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

[Richard C. <ric...@gm...>]

On Mon, Jul 16, 2012 at 10:58:14AM +0200, Delio Brignoli wrote:
> 
> 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

Before you had said that, with the patches you posted, gPTP was
already working for you. But not synchronization? Do you really need
the neighborRateRatio and cumulativeScaledRateOffset, or can these be
ignored (as the AS standard seems to suggest in a few places)?

Can you please clarify this for me?

Thanks,
Richard