Selection of a Rate Adaptation Scheme for Network Hardware

Rate adaptation is a family of technologies driven by the expectation that large energy savings can be achieved in packet networks by dynamically adjusting the capacity of network components to the load that they are required to sustain. Depending on the scope of their application, whether at the network, system, or circuit-pack level, specific instances of the rate adaptation concept differ widely by their timescale of operation. In this paper we focus on packet-timescale rate adaptation (PTRA) techniques, which apply to individual traffic processing chips in the circuit packs of network systems. We look at the field of available options for PTRA implementation, whose behavior has been so far well characterized only in single-device applications, and compare their performance in realistic multidevice configurations. We find that the sleep-state-exploitation (SSE) scheme, which only adds a sleep state to the ordinary fullcapacity state, offers the best compromise between energy savings and the packet delay degradation that PTRA unavoidably introduces. Our results indicate that the key technological enabler for the widespread adoption of PTRA will be the availability of SSE devices with a very-low-power sleep state and state transition time well shorter than one millisecond.