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DOA:DSR over AODV Routing for Mobile Ad

Hoc Networks

Mobile Computing, IEEE Transactions Volume 5, Issue 10, Oct. 2006

Rendong Bai; Singhal, M.;

報告 :柯竹蔚

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Outline

一、 Introduction 二、Way Point Routing Hierarchy 三、 Performance Evaluation 四、 Conclusion

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一、 Introduction(1/5)

Routing protocols can be grouped into proactive protocols and reactive protocols.

Proactive protocols propagate topology information

periodically. Reactive protocols find routes on demand.

DSR and AODV belong to the category of flat

routing protocols, all nodes are assigned the same functionalities.

Performance degrades rapidly as the network grow. Hierarchical routing protocols are developed to solve the scalability problem.

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一、 Introduction(2/5)

Cluster head-Gateway Switch Routing (CGSR) is a typical hierarchical routing protocol.

Local route maintenance activities will only affect a few neighboring clusters. Scalability is achieved.

A C E GB D

F

Q

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一、 Introduction(3/5)

In flat routing protocols , when a route breaks, typically discard the whole original route.

Actually, only a few hops are broken, but other hops

are still intact. Wastes the knowledge of the original route.

AODV, Local repair. Suitable for link failures near the destination.

Motivation: Maintaining active routes hierarchically, Route repaired locally.

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一、 Introduction(4/5)

Way Point Routing, a number of intermediate nodes on a route are selected as waypoints.

When a node on the route moves out or fails, instead of discarding the whole original route.

WPR is a lightweight scheme, CGSR and ZRP involves all nodes, hierarchy is easier to maintain.

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一、 Introduction(5/5)

CGSR, ZRP built in two way dimensions.

WPR hierarchy is built in one dimension

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二、 WAY POINT ROUTING

Comparison of AODV and DSR Packet header overhead: DSR is larger than AODV. Learning capability: DSR learn more routing

information. DSR contain complete route information.

Multiple routes: DSR is potentially to obtain multiple routes through multiple route replies.

Scalability: AODV is able to run on larger networks.

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二、 WAY POINT ROUTING

Way Point Routing Approach Waypoint nodes divide a route into segments. Forwarding nodes: Other nodes on the route.

Segment AD Segment DG Segment GJ

Ab c

D e fG h i J

IntersegmentIntrasegment

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二、 WAY POINT ROUTING

Advantages: Broken route can be fixed at the level of a segment. Length (hop count) of each segment on a route can be

different.• Nodes move slowly, longer segments can be used

• Nodes move faster, shorter segments can be used.

WPR only involves nodes on active routes.

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二、 WAY POINT ROUTING

Combining AODV and DSR in WPR Intrasegment routing: AODV Intersegment routing: DSR

Segment AD Segment DG Segment GJ

Ab c

D e fG h i J

DSRAODV

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二、 WAY POINT ROUTING

DOA Route Discovery When a source node requires a new route, it broadcas

ts an RREQinter

RREQ uniquely identified:

<Source address , Broadcast ID number> Intermediate node appends address in the RREQinter

b cA

D

A A-b A-b-c

…

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二、 WAY POINT ROUTING

DOA Route Discovery Destination divides the path into segments, generates

a RREPinter message.

Waypoint and forwarding nodes is placed into the RREPinter.

Source address is not listed because it appears as the destination.

fG h i J

RREP_interB-c-D-e-f-G-h-i-J

…

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二、 WAY POINT ROUTING

Two tables maintained by all nodes in the network:• Route cache (DSR)

• Routing table (AODV)

Route cache• < destination : source route >

• Source route only contains waypoint nodes.

Routing table• < end_node : next_hop >

• next_hop to the end node of a segment

• end_node of the current segment

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二、 WAY POINT ROUTING

When intermediate node receives RREPinter

• Waypoint node, updates route cache and routing table.

• Forwarding node, updates routing table.

To update route cache, node inserts source routes to the destination and to downstream intermediate waypoint.

RREP_inter

D e fG h i J

…< G:G >

< J:GJ >< J:J >

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二、 WAY POINT ROUTING

To update routing table, node inserts or updates

an entry in the table < end_node : next_hop > A-b-c-D-e-f-G-h-i-J, when h receives the RREPinter, it

searches the route to end node J.

For the new route, next hop is i, the hop count is 2. When the RREPinter reaches the source node that

initiated the intersegment route discovery, the source

updates both route cache and routing table.

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二、 WAY POINT ROUTING

Data Forwarding Source node inserts the source route into the header

• source route only contains waypoint nodes.

Source node processes intrasegment

routing for the first segment.

Ab c

D e…

(A) Routing table

Dest Next

A -

D b

… …

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二、 WAY POINT ROUTING

Route Maintenance Node can confirm if a packet is correctly received by

the downstream node through:• Link-level

• Passive

• Network-layer

A broken route can be repaired locally in DOA at the level of the broken segment or at the level of a few segments.

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二、 WAY POINT ROUTING

Two levels of route repairs:• Intrasegment route repair (first)

• Intersegment route repair

If Intrasegment route repair succeeds, waypoint are not changed. Source node does not need to be notified.

Intersegment route repair will be tried and it works

over multiple segments, including broken and downstream segments.

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二、 WAY POINT ROUTING

Intrasegment Route Repair When node finds the next hop node is unreachable, it

sends a RERRintra its precursor nodes.

RERRintra contains: broken link and end node of the broken segments.

Precursor node sets the state of the broken segments to invalidated.

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二、 WAY POINT ROUTING

Start node of a broken segment knows the route error, it becomes the initiator of the route repair.

Initiator broadcasts RREQintra

TTL: SEGMENT_LEN+1 During the route repair period, initiator buffers data

packets.

b cA D e f

Gh i J

u vbuffer

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二、 WAY POINT ROUTING

Intrasegment route repair may also establish a new path for the previous segment,

Intrasegment route repair at the segment DG also builds a new path for the previous segment AD.

b cA D e f

Gh i J

u vw

Broadcast RREQ

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二、 WAY POINT ROUTING

Intersegment Route Repair Three types of RERRinter message:

• REPAIR: intersegment route repair succeeded.

• BROKEN: route repair failed.

• LOOP: removes a loop on the route.

Intersegment route repair discovers a path to the end node of the segment after the broken segment

(2 * SEGMENT_LEN). When the target receives the RREQinter, it divides the

path recorded into segments.

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二、 WAY POINT ROUTING

Initiator updates its route cache, sends a RERRrepair

to the source through upstream waypoint nodes. A-b-c-D-e-f-G-h-i-J-k-L, denoted as A-D-G-J-L

Suppose segment DG is broken, A-D×G-J-L D is the initiator of the intrasegment route repair. If failed, D tries the intersegment route repair to disco

ver a path to the end node J.

D e fG h i J k L

initiator target

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二、 WAY POINT ROUTING

Suppose the route discovery succeeds,

New path from D to J, D-u-v-W-x-y-J Node D updates its route cache, sends RERRrepair

Initiator use timer Inter_CheckReplied when route repair. If failed, initiator then sends a RERRbroken

D J k L

u v W x y

e fG h i

… …

initiator target

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二、 WAY POINT ROUTING

Routing Loops Detection Upon receiving a data packet, intermediate node chec

ks its routing table < end_node : next_hop > If it has next_hop to the end node of the current segm

ent as well as to the end node of another

downstream segment.

Loop exist.

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三、 Performance Evaluation

Simulation Environment Radio bandwidth: 2Mb/s Radio range: 250m Traffic: constant bit rate (CBR)

• Source transmitted data packets four 512-byte per second

Mobility model: Speed from 0 m/s ~ 10 m/s Scalability: 100 ~ 1,400 nodes

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三、 Performance Evaluation

Scalability - Control Overhead Using hierarchy in MANET is to

reduce the routing overhead, DOA has less

control overhead

because use waypoint

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三、 Performance Evaluation

Scalability - Route Repair Success Ratio More than 80 percent of intrasegment and

intersegment route repairs succeed for all network sizes.

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三、 Performance Evaluation

Varying CBR Flows – Packet Delivery Ratio Simulations aim: Performance of DOA when the

number of CBR flows increases. CBR flows

increased from 20 to 6066%

34%

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三、 Performance Evaluation

Varying CBR Flows - End-to-End Delay DOA incurs the lowest end-to-end

delay among three protocols.

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五、 Conclusions

Way Point Routing (WPR), maintains active routes hierarchically. Divides an active route into segments.

An instantiation of WPR termed DSR over AODV. Simulation results show that DOA scales well for mo

re than 1,000 nodes, routing overhead significantly reduced.

Future work: • heuristic methods to select waypoint nodes