I live in a world of end user experience management.  The SLA’s I have in place with my customers are quantified in milliseconds, and as such we employ a strategy known as edge acceleration.  Edge acceleration can mean different things to different people, but those who have a SaaS (Software as a Service) model treat the “edge” as the network physically closest to the end user and the “origin” is where the application(s) is hosted.

For web-based applications, the following almost always happens (regardless of industry, form, or function):

Steps (necessarily very high-level)
1) user pulls up some hostname (app.company.com) in a browser
2) user sees a page, usually a login page, accompanied with text and images
3) user logs in and proceeds to use the application in any number of ways

Since these three steps are effectively universal in SaaS, it is worth our while to analyze these steps in an effort to increase the accessibility of these things from the edge.

Analysis
1) An end user typing a hostname into the address bar of his browser and clicking “go” triggers a number of events.  First, the hostname typed in needs to be resolved to an IP address via DNS.  Once the IP is known, our end user connects to the IP requested, and issues HTTP GET’s based on the server response (HTML).

Leveraging an edge DNS service, such as Akamai’s eDNS service, will ensure that a nameserver most accessible to the end user will pick up the request and respond.  This is theoretically faster than having ns1.company.com hosted in Silicon Valley with end users in New York.  With eDNS, users in New York will have their requests answered by servers which are usually physically much closer, and therefore faster.

2) An end user downloading and rendering the login page of a web-based application is probably the easiest part to deal with.  Since there’s nothing user-specific at this point generally object here are statically cacheable.

Leveraging an edge HTTP content delivery service, such as Akamai’s EdgeSuite service, tries to make sure the end user will be downloading this static content from a webserver cache somewhere closer than the origin.  Static content here typically includes JavaScript, JPG, GIF, PNG, CSS, and text.  Edge delivery services also tend to add gzip compression to these files, reducing data transfer and speed to transfer.  Files are cached for some configurable time and new files are retrieved from origin by the edge servers when an end user makes a request.

This is a well-understood problem and solution, and most CDN’s in existence today basically provide this as a baseline service.

3)  Once a user types in their identifying information and clicks login is where the complexity gets introduced.  Usually when a user clicks the login button, there’s a database lookup to validate user-supplied credentials, a session is instantiated for the user, amongst other things.  In either case, these server-side events require end user interaction with the origin and the edge delivery model above simply cannot handle it.  For this, a new trend in CDN technology has developed in the form of dynamic application acceleration.  Akamai’s service in this arena is called Web Application Accelerator (WAA) and utilizes their SureRoute technology to pass end user traffic back to origin and vice versa.  In theory, WAA bypasses the BGP that most providers use by maintaining their own (more optimized) route tables, thereby decreasing the latency an end user experiences.

Since this is a relatively new challenge to address en masse, it’s understandable that Akamai’s solution leaves a lot to be desired.  However, their service is significantly faster for almost any type of application, and smaller companies simply don’t have the expertise or funds to build their own application acceleration infrastructure.  The major online retailers and MMOG operators figured this out years ago and have been building out their own infrastructure, but the cost-prohibitive nature of these undertakings is a large obstacle to overcome.

Interesting note:  there have been more and more companies competing in the application acceleration space with packaged solutions but I think we’re still a bit aways from having your average medium-sized SaaS company deploy these things.

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