How Carriers Build an NFVi to Support Network Transformation

Zhang Yu, Chief Architect of NFVI Solution, IT Product Line, Huawei, 11/20/2017

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Carrier network transformation has become a popular topic in the industry over the past few years. Factors such as increasing service traffic, changing market trends and the acceleration of 5G development put forward new requirements for network infrastructure re-construction, making transformation a must. New technologies -- including virtualization, cloud computing and SDN -- are making this transformation possible.

Since the emergence of NFV, it has been rapidly implemented over the last few years thanks to the participation and promotion of many carriers and vendors. It is widely regarded as the basis for deploying new services in the future, such as 5G network services. NFV decouples the network infrastructure -- NFV infrastructure combined with virtual infrastructure manager (VIM), referred to here as NFVi), VNFs and MANO into different layers, making an open, flexible and automated network architecture possible and providing a basis for carrier network transformation and service innovation.

Key requirements for NFVI to support the commercial use of NFV
Although NFV lays out a blueprint for network transformation, it has many technical challenges. We analyzed cases from multiple carriers and summarized the following questions that drew carriers' close attention:

Can an IT-based NFVi bear carrier-class network services?
Telecom carriers have been providing secure, reliable network services to ensure an optimal user experience for a long time, and are responsible for the critical informatization infrastructure that supports stable social and economic operations.

In the NFV era, however, network services are migrated to the NFVi composed of COTS hardware and open-source software. Can the NFVi capabilities -- such as performance, reliability and security -- meet telecom service requirements? Will user experience deteriorate due to risks introduced by innovative technologies? The answers to these questions determine whether or not NFV can be commercially applied.

Can the NFVi architecture support the continuous development and innovation of network services?
Driven by market competition and innovative technologies, carrier network transformation and innovation is a continuous process over a long time. It could even be considered a "new normal" for carriers. In this context, new technical requirements for NFVi will continuously develop. In other words, service development will also drive NFVi development.

NFVi planners and designers are faced with the following question: What NFVi architecture is flexible enough to continuously meet service requirements? For example, can the NFVi constructed for 4G networks meet 5G service requirements? The answer to this question determines whether or not the NFVi can help carriers achieve their strategic goals for network transformation, and whether carriers can avoid the technical risks and wasted investment caused by planning issues.

How should the conflict between NFVI openness and delivery difficulty in network integration be resolved?
Highly open technological systems and architectures are essential for NFVi. Only an open NFVi can effectively improve the diversity of the network services and vendor ecosystem in order to maximize profits from the network transformation.

However, NFV-related technical specifications have not been completely standardized so far. For example, the standard is not formally defined for the northbound interconnection between the NFVi and VNF/MANO. Currently, only the OpenStack API is introduced as a de-facto standard. This is likely to lead to risks in delivering projects with multi-vendor products and solutions, hindering the commercial use of NFV networks.

Carriers' concerns during NFVi construction
To address the preceding issues, carriers should pay attention to the following when planning, designing and constructing their NFVi:

Properly harden and enhance the NFVi to meet carrier-class service quality requirements. To bear carrier-class services, multiple aspects of the NFVI must be hardened and enhanced, including performance, reliability, security and maintainability.

Performance
To achieve high performance, it is important to utilize a virtual network forwarding technology with high throughput and low latency. The performance of virtual switches not only determines whether the NFVi forwarding capabilities can meet commercial requirements for existing services (such as vEPC and vBRAS services), but also is crucial for user experience of new services (such as 5G and video services) over the NFVi platform. Improving performance also reduces carriers' costs and therefore has business value.

Since Moore's Law is running out of steam, it is not sustainable to rely on the performance improvement of general-purpose processors to continuously improve forwarding performance. SR-IoV, a hardware virtualization technology, provides an alternative to solve this problem. From a long-term perspective, software-virtualization and hardware-virtualization forwarding technologies will coexist for a long time in the NFV field, and play important roles in different service scenarios.

Reliability
Carriers should comprehensively analyze and harden the system reliability of multiple layers and fields to ensure that no single point of failure (SPOF) exists with a system and achieve a carrier-class service availability.

To be specific, the reliability of each component in the data, control, management and O&M planes in the NFVI should be hardened. Techniques, such as second-level alarms, automatic fault rectification on control components and VMs, automatic backup of service data and data center (DC)-level local and remote disaster recovery, should be used to fully ensure system reliability.

Security
As the industry transitions from closed, coupled telecom equipment to an open, decoupled NFV system, security is attracting more and more attention in the NFV field. In addition to the tenant-level isolation supported by computing, network and storage virtualization technologies, NFV1 security needs to be inspected and hardened from the following aspects: physical infrastructure security, software security, service data security and system security management.

Maintainability
Maintainability is also essential for commercial use of the NFVi. Since the NFVi is built using IT technologies, O&M tasks on the IT system, such as deployment, upgrades, patch installation, capacity expansion, alarms and fault management, are also involved in the NFVi, resulting in high technical requirements for the NFVi O&M system. For example, when Linux on physical hosts functioning as compute nodes requires an upgrade, automatically upgrading all the hosts in the same cluster without interrupting services is a big challenge. If such challenges cannot be overcome, the commercial use of the NFVI will be affected.

To overcome these challenges, an automated upgrade process management system needs to be added to the NFVi lifecycle management system, so that the sequence of service migration and node upgrades can be orchestrated in a programmed and automated way, which not only accelerates the upgrade process and lowers the upgrade risks, but also reduces the workload of the O&M team.

Ensure NFV flexibility during the design to make the transition to Network Functions Cloudification (NFC) possible.
The basis of carrier networks will transform from telecom equipment rooms to distributed, multi-level data centers. Data centers (DCs) of different scales and levels are distributed in different geographical locations and provide different types of cloud resource pools, supporting distributed deployment and wide-area coverage of different services. The network access delay is different for each different level of these DCs. Since service delay on future 5G networks must be reduced to milliseconds, a large number of small-scale edge sites are required at the edge of NFVi-based networks. Therefore, NFVi must be able to host multi-level DCs and edge sites on the same network and centrally manage them.

Meanwhile, diversified services require diversified resource types. Therefore, the NFVi must allow the use of heterogeneous computing, storage and network resources. With regards to computing, for example, VMs are required as basic computing resources and bare metal resources are required to support some performance-sensitive services. In addition to common x86 processors, high-performance heterogeneous computing resources (such as FPGA) are needed for computing-intensive services. Additionally, the NFVi must be able to integrate with an upper-layer container cluster management platform to support container-based services, such as agile 5G core network functions. However, the NFVi should remain decoupled from the platform and even the PaaS layer, preventing the NFVi architecture from becoming too complex and affecting NFVi transition and flexibility.

Consider the openness and ability of NFVi vendors to deliver end-to-end solutions, and jointly accelerate the NFV ecosystem.
To address the conflict between NFVi openness and delivery risks during a project delivery phase, carriers can closely collaborate with the top vendors in the NFVI industry to jointly verify the interconnection between mainstream NFVI solutions and each vendor's components (such as VNF and MANO) in major commercial scenarios, and formulate technical specifications. At the same time, carriers should consider vendors' end-to-end solution delivery capabilities to ensure quick delivery and after-sales services.

Conclusion
During the NFVi production and deployment process, there are still some technical challenges that require carriers' close attention. However, based on Huawei's global practical cases, carriers can overcome these challenges by complying with the standard NFVI architecture defined by ETSI, selecting a proper evolution path and considering end-to-end solution design and implementation based on existing technical capabilities and practices. As virtualization, cloud computing and SDN technologies advance, NFV will become mature and gradually transition to NFC to support cloud-native network services. Cloud-based NFVi will become the standard infrastructure for future 5G networks, and lead to infinite possibilities for service development and innovation. — Zhang Yu, Chief Architect of NFVI Solution, IT Product Line, Huawei