SoftCell™ ATM and IMA

ImageStream developed its SoftCell™ ATM and IMA protocol components to offer a low-cost alternative to dedicated ATM hardware. Most T1 and E1 cards that support ATM and IMA use dedicated chipsets that perform specific ATM functions, such as packet segmentation and reassembly (SAR). These ATM chips are expensive, and they make it impossible to use an ATM card for anything but an ATM connection.

Fortunately, low-cost off-the-shelf CPUs have more than enough processing power to encode and decode ATM cells for multiple T1 or E1 circuits. By using the host CPU to process ATM cells, ImageStream reduces the cost of an ATM T1/E1 card by eliminating the expensive ATM chipset. And because there is no dedicated ATM hardware, it is also possible to run different protocols simultaneously on the same card. This means that instead of offering 4 and 8-port interface cards that can only run ATM, ImageStream can run SoftCell ATM and any other Layer 2 protocol on its standard 1, 2, 4 and 8-port T1/E1 cards. When compared to dedicated ATM hardware, ImageStream's SAND driver architecture with SoftCell protocol components make it possible to run any protocol on any port at any time.

With the widespread adoption of ATM for the provision of DSL and other broadband services, inverse multiplexing for ATM (IMA) has also become a popular networking technology. IMA makes it possible to bond multiple ATM T1 or E1 circuits together into a single logical connection that provides the combined bandwidth of the individual circuits. With the huge jump in cost and speed from T1/E1 to DS3/E3 circuits, and the high-bandwidth demands of broadband services, many network operators have chosen to adopt technologies like IMA that allow them to combine multiple T1/E1 circuits, and scale up bandwidth services until they reach a level where DS3/E3 circuits become more cost-effective.

ImageStream includes the SoftCell ATM and IMA protocol components with every ImageStream router. Extensive modifications to the Linux kernel were required to support the critical timing specifications for ATM and IMA, so SoftCell ATM and IMA are not available to customers who are building their own systems using stand-alone cards. However, OEMs can license SoftCell ATM and IMA in conjunction with the complete Enterprise Linux router distribution for use in commercial products.