E2M: a scalable explicit multicast protocol for MANETs

In this paper, we propose a new scheme for small group multicast in Mobile Ad hoc Networks (MANETs) named Extended Explicit Multicast (EM), which is built on top of Xcast and introduces mechanisms to make it scalable with number of group members for a given multicast session. EM is based on the novel concept of dynamic selection of Xcast Forwarder (XF) between a source and its potential destinations. The XF selection is carried out based on group membership and the processing overhead involved in supporting the Xcast procedure at a given node. If the number of members in a given session is small, EM works just like the basic Xcast scheme with no intermediate XFs. As group membership increases, the overhead involved in supporting an Xcast session also increases. Therefore, to reduce the overhead and provide scalability, in EM nodes may dynamically decide to become a XF. This scheme, which can work with few EM aware nodes in the network, provides the transparency of stateless multicast, reduces header processing overhead and makes Xcast scalable with the number of group members.