cmpe 257 spring 20021 cmpe 257: wireless and mobile networking spring 2002 week 5

CMPE 257 Spring 2002 1

CMPE 257: Wireless and Mobile Networking

Spring 2002

Week 5


Multicast Communication in Ad Hoc Networks

Group Communications

Conference Scenario Rescue/Disaster Scenario Battlefield Scenario …


Multicast routing classification

Table Driven - Proactive

Routing Protocols

On Demand -Reactive

CAMP/WRPM-AODV ODMRPAMRIS

AMRoute


Overview

AMRoute AMRIS ODMRP M-AODV CAMP Flooding and Variations


Multicasting

A multicast group is defined with a unique group identifier

Nodes may join or leave the multicast group anytime

In traditional networks, the physical network topology does not change often

In MANET, the physical topology can change often


Multicasting in MANET

Need to take topology change into account when designing a multicast protocol

Several new protocols have been proposed for multicasting in MANET


On-Demand Multicast Routing Protocol (ODMRP)

ODMRP requires cooperation of nodes wishing to send data to the multicast group

To construct the multicast mesh

A sender node wishing to send multicast packets periodically floods a Join Data packet throughout the network

Periodic transmissions are used to update the routes



Each multicast group member on receiving a Join Data, broadcasts a Join Table to all its neighbors

Join Table contains (sender S, next node N) pairs next node N denotes the next node on the path from the

group member to the multicast sender S

When node N receives the above broadcast, N becomes member of the forwarding group

When node N becomes a forwarding group member, it transmits Join Table containing the entry (S,M) where M is the next hop towards node S



Assume that S is a sender node

S

T

N

D

Join Data

Multicast group member

M

C

A

B



S

T

N

D

Join Data


M

C

A

B

Join Data

Join Data



S

T

N

D


M

C

A

B

Join Table (S,M)

Join Table (S,C)



S

T

N

D

F marks a forwarding group member

M

C

A

B

Join Table (S,N)

Join Table (S,N)

F

F



S

T

N

D


M

C

A

B

Join Table (S,S) F

F

F



S

T

N

D


M

C

A

B

F

F

F

Join Data (T)



S

T

N

D


M

C

A

B

F

F

F

Join Table (T,C)

Join Table (T,C)

Join Table (T,D)

F

Join Table (T,T)


ODMRP Multicast Delivery

A sender broadcasts data packets to all its neighbors

Members of the forwarding group forward the packets

Using ODMRP, multiple routes from a sender to a multicast receiver may exist due to the mesh structure created by the forwarding group members


ODMRP

No explicit join or leave procedure

A sender wishing to stop multicasting data simply stops sending Join Data messages

A multicast group member wishing to leave the group stops sending Join Table messages

A forwarding node ceases its forwarding status unless refreshed by receipt of a Join Table message

Link failure/repair taken into account when updating routes in response to periodic Join Data floods from the senders


AODV Multicasting [Royer00Mobicom]

Each multicast group has a group leader

Group leader is responsible for maintaining group sequence number (which is used to ensure freshness of routing information)

Similar to sequence numbers for AODV unicast

First node joining a group becomes group leader

A node on becoming a group leader, broadcasts a Group Hello message


AODV Group Sequence Number

In our illustrations, we will ignore the group sequence numbers

However, note that a node makes use of information received only with recent enough sequence number


AODV Multicast Tree

E

L

H

J

D

C

G

AK

NGroup and multicast tree member

Tree (but not group) member

Group leader

B

Multicast tree links


Joining the Multicast Tree: AODV

E

L

H

J

D

C

G

AK

N

Group leader

B N wishes tojoin the group:it floods RREQ

Route Request (RREQ)



E

L

H

J

D

C

G

AK

N

Group leader

BN wishes tojoin the group

Route Reply (RREP)



E

L

H

J

D

C

G

AK

N

Group leader

BN wishes tojoin the group

Multicast Activation (MACT)



E

L

H

J

D

C

G

AK

N

Group leader

BN has joinedthe group


Group member

Tree (but not group) member


Sending Data on the Multicast Tree

Data is delivered along the tree edges maintained by the Multicast AODV algorithm

If a node which does not belong to the multicast group wishes to multicast a packet

It sends a non-join RREQ which is treated similar in many ways to RREQ for joining the group

As a result, the sender finds a route to a multicast group member

Once data is delivered to this group member, the data is delivered to remaining members along multicast tree edges


Leaving a Multicast Tree: AODV

E

L

H

J

D

C

G

A

Group leader

B

J wishes toleave the group


K

N



E

L

H

J

D

C

G

A

Group leader

B

J has leftthe group

Since J is not a leafnode, it must remaina tree member

K

N



E

L

H

J

D

C

G

A

Group leader

B

K

N

N wishes to leavethe multicast group

MACT (prune)



E

L

H

J

D

C

G

A

Group leader

B

K

N

MACT(prune)

Node N has removed itself from the multicast group.

Now node K has become a leaf, and K is not in the group.So node K removes itself from the tree as well.



E

L

H

J

D

C

G

A

Group leader

B

K

N

Nodes N and K are no more in the multicast tree.


Handling a Link Failure: AODV Multicasting

When a link (X,Y) on the multicast tree breaks, the node that is further away from the leader is responsible to reconstruct the tree, say node X

Node X, which is further downstream, transmits a Route Request (RREQ)

Only nodes which are closer to the leader than node X’s last known distance are allowed to send RREP in response to the RREQ, to prevent nodes that are further downstream from node X from responding


Handling Partitions: AODV

When failure of link (X,Y) results in a partition, the downstream node, say X, initiates Route Request

If a Route Reply is not received in response, then node X assumes that it is partitioned from the group leader

A new group leader is chosen in the partition containing node X

If node X is a multicast group member, it becomes the group leader, else a group member downstream from X is chosen as the group leader


Merging Partitions: AODV

If the network is partitioned, then each partition has its own group leader

When two partitions merge, group leader from one of the two partitions is chosen as the leader for the merged network

The leader with the larger identifier remains group leader



Each group leader periodically sends Group Hello

Assume that two partitions exist with nodes P and Q as group leaders, and let P < Q

Assume that node A is in the same partition as node P, and that node B is in the same partition as node Q

Assume that a link forms between nodes A and B A

P

QB



Assume that node A receives Group Hello originated by node Q through its new neighbor B

Node A asks exclusive permission from its leader P to merge the two trees using a special Route Request

Node A sends a special Route Request to node Q

Node Q then sends a Group Hello message (with a special flag)

All tree nodes receiving this Group Hello record Q as the leader



A

P

Q

BHello (Q)



A

P

Q

B

RREQ (can I repairpartition)

RREP (Yes)



A

P

Q

BRREQ (repair)



A

P

Q

BGroup Hello

(update)

Q becomes leader of the merged multicast tree

New group sequence number is larger than mostrecent ones known to P and Q both


Summary: Multicast AODV

Similar to unicast AODV

Uses leaders to maintain group sequence numbers, and to help in tree maintenance


CAMP

Uses Mesh instead of Tree Assumes the underlying unicast routing

protocol can provide correct distance to known destination within a finite time

Ensure reverse shortest paths from receivers to sources are part of a group’s mesh

Strongly depends on the underlying unicast protocol to work correctly in presence of router failure and network partition


Core in CAMP..

Extends the basic receiver-initiated approach introduced in CBT to create multicast mesh

Core is used to limit the control traffic needed for receivers to join the group

Cores need not to be part of mesh of their group


Join the group

Is any of my neighbors a member of group ? Else send a Join Request towards a Core Only members of the group can reply with a

Join-Ack

Cores are not reachable => expanding ring search (flooding)


core

c

g h

b di

j

k


core

c

g h

b d


Ad Hoc Multicast Routing Protocol utilizing Increasing id-number(AMRIS)


..Overview

Sid initiates a multicast session by broadcasting a NEW-SESSION message

All nodes that receive NEW-SESSION generate their own “multicast session member id” (msm-id) based on the value found in NEW-SESSION message , then rebroadcast NEW-SESSION with its msm-id

NEW-SESSION travels in an expanding ring fashion outwards from Sid, so nodes closer to Sid will generally have smaller msm-ids than those further away


Join the Tree

If the requesting node X has a neighbor who is already on the tree

send JOIN-REQ to that neighbor Y neighbor Y will send back JOIN-ACK to confirm now X

is its child If the neighbors are not on the tree, but have

smaller msm-id X send JOIN-REQ to one of the neighbor Y


..Join the Tree

After receiving a JOIN-REQ, neighbor Y sends out its own JOIN-REQ

If the parent node Y can successfully join the tree, then it sends a JOIN-ACK to X , otherwise, it will sends a JOIN-NACK to X

X will send a broadcast JOIN-REQ with limited ttl range, in turn will trigger all the nodes within that range will send out their JOIN-REQ

X might possibly receive several JOIN_ACK from its potential parent . It will choose one of them and sends a JOIN-CONF to that parent


AMRoute

Bidirectional shared-tree (1 tree per group) Create a mesh to establish connectivity before

tree creation Only group sender and receiver are tree nodes

(replication/forwarding only performed by group members, and state only in tree node)

No support needed from network nodes who are not interested/capable of multicast


..Overview

Uses virtual mesh links to establish the multicast tree

As long as routes between tree member exist via mesh links , the tree need not be readjusted when network topology changes

Suffers from temporary loops and non-optimal trees


Protocol AMRoute ODMRP CAMP AMRIS

Configuration TREE MESH MESH TREE

Loop-free NO YES YES YES

Dependson Unicast

YES NO YES NO

PeriodicMessage

YES YES YES YES

ControlPacket Flood

YES YES NO YES


Simulation Results


Results Mobility

5 sources, 20 receivers 2pkts/sec


Results Mobility


Flooding for Multicast ?

MANETS are very diverse in nature Different Mobility characteristics Varying Traffic Load characteristics Varying Sender / Receiver Populations Different Network Requirements

No Single Multicast Protocol is optimal in all scenarios

ODMRP Increased Routing Overhead with increase in number

of senders Degenerates to flooding as number of senders equals

number of nodes MAODV

Low Delivery Ratio’s with increased mobility


Focus

To provide adaptive multicast service where groups can span different network types.

Requires hosts to dynamically change routing mechanisms as they move from one network to another

Interoperability among different routing protocols (Long term !!)

Adaptive Flooding ?? Flooding variations perform better than ODMRP and

MAODV under various scenarios Flooding variations are easy to interoperate


Flooding Variations

Scoped Flooding: Reduce redundant transmissions using a set of heuristics

Nodes transmit HELLO messages with neighbor information

If source node’s neighbor set is a superset then no need to rebroadcast

Alternately use received power at nodes to decide retransmission threshold

Hyper Flooding: Re-flood to increase Reliability Broadcast packets similar to flooding first time Cache received data packets In case a node acquires a new neighbor retransmit

data packets in cache


Switching Criteria

Relative Velocity based Switching Nodes Send velocity information as part of HELLO

messages Each Node computes its velocity relative to its

neighbors every HELLO_INTERVAL. Only local information is used

If average relative velocity is greater than High_Thresh, switch to hyper flooding

If average relative velocity is lower than Low_Thresh, switch to scoped flooding

Else switch to plain flooding

Low threshold = cur_min + ( avg – cur_min)/2 High Threshold = cur_max – ( cur_max – avg) /2


Network Load based Switching Use collision as the yardstick for measuring traffic Each node maintains a count of number of collisions

in current time window If number of collisions greater than High_Threshold

then switch to scoped flooding If number of collisions lower than Low_Threshold

switch to hyper flooding Else switch to plain flooding Low threshold = cur_min + ( avg – cur_min)/2 High Threshold = cur_max – ( cur_max – avg) /2


Random Mobility Scenarios

Simulation parameters 1000m x 1000m field 50 Nodes CBR Traffic 30 pkts/sec Bouncing Ball Mobility Model 3 different mobility groups consisting of 20, 15, 15

nodes Velocity 5 - 50 m/s


Results


Conference Scenario

Scenario generated using the scenario generator tool 1 speaker node, 20 nodes [audience1] , 20 nodes

[audience 2] , 9 wanderers 1000m x 1000m CBR 20 pkts/sec On-Off Traffic On time 3 secs, Off time 3 secs, 5 kbs/sec Low mobility 2-5 m/sec with pause time of 2secs


Disaster Scenario

75 Nodes 2000m x 2000m 2 choppers 0-50 m/s 2 teams of foot soldiers 0 -5 m/s 2 teams of vehicles 5-15 m/s


Disaster Scenario


Overview of Results

For Conference scenario Adaptive Flooding delivered 15-17% more packets at slightly higher overhead for ON-OFF traffic

For the Disaster scenario Adaptive Flooding delivered about 20% more data for both CBR and On-OFF Traffic at higher routing overhead

Adaptive routing mechanisms not based on flooding could possibly be used in diverse MANET scenarios


Interoperability

Nodes belonging to different network types running different routing protocols should be able to communicate with each other.

Currently working with ODMRP (mesh based) MAODV (tree based )

Use some variation of flooding to translate messages

Requires a common routing framework

cmpe 257 spring 20021 cmpe 257: wireless and mobile networking spring 2002 week 5

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