A proxy agent for communicating data components between a Network Management System (NMS) which supports a first network management protocol, for example Simple Network Management Protocol (SNMP), and one or more network elements which support a second protocol, for example Transaction Language 1 (TL1). The proxy agent comprises a directory for storing the data components wherein each data component is associated with a first data component identifier which is compatible with the first protocol, and with a second data component identifier which is compatible with the second protocol. The directory provides an inherent mapping between protocols and obviates the need for a separate mapping component. The directory may conveniently comprise a Lightweight Directory Access Protocol (LDAP) directory.