PRISM MPI2-25 and MPX2-25 Media Analysis Platform User Manual
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Profiles and domains
Multiple domains and profiles can coexist on the same network.
Profiles
The IEEE1588 standard defines multiple parameters, such as the rates for Sync
and Announce messages, and optional functions such as grandmaster clusters.
Specific industries wanting to use PTP are encouraged to define their own
“profile,” which allows the PTP standard to be tuned for specific applications.
The profile defines the default and range of each parameter, and defines with
options are required, allowed or prohibited.
In the Prism monitor, the user should select the PTP profile (General, ST2059, or
AES67). The user can then modify the profile parameters and save as part of an
instrument preset. The allowed range of the parameters is restricted to that which
is allowed for the selected profile type.
Domains
The IEEE1588 standard defines “domains,” which allow multiple PTP services to
coexist simultaneously on one physical Ethernet connection. For example, on a
given network one master and several slaves can be using domain 0 while a
second master and other slaves are using domain 1. These two PTP services are
independent. One use for this is to have masters on different domains provide PTP
on different profiles. For example, domain 0 might be an AES67 profile, domain
1 could be a master using the AVB (802.1AS) profile, and domain 127 could be a
master on the SMPTE ST2059 profile.
One-step and two-step operation
Some PTP messages have a time stamp associated with them. This time stamp
indicates the time of the local clock when the message was sent or received.
In some cases, the hardware is capable of embedding the time stamp in the
message as it is sent. This is known as “one-step” mode because the message and
its associated time are sent together.
In other cases, the hardware is not capable of inserting the time into the message,
so instead it is sent in a second follow-up message. This is called “two-step” mode
because there are two messages.
It is interesting to note that in End-to-End mode, only the Sync message is
affected by the one-step and two-step setting since it is the only message that
needs the transmit time stamp inserted. In a similar fashion, Peer-to-Peer mode
has some messages that may require follow-up support.
The IEEE1588 standard specifies that all slaves are required to operate with either
one-step or two-step message types. One type of device which often requires two-
step operation is a Transparent Clock, since it has to calculate the residence time
of a message and insert that time into the message or the follow-up message.
