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Boundary
clock: A boundary clock is a clock with more than a single
PTP port, with each PTP port providing access to a separate PTP
communication path. Boundary clocks are used to eliminate fluctuations
produced by routers and similar network elements.
Clock:
A device providing a measurement of the passage of time since a defined
epoch. There are two types of clocks in 1588: boundary
clocks and ordinary clocks.
Clock
timestamp point: 1588 requires the generation of a
timestamp on transmission or receipt of all 1588 Sync and Delay_Req
messages. The point in the outbound and inbound protocol stacks where this
timestamp is generated is called the clock timestamp point.
Direct
communication: The communication of PTP information
between two PTP clocks with no intervening boundary clock is termed a direct
communication.
External
synchronization: It is often desirable to synchronize a
single clock to an external source of time, for example to a GPS system to
establish a UTC time base. This synchronization is accomplished by means
other than those specified by 1588 and is referred to as external
synchronization
Epoch:
The reference time defining the origin of a time scale is termed the
epoch.
Grandmaster
clock: �Within
a collection of 1588 clocks one clock, the grandmaster clock, will serve as
the primary source of time to which all others are ultimately synchronized.
Master
clock: A system of 1588 clocks may be segmented into
regions separated by boundary clocks. Within each region there will be a
single clock, the master clock, serving as the primary source of time. These
master clocks will in turn synchronize to other master clocks and ultimately
to the grandmaster clock.
Message
timestamp point: 1588 Sync and Delay_Req messages contain
a distinguished feature, the message timestamp point, serving as a reference
point in these messages. When the message timestamp point passes the clock
timestamp point, a timestamp is generated that is used by 1588 to compute
the necessary corrections to the local clock.
Ordinary
clock: An ordinary clock is a 1588 clock with a single PTP
port.
Preferred
master clock set: 1588 allows the definition a set of
clocks that will be favored over those not so designated in the selection of
the grandmaster clock.
PTP:
PTP is an acronym for Precision Time Protocol, the name used in the
standard for the protocol.
PTP
domain: A PTP domain is a collection of one or more PTP
subdomains.A subdomain is a logical grouping of
1588 clocks that synchronize to each other using the PTP protocol, but that
are not necessarily synchronized to PTP clocks in another PTP subdomain.
Subdomains provide a way of implementing disjoint sets of clocks, sharing a
common network, but maintaining independent synchronization within each set.
PTP
message: There are five designated messages types defined by
1588: Sync, Delay_Req, Follow-up, Delay_Resp, and Management.
Multicast
communication: 1588 requires that PTP messages be
communicated via a multicast. In this style of communication any node may
post a message and all nodes in the same segment of a subdomain will receive
this message. Boundary clocks define the segments within a subdomain.
PTP
port: A PTP port is the logical access point for 1588
communications to the clock containing the port.
Synchronized
clocks: Two clocks are synchronized to a specified
uncertainty if they have the same epoch and measurements of any time
interval by both clocks differ by no more than the specified uncertainty.
The timestamps generated by two synchronized clocks for the same event will
differ by no more than the specified uncertainty.
