1

Ad-Hoc Routing Protocols

Distance VectorDestination Sequenced Distance Vector

2

Outline Routing Protocol Overview Distance Vector (DV)

Route Table in Node Route Update Loop Problem

Destination Sequenced Distance Vector (DSDV) Route Table in Node Route Update ( Sequence Number ) Damping of fluctuations

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Classification of routing protocol

Ad-Hoc Mobile Routing Protocols

HybridTable-DrivenProactive

On-Demand-DrivenReactive

DSDV

CGSR

WRPZRP

AODV DSR TROA ABR

SSR

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Table V.S On-Demand

Proactive Advantage

No latency in route discovery May be appropriate for real time communication

Disadvantage Large network capacity to keep information to

update Most routing information may never be used

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Table V.S On-Demand

Reactive Advantage

Route discovery by global search Small network capacity to keep information to

update Disadvantage

Bottleneck due to latency of route discovery May be not appropriate for real time communication

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Distance Vector (DV)

Basic Routing Protocol known also as Distributed Bellman-Ford or RIP

Periodically send table to all neighbors to maintain topology

Bi-directional links are required

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Distance Vector Table Entry

Every node maintains a routing table all available destinations the next node to reach to destination the number of hops to reach the destination

CDest

.Next

Metric

…

A A 1B B 0C C 2

Dest.

NextMetri

c…

A A 0B B 1C B 3

1 2

Dest.

NextMetri

c…

A B 3B B 2C C 0

BA

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DV Routing Table Update Form

Destination MetricA 0

B 1

C 3

D 4

A B C1 2

D1

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(A, 1)(B, 0)(C, 1)

(A, 1)(B, 0)(C, 1)

Distance Vector Routing Update

CDest

.Next

Metric

…

A A 1B B 0

C C 2

Dest. Next Metric …

A A 0

B B 1

C B 3

1 2

Dest. Next Metric …

A B 3

B B 2

C C 0

BA

B broadcasts the new routing information to his neighbors

Routing table is updated

1

12

1

2

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Distance VectorCount-to-Infinite Problem

Dest.Next Metric …

… … … ...

D B 3

Dest. NextMetri

c…

… … … ...

D C 2

Dest. Next Metric …

… … … ...

D D 1

A B C1 1

D1

∞B 3

[D,2] [D,2]

[D,3]

4

[D,4] [D,4]

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Destination Sequenced Distance Vector (DSDV)

Based on bellman-ford algorithm (DV) A Table Driven protocol Every node maintains a routing table Each node periodically broadcast routing updates

Guarantees loop freedom Each entry of the table marked with a sequence

number assigned by the destination node

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DSDV Table Entry (1/2)

Destination Next Metric Seq. No Install Time

Stable Data

A A 0 A-550 001000 Ptr_A

B B 1 B-102 001200 Ptr_B

C B 3 C-588 001200 Ptr_C

D B 4 D-312 001200 Ptr_D

A B C1 2

D1

Node A Routing Table

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DSDV Table Entry (2/2)Destination Next Metric Seq. No Install Time Stable Data

A A 0 A-550 001000 Ptr_AB B 1 B-102 001200 Ptr_BC B 3 C-588 001200 Ptr_CD B 4 D-312 001200 Ptr_D

Seq.No : Sequence number originated from destination Ensures loop freeness

Install Time: Time when the entry was made Used to delete stale entries

Stable Data: Pointer to a table holding information on how stable a route is Used to dampen fluctuations in network

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DSDV Routing Table Update Form

Destination Metric Seq. No

A 0 A-550

B 1 B-102

C 3 C-588

D 4 D-312

A B C1 2

D1

Advertised route table by A

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DSDV Route Advertisement

Dest. Next Metric Seq

A A 1 A-550

B B 0 B-100

C C 2 C-586

Dest.Nex

tMetri

cSeq

A A 0 A-550

B B 1 B-100

C B 3 C-586

Dest. NextMetri

cSeq.

A B 3 A-550

B B 2 B-100

C C 0 C-586

A B C21 1

B-102

• B increases Seq. No from 100 => 102

(A, 1, A-550)(B, 0, B-102)(C, 1, C-588)

(A, 1, A-550)(B, 0, B-102)(C, 1, C-588)

1 C-588C-588

B-102

2

B-102

C-588

1

2 A-552

(A, 2, A-552)(B, 1, B-102)(C, 0, C-588)

A-552

(A, 1, A-552)(B, 0, B-102)(C, 1, C-588)

A-552

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DSDV Loop Handling

Dest. Next Metric Seq

… … … ...

D B 3 D-100

Dest. Next Metric Seq

… … … ...

D C 2 D-100

Dest. NextMetri

cSeq

… … … ...

D D 1 D-100

A B C1 1

D1

∞

1. Node C detects broken Link: - Increase Seq. No by 1(only case where not the destination sets the sequence number - odd number)

D-101

[D,2, D-100][D,2, D-100]

2. B broadcasts=> no affect on C : higher seq. no

=> no loop -> no count to infinity

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DSDV Damping Routing Changes

Routing update occasion Periodicity Immediate

Routing update method Full dump Incremental packet

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DSDV Route Update Immediately

DSDV adopts triggered updates to make route convergence faster Send an immediate routing update when a

significant change is noticed: Link to a neighbor has broken. A routing entry with higher sequence number and an infinity

metric is received. Newly recorded routes. Improved metric for same route or larger sequence number.

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DSDV Route Update Periodically

Routing update changes are not immediately propagated Waiting some settling time

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DSDV Fluctuations Problem

A

D

QP

10 Hops11 Hops

(D,0,D-102)

D,Q,14,D-100Entry for D in A: [D, Q, 14, D-100]

D makes Broadcast with Seq. Nr. D-102

A receives from P Update (D, 15, D-102)-> Entry for D in A: [D, P, 15, D-102]

D,P,15,D-102

A must propagate this route immediately.

A receives from Q Update (D, 14, D-102)-> Entry for D in A: [D, Q, 14, D-102]A must propagate this route immediately.

D,Q,14,D-102

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DSDVSolving the Fluctuations Problem

Damping of fluctuations from triggered updates: Settling Time:

Destination address

Last settling time

Average settling time Delay sending triggered updates when things seem likel

y to change again based on past experience.

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DSDV Full/Incremental Update

Full Update: Send all routing information from own table.

Incremental Update: Send only entries that has changed.

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Reference C. P. . P. Bhagwat, “Highly Dynamic Destination-Sequenc

ed Distance Vector Routing (DSDV) for Mobile Computer,” in Proceedings of ACM SIGCOMM 94, pp.234-244, September 1994.