limits the number of simultaneous connections that it makes to a single HTTP server. If you exceed this limit, the requests block until one of the current connections has completed. This is by design and is in agreement with the HTTP specification and industry standards.

IE uses Wininet.  The HTTP 1.0 spec mandates 4 simultaneous connections while the HTTP 1.1 spec (RFC2616) mandates the two connection limit.

However, in this article it also documents how to override these default settings.  We (Rex Hansen and I) have recently tried this and found that by increasing the default connections to 5, we observed a noticeable performance increase, especially on load. 

NOTE: I do believe that there is a point of diminishing returns and I have not gone to that level of detail yet. Also, the MS Article warns not to do this in your everyday web surfing.

So, for all you WebGIS developers out there, try this out with 9.2 and let me know your findings.  As we do more, I will report it soon.

• Support for multiple Servers and Services - works with ArcGIS Server, ArcIMS, ArcWeb Services, OGC, and any other custom datasource that you care to implement using the new Datasource API.
• Support for multiple Datasources in the same view - yes, we now support adding data sources (i.e. Services) to the map and manage the drawing for you asyncronously.
• Support for .NET 2.0 and the new ASP.NET Parts framework
• IDE Integration with VS.NET 2005 (in addition to VS.NET 2003)
• A new Web Services publisher and framework - a new ASP.NET Handler framework written especially for ArcGIS System Web Services (*.agsx) - much faster than in 9.1
• No more image loading graphics
• All controls are AJAX enabled
• Game-style navigation
• Seamless pan support - Tiling, not enlarged images as some blogs speculated at the UC - all working thru AJAX.
• No more image loading graphics
• Map Tips Control
• A new navigation control
• ArcIMS AXL Object library - comprehensive support for ArcIMS Services in .NET.  This is not the ActiveX Connector... it is a completely new implementation written in C# with a clean object model.  Fully embraces ASP.NET.  I am really excited about this one.
• Did I mention - No more image loading graphics ( ok, I will keep that in there for backward compatibility, but by default, it will not be enabled ;)
• and more....

Hope this wets your appetite a bit, we have been working real hard on making this something that all of our users want to use.

I know that Brian and Rob are working hard on getting the EDN web site updated as we discussed at the .NET SIG - more on that later.  I agree with James Fee that there should not be any marketing videos on the EDN web site and I have spoken to Brian about this... I know he has a cool new video camera and is shooting some ad-hoc videos around campus - he even said he would video interview my team and get that up on EDN talking and showing off the new Web ADF and the cool new Multi-source Spatial Controls with AJAX support!  Still waiting on that one... Brian???

Oh, almost forgot, I have asked my team to start blogging and begin getting more information on using the Web ADF and ArcGIS with .NET in general.... hope to see more ESRI blogging real soon.