With the widespread adoption of Gigabit Ethernet interfaces, many users prioritize Gigabit ports when selecting servers. However, many people misunderstand the actual upload and download speeds of Gigabit Ethernet, even misinterpreting "Gigabit" to mean a data transfer capacity of 1GB per second, leading to unrealistic bandwidth expectations. So, what are the actual upload and download speeds of Gigabit Ethernet servers? This isn't just a theoretical question; it also involves multiple technical factors, including network architecture, protocol overhead, and hardware support.

　　First, we must clarify that "Gigabit Ethernet" refers to a network interface standard of 1GbE, or 1000 megabits per second. Note that the unit is "bits," not "bytes." Under ideal conditions, a Gigabit Ethernet server can achieve up to 125MB/s in both upload and download speeds. However, this is only possible under purely theoretical conditions, with zero latency, zero interference, and zero protocol loss. Real networks are far from meeting these ideal conditions.

　　In actual deployment and use, the transmission speed of a Gigabit Ethernet server is often affected by the following factors:

　　1. Protocol overhead. During network transmission, some bandwidth is consumed by encapsulation protocols (such as TCP/IP and Ethernet frame headers). This loss typically ranges from 5% to 10%. Taking 125 MB/s as a baseline, the available speed after deducting protocol overhead is approximately 110 to 118 MB/s.

　　2. Server disk performance bottleneck. Servers equipped with traditional mechanical hard disk drives (HDDs) are far inferior to SSDs in read and write performance, often struggling to achieve sustained read speeds exceeding 100 MB/s. This results in a situation where "the network speed is fast enough, but the hard disk can't keep up." NVMe SSDs, combined with high-performance processors and optimized I/O scheduling strategies, can truly maximize the value of gigabit network bandwidth.

　　3. CPU usage and interrupt handling. High-speed network transmission requires processing a large number of interrupt requests. Insufficient CPU performance or weak system interrupt handling capabilities can also significantly limit transmission speeds. Modern servers generally use multi-queue network cards with interrupt binding optimization to alleviate this problem.

　　4. TCP window and congestion control algorithms. In Linux or Windows systems, the TCP window size and congestion control algorithm directly affect data transmission efficiency. The default configuration is often unsuitable for long-distance, high-bandwidth communications, requiring manual parameter adjustments to improve long-distance transmission rates.

　　5. Client device or network link limitations. If the peer device only supports 100Mbps or its access line (such as home fiber) is insufficient, uploads and downloads may not reach the full Gigabit speed. For example, a VPS in the US may have a Gigabit network card with a bandwidth listed as 1Gbps, but if the user's local access speed is only 100Mbps, the Gigabit speed will not be perceived.

　　How to improve the actual bandwidth utilization of Gigabit Ethernet?

　　To maximize the performance of a Gigabit Ethernet server, you need more than just hardware configuration; optimization at the system and network levels is also required. Here are some practical strategies:

　　Enabling multithreaded transfers and using tools such as aria2c and rsync -z --partial --inplace that support multithreaded concurrent transfers can overcome single-threaded bandwidth bottlenecks.

　　Enabling TCP acceleration algorithms and using modern TCP algorithms such as BBR and CUBIC in Linux can optimize long-distance transmission efficiency in environments with packet loss.

　　Optimizing network card driver parameters by modifying the MTU (typically set to 1500 or 9000), enabling interrupt coalescing, and binding CPU cores can reduce system resource usage.

　　Using efficient protocol tools such as Rclone, Syncthing, and Globus to transfer data offers superior stability and throughput over traditional FTP.

　　Choose a nearby mirror node and CDN acceleration. For services such as public network downloads, software updates, and image service deployment, you can combine CDN services or a multi-node active-active distribution strategy to reduce network hops.

　　Although "Gigabit Ethernet servers" sound impressive, their actual upload/download speeds are around 110 MB/s, assuming ideal network links, protocol loss, and hardware conditions. Often, insufficient bandwidth isn't a server issue, but rather a combination of factors, such as the network path, client, and concurrent connections. Understanding the gap between theoretical bandwidth and actual available bandwidth helps you set reasonable expectations and make system-level optimizations and configurations based on application needs. Only when the network, CPU, disk, and system stack fully collaborate can the true performance of Gigabit Ethernet be unleashed.