A Cheat Sheet for Understanding “NFV Architecture”

Short on time?

Need a quick refresher on NFV (Network Functions Virtualization) terminology/ architecture in easy to understand language?

Then find below a summary of SEVEN key blocks in NFV architecture, which is all you need to know to get started with the NFV architectural framework. Follow the block numbers and definitions below.

But before that what is NFV? According to ETSI

“Principle of separating network functions from the hardware they run on by using virtual hardware abstraction”

In short, running network functions on commodity generic hardware such as servers using virtualization technology for the purpose of reduced costs.

Now lets have a quick overview of important blocks in NFV architecture as per ETSI

NFV Architecture

1. VNF (Virtualized Network Function):

A VNF is the basic block in NFV Architecture. It is the virtualized network element. For example when a router is virtualized, we call it Router VNF; another example is base station VNF. Even when one sub-function of a network element is virtualized, it is called VNF. For example in router case, various sub-functions of the router can be separate VNFs which together function as virtual router.

Other examples of Virtual Network Functions include firewalls, IPS, GGSN, SGSN, RNC, EPC etc.

2. EM (Element Management ):

This is the element management system for VNF. This is responsible for the functional management of VNF i.e. FCAPS ( Fault, Configuration, Accounting, Performance and Security Management). This may manage the VNFs through proprietary interfaces. There may be one EMS per VNF or an EMS can manage multiple VNFs. EMS itself can be a VNF.

3. VNF Manager:

A VNF Manager manages a VNF or multiple VNFs i.e. it does the life cycle management of VNF instances. Life cycle management means setting up/ maintaining and tearing down VNFs.

Additionally VNFM ( VNF Manager) does the FCAPS for the virtual part of the VNF.

The difference between EM and VNFM should be noted. EM does the management of functional components. While the VNFM does the management for the virtual components. An example would make it clear. In case where Mobile core is virtualized, the EM will do the management of the functional part ( for example issues related to mobile signaling), while VNFM will do the management for the virtual part ( for example issues related to bringing up an VNF itself)

4. NFVI (Network Functions Virtualization Infrastructure):

NFVI ( NFV Infrastructure) is the environment in which VNFs run. This includes Physical resources, virtual resources and virtualization layer, described below.

4.1 Compute, Memory and Networking Resources:

This is the physical part in NFVI. Virtual resources are instantiated on these physical resources. Any commodity switch or physical server/storage server is part of this category.

4.2 Virtual Compute, Virtual Memory and Virtual Networking Resources:

This is the virtual part in NFVI. The physical resources are abstracted into virtual resources that are ultimately utilized by VNFs.

4.3 Virtualization Layer:

This layer is responsible for abstracting physical resources into virtual resources. The common industry term for this layer is “Hypervisor”. This layer decouples software from hardware which enables the software to progress independently from hardware.

Suppose, there is no virtualization layer, one may think that VNFs can run on physical resources directly; However, as such by definition we CANNOT call them VNF nor it would be NFV architecture. They may appropriately be called PNFs ( Physical Network Functions).

The network can also be virtualized using Software Defined Networking (SDN) layer.

5. VIM (Virtualized Infrastructure Manager):

This is the management system for NFVI. It is responsible for controlling and managing the NFVI compute, network resources and storage resources within one operator’s infrastructure domain. It is also responsible for collection of performance measurements and events.

6. NFV Orchestrator:

Generates, maintains and tears down network services of VNF themselves. If there are multiple VNFs, orchestrator will enable creation of end to end service over multiple VNFs.

NFV Orchestrator is also responsible for global resource management of NFVI resources. For example managing the NFVI resources i.e. compute, storage and networking resources among multiple VIMs in network.

The Orchestrator performs its functions by NOT talking directly to VNFs but through VNFM and VIM.

Example:

Let’s say there are multiple VNFs which need to be chained to create an end to end service. One example of such case is a virtual Base station and a virtual EPC. They can be from same or different vendors. There will be a need to create an end to end service using both VNFs. This would demand a service orchestrator to talk to both VNFs and create an end to end service.

Note that VIM,VNFM and NFVO together are also called Management and Network Orchestration (MANO)

7. OSS/BSS(Operation Support System/Business Support System)

Last but not the least in the discussion of NFV architecture– OSS/BSS refers to OSS/BSS of an operator. OSS deals with network management, fault management, configuration management and service management. BSS deals with customer management, product management and order management etc.

In the NFV architecture, the current BSS/OSS of an operator may be integrated with the NFV Management and Orchestration using standard interfaces.

That’s it about NFV architecture !

For more details on NFV including use cases and its relation to SDN, send me an email so I can share NFV mind map with you.

Drop me a comment below and let me know what do you think about this “Cheat Sheet” for NFV Architecture.