Profiles And Domains; One-Step And Two-Step Operation - Tektronix PRISM User Manual

Profiles and domains
Profiles
Domains

One-step and two-step operation

PRISM Media Analysis Platform User Manual
Multiple domains and profiles can coexist on the same network.
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.
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.
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 since 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
since there are two messages.
It is interesting to note that in End-to-End mode, only the Sync message is effected
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.
PTP operational overview
153