Re: [Linuxptp-devel] [PATCH 0/5] Add minimal gPTP (802.1 AS) support

[Delio B. <dbr...@au...>]

On Jul 14, 2012, at 12:49 PM, Richard Cochran wrote:

> On Sat, Jul 14, 2012 at 11:11:39AM +0200, Richard Cochran wrote:
>> 
>> I studied 802.1AS-2011 a bit, and I think that the ptp4l program could
>> also function as a "time-aware end station" (but not as a bridge). But
>> I wonder whether there will be conformance issues, for example when we
>> have ClockMaster = ClockSlave = LocalClock.
> 
> And just to get the discussion going, here is a list of what I think
> needs to get done in order to support gPTP minimally.
> 
> - config option for transportSpecific field.
> - config option for L2 destination MAC addresses
> - generic TLV support (need this for 1588-2008 management anyhow)
> - path trace TLV
> - alternate BCM algorithm state machine (controlled by config file option)
> - transmit hooks on general messages (controlled by config file options)
> - use the cumulativeScaledRateOffset when slave
> - send a reasonable looking Follow_Up information TLV when grand master
> - handle signaling message with Message Interval Request TLV
> 
> (and maybe more)

The above looks good, we also need at least:
- config option to ignore twoStepFlag and force two step sync

and I would add:
- calculate/use neighborRateRatio for pdelayRateRatio calculation
- optionally use exp averaging filter for pdelayRateRatio as described in 11.1.2 of 802.1AS

Regards
--
Delio