Wireless MESH Networks By: Tapu Ahmed Marshall Grillos.

Wireless MESH Wireless MESH NetworksNetworks

By: Tapu Ahmed

Marshall Grillos

Current Cellular Current Cellular TopologyTopology

Basic LayoutBasic Layout

Problems with Current Problems with Current Design Design

Single point of failureSingle point of failure

SolutionSolution

When you have a single node failure in MESH topology, the other nodes can simply “go around” to get to their neighbors.

Advantages to MESHAdvantages to MESH

Incredible amount of flexibility in Incredible amount of flexibility in session setup. session setup. All that is needed is a radioAll that is needed is a radio

Radio acts as both transmitter and receiverRadio acts as both transmitter and receiver

MESH networks can be extremely advantageous to small business owners.

Problems with MESHProblems with MESH

Distance is the primary disadvantage Distance is the primary disadvantage of MESH networksof MESH networks

Coverage area becomes a problem as well

Problems continuedProblems continued

Routing ComplexityRouting Complexity You must dynamically locate your You must dynamically locate your

neighbors.neighbors. Battery-LifeBattery-Life

Mobiles must remain “on” for a wireless Mobiles must remain “on” for a wireless MESH network to be useful. MESH network to be useful.

Why not MESH Now?Why not MESH Now?

Shannon’s Law (Spectrum Shannon’s Law (Spectrum Capacity)Capacity)

Amount of throughput that can be Amount of throughput that can be achieved depends on the level of achieved depends on the level of interference.interference.

If interference goes up, throughput If interference goes up, throughput goes down.goes down.

Mesh ProtocolsMesh Protocols

802.11 Standard802.11 Standard

Most MESH operate on this Most MESH operate on this standard since the 802.11 standard standard since the 802.11 standard is by far the most widely deployed in is by far the most widely deployed in wireless LAN. wireless LAN.

Thus it will contain: physical, MAC, Thus it will contain: physical, MAC, and link layer.and link layer.

802.11 Basic design802.11 Basic design

Source RTS Data

Destination CTS ACK

Questions to consider:

•When to initiate a route request

•When and how to buffer packets during route discovery

•When to update the lifetime of an active route

AODVAODV

Ad-hoc On Demand Distance VectorAd-hoc On Demand Distance Vector AODV is a reactive routing protocol. AODV is a reactive routing protocol. Routes to other nodes are determined Routes to other nodes are determined

only when needed. only when needed.

Source Node1 Node2 Destination

Hello

Route Request

Route Reply

Data

Route Error

X

AODVAODV

Advantages:Advantages: Since the nodes can change in and out of Since the nodes can change in and out of

the network quickly, you will not run into the network quickly, you will not run into dead endsdead ends

Uses little memoryUses little memory Good for small applicationsGood for small applications

DisadvantagesDisadvantages Inefficient when there is a large number of Inefficient when there is a large number of

routes needed and for applications that routes needed and for applications that cannot tolerate the delay of route discovery.cannot tolerate the delay of route discovery.

TBRPFTBRPF

Topology Broadcast based on Topology Broadcast based on Reverse-Path ForwardingReverse-Path Forwarding TBRPF is a TBRPF is a proactiveproactive routing protocol. routing protocol. Each node is provided with the state of Each node is provided with the state of

each link in the network.each link in the network.

Broadcast trees are updated Broadcast trees are updated automaticallyautomatically Creates a link-state design that has Creates a link-state design that has

minimal overhead.minimal overhead.

TBRPFTBRPF

Advantages:Advantages: Improved efficiencyImproved efficiency Alternate paths immediately available. Alternate paths immediately available.

Helps the quality of service.Helps the quality of service. DisadvantagesDisadvantages

Better suited for larger applicationsBetter suited for larger applications

ExtensionsExtensions

RedundancyRedundancy The meaning of “redundancy” in general network The meaning of “redundancy” in general network

architecture is a matter of degree and must be architecture is a matter of degree and must be carefully specified. carefully specified.

To reach higher levels of redundancy, you may add To reach higher levels of redundancy, you may add an additional line of fiber next to an existing one.an additional line of fiber next to an existing one.

In a mesh network, the degree of redundancy is In a mesh network, the degree of redundancy is essentially a essentially a function of node densityfunction of node density. .

A network can be deliberately over-designed for A network can be deliberately over-designed for reliability simply by adding extra nodes, so each reliability simply by adding extra nodes, so each device has two or more paths for sending data.device has two or more paths for sending data.

It can additionally be achieved by increasing the It can additionally be achieved by increasing the number of simultaneous connections a node may number of simultaneous connections a node may have. have.

Example, Simple vs. Example, Simple vs. Complex MeshComplex Mesh

A simple mesh network is one that A simple mesh network is one that requires relationships between the nodes requires relationships between the nodes or devices on the LAN. or devices on the LAN.

Devices need not all Devices need not all directlydirectly connected connected for a simple mesh for a simple mesh

Complex Mesh (Pure Mesh Complex Mesh (Pure Mesh or Logical Mesh)or Logical Mesh)

In a complex mesh, all In a complex mesh, all nodes must be connected nodes must be connected to all other nodes.to all other nodes.

The number of The number of relationships in a network relationships in a network can be represented by the can be represented by the formula N(N-1) where N formula N(N-1) where N is the number of devices is the number of devices in the network. in the network.

A complex mesh is vastly A complex mesh is vastly more redundant than a more redundant than a simple mesh.simple mesh.

This is often at the cost of This is often at the cost of higher network overhead.higher network overhead.

Mesh Networks Mesh Networks Security IssuesSecurity Issues

Another Mesh ExampleAnother Mesh Example

Dynamically configured and modified.Dynamically configured and modified. What implications on security?What implications on security? Each node acts as a router and an end user.Each node acts as a router and an end user.

Security ImplicationsSecurity Implications

Security in data transmission (much Security in data transmission (much more than typical WLAN due to more than typical WLAN due to multiple hops over wireless).multiple hops over wireless). Actually sending packets over the air.Actually sending packets over the air. Ensuring who’s receiving the packets is Ensuring who’s receiving the packets is

the intended target.the intended target. Security of Network AccessSecurity of Network Access

Ensuring everyone on the network Ensuring everyone on the network should be on the network (user should be on the network (user authentication).authentication).

User Authentication and User Authentication and Partial MeshPartial Mesh

Mesh exists Mesh exists outside of WLANoutside of WLAN

Relies on WLAN Relies on WLAN RADIUS servers RADIUS servers for for Authentication Authentication (much like (much like WLINE networks WLINE networks today)today)

What about What about purepure Mesh Mesh authentication?authentication?

Each node must have all authentication Each node must have all authentication data or connectivity to an authentication data or connectivity to an authentication agent.agent.

Generally multiple authentication agents Generally multiple authentication agents must exist for redundancy and efficiency must exist for redundancy and efficiency (number of hops).(number of hops).

ASIC security can be implemented to have ASIC security can be implemented to have pure hardware authentication of a device.pure hardware authentication of a device.

MeshDynamics suggests MeshDynamics suggests ASIC Security and “Smart ASIC Security and “Smart

Cards”Cards” ASIC - ASIC - Application-Specific Integrated Circuit: Application-Specific Integrated Circuit:

a very large scale integrated circuit (a VLSI a very large scale integrated circuit (a VLSI chip) designed for a specific customer and chip) designed for a specific customer and function (often on the basis of a function (often on the basis of a Programmable Gate Array).Programmable Gate Array).

Security chip devised for one way Security chip devised for one way authentication.authentication.

Used by Satellite TV Providers Used by Satellite TV Providers (DishNetworks, DirecTV).(DishNetworks, DirecTV).

Used by American Express (American Express Used by American Express (American Express Blue).Blue).

ASIC ContinuedASIC Continued Security chip contains application specific Security chip contains application specific

modifiable software for key decryption.modifiable software for key decryption. Card must be ‘activated’ in authentication Card must be ‘activated’ in authentication

server to receive proper decryption keys.server to receive proper decryption keys. Cards are easily changeable/upgradeable Cards are easily changeable/upgradeable

by companies.by companies. Removes the need for ‘login’ procedure.Removes the need for ‘login’ procedure. Cards can be read by wireless units (PDA, Cards can be read by wireless units (PDA,

Laptop, etc).Laptop, etc).

Secure Data Secure Data Transmission - WPATransmission - WPA

Wi-Fi Protected AccessWi-Fi Protected Access WPA is the Wi-Fi Alliance’s new security standard

that supersedes WEP (wired equivalent privacy). WPA is based on an early version of the IEEE 802.11i standard.

WPA upgrades WEP encryption with a stronger cipher, Temporal Key Integrity Protocol (TKIP) – timed keys, that fixes known vulnerabilities in the WEP encryption algorithm.

WPA also introduces stronger authentication using RADIUS as well as port-based access control based on IEEE 802.1x.

WPA contributes to network access control and secure data transmission.

Modern Day Modern Day Applications of Applications of

MeshMesh

MeshDynamics Offers MeshDynamics Offers Three-Radio Mesh Network Three-Radio Mesh Network

SolutionSolution From neighborhoods up to citywide From neighborhoods up to citywide

coveragecoverage

Services Include:Services Include:

Mobile Data, VoIP, and Public Safety Mobile Data, VoIP, and Public Safety NetworksNetworks

U.S. MilitaryU.S. Military The Pentagon, about a decade ago, set out The Pentagon, about a decade ago, set out

to design a wireless communications to design a wireless communications network that could survive a war. network that could survive a war.

One design that has emerged, in portable One design that has emerged, in portable military communications gear that has military communications gear that has been used in Afghanistan and could be been used in Afghanistan and could be used in the Iraqi theater, is called "mobile used in the Iraqi theater, is called "mobile ad-hoc" or mesh networking. ad-hoc" or mesh networking.

This provides instant up to date troop and This provides instant up to date troop and unit movements (all units are connected unit movements (all units are connected to the wireless mesh network).to the wireless mesh network).

Surveillance and tracking oppositionSurveillance and tracking opposition

IndustryIndustry

Mesh based diagnostic networksMesh based diagnostic networks Efficiency and stability monitoringEfficiency and stability monitoring Real Time DiagnosticsReal Time Diagnostics

Industry DiagnosticsIndustry Diagnostics

Mesh Networks can provide a low-cost diagnostic Mesh Networks can provide a low-cost diagnostic channel outside of normal control loops. channel outside of normal control loops.

This enables significant productivity improvements This enables significant productivity improvements where manual measurements may have previously where manual measurements may have previously been required. been required.

By regularly capturing diagnostic data, plants can By regularly capturing diagnostic data, plants can use predictive maintenance for cost savings. use predictive maintenance for cost savings.

QuestionsQuestions Q1: What problems do centralized Q1: What problems do centralized

designs present and how does a MESH designs present and how does a MESH network go about addressing those network go about addressing those problems?problems?

Q2: Would you use a proactive or reactive Q2: Would you use a proactive or reactive protocol in a large MESH environment. protocol in a large MESH environment. Why? Why?

Q3: How do you increase redundancy in a Q3: How do you increase redundancy in a Mesh network?Mesh network?

AnswersAnswers Answer1: MESH networks avoid a single Answer1: MESH networks avoid a single

point of failure which can be detrimental to point of failure which can be detrimental to centralized systems. MESH topology centralized systems. MESH topology eliminates routers, controllers, etc.eliminates routers, controllers, etc.

Answer2: You should use a proactive (TBRPF) Answer2: You should use a proactive (TBRPF) protocol since large applications cannot protocol since large applications cannot tolerate the delay of route discovery.tolerate the delay of route discovery.

Answer3: In a mesh network, the degree of Answer3: In a mesh network, the degree of redundancy is essentially a function of node redundancy is essentially a function of node density. You can increase the number of density. You can increase the number of nodes (to increase the density). Additionally, nodes (to increase the density). Additionally, it can be achieved by increasing the number it can be achieved by increasing the number of simultaneous connections a node may have.of simultaneous connections a node may have.

ReferencesReferences

http://dailywireless.org/modules.phphttp://dailywireless.org/modules.php?name=News&file=article&sid=201?name=News&file=article&sid=20100

http://www.iapplianceweb.com/storyhttp://www.iapplianceweb.com/story/oeg20040117s0019.htm/oeg20040117s0019.htm

http://home.pacific.net.au/~djames.hhttp://home.pacific.net.au/~djames.hub/mesh/routing_faq.htmlub/mesh/routing_faq.html

http://www.oreillynet.com/pub/a/wirhttp://www.oreillynet.com/pub/a/wireless/2004/01/22/wirelessmesh.htmleless/2004/01/22/wirelessmesh.html

References Cont.References Cont.

http://www.meshdynamics.com/http://www.meshdynamics.com/ http://wi-fi.org/http://wi-fi.org/ http://www.sensorsmag.com/articles/http://www.sensorsmag.com/articles/

0203/38/main.shtml0203/38/main.shtml