In recent years, due to the impact of new services and new traffic models on operator networks, traditional Broadband Remote Access Server (BRAS) equipment with tight coupling of control and forwarding has exposed a lack of scalability. At the same time, telecommunications networks are witnessing a historic transformation, for which NFV is one of the key technologies. To introduce NFV into Metropolitan Area Networks (MANs), BRAS equipment should be taken into consideration first.
Among the Global Telecom Business (GTB) Innovation Awards 2017 recently announced by the GTB, an authoritative media body specialised in the international telecommunications industry, China Mobile Research Institute (CMRI) and ZTE jointly won the "Infrastructure Innovation Award 2017" for the innovative vBRAS solution.
What features of CMRI's innovative vBRAS solution are highly recognized by the industry? Li Han, Vice Director of the Network Technology Research Institute, CMRI, was recently interviewed by C114, and discussed the reconstruction of CMRI's vBRAS solution to the industry concept as well as its current progress and the future prospects.
C/U Separation: Technological Innovation and Optimal Evolution
BRAS is the breakthrough point of the current fixed network digital transformation of operators. Li Han told C114 that the performance of the current vBRAS solution based on x86 servers cannot meet the requirements of large-scale MAN applications, while "C/U separation" (control and forwarding separation) is a "reconstruction" measure for traditional BRAS equipment. This measure not only meets CMCC's needs for developing a large number of broadband MAN users, but also completely solves the problems of traditional BRAS equipment, such as low resource utilization, long time-to-market of new services, and complexity in operation and maintenance. When CMRI first proposed the vBRAS with a C/U separation architecture, many operators and vendors adopted a wait-and-see attitude. However, with the continuous breakthroughs and bright commercial prospects of the vBRAS solution, this idea is gradually recognized by the industry.
In terms of network architecture design, CMCC proposes the transformation from voice and data orientation to content and traffic orientation, which is exactly CMCC's Telecom Integrated Cloud (TIC) architecture. According to Li Han, the C/U separation architecture of vBRAS well matches CMCC's TIC architecture, not only from the perspective of fixed network architecture or the edge of MANs, but also from the perspective of the overall network architecture.
According to Li Han, the C/U separation architecture of vBRAS provides a basis for exploration into Fixed Mobile Convergence (FMC) in the future. “The vigorous development of fixed network business has brought CMCC an opportunity to introduce new technologies and concepts, and to replace traditional CT equipment with IT ideas," said Li Han, "in the future FMC, the control plane is definitely centralized, while the media/service plane is distributed. C/U separation is the technical prerequisite for convergence of the control plane."
According to C114, CMCC has publicly highlighted the following features of the vBRAS solution with C/U separation:
The forwarding plane and the control plane are completely separated.
The control plane is centralized and cloud-based, and the forwarding plane is localized.
The control plane is based on the cloud, and the forwarding plane is based on high-performance hardware.
Both the control plane and the forwarding plane use standard interfaces to promote standardization and generalization of high-performance forwarding planes.
Li Han further stressed that CMCC attached greater importance to the following benefits from the new network structure: network flexibility, rapid response to new service provisioning, and support for future VASs. "For example, the time-to-market period of new services is shortened from six months or more to about two weeks. In addition, a traditional BRAS device accommodates 30,000 users, while the control plane with C/U separation can support ten million users. That is to say, a single forwarding plane can support at least 100,000 users, and the user access rate can be increased by five to six times. In addition, the control planes can be deployed in a unified manner so that the total configuration can be reduced by more than 90 percent. The new architecture lowers the cost, enhances the performance, and simplifies operation and maintenance. What's more, there is still great potential to tap."
Li Han pointed out, what CMCC pursues in the vBRAS solution is high efficiency, generalization, and low cost. However, generalization does not necessarily mean the use of x86 servers. It now appears that NP architecture can better meet the needs of operators in high traffic scenarios. ZTE is the major partner of CMCC for the vBRAS solution. Hu Longbin, Deputy General Manager of ZTE's Bearer Network product line, said in the C114's interview that, the performance of general x86 servers cannot meet the requirements of large-capacity and low-delay services, and it would be a rational choice to use high-performance hardware as the forwarding plane of vBRAS. In the future, as the forwarding plane and the control plane interfaces are standardized, the forwarding plane can also general x86 servers as a supplement to carry VoIP, TR069, and other services with high sessions but low traffic.
Next Step: Standards Formulation and Large-Scale Deployment
This GTB award indicates that CMCC's vBRAS solution has gained wide recognition in the industry. However, according to Li Han, only large-scale deployment can be deemed as a success. CMCC will strengthen the guidance on industrial partners to create benign industrial ecological chains, just like the PTN and 100 GHz WDM ecological chains built by CMCC.
First, standards should be formulated before large-scale deployment. Hu Longbin said that ZTE will work with CMRI to develop a unified C/U separation architecture, formulate related standards, and use standard interfaces so that other vendors in the industrial chain can be involved to jointly promote the development and maturity of new technologies. It is reported that both parties have developed related industry standards with the CCSA. Li Han emphasized that these standards will be promoted in the BBF, ONF, and other international and domestic standards organizations.
Second, hardware architecture should be defined and its interoperability needs to be verified, including verification of networking capabilities, service loading capacity, and security and scalability of the control plane. In addition, distributed databases should be deployed. "A centralized control plane is like a concentrated brain. The network with a centralized plane will be more secure at lower cost, which is the natural attributes of IT architecture," said Li Han.
According to C114, pilot verification of the vBRAS solution with C/U separation is expected to be launched in existing networks of CMCC, to carry major services from traditional BRAS equipment, thereby accelerating its commercialization process. "At present, we are conducting the phase-II lab test. In July, we will launch pilot tests of the vBRAS with a C/U separation architecture in the existing networks in six provinces, with the control plane supporting up to 1,000,000 users. In November, the control plane will support up to ten million users," Li Han disclosed.
The technical feasibility of the C/U separation architecture has been verified in the previous standards formulation, solution development, and laboratory test phases; and this architecture has met the pilot conditions. After the pilot verification, the vBRAS with C/U separation is likely to become a dominant form of CMCC's BRAS equipment. The vBRAS control plane is located in the core TIC in the provincial center. Each province is expected to deploy 1–3 vBRAS control plane instances with cross-DC hot standby redundancy. A single vBRAS control plane supports ten million sessions, and manages the vBRAS forwarding planes within the province. This will be a great potential market.
Hu Longbin added two points regarding the performance and standards:
Currently, a single control plane instance of the vBRAS supports 1 million user sessions, and will be expanded to support 20 million user sessions in the future, meeting the NovoNet business plan of CMCC.
The control plane and the forwarding plane interfaces are being standardized for decoupling of the control and forwarding planes of multiple vendors.
As the industry's first vendor who has completed the vBRAS technical verification tests of the C/U separation architecture in the laboratories of CMCC and China Telecom, ZTE will continue to work with CMCC on equipment forms, laboratory tests, existing network verification, and equipment standardization. In addition, ZTE will improve the reliability mechanisms of vBRAS and formulate related interface standards to promote the commercial use of vBRAS in CMCC's existing networks and jointly build a sound industrial ecological chain.