ACI streched fabric, QSFP-40G-SR4 connection over WDM

[krueffer]

Hi,

I am trying to setup a streched ACI fabric over DWDM. I am using QSFP-40G-SR4 on both sides. Each of the four broken out 10G SR lanes is connected to an independent DWDM lane equipped with a 10GBase-SR client interface. 

The connection does not come up. The DWDM provider says the DWDM is fine. We could proove this by plugin in 10G SR interfaces on each end and the links came up. Additionally we tested the connection with break out cables locally between spine and leaf and it work well.

I am aware, the the four 10G lanes of QSFP-40G-SR4 are compatible with 10GBase-SR to ensure interoperability.

But is there a compatibility list with DWDM equipment, has this been tested? Is there anything else to keep in mind?

regards

Knut

[olgerps]

I have the same problem

[krueffer]

In the meantime we were able to resolve the problem. The issue was caused by the DWDM service. It was setup in a fashion not fitting the purpose. Generally speaking the four lanes need to be transported independently and along the same fibre path. the reason is, the physical delay must be nearly the same for all "colours". If this is not the case, the receiver is not able to assemble the 40G signal correctly. Our provider did combine the 4 x 10 G lanes in one big 100G pipe along with other services. (this does safe lambdas on the DWDM) This did screw the link. As soon es they transmitted the four lanes separatly everything was fine. You should not use the enterprise class transceivers (the cheaper ones) for such setups, because they have less buffer. it may work but it may not. And it may stop working sometime. In case you need more information email me: krueffer@itris.ch.

Knut