Emulating a space-based router

In a satellite network, a centralized payload router peers with hundreds, to potentially thousands of terminals that serve as gateways for highly mobile user networks. These terminals and user networks generate significant amounts of control plane traffic when exchanging routing information that must be processed by the payload. Many factors influence this control traffic load, including neighbor count, route table size, routing policies, and user network mobility. Although these elements may seem manageable individually, their collective effect can significantly impact the router's performance. Routing protocols currently used by the Internet were not designed for satellite networks, and the consequences of using them in these environments have not been studied in depth. The mobility patterns and link intermittence characteristics of a satellite-based network not only make well known network problems such as ?black holing traffic? and ?route flapping? worse, but also create a whole new set of issues, such as mobile route churn. In order to study some of these issues, we have developed a space networking testbed (SNTB) to stress a representative payload router with realistic events and conditions. SNTB is an experimental local-area network (LAN) consisting of PC nodes, commercial off-the-shelf (COTS) routers, and traffic generators/analyzers that are automatically configured by a Web-based software tool, Emulab. Using real instances of current Internet routing protocols to generate representative control-plane traffic, emulation studies were conducted for space-based networks with both static and dynamic connectivity to measure the CPU load, memory utilization, and bandwidth usage at the payload router. Three representative payload routers (software-based, Cisco 7604, and Juniper M7i) were tested, and results show that payload router performance is a function of the ground network it is peering with (i.e., neighbor count, route table size, number of routing advertisements, and mobility), as well as the CPU, memory limitations, and operating system of the router itself.