Also known as “Deep-DPI”, Cross Packet Inspection technology (XPI) is achieving packet and payload reassembly. This technology is used in the OSS industry to fit the specificity of mobile data.
For example, an HTTP GET can be spread in 3 packets, a MMS payload in 120 packets. XPI is inspecting the first packet, analyzing its content and retrieving information that links it to another packet to reassemble the complete GET request.
On the hardware level, because of its buffering needs, XPI is very demanding in memory & CPU resources. Not only does the XPI engine needs to reassemble information at the application layer and at each of the lower layers: (IP fragments, GTP fragments, TCP, etc...) but it also needs to achieve the management of packet retransmission and out of order packets.
Cross Packet Inspection is used by higher level technologies such as Cross Session Inspection (XSI) and Deep Session Inspection (SPI).
