Sun concurrently serves as a full-time professor in the Department of Information Management, National Taiwan University. Before landing the current roles, Sun assumed various positions in relevant fields, namely a member of Technical Staff at Bell Communications Research, Inc. in the United States; professor in the Department of Information Management, National Taiwan University while serving as the Director of the Division of Network Management, Computer and Information Networking Center; Chairman of Lin Chien-Cheng Cultural Foundation; member of the Taipei City Public Wireless Local Area Network Management Committee, Taipei City Government; member of the Review Committee under the Public Construction Commission, Executive Yuan; and member of the Information Promotion Committee, Central Bank of the Republic of China (Taiwan), all of which helped him gain plentiful experiences.