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Re: [TICTOC] [mpls] TICTOC WG LC for draft-ietf-tictoc-1588overmpls

Kevin Gross <kevin.gross@avanw.com> Fri, 19 July 2013 17:35 UTC

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Date: Fri, 19 Jul 2013 11:32:54 -0600
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From: Kevin Gross <kevin.gross@avanw.com>
To: Shahram Davari <davari@broadcom.com>
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Cc: "mpls@ietf.org" <mpls@ietf.org>, "S. Davari" <davarish@yahoo.com>, "tictoc@ietf.org" <tictoc@ietf.org>
Subject: Re: [TICTOC] [mpls] TICTOC WG LC for draft-ietf-tictoc-1588overmpls
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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


On Fri, Jul 19, 2013 at 7:19 AM, Shahram Davari <davari@broadcom.com> 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" <stbryant@cisco.com> 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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> >
>
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