Analysis of NAT-Based Internet Connectivity for Multi-Homed On- Demand Ad Hoc Networks Engelstad, P.E. and Egeland, G. University of Oslo (UniK) / Telenor R&D, 1331 Fornebu, Norway Presented by: Geir Egeland http:// www.unik.no /~ paalee / research.htm CNDS 2004 (WMC 2004) San Diego, 22.01.2004
25
Embed
Analysis of NAT-Based Internet Connectivity for Multi-Homed On-Demand Ad Hoc Networks
CNDS 2004 (WMC 2004) San Diego, 22.01.2004. Analysis of NAT-Based Internet Connectivity for Multi-Homed On-Demand Ad Hoc Networks. Engelstad, P.E. and Egeland, G. University of Oslo (UniK) / Telenor R&D, 1331 Fornebu, Norway Presented by: Geir Egeland http://www.unik.no/~paalee/research.htm. - PowerPoint PPT Presentation
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Analysis of NAT-Based Internet Connectivity for Multi-Homed On-Demand Ad Hoc Networks
Engelstad, P.E. and Egeland, G.University of Oslo (UniK) / Telenor R&D, 1331 Fornebu, Norway
– IEEE 802.11b– Linux (2.2.20 kernel)– MAC-layer filtering– Gateways with equal configuration
Best performance: 14% of sessions break due to race condition
Introduced a random delay from a uniform distribution [0,Tmax] ms in the GWs
– Share of sessions that breaks approx. 50%
Internet
External Host
GW2(NAT)
MANET
Source Node
GW1(NAT)
Intermediate Node
10
Test bed experiment (2)
0 %
50 %
100 %
0 1 2 3 4 5
Tmax (ms)
From GW1
From GW2
Sha
re o
f RR
EP
s re
ceiv
ed
14
Tmax [ms]
11
Simulation setup
Glomosim, with AODV module
IEEE 802.11, Two-Ray channel model
Traffic pattern: Constant Bit Rate (CBR), 1024 byte packets
50 nodes– Radio Range 50m, 200mx200m square
– Radio Range 10m, 40mx40m square
12
Simulation #1 Testing Race Conditions due to Route Timeout:
– Static scenario, and varying Packet Transmission Interval (PTI):– Race Conditons have a dramatic impact on performance when PTI
exceeds Active Route Timeout of AODV (of 3 sec.).
Variable Packet Transmission Interval (with fixed route timeout, fixed terrain size and no mobility)
0 %
25 %
50 %
500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Packet Transmission Interval (ms)
Ses
sio
n b
reak
ages
/Dat
a P
acke
t
Range 10
Range 50
13
Simulation #2 Network configurations/ topologies that leads to bad
performance?– When gateways are an equal number of hops away from SN– (i.e. on right hand side of figure...)
Distribution of different network configurations (with fixed terrain size and no mobility)
0 %
5 %
10 %
15 %
20 %
25 %
30 %
35 %
40 %
45 %
50 %
0 % 20 % 40 % 60 % 80 %
Session Breaks/Packet for different Network Configurations
Sh
are
of
Ne
two
rk C
on
fig
ura
tio
ns
Range 10m
Range 50m
Distribution of different network with bad performance
Pe
rce
nta
ge
of
ne
two
rks
14
Simulation #3 Testing effects of terrain size (i.e. of node density or
of ”strength” of connectivity):– Fully connected network: Probability that session breaks = 0.5– Problem decreases as terrain size increases, because probability that
gateways are an equal number of hops away, decreases.
Variable Terrain Size(with fixed route timeout, 2Kbps CBR and no mobility)
0 %
10 %
20 %
30 %
40 %
50 %
60 %
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
Size of Sides of Terrain Square (m)
Se
ss
ion
bre
ak
ag
es
/Da
ta P
ac
ke
t
Range 10
Range 50
(50) (400)(100) (350)(150) (200) (250) (300)
15
Simulation #4 Testing Race Conditions due to link breaks, by adding
mobility:– Random Way Point (with zero rest-time and variable max velocity)
– PTI = 1 sec, i.e. safely below the Active Route Timeout of AODV
Test bed experiment showed that race conditions occurs due to Proxy RREPs
Simulations showed that race conditions reduce performance in small on-demand ad hoc networks.
Race Conditions due to route timeout represents a non-negligible problem, especially for interactive applications where the packet transmission interval easily exceeds the Active Route Timeout of AODV
Race Conditions due to link breaks (e.g. caused by mobility, radio fading, etc.) is a serious problem for all sessions, independent of packet transmission intervals.
17
Proposed working solution
SN discovers that XH is not present locally after unsuccessful route establishment on MANET
SN sets a “Gateway bit” in RREQ for XH
Gateways responds with a RREP establishing route to the GW (i.e. no race conditions will occur)
RREP contains extensions with – XH’s destination IP-address – The functionality/capabilities of the gateway
SN tunnels traffic to selected GW– GW decapsulates and forwards to XH