ON IMPROVING THE PERFORMANCE OF TCP APPLICATIONS IN PUBLIC CLOUD NETWORKS

The Hong Kong University of Science and Technology
Department of Computer Science and Engineering


PhD Thesis Defence


Title: "ON IMPROVING THE PERFORMANCE OF TCP APPLICATIONS IN PUBLIC CLOUD
NETWORKS"

By

Mr. Ahmed MOHAMED ABDELMONIEM SAYED


Abstract

By making computing available to the users in the same manner as utilities, 
such as water, electricity, and gas are, Cloud computing has defined a new 
computational approach that is revolutionizing the IT industry. As a natural 
consequence, and under the impetus of competition between cloud service 
providers (CSPs), data center deployments have seen a dramatic increase. Today, 
it is believed that most data or information circulating on the Internet, 
originates from some data center somewhere in the world.

The archetype of public data centers consists of tens of thousands of servers 
mutually interconnected via a high-speed interconnections network made of 
thousands of commodity network switches. They often run many applications that 
serve a huge number of users simultaneously. As a consequence, data 
center-hosted applications often adopt a multi-tiered model where several 
services running on distributed servers work together to satisfy a single 
client request. In such a model, performance depends greatly on the ability of 
the communication network to provide efficient and timely data transfers.

After introducing the background of the architectural design of data center 
networks and examining how such new operating environments affect network 
applications performance, we then explore the causes of performance 
degradations in such high-throughput low-latency data center networks (DCNs). 
Following that, we finally focus on presenting a collection of mechanisms we 
have designed to deal with network congestion in DCNs. In particular, as in 
public data centers virtual machines and their protocol stacks are under the 
control of the cloud tenants, we focus primarily on new designs that avoid 
modifying the protocol stack and its underlying congestion control algorithm.

In this perspective, by conducting simulation experiments and analysing real 
network traffic traces, we first identify the reasons behind the problems faced 
by TCP in DCNs: namely, unfairness, Incast congestion, a short TCP loss cycle 
and the bloated flow completion time for short-lived flows due to the 
inadequate retransmission timeout in TCP. We also propose a collection of 
traffic control schemes to address each of the problems without incurring any 
modifications to the TCP stack.

In particular, we propose: i) switch-based mechanisms, such as the so-called 
RWNDQ, IQM and HSCC schemes to address unfairness, TCP incast congestion and 
the short TCP cycle respectively; ii) hypervisor-based schemes, namely, T-RACKs 
and HyGenICC to handle any inadequate TCP RTO and inter-transport-protocol 
unfairness, respectively; and iii) SDN-based approaches, viz., SICC and SDN-GCC 
to provide an SDN implementation alternative to the switch-based IQM and 
hypervisor-based HyGenICC, respectively.

The proposed schemes are demonstrated to achieve considerable performance gains 
for cloud applications via mathematical modelling, empirical analysis, 
simulation and real-testbed implementation and experiments on various network 
scenarios and topologies. The thesis is supplemented with the prototyping of 
the switch-based schemes in the NetFPGA platform.


Date:			Monday, 31 July 2017

Time:			11:00am - 1:00pm

Venue:			Room 2130A
 			Lift 19

Chairman:		Prof. Yu Wang (MAE)

Committee Members:	Prof. Brahim Bensaou (Supervisor)
 			Prof. Gary Chan
 			Prof. Kai Chen
 			Prof. Danny Tsang (ECE)
 			Prof. Chun-Tung Chou (Comp. Sci., & Eng., UNSW)


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