Layer 4 load balancing operates at the transport layer (OSI Layer 4), using TCP/UDP protocols to

distribute traffic based on information like IP addresses and port numbers, without inspecting the

application-layer content (Layer 7). Let’s evaluate each option:

A. Nginx: Nginx is a versatile web server and reverse proxy that supports both Layer 4 and Layer 7

load balancing. In its Layer 4 mode (e.g., with the stream module), it balances TCP/UDP traffic,

making it a Layer 4 load balancing technology. This is widely used in Huawei’s CloudFabric DCN

solutions for traffic distribution. TRUE.

B. PPP (Point-to-Point Protocol): PPP is a Layer 2 protocol used for establishing direct connections

between two nodes, typically in WAN scenarios (e.g., dial-up or VPNs). It does not perform load

balancing at Layer 4 or any layer, as it’s a point-to-point encapsulation protocol. FALSE.

C. LVS (Linux Virtual Server): LVS is a high-performance, open-source load balancing solution

integrated into the Linux kernel. It operates at Layer 4, using techniques like NAT, IP tunneling, or

direct routing to distribute TCP/UDP traffic across backend servers. It’s a core Layer 4 technology in

enterprise DCNs. TRUE.

D. HAProxy: HAProxy is a high-availability load balancer that supports both Layer 4 (TCP mode) and

Layer 7 (HTTP mode). In TCP mode, it balances traffic based on Layer 4 attributes, making it a Layer 4

load balancing technology. It’s commonly deployed in Huawei DCN environments. TRUE.

Thus, A (Nginx), C (LVS), and D (HAProxy) are Layer 4 load balancing technologies. PPP is not.

Reference: Huawei CloudFabric Data Center Network Solution – Load Balancing Section; HCIP-Data

Center Network Training – Network Traffic Management.