The next generation Internet is supposed to support a wide range of network applications with highly diverse requirements. Network virtualization, which is expected to play a key role in the future Internet, allows a large number of service providers to offer various network services upon shared network infrastructures. Therefore, selecting the appropriate network service for supporting the requirement of each application becomes an important issue in the virtualization-based future Internet. The research presented in this paper explores application of the Service-Oriented Architecture (SOA) in network virtualization to address this problem. This paper proposes a SOA-based broker system for automatic network service discovery and selection, and develops an information update mechanism for improving the broker performance. Multiple attribute decision making technique is also employed in the paper for developing an algorithm that can be used in the broker system for selecting the appropriate network service for each application.