A time service in a distributed system may be used both for multiprocess synchronization and for simply finding out what time it is. For synchronization, the time provided by di#erent servers should be closely synchronized. For telling time, the time provided by each server should be a close

This memo describes the Network Time Protocol (NTP) designed to distribute time information in a large, diverse internet system operating at speeds from mundane to lightwave. It uses a returnabletime architecture in which a distributed subnet of time servers operating in a self

frequency plots and ‘energy dot plots’, are available for the folding of single sequences. A variety of ‘bulk ’ servers give less information,but in a shorter time and for up to hundreds of sequences at once. The portal for the mfold web server is

to lightwave. It uses a returnable-time design in which a distributed subnet of time servers operating in a selforganizing, hierarchical-master-slave configuration synchronizes local clocks within the subnet and to national time standards via wire or radio. The servers can also redistribute reference time via

are used in this study: three from academic environments, two from scientific research organizations, and one from a commercial Internet provider. These data sets represent three different orders of magnitude in server activity, and two different orders of magnitude in time duration, ranging from one week

the Chord location protocol, which operates in time logarithmic in the number of servers. CFS is implemented using the SFS file system toolkit and runs on Linux, OpenBSD, and FreeBSD. Experience on a globally deployed prototype shows that CFS delivers data to clients as fast as FTP. Controlled tests show

, does not provide the mechanisms for building the servers which ensure predictable services. Therefore, if real-time applications which have rigid timing constraints access the servers, they will fail to meet deadlines. Real-Time Mach provides a set of mechanisms and policies for implementing real-time

Bigtable is a distributed storage system for managing structured data that is designed to scale to a very large size: petabytes of data across thousands of commodity servers. Many projects at Google store data in Bigtable, including web indexing, Google Earth, and Google Finance. These applications

of magnitude under concurrent load. These measurements indicate that hierarchy does not measurably increase access latency. Our software can also be configured as a Web-server accelerator; we present data that our httpd-accelerator is ten times faster than Netscape's Netsite and NCSA 1.4 servers. Finally

-riding are in place. We demonstrate through simulations of scenarios of practical interest that the expected file download time improves by more than 20-30 % with network coding compared to coding at the server only and, by more than 2-3 times compared to sending unencoded information. Moreover, we show that network