INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIAKulliyyah of Engineering

Department of Electrical and Computer Engineering

Operation and performance of MAODV(Multicast Ad Hoc On Demand Distance Vector)

ADVANCED COMPUTER COMMUNICATION NETWORKS

ECE 6103SEMESTER I (10/11)

BYNUURUL IFFAH CHE OMAR (G1017674)

 SUBMITTED FOR

PROF. DR. FARHAT ANWAR

Presentation Outline

INTRO• Objecti

ve• Introdu

ction

OPERATION• Messag

es• Operati

on

PERFORMANCE• Compar

ison• Limitati

ons

CONCLUSION• Conclu

de• NS2

(not done)

Objectives

• To review the multicast extension of AODV.• To obtain background knowledge on wireless

network.• To enhance and improve knowledge regarding

data communication.

MAODV : Where am I?

Ad-hoc network routing protocols

Table driven/ proactive

DSDV WRP CGSR STAR

On demand/ reactive

ABR DSR TORA AODV MAODV

CBRP

Hybrid

ZRP

Why MAODV?

Multicast routing is more challenging in ad hoc networks compared to wired networks due to the dynamic topology changes in the network [12]. This is due to several reasons and some which are:• Node motion and wireless propagation

variability • Wireless network bandwidth limitation • Limited node energy resources available.

MAODV: Definitions(Multicast Ad Hoc On Demand Distance Vector protocol)

• Multicast is a single transmission of a message to a specific group of destination computers simultaneously from the source creating copies automatically in other network elements. Differ with broadcast.

• Ad hoc network is a collection of nodes that communicate with each other without fixed infrastructure [7] Ad hoc is Latin meaning "for this purpose." Ad hoc networks therefore refer to networks created for a particular purpose.

• On-demand according to [4], is defined as reacting to changes in the environment only when necessary. An on-demand protocol or reactive protocol establishes routes between nodes only when they are required to route data packets.

• Distance Vector routing protocol uses the Bellman-Ford algorithm to calculate paths. It requires that a router informs its neighbors of topology changes periodically.

MAODV Advantages

• Discovers Multicast routes on demand and purposely used by mobile nodes in an ad hoc network.

• It offers quick adaptation to dynamic link conditions, low processing and memory overhead and low network utilization [10].

• Moreover, MAODV creates bi-directional shared multicast trees connecting multicast sources and receivers. – Can move forward or backward or duplex communication

system where a system composed of two connected parties or devices that can communicate with one another in both directions.

Intro to its Messages

Exploits four types of messages. • The Route Requests (RREQs) • Route Replies (RREPs) • Multicast Activation (MACTs)• Group Hellos (GRPHs)

Sending a RREQ

= Node issuing request to join

oConsult its Group Leader Table, based on entryo Set ‘J’ if node wishes to join the multicast groupo If nodes not know leader, Dest. address = Address of

Multicast Group & broadcast RREQ without MGLExo If nodes knows leader, place group leaders address in

MGLEx & unicast to next hop to the destination

MGLEx = Multicast Group Leader Extension

Receiving a RREQ

Node issuing request to join

oNode checks “J” flag, if setoNode can only respond if it is a member of Multicast

tree of MG or node’s MGSN > MGSN in RREQ

MGL = Multicast Group Leader

o If “J” flag not setoNode can only respond if it has unexpired route to MG

and node’s MGSN > MGSN in RREQ

Waiting for a RREP

Node issuing request to join

oNode waits for RREP oMay resend RREQ up to RREQ_RETRIES additional timeso If no RREP within RREP_WAIT_TIME of unicast RREQ to

leader, node broadcast subsequent RREQs for MG.o If RREP not received after RREQ_RETRIES, assume no

other members in group , so it then becomes MGL (if wanting to join group) or drop packet and abort session. MGL = Multicast Group Leader

Control Route Request Broadcast

• Prevent unnecessary boadcast of RREQs– Source node use expanding ring search technique• After RREP received, Hop Count to group leader in RREP

packet is remembered as the Last Hop Count, LHC in that nodes routing table• When require new route to this Multicast Group, RREQ

IP header’s TTL = initially set to LHC + TTL_INCREMENT• Thus, TTL incremented by TTL_INCREMENT until

TTL_THRESHOLD reached.

Brief Summary Operation of MAODVhttp://code.google.com/p/typecast-routing/wiki/MAODVOverView

• The core of the MAODV protocol is about how to form the tree, repair the tree when a link is broken, and how to merge two previously disconnected tree into a new tree.

• All members of a multicast group are formed into a tree • The root of the tree is the group leader. • Multicast data packets are propagated among the tree. • There are four types of packets in MAODV: RREQ, RREP,

MACT and GRPH.

o A node broadcasts a RREQ when o it is a member node and want to join the treeo it is a non-member node and has a data packet targeted to the

group. o When a node in the tree received RREQ, it responses with RREP using unicast. o Since RREQ is broadcasted, there may be multiple RREPs received by the

originating node.o The originating node should select one RREP that has the shortest distance to

the tree and unicast a MCAT along the path to set up a new branch to the tree.

o GRPH is the group hello packet, it is periodically broadcasted by group leader to let the nodes in the tree to update its distance to the group leader.

Parameter Metrics1. Packet Delivery Ratio: The fraction of packets sent by the multicast

application that are received by the multicast receivers.

2. Control Packet Overhead: The total number of control packets originated

and forwarded by the protocol.

3. Normalized Packet Overhead: The number of control and data

transmissions performed by the protocol per successfully delivered data

packet.

4. End-To-End Delay: The time between the transmission of a data packet

from a multicast source and the time of its reception by a multicast

receiver, averaged over all packets.

Performance Analysis Comparison

CLICK MEMy Compilation

MAODV: Comparison with ROMANT

• Individual links are repaired only when broken. • over a period of time due to the random movement of nodes, • making the tree susceptible to more link breakages.

On the other hand, the number of broken links in ROMANT is much lower, because an optimal tree is reconstituted during every core announcement interval, which is less than the average link life.

So, few links in ROMANT require any repairing. Plus, even when a link breaks, the link repair scheme in ROMANT is very efficient. [22]

Figure 12: Packet Delivery Ratio Vs Mobility

MAODV: Comparison Graphs• ROMANT is hardly affected by the number of senders. The

performance of MAODV is very similar to ROMANT's, and is not affected by the number of senders, given that it is a shared-tree approach. [22]

Figure 13: Control Packet Overhead Vs Mobility

MAODV: Comparison GraphsMAODV shows a very good performance but for 40 members, the multicast tree becomes too susceptible to perceived link breakages caused by either mobility or packets not being received due to contention in the channel. The effects of high mobility are high control packet overhead due to repeated Repair RREQ floods, and low packet delivery ratio due to a broken multicast tree.[22]

Figure 14: Packet Delivery Ratio Vs Members.

MAODV: Comparison Graphs• At higher traffic loads, more hello packets are lost, which leads routers

to assume that more links break, even though no link breakages actually occur since there is no mobility in the scenario. This activates the MAODV repair mechanism, and most of the Repair RREQ's in MAODV end up being flooded throughout the network. In turn, this aggravates the congestion, which results in more apparent link breaks and more Repair RREQ floodings. As a result, control packet overhead shoots up, and packet delivery ratio plummets.. [22]

Figure 15: Packet Delivery Ratio Vs Traffic Load.

MAODV: Problem [22]

• Through the analysis, it leads to the belief that MAODV's response to fixing broken links is its greatest limitation. The fact that nodes believe that links are being broken indicates that the network is operating in stress mode and MAODV responds with RREQ, RREP and MACT packets. As a result,

• many RREQ packets may be flooded if a RREP packet is not received soon enough.

MAODV: Performance continued…

• The injection of these packets may in fact lead to more apparent link breaks due to the loss of more hello packets in collisions, which in turn leads to the injection of more RREQ, RREP and MACT packets, in an attempt to fix these new link breaks.

• As a result of this cyclic nature of congestion, there is sharp decrease in packet delivery ratio and a sharp increase in control overhead as the network crosses a certain “stress threshold”.

Proposed Solution

In ROMANT (Robust Multicasting in Ad hoc Networks using Trees), nodes receiving core announcements from two cores simply disregard the messages from the core with the lower address. Eventually, the core with a lower address receives the core announcement from the core with a higher address and stops core announcements. This kind of merging is called “passive merging” as opposed to the “active merging” of MAODV.

R. Vaishampayan and J. J. Garcia-Luna-Aceves, "Robust Tree-based Multicasting in Ad hoc Networks," Proc 2004 IEEE International Conference on Performance, Computing, and Communications, IPCCC, Phoeniz, AZ, USA, , pp. 647-652 2004.

Conclusion

• The objectives are achieved which are:• To review the multicast extension of

AODV.• To obtain background knowledge on

wireless network.• To enhance and improve knowledge

regarding data communication.

Hands On Simulation on NS2

• MAODV simulation in NS-2• http://kunz-pc.sce.carleton.ca/Thesis/maodv-code.zip• http://kunz-pc.sce.carleton.ca/Thesis/maodv-scripts.zip• http://kunz-pc.sce.carleton.ca/Thesis/maodv-ns-2.26.pdf• Getting the write Tool : Ns-allinone

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