Tuesday, March 8, 2011

Difference Between NMS and EMS

Haah..... When so many people search Google for this, well I thought it wouldn't harm to write a note on this basic concept.

"Not for Pros".

NMS - Network Management System
EMS - Element Management System

Well, lets define what is a network Node. A node is a single device or entity usually a single physical box, such as a computer, server, router, switch, etc. The node, usually is connected to other nodes in the network, interacting and exchanging data in the language the local network devices understand.

Of course a Network, is a bunch of interconnected nodes where communication between them is usually possible at will if any device wants to talk to other devices.

EMS is a system which manages a single Node or group of similar Nodes. The word 'Element' refers to a node in a network.

NMS is a system which manages the entire network or multiple networks.

EMS can sit in one part of the network and manage node/nodes in other part of the same network(or a different network) or it can sit inside the managed device itself and extend management interface to the outside world.

NMS can sit inside the network or outside the network (but can reach the network) monitoring all the nodes in the network or most of the nodes in the network and the connections among them.

So, the main difference between EMS and NMS is the ability of NMS to understand the inter-relation between the devices of the network. An EMS does not understand the communication links or relationships between devices. It only knows the intricacies of a single device, though it can manage multiple devices of similar type, it treats all the nodes in that group as independent devices not recognizing how they interact among themselves or their complementing functionality or what they mean to each other.

Another functionality of NMS which differentiates it from EMS is, its ability to monitor the inter-links among the devices, or the connecting links in the entire network or the ability to report the faults occurring at various nodes in the network and also predict how such faults disrupt the communication links in the network causing the whole network to not function or malfunction.

So, one can roughly say,

NMS = EMS + Link/Connectivity Management + Management of Relationships among devices + Understanding of contributions of each node in the functioning of the network itself

How does NMS or EMS look like?

Well, both of them can be just softwares with/without graphical interface running in a separate server or in a normal desktop computer or in a network node/device (usually EMS, with a web server).

Current trend is, a server with GUI developed in java or with a web server or an enterprise server.

NMS can perform very complex operations with respect to the network as a whole. The functions are termed as FCAPS.

Fault - Report Link Failures and node failures or faults in the part of a device

Configuration - Modify/enable functionality of a device/node

Accounting - Perform billing, accounting related functions for a commercially used business network

Performance - Measure/improve performance or utilization of the network or devices

Security - Protect the devices or network from harmful or illegal access, implement hierarchical access policy within the network, provide user management (human users accounts) in conjunction with device/network/service access

Literally an NMS can do anything with the network if anyone is willing to put such functionality in the NMS. It can create, maintain, provision or destroy a network or a device within the network. From sending an electronic message to operating a robotic arm to mechanically connect or disconnect devices, to showing the mobile users and their movements on a screen to shutting a water pipe or door, or closing a dam, to anything. The possibilities are endless.

But the devices in that network should be designed in such a way that an NMS can manipulate them easily.

The last notable capability of an NMS is to manage dissimilar devices that is differing in functionality, differing by vendor, or differing in its basic nature (the language a device understands, e.g. IP device and Telecom Device).


  1. Its a very nice article . Its like a glance explaining very soon..

  2. Thanks your article is amazingly simple :)

  3. thank you so much for such a simple and informative article.......... very nice.....

    it would be great if you would have explained about SNMP too..... :)

  4. @Ranju: I'm glad that you found it useful. Thanks.

  5. Done. http://murkymind.blogspot.com/2011/04/snmp-simple-network-management-protocol.html

  6. You seemed a bit biased to NMS over EMS ;)

    My doubt is, how can an NMS be considered as EMS+etc? Can NMS do what all EMS can do? For example, an element manager can do almost all the configuration possible for a single node right? Can NMS do that? Lets take the example of the product we worked... We can make a port beacon using EMS, can an NMS application do that?

    I am honestly confused... I am not simply asking to refute your post...

  7. haha.... I think you haven't seen the actual EMS.... the EMS you are referring to which was a part of an NMS product, ya very well it can work as independent product, but if you remember, it's low level protocol querying machine was part of NMS architecture..... So, this EMS can be assumed as just one component of NMS... instead of calling it EMS, they could've called with any other name...

    well, the usual actual so called EMSes are standalone products targeted on a single product.... once you cover various different products in your EMS, it becomes NMS :)

    And yes, if you can do something in EMS, the same can be implemented in NMS without any doubt...

  8. Yes da... I remember... we were allowed to do zoning and all using the (misnomer) EMS product we worked on... good explanation...

  9. amazing information...thanks a tonn :)

  10. hi, once again excellent post!! I have a doubt how do EMS and NMS communicate? which is the standard protocol? can two NMS communicate between them to request information? I'm pretty new in all this and have many doubts, cause it is clear that NE communicate to NMS through SNMP for example, but how do actually NMS communicate between them?

  11. Hi, communication between EMS and NMS or between two NMSes is a very special situation. It happens only in distributed architecture. That is one part of the network is managed by NMS1 and other part is managed by NMS2. In this scenario, both of them can exchange the management information in two ways.

    1. Implement SNMP agent within themselves so that the other NMS can use SNMP protocol itself to query info from this NMS.

    2. Use a custom exchange interface like XML or SOAP to exchange info between two NMSes.

  12. can anyone explain me the scenario where EMS is used and why??are EMS deals only with non snmp device?? I am clear why NMS are being used..but confused with the use of EMS?

  13. Usually EMS is provided by the device vendor itself. It is shipped along with the product or as part of the device itself as a monitoring and diagnostic tool to manage one device or group of similar devices. EMS is not limited to non-snmp devices.

  14. Hi

    I have a doubt. You said intercommunication between the devices is not possible using EMS and its possible using NMS.
    Though you have similar devices under one EMS, EMS will treat them as independent devices and only collects the data and provision independently and discovers the nodes.

    I think the same can be done by NMS. Can you explain an example like how intercommunication is not possible using EMS, possible by NMS?

    Also it will be great if you can give the similar notes for OSS/BSS?