jNetPcap briefly introduced an experimental feature which analyzes (in great detail) various protocols and provides Ip4 and tcp-reassembly services. The feature was deprecated fairly quickly due to some limitations of the existing jNetPcap implementation. Especially at the native level and how information is stored about decoded packet states. The existing memory management of jNetPcap turned out to be inadequate for the task and greatly complicated implementation of this feature.
This is however #1 feature requested and sought after by most users. It is currently being completely rewritten for the next generation of the jNetPcap API in the coming
2.x 1.5 releases. The expected time frame for first release of this feature is in October June of 2011. It will be decoupled from overall jnetpcap dependency and released as a separate module. Of course this module will work in conjunction with jnetpcap, the libpcap java wrapper module.