Future Development Path of Home Broadband Infrastructure

Part 01: Background

China Mobile Group has further upgraded its cloud-network integration strategy, built a ubiquitously integrated computing network, and created a "one-point access, ready-to-use" computing service, allowing computing power to flow into thousands of households like water, electricity, heating, and gas, becoming the fifth essential means of production in people's daily lives.

The China Mobile Computing Network White Paper proposes the goal vision of "networks that reach everywhere, computing power that is ubiquitous, and intelligence that is all-encompassing." To achieve this vision, the integration of computing and networks in network infrastructure is the foundation, and the integration of cloud and networks is inevitable, gradually moving towards the integration of computing and networks.

Based on the accumulation of China Mobile's Smart Home Operation Center's independent and controllable hundreds of millions of household terminals, Hejia Cloud Network's accelerated network construction, and network infrastructure research and development, this paper attempts to explore the evolution strategy and direction of broadband infrastructure in the context of computing power networks from three dimensions: network element architecture, computer room deployment, and computing-network integration.

Part 02: Evolution of the control-transmission separation architecture

Broadband network element infrastructure includes two categories: user-side equipment (broadband gateway) and operator-side equipment (OLT, BRAS equipment). Among them, broadband gateway, OLT, aggregation switch, together with optical splitter, optical fiber cable, and network cable together constitute the commonly referred to access network; BRAS and other network element equipment (routers, switches, etc.) in the same position together constitute the commonly referred to metropolitan area network. It is worth mentioning that the aggregation switches, routers and other network elements involved are only used for general routing and switching functions, and are not network elements unique to broadband networks, so they are not described separately.

The advantages of the network element's control-forwarding separation architecture are mainly reflected in the following aspects:

• Maximize the performance of the forwarding plane: The forwarding plane forwards at line speed and continuously sinks to a lower position to get as close to the user as possible, achieving traffic offloading nearby and high-speed one-hop access to the cloud, which is the physical guarantee for ultra-low latency and ultra-high bandwidth service experience.
• Maximize the advantages of centralized control and flexible elasticity of the control plane: The control plane has complex logic control, which is continuously graded and raised to a higher level, realizing centralized management and control of the forwarding plane and value-added services, and improving network elasticity and reliability;
• Realize the integration and unification of heterogeneous networks: After the forwarding and control separation of different network elements, the forwarding plane functions converge, the control plane functions converge, and further horizontal penetration is achieved to achieve the unification of different network elements and the normalization of heterogeneous networks, greatly simplifying the network architecture;
• Decouple network element functions and get rid of vendor lock-in: After the separation of transmission and control, multi-vendor device-level interoperability can be achieved through standardization of north-south interfaces, eliminating vendor lock-in.

The evolution of separation of control and transmission of network elements may seem to contradict the evolution of computing-network integration, but in fact, it is an organic unity. In particular, the third advantage mentioned above will form a widely covered standardized terminal room with data centers as the carrier, with the network as the basis, end-edge collaboration, edge-edge collaboration, and cloud-edge collaboration, and activate the computing power of end, edge, and cloud. Separation of control and transmission reshapes the edge data center, and the computing power network wins at the edge.

2.1 Broadband Gateway

The broadband gateway is upgraded through the separation of forwarding and control, which enables the slimming of the physical gateway on the user side, and all services are migrated to the cloud, realizing "one-hop to the cloud" for broadband access.

The BBF World Broadband Forum standardization organization and the IETF International Internet Engineering Task Force have both proposed user-side broadband gateway standards and deployment solutions based on the control-forwarding separation architecture. Different standardization organizations, the same system architecture and deployment solutions, the industry has reached a consensus on the control-forwarding separation architecture of user-side broadband gateways.

BRG (thin gateway) logically connects to vG (cloud gateway) through OverLay tunnel or 1:1 VLAN mapping, and the two work together to carry the user-side gateway function. The following changes are brought about by separating the control and forwarding of cloud gateways:

1. When providing L3~L7 value-added services, it reduces the complexity of gateway implementation and has a flexible upgrade and update mechanism, enabling cloud gateways through SFC service chain orchestration;

2. Significantly shorten the service delivery cycle and quickly deploy through cloud computing;

3. Integrated deployment of edge cloud, CDN, etc., one-hop access to the cloud, greatly improving user experience;

4. Reduce the user-side physical gateway cost to a certain extent.

The user-side physical gateway, based on an all-optical base, uses an OverLay tunnel to route traffic to the edge cloud gateway at high speed. The cloud gateway orchestrates and schedules services based on the service chain, carries out home broadband value-added services, and schedules traffic into the cloud and network based on users, services, and content.

2.2 OLT Network Element

OLT, Optical Line Terminal, is a terminal device used to connect to the optical fiber trunk line. Its function determines that OLT itself is a network element device that focuses on the forwarding plane, and is not the key to separation of forwarding and control. Its separation of forwarding and control is at most to shrink its network element management function to the cloud. When broadband gateways and BRAS are separated from forwarding and controlled and deployed in edge cloud, the role of OLT's separation of forwarding and control is not obvious, and it is even gradually combined with other network element forwarding planes. I will not elaborate on this here.

2.3 BRAS Network Element

BRAS is located at the edge of the metropolitan area network and is the entry point for users to realize various broadband services. It plays a pivotal role in the operator's network. At present, major domestic operators have completed the upgrade and transformation of vBRAS and have maturely put it into commercial use. China Mobile has already launched the vBRAS equipment specification standard.

vBRAS has taken the first step towards cloudification of metropolitan area networks and completed edge cloud deployment. In the future, it will drive more network elements to be carried on cloud resource pools, more services will be centrally configured and scheduled, and the network architecture will be more concise, open, and agile.

In traditional broadband networks, OLT carries the user access aggregation function. When BRAS realizes the separation of forwarding and control, BRAS-UP will be able to gradually sink to a lower position, or even be deployed at the OLT position, until it replaces the OLT equipment, greatly simplifying the network topology.

Part 03: Evolution of layered architecture centered on DC

When multiple network elements and multiple heterogeneous networks are separated in forwarding and control, the forwarding planes and control planes of the network element devices converge, providing conditions for building a DC-centric layered network architecture. At the same time, some heterogeneous network elements may disappear.

Let's take the BBF TR-459.2 vBRAS standard as an example. As a broadband infrastructure, vBRAS also completes the functions of 4G LTE mobile communication network related network elements. On the other hand, the evolution of 4G and 5G network elements of mobile communication networks, including SGW, PGW, UPF, etc., reversely penetrates the broadband access function. Finally, the fixed and mobile heterogeneous networks are completely integrated and normalized.

China Mobile has also proposed a DC-centric cloud network architecture. The telecom cloud resource pool is centered on DC and a unified hardware resource pool, including two layers of TIC (core TIC and edge TIC).

With the comprehensive separation of control and transmission of network element equipment and further integration of cloud and network, the following DC-centric operator terminal room layout will eventually be formed.

Domestic operators and foreign operators such as AT&T launched the R-CORD project in 2014. By adopting white box equipment, open source software, and virtualization technology (SDN/NFV, etc.), they transformed the traditional terminal equipment room (switching center) in the operator's broadband network into a data center similar to that of a cloud service provider, reconstructed the network architecture into a DC-centric layered network architecture, and successfully put it into commercial use.

Part 04: Evolution of computing and network integration

When the network is reconstructed into a DC-centric hierarchical network architecture, if cloud-network integration is inevitable, then computing-network integration is the cornerstone. Each network element exists in the form of a DC edge cloud, and each hierarchical DC is connected to form a network with an all-optical base. The computing power will flow freely between DCs like tap water, realizing "computing follows people, people move and computing moves", and "one point access, ready to use".

Part 05: Outlook

The computing network has been promoted to an extremely important position at the industry and national levels, including the national "East Data West Computing" strategy and the operator computing network transformation strategy, and has huge market potential and strategic value. Starting from the evolution of broadband infrastructure, this article discusses the development direction and strategy for computing networks from various levels, and will achieve the goal of "ubiquitous computing power, symbiosis of computing networks, intelligent orchestration, and integrated services" in the future.