An element management system (EMS) manages one or more of a

specific type of network elements (NEs).

Using an EMS a user can manage all the features of each NE

individually, but not the communication between NEs.

Communication between NEs is managed by the network

management system (NMS).

A network management system is a combination of hardware and

software used to monitor and administer a network.

Network management refers to the maintenance and

administration of large scale computer networks at the top

level.

In brief,If network vendor wants to manage multiple

EMS,vendor can go to NMS.

If network vendor wants to manage multiple EMS,vendor can

decide to go for NMS.

If network vendor want to manage one or more of a specific

type of network elements (NEs),vendor can decide to go for EMS.