The Impact of a Zero-Scan Internet Checksumming Mechanism

This paper describes a "zero-scan" mechanism that reduces Internet checksumming overhead from a per-byte scan (or copy) cost, to a small and constant per-message cost. Unlike previous techniques, this mechanism requires no message buffering within the source. This will allow Internet transport protocols to achieve transfer latencies comparable to specialized protocols implemented directly on high-speed LAN (link-layer) services. In addition, this mechanism is transparent to systems outside of the source LAN. Hence, this mechanism affords applications the portability of Internet protocols without sacrificing the high performance of specialized LAN transport protocols. The proposed zero-scan checksumming scheme eliminates the last requirement for an additional data copy/scan, beyond the scan required to transmit or receive from the network channel. If this checksumming mechanism is combined with zero-copy operating system mechanisms that provide low-overhead transfer across application a..