## 4 Results and Analysis
### Comparative Testing of Transmission Mechanisms and Results Analysis
#### 4.2.7 Special Features of the Status Byte in Memory Block Management  
The status-byte-assisted RDMA transmission mechanism adds a status byte to each memory block, enabling operations on individual memory blocks. In contrast, the sliding window RDMA transmission mechanism requires sequential processing of memory blocks. In practical applications, the receiver might need to retain data within a memory block. The two transmission mechanisms handle this differently. To simulate this scenario, it is assumed that the receiver retains the data from the third memory block at the 100-ms mark and resumes processing at the 200-ms mark.  
Figure 18 shows the throughput changes in the sliding window RDMA transmission mechanism and the status-byte-assisted RDMA transmission mechanism in response to specific demands. As depicted in Figure 18, the status-byte-assisted RDMA transmission mechanism experiences only a 12% decrease in throughput after the 100-ms mark and recovers at the 200-ms mark. In contrast, the sliding window RDMA transmission mechanism stops sending data at the 100-ms mark, resulting in zero throughput until the memory block is released at the 200-ms mark, after which the throughput recovers.  
Figure 17: Comparison of the minimum RNIC resource consumption at the receiving end for different RDMA transmission mechanisms.  
Figure 18: Throughput change in various RDMA transmission mechanisms in response to special demands.  
The reason for this difference lies in the status-byte-assisted RDMA transmission mechanism's ability to set the status byte of a retained memory block to \"unavailable\" while continuing to process the next memory block. In this scenario, the sending thread skips over the retained memory block and continues processing until the device returns to normal. With only two memory blocks used for data transmission, the throughput only slightly decreases. Therefore, this flexible memory block handling capability of the status-byte-assisted RDMA transmission mechanism enhances the system's ability to manage various unexpected situations. In contrast, in the sliding window RDMA transmission mechanism, memory block sending and receiving must occur sequentially. Consequently, a subsequent memory block cannot be sent before the preceding one, and the ACK for a subsequent memory block cannot be sent before the preceding memory block's ACK. As a result, its throughput drops to zero.  
One of the key advantages of the status-byte-assisted RDMA transmission mechanism in practical applications is its ability to maintain transmission continuity effectively. When network conditions change or delays occur, this mechanism dynamically adjusts the allocation of memory blocks, ensuring that the data transmission process is not interrupted. This continuity is particularly crucial in critical applications such as real-time video streaming and autonomous systems, where any pause or interruption could lead to serious consequences. By quickly adapting to changing transmission conditions, this mechanism significantly reduces the risk of system downtime, ensuring efficient and stable operation.  
Although the status-byte-assisted RDMA transmission mechanism provides significant flexibility in memory block management, this flexibility also comes with some potential drawbacks. Specifically, this mechanism requires status byte checks during data transmission to flexibly manage the memory blocks. The status-byte-assisted mechanism does not need to check the memory block status when the memory block is available. However, it needs to perform an additional check to find an available memory block when a particular memory block is unavailable, which could increase additional CPU resource usage. Moreover, the CPU resource consumption of the status-byte-assisted transmission mechanism remains lower than that of the sliding window transmission mechanism as the data transmission of the status-byte-assisted RDMA transmission mechanism is handled by a single thread.