Because of SSL's popularity, SSL acceleration is ubiquitous in security gateways: Even virtual-appliance vendors support hardware with SSL accelerator cards. XML acceleration is much rarer, with only Layer 7, Cisco, and IBM boxes including dedicated XML chips; IBM builds its own, Cisco and Layer 7 rely on Tarari. This is partly because of Intel's use of its Sarvega technology--Layer 7 believes that the hardware market will gradually transition to software--but mostly because there hasn't yet been much demand for application-layer acceleration.
XML acceleration is useful mostly in Web services that transfer relatively long XML documents, such as SOAP or SAML messages. It isn't used much in Web services designed to support browser-based applications, as these transfer relatively little data in each session, perhaps a single XML element or JSON object, wrapped up in TCP/IP and HTTP headers. Because JavaScript and Flash clients don't need to reload an entire page every time a user performs an action, most Web 2.0 applications involve less application-layer traffic than comparable apps built using static XHTML.
Still, rich Internet applications don't let Web servers off easy. While they may reduce XML traffic, RIAs can dramatically increase the number of HTTP connections that a server has to deal with. Instead of waiting for a user to click on a link, most RIAs run in real time, initiating new connections every few seconds. Servers overloaded by this can often benefit from SSL acceleration and other AFE techniques, including load-balancing and HTTP compression.
Photograph by Tim Flach/Stone/Getty Images
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WS-* Security Standards: Too Much Of A Good Thing?