Currently, there are no Internet access authentication protocols available that are lightweight, can be carried over arbitrary access networks, and are flexible enough to be used in all the likely future ubiquitous mobility access contexts. The IETF PANA (Protocol for carrying Authentication for Network Access) work aims to provide a protocol that will be a network-layer authentication carrier for access networks that support IP. The article proposes a PANA/GSM authentication protocol for heterogeneous network access as a step towards filling this gap. A security analysis of the PANA/GSM protocol is also provided. The article aims primarily at contributing to the design of authentication protocols suitable for use in future heterogeneous Internet access environments supporting ubiquitous mobility.