linuxptp-users

[Linuxptp-users] Hardware timestamping with bridge device?

[Thomas M. <tm....@gm...>]

Hi everybody,

for a project I have to synchronize around 3 or 4 devices. Because all 
devices have two ethernet ports, one requirement is not to use a 
separate network switch. Instead the idea is to chain up all devices and 
use the middle device(s) as bridge(s).

Example:

DEV1_eth0|DEV1_eth1 <--> DEV2_eth0|DEV2_eth1 <--> DEV3_eth0|DEV3_eth1

I have already tried a few things, but it seems that it's not possible 
to use hardware timestamping with a bridge device.

Has anybody tried to build something like this and can give me a little 
help?


Thanks,
Thomas

Re: [Linuxptp-users] Hardware timestamping with bridge device?

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

On Tue, Mar 18, 2014 at 11:48:19AM +0100, Thomas Mayer wrote:
> Hi everybody,
> 
> for a project I have to synchronize around 3 or 4 devices. Because all 
> devices have two ethernet ports, one requirement is not to use a 
> separate network switch. Instead the idea is to chain up all devices and 
> use the middle device(s) as bridge(s).
> 
> Example:
> 
> DEV1_eth0|DEV1_eth1 <--> DEV2_eth0|DEV2_eth1 <--> DEV3_eth0|DEV3_eth1
> 
> I have already tried a few things, but it seems that it's not possible 
> to use hardware timestamping with a bridge device.

You would need to write firewall rules to divert PTP events to the
local host.
 
> Has anybody tried to build something like this and can give me a little 
> help?

So you want to build a Transparent Clock?  Linuxptp does not implement
this, but you might be able to reuse parts of the code. I think it
will be a bit of work.

Good luck,
Richard

Re: [Linuxptp-users] Hardware timestamping with bridge device?

[Thomas M. <tm....@gm...>]

On 18.03.2014 19:05, Richard Cochran wrote:
> On Tue, Mar 18, 2014 at 11:48:19AM +0100, Thomas Mayer wrote:
>> Hi everybody,
>>
>> for a project I have to synchronize around 3 or 4 devices. Because all
>> devices have two ethernet ports, one requirement is not to use a
>> separate network switch. Instead the idea is to chain up all devices and
>> use the middle device(s) as bridge(s).
>>
>> Example:
>>
>> DEV1_eth0|DEV1_eth1 <--> DEV2_eth0|DEV2_eth1 <--> DEV3_eth0|DEV3_eth1
>>
>> I have already tried a few things, but it seems that it's not possible
>> to use hardware timestamping with a bridge device.
>
> You would need to write firewall rules to divert PTP events to the
> local host.
>
I was afraid to hear that, now I have to increase my knowledge about 
iptables first :D

>> Has anybody tried to build something like this and can give me a little
>> help?
>
> So you want to build a Transparent Clock?  Linuxptp does not implement
> this, but you might be able to reuse parts of the code. I think it
> will be a bit of work.
>
Not really :D ...I still hope that a simple installation with Ordinary 
Clocks only works fine for my use case.


Thanks,
Thomas

Re: [Linuxptp-users] Hardware timestamping with bridge device?

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

On Wed, Mar 19, 2014 at 09:06:00AM +0100, Thomas Mayer wrote:
> Not really :D ...I still hope that a simple installation with Ordinary 
> Clocks only works fine for my use case.

It will work best if eth0 and eth1 share the same hardware
clock. Otherwise, you will need 5 servo for a chain of 4 nodes.

Thanks,
Richard