Lecture 1: Introduction
University of Tehran
Dept. of EE and Computer Engineering
By:
Dr. Nasser Yazdani & Farshad Lahouti
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Learn challenges in wireless networking
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What forces us to reconsider many traditional designs?
Understand state-of-the-art in wireless/ubiquitous systems
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Get a broad view of the ongoing research in the wireless domain.
Have a good understanding of the capabilities and limitations of them
Above all enjoy learning something new
Univ. of Tehran Wireless Ad hoc/Sensor Networks 2

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Course Web page
 http://ece.ut.ac.ir/classpages/F85/Wireless/
 visit regularly
Research papers
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Pdf/ps version of the papers on the Web page
~30 papers, Combination of classic and recent work. Some Optional reading!
Recommended textbook
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“Ad Hoc Wireless Networks: Architectures and
Protocols”, Ram Murthy & Manoj.
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Homework assignments, around %20
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Paper review
Problems and hands-on assignments
Severe late penalties!
Project, ~ %30
Exam(s) ~%50
No Presentation : Except for PhD students
Univ. of Tehran Wireless Ad hoc/Sensor Networks 4

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Some Networking concepts are behavioral, then, do not expect everything is as exact as mathematics.
Networking in general and wireless in particular is a complicated field even though it sounds easy and straightforward,
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Concentrates on concepts instead of a special technique or technology.
The course is not a classic course like math 2, be prepared for a lot of ideas.
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Then, class participation is extremely important.
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Do not leave everything to the last minute.
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We will try to understand the wireless networking as a whole. Believe or not Networking is fun and applicable in many places.
You are supposed to be trained as researcher, then,
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Be open minded, nothing is final.
Try to understand the history and idea. It is important to not repeat the same thing people have done previously
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Capture concepts, then, you can easily say what is possible or not possible.
Will try to follow layering perspective . Different from the book
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People from different background and different interests. Makes course customization difficult
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Try to give input
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Be patient!
Wireless realm is very vast, from communication to computer.
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It is not possible to cover everything in one semester
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We try to expose you to the whole realm without going necessarily in all detail.
Notice: This course is the beginning not the end.
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Is this a vision/position/direction paper, or just a measurement/implementation?
How the paper is compared to others? Can I mentally slot this paper somewhere in the taxonomy? “Differs from X as follows; has the following in common with Y”
What is the most important contribution?
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Does this advance the state of the art?
Did you learn anything new?
Does it provide evidence which supports/contradicts hypotheses?
Is there experimental validation?
Any technical flaws?
Will the paper generate discussion in the class?
How readable is the paper?
Is the paper relevant to a broader community?
Univ. of Tehran Wireless Ad hoc/Sensor Networks 9

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Goal: new research results
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Several publications from last years
Instructive projects okay too
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Ex: protocol visualization tool
System building, simulation-based
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Theoretical analysis
Must have strong networking concept
Try to work with 1–2 partners
Project proposal with presentation around 5-10 mins
Final report + presentation session
Univ. of Tehran Wireless Ad hoc/Sensor Networks 10

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Overview
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The challenges, technologies, and trends
Wireless Fundamentals
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Source and channel coding
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Frequency spectrums
Wireless LAN
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MAC protocols
Wireless Internet – Mobile IP
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Routing for Wireless
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Ad Hoc Routing
TCP in wireless enviroment
Power Management wireless Sensor Networks
Quality of Services (QoS)
Hybrid Wireless Networks – Architectures– Pricing,
Power Control, Load Balancing
Special Topics
Univ. of Tehran Wireless Ad hoc/Sensor Networks 12

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Mobility: to support mobile applications
Costs: reductions in infrastructure and operating costs: no cabling or cable replacement
Special situations: No cabling is possible or it is very expensive.
Reduce downtime: Moisture or hazards may cut connections.
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Rapidly growing market attests to public need for mobility and uninterrupted access
Consumers are used to the flexibility and will demand instantaneous, uninterrupted, fast access regardless of the application.
Consumers and businesses are willing to pay for it
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700
600
500
400
300
200
Millions
Mobile Telephone
Users
Internet Users
100
0
1993 1994 1995 1996 1997 1998 1999 2000 2001
Year

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Historic shift from PC’s to mobile computing and embedded devices…
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>2B cell phones vs. 500M Internet-connected PC’s in 2005
>400M cell phones with Internet capability, rising rapidly
Sensor deployment just starting, but some estimates ~5-10B units by 2015
~750M servers/PC ’s, >1B laptops, PDA’s, cell phones, sensors
~500M server/PC
’s, ~100M laptops/PDA’s
Wireless
Edge
Network
INTERNET
INTERNET
Wireless
Edge
Network
Univ. of Tehran
2005
Wireless Ad hoc/Sensor Networks 2010 18

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Wireless as the common case vs. the exception
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Laptop (54%) vs. desktop sales
(46%)
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>2B cell phones vs. 500M
Internet-connected PCs
Estimates of ~5-10B wireless sensors by 2015
Staggering Market Statistics
• 9 million hotspot users in 2003
( 30 million in 2004 )
• Approx 4.5 million WiFi access points sold in 3Q04
• Sales will triple by 2009
• Many more non-802.11 devices
Total 667
Rapid deployment of new technology
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Highly dynamic environment
Must accommodate new/unexpected technologies
Univ. of Tehran
Classified
802.11b
802.11g
472
379
93
7/2004 wardrive (802.11g standardized in 6/2003)
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Flexible
Low cost
Easy to deploy
Support mobility
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Ubiquitous, Pervasive computing or nomadic access.
Ad hoc networking: Where it is difficult or impossible to set infrastructure.
LAN extensions: Robots or industrial equipment communicate each others. Sensor network where elements are two many and they can not be wired!.
Sensor Networks: for monitoring, controlling, e
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Mobile hosts traveling through fixed network
Good for periodic download or upload of bulky data
Wireless islands (interconnected by wired network)
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Gas stations
Here and there on the freeway
Possibly an invisible infrastructure with mobile-aware applications
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In reality, you may need to know to go to it
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Original paper assumes this: information kiosks
Coverage is spotty
Cost is lower than complete coverage
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Collection of wireless mobile nodes dynamically forming a temporary network without the use of any existing network infrastructure or centralized administration.
Hop-by-hop routing due to limited range of each node
Nodes may enter and leave the network
Usage scenarios:
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Military
Disaster relief
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Temporary groups of participants (conferences)
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Deployment of small, usually wireless sensor nodes.
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Collect data, stream to central site
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Maybe have actuators
Hugely resource constrained
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Internet protocols have implicit assumptions about node capabilities
Power cost to transmit each bit is very high relative to node battery lifetime
Loss / etc., like other wireless
Ad-hoc: Deployment is often somewhat random
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Very mobile – whole network may travel
Applications vary according to purpose of network
No pre-existing infrastructure. Do-ityourself infrastructure
Coverage may be very uneven
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Connected to network
 send and/or receive
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May be embedded only for network access
Network
 networked appliances
 sensors
 historical sites & other locations
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Composite devices
 security system
Network
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Distributed composites vs. hardwired devices
 client-defined composites
 reuse of constituents
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 ease of change extendibility & scalability
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Network
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Issues
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Late binding
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Naming
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Discovery
IPC
User-interface deployment
Multi-appliance control
Univ. of Tehran
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Access control
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Existing social protocols not supported by existing mechanisms
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All co-located users can use appliance
Wireless Ad hoc/Sensor Networks
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Children can see certain channels

Univ. of Tehran
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Motivation
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 location-based action
 nearby local printer, doctor
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 nearby remote phone directions/maps location-based information
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 real
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 person’s location history/sales/events virtual
 walkthrough story of city augmented
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Operations based on locations and orientations of users and devices
Motivation
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Augmented reality
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Magic Lens
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Computers on body
 track body relative movements
 monitor person
 train person
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Embedded
Location
Interactive
Sensor
Flight
Simulator
Wearable
Mobile
Active badge
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Need to be connected from everywhere and anytime.
Need to be connected on movement
Need to good quality service on those situation.
Interworking with the existing networks
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Mobility: fixed wireless or mobile
Analog or digital
Ad hoc (decentralized) or centralized
(fixed base stations)
Services: voice (isochronous) or data
(asynchronous)
Ownership: public or private
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Area: wide (WAN), metropolitan (MAN), local (LAN), or personal (PAN) area networks
Switched (circuit- or packet-switched) or broadcast
Low bit-rate (voice grade) or high bit-rate
(video, multimedia)
Terrestrial or satellite
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Channel characteristics
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Half-Duplex
Location dependency
Very noisy channel, fading effects, etc.,
Resource limitation
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Bandwidth
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Frequency
Battery, power.
Wireless problems are usually optimization problems.
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Mobility in the network elements
Very diverse applications/devices.
Connectivity and coverage (internetworking) is a problem.
Maintaining quality of service over very unreliable links
Security (privacy, authentication,...) is very serious here. Broadcast media.
Cost efficiency
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Integration with existing data networks sounds very difficult.
It is not always possible to apply wired networks design methods/principles here.
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initially ARPANET and ARPA packet radio network
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Survivability ensure communication service even in the presence of network and router failures
Support multiple types of services
Must accommodate a variety of networks
Allow distributed management
Allow host attachment with a low level of effort
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Host mobility is not considered in the design.
There is a hierarchal design. How Ad hoc wireless networks can be handled
A layered design. Layer should be independent of each other. It is not work at all in wireless
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TCP
Battery shortages;
Etc,.
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Many Internet protocols assume frequent connectivity
What if your node is only on the Internet for 5 minutes every 6 hours?
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How do you browse the web?
Receive SMTP-based email?
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No QoS assumed from below
Reasonable but non-zero loss rates
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What’s minimum recovery time?
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1rtt
But conservative assumptions end-to-end
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TCP RTO - min(1s)!
Interconnect independent networks
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Federation makes things hard:
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My network is good. Is yours? Is the one in the middle?
Scale
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Routing convergence times, etc.
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Multimedia over IP networks
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Next Generation Internet with features for “soft”
QoS
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RSVP, Class-based Queuing, Link Scheduling
Voice over IP networks
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Packet Voice and Video
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RTP and ALF
Intelligence shifts to the network edges
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Better, more agile software-based voice and video codecs
Univ. of Tehran Wireless Ad hoc/Sensor Networks Programmable intelligence
44 the network

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Scalability
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Must scale to support hundreds of thousands of simultaneous users in a region.
Functionality
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Computer-phone integration
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Real-time, multipoint/multicast, locationaware services, security
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Home networking, “active” spaces, sensors/actuators
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First Principles-based Design
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Leverage evolving IP traffic models
Provisioning the network for the extrapolated traffic and services
ProActive Infrastructure
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Computing resources spread among switching infrastructure
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Computationally intensive services: e.g., voice-totext
Service and server discovery
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Physical layer: signals travel in open space
Subject to interference
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From other sources and self (multipath)
Creates interference for other wireless devices
Noisy  lots of losses
Channel conditions can be very dynamic
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Need to share airwaves rather than wire
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Don’t know what hosts are involved
Hosts may not be using same link technology
Interaction of multiple transmitters at receiver
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Collisions, capture, interference
Use of spectrum: limited resource.
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Cannot “create” more capacity very easily
More pressure to use spectrum efficiently
Univ. of Tehran Wireless Ad hoc/Sensor Networks 48

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Mobility
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Must update routing protocols to handle frequent changes
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Requires hand off as mobile host moves in/out range
Changes in the channel conditions.
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Coarse time scale: distance/interference/obstacles change
Fine time scale: Doppler effect
Other characteristics of wireless
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Slow
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Collision Avoidance:
Car Networks
Mesh Networks
Wired Internet
Access
Point
Sensor
Relay Node
Ad-Hoc/Sensor Wireless Home
Wireless Ad hoc/Sensor Networks
Multimedia
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INTERNET
Wireless
Edge
Network
INTERNET
Wireless
Edge
Network
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2005
2010
New architectures must accommodate rapidly evolving technology
Must accommodate different optimization goals
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Power, coverage, capacity, price
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Interference and unpredictable behavior
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Need better management/diagnosis tools
Lack of isolation between deployments
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Cross-domain and cross-technology
Why is my
802.11 not working?
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Performance: Nothing is really work well
Security: It is a broadcast media
Cross layer interception
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TCP performance
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