ATM Private Network-to-Network Interface (PNNI) adopts hierarchical routing which reduces nodal and link information to accomplish scalability and efficiency in large ATM networks. We design and evaluate two different aggregation schemes (Asymmetric Simple and Full-Mesh). Information aggregated includes available bandwidth, delay and cost. In the past, the definition of the cost function has received much less attention. We study two approaches: the Markov Decision Process (MDP) approach and the Competitive On-Line (COL) routing approach. Our simulation results show that the proposed asymmetric simple aggregation scheme yields a very good performance while it significantly reduces the amount of advertised information. Among these two link cost functions, the MDP-based approach provides a systematic way of defining the call admission function and yields a better network utilization than the COL-based approach.