RuggedCom RuggedRouter RX1100 - Manual (Page 268)

32. Configuring IRIGB And IEEE1588
Revision 1.14.3 268 RX1000/RX1100™
32. Configuring IRIGB And IEEE1588
32.1. Introduction
This chapter familiarizes the user with:
• IEEE 1588 Configuration
• IRIGB Configuration
• Viewing IRIGB and IEEE1588 Status
32.1.1. IEEE1588 Fundamentals
The IEEE 1588 working group Precise Timing Protocol (PTP) standard details a method of
synchronizing a clocks over networks, including Ethernet. The RuggedRouter provides a special
hardware assisted PTP capability as provided by the RuggedCom PTP card. When used in
conjunction with the cards Global Positioning System (GPS) receiver, the router can provide
nanosecond accuracy via IEEE1588.
Additionally, IEEE1588 may be used (in GPS failure situations) to synchronize to a remote source
and provide accurate time for IRIG-B.
32.1.1.1. PTP Network Roles
The IEEE 1588 standard describes regular clocks as devices having a single PTP port that can issue
and receive PTP messages. PTP boundary clocks are clocks have multiple PTP ports, offering the
ability to serve time to more than one subnet at a time. The RuggedRouter can serve as a regular
clock and communicate with boundary clocks.
The set of devices that can communicate using the PTP protocol IP multicast transmissions are said
to be in the PTP subdomain. This is usually a set of PTP devices connected by a switched network
or direct links. The "best" clock in the subdomain is known as the master clock. The master clock of
a boundary clock is known as the grandmaster clock.
The protocol negotiates among PTP ports to identify the device with the highest quality clock source.
Ports issuing messages from the master clock are said to be masters, while those that will receive the
messages are slaves. When a port will not participate in the protocol its status is passive. When the
network architect knows the relative quality their clock's time sources, they may configure a specific
clock to be the preferred master.
32.1.1.2. PTP Master Election
PTP clocks exchange SYNC messages containing information which is used by the PTP Best Master
Clock (BMC) algorithm. Several factors will affect the choice of best master clock, including the
preferred master clock setting, the clock identifier, grandmaster settings and clock stability.
The clock identifier is the measure of PTP clock quality and is one of the following:
PTP Identifier Descrption
GPS The PTP clock is a primary reference standard traceable to a recognized standard source
of time such as GPS. The router uses this identifier when GPS is locked.