Improving TCP Performance over Wireless Networks

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Improving TCP Performance over Wireless Networks

• Project Proposal

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Outline

• Wireless Network
• TCP
• Challenges
• Design Issues
• Existing Research Work
• Research Focus and Directions
• References

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Wireless Network

• Architecture
• Mobile Hosts are connected to Base stations
  through Wireless and Base Stations are connected
  with Wireline Internet

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Wireless Network

• Issues
• High rate of Packet Loses
• Handoff
• Large RTT and RTT Variation

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Next one is

• Wireless Network
• TCP
• Challenges
• Design Issues
• Existing Research Work
• Research Focus and Directions
• References

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TCP

• Today, Majority of Application Protocols use
  Internets reliable Transmission Control Protocol
  (TCP).
• TCP aims at providing a reliable service with
  aiming to provide following features
• Fairness to other flows that potentially share a
  channels bandwidth
• Dynamic Discovery of current availability of
  bandwidth
• Congestion Avoidance and Control
• Optimization of Error Recovery Process

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TCP

• Issues in Wireless
• TCP only assume that Packet loss is due to
  Congestion
• But in wireless environment Packet loss can be
  due to following reasons
• High bit Error Rates
• Handoffs
• Disconnections
• TCP Only resolve the packet Loss issue by
  decreasing the sending rate
• TCP resolution strategy degrades TCP Performance
  and throughput

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TCP

• In short
• Not Capable of detecting the nature of Error but
  only the result of the error
• Error recovery mechanism is not efficient
  specially in Wireless environment
• Very important need of TCP features for wireless
  devices similar to TCP features for wireline
  devices

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Next one is

• Wireless Network
• TCP
• Challenges
• Design Issues
• Existing Research Work
• Research Focus and Directions
• References

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Challenges

• Propose TCP must be able perform in wireless
  environment similar to as current TCP in Wireline
  network.
• Also able to deal with following characteristics
  of Wireless environment
• High bit Error Rate
• Handoff
• Disconnections
• Large RTT and RTT Variation
• It should be simple to implement and easy to
  deploy

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Next one is

• Wireless Network
• TCP
• Challenges
• Design Issues
• Existing Research Work
• Research Focus and Directions
• References

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Design Issues

• Which part of network to implement the solution?
  It can be following
• Sender
• Receiver
• Wired part of the Network
• Wireless part of the Network
• Hybrid Approach

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Design Issues

• Which layer to implement the solution? It can be
  following
• Transport Layer
• Network Layer
• MAC Layer

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Next one is

• Wireless Network
• TCP
• Challenges
• Design Issues
• Existing Research Work
• Research Focus and Directions
• References

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Existing Research Work

• TCP-Probing
• Indirect TCP (I-TCP)
• MTCP
• Explicit Bad State Notification (EBSN)
• WTCP
• Snoop

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Existing Research Work

• TCP-Probing
• Monitor the Network status on time out event or
  due to three Duplicate Acknowledgements
• A structured probe segment, is initiated by
  sender and sender also suspends all data
  transmission until probe acknowledgement

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Existing Research Work

• Indirect TCP (I-TCP)
• Splits the transport link at the
  wireline-wireless boundary
• Attempt to hide the effect of wireless losses
  from TCP.
• Loses the TCPs end-to-end semantics
• Also causes the high overhead of two connections
  at boundary of wireline-wireless.

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Existing Research Work

• MTCP
• Similar to I-TCP except that the last byte of
  data is to acknowledged to the source only it is
  received by the mobile host.

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Existing Research Work

• Explicit Bad State Notification (EBSN)
• If the wireless link is in erroneous state then
  the base station sends EBSN message to source for
  every retransmission of a segment to mobile host.
  It will require changes at source to incorporate
  EBSN messages.

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Existing Research Work

• WTCP
• Congestion is detected by inter-packet separation
  at the receiver side.
• Receiver does most of the computations for
  congestion control.
• It requires modifications in both Mobile host and
  as well as Fixed host.

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Existing Research Work

• Snoop
• Implemented at Data Link Layer
• Base station, boundary of wireline-wireless
  network, monitor packets in both directions.
• Base Station cache the packets and if detect the
  duplicate acknowledgements then it retransmit the
  packet from cache to mobile host.
• Sack is used when traffic is send from mobile
  host to fixed server.
• No change required in fixed host.
• End-to-End mechanisms will also be preserved.
• But the Link layer needs to aware that that the
  segment is of TCP packet.
• It can also not be implemented for encrypted
  headers.

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Next one is

• Wireless Network
• TCP
• Challenges
• Design Issues
• Existing Research Work
• Research Focus and Directions
• References

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Research Focus and Directions

• As transport layer seems to be most appropriate
  place for Error Control so my research will focus
  for the implementation at transport layer.
• There may also include lower layers for
  optimization based on more precise information
  that could be gathered from lower layers.
• My design goals will focus to cover above
  mentioned challenges maximally.

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Research Focus and Directions

• My intention will be to design the mechanisms
  which will able to identify the nature of the
  error due to which packet is dropped. And design
  of error recovery techniques based on different
  nature of error.
• My initial focus of implementation will be
  wireless part of the network.

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Research Focus and Directions

• My initial though is that the Wieleline network
  will provide an interface to wireless network at
  connection management time to communicate its
  network characteristics so that during further
  communication my mechanism will consider these
  characteristics to detect the nature of the
  error.
• To analyze the performance of identified
  techniques I will work on Network Simulator named
  as REAL.

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Next one is

• Wireless Network
• TCP
• Challenges
• Design Issues
• Existing Research Work
• Research Focus and Directions
• References

27
References

• Open Issues on TCP for Mobile Computing by
  Vassilis Tsaoussidis and Ibrahim Matta
• Improving Reliable Transport and Handoff
  Performance in Cellular Wireless Networks by
  Hari Balakrishnan, Srinivasan Seshan and Randy H.
  Katz
• Congestion Control for High Bandwidth-Delay
  Product Networks by Dina Katabi, Mark Handley,
  Charlie Rohrs
• Comparative Study of Various TCP Versions Over a
  Wireless Link with Correlated Losses
• Presentation on Introduction to TCP in Wireless
  Networks by Wan Gang Zeng at Simon Fraser
  University on July 2003
• 15th lecture of Topics in Internet Research on
  Wireless TCP by Satyam Sharma on February 2003