Network Working Group Robert Kahn RFC-29 BBN 19 January 1970 This note is in response to Bill English's Request for Comments: 28. A "millisecond" clock should be satisfactory for most network measurements. Round-trip message transit times typically should be at least on the order of tens to hundreds of milliseconds. The IMP contains a 16-bit hardware clock which is incremented every 100 microseconds to allow for timing of internal events within the IMP, as for example, during tracing. However, most measurements are made using a 25.6 ms. software clock. DISTRIBUTION: A. Bhushan, MIT S. Carr. Utah G. Cole, SDS S. Crocker, UCLA K. Fry, MITRE J. Heafner, RAND B. Kahn, BBN T. O'Sullivan, Raytheon L. Roberts, ARPA P. Rovner, LL R. Stoughton, UCSB