linuxptp-users

[Linuxptp-users] Help Needed about Transparent Clock

[Akhil N. <akh...@tc...>]

Dear All,
I want to know about linux ptp whether it supports Transparent Clock and
if it doesn't support it is there any scope of implementation in
future ?
I also want to know that with the hardware and software time stamping
can we get the operation of transparent clock ?

Thanks and Regards
 

-- 
Akhil Nair <akh...@tc...>

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Re: [Linuxptp-users] Help Needed about Transparent Clock

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

On Tue, Apr 16, 2013 at 11:41:38AM +0530, Akhil Nair wrote:
> Dear All,
> I want to know about linux ptp whether it supports Transparent Clock and
> if it doesn't support it is there any scope of implementation in
> future ?

No, transparent clock is not implemented. This would be a major new
feature, and I have no plan to start working on it.

> I also want to know that with the hardware and software time stamping
> can we get the operation of transparent clock ?

I think SW time stamping cannot be used in a TC.

Thanks,
Richard

Re: [Linuxptp-users] Help Needed about Transparent Clock

[Keller, J. E <jac...@in...>]

> -----Original Message-----
> From: Richard Cochran [mailto:ric...@gm...]
> Sent: Tuesday, April 16, 2013 10:21 AM
> To: Akhil Nair
> Cc: lin...@li...
> Subject: Re: [Linuxptp-users] Help Needed about Transparent Clock
> 
> On Tue, Apr 16, 2013 at 11:41:38AM +0530, Akhil Nair wrote:
> > Dear All,
> > I want to know about linux ptp whether it supports Transparent Clock
> and
> > if it doesn't support it is there any scope of implementation in
> > future ?
> 
> No, transparent clock is not implemented. This would be a major new
> feature, and I have no plan to start working on it.
> 
> > I also want to know that with the hardware and software time
> stamping
> > can we get the operation of transparent clock ?
> 
> I think SW time stamping cannot be used in a TC.
> 
> Thanks,
> Richard
> 

As far as I know, it cannot. I believe TC also requires the same issue as BC which is multiple ports connected to a  single device?

- Jake

Re: [Linuxptp-users] Help Needed about Transparent Clock

[Akhil N. <akh...@tc...>]

Dear jake,
On Tue, 2013-04-16 at 18:17 +0000, Keller, Jacob E wrote:
> > -----Original Message-----
> > From: Richard Cochran [mailto:ric...@gm...]
> > Sent: Tuesday, April 16, 2013 10:21 AM
> > To: Akhil Nair
> > Cc: lin...@li...
> > Subject: Re: [Linuxptp-users] Help Needed about Transparent Clock
> > 
> > On Tue, Apr 16, 2013 at 11:41:38AM +0530, Akhil Nair wrote:
> > > Dear All,
> > > I want to know about linux ptp whether it supports Transparent Clock
> > and
> > > if it doesn't support it is there any scope of implementation in
> > > future ?
> > 
> > No, transparent clock is not implemented. This would be a major new
> > feature, and I have no plan to start working on it.
> > 
> > > I also want to know that with the hardware and software time
> > stamping
> > > can we get the operation of transparent clock ?
> > 
> > I think SW time stamping cannot be used in a TC.
> > 
> > Thanks,
> > Richard
> > 
> 
> As far as I know, it cannot. I believe TC also requires the same issue as BC which is multiple ports connected to a  single device?

So you mean to say there is an issue with BC that in BC multiple ports
can not be connected to single device ?

As far as TC it only update the time stamp of the packet and the link
delay so if there are multiple ports also the packet time stamp will be
updated.
> - Jake
> 


-- 
Akhil Nair
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Cell no.  +917871362812
Mailto: akh...@tc...
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Re: [Linuxptp-users] Help Needed about Transparent Clock

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

On Tue, Apr 16, 2013 at 06:17:23PM +0000, Keller, Jacob E wrote:
> 
> As far as I know, it cannot. I believe TC also requires the same issue as BC which is multiple ports connected to a  single device?

Yes, however the TC only has to correct the residence time of the PTP
packets in the switch. So it would not necessarily have to synchronize
multiple PHCs in a system.

But there are other issues to consider. A TC must behave like a
switch. Although you can use Linux to bridge multiple ports, still the
performance is not as good as real switch. So I would expect that no
one would be interested in a TC built on a Linux software switch.

The commercial TCs that I have seen combine a normal managed switch
with an embedded processor. The switch diverts the PTP packets to the
processor which then performs the TC functions.

HTH,
Richard

Re: [Linuxptp-users] Help Needed about Transparent Clock

[Akhil N. <akh...@tc...>]

On Wed, 2013-04-17 at 07:31 +0200, Richard Cochran wrote:
> On Tue, Apr 16, 2013 at 06:17:23PM +0000, Keller, Jacob E wrote:
> > 
> > As far as I know, it cannot. I believe TC also requires the same issue as BC which is multiple ports connected to a  single device?
> 
> Yes, however the TC only has to correct the residence time of the PTP
> packets in the switch. So it would not necessarily have to synchronize
> multiple PHCs in a system.
> 
> But there are other issues to consider. A TC must behave like a
> switch. Although you can use Linux to bridge multiple ports, still the
> performance is not as good as real switch. So I would expect that no
> one would be interested in a TC built on a Linux software switch.

So you mean to say that the router can not be used as TC ?
and also if it is been used then the performance won't be good as when
used with switch ? 
> The commercial TCs that I have seen combine a normal managed switch
> with an embedded processor. The switch diverts the PTP packets to the
> processor which then performs the TC functions.
> 
> HTH,
> Richard
> 
> 

Thanks and Regards

-- 
Akhil Nair <akh...@tc...>

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Re: [Linuxptp-users] Help Needed about Transparent Clock

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

On Wed, Apr 17, 2013 at 10:54:41AM +0530, Akhil Nair wrote:
> On Wed, 2013-04-17 at 07:31 +0200, Richard Cochran wrote:
> > 
> > But there are other issues to consider. A TC must behave like a
> > switch. Although you can use Linux to bridge multiple ports, still the
> > performance is not as good as real switch. So I would expect that no
> > one would be interested in a TC built on a Linux software switch.
> 
> So you mean to say that the router can not be used as TC ?

Don't confuse router with switch.

> and also if it is been used then the performance won't be good as when
> used with switch ? 

What I meant was that a mutli-homed, general purpose computer running
Linux can be used as a poor-man's switch. This could be extended with
TC functionality, but probably the result would not be acceptable WRT
the normal switching performance.

HTH,
Richard

Re: [Linuxptp-users] Help Needed about Transparent Clock

[Akhil N. <akh...@tc...>]

Dear Richard,
Thank you for clearing the doubt.
On Wed, 2013-04-17 at 07:57 +0200, Richard Cochran wrote:
> On Wed, Apr 17, 2013 at 10:54:41AM +0530, Akhil Nair wrote:
> > On Wed, 2013-04-17 at 07:31 +0200, Richard Cochran wrote:
> > > 
> > > But there are other issues to consider. A TC must behave like a
> > > switch. Although you can use Linux to bridge multiple ports, still the
> > > performance is not as good as real switch. So I would expect that no
> > > one would be interested in a TC built on a Linux software switch.
> > 
> > So you mean to say that the router can not be used as TC ?
> 
> Don't confuse router with switch.
> 
> > and also if it is been used then the performance won't be good as when
> > used with switch ? 
> 
> What I meant was that a mutli-homed, general purpose computer running
> Linux can be used as a poor-man's switch. This could be extended with
> TC functionality, but probably the result would not be acceptable WRT
> the normal switching performance.

Ok. Is there any way to configure TC on above mentioned multi-homed,
general purpose computer running with linux as a Transparent Clock if
the performance is not a main concern ?
> HTH,
> Richard
> 

Thanks and Regards

-- 
Akhil Nair <akh...@tc...>

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Re: [Linuxptp-users] Help Needed about Transparent Clock

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

On Wed, Apr 17, 2013 at 11:25:40AM +0530, Akhil Nair wrote:
> 
> Ok. Is there any way to configure TC on above mentioned multi-homed,
> general purpose computer running with linux as a Transparent Clock if
> the performance is not a main concern ?

Well, you cannot simply configure it. You would have to develop
this. But it can be done, I think.

Richard