Bridging the Software/Hardware Forwarding Divide

As network speeds increase, and network requirements diversify, networking hardware vendors are being pressed on two distinct fronts. To remain competitive, they must continually improve their cost/performance ratio at a pace faster than Moore’s Law. Over the past fifteen years, enterprise network speeds have increased by three orders of magnitude, from 10Mbps to 10Gbps, requiring that the cost of a unit of bandwidth (a gigabit port, or Gport) drop precipitously. At the same time, networks are expected to address myriad application, management and security requirements that were unheard of fifteen years ago, creating pressure to develop network forwarding devices that can flexibly accommodate these new demands as they arise. This trend is reflected in the many “open” platform initiatives launched by system vendors [10, 16, 22]. Despite significant research and engineering efforts, the industry has failed to simultaneously achieve low cost/performance and high flexibility.1 There are three basic approaches to building network forwarding devices currently pursued in the field and, as we relate below, they offer quite different tradeoffs between these two goals. In the commercial world, where cost concerns dominate, the most prevalent approach to building network forwarding devices (this includes both switches and routers, but hereafter we will use the term “switch” as shorthand) involves embedding the basic forwarding logic in ASICs. There are commodity forwarding chips (from, for example, Broadcom, Marvell, and Fulcrum) that cost as little as $20/10Gport, a pricepoint that would have been unthinkable only a few years ago. Multi-layer switches using these commodity chips support 240Gbps (24x10Gbps) of capacity for under $100/10Gport, and 640Gbps (64x10Gbps) chipsets will be generally available this year which should lower the cost even further. However, one cannot modify the hardware forwarding algorithm without respinning the chip. This forces packet forwarding to evolve on hardware