Juan-Antonio Cordero Philippe Jacquet Emmanuel Baccelli

Orlando, FL -- March 29th, 2012

Impact of Jitter-based Techniques on Flooding over Wireless Ad hoc Networks

Model and Analysis

31st Annual IEEE International Conference on Computer Communications

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

Motivation: Flooding over wireless ad hoc networks

Packet collisions in wireless flooding

The jitter technique for flooding

Framework: goals, assumptions, approach

Main results

Discussion

Agenda

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

Motivation

Flooding in Wireless Ad hoc Networks

Flooding

Periodic dissemination of messages over the network

Routers participating in flooding:

1) Create and transmit their own messages

2) Receive and forward messages from other routers in the network

Example:

Link-state routing: OSPF, OLSR Other…

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

Motivation

Wireless Ad hoc Networks

Wireless communication

Dynamic and unpredictably changing topology

Less available bandwidth

More updates required (in routing protocols)

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

Motivation

Wireless Ad hoc Networks

Wireless communication

Dynamic and unpredictably changing topology

Less available bandwidth

More updates required (in routing protocols)

Packet collisions in flooding !

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

A tx

Shared channel(from D)

A

BB rx

processing

B tx

CC rx

processing

C tx

systematic collision

Wireless flooding : Stating the problem A

B

C

D

Wireless flooding

Packet collisions in flooding

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

Wireless flooding with jitter | Intuition

A tx

Shared channel(from D)

A

BB rx

processing

B tx

CC rx

processing

C tx

random delay for C tx

random delay for B tx

The jitter technique

Jitter for flooding

A

B

C

D

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

Packet piggybacking

Wireless flooding with jitter : RFC 5148

Self-generated msg at t=t1

Received pkt at t=t0

Assigns a jitter value jto all msgs of the pkt

N=1

Extracts N-thmsg from the pkt

N-th msg needs to be forwarded?

Schedule txat t=t0+j

Scheduled tx at t=t2

Next N?

Send all msgs scheduled and not sent at t=t2

Schedule txat t=t1

t2=t1

Yes

Yes

No

No

The jitter technique

Jitter for flooding

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

Advantages

Reduction of systematic packet collisions by spreading transmissions

Reduction in the number of transmissions due to piggybacking

Drawbacks

Delay of the flooding operation

Increase of the length of the transmitted packets

Impact of jitter technique in wireless flooding

Main effects

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

System model

Packet arrival ~ punctual, homogeneous Poisson process

Instantaneous packet transmission

All packets received are to be forwarded

R

In λin

Self-generatedλg

Outλout

Impact of jitter technique in wireless flooding

Model and assumptions

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

time(in)

Arrival triggering a collecting phase

Impact of jitter technique in wireless flooding

Variables

t

t0

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

time(in) (in) (in)

…

(in)

Arrival triggering a collecting phase

Impact of jitter technique in wireless flooding

Variables

t

t1

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

time(in) (in) (in) (self)

…

(in)

D(t) ≡ avg length of collecting phase

t

Arrival triggering a collecting phase

Effective time of transmission

Impact of jitter technique in wireless flooding

Variables

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

Impact of jitter technique in wireless flooding

Average duration of collecting phase

ODE )('))(()('' tDtFtD gTin j

t x

gTin yFdydxtDj

0 0

)(exp)( General solution ( D(0) = 0 ; D’(0) = 1 )

Out-packet rate}{1 Dtin

ginout E

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

time(in) (in) (in) (self)

…

(in)

t

Arrival triggering a collecting phase

Effective time of transmission

Impact of jitter technique in wireless flooding

Variables

G(t)

Ttx(t)

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

Impact of jitter technique in wireless flooding

In-packet delays

Average in-packet cumulated delay before out-packet transmission

where

Average forwarding delay for an in-packet

)()()( tHtDtG

)(1

)()(

tD

tGtT

intx

t

Tin dxtFtDtHj0

))(1()(')('

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

Impact of jitter technique in wireless flooding

Some particular results

Uniformly distributed jitter ( RFC 5148 )

Packet delays: D(t) , Ttx(t)

Packet rate: λout(λin, λg) , λout(T)

Jm

1/Jm

pdf Tj

Jm

1

cdf Tj

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

Impact of jitter technique in wireless flooding

Delays before transmission

Ttx(t) ≡ Avg time of transmission D(t) ≡ Avg duration of collecting phase

(λin = 4 pkt/sec, λg = 0.2 pkt/sec, Jm = 1 sec)

Model results

D(t)

Ttx(t)

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

Impact of jitter technique in wireless flooding

Out-packet rate

λout ≡ Out-packet rate (pkts/sec)

(Jm = 1 sec)

λg = 0

λg = 0.9

Model results

λout

λin +λg

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

λout ≡ Out-packet rate (pkts/sec)

( λ in = 4 pkts/sec, λg = 0.2 pkts/sec )

Impact of jitter technique in wireless flooding

Out-packet rate Model results

with simulations

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

Discussion & Conclusions

Future work

Non-instantaneous packet transmissions ( packet collisions)

More jitter … less collisions ?

Network experimental results

RFC 5148 : jitter + piggybacking for flooding (OLSR, OSPF, DYMO…)

Theoretical model : additional delay D(t) vs. packet rate (λout) reduction

Generality of results

Model limitations

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

Questions ?

E-mail: cordero@lix.polytechnique.fr

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

Backup slides

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

dtdttDdtdtdtD

dxxDxftDtTPdttD

ging

t

Tjin j

)()(1)(

)()()()()(0

Transition equations for D(t) and F(t)

)()(10

)()()()()(0

tFdtdt

dxxGxftGtTPdtdttF

ging

t

Tjin j

Avg duration of collecting phase

Avg cumulative delay of in-packets arrived within a collecting phase

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

Some values…

Jitter scale (Friedman, Hay & Kliot, 2009)

For Jm = t = 10 msec, λin = 15 pkt/sec, λg = 0,25 pkt/sec,

λout = 14,2 pkt/sec (-7%)

D(t) = 9,74 msec, Ttx(t) = 8,92 msec (worst case)

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Link-state routing over MANETs: Estimating the impact of jitter techniques in wireless flooding

References

(Technical Report, 2009) R. Friedman; D. Hay; G. Kliot: Jittering Broadcast Transmissions in MANETs: Quantification and Implementation Strategies. Department of Computer Science, Technion – Institute of Technology of Israel.

(Journal, 2004) C. Adjih; E. Baccelli; T. Clausen; P. Jacquet; G. Rodolakis: Fish Eye OLSR Scaling Properties. In: IEEE Journal of Communications and Networks (JCN), Special Issue on Mobile Ad Hoc Wireless Networks, Volume 6, Number 4, pp. 343-351, IEEE, December 2004.

(Conference, 2003) T. Henderson et al.: A Wireless Interface Type for OSPF, Proceedings of the IEEE Military Communications Conference (MILCOM), pp. 137-145, Boston, MA (United States), October 2003.

(Conference, 1998) J. Broch; D. A. Maltz; D. B. Johnson; Y.-C. Hu; J. Jetcheva: A performance comparison of multi-hop wireless ad hoc network routing protocols, Proc. ACM Annual International Conference on Mobile Computing and Networking (MobiCom’98), pp. 85–97, Dallas, TX (United States), October 1998.