GS308P PTP LAG

[lynlin]

Hi guys, recently I bought a GS308P unmanaged switch for data collecting system. However, it is found that the lag between two devices is larger than another Linksys smart switch. In this case, the data collecting system shows "Synchonization Error". If I change the PTP subdomain, it can work for a while. But it ends with the same error. I check the lag, it reaches around 10000ns for GS308P while it is only around 20ns for Linksys switch.

I hope anyone can tell me does it mean that this switch cannot meet my system requirement?

[lynlin · Accepted solution]

Hi everyone,

Here comes the update of this issue.

I get a solution of using GS305P instead of GS308P. This solution works. It seems that the chipset has some problem in GS308P.

So, if you need to some works requiring synchronization, GS308P may not be the best choice at present.

Hope the engineers can solve it in the future product.

[XavierLL]

Hi lynlin

Welcome to our community!

A 10.000 ns delay is much bigger that what you should get in a Gigabit Ethernet Network. We tested the GS305P and the delay added should be arround microseconds. There are different reason that you can expect a similar issue:

1. Saturated Network - can you check if when you are doing the tests there are other source of traffics that are interfering the tests.
2. Retransmisions - Could happen that the packet is retransmited due to a longer MTU or a cable or port issue.
3. Mix Environment- Do all the devices connected running at 1Gbps?

Could you check if any of the above issues could be causing your issues?

Hope it helps

Xavier Lleixa

NETGAER CBU PLM

[lynlin]

Hi Xavier

Thanks for your reply!

A 10.000 ns delay is horrible, I agree, but it did happen. The problem is I tested two switches in the same condition, but GS308P performed so poor.

Saturated Network - can you check if when you are doing the tests there are other source of traffics that are interfering the tests.

-----Nope, only connected two PTP devices and one PC. Only one software was running.

Retransmisions - Could happen that the packet is retransmited due to a longer MTU or a cable or port issue.

-----Maybe it is the case, but I have to test it under the normal condition, so I cannot change.

Mix Environment- Do all the devices connected running at 1Gbps?

-----The limit of my devices is running at 100Mbps.

[XavierLL]

Hi lynlin,

Unfortunately the GS308P it's an unmanaged switch so it doesn't have any troubleshooting capabilities that we can analyse.

However could you run a wireshark with the GS308P and the Linksys and send us the packet capture so we can have a look on this?

Also if you let us know what is your environment ( PTP models, PC model, sw) we can set up a similar environment and test it.

Regards

[lynlin]

Hi Xavier,

Thanks for your reply.

In my current situation, I dont have wireshark right now (I am running in company environment, which has limited access). 

My environment is using two B&K LAN-XI data acquisition modules (Master and Slave) and one PC Fujitsu LIFEBOOK LH532, and the GS308P POE. The software is pulse labshop. I wonder is there a similar system you can find.

Regards

[lynlin · Accepted solution]

Hi everyone,

Here comes the update of this issue.

I get a solution of using GS305P instead of GS308P. This solution works. It seems that the chipset has some problem in GS308P.

So, if you need to some works requiring synchronization, GS308P may not be the best choice at present.

Hope the engineers can solve it in the future product.