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hopf
Elektronik GmbH
Nottebohmstr. 41
• D-58511 Lüdenscheid • Tel.: +49 (0)2351 9386-86 • Fax: +49 (0)2351 9386-93 • Internet: http://www.hopf.com • E-Mail: info@hopf.com
5.3.4.4 Server Configuration
The basic settings for NTP base functionality are displayed when the "Server Configuration"
link is selected.
5.3.4.4.1 Broadcast / Multicast
This section is used to configure the Network Time Client 8029NTC as a broadcast or multicast
server.
The broadcast mode in NTPv3 and NTPv4 is limited to clients on the same sub-network and
Ethernets which support broadcast technology.
This technology does not generally extend beyond the first hop (network node - such as router
or gateway).
The broadcast mode is provided for configurations which are designed to facilitate one or more
servers and as many clients as possible in a sub-network. The server continuously generates
broadcast messages at defined intervals, corresponding to 16 seconds (minpoll 4) for Network
Time Client 8029NTC. Care should be taken to ensure that the correct broadcast address is
used for the sub-network, usually xxx.xxx.xxx.255 (e.g. 192.168.1.255). If the broadcast
address is not known, this can be requested from the network administrator.
This section can also be used to configure the Network Time Client 8029NTC as a multicast
server. The configuration of a multicast server is similar to that of a broadcast server. However,
a multicast group address (class D) is used instead of the broadcast address.
An explanation of multicast technology goes beyond the scope of this document.
In principle, a host or router sends a message to an IPv4 multicast group address and expects
all hosts and routers to receive this message. In doing so, there is no limit to the number of
senders and receivers and a sender may also be a receiver and vice-versa. The IANA has
assigned the multicast group address IPv4 224.0.1.1 to the NTP, however this should only be
used if the multicast range can be safely limited in order to protect neighbouring networks. As
a basic principle, administratively manageable IPv4 group addresses should be used as
described in RFC-2365 or GLOP group addresses as described in RFC-2770.