Source determination for backend service in request/SC

We have created a contract in SRM5.0 for backend service & local(SRM) service

Source is getting determined for local(SRM) service while creating shopping cart/request.

<b>But source is not getting determined for backend (R/3 ECC6.0) service replicated in SRM while creating request/SC.</b>

Kindly suggest.

Rgds,

NNK