57When packets travel between different kinds of networks, the “gateway” devices at those transition points may need to fragment large IP packets into smaller IP packets and then re-assemble those fragments at the other end. This fragmentation and reassembly is a function of Internet Protocol, but it happens at the packet level. The task of portioning a large data block into packet-sized pieces at the very start and then reassembling those packets into a facsimile of the original data at the very end, however, is beyond the scope of IP.