NetApp CN1610 - Sntp

Chapter 2: Switch Administration 33
SNTP
Feature overview The Simple Network Time Protocol (SNTP) is widely used for synchronizing
network resources. SNTP Version 4 is described in RFC 2030. SNTP is an
adaptation of the Network Time Protocol (RFC 1305) and is useful in situations
where the full performance of NTP is not justified. SNTP can operate in either
unicast mode (point-to-point) or broadcast mode (point-to-multipoint).
Various NTP implementations can operate as either a client or as a server. To an
NTP or SNTP server, NTP and SNTP clients are indistinguishable; to an NTP or
SNTP client, NTP and SNTP servers are indistinguishable. Furthermore, any
version of NTP is compatible with any other version of NTP1. The CN1610
switch software implements only the client side of SNTP.
Basic operation The SNTP client runs over UDP. The time products derived from the operation of
the SNTP client are used to synchronize the system clock with the network time.
The system clock is used to provide a network synchronized timestamp service to
internal clients for use in time stamping events within the switch software (for
example, message logs).
In the event that the SNTP client is unable to synchronize with the network clock
or is disabled, the internal clients will continue to use the system clock for
timestamps. In general, internal clients will not be aware of whether the
timestamps are synchronized with the network clock.
Depending on the mode of operation, the SNTP client listens on UDP port 123 on
the local management interface for broadcast UDP packets containing valid NTP
data or queries one or more configured time servers and listens for responses.
The switch internal clients include the message logging subsystem, the trap
manager (timestamps for traps), and other clients that require high-precision
synchronized timestamps.
The administrator has the option of enabling a security mechanism to ensure that
only authorized servers are allowed to distribute time to the client. The user
defines a key on the switch and enables authentication. The same key must be
defined on the server in order for the switch to accept time information from that
server.