Design and investigation of scalable multicast recursive protocols for wired and wireless ad hoc networks

2.4.6.2 Ad-hoc Multicast routing protocol using incrementing Id-numbers

Ad-hoc Multicast routing protocol using incrementing Id-numbers AMRIS [68] is a tree-
based multicast ad hoc routing protocol, designed to run independently of underlying routing
protocol. It builds a group-shared tree for multicast packet delivery. The key idea for AMRIS
is the use of multicast session member id msm-id. The msm-id is used to direct the flow of
data and indicate the logical level of nodes in the multicast shared tree. The root will get the
smallest msm-id within the members of the group; this special rooted node is called s-id. To
construct a group-shared tree, the s-id broadcast a new-session packet contains its msm-id.
Neighbouring node receiving this packet will create there own msm-id which should be
greater than the received msm-id but not consecutive. This propagation process is repeated
by the neighbour nodes so that the msm-id’s get greater for the nodes far from the s-id.

Like other multicast tree-based routing algorithms, when a node needs to join the group, it
sends Join-Req to its potential parent which has smaller msm-id. If the parent node is a group
member, it will respond by a Join-Ack message, otherwise it will forward the message to its
potential parents. As soon as the Join-Req message initiator receives a Join-Ack this means it
is now part of the multicast shared tree. Otherwise if this node received a Join-NAck or did
not receive any messages within a predefined period of time it initiates a Branch-
Reconstruction phase until being able to join the multicast group.

2.4.7 Mesh based routing protocol

In the presence of high mobility in the network, the tree-based multicast structure will not
perform optimally because it is fragile and requires to be reconfigured frequently.
Reconfiguration will incur large control traffic. Furthermore, the traffic will be enforced to
stop until the reconfiguration is finished and which may cause a delay and a loss of data
packets.

Mesh-based multicast routing protocols have overcome these drawbacks. At mesh-based a
construction of mesh for each group offers redundant paths among the group members. The
subsection will give brief description of the most common mesh-based multicast ad hoc
protocols.

27

<<   38   39   40   41   42   43   44   >>

More intriguing information