# Lossless and High-Throughput Congestion Control in Satellite-Based Cloud Platforms +
###### Abstract
Specifically, NDN's request aggregation, content multicast [12], and in-network storage mechanisms facilitate the distribution and collaborative storage of data chunks. These features ensure that satellite-based cloud platforms can meet the requirements for efficient content distribution, low-delay data acquisition, and reliable transmission. Consequently, the satellite-based cloud platform based on the NDN architecture demonstrates substantial development potential [13]. As the demand for cloud storage and cloud computing services continues to grow, LEO satellite networks face the challenge of handling a vast amount of information exchange, which poses significant challenges for congestion control. Reducing packet loss, improving throughput, and avoiding congestion have become urgent issues that need to be addressed. NDN relies on the pull model to acquire content, where the user sends explicit requests referred to as \"Interest\" to pull the named content referred to as \"Data\". Each request message contains the name of the desired content and is forwarded by routers according to the name to retrieve the corresponding content from sources or in-network caches [14]. Each Interest will retrieve one Data, and the Data are reverse-forwarded along the path specified by the Interest. After receiving the Data, the router stores its copy in the Content Store (CS) and immediately forwards the Data. This means that the Data will be inserted into the output queue of the forwarding interface, as shown in Figure 1.  
However, when the traffic of Data packets waiting to be forwarded exceeds the link capacity, these Data packets accumulate in the output queue, leading to queue overflow and packet loss. This issue is prominent in LEO satellite networks due to their dynamic available bandwidth. In this paper, the term \"bandwidth\" is employed to denote the maximum data transmission rate of a link, reflecting the link capacity for data transfer. The substantial space propagation delay and queuing delay result in a significant increase in data acquisition delay, especially during retransmission triggered by packet loss. Therefore, designing an effective congestion control scheme in NDN to achieve low transmission delay, high throughput, and lossless forwarding is of great significance. Currently, most NDN congestion control schemes employ a receiver-driven approach, whereby the traffic of Data packets can be indirectly regulated by adjusting the sending or forwarding rate of Interests. According to the participants involved in congestion control, existing methods in NDN can be classified into three categories: (1) consumer-side congestion control, (2) hop-by-hop congestion control, and (3) hybrid congestion control [15]. Regarding the first method, it requires consumers to monitor the RTT from sending an Interest to receiving Data and then estimate whether the network is congested based on changes in RTT. This information is used to adjust the sending rate of Interests, thereby controlling the response rate of Data packets. However, due to multiple sources and forwarding paths in NDN, content is no longer transmitted along a single path, resulting in significant fluctuations in RTT. Consequently, adjusting the sending rate of Interests becomes challenging for accurately preventing congestion. The second method, hop-by-hop congestion control, requires each router to monitor the occupancy of output queues at each interface. Once congestion is detected, the router sends signals downstream. Upon receiving these signals, downstream routers reduce the forwarding rate of Interests and continue to propagate the signals further downstream [16; 17]. Ultimately, this forces a decrease in the sending rate of Interests. However, this approach can easily lead to packet loss because received Interests may not be forwarded in a timely manner. The hybrid congestion control method requires collaboration between consumers and routers. Currently, the Practical Congestion Control Scheme (PCON) [18] is the most recognized mechanism in NDN.