S100 and time distribution, S100 and client software, S100 and ntp v4’s security features – Symmetricom S100 User Manual
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S100 User Guide – Rev. D – June 2005
1
SyncServer S100
More details are found in
“Chapter 3” on page 13 and “The Web-Based Interface” on
S100 and Time Distribution
Time is distributed over an IP network using Network Time Protocol (NTP), Simple Network
Time Protocol (SNTP), Time Protocol, and Daytime Protocol over TCP/IP.
S100s can be distributed throughout a LAN or intranet. Also, a single GPS antenna is all that
is required to acquire UTC time for an array of S100s, making the network less vulnerable to
damage or attack. (Note: The GPS antenna described in this manual has been replaced as
described in
.)
Once the S100 is locked with its time source, it will continuously provide time even if the
timing signal is lost. If the GPS time signal is lost, the NTP message returned by the S100 will
indicate—from the Reference Timestamp—when it last obtained time updates from the timing
signal.
The S100 maintains the year value as a four-digit number. The S100 maintains time as binary
seconds and has no problem with leap-years and the introduction of leap seconds.
S100 and Client Software
Install NTP client software on the client machines in order to synchronize those clients with
S100’s NTP server.
Obtain the SymmTime™ NTP client for Windows
.
Details about installing SymmTime are found in
“Installing SymmTime” on page 49
Unix/Linux clients can be synchronized using the public domain NTP daemon or equivalent
NTP client software. If an NTP daemon is not available for your system, you can obtain a
copy of RFC 1305 or 2030 from the Network Information Center (NIC) at
order to implement an NTP daemon for your system.
S100 and NTP v4’s Security Features
NTP is the de facto standard of communicating time in IP network environments. Developed
at the University of Delaware in the United States, NTP is public domain software. It can
provide time without opening the NTP port and exposing the firewall to possible intrusion. The
S100 supports NTP v4 (Secure NTP), and can support NTP v2 and v3, as well.
The S100 generates keys, which take the form of a file composed of random numerical
sequences. These key files are recognized by the cryptographic authentication components
of NTP. These keys are symmetric, or private (in NTP v3 and v4), and asymmetric or public or
Autokey (NTP v4); Autokey protocol, therefore, can recognize the key files as well. The
contents of the key files include the public/private key pair, a certificate request, a certificate,
and Diffie-Hellman parameters.