# Towards Deterministic-Delay Data Delivery Using Multi-Criteria Routing over Satellite Networks
## 3 Problem Modeling
### Routing Algorithm
The SRv6 SID (Segment Identifier) packet format typically consists of three parts: Locator, Function, and Arguments [33]. The Locator is used to identify different satellite nodes in the satellite Internet. The Function field includes a specific identifier that distinguishes time-sensitive traffic from other types of traffic. This identifier is used in path generation and path selection to differentiate time-sensitive traffic from other services, creating a dedicated path that meets low-latency requirements. Different SID combinations form Segment Lists, which provide independent path information for time-sensitive and non-time-sensitive traffic and are stored in the Segment Routing Header (SRH) of each packet. By predefining SID sequences for time-sensitive traffic during the path planning phase and specifying the transmission path in the IPv6 header, precise control over the data transmission path can be achieved. The traffic is forwarded sequentially according to the SID list during transmission, bypassing route lookups at intermediate nodes and significantly reducing end-to-end latency for time-sensitive traffic. (2) Service Priority Configuration Based on Traffic Type: SRv6 supports service priority control based on traffic type. By setting a high-priority identifier in the Traffic Class field of the IPv6 header for time-sensitive packets, and leveraging SRv6's priority forwarding capability, this type of traffic can receive preferential treatment at network nodes, ensuring low-latency and reliable transmission. (3) Network Slicing and Traffic Isolation Strategy: The network slicing functionality in SRv6 enables independent path resources to be allocated to different types of data flows, each meeting its specific QoS requirements. By assigning different slice identifiers in the SID sequence for time-sensitive and non-time-sensitive services, independent transmission paths can be created for each service. This effectively prevents resource competition between TS and non-TS traffic, ensuring that time-sensitive data maintain a stable transmission path even under network load fluctuations. Specifically, network slicing isolatesthe transmission path of time-sensitive traffic from other flows, ensuring it maintains the shortest path transmission even under congestion conditions. (4) Dynamic Path Selection Mechanism: To further optimize the transmission quality of time-sensitive services, a satellite internet traffic scheduling algorithm based on the spatiotemporal distribution of traffic can be incorporated into the SRv6 protocol. This algorithm enables real-time awareness of load conditions across different paths and dynamically selects the optimal path for data forwarding based on the network load, thereby achieving load balancing and efficient resource utilization. (5) Time-Based VPN Update Strategy: In the satellite Internet, due to the limited network resources and unstable network connections, VPN updates should be scheduled to minimize any negative impact on network performance and user experience. Different regions can establish update schedules based on network load and traffic usage patterns. Typically, updates are triggered during off-peak periods to avoid affecting network performance. For example, updates can be scheduled during times when user activity is low or the network load is light, such as at night or in the early morning. ## 5 Algorithm Simulation and Results Analysis

To evaluate the performance of the routing algorithm, network simulations were conducted using MATLAB R2024a, based on a constellation _Walk_ker72/6/3\(\pi\) configuration. The algorithm's performance was compared with the shortest path algorithm and the optimized method in terms of load balancing effectiveness, packet loss rate for time-sensitive services, and throughput of time-sensitive services under different total daily traffic volumes. Additionally, the algorithm's runtime was simulated under varying numbers of tasks.