A Simplified Approach to Multicast Forwarding Gateways in MANET

Simplified multicast forwarding (SMF) provides an optimized flooding mechanism in MANET environments to efficiently propagate multicast packets. The main difference between the SMF and traditional multicast routing is that no multicast tree is built and maintained, and no group membership management is needed. Therefore all the nodes in MANET receive the multicast information. However, a multicast border gateway is required in a MANET to interoperate with other multicast routing protocols in the wired domain as SMF does not make use of traditional multicast method. We propose a MANET SMF gateway implementation solution that addresses the issues encountered within the gateway configuration, such as interaction with the protocol independent multicast protocol (PIM). We will present the results of a tested single-gateway MANET implementation, and will also introduce a proposal for the multiple-gateway scenario. In the IETF MANET working group, the SMF design group also presents proposals for handling multiple gateways; they recommend to apply a <taggerID> to the multicast traffic when multiple gateways are injecting a flow into a MANET area. However this approach implies that equal multicast packets disseminated into the MANET by different gateways have different taggerlD, and hence these packets cannot be detected as duplicates. Our approach differs by preferring the use of hashing by the gateways for marking equal packets injected into the MANET, hence making these equal packets compliant for duplicate detection. This article demonstrates a successful implementation of the gateway functionality and extends its analysis by proposing a solution for the multiple-gateway configuration.