In this dissertation we examine some of the challenges faced by the congestion
control algorithms of TCP in emerging networks. We focus on three main issues.
First, we propose TCP with delayed congestion response (TCP-DCR), for improving
performance in the presence of non-congestion events. TCP-DCR delays the conges-
tion response for a short interval of time, allowing local recovery mechanisms to
handle the event, if possible. If at the end of the delay, the event persists, it is treated
as congestion loss. We evaluate TCP-DCR through analysis and simulations. Results
show significant performance improvements in the presence of non-congestion events
with marginal impact in their absence. TCP-DCR maintains fairness with standard
TCP variants that respond immediately.
Second, we propose Layered TCP (LTCP), which modifies a TCP flow to behave
as a collection of virtual flows (or layers), to improve eficiency in high-speed networks.
The number of layers is determined by dynamic network conditions. Convergence
properties and RTT-unfairness are maintained similar to that of TCP. We provide the
intuition and the design for the LTCP protocol and evaluation results based on both
simulations and Linux implementation. Results show that LTCP is about an order
of magnitude faster than TCP in utilizing high bandwidth links while maintaining
promising convergence properties.
Third, we study the feasibility of employing congestion avoidance algorithms
in TCP. We show that end-host based congestion prediction is more accurate than previously characterized. However, uncertainties in congestion prediction may be un-
avoidable. To address these uncertainties, we propose an end-host based mechanism
called Probabilistic Early Response TCP (PERT). PERT emulates the probabilistic
response function of the router-based scheme RED/ECN in the congestion response
function of the end-host. We show through extensive simulations that, similar to
router-based RED/ECN, PERT provides fair bandwidth sharing with low queuing
delays and negligible packet losses, without requiring the router support. It exhibits
better characteristics than TCP-Vegas, the illustrative end-host scheme. PERT can
also be used for emulating other router schemes. We illustrate this through prelim-
inary results for emulating the router-based mechanism REM/ECN.
Finally, we show the interactions and benefits of combining the different proposed
mechanisms.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-1757 |
| Date | 02 June 2009 |
| Creators | Bhandarkar, Sumitha |
| Contributors | Reddy, A. L. Narasimha |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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