iDoc Ack hoplist

Hello,

I have a B2B scenario of iDoc to iDoc when both sides have their own XI, so actually the iDoc passes the following route: R/3a->XIa->XIb->R/3b.

Now, the target system R/3b sends back an applicational acknowledgement using transaction RBDSTATE back to the source system.

As I understand, the iDoc saves it's hoplist so that the ack could go back in the reverse route all the way back to the source system.

XIb had received the ack, but the ack stops there, and not passed back to the other XI and R/3.

Any ideas ?

What special configurations do I need (R/3 partner profile, XI partner profile, comm channels ... etc.) ?

Thanks,

Elad.