CS-435 Network Technology & Programming Laboratoryhy435/material/CS435-lecture15.pdf · Network Technology and Programming Laboratory CSD.UoC Stefanos Papadakis & Manolis

Network Technology & Programming LaboratoryCS-435spring semester 2014

Stefanos Papadakis & Manolis SpanakisUniversity of Crete

Computer Science Department

<CS-435> Network Technology and Programming Laboratory

CSD.UoC Stefanos Papadakis & Manolis Spanakis spring 2014

CS-435

• Lecture preview

• Ad-Hoc Networks

• Mesh Networking



Ad-Hoc? vs.

Mesh?

I can hear u, Lisa.

The Simpson's



Mobile Ad Hoc Networks

• May need to traverse multiple links to reach a

destination



Mobile Ad Hoc Networks (MANET)

• Mobility causes route changes



Why Ad Hoc Networks ?

• Ease and Speed in deployment

• Decreased dependence on infrastructure

• Only possible solution to interconnect a group of

nodes

• Many Commercial Products available today



Introduction• In the past the Ad hoc Networking paradigm absorbed a lot

of research effort.

• Most of the work is focused on isolated military or

specialized civilian application multi-hop ad hoc networks.

• Turning ad-hoc networks into a commodity takes a few

changes

• Make multi-hop flexible low cost last mile-extensions of

wired infrastructure:

Turn them into MESH NETWORKS!



MANET Applications

• Body Area Networking

• body sensors network,

• Personal area Networking

• cell phone, laptop, ear

phone, wrist watch

• Emergency operations

• search-and-rescue

(earthquakes, boats,

airplanes…)

• policing and fire fighting

Military environments

soldiers, tanks,

planes, battlefield

Civilian environments

taxi cab network

meeting rooms

sports stadiums

boats, small aircraft



Variations

• Traffic characteristics may differ in different ad hoc

networks

• bit rate, reliability requirements, unicast, multicast, host-based

addressing, content-based addressing, capability-based

addressing

• Adhoc networks may co-exist and co-operate with

infrastructure-based networks

• Mobility characteristics may be different

• speed, direction of movement, pattern of movement

• Symmetric vs. Asymmetric

• nodes’ capabilities and responsibilities



Issues in Mobile Ad-hoc

Networks• Limited wireless transmission range

• Broadcast nature of the wireless medium• Hidden terminal problem

• Packet losses due to transmission errors

• Mobility-induced route changes

• Mobility-induced packet losses

• Battery constraints

• Potentially frequent network partitions

• Ease of snooping on wireless transmissions (security hazard)



What’s unique about a

MANET ?• Moving nodes

ever changing topology

• Wireless links

various and volatile link quality

• Pervasive (cheap) devices

Power constraints

• Security

Confidentiality, other attacks



Ad-hoc & p2p a Comparison

• P2P is based on an IP network

• Ad-hoc is based on a mobile radio network

• Mobile Ad-hoc and Peer-to-Peer Networks

hold many similarities concerning their

• routing algorithms and

• network management principles

• Both have to provide networking functionalities

in a completely unmanaged and decentralized

environment

• ie. To determine how queries (packets) are guided

through the network



Ad-hoc & p2p a Comparison



Ad-hoc & p2p - Differences



Ad-hoc & p2p - Similarities



Is the ad-hoc paradigm failed?

• An ad-hoc network is a collection of mobile nodes that

connect over the wireless medium without the need of any

pre-deployed infrastructure.

• Nodes in a MANET can dynamically self-organize into

temporary and arbitrary and network topologies

✓ No pre-existing infrastructure required:

• Many supporting application scenarios:

• Disaster Recovery Areas

• Battlefields



Is the ad-hoc paradigm failed?

• Key Research drivers

• Bluetooth and WiFi

• mass market deployment

• ZigBee

• IETF “MANET” WG standardizations

Main problem:

• Users want:

• affordable devices

• Internet access

• Is high quality connectivity during mobility such an important issue?



Making ad-hoc networks a

commodity

• Pass down research from the MANET field to a more market-

viable networking paradigm.

• Relax the main constraint of MANETS:

• Accept the existence of wired infrastructure

• Wireless Mesh Networks (WMNs) are build by interconnecting

internet egress points with end-user devices can act as terminals

and as routers.

• Community Networks being the earliest form of Meshes, relaxed a

second MANET feature:

• Mesh nodes are practically stationary



Wireless Mesh Networks

• Wireless Mesh Networks (WMN) are the networks in which each node can communicate directly with one or more peer nodes.

• Different from traditional wireless networks (e.g. 802.11 WLANs) requiring centralized access points to mediate the wireless connection.

• Each node operates not only as a host but also as a router, forwarding packets on behalf of other nodes that may not be within direct wireless transmission range of their destinations.

• It is dynamically self-organized and self-configured, nodes can automatically establishing and maintaining mesh connectivity among nodes



Network ArchitectureWMNs consist of two types of nodes: Mesh Routers and Mesh

Clients

• Mesh router • Additional routing functions to support mesh networking.

• Multiple wireless interfaces with same or different wireless access technologies.

• The gateway/bridge functionalities enable the integration of WMNs with existing wireless networks(cellular, sensornet, Wi-Fi, WiMAX).

• Mesh Clients • Conventional nodes (e.g., desktops, laptops, PDAs, PocketPCs,

phones, etc.) equipped with wireless network interface cards (NICs), and can connect directly to wireless mesh routers.

• Customers without wireless NICs can access WMNs by connecting to wireless mesh routers through, e.g., Ethernet



WMN Architecture Classifications• Infrastructure Meshing

• Mesh routers form an mesh infrastructure among themselves.

• Provides backbone for clients and enables integration of WMNs with existing wireless networks

and Internet through gateway/bridge functionalities.

• Clients connect to mesh router with wireless link or Ethernet

• Client Mesh Networking• Client nodes constitute peer-to-peer network, and perform routing and configuration

functionalities as well as provide end-user applications to customers, mesh routers are not

required.

• Multi-hop routing.

• Client nodes have to perform additional functions such as routing and self-configuration.

• Hybrid Mesh Networking• A combination of infrastructure and client meshing.

• Infrastructure provides connectivity to other networks such as the Internet, Wi-Fi, WiMAX, cellular, and sensor networks;

• Mesh clients can access the network through mesh routers as well as directly meshing with other mesh clients.

• The routing capabilities of clients provide better connectivity and coverage



WMNs Characteristics

• Multi-hop wireless networks

• Support for Ad Hoc networking, and capability of self-forming, self-healing, and self-organization

• Mobility dependence on the type of mesh nodes

• Multiple types of network access

• Dependence of power-consumption constraints on the type of mesh nodes

• Compatibility and interoperability with existing wireless networks



Protocol Design

• Physical Layer

• Mac Layer

• Network Layer

• Transport Layer

• Application Layer

• Network Management

• Security



A Wireless Mobile Ad hoc

Network• A 10-node MANET at time t0



A Wireless Mobile Ad hoc

Network• A 10-node MANET at time t1



How does this change look like?

• A wireless mesh

network of 3 tiers



Ad-hoc – WMN, what is

different ?• The WMN concept is similar to ad-hoc networks concept

but has four important differences:

1. (practically) fixed nodes => Topology changes are infrequent

• Addition of nodes

• Node failure or maintenance

2. Traffic distribution is skewed (to/from the wired network)

3. Traffic characteristics aggregated from large numbers of flows

=> network optimization based on profiling

4. Reactive discovery of multi-hop paths is not efficient for an

effective backbone and not fit under (1).



Mesh Networking - Overview

Wireless routers

Gateways

Printers, servers

Mobile clients

Stationary clients

Intra-mesh wireless links

Stationary client access

Mobile client access

Internet access links

Node Types Link Types



How it Works

• User-Internet Data Flows

• In most applications the

main data flows

• User-User Data Flows

• In most applications a small

percentage of data flows



Taxonomy (example)Wireless

Networking

Multi-hop

Infrastructure-less

(ad-hoc)

Infrastructure-based

(Hybrid)Infrastructure-less

(MANET)

Single

Hop

Cellular

Networks Wireless Sensor

NetworksWireless Mesh

Networks

Car-to-car

Networks

(VANETs)

Infrastructure-based

(hub&spoke)

802.11 802.16 Bluetooth802.11



Mesh vs. Ad-Hoc Networks

Multi-hop

Nodes are wireless, possibly mobile

Do not rely on infrastructure

Most traffic is user-to-user

Ad-Hoc Networks Wireless Mesh Networks

Multi-hop

Nodes are wireless,

some mobile, some

fixed

It relies on

infrastructure

Most traffic is user-to-

gateway



Mesh vs. Sensor Networks

Bandwidth is limited

(tens of kbps)

In most applications, fixed

nodes

Energy efficiency is an

issue

Resource constrained


gateway

Wireless Sensor Networks Wireless Mesh Networks

Bandwidth is generous

(>1Mbps)

Some nodes mobile,

some fixed

Normally not energy

limited

Resources are not an

issue


gateway



Application domain• Broadband Internet Access

• Extend WLAN Coverage

• Mobile Internet Access• Direct competition

with cellular systems

• Emergency Response

• Layer 2 Connectivity• entire wireless mesh cloud becomes

one (giant) Ethernet switch

• Military Communications

• Community Networks

• Other: • Remote monitoring and control

• Public transportation Internet access

• Multimedia home networking

Internet

http://www.intel.com/update/contents/nc11032.htm

http://www.intel.com/update/contents/nc11032.htm



Research Topics

• Physical Layer

• Smart Antennas

• Transmission Power

Control

• MAC Layer

• Multiple Channels

• Network Layer

• Routing

• Fairness and QoS

• Transport Layer

• Provisioning

• Security

• Network Management

• Geo-location



QoS requirements• Physical Layer

• Robust modulation

• Link adaptation

• MAC Layer

• Offer priorities

• Offer guarantees

(bandwidth, delay)

• Network Layer

• Select “good” routes

• Offer priorities

• Reserve resources (for

guarantees)

• Transport

• Attempt end-to-end

recovery when

possible

• Application

• Negotiate end-to-end

and with lower layers

• Adapt to changes in

QoS



A key research decision that

made a big difference• Test-beds were used in WMN research from the start.

• MIT Roofnet (http://pdos.csail.mit.edu/roofnet/design/)

• Proof of existence of good enough solution for civilian

applications has stimulated the users’ interest to adopt this

technology.

• Two main solutions classes:

1. “off-the-shelf” => “community” networks

• Roofnet

• AWMN

• FORTH

• BAWUG

• Seattle Wireless

2. proprietary => MeshNetworks, Tropos Networks, Radiant…

http://pdos.csail.mit.edu/roofnet/design/



Companies

State of the art• Aerial Broadband

• BelAir Networks

• Firetide

• Intel

• Kiyon

• LamTech (ex.

Radiant)

• Locust World

• Mesh Dynamics

• Microsoft

• Motorola (ex. Mesh

Networks)

• Nokia Rooftop

• Nortel Networks

• Packet Hop

• Ricochet Networks

• SkyPilot Networks

• Strix Systems

• Telabria

• Tropos Networks



University Testbeds

• Georgia Tech - BWN-Mesh

• MIT - Roofnet

• Rutgers WinLab – Orbit

• SUNY Stonybrook – Hyacinth

• University of Utah – Emulab

• FORTH (eu - MESH)



Georgia Institute of Technology

BWN-Mesh

• 15 IEEE 802.11b/g

nodes

• Flexible configuration

and topology

• Can evaluate routing

and transport protocols

for WMNs.

• Integrated with the

existing wireless sensor

network testbed Source: http://users.ece.gatech.edu/~ismailhk/mesh/work.html

http://users.ece.gatech.edu/~ismailhk/mesh/work.html



MIT Roofnet• Experimental testbed

• More than 40 nodes at

the present

• Real users (volunteers)

• Focus on link layer

measurements and

routing protocols

• Open source software

runs on Intersil Prism

2.5 or Atheros AR521X

based hardware Source: http://pdos.csail.mit.edu/roofnet/doku.php

http://pdos.csail.mit.edu/roofnet/doku.php

http://pdos.lcs.mit.edu/roofnet/roofnet-weather.jpg

http://pdos.lcs.mit.edu/roofnet/roofnet-weather.jpg



Rutgers Winlab

ORBIT• Collaborative NSF project

(Rutgers, Columbia,

Princeton, Lucent Bell Labs,

Thomson and IBM Research)

• Start date: September 2003

• Emulator/field trial wireless

system

• 400 nodes radio grid

supporting 802.11x

• Software downloaded for

MAC, routing, etc.

• Outdoor field trialSource: www.winlab.rutgers.edu

http://www.winlab.rutgers.edu/



SUNY Stonybrook

Hyacinth

• Multichannel test-bed

based on stock PCs

with two 802.11a

NICs.

• Research focus on:

• interface channel

assignment

• routing protocol

Source: http://www.ecsl.cs.sunysb.edu/multichannel/

http://www.ecsl.cs.sunysb.edu/multichannel/



University of Utah

Emulab

• Three experimental environments

• Simulated and Emulated

• hundreds of PCs (168 PCs in racks)

• Several with wireless NICs (802.11

a/b/g)

• wide-area network

• 50-60 nodes geographically distributed

across approximately 30 sites

• Smaller brothers at

• U. of Kentucky

• Georgia Tech

Source: www.emulab.net

http://www.emulab.net/gallery/full/bigbundle.jpg

http://www.emulab.net/gallery/full/bigbundle.jpg

http://www.emulab.net/

http://www.emulab.net/gallery/full/side_shot.jpg

http://www.emulab.net/gallery/full/side_shot.jpg



FORTH’s metropolitan mesh

network testbedFORTH’s metropolitan

mesh network testbed

• 14 nodes: 6 multi-radio / PC-based

• independent management network

• 1.6 - 5.2km links

• 60sq.km. coverage



Extended testing

capabilities

• cross layer data acquisition

• parallel processing

• remote management

• remote & local storage

• high computing power

• 4+1 wireless interfaces per

node

• UPS & remote power

management

• Linux operating system



Features - Advantages -

Flexibility - Adaptability• real life environment

• city wide deployment

• high density population

coverage

• over 9 years of

experience

• off-the-self hardware

• highly customizable &

expandable

• multiple Internet

gateways

• service-driven network

virtualization

• mobile social networking

• location based services

• emergency services

• rapid deployment

scenarios

• ubiquitous wireless

access

• future technologies proof



Standards & Committees

• IEEE standards groups actively working to define specifications for

wireless mesh networking techniques

• Special groups established to define the requirements for mesh networking

in WPANs, WLANs, and WMANs.

• The following standards amendments are considering WMNs:

• 802.15.5 (bluetooth - WPAN)

• 802.11s (wi-fi - WLAN)

• 802.16a (wi-max - WMAN)

• Also 802.20 (wireless mobile broadband access -WMBA) is to support the

Mesh Networking paradigm from the first spec.

• On 12 June 2008, the IEEE approved the new standard



The 802.11s ideas• The 802.11 group had set up the “TG s” to discuss proposals for a specs

amendment in the 2nd quarter of ’05 and reach a final document no sooner than

2007.

…And still is at the drafting stage

• Scope of the Project: An IEEE 802.11 Extended Service Set (ESS) Mesh is a collection of APs

interconnected with wireless links that enable automatic topology learning and dynamic path

configuration.

• The proposed amendment shall be an extension to the IEEE 802.11 MAC.

• The amendment will define an architecture and protocol for providing an IEEE 802.11 ESS Mesh

using the IEEE 802.11 MAC to create an IEEE 802.11 Wireless Distribution System that supports

both broadcast/multicast and unicast delivery at the MAC layer using radio-aware metrics over self-

configuring multi-hop topologies.

• An ESS Mesh is functionally equivalent to a wired ESS, with respect to the STAs relationship with

the BSS and ESS.



The 802.11s ideas

The amendment shall:

• Enable interoperable formation and operation of an ESS Mesh

• extensible to allow for alternative path selection metrics and/or

protocols based on application requirements.

• target configuration of up to 32 devices participating as AP

forwarders in the ESS Mesh. Larger configurations may also be

contemplated by the standard.

• The architecture defined by the amendment shall allow an ESS Mesh

to interface with higher layers and to connect with other networks using

higher layer protocols.

• Utilize IEEE 802.11i security mechanisms, or an extension thereof, for the

purpose of securing an ESS Mesh in which all of the APs are controlled by

a single logical administrative entity for security.

• Allow the use of one or more IEEE 802.11 radios on each AP in the ESS

Mesh.”



802.11s timeline

802.11s started as a Study Group of IEEE 802.11 in September 2003.

Became a Task Group in July 2004.

A call for proposals was issued in May 2005, which resulted in the submission of 15

proposals submitted to a vote in July 2005.

After a series of eliminations and mergers, the proposals dwindled to two (the "SEE-

Mesh" and "Wi-Mesh" proposals), which became a joint proposal in January 2006.

This merged proposal was accepted as draft D0.01 after a unanimous confirmation

vote in March 2006.

The draft evolved through informal comment resolution until it was submitted for a

Letter Ballot in November 2006 as Draft D1.00.

Draft D2.00 was submitted in March 2008 which failed with only 61% approval.

A year was spent clarifying and pruning until Draft D3.00 was created which reached

WG approval with 79% in March 2009.

The Task Groups stated goal for the May 2009 802.11 meeting is to start resolving

comments from its new Letter Ballot



IEEE 802.15.1- Bluetooth

• Low data rate (1Mbps bit-

rate) BAN/PAN technology

• Targets wire replacement

• Has provisions for multi-hop

scatter-nets

• Not a popular wireless mesh

network platform due to:

• the low bandwidth and

• limited hardware support for

scatter-nets.



IEEE 802.15.4 - Zigbee

• Lower data rate BAN/PAN (250,40,20kbps)

• Multi-months – years lifetime on small batteries

• Supports mesh topology – one coordinator is responsible for setting up the network

• Characteristics suitable for wireless sensor networks rather than wireless mesh networks



IEEE 802.15.5

Mesh Topology Capability in (WPANs).

• Standard applicable to all other WPANs

• Mesh networks have the capability to provide:

• Extension of network coverage without

increasing transmit power or receive sensitivity

• Enhanced reliability via route redundancy

• Easier network configuration

• Better device battery life due to fewer

retransmissions



The 802.16a• 802.16 is a point to multipoint first-mile/last-mile WMAN connection

standard

• data rate up to 120Mbps @ 30miles

• great for gateway to internet links

• A base station serves a number of subscriber stations

• BS uses a broadcast channel to transmit to all SSs.

• 802.16 approved in 2001

(10-66GHz operation – TDMA, TDD&FDD)

• 802.16a approved in Jan. 2003

(2-11 GHz operation added -ODFM)

• The extensions specifies user-user links using:

• either centralized schedules,

• or distributed schedules.

• Already obsolete and part of the 802.16-2004 doc

• Stations may have direct links to each other - control can be

distributed.

• WiMax forum formed later in 2003 (just like the 802.11 Wi-Fi forum) to

promote IEEE standards for interoperability)

• Certifications began as late as 2006



More references….

• http://research.microsoft.com/mesh

• Roofnet

• Seattle Wireless

• Locust World

• Kingsbride Link

• Mesh Networks Inc

• FireTide Inc.

• Strix Networks Inc

• Telabria Inc

• Tropos Inc

• Cowave Inc

http://research.microsoft.com/mesh

http://www.pdos.lcs.mit.edu/roofnet/

http://www.seattlewireless.net/

http://meshbook.locustworld.com/

http://www.kingsbridgelink.co.uk/

http://www.meshnetworks.com/

http://www.firetide.com/

http://www.strixsystems.com/

http://www.telabria.com/

http://www.tropos.com/

http://www.cowave.com/

Documents

CS-435 Network Technology & Programming Laboratoryhy435/material/CS435-lecture15.pdf · Network Technology and Programming Laboratory CSD.UoC Stefanos Papadakis & Manolis