What are Virtualised Network Functions?
There’s a lot of buzz around NFV (Network Function Virtualisation) and there are a number of terms that seem to overlap: network softwarization, network function virtualisation, virtual or virtualised network function and service chaining. Add software decoupling and network function disaggregation and we have a slew of acronyms and terms.
Software is eating the world.
This 2011 quote is attributed to Marc Andressen (developer of the Netscape browser and founder of Andressen-Horowitz venture capitalists), and neatly summarises the well-established trend “softwarization” of products and services. Over recent years we’ve seen this process increasing in networks — here we’ll briefly introduce the terms and describe how we’re using Software Defined Networking.
Within networks there is an hierarchy of terms.
Network Softwarization and Software Defined Networking (SDN)
The terms are broadly synonymous and SDN now more commonly used to describe the concept that the network can be programmable leading to agility, cost reduction, security and efficiency.
Network Function Virtualisation (NFV)
More recently network function virtualisation broadly describes the separation of the hardware from the software needed to run network functions, services and protocols.
This disaggregation means that commercial off the shelf (COTS) x86 hardware (or x86 virtual machines) can be deployed and integrated horizontally to replace the vertical stack vendor solutions — freeing customers from vertically integrated products where aspects of the network stack may need to be sacrificed in order to use a particular vendor’s product.
The benefits of NFV include:
- better scaleability and agility
- reducing power consumption
- increasing security
- reducing physical rack space
- reducing opex
- reducing capex
Virtual Network Functions (VNFs)
VNFs are defined as virtual services running on COTS hardware which previously ran on proprietary, dedicated hardware. Common VNFs include virtualized routers, firewalls, WAN optimization, and NAT services. Most VNFs are run in virtual machines.
VNFs can help increase network scalability and agility, while also enabling better use of network infrastructure resources. Other benefits include reducing power consumption and increasing security and available physical space, since VNFs replace physical hardware. This also results in reduced operational and capital expenditures.
VNFs are often linked together in “service chains”. Service chaining means that end-to-end data streams of data pass through a series of functions, for example passing through a firewall, encryption and software-defined WAN. We compose multiple network functions in our wholesale broadband services: virtual L2TP routers talk to virtual LNSs which authenticate against virtual RADIUS services before passing traffic through virtual CGNAT and/or NAT64 routers.
Software Defined WAN (SD-WAN)
Software Defined Wide Area Network (SD-WAN) is a specific application of SDN. Commonly an SD-WAN product is combined with commodity Internet access, and is used as an alternative to single-provider MPLS connectivity to link enterprise branch offices to their headquarters. With SD-WAN there is more flexibility to choose different technologies for spoke sites, and different types of traffic can have policies applied to route them down an appropriate link: low latency interactive traffic may take a more expensive link than high bandwidth bulk data, and voice/video calls might be sent redundantly over multiple links to ensure completely seamless failover.
SD-WAN routers can often be deployed as VNFs. For example, we host SD-WAN hubs for ISPs to the TV/broadcast/film production market.