DoS Resilience in Ad Hoc Networks€¦ · TCP congest. window minRTO n x minRTO Time JF Outage:...

DoS Resilience in Ad Hoc Networks

I. Aad, J.-P. Hubaux and E. Knightly

MobiCom 2004, Sept. 29th 2004,

Philadelphia - PA, USA

1

Outline

Introduction and system model

DoS attacks:“Protocol-compliant” attacks: JellyFishBlackHole

The cost of counter-measures

Network performance under DoS attacks

Conclusion

2

Introduction

Significant work has been made in:

Key Establ.

General

Authentication

Group / Multic

ast

Arms ra

ce

Localisation

Cooperation

Routing

Intrusion detectio

n

Reputation

32P

erce

nta

ge

26

12

7 65 4 3

2 2

3

Introduction


Key Establ.

General

Authentication

Group / Multic

ast

Arms ra

ce

Localisation

Cooperation

Routing

Intrusion detectio

n

Reputation

32P

erce

nta

ge

We are here

0

DoS assessment

26

12

7 65 4 3

2 2

Our goal: quantify the damage of a DoS attack on anad-hoc network

3

Introduction


Key Establ.

General

Authentication

Group / Multic

ast

Arms ra

ce

Localisation

Cooperation

Routing

Intrusion detectio

n

Reputation

32P

erce

nta

ge

We are here

0

DoS assessment

26

12

7 65 4 3

2 2

Design (and study) a new class of “protocol-compliant”attacks

3

System model

Ad-hoc multi-hop network, Mobile nodes, Secure routing,

Node Authentication, 1 ID/node, Packet Authentication and

Encryption...4

System model

JF

JF: JellyFishBH: BlackHole

BH

JF

The dual role of hosts as routers introduces a criticalvulnerability!

4

Outline


DoS attacks:

“Protocol-compliant” attacks: JellyFishBlackHole



Conclusion

5

What is a "protocol-compliant" attack?

Just like any IP service, it can:

Drop packets

Reorder packets

Delay / jitter packets

6



Drop packets

Reorder packets


BUT!in a MALICIOUS way...

6



Drop packets

Reorder packets


Why use "protocol-compliant" attacks ?Detection and diagnosis are time consuming!

6

Example: the JellyFish

� ��

��

� ��

��

� ��

��

Buffer size

JF−reordering node

Pkt Recv

SrcJF

Dst

Random select

Pkt Send

� ��

��

7

Example: the JellyFish

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

1 1.5 2 2.5 3 3.5 4 4.5 5

Goo

dput

(M

b/s)

Reordering buffer size

2 hops3 hops4 hops5 hops

Reordering >3 packets reduces TCP throughput to ≈zero!7

The JellyFish

For closed-loop traffic:TCP, TFRC-like...

Passive

Hard to detect...... until after the "sting"

End-to-end control protocols infer network status fromfeedback measurements.

JF interferes with these measurements...

... to attenuate the traffic flows.8

The JellyFish

For closed-loop traffic:TCP, TFRC-like...

Passive

Hard to detect...... until after the "sting"

Species:

JF-Reorder → “multipath”

JF-drop → “congestion, buffer overflow...”

JF-Jitter (variable RTT) → “variable loads” 8

JF-drop

For wired networks: the Shrew [Kuzmanovic & Knightly]

Dropping 5% of the packets periodically (@T = 1sec)

T

Time

SrcJF

Dst

T x d%

9

JF-drop

Dropping 5% of the packets periodically (@T = 1sec)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 0.5 1 1.5 2 2.5 3

Goo

dput

(M

b/s)

Time period (s)

2 hops3 hops4 hops5 hops

... reduces TCP throughput to zero!9

JF-drop

TC

P c

on

ges

t. w

ind

ow

Time

JF Outage: ~RTT

9

JF-drop

TC

P c

on

ges

t. w

ind

ow

minRTO

Time

JF Outage: ~RTT

9

JF-drop

TC

P c

on

ges

t. w

ind

ow

minRTO n x minRTO

Time

JF Outage: ~RTT

9

JF-drop

TC

P c

on

ges

t. w

ind

ow

1 sec n x 1 sec

Time

RFC 2988

JF Outage: ~RTT

9

JF-jitter

��

JF−jitter−delay node

time

IDLE

Server with vacations

JFDst

Src

10

JF-jitter

TCP infers network/congestion status using RTT...

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 1 2 3 4 5

Goo

dput

(M

b/s)

Idle period (s)

JF-jitter

JF interferes with RTT to attenuate the TCP flow!10

The BlackHole

For non-responsive / open-loop traffic...

Passive

Forwards routing packets

"Absorbs" all data packets

Hard to detect...11

The BlackHole

MAC/PHY

UpstreamBH

DstMAC/PHY

IP IP

Data

MAC−ACK

Drop!

of MAC layerfailure

Detection

neighbor

MAC ACK avoids immediate diagnosing

11

The BlackHole

MAC/PHY

UpstreamBH

DstMAC/PHY

IP IP

Data

MAC−ACK

Drop!

of MAC layerfailure

Detection

neighbor

(zero throughput)

11

Passive ACK (PACK) [DSR]

A is sending a packet to C via B

A B C

12


A overhears B’s transmission/forward to C

A B C

12


PACK can be fooled by low-power transmissions...

A B C

12


... Or by using directional antennas!

A B C

12

Outline





Conclusion

13

Non-goal: escalating the “arms race”

Diagnosis are inevitableLocally ?End-to-end ?

Our goal: how do they perform ?14


Counter-measure parameters:

Diagnosis time → E(T ndiag)

(re)Route request → E(T nRR)

Routing protocol limitations:

Rate limiter → E(T nRL)

Let:

Flow lifetime → E(TL)

Proportion of JF → p

Path length (for recvd. pkts.) → h

15


Goodput = E(TL)

E(TL)+(E(T ndiag

)+E(T nRL

)+E(T nRR

))(1−p)−h

0

0.2

0.4

0.6

0.8

1

0 0.1 0.2 0.3 0.4 0.5 0.6

Goo

dput

Fraction of JellyFish Nodes

3 relay nodes6 relay nodes9 relay nodes

Diagnosis and rerouting times get magnified by (1 − p)−h.

(h: average hop-count, p: proportion of JF)15


Goodput = E(TL)

E(TL)+(E(T ndiag

)+E(T nRL

)+E(T nRR

))(1−p)−h

Mobility

Network size

“PACK++”

Watchdog, path-rater [Marti et al.]

Identifying “Byzantine nodes” [Awerbuch et al.]

Reputation systems [Buchegger et al., Michiardi et al.]

Rushing attack [Hu et al.]

15


16


JF

The malicious node increases its transmission range

16


JF

... to "attract" more flows, therefore increasing p!

16


Goodput = E(TL)

E(TL)+(E(T ndiag

)+E(T nRL

)+E(T nRR

))(1−p)−h

0

0.2

0.4

0.6

0.8

1

0 0.1 0.2 0.3 0.4 0.5 0.6

Goo

dput


no rushing attack2x rushing4x rushing

The rushing attack makes things even worse,exponentiating the effect with hop length!

(h: average hop-count, p: proportion of JF) 16


Goodput = E(TL)

E(TL)+(E(T ndiag

)+E(T nRL

)+E(T nRR

))(1−p)−h

0

0.2

0.4

0.6

0.8

1

0 0.1 0.2 0.3 0.4 0.5 0.6

Goo

dput


no rushing attack2x rushing4x rushing

The goodput collapses under 10% of attackers!

16

Outline





Conclusion

17

What about the network resistance?

Simulation setup:

2000m × 2000m topology

200 mobile nodes

Velocity: 0 to 10m/s

Average pause time: 10s

50 UDP flows: 500B packets / 5s, (800b/s)

Clear non-fading channel

Simulation: 100s warmup + 500s simulation

(50 simulations, 18 topologies) / point, 95% conf.intervals

18


System-wide total throughput = sum of E-2-E throughputs:

%

Sys

tem

Th

rpt.

Percentage of JF

18


System-wide total throughput = sum of E-2-E throughputs:

100%

Sys

tem

Th

rpt.

Percentage of JF

18

again ?

DoS increases the capacity of ad-hoc networks!

19

Path length for received packets

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 5 10 15 20

Pro

babi

lity

Number of hops

0 JF / 200 nodes16 JF, Grid. plac. / 200 nodes25 JF, Grid. plac. / 200 nodes49 JF, Grid. plac. / 200 nodes

After DoS: → Long paths are extinguished...

→ Short paths will survive...20


− End−to−End throughput = channel capacity− Less interference− More channel reuse





− E2E throughput = ch. capacity / 3− More interference− Less channel reuse






System throughput maximizer






System throughput maximizer

and this is what JF and BlackHoles are doing!20

System throughput

0

0.5

1

1.5

2

2.5

0 5 10 15 20 25

Nor

mal

ized

sys

tem

thro

ughp

ut

Percentage of JFs

50 1Mb/s CBR flows250 1Mb/s CBR flows

5 TCP flows

System throughput often increases after DoS!21

BUT!

0

0.2

0.4

0.6

0.8

1

0 5 10 15 20 25

Jain

’s in

dex

of fa

irnes

s

Percentage of JF

50 1Mb/s CBR flows250 1Mb/s CBR flows

5 TCP50 TCP

System becomes unfair, in favor of short paths.22

After DoS...

Network gets severely partitioned

Short flows survive

Long flows are attenuated

Aggregated system throughput may increase!

23

More in the paper...

We analyze the performance of the system when varyingthe:

Offered load

Network size

Node density

Node mobility

JF placement strategy

24

Outline





Conclusion

25

Conclusion

TCP collapses with malicious:Dropping, reordering, jitter ...

More generally, all closed-loop mechanisms arevulnerable to malicious tampering

“Protocol-compliance” makes defense moreproblematic

First paper to quantify DoS effects on ad-hoc networks:DoS increases capacity! BUT!Network gets partitionedFairness decreases→ System throughput, alone, is not enough tomeasure DoS impacts

26

PACK

PACK power

i j k i j k

27

PACK

PACK fool

i j k i j k

27

PACK

PACK directional antenna

i j k i j k

27

Reminder on TCP

TimersCong. Window

Pkt Recv(ACK recv)

Sender Receiver

Data Pkt

ACK

8x

8x

9x

Sender Receiver

Slow Start (SS)

Congest. Avoid. (CA)(cwnd > ssthresh)

b |SRTT−RTT|

SRTT = (1−a) SRTT + a RTT

RTTVAR = (1−b) RTTVAR +

SRTT+ max(G, 4 RTTVAR))

Timers

cwnd += 1/cwnd (CA)

ssthresh

RTO = max(minRTO ,

Cong. Window

Pkt Recv(ACK recv)

cwnd += 1 (SS)

1 RTT

28

Reminder on TCP

TimersCong. Window

Pkt Recv(ACK recv)

Data Pkt

Sender Receiver

28

Reminder on TCP

b |SRTT−RTT|




Timers

ssthresh

RTO = max(minRTO ,

Cong. Window

Pkt Recv(ACK recv)

cwnd += 1 (SS)

1 RTT

Data Pkt

ACK

Sender Receiver

28

Reminder on TCP

b |SRTT−RTT|




Timers

ssthresh

RTO = max(minRTO ,

Cong. Window

Pkt Recv(ACK recv)

cwnd += 1 (SS)

1 RTT

Data Pkt

ACK

Sender Receiver

Slow Start (SS)

28

Reminder on TCP

b |SRTT−RTT|




Timers

ssthresh

RTO = max(minRTO ,

Cong. Window

Pkt Recv(ACK recv)

cwnd += 1 (SS)cwnd += 1/cwnd (CA)

1 RTT

Data Pkt

ACK

8x

8x

Sender Receiver

Slow Start (SS)

28

Reminder on TCP

b |SRTT−RTT|




Timers

ssthresh

RTO = max(minRTO ,

Cong. Window

Pkt Recv(ACK recv)

cwnd += 1 (SS)cwnd += 1/cwnd (CA)

1 RTT

Data Pkt

ACK

8x

8x

9x

Sender Receiver

Slow Start (SS)

28

Reminder on TCP

28

Reminder on TCP

1 RTT

Data Pkt

ACK

Sender Receiver

Slow Start (SS)

b |SRTT−RTT|




Timers

cwnd += 1/cwnd (CA)cwnd += 1 (SS)

ssthresh

RTO = max(minRTO ,

Cong. Window

Pkt loss

Pkt Recv

T.O.)

(dup. ACKs,

(ACK recv)

Duplicate ACK

28

Reminder on TCP

1 RTT

Data Pkt

ACK

Sender Receiver

Slow Start (SS)

b |SRTT−RTT|


cwnd = 1



ssthresh = cwnd / 2

Timers

RTO = RTO x 2


ssthresh

RTO = max(minRTO ,

Cong. Window

Pkt loss

Pkt Recv

T.O.)

(dup. ACKs,

(ACK recv)

Duplicate ACK

28

Reminder on TCP

1 RTT

Data Pkt

ACK

Sender Receiver

Slow Start (SS)

b |SRTT−RTT|


cwnd = 1



ssthresh = cwnd / 2

Timers

RTO = RTO x 2


ssthresh

RTO = max(minRTO ,

Cong. Window

Pkt loss

Pkt Recv

T.O.)

(dup. ACKs,

(ACK recv)

Duplicate ACK

/ T.O. ?

28

JF-drop

TimerRetx

1s

Time

TimersCong. Window

Pkt Recv

Pkt loss

29

JF-drop

TimerRetx

1s−RTT1s

Time1s

1s

TimersCong. Window

Pkt Recv

Pkt losscwnd = 1 RTO = RTO x 2

29

JF-drop

TimerRetx

2s−RTT

1s−RTT1s

2s

Time1s

1s 1s+R

TT

Timers

Pkt loss

Pkt Recv

Cong. Window


RTO = max(minRTO,cwnd +=1 (SS)

29

JF-drop

TimerRetx

2s−RTT

1s−RTT1s

2s

Time1s

1s 1s+2

RT

T1s

+RT

T

Timers

SRTT+ max(G, 4 RTTVAR))cwnd +=1 (SS)

RTO = max(minRTO,

Pkt Recv

Pkt loss

Cong. Window

29

JF-drop

TimerRetx

2s−RTT

1s−RTT1s

2s

Time1s

1s 1s+2

RT

T1s

+RT

T

Timers

SRTT+ max(G, 4 RTTVAR))cwnd +=1 (SS)

RTO = max(minRTO,

Cong. Window

Pkt Recv

Pkt loss

29

JF-drop

TimerRetx

2s−RTT

1s−RTT1s

2s

Time1s

1s 1s+2

RT

T1s

+RT

T

Timers



Pkt Recv

Pkt loss

Cong. Window

29

JF-drop

TimerRetx

2s−RTT

1s−RTT1s

2s

Time1s

1s 1s+2

RT

T1s

+RT

T

t 0

Timers

cwnd = 1 RTO = RTO x 2Pkt loss

Pkt Recv

Cong. Window

29

JF-drop

TimerRetx

2s−RTT

1s−RTT1s

2s

Time1s

1s 1s+2

RT

T1s

+RT

T

t t +2s0

Timers

cwnd = 1 RTO = RTO x 2

0

Pkt loss

Pkt Recv

Cong. Window

29

JF-drop

TimerRetx



2s−RTT

1s−RTT1s

2s

Time1s

1s 1s+2

RT

T1s

+RT

T

t t +2s0

Timers

RTO = RTO x 2

0

cwnd = 1

Pkt Recv

Pkt loss

Cong. Window

29

JF-drop

TimerRetx



2s−RTT

1s−RTT1s

2s

Time1s

1s 1s+2

RT

T1s

+RT

T

t t +2s0

Timers

RTO = RTO x 2

0

cwnd = 1

Pkt Recv

Pkt loss

Cong. Window

t +1s0

29

Simulation results: Number of hops

0

1

2

3

4

5

6

7

502512.580

Ave

rage

num

ber

of h

ops

Percentage of JF

Baseline: 50 1Mb/s CBR flows

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DoS Resilience in Ad Hoc Networks€¦ · TCP congest. window minRTO n x minRTO Time JF Outage:...

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