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Masterclock NTDS Series User Manual – v2 – December 2012

MULTICAST

The network device also supports Multicast Addressing of NTP

packets. Multicasting is useful because it conserves bandwidth.

Multicasting replicates only the necessary packets and only as

needed to send them only to clients that want them.

The concept of a group, and group membership, is crucial to

multicasting. Every multicast requires a multicast group; the

sender transmits to the group address, and only members of the

group can receive the multicast data. A group is defined by a

Class D address.

The network device does not restrict the use of the multicast

address assignment and supports the full range of class D

multicast addresses or groups from “224.0.0.0” to

“239.255.255.255”. These are defined and governed by

RFC3171, IANA IPv4 Multicast Guidelines.

Typically, the multicast address range “224.0.1.0” to

“224.0.1.255” (Internetwork Control Block) is used for NTP

traffic. However, please refer to the RFC3171 for your specific

application and implementation.

The IGMP (Internet Group Management Protocol) controls

group membership for individual hosts. This protocol only

operates in a LAN setting, but is required if you wish to be able

to join a multicast group on a host. IGMP is defined in RFC 2236.

ANYCAST

The network device does not currently provide Anycast

capability.

STATIC IP

To use a static IP address, de-select the checkbox for

“Automatically obtain network configure tion from

DHCP/BOOTP.” You must enter the IP address, netmask,

gateway, primary DNS and also a secondary DNS.

Devices which have been assigned a fallback IP address of

“169.254.xxx.xxx” will be displayed in the main WinDiscovery

window with RED text, indicating a problem with the

configuration.

NTP CLIENT AUTHENTICATION SETTINGS

The NTDS series uses the MD5 Message Digest Algorithm, which

is a widely used cryptographic hash function that produces a

128-bit hash value.

IGMP

Use of the multicast addressing method

requires the use of routers and switches and

other network devices which support the

Internet Group Management Protocol

(IGMP).

In addition, the IGMP mode must be enabled

and configured for multicast addressing to be

implemented properly. Please ensure that

your network system components are capable

of, and configured properly for, IGMP before

utilizing the multicast addressing feature.

Consult you network administrator for

assistance in utilizing the multicast addressing

feature.

FIREWALLS

Check with your firewall vendor to determine

how to enable multicast traffic through a

firewall. In addition, you may want to read

RFC 2588: IP Multicast and Firewalls.

Port 123

Some NTP/SNTP servers will expect NTP

clients to operate on port 123.

If the advanced settings have been altered for

your clock and you begin experiencing

difficulty in getting your clock to synchronize

to the NTP time server, or the clock begins

acting erratically, try returning the advanced

settings to the default values: “123.”

NTP CLIENT ADVANCED SETTINGS

From the NTP Client window, the [NTP Client

Advanced Settings] button allows for the

adjustment of additional network

communication settings. Under most

operating circumstances it is not necessary

to change these settings.

The factory-default TCP/UDP port for NTP

service is: “123”

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