PTPv2 network infrastructure question

[Mirek Sobczak]

Hello,

I've OMICRON CMGPS 588 working as Grandmaster clock. Unfortunately I haven't any switch suporting IEEE 1588.
than my network looks like that:

+-----------------+        +-----------+       +--------------------+
|    CMGPS 588    | ------ |   Switch  |-------| My testing ARM SoC |
+-----------------+        +-----------+       +--------------------+
                                                                    |
                                                        +----------+
                                                        |    PC    |
                                                        +----------+

edit: PC is connected to switch

I've observed PTPv2 packets at PC and at ARM SoC.
Is it possible that ptpd2 deamon will work in this configuration?
When I connect OMICRON CM 353 - test equipment to this switch it doesn't synchronize over PTP

Kind regards
Mirek

[Wojciech Owczarek]

Mirek,

I'm not sure what your question really is. Where do you want to run PTPd? On the SoC or on the PC? Is the SoC routing or forwarding PTP packets to the PC?

The reasons why the CM353 does not synchronise can be many... Is this a managed switch, is it running IGMP snooping? Does it work when you connect CM353 directly to the CMGPS?

You don't need a PTP aware switch to run PTP, it helps on busy networks or when there are many hops, but it is not essential. PTP works fine with no network assistance.

Thanks,
Wojciech

[Mirek Sobczak]

Wojciech,
PTPd is run on SoC in slave mode to synchronise clock in device where SoC is embedded.
PC is only for test network trafic.

CM353 is working correctly when CMGPS 588 is connected directly to it.
My switch is HP 1810-8 Switch. It is managed. About " IGMP snooping" sorry I heard first time this term. I need to learn about it. Maybe it helps.

I thought that regular switch should be transparent to PTP packetes. But in CMGPS 588 manual is a picture where switch is with IEEE 1588 support.

Thanks
Mirek

[Wojciech Owczarek]

OK. You should check if IGMP snooping is enabled on your switch.

IGMP is the protocol used to manage multicast group join and leave on the same segment / Layer 2 network / subnet. To receive multicast, host sends an IGMP join. When it doesn't want it anymore, it sends an IGMP leave (in IGMP v2 and above).

IGMP snooping tracks these joins and switch only sends multicast to the ports which joined the group. Without IGMP snooping, this is not tracked and multicast is flooded to all ports on the same VLAN.

So if IGMP snooping is enabled on the switch, PTPd will get multicast because it always sends IGMP joins. Test equipment typically does not (and this is wrong - see my post about this: http://www.theptpguy.net/posts/2015/08/31/dear-ieee-1588-implementers-remember-about-igmp), and it just expects multicast to be flooded - so one reason why the Omicron tester is not getting multicast can be IGMP snooping.

See this for ProCurve: https://community.spiceworks.com/how_to/26481-enable-igmp-on-hp-procurve

Many industries assume that PTP switches will be PTP-aware, but this is not required. It improves performance, but is not essential, especially for test purposes.

Thanks,
Wojciech

[Mirek Sobczak]

Hi Wojciech,

I've found fully managed switch. Ruggedcom 2100
It has following config:

https://www.dropbox.com/s/p5ej9v2rymo1f6n/rugg_igmp.png?dl=0
How should set it?

Mirek

[Wojciech Owczarek]

Just test it and see if it works.

As far as I remember, Ruggedcom specifically excludes the 224.0.1.129 multicast group (PTP) from IGMP so it will always flood PTP to all ports in the same VLAN, so PTP should work anywhere. If you have more questions, just theck the Ruggedcom documentation and read about IGMP. If you only have one switch on your network and no routers, you should probably set Ruggedcom to IGMP Active mode so that it becomes an IGMP querrier, but then again, for PTP there should be no difference.

Thanks,
Wojciech

[Mirek Sobczak]

Thanks
Mirek

[Mirek Sobczak]

Hello,
I give up with geting work OMICRON CMC 353 connected to CMGPS 588 via managed or unmanaged switch.
Today I received another switch SMARTzynq module, FPGA powered with MES IP core and Eureka! CMC 353 synchronize with CMGPS 588 :).
CMC 353 is connected to PTP aware switch but CMGPS588 is connected via additional switch (RSG2100). Then between CMC 353 and CMGPS are 2 switches.

Switch is SMARTzynq module, FPGA powered with MES IP core. This is not commercial :).

Mirek