Mobile Ad Hoc Routing (IV) Uses material from tutorial by Nitin Vaidya

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Mobile Ad Hoc Routing (IV) Uses material from tutorial by Nitin Vaidya

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Last Time

Finished Cache optimization for reactive protocols Preemptive Routing

Discussion: optimizing reactive protocols

Link Reversal algorithms and TORA Try to localize updates when a link breaks

Proactive protocols Like Internet routing protocols; exchange state continuously Covered OLSR (Optimized Link State Routing)

Today: wrap up ad hoc routing Coming 2 classes: TCP over wireless

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Destination-Sequenced Distance-Vector (DSDV) [Perkins94Sigcomm]

Each node maintains a routing table which stores next hop towards each destination a cost metric for the path to each destination a destination sequence number that is created by the

destination itself Sequence numbers used to avoid formation of loops

Each node periodically forwards the routing table to its neighbors Each node increments and appends its sequence number

when sending its local routing table This sequence number will be attached to route entries

created for this node

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Destination-Sequenced Distance-Vector (DSDV)

Assume that node X receives routing information from Y about a route to node Z

Let S(X) and S(Y) denote the destination sequence number for node Z as stored at node X, and as sent by node Y with its routing table to node X, respectively

X Y Z

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Destination-Sequenced Distance-Vector (DSDV)

Node X takes the following steps:

If S(X) > S(Y), then X ignores the routing information received from Y

If S(X) = S(Y), and cost of going through Y is smaller than the route known to X, then X sets Y as the next hop to Z

If S(X) < S(Y), then X sets Y as the next hop to Z, and S(X) is updated to equal S(Y)

X Y Z

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Hybrid Protocols

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Zone Routing Protocol (ZRP) [Haas98]

Zone routing protocol combines

Proactive protocol: which pro-actively updates network state and maintains route regardless of whether any data traffic exists or not

Reactive protocol: which only determines route to a destination if there is some data to be sent to the destination

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ZRP

All nodes within hop distance at most d from a node X are said to be in the routing zone of node X

All nodes at hop distance exactly d are said to be peripheral nodes of node X’s routing zone

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ZRP

Intra-zone routing: Pro-actively maintain state information for links within a short distance from any given node Routes to nodes within short distance are thus maintained

proactively (using, say, link state or distance vector protocol)

Inter-zone routing: Use a route discovery protocol for determining routes to far away nodes. Route discovery is similar to DSR with the exception that route requests are propagated via peripheral nodes.

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ZRP: Example withZone Radius = d = 2

SCA

EF

B

D

S performs routediscovery for D

Denotes route request

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ZRP: Example with d = 2

SCA

EF

B

D


Denotes route reply

E knows route from E to D, so route request need not beforwarded to D from E

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ZRP: Example with d = 2

SCA

EF

B

D


Denotes route taken by Data

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Fisheye Routing Protocol [Pei00]

Similar idea to ZRP, but fully proactive protocol

Frequency of updates varies with distance between nodes (we saw this before in DREAM)

Accomplished by changing scope of update

Frequency of updateInversely proportional

To scope

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Routing

Protocols discussed so far find/maintain a route provided it exists

Some protocols attempt to ensure that a route exists by Power Control [Ramanathan00Infocom] Limiting movement of hosts or forcing them to take detours

[Reuben98thesis]

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Power Control

Protocols discussed so far find a route, on a given network topology

Some researchers propose controlling network topology by transmission power control to yield network properties which may be desirable [Ramanathan00Infocom] Such approaches can significantly impact performance at several

layers of protocol stack

[Wattenhofer00Infocom] provides a distributed mechanism for power control which allows for local decisions, but guarantees global connectivity Each node uses a power level that ensures that the node has at

least one neighbor in each cone with angle 2/3

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Other Routing Protocols

Plenty of other routing protocols Discussion here is far from exhaustive

Many of the existing protocols could potentially be adapted for MANET (some have already been adapted as discussed earlier)

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Some Variations

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Power-Aware Routing [Singh98Mobicom,Chang00Infocom]

Define optimization criteria as a function of energy

consumption. Examples:

Minimize energy consumed per packet

Minimize time to network partition due to energy depletion

Maximize duration before a node fails due to energy depletion

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Power-Aware Routing [Singh98Mobicom]

Assign a weigh to each link

Weight of a link may be a function of energy consumed when transmitting a packet on that link, as well as the residual energy level low residual energy level may correspond to a high cost

Prefer a route with the smallest aggregate weight

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Power-Aware Routing

Possible modification to DSR to make it power aware (for simplicity, assume no route caching):

Route Requests aggregate the weights of all traversed links

Destination responds with a Route Reply to a Route Request if it is the first RREQ with a given (“current”) sequence

number, or its weight is smaller than all other RREQs received with the

current sequence number

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Signal Stability Based Adaptive Routing (SSA) [Dube97]

Similar to DSR

A node X re-broadcasts a Route Request received from Y only if the (X,Y) link is deemed to have a strong signal stability

Signal stability is evaluated as a moving average of the signal strength of packets received on the link in recent past

An alternative approach would be to assign a cost as a function of signal stability

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Associativity-Based Routing (ABR)[Toh97]

Only links that have been stable for some minimum duration are utilized motivation: If a link has been stable beyond some minimum

threshold, it is likely to be stable for a longer interval. If it has not been stable longer than the threshold, then it may soon break (could be a transient link)

Association stability determined for each link measures duration for which the link has been stable

Prefer paths with high aggregate association stability

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Geography Adaptive Fidelity [Xu01MobiCom]

Each node associates itself with a square in a virtual grid

Node in each grid square coordinate to determine who will sleep and how long

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Quality-of-Service

Several proposals for reserving bandwidth for a flow in MANET – we do not have time to discuss in detail Example: QoS routing – prefer paths that meet QoS

requirement specified in search Example: INSIGNIA and SWAN out of Cornell

INSIGNIA: Application specify their need as Base QOS (minimum) to Extended QOS (maximum) Admission control is applied to find out if the flow can be

accommodated at each hop Solutions needed to adapt to mobility, non-uniform

interference, and dynamic traffic

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Multicasting Protocols

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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

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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

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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

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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

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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)

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E

L

H

J

D

C

G

AK

N

Group leader

BN wishes tojoin the group

Route Reply (RREP)

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E

L

H

J

D

C

G

AK

N

Group leader

BN wishes tojoin the group

Multicast Activation (MACT)

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E

L

H

J

D

C

G

AK

N

Group leader

BN has joinedthe group


Group member

Tree (but not group) member

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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

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Leaving a Multicast Tree: AODV

E

L

H

J

D

C

G

A

Group leader

B

J wishes toleave the group


K

N

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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

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E

L

H

J

D

C

G

A

Group leader

B

K

N

N wishes to leavethe multicast group

MACT (prune)

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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.

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E

L

H

J

D

C

G

A

Group leader

B

K

N

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

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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

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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

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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

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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

AP

QB

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Merging Partitions: AODV 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

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A

P

Q

BHello (Q)

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A

P

Q

B

RREQ (can I repairpartition)

RREP (Yes)

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A

P

Q

BRREQ (repair)

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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

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Summary: Multicast AODV

Similar to unicast AODV

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

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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 throughput the network Periodic transmissions are used to update the routes

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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

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Assume that S is a sender node

S

T

N

D

Join Data

Multicast group member

M

C

A

B

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S

T

N

D

Join Data


M

C

A

B

Join Data

Join Data

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S

T

N

D


M

C

A

B

Join Table (S,M)

Join Table (S,C)

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S

T

N

D

F marks a forwarding group member

M

C

A

B

Join Table (S,N)

Join Table (S,N)

F

F

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S

T

N

D


M

C

A

B

Join Table (S,S) F

F

F

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S

T

N

D


M

C

A

B

F

F

F

Join Data (T)

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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)

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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

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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

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Other Multicasting Protocols

Several other multicasting proposals have been made

For a comparison study, see [Lee00Infocom]

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Geocastingin

Mobile Ad Hoc Networks

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Multicasting and Geocasting

Multicast members may join or leave a multicast group whenever they desire

Geocast group is defined as the set of nodes that reside in a specified geographical region

Membership of a node to a geocast group is a function of the node’s physical location Unlike multicasting

Geocasts are useful to deliver location-dependent information

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Geocasting [Navas97Mobicom]

Navas et al. proposed the notion of geocasting in the traditional internet

Need new protocols for geocasting in mobile ad hoc networks

Geocast region: Region to which a geocast message is to be delivered

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Geocasting in MANET

Flooding-based protocol [Ko99Wmcsa]

Graph-based protocol [Ko2000icnp,Ko2000tech]

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Simple Flooding-Based Geocasting

Use the basic flooding algorithm, where a packet sent by a geocast sender is flooded to all reachable nodes in the network

The geocast region is tagged onto the geocast message

When a node receives a geocast packet by the basic flooding protocol, the packet is delivered (to upper layers) only if the node’s location is within the geocast region

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Simple Flooding-Based Geocasting

Advantages: Simplicity

Disadvantages High overhead Packet reaches all nodes reachable from the source

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Geocasting based onLocation-Aided Routing (LAR)

[Ko99Wmcsa]

Similar to unicast LAR protocol

Expected zone in unicast LAR now replaced by the geocast region

Request zone determined as in unicast LAR

Only nodes in the request zone forward geocast packets

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Geocast LAR

X

Y

r

S

Request Zone

Network Space

BA

Geocast region

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Geocast LAR

If all routes between a geocast member and the source may contain nodes that are outside the request zone, geocast will not be delivered to that member

Trade-off between accuracy and overhead Larger request zone increases accuracy but may also

increase overhead

Advantage of LAR for geocasting: No need to keep track of network topology Good approach when geocasting is performed infrequently

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GeoTORA [Ko2000icnp,Ko2000tech]

Based on link reversal algorithm TORA for unicasting in MANET

TORA maintains a Directed Acyclic Graph (DAG) with only the destination node being a sink

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Anycasting with Modified TORA [Ko2000tech]

A packet is delivered to any one member of an anycast group

Maintain a DAG for each anycast group

Make each member of the anycast group a sink

By using the outgoing links, packets may be delivered to any one sink

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Anycasting

A FB

C E G

D

Maintain an directed acyclic graph (DAG) for each anycast group, with each groupmember being a sink

Link between two sinks isnot directed

Links are bi-directional

But algorithm imposeslogical directions on them

Anycast groupmember

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DAG for Anycasting

Since links between anycast group members are not given a direction, the graph is not exactly a “directed” acyclic graph So use of the term DAG here is imprecise

Ignoring links between anycast group members, rest of the graph is a DAG

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Geocasting using Modified Anycasting

A FB

C E G

D

All nodes within aspecified geocastingregion are made sinks

When a group memberreceives a packet, itfloods it within thegeocast region

Geocast groupmember

Geocast region

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A FB

C E

G

D

Links may have to beupdated when a nodeleaves geocast region

Geocast groupmember

Geocast region

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A FB

C

E

G

D

Links may have to beupdated when a nodeenters geocast region

Geocast groupmember

Geocast region

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Other Geocasting Schemes

[Macwan01thesis] divides space into a grid, and maintains a graph structure for each grid square. Data transmitted using grid structures for the grid squares

that intersect with the geocast region.

d

a b

e f

c

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Other Geocasting Schemes

Mesh-based geocast routing [Boleng01]

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Some Related Work

Content-based Multicasting [Zhou00MobiHoc] Recipients of a packet are determined by the contents of a

packet Example: A soldier may receive information on events within

his 1-mile radius

Role-Based Multicast [Briesmeister00MobiHoc] Characteristics such as direction of motion are used to

determine relevance of data to a node Application: Informing car drivers of road accidents,

emergencies, etc.

Mobile Ad Hoc Routing (IV) Uses material from tutorial by Nitin Vaidya

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