XML and the AJAX Model
One the requirements listed in the original XML specification was that it be simple and capable of combination with other technologies. One technology getting significant attention recently is Ajax or Asynchronous JavaScript and XML, a web development technique for creating interactive, responsive web applications. Technically, Ajax does not require the use of either JavaScript or XML although these two technologies are most commonly associated with the asynchronous nature of Ajax web interactions.
To understand how Ajax is impacting network planners it's helpful to compare the traditional web client server model with Ajax.
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Figure 2. With AJAX (Asynchronous Javascript and XML) browser server communication is not directly associated with a users web requests.
As illustrated in Figure 2, with the conventional web, the web browser and server interact in a request response model. A user's browser click results in a request to a server, which in turns delivers a new web page. In the Ajax model, the browser through the use of JavaScript, can initiate communication with the server asynchronously and independently of user input. Google Maps, for example, is a web application designed according to the Ajax model where map segments that surround the current display are fetched independently of user movement. Scroll right across your map and the underlying JavaScript will generate multiple server requests trying to anticipate where you will be looking next.
While users find GoogleMaps quick and responsive, network planners see a potential barrage of packets heading back to their servers from a single web request. Because the creation of asynchronous communication back to the server has the potential to generate compelling, responsive web applications, it looks to be just a matter of time before more developers latch on to the technique. For organizations that take the idea of application network seriously, expect to see guidelines and constraints on the use of the Ajax related technologies. For organizations that don't understand the increasingly important connection between networks and applications, expect to see servers come crashing down at the hands of their own developers inadvertently generating their own denial of service attacks via Ajax web requests.
Overall, my foray into Interop 2005 gave me new insights into how XML's success is impacting the world of networking and how what occurs at the application level impacts the network in a variety of ways. For some of the challenges associated with XML processing, hardware-based solutions go a long way toward alleviating the pressure on servers to parse, extract and route XML traffic. But the challenges associated with the increased bandwidth have fewer ready made solutions and when coupled with the explosion of asynchronous XML traffic generated by Ajax styled web applications, create enough challenges to keep network managers from getting a good night's sleep.