Mobile Ad Hoc NETwork (MANET)

A Mobile Ad Hoc Network is formed by the association of mobile devices, usually wireless and capable of multi-hop communication among themselves even if there is no networking infrastructure available. [MANET Auto configuration Internet-Draft].

Node's mobility (arrival and departure of nodes in the network) makes it difficult to rely on a central trusted node whose role will be to allocate free unique IP addresses. The failure or departure of such central node will prevent further IP allocation.
Since there is no central networking infrastructure, MANET nodes should request from other nodes (or auto-assign) a unique identifier in order to communicate with other MANET nodes.

When building an address allocation system, the following 3 scenarios should be handled:
[Prophet allocation ...]

1. Join and leave: A mobile node joins a network and leaves forever with/without acknowledgment of departure. How to detect unacknowledged departure and reuse allocated IP address. How to allocate a unique IP address for 2 nodes joining at the same time.
2. Partition and Merge: a node or more of the MANET moves outside other's transmission range. When they move back within the transmission range, they should merge again with the MANET. What if other nodes joined and same IP addresses where allocated to them.
3. Two separated MANETs with different IP configuration merging.
   

Existing solutions can be divided into the following three categories:

1. Conflict-detection allocation: A new node selects an address from the private address space and requests approval from all nodes in the MANET. If it receives a conflict message from a node in the network, then it selects another address until the address is free, it becomes the new node's address. (Duplicate Address Detection method). These methods can handle easily scenario#1.
   
2. Conflict-free allocation: Free IP addresses are assigned to new nodes. Dynamic Configuration and Distribution Protocol is an example of conflict-free allocation algorithms which is based on dividing the address pool in two halves every time a new node joins the MANET. This insures the uniqueness of the allocated addresses. These methods can handle scenario #1 and #2 since the addresses are already different. However when it comes to dealing with scenario #3 conflicts are unavoidable. The pool addresses are taken from the private addresses range.
3. Best effort allocation: the nodes responsible for allocating new addresses attempt to provide a conflict free address to the best of their knowledge, but conflicts may still occur, say due to the same address being allocated to two joining nodes before there is time for updating the table of existing addresses. An example of best-effort allocation is MANETConf Protocol.
   

The next section describes a summary of an auto address assignment methods to MANET nodes.