Resources for Collaborative Experiments
We participate in many network experiments with our international partners in several countries. Some of these involve ongoing network performance evaluation and measurements with sites all over the world, others have specific goals and designated experiment plans. To support these experiments, we make available workstation and network resources to outside investigators. Some idea of the resources we can provide can be found in the Internet Research Laboratory page.
Software and Documentation Resources
Following is a hodgepodge of programs and other resources which may be helpful for adventuring in computer network time synchronization. Note that all software and documentation are now retrieved directly from the web. the security requirements of our campus FTP server preclude access from many places in the Internet. If you have no web access but do have FTP access, try our server at ftp.udel.edu and surf the pub/ntp directory.
Many of the links reveal directories which require you to make a selection among several sequential releases of a software package. In these cases, you are advised to use the latest version; but, if something wicked happens, back up to a previous version. In the case of software distributions, we have stashed both Unix-friendly (.Z or .gz file extensions) and PC-friendly (.zip) compressed archives. Most documents are available in PostScript (.ps) and Adobe PDF (.pdf) formats; briefing slides are available in HTML (.htm or .html), PostScript (.ps), PowerPoint (.ppt) and PDF (.pdf)). Beware, some of these files, especially the PostScript ones, are rather large.
Important: Respect the copyright information included in each distribution.
Network Time Protocol (NTP) Version 4
Network Time Protocol web site
This is a compressed archive containing the NTP Version 4 sources, documentation and supporting utilities for Unix, VMS and Windows. It can be compiled and run on over two dozen hardware platforms and operating systems, from personal computers to supercomputers. It includes support for over two dozen radio timecode receivers and special purpose interfaces. It supports cryptographic authentication using the MD5 message digest algorithm, which is included in the distribution.
NTP Version 4 can be exported anywhere, since it does not include cryptographic algorithms subject to export control. However, the cryptographic algorithm interface is compatible with the OpenSSL cryptographic library, which is used by many ubiquitous applications, including TLS and ssh. As explained in the documentation, this distribution can be obtained directly from the www.openssl.org web site.
NTP Version 4 is compatible with all previous NTP versions and the kernel modifications below. While the NTP Version 3 specification document applies also to version 4 of the protocol, this version supports additional features, including autonomous configuration and autonomous authentication, as described in:
- Mills, D.L. The Autokey security architecture, protocol and algorithms. Electrical and Computer Engineering Technical Report 06-1-1, University of Delaware, January 2006, 59 pp. PDF
- Mills, D.L. Public key cryptography for the Network Time Protocol. Electrical Engineering Report 00-5-1, University of Delaware, May 2000. 23 pp. Abstract: PostScript | PDF, Body: PostScript | PDF
Network Time Protocol (NTP) Version 3
This is a compressed archive containing the NTP Version 3 sources, documentation and supporting utilities for Unix, VMS and Windows. It can be compiled and run on over two dozen hardware platforms and operating systems, from personal computers to supercomputers. It includes support for over two dozen radio timecode receivers and special purpose interfaces. It supports cryptographic authentication using the MD5 message digest algorithm, which is included in the distribution.
NTP Version 3 is distributed in two versions, one for use only in the US and Canada and the other (export) for use in other countries. While both versions support MD5-based authentication, which is the preferred algorithm, support for DES-based authentication outside the US and Canada must be provided from sources outside the US and Canada.
NTP Version 3 is compatible with all previous versions and the kernel modifications below. The current NTP Version 3 specification document, which applies to a proper subset of NTP Version 4, is:
- Mills, D.L. Network Time Protocol (Version 3) specification, implementation and analysis. Network Working Group Report RFC-1305, University of Delaware, March 1992, 113 pp. Abstract: PostScript | PDF, Body: PostScript | PDF, Appendices: PostScript | PDF Revised from: Electrical Engineering Department Report 90-6-1, University of Delaware, June 1990, 103 pp. Abstract: PostScript | PDF, Body: PostScript | PDF, Appendices: PostScript | PDF
Precision Radio Clock for WWV Transmissions
This is a program for the DSP-93, a digital signal processor system based on the Texas Instruments TMS320C25 DSP chip. The program works with an inexpensive shortwave receiver to receive, demodulate and decode signals broadcast by NIST radio stations WWV, Ft. Collins, CO, and WWVH, Kauai, HI. The system can provide an ASCII timecode suitable to set the clock on a computer with accuracy less than a millisecond. The principal advantage using the DSP approach is successful operation with very weak signals, such as with an indoor antenna far from the transmitters. Further details are in the technical report:
- Mills, D.L. A precision radio clock for WWV transmissions. Electrical Engineering Report 97-8-1, University of Delaware, August 1997, 25 pp. Abstract: PostScript | PDF, Body: PostScript | PDF
Gadget Box Level Converter
This is a compressed archive containing the schematics, artwork and related information for (a) a modem for the Canadian time/frequency radio service CHU, which can be used as a primary reference clock for NTP Version 2 and Version 3 daemons, and (b) a pulse shaper and line driver used to provide an external one-pulse-per-second signal from a radio clock to a serial port. See above and the NTP Version 3 distribution for an example of its use.
Unix Kernel Timekeeping Support
This is a compressed archive containing sample code segments and documentation for Unix kernel modifications which implement a precision, disciplined clock. The sample code segments, which involve no licensed code, can be incorporated in the timer interrupt routine of Unix workstations. Complete kernels with these modifications have been constructed for SunOS, Ultrix, HP-UX, Digital OSF/1 and Linux kernels. Since these modifications involve licensed code, they are available only from the manufacturer's representatives. A technical report is also available:
- Mills, D.L. Unix kernel modifications for precision time synchronization. Electrical Engineering Department Report 94-10-1, University of Delaware, October 1994, 24 pp. Abstract: PostScript | PDF, Body: PostScript | PDF Major revision and update of: Network Working Group Report RFC-1589, University of Delaware, March 1994. 31 pp. ASCII
Generic Nanosecond Kernel Timekeeping Support
This is a refined version of the Unix kernel modifications described above. It consists of a compressed archive containing sample code segments, documentation and utility programs. It includes a discrete event simulator for evaluating performance of the various algorithms, together with measured peformance data with Digital Alpha and Sun IPC systems, which generally discipline the system clock to better than one microsecond.
Spectracom 8170 WWVB Receiver
PSTI/Traconex 1020 WWV/H Receiver
LORAN-C Stabilized Precision Oscillator
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LORAN-C Receiver PC Card and Oscillator Unit
This is a compressed archive containing the schematics, artwork and documentation for a computer-controlled LORAN-C timing receiver used as a precision source of standard time. The device is designed as an ISA bus peripheral for a PC. It provides a variety of signals useful for calibrating precision time equipment to an accuracy and stability of a few parts in 1010. A technical report is available:
- Mills, D.L. A computer-controlled LORAN-C receiver for precision timekeeping. Electrical Engineering Department Report 92-3-1, University of Delaware, March 1992, 63 pp. Abstract: PostScript | PDF, Body: PostScript | PDF, Appendix A Host Computer Interface: PostScript | PDF, Appendix B Program Listing: PostScript | PDF, Appendix C Schematic Drawings: PostScript | PDF
ICOM Radio Controller
This is a compressed archive containing a C-language program to control HF/VHF radios made by the ICOM Corporation. It can be used interactively or run from a shell script to adjust the frequency, mode and related parameters of one or more radios connected to the CI-V local network. It can also be used in conjunction with the MINIMUF distribution below to automatically tune radios as propagation conditions change throughout the seasons and hours.
MINIMUF Program for HF Radio Propagation Predictions
This is a compressed archive containing a C-language program that computes high frequency radio propagation data between two geographic locations on the Earth. It is useful in setting propagation-delay switches on radio clocks. It can be used interactively or in a shell script in conjunction with the ICOM distribution above to automatically tune radios as propagation conditions change throughout the seasons and hours.
DSP Software Modem for RTTY and SITOR signals
This is a compressed archive containing the program and documentation for an advanced linear receiver for radiotelegraph signals. The program is written for the TI TMS320C25 and the DSP-93 digital modem available from the Tucson Amateur Packet Radio organization (TAPR) (see picture above). A technical report is available:
- Mills, D.L. An optimal linear receiver and codec for a class of radiotelegraph signals. Electrical Engineering Department Report 95-8-1, University of Delaware, August 1995, 91 pp. Abstract: PostScript | PDF, Body: PostScript | PDF, Appendix A Operations: PostScript | PDF, Appendix B RTTY Analysis: PostScript PDF, Appendix C DCD Analysis:PostScript | PDF
