Date Added: Jan 2010
Backbone routers typically require large buffers to hold packets during congestion. A thumb rule is to provide a buffer at every link, equal to the product of the round trip time and the link capacity. This translates into Gigabytes of buffers operating at line rate at every link. Such a size and rate necessitates the use of SDRAM with bandwidth of, for example, 80 Gbps for link speed of 40 Gbps. With speedup in the switch fabrics used in most routers, the bandwidth requirement of the buffer increases further. While multiple SDRAM devices can be used in parallel to achieve high bandwidth and storage capacity, a wide logical data bus composed of these devices results in suboptimal performance for arbitrarily sized packets.