Query Control Mechanisms for the Zone Routing Protocol (ZRP) - - PowerPoint PPT Presentation

9/3/98 SIGCOMM '98 1

Query Control Mechanisms for the Zone Routing Protocol (ZRP)

Zygmunt J. Haas and Marc R. Pearlman Wireless Networks Laboratory Cornell University

9/3/98 SIGCOMM '98 2

Agenda

◆ Introduction -

Routing in Mobile Ad-Hoc Networks

◆ The Zone Routing Protocol (ZRP) ◆ Query Control Mechanisms ◆ Simulation Description ◆ Results ◆ Conclusions

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Mobile Ad-Hoc Networking

◆ Rapidly deploy a regional (~ 100 m - 100 km)

network of mobile hosts, anywhere.

◆ Why? Coordinate Efforts of Distributed Systems – military (battlefield communications) – law enforcement – construction – emergency response

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Mobile Ad-Hoc Networking

B A D C E F

• no infrastructure !
• short range direct communication:

A-B , A-C

• nodes act as relays: multihop routing:

A-D-E-F

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Traditional Routing Schemes

◆ Proactive (i.e. distance vector, link state)

– maintain up-to-date view of network – extremely high traffic – most routes are not used

◆ Reactive (i.e. route query - response)

– acquire routes on demand – high traffic – route query delays

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A Hybrid Approach: Introducing the Routing Zone

Each node:

◆ Proactively tracks topology within its own routing zone ◆ Reactively acquires routes to nodes beyond routing zone

by querying between overlapping zones

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Anatomy of a Routing Zone

Routing Zone Radius: ρ (hops)

S

Neighbor Node Peripheral Node

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Bordercasting

flooding: 30 transmissions bordercasting: 20 transmissions

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Route Discovery Example

1) S-X-Y: terminates because Y has no peripheral nodes 2) S-A-B-E-A: terminates because thread returned to A 3) S-A-B-C: successful discovery ! S X Y A B C D E

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Benefits of Routing Zones

◆ Proactive: maintain routing zone

– routing traffic significantly reduced – routes used more often

◆ Reactive: query only peripheral nodes

– fewer query packets – shorter query packets * – reduced delay – routes more robust

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Routing Zones Overlap

Overlapping Zones May Lead to Excess Control Traffic

thread loops back onto a zone which it already queried. thread enters a zone previously queried by another thread

S

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Encourage Outward Propagation

• f Queries

◆ Terminate threads that return to a queried node

(not strong enough)

◆ Terminate threads that return to a queried zone

– threads that loopback on themselves – threads that overlap with other threads

◆ Prevent overlap

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Query Control Mechanisms

Terminate threads when they appear in previously queried zones

– Query Detection (QD)

intermediate nodes can detect passing threads

– Early Termination (ET)

intermediate nodes can terminate previously detected threads

previously detected query w/o QD w/ QD

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Query Control Mechanisms (cont’d)

Special Case: thread loops back on itself – Loopback Termination (LT) (100% effective)

use accumulated route to identify loopback condition

S A B

query returns to S’s routing zone

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Query Overlap Prevention: Selective BorderCasting (SBC)

full bordercasting selective bordercasting

Cover a given set of “outer” peripheral nodes with the fewest “inner” peripheral nodes

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Implementing Selective Bordercasting

◆ Extended Routing Zone (at least 2ρ hops):

◆ For each received query packet . . .

– Compute “best” SBC assignment – Send SBC assignments

Do the benefits offset the cost?

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Simulation Model

1.5 k m 1.5 km dxmit dxmit 100m # nodes 500 v 10 - 75 m/s ρ 1-10 hops Rquery 0.1 - 10 queries/sec

Variable Simulation Parameters Static Simulation Parameters

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routing zone radius (ρ) traffic (ID fields/sec) IARP Traffic per m/s

1 2 3 4 5 6 7 8 9 10 50 100 150 200 250 300 350 400 450

Full Bordercasting Selective Bordercasting

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traffic (ID fields/sec · 1000)

1 2 3 4 5 6 7 8 9 10 10 20 30 40 50 60 70 80 90 100

QD1−LT−ET QD2−LT−ET SBC−QD1−LT−ET None

IERP Traffic per Route Discovery routing zone radius (ρ)

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routing zone radius (ρ) traffic (ID fields/sec · 1000) Total ZRP Control Traffic

1 2 3 4 5 6 7 8 9 10 0.5 1 1.5 2 2.5 3 3.5 4

QD1−LT−ET QD2−LT−ET SBC−QD1−LT−ET

v = 10 [m/sec] Rquery = 0.1 [query/sec]

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Call to Mobility Ratio (CMR) Routing Zone Radius (ρ) Optimal ZRP Configuration

10

1

10

2

1 2 3 4 5 6 7 8

QD1−LT−ET QD2−LT−ET SBC−QD1−LT−ET

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Conclusions

◆ ZRP can perform worse than flooding without proper

query control mechanisms.

◆ QD, ET and LT provide significant improvements

compared with purely reactive (ρ = 1) and purely proactive schemes (ρ → ∞).

◆ Optimal ZRP radius is an increasing function of the

Call-to-Mobility Ratio (CMR).

◆ Use of SBC depends on delay and computational

complexity considerations.