ADHOC– PROACTIVE AND REACTIVE
is the act of moving information across the network from a source to a
destination. It is also referred as the process of choosing a path over which
the packets are sent. The routing process usually directs forwarding on the
basis of routing tables which maintain a record of the routes to various
one intermediate node within the internetwork is encountered during the
transfer of information. Basically two activities are involved in this concept:
determining optimal routing paths and transferring the packets through an
internetwork. The transferring of packets through an internetwork is called as
packet switching which is straight forward, and the path determination could be
protocols use several metrics as a standard measurement to calculate the best
path for routing the packets to its destination that could be : number of hops, which are used by the
routing algorithm to determine the optimal path for the packet to its
destination. The process of path determination is that, routing algorithms find
out and maintain routing tables, which contain the total route information for
the packet. The information of route varies from one routing algorithm to
another. The routing tables are filled with entries in the routing table are ip-address prefix and the next hop.
is mainly classified into static routing
and dynamic routing.
1. Static routing refers to
the routing strategy being stated manually or statically, in the router. Static routing maintains a routing
table usually written by a networks administrator. The routing table doesn‗t
depend on the state of the network status, i.e., whether the destination is
active or not.
2. Dynamic routing refers to
the routing strategy that is being learnt by an interior or exterior routing protocol. This routing
primarily depends on the state of the network i.e., the routing table is
affected by the activeness of the destination.
b) Routing in Mobile Ad-hoc Networks
Ad-hoc networks are self-organizing and
self-configuring multihop wireless
where the structure of the network changes dynamically. This is mainly due to
the mobility of the nodes. Nodes in these networks utilize the same random
access wireless channel, cooperating in an intimate manner to engaging
themselves in multihop forwarding. The node in the network not only acts as
hosts but also as routers that route data to / from other nodes in network.
ad-hoc networks there is no infrastructure support as is the case with wireless
networks, and since a destination node might be out of range of a source node
transferring packets; so there is need of a routing procedure. This is always
ready to find a path so as to forward the packets appropriately between the source
and the destination.
infrastructure networks, within a cell, a base station can reach all mobile
nodes without routing via broadcast in common wireless networks. In the case of
ad-hoc networks, each node must be able to forward data for other nodes. This
creates additional problems along with the problems of dynamic topology which
is unpredictable connectivity changes.
c) Problems in routing with Mobile Ad hoc Networks
links: Most of the wired networks rely on the symmetric links which are always fixed. But this is not a
case with ad-hoc networks as the nodes are mobile and constantly changing their
position within network
Overhead: In wireless ad hoc networks, nodes often change their location within network. So, some stale routes
are generated in the routing table which leads to unnecessary routing overhead.
the major problem with mobile ad-hoc networks as links come and go depending on the transmission characteristics, one
transmission might interfere with another one and node might overhear
transmissions of other nodes and can corrupt the total transmission.
Topology: Since the topology is not constant; so the mobile node might move or medium characteristics might
change. In ad-hoc networks, routing tables must somehow reflect these changes
in topology and routing algorithms have to be adapted. For example in a fixed
network routing table updating takes place for every 30sec. This updating
frequency might be very low for ad-hoc networks.
d) Classification of Routing Protocols
of routing protocols in mobile ad hoc network can be done in many ways, but
most of these are done depending on routing strategy and network structure.
routing protocols can be categorized as flat routing, hierarchical routing and
geographic position assisted routing while depending on the network structure.
According to the routing strategy routing protocols can be classified as
Table-driven and source initiated. The classification of routing protocols is
FSR – Fish Eye State Routing ;FSLS
– Fuzzy Sighted Link state;
OLSR – Optimized Link State Routing;
DSR – Dynamic Source Routing
TBRPF – Topology broadcast based on Reverse – Path Forwarding
AODV – Ad hoc On Demand Distance Vector; HSR – Hierarchical
State Routing CGSR – Cluster Gateway Switch Rouing; ZRP – Zone Routing Protocol
LANMAR – Landmark Ad hoc Routing;
GeoCast – Geographic Addressing
and Routing LAR – Location Aided Routing Protocol; GPSR – Greedy Perimeter Stateless Routing DREAM – Distance
Routing Effect Algorithm for mobility
the Routing Information Update Mechanism :
wireless network routing protocols can be classified into three major
categories based on the routing information update mechanism. They are
1. Proactive or Table driven routing protocols
: In table drive routing protocols , every node maintains the network topology
information in the form of routing tables by periodically exchanging routing
2. Reactive or On-demand routing protocols :
Protocols that falls under this category do
not maintain the network topology information. They obtain the necessary
path when it is required by using connection establishment process. Hence these
protocols do not exchange routing information periodically.
3. Hybrid Routing Protocols :
Protocols belonging to this cateogory combine the best features of above two categories. Nodes within a certain distance
from the node concerned or within a particular geographical region are said to
be within the routing zone of the given node. For routing within this zone, a
table- driven approach is used. For nodes that are located beyond this zone is
on-demand approach is used