Nikolaos-VMeshPresentationRNP

Report
SBRC 2005
RNP Annual Workshop
Brazil
Mesh Network Design
and Implementation using
off-the-shelf Wireless
Routers and Linux
Nikolaos Tsarmpopoulos
Department of Computer and Communications Engineering,
University of Thessaly, Greece
Dedicated to
Dr. Ketsiri Kueseng
Lecturer in Materials Science
Walailak University, Thailand
Missing since 26th December 2004
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
About the research group
University of Thessaly:

Department of Computer and Communications Engineering
http://inf.uth.gr/
Distributed Computing and Software Engineering Group
Topics of Research:
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Pervasive computing
Mobile computing
Distributed systems
Peer-to-Peer systems
People involved in “VMesh” project:
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Dr. Nikolaos Tsarmpopoulos
Mr. Ioannis Kalavros
Dr. Spyros Lalis
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Purposes of VMesh Project
Design a wireless mesh network
architecture supporting all types of IPenabled devices.
Design and implement a wireless router
for building city-wide mesh networks.
Reuse low-cost, off-the-shelf wireless
routers for the purpose of building mesh
networks.
Build a testbed network.
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Testbed Networks
Can be used for the purposes of:
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Experimentation on new protocols and
technologies.
Evaluation in real world environments.
Research and Development (R&D).
Education (hands-on experience).
Building communities.
Supporting emergency services:
police, fire brigade, ambulance, rescue workers
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
“VMesh” Project Plan
1. Evaluate the social and economic factors in
building community networks.
2. Evaluate the technological factors in building
wireless testbed networks.
3. Develop the required technology.
4. Deploy a prototype testbed (proof of concept).
5. Let the users deploy the network in large scale.
6. Exploit the potential of the testbed.
7. Identify key areas for future research.
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Challenges

Cost
Hardware
Software
Deployment
Maintenance

Programmable/expandable platform
Open Source
Standards-based

Configuration
Ease of configuration

License
Radio Spectrum
Access to tall buildings
Social factors (!!!)

Deployment
Ease of deployment
Required expertise
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Challenges

Cost
Proposed Solutions
Hardware
Software
Deployment
Maintenance

Linux
IEEE 802.11b/g
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Statically assigned

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ISM Band (2.4GHz)
By end users
By end users (!!!)
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Use of Omni antennas
None!
License
Radio Spectrum
Access to tall buildings
Social factors (!!!)



Configuration
Ease of configuration

Off-the-shelf / Embedded
GPL-licensed
By end users
By end users
Programmable/expandable platform
Open Source
Standards-based





Deployment
Ease of deployment
Required expertise
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Design Requirements
Automatically adapt to changes in
topology.
Provide the means for seamless
connectivity of user terminals (without
requiring additional software).
Support multiple Internet gateways.
Support authenticated, secure access to
selected services.
Support Wi-Fi compliant products.
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Design Decisions
1. Use Optimized Link State Routing (OLSR).
2. Use of Proxy ARP function between the user
terminal and the router.
3. Use semi-automated IP address assignment.
4. Combine wireless routers with access points for
supporting typical Wi-Fi devices (PDAs, laptops).
5. Use VPN technology for controlled access to
selected network resources and services.
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
1. OLSR
Characteristics:
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Table driven (easy to implement and port).
Proactive (no initial delays for route
calculation).
Scalable: Suited for large and dense
networks with low-mobility rate.
shelf-healing (routes are periodically and
dynamically recomputed).
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
2. Proxy ARP
Functionality:
User Terminal
The router responds to all ARP
requests submitted by the user
terminal (on the Ethernet
interface) with its own MAC
Address.
The data packets transmitted
by the user terminal have the
correct destination IP address
(layer 3), and the MAC
address of the router (layer 2).
Router
MANET
Who has
<IP address> ?
<My MAC>
has <IP
Address>.
Send data
packet to
<IP address>
The router forwards the data
packets on behalf of the user
terminal.
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
ARP resolution
for next-hop
router
Send data
packet to
<IP address>
3. IP Address Assignment
Every wireless MANET node is:

Statically assigned a unique IP address on the
Wireless Interface (MANET)
On our network: 10.151.0.0/16
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Statically assigned a unique IP subnet for
non-OLSR user terminals, connected to its
LAN segment.
The 1st usable address of the subnet is assigned to
the router LAN interface. The remaining are
assigned to user terminals using DHCP.
One our network (e.g.): 10.152.0.0/27
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Router IP Configuration Example
ROUTER IP SETTINGS
10.151.0.5
10.151.0.3
10.151.0.4
10.151.0.2
10.151.0.6
Each node is assigned an IP
address on the subnet of the Ad Hoc
network.
On our network: 10.151.0.0/16
WLAN Interface
IP Address:
10.151.0.6
Subnet Mask:
255.255.0.0
LAN Interface
IP Address:
DHCP From:
DHCP To:
Subnet Mask:
10.152.0.161
10.152.0.162
10.152.0.190
255.255.255.224
WAN Interface
IP Address:
DHCP assigned
Subnet Mask:
DHCP assigned
Default Gateway: DHCP assigned
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
4. Ad Hoc + Infrastructure
Routers form a mesh
network using OLSR
protocol.
Wi-Fi Access Points
let mobile users
access a non-OLSR
segment (subnet) of
the network attached
to the Ethernet
interface of the router.
MANET
Router
Access Point
Mobile users
(non-OLSR)
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
5. VPN technology
Point-to-Point Tunnelling Protocol provides user
authentication encryption functions.
MANET
VPN Server
Router
Access Point
Protected
network
Mobile users
(non-OLSR)
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Usage Scenarios
1. MANET – LAN connectivity, 2. MANET – Wi-Fi connectivity, 3. Mobility (OLSR)
Wi-Fi compliant
hotspot
2
OLSR-capable mobile terminals
3
Wireless LAN
1
MANET
Home / Office LAN
Ethernet
Wireless Connection
Connection
(Ad Hoc mode)
Wireless Connection
(Infrastructure mode)
Ad Hoc Router
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Wireless Node Basic Requirements
802.11b/g standards based
Network interfaces:

Wireless network interface (802.11b/g)
For connecting to the MANET (backbone network)
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Ethernet network interface (LAN)
For connecting personal computers and wireless
access points
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Ethernet network interface (Ethernet)
Internet broadband connection
Linux-based firmware
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Wireless Router Architecture
((( 802.11g Radio )))
OLSR
IP Forwarding
DHCP Server
Proxy ARP
IP Forwarding
Switched
Ports (LAN)
DHCP Client
IP Forwarding
WAN Port
(public Internet)
Wi-Fi
Access Point
Optional external connection
Optional external connection
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
IP Configuration made easy (part1)
We need to configure 3 interfaces:
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Wireless interface (mesh network)
LAN interface (Ethernet)
WAN interface (connection to Internet)
2 step process:
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Each node is statically assigned a unique
identifier NodeID (integer value starting from
zero).
Each node derives all IP configuration settings
from its identifier.
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
IP configuration made easy (part2)
Wireless interface:
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echo "10.151."$(((1+$1)/256))"."$(((1+$1)%256))
Netmask: 255.255.0.0
$1 contains the node identifier (NodeID)
LAN interface:
Every LAN segment on a VMesh wireless router is
assigned an IP subnet of 32 addresses.
 LAN interface IP Address:
echo "10."$((152+($1/2048)))".“
$(((($1*32)%65536)/256))"."$((($1*32)%256+1))
 Netmask: 255.255.255.224

RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
IP configuration made easy (part3)
DHCP Server on LAN interface
“DHCP From” Address:
echo
"10."$((152+($1/2048)))"."$(((($1*32)%65536)/256))".
"$((($1*32)%256+2))
 “DHCP To” Address:
echo
"10."$((152+($1/2048)))"."$(((($1*32)%65536)/256))".
"$((($1*32)%256+30))
Netmask: 255.255.255.224

WAN interface:

DHCP assigned IP settings
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Enabling Technologies
Wireless Router Application Platform
(PC Engines WRAP®)
Low-cost 802.11g Broadcom wireless router
platform (Linksys® WRT54G/GS®)
OpenWRT Linux
(http://www.openwrt.org)
A. Tønnesen’s OLSR implementation
(http://www.olsr.org)
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
WRAP® Platform
(PC Engines GmbH)
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National Semiconductors Geode SC1100 (233 MHz)
64MBytes RAM
1 Ethernet interface (100Mbps)
1-2 Wireless interfaces (miniPCI Cards)
1 RS232 interface (we can use it for sensors)
Slot for removable CompactFlash (IDE Drive)
Thermal Zone detector
Watchdog timer
Power over Ethernet (802.3af)
Low Power Consumption (10 Watt)
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Linksys® Hardware
WRT54G (version 2.0):
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Broadcom MIPS BCM4702KPB, 125MHz, 4MB
Flash, 16MB RAM, 5 port 10/100 Ethernet switch,
802.11g Broadcom wireless chipset.
WRT54GS (version 1.0):
Broadcom MIPS BCM4712KPB, 200Mhz, 8MB
Flash, 32MB RAM, 5 port 10/100 Ethernet switch,
802.11g Broadcom wireless chipset.
New hardware versions have become available and
require updated firmware (drivers for ethernet chipset)

RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
OpenWRT-based firmware
We expanded OpenWRT to support:
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OLSR implementation (by A. Tønnesen, Th. Lopatic)
Auto-configuration scripts for:
Network interfaces, DHCP, OLSR, IP Forwarding, Proxy ARP
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Scripts for collecting performance measurements
Scripts for posting measurements via HTTP to an SQL
database
User-accessible troubleshooting web Interface for:
Displaying other 802.11 Wireless Networks
Displaying 1-hop neighbour nodes
Displaying LAN, WLAN, WAN ports configuration settings
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Deployment
WRAP Linux router
in a water-proof
case (dual WLAN)
Linksys WRT54GS
OpenWRT router
board
Roof-top
installation of
Linksys router with
15dBi omni
directional antenna
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Routing Table
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Troubleshooting Web Interface
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Experiences
Router is easily configured in a timely manner
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Firmware installation + configuration: 5 minutes
Node deployment is relatively easy
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Cabling, packaging, mounting: 2 hours
Network stability:
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Links between nodes with distance up to 300m are stable.
Stability is improved as new nodes are added in between other nodes.
Other factors: antenna, line-of-sight, interference, weather, environment.
High-gain antennas used: 8dBi (up to 300m)
Bandwidth:
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Transfer rates up to 800Kbytes/second
(DC++ file transfers during network idle times)
TCP Performance:
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TCP exhibits poor performance over multi-hop connections if one or more
links are unstable. This behaviour affects the performance of VPN
connections.
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Firmware Upgrades
There are two methods for upgrading firmware:

Partial updates
Are performed by replacing existing files with newer ones.
Tools: BASH (for shell scripts), scp (Secure FTP), wget
(HTTP), ssh (Secure Shell)
Advantage: Can be performed remotely, over an Ethernet
(LAN) or wireless connection.

Firmware replacement
Disadvantage: It currently requires physical access to the
device (access to the hardware reset button).
In newer versions of the firmware, this should be fixed,
allowing remote firmware replacement.
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Contributions and Achievements
Contributions:
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A complete network architecture for wireless
network testbeds
Implementations for two different hardware
platforms
Technical Achievements:
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Compiled firmware for easily configurable, easily
deployable, off-the-shelf wireless routers
Combined various different network technologies
to achieve seamless interoperability with mobile
user terminals
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Research Topics (1/2)
Fast, Efficient Mobility in MANETs
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Non-OLSR aware, Wi-Fi mobile devices may
roam between Access Points attached to
different wireless routers.
Workaround: The client refreshes his IP
settings (using DHCP client)
Secure, Efficient Network Management in
Ad Hoc Networks
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Automated firmware upgrades on the routers
Updating router settings
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Research Topics (2/2)
Dynamic IP configuration for:

Ad Hoc nodes
Improve TCP performance
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Investigate alternative protocols to TCP, for use over the wireless
network
Design and implement on the routers a “proxy” service.
Virtual Networks
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Use a MANET to build the infrastructure for supporting multiple
virtual wireless networks
(managed/controlled independently by ISPs)
Wi-Fi compliant Access Mechanisms on Wireless Routers.
Eliminate the need for additional hardware (Access Points).
Perimeter-based AAA
Secure mesh network backbone
RNP Workshop, 2005, Brazil
Nikolaos Tsarmpopoulos, University of Thessaly
Thank you
Project’s Web Site:
http://vmesh.inf.uth.gr/

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