Network Allies Blog Network Appliances vs aTCA: Which Network Services Approach Should Your Company Deploy?

When building low latency messaging and other systems, designers inevitably reach for various combinations of general-purpose CPUs, network processors (NPUs), and switch fabrics.Indeed, the quest for performance often leads designers to automatically select Advanced Telecommunications Computing Architecture, or ATCA, a blade-based platform designed specifically for telecomms applications. But in many cases, to quote jazz pianist Thelonius Monk, they needn't. ATCA certainly has its benefits, but standard Network Appliances often can do more in less space and at reduced cost.Take the issue of latency and bandwidth, for instance - how long it takes a single bit to traverse a system and the total number of bits the system can move each second. In ATCA, both latency and bandwidth are largely determined by the constraints of the particular interconnections existing between boards connected through the backplane. As the number of on-board processors increases, to help boost bandwidth, so does the need for local switches, which only add to the latency of each packet.Not so in a Network Appliance. There, multiple processors are connected by a switch on the same board. Fewer switches, lower latency.Expandability, Power, CoolingWith its chassis able to accept new node cards, ATCA is quite expandable, but only at a cost. Unused chassis space wastes space and cost, and as boards get added and moved, designers must plan carefully to make sure each board, consuming as much as 300 watts, gets the power and cooling it needs. A Network Appliance, however, is a self-contained unit, and expansion is simply a matter of linking appliances over an interconnect such as Ethernet or Infiniband - perfect, it seems, for low-latency messaging.Product Life CycleWhile the relatively long, 7 to 10-year life cycle of ATCA boards may seem like an advantage, it may actually weaken a design. Over time, the system may be unable to accommodate newer, more powerful components simply because they cannot meet the same long life cycle requirement. Designs using Network Appliances, however, can be architected to be more or less "evergreen" depending on requirements.CPU and I/O DensityATCA boards may be hot-swappable, but only by incurring significant overhead: Every board duplicates power and IPMC circuitry, which severely limits the space left for processors and I/O connections. Network Appliances offer considerably more front- and rear-panel space for I/O and potentially much greater board area for processors.InteroperabilityEven with many standards in place, the fact that ATCA systems are typically sourced from multiple vendors puts a burden on designers. Appliances, though, are by definition single-sourced and thus cause fewer headaches. Cost ATCA designs are notoriously expensive, for they are rife with "overhead" - components like intelligent fans that don't contribute directly to performance. What's more, ATCA generally incurs the cost of integrating components from multiple vendors. In contrast, every Network Appliance is pre-integrated. In sum, while ATCA may be appropriate for certain high-end applications, including low latency messaging, the Network Appliance is more often the right choice.