The%20Future%20of%20Broadband%20Wireless%20(and%20the%20role%20of%20

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The Future of Broadband Wireless(and the role
of awareness inwireless Internet performance)

• Carey Williamson
• iCORE Professor
• Department of Computer Science
• University of Calgary

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Introduction

• It is an exciting time to be an Internet
  researcher (or even a user!)
• The last 10 years of Internet development have
  brought many advances
• World Wide Web (WWW)
• Media streaming applications
• Wi-Fi wireless LANs
• Mobile computing
• E-Commerce, mobile commerce
• Pervasive/ubiquitous computing

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(No Transcript)
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The Wireless Web

• The emergence and convergence of these
  technologies enable the wireless Web
• the wireless classroom
• the wireless workplace
• the wireless home
• Holy grail anything, anytime, anywhere access
  to information (when
  we want it, of course!)
• My iCORE mandate design, build, test, and
  evaluate wireless Web infrastructures

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Clarification
Wireless Communications
(the enabler)

Wireless Internet
(the value-added service)
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Internet Protocol Stack

• Application supporting network applications and
  end-user services
• FTP, SMTP, HTTP, DNS, NTP
• Transport end to end data transfer
• TCP, UDP
• Network routing of datagrams from source to
  destination
• IPv4, IPv6, BGP, RIP, routing protocols
• Data Link hop by hop frames, channel access,
  flow/error control
• PPP, Ethernet, IEEE 802.11b
• Physical raw transmission of bits

001101011...
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Pieces of the Puzzle

• Portable computing devices no problem (cell
  phones, PDAs, notebooks, laptops)
• Wireless access not much of a problem
  (BlueTooth, IEEE 802.11, 802.11b, WiFi,
  802.11a, Pringles)
• Security still an issue, but being addressed
• Services the next big growth area???
• Performance transparency providing an end-user
  experience that is hopefully no worse than that
  in traditional wired Internet desktop
  environments (my focus)

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Research Theme

• Existing layered Internet protocol stack does not
  lend itself well to providing optimal performance
  for diversity of service demands and environments
• Who should bend users or protocols?
• Explore the role of awareness in Internet
  protocol performance
• Identify tradeoffs, evaluate performance

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Talk Overview

• Introduction
• Background
• Emerging Wireless Trends and Technologies
• The Future of Broadband Wireless
• The Role of Awareness
• TCP 101
• Motivating Examples
• Our Work on CATNIP
• Concluding Remarks

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Brief History Cellular/Wireless

• First Generation (1G) analog
  (cellular voice, AMPS, RTMS, TACS, 1980s)
• Second Generation (2G) digital
  (IS-64, GSM, ISM-95, 8-32 kbps, 1990s)
• Third Generation (3G) broadband multimedia
  (always on, UMTS, 334 kbps-2 Mbps, 2000s)

2.5G You are here
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Some Interesting Reading

• Brave New Unwired World (BNUW), by Alex
  Lightman and William Rojas
• In a nutshell, the authors argue that
• 2.5G is dead
• 3G is a waste of time (and money)
• 4G is EVERYTHING!!!

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Another Lightman Opinion

• the success of a technology in the marketplace
  is inversely proportional to the amount of hype
  associated with that technology prior to its
  release

Examples Internet, Web, napster, WiFi
Examples ISDN BlueTooth 3G
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What is 4G then?

• Culmination of wireless Internet revolution
• Convergence of key emerging technologies

Storage technology
Image Generation
802.11b
GPS
Semiconductors
Wearable Computers
New Interfaces
WIDs
Microprocessors
IP-based Networks
Antenna Arrays
Satellite
Backhaul NWs
RF elements
Molecular Engineering
NanoTech
Wireless Services
Quantum
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Some Challenges/Opportunities

• Ultra low-power processors
• pg 108 could change the entire industry
• Services
• pg 76 extension of the Internet to mobile
  deviceswhole new range of Internet
  servicespersonalized, location-sensitive
  contentpreviously impossible or impractical
• Awareness
• pg 221 Location/context-aware applications can
  determine and react to current physical computing
  context of mobile users altering information
  presented to users accordingly

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The Future?

• Service-centric economy
• Significant shifting of economic power
• The winner is likely to be either Japan (iMODE,
  DoCoMo) or China (Internet growth, wireless
  growth)
• Reasons
• cooperation, encouragement, support from
  government on a national scale
• strategic alliances within and across industries

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Talk Overview

• Introduction
• Background
• Emerging Wireless Trends and Technologies
• The Future of Broadband Wireless
• The Role of Awareness
• TCP 101
• Motivating Examples
• Our Work on CATNIP
• Concluding Remarks

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My iCORE Research Team

• Martin Arlitt Web performance, workload
  characterization
• Qian Wu TCP, ns-2 simulation
• Guangwei Bai network traffic measurement
  and modeling
• Tianbo Kuang wireless measurements, video
  compression, streaming media
• Nayden Markatchev technical support
• Grad Students Mingwei Gong, Yujian Li, Kehinde
  Oladosu, Fang Xiao, Andreas Hirt, Abhinav Gupta,
  Gwen Houtzager

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Internet Protocol Stack

• Application supporting network applications and
  end-user services
• FTP, SMTP, HTTP, DNS, NTP
• Transport end to end data transfer
• TCP, UDP
• Network routing of datagrams from source to
  destination
• IPv4, IPv6, BGP, RIP, routing protocols
• Data Link hop by hop frames, channel access,
  flow/error control
• PPP, Ethernet, IEEE 802.11b
• Physical raw transmission of bits

001101011...
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Viewpoint

• Layered design is good
  layered implementation is bad -Anon.
• Good
• unifying framework for describing protocols
• modularity, black-boxes, plug and play
  functionality, well-defined interfaces (good SE)
• Bad
• increases overhead (interface boundaries)
• compromises performance (ignorance)

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Research Theme

• Existing layered Internet protocol stack does not
  lend itself well to providing optimal performance
  for diversity of service demands and environments
• Who should bend users or protocols?
• Explore the role of awareness in Internet
  protocol performance
• Identify tradeoffs, evaluate performance

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Tutorial TCP 101

• The Transmission Control Protocol (TCP) is the
  protocol that sends your data reliably
• Used for email, Web, ftp, telnet,
• Makes sure that data is received correctly right
  data, right order, exactly once
• Detects and recovers from any problems that occur
  at the IP network layer
• Mechanisms for reliable data transfer sequence
  numbers, acknowledgements, timers,
  retransmissions, flow control...

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TCP 101 (Contd)

• TCP is a connection-oriented protocol

YOUR DATA HERE
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TCP 101 (Contd)

• TCP slow-start and congestion avoidance

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TCP 101 (Contd)

• TCP slow-start and congestion avoidance

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TCP 101 (Contd)

• TCP slow-start and congestion avoidance

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TCP 101 (Contd)

• This (exponential growth) slow start process
  continues until either of the following happens
• packet loss after a brief recovery phase, you
  enter a (linear growth) congestion avoidance
  phase based on slow-start threshold found
• all done terminate connection and go home

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Simple Observation

• Consider a big file transfer download
• brief startup period to estimate network
  bandwidth most time spent sending data at the
  right rate small added penalty for lost
  packet(s)
• Consider a typical Web document transfer
• median size about 6 KB, mean about 10 KB
• most time is spent in startup period as soon as
  you find out the network capacity, youre done!
• if you lose a packet or two, it hurts a lot!!!

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The Problem (Restated)

• TCP doesnt realize this dichotomy between
  optimizing throughput (the classic file transfer
  model) versus optimizing transfer time (the Web
  document download model)
• Wouldnt it be nice if it did?
  (i.e., how much data it was sending, and over
  what type of network)
• Some research starting to explore this...

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Motivating Example 1

• Wireless TCP Performance Problems

Low capacity, high error rate
Wired Internet
High capacity, low error rate
Wireless Access
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Motivating Example 1

• Solution wireless-aware TCP (I-TCP, ProxyTCP,
  Snoop-TCP, ...)

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Motivating Example 2

• Multi-hop ad hoc networking

Janelle
Carey
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Motivating Example 2

• Multi-hop ad hoc networking

Janelle
Yannis
Carey
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Motivating Example 2

• Multi-hop ad hoc networking

Janelle
Yannis
Carey
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Motivating Example 2

• Multi-hop ad hoc networking

Janelle
Yannis
Carey
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Motivating Example 2

• Two interesting subproblems
• Dynamic ad hoc routing node movement can disrupt
  the IP routing path at any time, disrupting TCP
  connection yet another way to lose packets!!!
  possible solution Explicit Loss Notification
  (ELN)
• TCP flow control the bursty nature of TCP packet
  transmissions can create contention for the
  shared wireless channel among forwarding nodes
  possible solution rate-based flow control

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Example of Our Work

• Context-Aware Transport/Network Internet
  Protocol (CATNIP)
• Motivation Like kittens, TCP connections are
  born with their eyes shut - CLW 2002
• Research Question How much better could TCP
  perform if it knew what it was trying to
  accomplish (e.g., Web document transfer)?

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Some Key Observations (I think)

• Not all packet losses are created equal
• TCP sources have relatively little control
• IP routers have all the power!!!

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Tutorial TCP 201

• There is a beautiful way to plot and visualize
  the dynamics of TCP behaviour
• Called a TCP Sequence Number Plot
• Plot packet events (data and acks) as points in
  2-D space, with time on the horizontal axis, and
  sequence number on the vertical axis

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Key X Data Packet Ack Packet
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SeqNum

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X

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Time
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TCP 201 (Contd)

• What happens when a packet loss occurs?
• Quiz Time...
• Consider a 14-packet Web document
• For simplicity, consider only a single packet
  loss

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?
Key X Data Packet Ack Packet

X

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SeqNum

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Time
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Key X Data Packet Ack Packet

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SeqNum

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Key X Data Packet Ack Packet
X
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?

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SeqNum

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Key X Data Packet Ack Packet
X
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X
SeqNum

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Key X Data Packet Ack Packet
SeqNum
?

X

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Key X Data Packet Ack Packet
SeqNum

X
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X



X

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Time
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TCP 201 (Contd)

• Main observation
• Not all packet losses are created equal
• Losses early in the transfer have a huge adverse
  impact on the transfer latency
• Losses near the end of the transfer always cost
  at least a retransmit timeout
• Losses in the middle may or may not hurt,
  depending on congestion window size at the time
  of the loss

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The TCP Transfer Pain Profile
Relative Transfer Time
1
N
SeqNum of the Single Lost Packet
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Design of CATNIP

• Can we make the TCP/IP protocols smarter about
  the specific job they are trying to do?
• Yes. Convey application-layer context information
  to the TCP and IP layers

Application
Transport
Network
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Design of CATNIP (Contd)

• Q What could a TCP source do differently?
• A If it knew how much data it had to send, and
  how far along it was already, then maybe
• Rate-Based Pacing of the Last Window (RBPLW)
• Early Congestion Avoidance (ECA)
• Selective Packet Marking (SPM)
• Use the reserved high-order bit in the TCP
  header to convey packet priority information
  (high priority for the really crucial packets)

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Design of CATNIP (Contd)

• Q What could an IP router do differently?
• A If it knew which packets were the painful
  ones to lose, then the router could
• CATNIP-Good give them preferential treatment,
  and avoid throwing them away (if possible)
  when congested
• CATNIP-Bad throw them away

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• Simulation Evaluation
• Network model

Client 1
Server 1
10 Mbps, 5 ms
10 Mbps, 5 ms
Client 2
1.5 Mbps, 5 ms
Server 2
RouterS
RouterC
Client 99
10 Mbps, 5 ms
10 Mbps, 5 ms
Client 100
Server 10
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• Simulation Evaluation (Contd)
• Web workload model
• 100 clients, 10 different Web pages
• Use empirically-observed distribution to
  determine the size, and the number of embedded
  images

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• Simulation Evaluation (Contd)
• Factors and Levels

• Performance metrics
• transfer time for each Web page
• packet loss ratio

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Simulation Results for DropTail Routers
Mean and Standard Deviation of Transfer Times
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Simulation Results for CATNIP-Good Routers Mean
and Standard Deviation of Transfer Times
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Observations

• Sources have relatively little control
• IP routers have all the power
• Adding context-awareness at the IP routers
  improves both mean and standard deviation of Web
  page transfer times
• SPM and CATNIP-Good provide most of the benefit
• Advantages of CATNIP are most prominent at low
  levels of IP packet loss (1-5)

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Summary

• There seem to be performance advantages to
  bending the rules regarding the Internet
  protocol stack layered model
• The general notion of awareness needs to
  explored in a variety of contexts
• wireless networks, ad hoc routing, TCP/IP, Web
  caching, mobile computing, adaptive
  applications,
• Many exciting issues to explore!!

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The Next Steps

• Putting it all together Web Wireless
• Wireless Internet Performance Lab (UofC)
• Experimental Laboratory for Internet Systems and
  Applications (UofS/UofC,CFI)
• Research Collaborations
• UofC, UofS, UofA, TRLabs, CS/ECE
• Nortel? HP? Cisco? Agilent? Telus Mobility?

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The End Question Time!

• For more information
• Email carey_at_cpsc.ucalgary.ca
• URL www.cpsc.ucalgary.ca/carey
• Many thanks to my research team and the TeleSim
  Research Group at the U of C
• Special thanks to iCORE, NSERC, CFI, andTelus
  Mobility