Mobile IP is the basic solution to provide host mobility, whereas network mobility refers to the concept of collective mobility of a set of nodes. In the simplest scenario, a mobile network moves as a single unit with one mobile router (MR) that connects it to the global Internet. Also, multiple mobile networks can be nested in a hierarchical form, e.g., a wireless personal area network (PAN) in a vehicular network. In a nested mobile network, multiple MRs form a tree hierarchy in which the root MR is called the top-level mobile router (TLMR). Nested mobile networks exhibit the pinball routing problem, which becomes worse in proportion to the number of nested levels in the hierarchy. To solve this problem, we propose a routing optimization scheme using a tree information option (ROTIO) that extends the NEMO basic support protocol. In the ROTIO scheme, each MR in the nested mobile network sends two binding updates (BUs): one to its home agent and the other to the TLMR. The former BU contains the TLMR's home address, while the latter contains routing information between the issuing MR and the TLMR. This alleviates the pinball routing problem significantly. Now, a packet from a correspondent node only needs to visit two transit nodes (the home agents of the MR and the TLMR), regardless of the degree of nesting. Moreover, the ROTIO scheme provides location privacy and mobility transparency. We also extend ROTIO to perform routing between two mobile network nodes inside the same nested mobile network more efficiently and to substantially reduce the disruption when a mobile network hands off.

By means of network mobility (NEMO) support, users can organize their various communication devices into a network, called a mobile network. In a mobile network, the mobile router provides the connectivity to the Internet and mobility management transparency for the rest of the mobile nodes in the mobile network. So, it is important for the mobile router to assure reliable communications and a high data rate for the group of nodes behind it. In support of broadband wireless communications, the use of multiple mobile routers would allow the transfer of large volumes of data to a group of mobile nodes. This paper addresses the protocol issues arising from the use of multiple mobile routers, and analyzes the influence of mobility on load sharing and session preservation when there are multiple mobile routers. Simulation results with different configurations show that session preservation and load sharing schemes are influenced by application mobility behavior and wireless access technologies.