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 a first packet, analyzing its content and retrieve 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, the XPI engine needs to reassemble information at the application layer and at each 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).
