A Framework for Delivering Multicast Messages in Networks With Mobile Hosts

To accommodate mobile hosts (MHs) within existing data networks, the static network is augmented with “mobile support stations” (MSSs) that communicate directly with MHs, usually via wireless links. Connectivity of the overall network changes dynamically as MHs connect to the static network from different “locations” (MSSs) at different times. Compared to their desktop counterparts, mobile hosts face a new set of constraints namely, low bandwidth of the wireless links, tight constraints on power consumption and a significantly lower computing capability. Thus, even without considering failures, integration of mobile computers within existing networks pose a new set of problems. In this paper, we look at the problems associated with delivering multicast messages to mobile hosts. First, we identify how a mobile host’s ability to connect to different MSSs at different times, affects delivery of multicast messages and present schemes to deliver multicast messages to MHs from atleast-one location, from atmost-one location, and from exactly-one location. Next, we introduce “multicast groups” of mobile hosts wherein each multicast group is associated with a “host view”, a set of MSSs representing the aggregate location information of the group. A host-view membership algorithm is then presented and combined with the multicast scheme for exactly-once delivery. As a result, to deliver a multicast message to a specified group, copies of the message need be propagated only to the MSSs in the group’s host-view.