Re: [Linuxptp-devel] [PATCH 1/4] Schedule announce TX timeout also when in slave-only mode

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

On Dec 1, 2013, at 7:48 AM, Richard Cochran <ric...@gm...> wrote:

> On Sat, Nov 30, 2013 at 09:46:46PM +0100, Delio Brignoli wrote:
>> 
>> Yes, but... 802.1AS does not have a different state machine for
>> slave-only operation, instead a non grand-master capable time-aware
>> system has a property1 value of 255 (see second paragraph of section
>> 8.6.2.1). Additionally, according to point f.5 of section
>> 10.3.12.1.4 updtRolesTree(), if the current portPriorityVector is
>> the portPriorityVector of the time-aware system (i.e. we have not
>> yet received an announce message with better portPriorityVector) the
>> portRole should be set to MasterPort which makes the txAnnounce
>> method reachable.
> 
> This brings to mind two questions.
> 
> 1. Does omitting the announce message from a slave only node cause you
> interoperability problems?

Yes, we are failing interoperability tests without this fix.

> 2. What is the point of the slave only node's announce messages?
> 
> [ The announce messages will not affect the outcome of the peer's
> BMC election, except to make it slower. ]


Knowing the node exists and it is a slave I guess...

From point i.4 of section 7.5 "Differences between gPTP and PTP": "all time-aware systems are required to participate in best master selection (even if it is not grandmaster capable)".

Thanks
--
Delio