nd present an integrated view of data. Now each EMS can be from a different vendor and based on a different technol- ogy. Moreover the different EMS may not talk in a common vocabulary or have a common format for data. Then how is it possible to have a single NMS for multiple EMS? This chapter gives you an understanding on the requirement to have standards for interaction between element management layer (EML) and network manage- ment layer (NML). It has a detailed discussion on the MTNM (Multi Technology Network Management) standards from TMF (TeleManagement Forum). MTNM is a copyright of TMF (www.tmforum.org) 8.1 Introduction Consider that service provider X wants to use your EMS and NE with their NMS solution. To get fault data from an EMS, the NMS solution from X sends query "getAlarmList," which your EMS does not understand and cannot respond to. The obvious solution is to write an adaptor (a process that acts as mediator between two modules and performs format conversion in message/data for the two modules to interoperate) that converts message/data from the format of NMS solution X to a format that your EMS can understand and vice versa. Now there is another service provider Y who also wants to use your EMS and sends a different query "getFaultList" for the same operation. For interoperability another adaptor needs to be written. For NMS solution X to interact with an EMS other than yours will also require an adaptor. So in a multitechnology (underlying protocol), multivendor environment, where interaction between EML and NML is not standardized, for an NMS to Fundamentals of EMS, NMS and OSS/BSS collect data from multiple EMS or for an EMS to be used with multiple NMS, the possible method of operation would require writing multiple adaptors. Writing adaptors is not a cost-effective option in the evolving telecom industry where the major investment could end up in writing adaptors. Hence there was a need to have standards for interaction between EML and NML. For the interaction to be standardized, the foll