Receiving a Large Doc from TN in IS 4.6

How do we handle a large document from TN.
My setup in TN is ok and I can get Large Doc.
However when I receive the BizDoc in my IS Service, I cannot see how I can handle it.

Before I use NodeIterator, how do I extract the data of the BizDoc.

GetContentPart on the bizdoc Content return an eXML error…

Please help