Date of Award
Master of Science
Electrical and Computer Engineering
Computers and data networks have revolutionized communications today. The TCP/IP Protocol suite, specifically designed for wired networks, is the predominant protocol suite used in data networks. However, a large number of wireless devices are now part of data networks including the internet. A TCP flow on a wired network experiences data loss predominantly due to congestion on the network, while a TCP flow on a heterogeneous network, which is a combination of wired and wireless links, may experience data loss due to either congestion (along the wired links) or interference (on the wireless links). Whenever data loss occurs, TCP assumes the loss is due to congestion and reduces its transmission window size to relieve the congestion. This adversely affects the TCP throughput in a heterogeneous or wireless network, where most of the data loss is due to interference. In this research we propose ICEI TCP-a scheme for Implicit Congestion and Explicit Interference detection in TCP. ICEI TCP is designed based on the following assumptions: i). The heterogeneous network has a cellular wireless network architecture where all the links of the network are wired links while the last link alone is a wireless link ii). The wireless host simultaneously runs multiple distributed applications i.e. multiple TCP flows terminate on the same wireless host. In our scheme each TCP source within a sending host maintains its own Congestion History (CHISTORY), a fixed size queue, which contains the latest values of the Round Trip Time Ratio (RTTR). The RTTR is a ratio of the Round Trip Time (RTT) for each transmission of the TCP flow to the lowest such RTT value computed during the lifetime of that TCP flow. Rapid variations in the RTTR of successive transmissions, are treated as an indication that the TCP flow is heading towards congestion phase. Each wireless host on the network also maintains an Interference Profile (IPROFILE), a shared area in memory, which contains the latest details of the times at which packets loss is experienced by different TCP sinks on that wireless host. In case the IPROFILE has entries from different TCP sinks during a time interval i.e. if more than one TCP sink on the same wireless host experiences a packet loss within a time interval, the packet losses for all those TCP flows is interpreted to be due to the effect of interference on their shared wireless link. In the event of a packet loss, the TCP source in the ICEI TCP scheme now uses the information from the CHISTORY and IPROFILE to decide if congestion control algorithms need to be invoked. This ensures that congestion control algorithms are not invoked during a phase where interference is causing the data loss, thereby improving the throughput of the TCP flow.
Raghavan, Rakesh, "ICEI TCP: implicit congestion and explicit interference detection in TCP" (2003). Retrospective Theses and Dissertations. 20000.