Yes you setup the HTTP Post and XI HTTP to use the standard SAP Data Buffer feature and this is setup in the individual action configurations to buffer data when there is a technical communication issue (ie: network is down or PI is down for maintenance)
Data Buffer - SAP Manufacturing Integration and Intelligence - SAP Library
- Retention Time in Days
- Max. Retry Count
- Retry Interval
- Processing Type
If you need more control over the buffer you can also use the standard MDO capability, introduced in MII 12.2, and I have outlined how to achieve this here in the MII Examples 12.2 project guide in the MDO section called "Communication Buffer": http://scn.sap.com/docs/DOC-1777
Sam