The document discusses Ad hoc On-demand Multipath Distance Vector (AOMDV), which is a multipath extension of the AODV routing protocol for mobile ad hoc networks. AOMDV discovers multiple loop-free and disjoint paths between source and destination nodes in a single route discovery to improve fault tolerance. It provides benefits like lower end-to-end delay, higher throughput, and reduced route discovery operations compared to AODV, which is a single path routing protocol.

1. Ad hoc On-demand Multipath
Distance Vector
(AOMDV)

2. MANET
• Mobile ad hoc networks is a type of ad hoc
network that can change locations and
configure itself.
• MANETS are Mobile, they use an infrastructure-
less, dynamic network consisting of a collection
of wireless mobile nodes that communicate
with each other without the use of any
centralized authority.

4. AODV
• Ad hoc On-demand Distance Vector.
• AODV is an on-demand, single path, loop-free
distance vector protocol.
• It combines the on-demand route discovery
mechanism with the concept of destination
sequence numbers.
• AODV takes a hop-by-hop routing approach.

5. • RREQ
– Route request packet (RREQ)
– Flooding method
– When one node needs to send a message to another
node for which it does not already have a route it
broadcasts a Route Request (RREQ) message. By
sending RREQ the node is asking the network how to
get to the destination.
• RREP
– Route Reply (RREP)
– When RREQ message arrives at its destination, a
Route Reply (RREP) message will immediately get
passed back to the origin, indicating that a route to
the destination was found.
– The RREQ message contains several key bits of
information like the source, the destination, the
lifespan of the message, broadcast ID etc.

7. • RERR
– Route Error (RERR)
– RERR message is sent whenever a link break causes
one or more destinations to become unreachable
from some of the node's neighbors.
– Link failures are propagated by means of Route
Error (RERR) messages, which also update
destination sequence numbers.

8. • RREP-ACK
– Route reply acknowledge (RREP-ACK)
– RREP-ACK message MUST be sent in response to a
RREP message.
– This is done when there is danger of unidirectional
links preventing the completion of a Route
Discovery cycle.
• Timeouts
– Neighboring nodes periodically exchange hello
message.
– Absence of hello message is considered as an
indication of link failure.
– Whenthe next hop link in a routing table entry
breaks,all active neighbors are informed.

9. • Sequence Number
– To avoid using old/broken routes
– To determine which route is newer
– To prevent formation of loops

10. Multipath Routing
• Multipath routing protocol has multiple
numbers of routes between a source and
destination.
• It overcomes certain limitation of single path
routing.

11. • Multipath routing protocol gives some
benefits, such as:
– Higher utilization of bandwidth,
– Lower end-to-end delay,
– Higher throughput and
– Higher network life
• Multipath also associated with some issues
like:
– How to discover multiple paths,
– How to distribute the load among the multiple
paths
• Path discovery in multipath approach is very
much similar to single path approach.

12. • Multipath routing protocols prefers disjoint
paths.
• Paths can be disjoint in two ways:
– Node-disjoint
– Link-disjoint
• Node-disjoint paths do not have any nodes in
common, except the source and destination.
It also do not have any links in common.
• Link-disjoint do not have any links in common,
but they may have common nodes.

13. AOMDV
• Ad hoc On-demand Multipath Distance Vector
• Modified enhanced version of AODV protocol, it
belongs to on demand and reactive routing
protocol of ad-hoc wireless networks.
• Multipath extensions to AODV protocol to cope
effectively with high mobility-induced route
failures.
• Discovers multiple loop-free disjoint paths
between the source and the destination in a
single route discovery. So, a new route discovery
is needed only when all these paths fail.

14. • Causes fewer interruptions to the application
data traffic when routes fail. They also have
the potential to lower the routing overhead
because of fewer route discovery operations.
• The main ideas in AOMDV protocol is to find
loop-free and link-disjoint paths.
• AOMDV improves fault-tolerance by selecting
disjoint paths.

15. AODV versus AOMDV

17. PARAMETERS AODV AOMDV
Routing Protocol Single path routing
protocol
Multipath routing
protocol
Average End-to-End
delay of data packets
AODV has an
average delay of
175ms
AOMDV has an
average delay of
194ms
Routing Overhead low high
No. of Packets
Dropped
high low
Performance metrics low high