Re: [Linuxptp-users] Port option: logMinDelayReqInterval

[Ledda W. E. <Wil...@it...>]

If you are able to take a look into the IEEE 1588 standards, see section 9.5.11 (Transmission of a Delay_req message) and in particular section 9.5.11.2 (Timing requirements). It states that:

The transmission of the Delay request message from a port SHALL be limited as follows:

- The initial may be transmitted when required
- Following messages in a way such that the mean interval, in seconds, is not less than the value of 2^logMinDelayreqInterval seconds (where logMinDelayreqInterval  us the logMessageInterval field of the last Delay response received)

The standard provides also two option to meet this requirement.

HTH

William
-----Original Message-----
From: Miroslav Lichvar [mailto:mli...@re...] 
Sent: 17 March 2015 14:03
To: Chandra Mallela
Cc: Ledda William EXT; lin...@li...
Subject: Re: [Linuxptp-users] Port option: logMinDelayReqInterval

On Tue, Mar 17, 2015 at 12:47:13PM +0000, Chandra Mallela wrote:
> 1.      Which field in the delay response indicates the value to the slave announed by the master? Is it logMessageInterval?

Yes.

> 2.      DelayReq packet is sent by the slave. Thus, the number of DelayReq packets to be sent is to be controlled by the slave. Am I right? Why should it be an option with master?

Master tells slaves how often they should be polling the master.

> An answer to my own question: It is the master being burdened to respond to possibly many number of slaves. Hence, it controls the number. Is this the rationale for what you have mentioned below?

Yes, I think that's correct. The sync interval is controlled by master, so the delay interval should be too.

--
Miroslav Lichvar