Re: [Linuxptp-users] About gptp and ptp 1588

[Keller, J. E <jac...@in...>]

Hello -

gPTP is supposed to be a subset of 1588 PTP, however it has modifications to the standard. It is part of 802.1AS, and the gPTP standard is freely available online. In general, gPTP just has more restrictions on what it defines as acceptable, ie: you can't use E2E mode in gPTP. Both support Transparent clocks, assuming you have hardware capable of it. I don't know if linuxPTP supports transparent clocks at this time.

The gPTP.config file uses the settings that make LinuxPTP compatible with the gPTP standard. Some of those changes may result in better performance of PTP, (depending on your system and the requirements).

Fundamentally they are very similar, and perform using the same type of mechanisms.

gPTP is supposed to be a profile for PTP but it has some non-compatible changes which are not supposed to be allowed for a profile. The following is a list of the profile requirements.

PTP Profile Included in
IEEE 802.1AS - 1
Profile Item Specification
Best master clock
algorithm (BMCA) option
Alternate BMCA (similar, but not identical, to
algorithm (BMCA) option 1588 clause 9) 1588 clause 9)
Management mechanism SNMP MIB
Path delay mechanism Peer delay mechanism
802 1AS ifi d f l 802.1AS specifies default S i l 1/8
values; 802.1BA may
specify additional ranges
for each AVB profile
Sync interval: 1/8 s
Announce interval: 1 s
Pdelay interval: 1 s
for each AVB profile
Announce receipt timeout: 2 announce
intervals
Sync receipt timeout: 3 sync intervals
Node types Boundary clock (synchronization specified in
manner similar to peer-to-peer transparent
clock; BC and peer-to-peer TC synchronization
can be shown to be mathematically can be shown to be mathematically
equivalent, see [6])
Ordinary clock

This is taken from http://www.itu.int/dms_pub/itu-t/oth/06/38/T06380000040002PDFE.pdf



From: Aman Sharma [mailto:ama...@gm...]
Sent: Thursday, July 11, 2013 12:06 AM
To: lin...@li...
Subject: [Linuxptp-users] About gptp and ptp 1588

Hi all,


Can anyone please explain the difference between gPTP and 1588 PTP .And How do I know which is better one for my system architecture.Detail explanation is required for understanding the architecture of both gPTP and 1588 PTP.

Can we use E2E and P2P Transparent clock in gPTP ?

Please help me in this ASAP.
Plz Revert me in case you have any query.

--
regards
Aman Sharma