Network re-architecting presents telecom operators both challenges and opportunities. To figure out a proper way to make traditional networks step forward to SDN/NFV-based networks, operators have to tackle the essential problem by re-architecting their Central Offices (COs). A number of hot topics such as how to rebuild the equipment rooms, how to restructure the devices and how to deploy services are now intensively discussed in the industry.
Currently, overseas mainstream operators and organizations, for instance the AT&T in America, as well as Orange and Deutsche Telekom (DT) in Europe, show great passion for CO re-architecting.
At the same time, the operators in China also start their CO re-architecting on local networks so as to set up edge data centers (EDCs). When compared with Internet companies, the telecom operators with massive EDCs locating close to users show predominant advantages. It has been proved that CO re-architecting on the existing local network is critical to the EDC establishment. So far, the operators have made plenty of achievements, for example, the CTNet2025 Technical White Paper released by China Telecom defines the future network architecture and points out the evolution direction of the China Telecom CO re-architecting; the TIC next-generation network plan released by China Mobile defines the roadmap Of China Mobile’s future network planning and clearly shows the general objective of CO (edge TIC) re-architecting; the CUBE strategy issued by China Unicom highlights the future network architecture and evolution path vividly. A lot many tests and pilots related to the CO re-architecting have been carried out in China.
ZTE CO Re-Architecting Solution
Aiming at carrying all sorts of virtual network functions (VNFs), ZTE CO re-architecting solution urges service innovation and fast service provisioning. By proving on-demand networks including both on-demand network connections and services, satisfying the user’s demands for customized and differentiated services and making the services close to the user, it greatly enhances the user experience.
The ZTE CO re-architecting Solution is as shown in the figure 1:
- Cloud access network: Services are distributed to the data centers on the basis of dynamic policies; Support the EDC backup and load sharing.
- EDC/DDC: Build VxLAN-based cloud data center network architecture on the basis of spine-leaf data center switching; Build a unified basic cloud platform in the DC to form vDC-based cloud infrastructure; Support NFV-based unified service orchestration and deployment, as well as all sorts of services and service chains.
- Data center interconnect (DCI) between EDCs/DDCs: Carry east-west traffic between the data centers; support north-south traffic of new services, for example, the north-south traffic of the CDN and green internet services.
- Operation and management based on SDN and cloud: A unified orchestration and management system allows unified deployment and management of SDN-based infrastructure and NFV-based VNFs.
Figure 1 ZTE CO Re-Architecting Solution
Essential Factors of the CO Re-Architecting Solution
Major Factors for selecting equipment rooms
Traditionally, the power density per rack is around 2KW-4KW. The IT rack of the data center available for 20-30 servers lifts the power density up to 10KW-20KW, which accordingly generates tougher requirements for the power and air conditions of the CO equipment room. Besides, as the number of the users covered by one CO equipment room increases by several or even dozens of times, one single equipment room shall be reserved with enough space for more COTS servers and other network devices. Selecting the most proper EDC has never been an easy thing, thus people should take a lot of factors such as the power, air conditioning, area, load bearing and fiber resources into consideration, so as to select the most suitable CO equipment room for the re-architecting. It is proposed that the DC re-architecting can be started with the idle equipment rooms appeared when the public switched telephone network (PSTN) is out of service.
Central Office Re-Architecting
The CO re-architecting is to covert the traditional equipment room to the DC, so that cloudified DC network infrastructure can be provided. As shown in the figure 2, the key points of the CO re-architecting include:
- Build a VxLAN-based multi-tier DC cloud network. The multi-tier DC includes the central DC, regional DC, edge DC and remote modules. The cloudified DC network turned from the multi-tier DC is under unified management and scheduling. s
- A cloud management platform is deployed to enable unified management of the DC resources. Interoperation of three parties’ data centers implemented by the cloud management platform enables virtual cloud resource pool. The SDN controller is deployed to enable interconnection of all the connections and services of the entire vDC network. Build a public resource pool to improve the device utilization and reliability. The public resource pool includes an IT cloud resource pool, CT cloud resource pool and public network forwarding resource pool. The innovative Tunnel Terminate Gateway (TTGW) proposed by ZTE provides large traffic, high QoS and high performance for the vBRAS, gives support for future flexible service classification and complies with the demands for integrated mobile and fixed network services. AvBRAS X86 public forwarding resource pool is built to match the demands of the services with small traffic and high sessions. The two resource pools serving each other as important supplement satisfy the demands of different services.
Figure 2 Central Office Re-Architecting
Service deployment inside the CO
Virtualized services are deployed in the CO hierarchically as per different factors, for example, the bandwidth demand, latency demand and coverage. The services requiring high bandwidth and low latency are deployed on the EDC; while, the services with moderate demands for traffic and latency are deployed on the regional and central DCs.
- Deployment of the vBRAS service
The vBRAS with control plane and user plane (C/U) separated architecture unveiled by ZTE decouples the service control and service forwarding successfully. The two vBRAS models released by ZTE support different application scenarios with different traffic/session density. The NFV-based control plane enables virtualization, automatic deployment and elastic scaling. The high-performance user plane allows the big-traffic and high-performance service forwarding. The universal X86 forwarding plane enables flexible multiservice deployment.
In the CO re-architecting solution, the dual resource pools on the vBRAS user plane is deployed in the following way: The high-performance forwarding resource pool evolves to the TTGW to serve multiple services as a public performance forwarding resource pool. As a result, the services asking for high bandwidth, low latency and high QoS can be well satisfied. The X86-based forwarding resource pool deployed as a supplement of the high-performance forwarding resource pool is to meet the requirements of the services known for high concurrency, small traffic and low QoS demands. The two resource pools work together with each other perfectly to satisfy the future elastic and high-performance services.
- Deployment of the Elastic SD-WAN service
ZTE’s Elastic SD-WAN cloud and network integrated solution employs coupled network and cloud to enable automated deployment and O&M of enterprise private lines. The vCPE-related VNF is deployed in the CO to support elastic service scaling and automatic service deployment. So that, on-demand networks and services can be supported. ZTE’s virtual multi-service routers (vMSRs) provide vCGN, vFW and vLNS services on the basis of service chains to enable flexible service customization. Moreover, the vMSR can either be shared by small enterprise VPNs or implemented independently by large private lines of big customers. ZTE Elastic VPN service enables the interoperation between different enterprise VPN sites and makes the enterprise users capable of accessing both public and private cloud resources in the cloud resource pool.
- Deployment of the vCDN service
The increasing big video services raise stricter requirements for network bandwidth, latency and packet loss rate. Also the related video services need to be shifted down. Therefore, the vCDN may contain more hierarchies and be deployed in a lower position. In the CO re-architecting solution, the vCDN shall support hierarchical and multi-tier deployment as per specific demands. The services with high hit ratio are deployed on the EDC or the remote modules. While, the services with low hit ratio shall be deployed on the regional or central DC.
- Deployment of the vEPC service
Being an active member in the virtualization of the network infrastructure, the vEPC in order to support high bandwidth, low latency and high concurrency in the 5G/5G+ Era employs C/U separated architecture to allow the data plane and control plane deployed in different DCs. Terminate the data plane at the EDC (CO equipment room) to comply with the high-bandwidth and low-latency requirements. Deploy the control plane on the regional or central DC to satisfy the demands for big concurrency and wide coverage.
Other services such as Internet of Things (IoT) can also be deployed hierarchically as per their own features.
- Fixed Mobile Convergence Deployment Solution
Regarding to the network that hasn’t been re-architected, the vEPC is not shifted down to the EDC. A co-site mobile edge computing (MEC) service processing server deployed at the BBU side serves for a remote node of the EDC. The service is managed uniformly together with the fixed services. Configure service diversion policies on the switching unit of the BBU to redirect some special services to the MEC server. Then the MEC server resolves the GTP-U tunnel, processes services and finishes necessary accounting services. For example, when a large-scale live broadcasting service is implemented, the EDC will send the services to the MEC server first, and let the MEC broadcast the media streams to the wireless network. This method saves a lot of Backhaul bandwidth. With the brand-new 5G network architecture, some vEPC user planes will be shifted down to the EDC by the MANO according to the specific service planning and demands. When the MEC services are deployed to the vEPC, the vEPC identifies the service streams to be processed on the EDC, and sends them to the MEC service system via service chaining or routing. In this way, the fixed network and mobile network services can be carried on the EDC uniformly.
ZTE CO re-architecting solution, putting Broadband China Strategy into practice, serves global operators’future network architecture and provides powerful support for their network transformation.
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