Satellite communications present challenging characteristics. Continuous end-to-end connectivity may not be available due to the large distances between satellites. Moreover, resources such as link capacity and buffer memory may be limited. Routing in satellite networks is therefore both complex and crucial to avoid packet losses and long delays. The Delay Tolerant Network (DTN) paradigm has emerged as an efficient solution for managing these challenging networks. Contact Graph Routing (CGR), a deterministic routing algorithm, is one of the most popular DTN algorithms. CGR is compatible with the store, carry, and forward principle, whereby a node receives a message and stores it in its buffer until a transmission opportunity becomes available. However, CGR relies on simplified models to incorporate potential constraints in the route search. For instance, the linear volume assumption is often used to consider capacity constraints. Moreover, capacity management and buffer management are mostly performed during the forwarding phase, once an issue has occurred. These reactive management techniques cause many collisions and increase the average delivery time. In this paper, we propose taking measures before or during the route search in order to find routes that respect both contact-capacity and node-buffer limits. We introduce the contact splitting and edge pruning operations to effectively account for the routing constraints. This ensures that CGR outputs the optimal solution in terms of delivery time among the subset of valid solutions. The problem is formalized as the Feasible Earliest-Arrival Path with Capacity and Buffer constraints (FEAP-CB) and optimality is proved. The proposed approach can also be used to book resources to be used in case of issues during the forwarding phase.

翻译：卫星通信呈现出具有挑战性的特性。由于卫星间距离遥远，持续的端到端连接可能无法实现。此外，链路容量和缓冲区内存等资源可能有限。因此，卫星网络中的路由既复杂又至关重要，以避免数据包丢失和长延迟。容迟网络（DTN）范式已成为管理这些挑战性网络的有效解决方案。接触图路由（CGR）作为一种确定性路由算法，是最流行的DTN算法之一。CGR兼容存储、携带和转发原则，即节点接收消息并将其存储在缓冲区中，直到出现传输机会。然而，CGR依赖于简化模型来纳入路由搜索中的潜在约束。例如，常使用线性体积假设来考虑容量约束。此外，容量管理和缓冲区管理大多在转发阶段、问题发生后执行。这些反应式管理技术会导致许多冲突并增加平均交付时间。在本文中，我们建议在路由搜索之前或期间采取措施，以找到同时遵守接触容量和节点缓冲区限制的路由。我们引入了接触分割和边剪枝操作，以有效考虑路由约束。这确保了CGR在有效解子集中输出交付时间最优的解。该问题被形式化为具有容量与缓冲区约束的可行最早到达路径（FEAP-CB）问题，并证明了最优性。所提出的方法还可用于预留资源，以便在转发阶段出现问题时使用。