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Service providers have long covetted the efficiencies achieved by hyperscale data centre operators running applications on servers. The telecom operators want their networking functions to run on servers in the cloud, instead of having to buy - and maintain - custom boxes running proprietary software for each new service.

Dor Skuler

In October 2012, several of the world's leading telecom operators published a document to spur industry action. Entitled Network Functions Virtualisation - Introductory White Paper, the document stressed the many benefits such a telecom transformation would bring: reduced equipment costs, power consumption savings, portable applications, and nimbleness instead of ordeal when a service is launched.

Eighteen months on and much progress has been made. Operators and vendors have been identifying the networking functions to virtualise on servers, and the impact Network Functions Virtualisation (NFV) will have on the network.

A group within ETSI, the standards body behind NFV, is fleshing out the architectural layers of NFV: the virtual network functions layer that resides above the management and orchestration one that oversees the servers, distributed in data centres across the network.

In the lab, network functions have been put on servers and then onto servers in the cloud. "Now we are at the start of the execution phase: leaving the lab and moving into first deployments in the network," says Dor Skuler, vice president and general manager of CloudBand, the NFV spin-in of Alcatel-Lucent. Skuler views 2014 as the year of experimentation for NFV. By 2015, there will be pockets of deployments but none at scale; that will start in 2016.

SDN is a simple way for virtual network functions to get what they need from the network through different commands

Deploying NFV in the network and at scale will require software-defined networking (SDN). That is because network functions make unique requirements of the network, says Skuler. Because the network functions are distributed, each application must make connections to the different sites on demand. "SDN is a simple way for virtual network functions to get what they need from the network through different commands," he says.

CloudBand's customers include Deutsche Telekom, Telefonica and NTT. Overall, the company says it is involved in 14 customer projects.

CloudBand 2.0

CloudBand has developed a management and orchestration platform, and launched an 'ecosystem' that includes 25 companies. Companies such as Radware and Metaswitch Networks are developing virtual network functions that use the CloudBand platform.

More recently, CloudBand has upgraded its platform, what it calls CloudBand 2.0, and has launched its own virtualised network functions (VNFs) for the Long Term Evolution (LTE) cellular standard. In particular, VNFs for the Evolved Packet Core (EPC), IP Multimedia Subsystem (IMS) and the radio access network (RAN). "These are now virtualised and running in the cloud," says Skuler.

SDN technology from Nuage Networks, another Alcatel-Lucent spin-in, has been integrated into the CloudBand node that is set up in a data centre. The platform also has enhanced management systems. "How to manage the many nodes into a single logical cloud, with a lot of tools that help applications," says Skuler. CloudBand 2.0 has also added support for OpenStack alongside its existing support for CloudStack. OpenStack and CloudStack are open-source platforms supporting cloud.

For the EPC, the functions virtualised are on the network side of the basestation: the Mobility Management Entity (MME), the Serving Gateway and Packet Data Network Gateway (S- and P-Gateways) and the Policy and Charging Rules Function (PCRF).

IMS is used for Voice over LTE (VoLTE). "Operators are looking for more efficient ways of delivering VoLTE," says Skuler. This includes reducing deployment times and scalability, growing the service as more users sign up.

The high-frequency parts of the radio access network, typically located in a remote radio head (RRH), cannot be virtualised. What can is the baseband processing unit (BBU). The BBUs run on off-the-shelf servers in pools up to 40km away from the radio heads. "This allows more flexible capacity allocation to different radio heads and easier scaling and upgrading," says Skuler.

Skuler points out that virtualising a function is not simply a case of putting a piece of code on a server running a platform such as CloudBand. "The VNF itself needs to go through a lot of change; a big monolithic application needs to be broken up into small components," he says.

"The VNF needs to use the development tools we offer in CloudBand so it can give rules so it can run in the cloud." The VNF also needs to know what key performance indicators to look at, and be able to request scaling, and inform the system when it is unhealthy and how to remedy the situation.

These LTE VNFs are designed to run on CloudBand and on other vendors' platforms. "CloudBand won't be run everywhere which is why we use open standards," says Skuler.

Pros and cons

The benefits from adopting NFV include prompt service deployment, "Today it can take 9-18 months for an operator to scale [a service]," says Skuler. The services, effectively software on servers, can scale more easily whereas today, typically, operators have to overprovision to ensure extra capacity is in place.

Less equipment also needs to be kept by operators for maintainance. "A typical North America mobile operator may have 450,000 spare parts," says Skuler; items such as line cards and power supplies. With automation and the use of dedicated servers, the number of spare parts held is typically reduced by a factor of ten.

Services can be scaled and healed, while functionality can be upgraded using software alone. "If I have a new verison of IMS, I can test it in parallel and then migrate users; all behind my desk at the push of a button," says Skuler.

The NFV infrastructure - comprising compute, storage, and networking resources - reside at multiple locations - the operator's points-of-presence. These resources are designed to be shared by applications - VNFs - and it is this sharing of a common pool of resources that is one of the biggest advantages of NFV, says Skuler.

But there are challenges.

"Operating [existing] systems has been relatively simple; if there is a faulty line card, you simply replace it," says Skuler. "Now you have all these virtual functions sitting on virtual machines across data centres and that creates complexities."

An application needs to be aware of this and provide the required rules to the management and orchestration system such as CloudBand. Such systems need to provide the necessary operational tools to operators to enable automated upgrades and automated scaling as well as pinpoint causes of failures.

For example, an IMS core might have 12 tiers. In cloud-speak, a tier is one of a set of virtual machines making up a virtual network function. Examples of a tier include a load balancer, an application or a database server. Each tier consists of one or more virtual machines. Scaling of capacity is enabled by adding or removing virtual machines from a tier.

In a cloud deployment, these linkages between tiers must be understood by the system to allow scaling. Two tiers may be placed in the same data centre to ensure low latency, but an extra pair of the tier-pair may be placed in separate sites in case one pair goes down. SDN is used to connect the different sites, says Skuler: "All this needs to be explained simply to the system so that it understands it and execute it".

That, he says, is what CloudBand does.