Robust Dynamic Congestion Control Protocol for Mobile Networks (TCP DCM+)
Date
2019-12-21
Authors
Derar Sameeh Abdel-Aziz Khader
ضرار سميح عبد العزيز خضر
Journal Title
Journal ISSN
Volume Title
Publisher
Al-Quds University
Abstract
Data networks are considered as a critical corner of data transmission
between the different hosts wherever they exist. In the last few years, the wireless
and mobile networks become more important for daily use and are their spread is
increasing for personal and commercial use. The main difference between wired
and wireless networks is the large number of lost packets during the data
transmission. The packet losses are a result of errors on the data transmission
channel. These errors are due to external noise, interference and mobility of the
wireless devices that results in deep fading. The mentioned problems earlier are the
reasons that the throughput of wireless, mobile and mobile adhoc networks is less
than wired networks, which does not suffer such problems.
Old traditional transmission control protocols like (Standard TCP) behave
extremely hard when they detect any data packet losses. They drop the congestion
window to the half though the transmission channel capacity is not exhausted. This
high drop results in low throughput, hence longer time to finish the transmission.
Most traditional TCP protocols lack the use of appropriate techniques to
estimate the available channel capacity, which are known as bandwidth estimation
(BWE) techniques. In 2004, TCP Westwood+ protocol proposed a technique for
estimating the available channel capacity. It uses a first-order low-pass filter to find
the available bandwidth. TCP Westwood+ has largely improved the throughput of
TCP connections, however, the problem of window drops is still existing, which
makes it less appropriate for use in networks, that include mobility, i.e. MANETs.
Hence, it is desired to modify the TCP protocol behavior to eliminate these drops,
which are the results of congestion events or channel problems. If the congestion
events are eliminated, then we can detect the times at which the transmission
channel problems occur.
The proposed approach in this thesis is called TCP DCM+. It is the
abbreviation for “Dynamic Congestion Control for Wireless and Mobile
Networks”. The transfer of data with different sizes has been simulated with
different packet error rates, which should simulate the existence of wireless
channel for large packet error rates (1e-3 to 5e-2).
We executed hundreds of simulations for cases with different parameters
like error rates, MTU sizes, bandwidth of both bottleneck (link) and destination
(access), protocol type and the size of sent data. We found that DCM+ performs
better than the other approaches, especially if the error rates are large. We used the
usual performance metrics like throughput, average delay and packet losses to
measure how well our approach performs. Additionally, we introduced two new
metrics to measure the total time needed to finish the transmission, and also to
measure the robustness and stability of the transmission. Our conclusion is, that
DCM+ is minimizing congestion events, hence, transmits data much faster, shows
stable behavior and is highly robust compared with other approaches.