As a result, EMSs require routines to map between older agent interfaces, such as TL1 or SNMP and their object-based management functions. These mappings are difficult to establish and maintain. Each change in the agent forces a change to the EMS' mapping code. Though change must be handled regardless of the nature of the embedded agent, the remapping, as well as the handling of inevitable content changes, greatly adds to the complexity of EMS development. Software products exist to bridge this gap, but it is not uncommon for EMS releases to lag significantly behind equipment releases.
New equipment is trialed and often deployed without an adequate management system.
Older systems built from top to bottom around either TL1 or SNMP leverage the specific facilities offered by the selected protocol. Telcordia's NMA, for example, is a highly efficient and scalable fault management system that uses TL1. As a result, new equipment today often needs to have both a TL1 and an SNMP agent. Traditional providers that have more TL1-based management systems will generally choose TL1. To address a wider market, an equipment vendor would want to embed both interfaces.