"TCP has very little trust," says Mark Butler, director of Product Marketing. "It takes its legacy from the telco world. They are very concerned about getting information from point A to point B -- performance is an afterthought. It starts slow and is very cautious. It wants to get an 'ack' back, and then slowly ramp up to deliver data. What we're saying is that's not the operating scenario you should be in, in terms of enhancing performance with applications."
This is particularly important in the case of heavy traffic applications, Butler says. For example, one of the company's users sends satellite imagery to its client in real time and is not currently hitting its metrics; similarly, another user has problems delivering medical imagery to doctors' laptops, he says. In a different example, a SaaS vendor user is having trouble with a web-based expense tracking application because the pages take too long to load for its European clients. "Their other option is to build a data center in Europe, and they don't want to take on that investment," Butler says. Internap refers to this capability as expanding the geographic reach of applications, because the data can travel a longer distance in the same time and still maintain acceptable performance.
The service is based on several existing Internap technologies and services, such as its Performance IP service and Managed Internet Route Optimizer technology, which acts as a front end to up to ten carriers and dynamically routes data to whichever carrier offers the best performance, based not just on availability but also on factors such as congestion and latency, Butler says. Examples of ways in which XIP accelerates TCP include improving recovery time after packet loss is detected, and enabling it to transmit more data at a continuously faster rate by opening a wider data receiving "window" at the client side. "That overrides TCP's desire to have a slow start," Butler explains. The result is applications performance that is typically two to four times faster than with TCP, he says.
No client-side software is required, meaning users can take advantage of the service wherever they are, Butler says. "If you're with an organization with lots of 'road warriors,' you're no longer as concerned about where they are," he says. The acceleration is one-way, from application to client, meaning it is best suited for applications that send a great deal of data to the client. The service is expected to be available in the second quarter for an undisclosed price.