The IMA (Inverse Multiplexing over ATM ) protocol allows multiple E1 links to be used as a group to provide an aggregate bandwidth. The ATM (Asynchronous Transfer Mode) transmission protocol is already used to carry all of the signalling, voice and data information for many networks, e.g. 3G mobile networks. The use of IMA ensures that the bandwidth from each E1 link is proportionally used. This avoids any one link becoming a bottleneck to the service. When additional bandwidth is required an extra link can be added with little or no management of the ATM or application layers required.