Kevin, Shahram and all,
I do not actively follow the developments in the ITU-T SG 15, but I believe
that investigation of partial on-path support for PTP (which would be the case
if some LERs on the path were not PTP-aware) has just began there, and it is
not clear what (if anything) could be achieved and under what conditions.
Did I miss something important here?
My 2c,
Sasha
________________________________
From: [email protected] [[email protected]] on behalf of Kevin
Gross [[email protected]]
Sent: Friday, July 19, 2013 7:32 PM
To: Shahram Davari
Cc: [email protected]; S. Davari; [email protected]
Subject: Re: [TICTOC] [mpls] TICTOC WG LC for draft-ietf-tictoc-1588overmpls
You need to specify what you mean by "recover the time correctly." Everytime
you pass through a piece of equipment that is not timing aware, you introduce
noise into the timing signal. More hops, more noise. Noise reduces
synchronization accuracy.
Kevin Gross
+1-303-447-0517
Media Network Consultant
AVA Networks - www.AVAnw.com<http://www.avanw.com/>,
www.X192.org<http://www.X192.org>
On Fri, Jul 19, 2013 at 7:19 AM, Shahram Davari
<[email protected]<mailto:[email protected]>> wrote:
Hi Stewart,
Not necessarily. It is ok if some of the routers in the path are not timing
aware. That is the whole idea. We have tested cases in which 5-7 hops are not
1588 aware and still we can recover the time correctly.
Regards,
Shahram
On Jul 19, 2013, at 3:33 AM, "Stewart Bryant"
<[email protected]<mailto:[email protected]>> wrote:
> On 19/07/2013 09:11, Bhatia, Manav (Manav) wrote:
>> Hi Sasha,
>>
>>> 1) reserved label is not backward compatible with existing routers. One
>>> of the requirements is that routers that are not PTP aware can just
>>> switch the packet normally. Using a reserved label can't achieve this
>>> requirement, since routers that don't understand it will drop it or
>>> sent it to CPU.
>>> [[Sasha]] Is not this concern applicable to any new reserved label?
>>> And routers that use network processors as forwarding engines could
>>> easily overcome this issue by upgrading their microcode.
>>> But I agree that this is a valid concern.
>> This is a huge concern because not all routers use network processors that
>> can be reprogrammed.
>>
>> The current solution works with any router that can set up an MPLS path.
> Really?
>
> Surely the LSR needs to know that on seeing a label in the FEC it needs
> to timestamp the packet.
>
> Stewart
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