Multi-Layer Analysis of Web Browsing Performance for Wireless PDAs

1
Multi-Layer Analysis of Web Browsing Performance
for Wireless PDAs

• Adesola Omotayo Carey Williamson

November 1, 2014
2
Presentation Outline

• Introduction Motivation
• Related Work
• Data Gathering Validation
• HTTP-level Analysis
• TCP-level Analysis
• MAC-level Error Analysis
• Summary
• Future Work

3
Introduction Motivation

• Widespread availability of WiFi hot spots
• Limited understanding of multi-layer protocol
  interactions over IEEE 802.11b WLAN
• Crucial to understand the performance of the
  wireless Web

4
Related Work

• Workload of clients at wireline networks
• Client-based
• Changes in Web Client Access Patterns,P.
  Barford, A. Bestavros, A. Bradley, and M.
  Crovella, 1999
• Server-based
• Internet Web Servers Workload Characterization
  and Performance Implications,M. Arlitt and C.
  Williamson, October 1997
• Proxy-based
• On the Scale and Performance of Cooperative Web
  Proxy Caching,A. Wolman, G. Voelker, N. Sharma,
  N. Cardwell, A. Karlin, and H. Levy, December
  1999
• Workload of wireless clients
• Local-area
• Analysis of a Local-Area Wireless Network, D.
  Tang and M. Baker, August 2000
• Campus-area
• Analysis of a Campus-Wide Wireless Network, D.
  Kotz and K. Essien, September 2002
• Metropolitan-area
• Analysis of a Metropolitan-Area Wireless
  Network, D. Tang and M. Baker, August 1999

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Data Gathering Validation
A very simple workload

• Selected websites
• news, yellow pages, driving directions, stock
  quotes, educational resources, and downloadable
  PDA software
• Over a period of 35 minutes
• 398 TCP connections
• 1.8 with expected FIN handshake
• 96.5 used the RST packet
• 1.7 unsuccessful connections

AP Netgear WAB 102 PDA Compaq iPAQ 3600 Pocket
PC, Windows CE, IE, MTU size of 1500
bytes Wireless Sniffer Sniffer Pro 4.60.01,
microsecond resolution timestamps
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HTTP-level Analysis

• Server Response Time

• distinct plateaus
• consistent server response time
• response times lt 200 ms

Network RTT dominates the response latency Cache
per-destination state information
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HTTP-level Analysis

• Web Object Sizes

• object sizes
• 90 lt 10 KB
• 2.5 gt 40 KB
• file types
• most prevalent GIF, JPG HTML
• Least prevalent PNG
• largest objects transferred
• executables

Cache contents from wireless portals on Proxy
Servers Increase support for PNG file type
across browsers Compress executable files to be
more compact
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HTTP-level Analysis

• HTTP Transfer Time

• HTTP transfers
• 96 lt 1 second
• 2.5 gt 2 seconds
• larger objects take longer to download
• few small objects have excessively long transfer
  times

HTTP transfer times are generally low Most
responses fit in a single TCP packet
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TCP-level Analysis

• TCP Connection Type

• 13 were persistent
• 87 were non-persistent
• 4 of TCP connections sent gt 10 HTTP requests
• 65 of HTTP transfers occurred on persistent
  connections
• As much as 73 HTTP requests were seen per
  connection

Use persistent connections for all web sites
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TCP-level Analysis

• TCP Connection Duration

• 75 sent lt 20 packets
• 6 sent gt 100 packets
• 80 sent lt 10 KB
• 8 sent gt 50 KB
• 75 lasted lt 1 second
• 10 lasted gt 30 seconds
• 4 connections lasted gt 300 sec.

Most TCP connections are non-persistent Most web
object transfers are small Tightly set the
persistent connection timeout
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TCP-level Analysis

• TCP Connection Throughput

• 95 lt 400 Kbps

Non-persistent TCP connections Small HTTP
transfer size Non-negligible RTTs TCP slow
start effects
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MAC-level Error Analysis


MAC-level Retransmissions
CRC Errors

• 3 of the packets
• 40 of the connections
• most retry attempts for a packet 6

• 0.04 of the packets

TCP-level Retransmissions
HTTP-level Errors

• 0.2 of the packets
• 12 TCP connections
• 2 connection have gt 3 packet loss

• Unsuccessful 1
• Successful 96.74
• Aborted 2.26

Wireless channel quality does not have a major
impact on wireless Web browsing performance
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Summary (1 of 2)
Facts Implications
Network RTT dominates the response latency Caching per-destination state information (e.g., RTT, cwnd) might be effective
Web objects are typically small Web proxy caching of content from wireless portals could reduce network latency
Largest web objects transferred were executables Software providers should compress executable files into more compact file formats
Even though free, the least prevalent graphics file type on the web is PNG Increase support for PNG file type across web browsers
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Summary (2 of 2)
Facts Implications
87 were non-persistent and 65 of HTTP transfers occurred on persistent connections Wireless Web browsing would be faster if persistent connections were used for all Web sites
Some TCP connections lasted longer than 300 seconds Persistent connection timeout should be tightly set
52 of the TCP packets were transmitted by the client PDA Some form of ACK consolidation in Windows CE would economize on wireless network usage and battery power for wireless device
MAC 3 of the packets CRC 0.04 of the packets TCP 0.2 of the packets HTTP 1 of the connections Wireless channel quality does not have a major impact on wireless Web browsing performance
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Future Work

• Expand the work to a large scale traffic
  measurement
• Study the effect of interference and range
  overlapping among closely located APs

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References

• M. Arlitt and C. Williamson, Internet Web
  Servers Workload Characterization and
  Performance Implications, IEEE/ACM Transactions
  on Networking, Vol. 5, No. 5, pp. 631-645,
  October 1997.
• P. Barford, A. Bestavros, A. Bradley, and M.
  Crovella, Changes in Web Client Access
  Patterns, World Wide Web Journal, 1999.
• D. Kotz and K. Essien, Analysis of a Campus-Wide
  Wireless Network, Proceedings of ACM MOBICOM,
  Atlanta, GA, pp. 107-118, September 2002.
• D. Tang and M. Baker, Analysis of a
  Metropolitan-Area Wireless Network, Proceedings
  of ACM MOBICOM, Seattle, WA, pp. 13-23, August
  1999.
• D. Tang and M. Baker, Analysis of a Local-Area
  Wireless Network, Proceedings of ACM MOBICOM,
  Boston, MA, pp. 1-10, August 2000.
• A. Wolman, G. Voelker, N. Sharma, N. Cardwell, A.
  Karlin, and H. Levy, On the Scale and
  Performance of Cooperative Web Proxy Caching,
  Proceedings of ACM SOSP, December 1999.

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Thank You!

• ?