# Lossless and High-Throughput Congestion Control in Satellite-Based Cloud Platforms +
## 3 Integrated System and Algorithm Design
### Framework of CCLF  
The CCLF modifies the details of the data forwarding process in NDN. Specifically, we enhance the backhaul forwarding of Data packets. Incoming Data packets are first stored in the CS. Following this, a priority-based scheduling algorithm is employed to progressively forward both time-sensitive and regular Data packets.  
The current NDN architecture allows the CS to store Data packets, which are then forwarded immediately. However, when the output queue of the forwarding interface is full, Data packets are discarded. In contrast, the CCLF method enhances the functionality of the CS by enabling it to serve both as a storage and a forwarding buffer. This allows Data packets to be temporarily held in the CS when the output queue of the forwarding interface is full, ensuring lossless forwarding by retaining packets until the queue has available capacity. This critical capability is absent in traditional NDN systems.  
Advancements in hardware technology have enabled high-capacity DRAM in cloud servers. For instance, the M2 UltraMemory [24] machine types are specifically designed for memory-intensive workloads. Each M2 UltraMemory VM provides up to 5888 GB of memory. Consequently, it is feasible to equip LEO satellite routers with 5 TB or greater DRAM, thereby facilitating efficient data storage and access in the CS.  
The main improvement introduced by the CCLF is the creation of a dispatch table within NDN routers to assist in making forwarding decisions. This dispatch table maintains detailed records for each Data packet stored in the CS that has not yet been forwarded. When the final Data packet in the output queue is transmitted, the dispatch table is consulted, and the next Data packet to be forwarded is selected based on a priority-based scheduling algorithm. This selected Data packet is inserted into the output queue and immediately forwarded, and the next Data packet is then selected, as illustrated in Figure 3. By scheduling Data forwarding based on the current status of the output queue and the priorities of data flows, the CCLF method achieves maximum throughput while ensuring congestion-free forwarding and reducing the flow completion time.  
In LEO satellite communications, the available bandwidth frequently fluctuates due to varying conditions. By leveraging the contact windows provided by satellite communication, we can model the time-varying network as a sequence of segmented static networks. Specifically, when the available bandwidth of the upstream link exceeds that of the downstream link, CCLF leverages the CS to store Data packets that cannot be immediately  
Figure 3: Data forwarding process in CCLF with dispatch table.  
forwarded due to bandwidth limitations. Once the available bandwidth of the downstream link increases, these previously stored Data packets can be promptly forwarded, thereby enhancing the overall throughput of the network. This mechanism ensures efficient use of available bandwidth and minimizes delays, as illustrated in Figure 4.  
We establish models to validate throughput optimization and QoS guarantees in CCLF. First, we calculate and compare the end-to-end average bandwidth, which serves as an indicator of throughput. Then, we introduce a priority-based Data scheduling model.