Author ORCID Identifier

Date Available


Year of Publication


Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation




Computer Science

First Advisor

Dr. Zongming Fei

Second Advisor

Dr. James Griffioen


Computer networks are becoming more complex and challenging to operate, manage, and protect. As a result, Network policies that define how network operators should manage the network are becoming more complex and nuanced. Unfortunately, network policies are often an undervalued part of network design, leaving network operators to guess at the intent of policies that are written and fill in the gaps where policies don’t exist. Organizations typically designate Policy Committees to write down the network policies in the policy documents using high-level natural languages. The policy documents describe both the acceptable and unacceptable uses of the network. Network operators then take the responsibility of enforcing the policies and verifying whether the enforcement achieves expected requirements.

Network operators often encounter gaps and ambiguous statements when translating network policies into specific network configurations. An ill-structured network policy document may prevent network operators from implementing the true intent of the policies, and thus leads to incorrect enforcement. It is thus important to know the quality of the written network policies and to remove any ambiguity that may confuse the people who are responsible for reading and implementing them. Moreover, there is a need not only to prevent policy violations from occurring but also to check for any policy violations that may have occurred (i.e., the prevention mechanisms failed in some way), since unwanted packets or network traffic, were somehow allowed to enter the network. In addition, the emergence of programmable networks provides flexible network control. Enforcing network routing policies in an environment that contains both the traditional networks and programmable networks also becomes a challenge.

This dissertation presents a set of methods designed to improve network policy enforcement. We begin by describing the design and implementation of a new Network Policy Analyzer (NPA), which analyzes the written quality of network policies and outputs a quality report that can be given to Policy Committees to improve their policies. Suggestions on how to write good network policies are also provided. We also present Network Policy Conversation Engine (NPCE), a chatbot for network operators to ask questions in natural languages that check whether there is any policy violation in the network. NPCE takes advantage of recent advances in Natural Language Processing (NLP) and modern database solutions to convert natural language questions into the corresponding database queries.

Next, we discuss our work towards understanding how Internet ASes connect with each other at third-party locations such as IXPs and their business relationships. Such a graph is needed to write routing policies and to calculate available routes in the future. Lastly, we present how we successfully manage network policies in a hybrid network composed of both SDN and legacy devices, making network services available over the entire network.

Digital Object Identifier (DOI)

Funding Information

The research in this dissertation was supported by the National Science Foundation under grant ACI-1541426 in 2018.

The research in this dissertation was supported by the National Science Foundation under grant CNS-1551453 in 2019.

The research in this dissertation was supported by the National Science Foundation under grant ACI-1642134 in 2020.