5G services not only have high requirements on network bandwidth, latency, reliability, and security, but also present a huge challenge to transport networks. ZTE has innovatively proposed 5G Flexhaul solution that can provide flexible and super-large capacity transport of fronthaul and backhaul services and achieve ultra-low latency and SDN-based dynamic traffic engineering.
In 2015, several equipment vendors, operators, and internet content providers jointly proposed flexible Ethernet (FlexE) interfaces, aiming to utilize existing 100G PHY resources to meet the needs of transporting large-granularity and some small-granularity services. FlexE has the characteristics of large bandwidth and port isolation. However, only as an interface technology at that time, FlexE failed to meet the 5G needs of low latency and E2E isolation.
Based on FlexE, ZTE has creatively developed three key techniques: FlexE switch, OAM, and protection (Fig. 1). FlexE is thereby extended from a point-to-point interface technology to an E2E networking technology. The FlexE tunnel solution, featuring E2E, ultra-low latency, and hardware isolation, is formed, providing vital technical support for 5G transport. This innovation is an important advancement of the 5G Flexhaul solution.
During the MWC Shanghai 2017, ZTE conducted a field test of key FlexE tunnel technologies. In the test, three 5G Flexhaul pre-commercial ZXCTN 609 devices are connected to the test instrument (data tester IXIA XM2) through 100GE links. ZTE demonstrated service isolation, ultra-low latency for traffic forwarding, E2E OAM, and rapid protection switching.
ZXCTN 609, based on packet switch and FlexE innovative technologies, supports integrated fronthaul, midhaul, backhaul transport scenarios, meeting the application need for unified 3G, 4G, and 5G networking. By providing wide bandwidth networking capabilities (100GE, 50GE, and 25GE) and supporting innovative E2E FlexE tunnel, ZXCTN 609 can also realize reliable service isolation, ultra-low latency for traffic forwarding, E2E OAM, and rapid protection switching.
● FlexE hard pipe isolation: In the 100G link, three high-speed bandwidth slices at rates of 5 Gbps are established by using the FlexE technology. Test traffic is injected into the three slices. When the test traffic in the first slice is over 5 Gbps, packet loss occurs. However, the other two slices still work normally. Traffic forwarding between different slices is strictly isolated without affecting each other.
● Industrial-grade rapid protection switching: In the FlexE tunnel solution, a complete OAM system including Flex Group OAM and FlexE Tunnel OAM is defined. Fault management, channel detection, latency measurement, and management channel are also included. Three devices are used to set up working paths and protection paths. The OAM fault detection mechanism at the FlexE level is enabled on the active and standby paths. Through fiber pulling, it can be observed that switching between the active and standby paths takes only milliseconds. Protection switching based on FlexE tunnel can be completed within 1 ms. This upgrades the protection switching from telecom-grade to industrial-grade.
● Ultra-low latency: Based on time slice, FlexE switch uses data block with 66 bits for data switching and forwarding on the shim layer, which is similar to cars passing through the viaduct. One and two P nodes are respectively inserted between two PE devices, and a test instrument is used to test E2E traffic latency in the two networking scenarios respectively. The test results show that the latency of a single P node can be as short as 500 ns and the jitter as short as 0.1 μs (Table 1). The latency and jitter of FlexE switch have no obvious changes as the load for single P node increases. FlexE switch can fully meet the ultra-low latency need of uRLLC traffic in the 5G era.
In the test, traffic forwarding between different network slices are strictly isolated without affecting each other. E2E connectivity detection and latency measurement are provided. The test results show that fault switching time is shorter than 1 ms, and the lowest latency of a single node for traffic forwarding is shorter than 0.5 μs. The test proves that ZTE’s 5G transport devices, with the traffic isolation and ultra-low latency features of FlexE tunnel, can fully meet differentiated transport requirements of various 5G services. Moreover, its efficient protection solution can lay a solid foundation for 5G network security in the future.
ZTE has completely carried forward the trials of 5G transport solution. The company has cooperated with several operators to explore the 5G transport field and has actively promoted the development of related standards. As a leader in the 5G era, ZTE will continue to make innovations in terms of device function, traffic forwarding, and network slicing, aiming to offer more competitive solutions for operators.
5G Flexhaul, FlexE tunnel, verification, Packet switch, FlexE switch, protection switching, latency