Download What is Wireless Mesh Network?

Mesh Networks
Sri Edupuganti
The Wireless Paradox: Lots of Wires
Internet
ETHERNET
WIRELESS
Expensive, difficult to install, and long installation time,
especially in outdoor deployments
Traditional vs Ad-hoc Network
Traditional
Mobile Ad-hoc
WLAN vs Wireless Mesh
Traditional vs Mesh Network
Evolution of Mesh
• It takes a lot of wires to build a wireless network
• If all you have is a hammer every problem looks like a nail
– i.e. AP’s alone are not the answer
• The original embodiment of mesh as a wireless peer to peer
version of the Internet is incomplete: We moved the mesh “one
node in”.
– i.e. clients are not part of the mesh
• Wireless backhaul Mesh is not the same as WiFi
• Mesh can be the glue to join separate networks together
What is Wireless Mesh
Network?
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A wireless mesh network is a
mesh network created through
the connection of wireless
access points installed at each
network user's locale.
Each network user is also a
provider, forwarding data to the
next node.
The networking infrastructure is
decentralized and simplified
because each node need only
transmit as far as the next node.
Wireless mesh networking could
allow people living in remote
areas and small businesses
operating in rural
neighborhoods to connect their
networks together for affordable
Internet connections.
Mesh topology definition
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A mesh network is a
network that employs one
of two connection
arrangements, full mesh
topology or partial mesh
topology.
In the full mesh topology,
each node is connected
directly to each of the
others.
In the partial mesh
topology, nodes are
connected to only some, not
all, of the other nodes."
Full and Partial Mesh Network
Functional components of
Mesh Networks
Access Point and Backhaul Router
of Mesh Network
Like any Wi-Fi access
point, the access point
in the mesh router
serves the mobile
users in the area.
The backhaul side of
the device wirelessly
relays the traffic from
router to router until it
reaches a gateway that
connects to the
Internet or other
private network via a
wired or other wireless
connection.
Network Architecture of
Wireless Mesh Network
• In the wireless mesh network, a
node can send and receive
messages, and it also functions
as a router and can relay
messages for its neighbors.
Multiple nodes cooperate to
relay a message to its
destination.
• Through the relaying process, a
packet of wireless data will find
its way to its destination,
passing through intermediate
nodes with reliable
communication links
• The mesh topology enhances
the overall reliability of the
network, which is particularly
important when operating in
harsh industrial environments.
Network Architecture of
Wireless Mesh Network
Network Architecture of
Wireless Mesh Network
Working of Mesh Networks
Interconnectivity between
Mesh and Other Networks
Configuration of Mesh Network
• Networks can be configured in one of several ways
such as:
(1) All the BSs, and only the BSs, are gateways to the
wireless network,
(2) none of the BSs are gateways
(3) the BSs are gateways (possibly with a limited
capacity)
along with other specific gateways,
(4) Every BSs and the MUs it serves are an IP-subnet
and all these subnets form a single IP-network.
Mesh networks –
motivations & expectations
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Until now, mesh
networks have
most often
proposed for
urban scenarios
and municipality
networks
But there is big
potential for
rural and remote
connectivity
scenarios
Suitability of Mesh Networks
in Industrial Applications
Topology
Reliability
Point-to-Point High
Point-toMultipoint
Mesh
Networks
Low
High
Adaptability
Scalability
Low
None
(2 end points)
Low
High
Moderate
(7-30 end
points)
Yes
(1000’s of end
points)
Advantages of Mesh Networks
Advantages of Mesh Networks
• Decreased need for Internet gateways
• Collaborative redundant backup technology, which insures
data security in the event of disk failure
• The ability to configure routes dynamically
• Lower power requirements, which could potentially be met
by low-cost or renewable energy sources
• Increased reliability: Each node is connected to several
other nodes and if one drops out of the network, its
neighbors simply find another route.
• Since mesh or multi-hop networks use low power
transmissions to reach only the nearby nodes there is less
interference with radio signals from other nodes.
Why Wireless Mesh Network?
Flexible coverage
Reliable routing
Mesh Hardware and
Software Examples
Hardware
Mesh AP
LinkSys WRT54G
Mesh node
4G Access cube
Software
MeshLinux
Zebra/Quagga
QuWin
OpenWRT
Pebble
Single, Dual, Triple Radio
Mesh Routers
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Mesh routers can employ one, two or three radios.
A single-radio router shares bandwidth between users and the backhaul.
If two radios are used, one is dedicated to the frontside clients and the other to the backhaul.
In three-radio routers, two radios are used for the backhaul and can transmit and receive
simultaneously over different Wi-Fi channels , such as the systems from BelAir Networks
(www.belairnetworks.com) and MeshDynamics (www.meshdynamics.com).
Infrastructure/Backbone
Wireless Mesh Network
Hybrid Wireless Mesh
Network
Mesh routing protocols:
Elements of mesh routing
A major benefit of wireless mesh
networks is path diversity, which
provides many routes to the
central network in case one of the
routers fails or its transmission
path is temporarily blocked.
The choice in routing algorithm is
critical, and numerous mesh
algorithms have been used over
the years.
• Node discovery
• Border discovery
• Link metrics
• Route calculation
• IP address management
• Uplink/backhaul
management
Mesh routing protocols: Types
• Proactive (Tabledriven)
Proactive checking of
Link state and updating of
routing tables – high
complexity and CPU load,
high performance
• Reactive (Ondemand)
Reacting on detection
problems (nonworking
routes) – less demanding
on CPU
• Lines between types are not
strict
• More and mixed types exist
Proactive(Tabledriven)
• OLSR (Optimized Link State Routing
protocol)OLSREXT,QOLSR
• TBRPF (Topology Broadcast based
on ReversePath Forwarding routing
protocol)
• HSLS (Hazy Sighted Link State
routing protocol)
• MMRP (Mobile Mesh Routing
Protocol), short: MobileMesh
• OSPF (Open Shortest Path First)
Reactive (Ondemand)
• AODV
Mesh routing protocols
MMRP(MobileMesh)
OLSR
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• OLSR is a routing protocol for mobile adhoc networks. The protocol is proactive, table
driven and utilizes a technique called
multipoint relaying (MPR) for message
flooding.
Mobile Mesh contains 3 separate protocols,
each addressing a specific function
Link Discovery – a Simple “Hello” Protocol
Routing Link - State Packet Protocol
Border Discovery Enables external tunnels
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Developed by Mitre (with military interest
involved)
• OLSRD is meant to be a well structured and
well coded implementation that should be
easy to maintain, expand and port to other
platforms. One of the most promising and
stable protocols
OSPF
• Calls for the sending of linkstate
advertisements (LSAs) to all other routers
within the same hierarchical area. Information
on attached interfaces, metrics used, and other
variables included in LSAs.
• OSPF routers accumulate linkstate
information, use the SPF algorithm to calculate
shortest paths
AODV
• The Ad hoc On Demand Distance
Vector (AODV) protocol is a routing
protocol designed for mobile ad hoc
networks. ...enables dynamic, self
starting, multihop routing between
computers.
Applications of Mesh Networks
Connected and Ad-hoc
Mesh Network
Security and Encryption in
Mesh Networks
Message Formats in Mesh
Network
State diagrams for message
passing in Mesh Network
Performance Issues
in Mesh Network
• Throughput
• Latency
• Scalability
• Security
• IP distribution
• Latency obviously has to
grow with number of hops
• Effects of latency
dependent on application
• Example VoIP: latency
can be felt from 170ms on,
but sometimes walkie talkie
with 5 s delay is better than
nothing
• Ad hoc networks per
definition need to talk to
clients before they know
them this imposes an
inherent security
challenge!
• IP distribution in mesh networks is
far from trivial
• Vulnerability to Denial of
Service attacks
• Ipv6 might solve many issues, but is
not
• DHCP in private IP ranges is
unproblematic, but what happens
when a mesh meets a neighbour mesh?
implemented widely yet
• Mesh has not been tested in real life with
more than a few dozen nodes
• Commercial implementations (200 nodes?
10,000 nodes?) often do not share (true)
experience – and are therefore hard to
evaluate
Issues in Mesh Networks
• Multihop performance degradation
– Exponential decay, linear decay, or k-asymptotic?
– Multiple Radios and preventing dynamic frequency
oscillations in a self aware network
• Scalability and bridging
– Most meshes are really small, and joined together
– IEEE 802 TGs is specifying 32 node maximums!
– How to manage disjoint but cooperating meshes
• Multiple loop-free Mesh portals (partially solved, but
not widely adopted)
• Mesh Security (solved)
• Compatibility (intra-mesh, and inter-mesh)
Privacy in Mesh Network
DEPLOYMENT ISSUES
• Practical deployment experience shows that
simple models, while useful, are largely
wrong.
• Metrics for routing need to take into
consideration expected throughput based on
network measurement.
• Self organization is critical, but currently
lacking.
Conclusion
• Mesh networks can handle many to many connections and
are capable of dynamically updating and optimizing these
connections
• WMN’s are a promising technology for next generation
wireless networking.
• Many application scenarios are stimulating its rapid
development.
• However, to strengthen the market penetration and
secure the success of WMN’s, more research is needed.
Questions
• What are functional components of Mesh Network?
Ans: Routing Functionality(L2 or L3), Access point,
Gateway Mesh point, Mesh Portal, Base station and
Mobile station.
• What are advantages of using Mesh Network?
Ans: Self forming, Self healing, Self balancing, Increased
Performance and coverage, Lower Infrastructure and Operational
costs, and Increased Reliability.
• What are the issues in Wireless Mesh Networks?
Ans: Throughput, Latency, Scalability, Security and IP distribution
References
• Kevin DeMartino, “An Architecture for a Seamless Mesh
Network”, IEEE Communications Magazine
• http://www.itrainonline.org/itrainonline/mmtk/wireless_en/17_Mes
h_Networking/17_en_mmtk_wireless_mesh-networking_slides.pdf
• http://www.oreillynet.com/pub/a/wireless/2004/01/22/wirelessmesh.
html
• http://en.wikipedia.org/wiki/Wireless_mesh_network
• http://en.wikipedia.org/wiki/Mesh_network
• http://en.wikipedia.org/wiki/Ad_hoc_routing_protocol_list
• http://wifinetnews.com/archives/003972.html
• http://www.sensorsmag.com/articles/0203/38/main.shtml
References
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IAN F. AKYILDIZ, GEORGIA INSTITUTE OF TECHNOLOGY,”A survey on
wireless mesh network”
Kamlesh Rath, Lalit Kotecha, Howard Persh, Deb Ranjan Das, Dat Ton, “Scalable
Connection Oriented Mesh Proposal ”
STEFANO M. FACCIN, MESH WLAN NETWORKS:CONCEPT AND SYSTEM
DESIGN
Rainer Baumann, Olga Bondareva, A Macro Mobility and Multihoming
Notification Protocol for Wireless Mesh Networks implementing Mobile IP and
SHIM6
http://www.intel.com/technology/comms/cn02032.htm
ieeexplore.ieee.org/iel5/35/32334/01509968.pdf
ieeexplore.ieee.org/iel5/2188/19625/00909581.pdf?arnumber=909581
www.answers.com/topic/wireless-mesh-network
www.eng.ucy.ac.cy/toumpis/courses/ECE453/papers/mesh2.pdf
www.apricot.net/.../1%20%20Danny%20Ng/Apricot%202004%20Wireless%20Mesh.pdf
Many IEEE papers on Mesh and Wireless Mesh Networks.
Many documents and links related to Mesh networks and Wireless Mesh Networks
in google.com and ask.com
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