In the 5G era, as the Internet of Everything faces diverse and multi-scenario demands, the 5G bearer network is entering a period of unprecedented opportunities and challenges. The transformation of bearer networks and technologies is no longer optional—it's essential. Let’s explore this topic with Network Communication Xiaobian.
For the 5G bearer network, it’s not just about high bandwidth anymore. Operators must also consider end-to-end service delivery, traffic isolation, low latency, and robust network protection. To meet these requirements, ZTE has introduced the Flexhaul solution—a next-generation end-to-end network architecture for 5G bearers. Based on SDN technology, Flexhaul spans from Layer 3 down to Layer 0, offering a comprehensive technical system. As shown in Figure 1, Flexhaul supports L2/L3VPN services at Layer 3, SR/MPLS at Layer 2, FlexE at Layer 1, and includes innovations and extensions to standard FlexE technology. It enables end-to-end FlexE Tunnel at Layer 1, providing switching, OAM, and protection. At Layer 0, DWDM technology ensures scalability and smooth evolution of the network.
Figure 1: ZTE’s 5G Flexhaul Bearer Architecture
Flexhaul supports a flat network architecture and uses FlexE technology to enable multi-wavelength and multi-link bandwidth aggregation. This allows flexible expansion of network capacity and significantly improves bandwidth scalability. To support ultra-low latency services like uRLLC, ZTE has innovated FlexE Tunnel technology, extending FlexE from interface-level to network-level. This enables network segmentation based on FlexE Tunnel, meeting the needs of low latency and high reliability. As shown in Figure 2, Flexhaul can divide network resources—bandwidth, delay processing functions, CPU, and VPN—into multiple virtual end-to-end networks. Each network slice is logically isolated on the forwarding and control planes, adapting to various service types and user needs. Additionally, protection switching based on FlexE tunnel technology can be achieved within 1ms, upgrading carrier-class protection to an industrial control level. For uRLLC services, FlexE Tunnel solves the issue of excessive granularity and low efficiency in wavelength punch-through solutions, while avoiding the large delays and lack of physical isolation in soft slicing.
Figure 2: Network Slice Based on FlexE Tunnel
Now, let’s dive into one of the key innovations of the 5G Flexhaul solution: FlexE Tunnel.
First, the origin of FlexE — decoupling of service rate and physical port.
In January 2011, the Optical Internetworking Forum (OIF) established a research group focused on Flexible Ethernet. By July 2015, they released a draft, and by March 2016, they finalized the FlexE 1.0 standard (OIF-FLEXE-01.0). They later began working on the 2.0 version. FlexE technology decouples the service rate from the physical channel rate, allowing customers to use different rates than the physical interface. For example, a customer service running at 400GE can use a 100GE physical channel. Instead of being limited to a single physical channel, services can be bundled across multiple channels to form a virtual logical channel. This flexibility allows for diverse service speeds and multiple physical channel rates. Large-bandwidth services can utilize standard 25GE/100GE interfaces, combined with port bundling and time-slot cross-connect technology, enabling a smooth evolution from 25G → 50G → 100G → 200G → 400G → xT, solving the cost inefficiency of high-speed physical channels.
Figure 3: FlexE Technology Achieves Flexible Speed
Second, FlexE Tunnel technology — expanding FlexE to the network level.
Initially, FlexE was designed for point-to-point applications, focusing on large-bandwidth transmission. However, current standards are limited in end-to-end network applications and service protection. ZTE has expanded FlexE beyond its original scope, introducing the revolutionary FlexE Tunnel technology. This technology creates an ultra-low latency, physically isolated, highly reliable end-to-end pipeline based on customer bandwidth needs, adaptable to dynamic customer requirements. FlexE time-slot switching, OAM expansion, and ultra-fast protection switching extend FlexE from a point-to-point interface technology to a full network solution. This provides critical technical support for 5G bearer networks. ZTE’s extended FlexE Tunnel solution offers operators several advantages:
**Device-Level Ultra-Low Latency Forwarding**
FlexE uses time-slot cross-connect to forward user service flows at the physical layer, without parsing packets in intermediate nodes. This real-time forwarding achieves a single-hop device delay of less than 0.5 μs, laying the foundation for low-latency services.
Figure 4: FlexE Switching for Ultra-Low Latency Forwarding
**L1 End-to-End OAM and Fast Protection**
FlexE Tunnel expands overhead to enable end-to-end error detection and performance monitoring. OAM information such as CC/CV, LM, DM, RDI, LB, LT, LCK, TST, APS, and more is used for end-to-end monitoring. It also provides protection to ensure service reliability. When a failure occurs in a tunnel, traffic is quickly switched to another tunnel. Protection methods include 1+1 and 1:1, with switching times under 1ms due to physical-layer implementation.
**Any Subrate Fragmentation, Physical Isolation, and End-to-End Hard Pipeline**
FlexE sub-pipeline features and physical-layer slot-crossing combine to create an end-to-end FlexE Tunnel that isolates services at the physical layer. Intermediate nodes do not need to parse service packets, ensuring strict physical isolation. For example, a service between NE1 and NE4 can establish an end-to-end FlexE Tunnel 1, with NE2/NE3 devices directly using physical-layer cross-forwarding to connect NE1 to NE4.
Figure 5: FlexE Tunnel with Physical Layer Isolation
Third, FlexE Tunnel Practice and Collaboration
At the 2017 World Mobile Congress in Shanghai, ZTE demonstrated FlexE Tunnel for the first time. The demo included service isolation, ultra-low latency forwarding, end-to-end OAM, and fast protection switching. A 3D Flexhaul pre-commercial device, ZXCTN 609, was connected to a test instrument (IXIA XM2) via 100GE links.
Figure 6: Shanghai Exhibition Demo Network Topology
This demonstration showcased ZTE’s FlexE technology, including end-to-end isolation, sub-1ms protection switching, and sub-0.5μs device delay. Based on verification data, ZTE believes FlexE has a natural advantage in implementing ultra-low latency and secure isolation, making it the best choice for 5G bearer forwarding.
In August 2017, ZTE and Telefonica completed the first phase of 5G bearer testing in Madrid, Spain, proving the excellent performance of FlexE Tunnel-based Flexhaul in CPRI/eCPRI unified bearing, ultra-low latency, and fast switching.
In September 2017, ZTE passed the first phase of China Mobile’s SPN prototype equipment test, meeting all technical specifications, especially achieving a single-node forwarding delay of less than 0.5μs.
As 5G wireless standards continue to evolve, ZTE actively participates in standardization efforts, contributing proposals to ITU-T and promoting 5G bearer standards. One of its key contributions, the "FlexE Layer Network Model," is the first industry proposal for a layered network model based on FlexE, extending FlexE from link-only to network-level technology.
ZTE is the first in the industry to offer a complete 5G end-to-end product solution, continuously advancing 5G bearer implementations globally. With partners in China, Spain, France, Italy, Japan, South Korea, Singapore, Australia, and more, ZTE is leading the way in 5G development.
The journey of 5G is one of constant innovation. As a leader in the 5G era, ZTE will keep pushing the boundaries of 5G-hosted technologies, solutions, and equipment to provide operators with competitive and cost-effective options. With 5G construction, ZTE is ready to seize new opportunities in the 5G era!
This concludes our exploration of the 5G transformation of network communication—specifically, the FlexE Tunnel. For more detailed and updated information, visit eeworld, where we provide comprehensive content on electronic engineering.
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