Regarding communication channel
we will not create communication channel while
using HTTP/Idoc Adapter. but why should we require comm channel while receiver is SAP system?
IDoc Adapter resides on ABAP stack and hence can communicate directly with Integration Server, for the conversion from IDoc to IDoc XML.Communication Channel is used for communication with the Integration Server which is obtained directly in case of IDoc .Hence Sender idoc adapter is not required and therefore no Sender Agreement.
In case of IDOC adapter as receiver to tell the XI where he should
send the data - there are many systems to which we can connect our XI and somewhere there has to be an object which will tell thx XI "where to" -> which RFC destination should it use.