ITR: Collaborative Research: Resource Allocation and Denial of Service Prevention in Active Networks

互联网被一组快速扩展和变化的应用程序所使用。网络发展甚至提供特定于应用的处理的需求是显著的。然而，目前的网络基础设施很难发展，并不容易支持可定制性。主动网络的目标[21，3，2]是通过使网络基础设施可编程来促进这种演进和定制。增加可编程性的一种方法是允许将代码下载到路由器中，从而允许添加或修改服务。一种更激进的方法是允许数据包本身携带程序，以便在网络的路由器上选择性地执行。在其他问题中，这两种方法增加了拒绝服务攻击的可能性，由此用户对网络资源提出过度要求，以便拒绝另一用户的访问。然而，他们也使新的方法来处理这样的攻击，并解决一般的问题，在网络内的资源分配。建议的研究重点是涉及可编程的，或主动，数据包的问题。主动数据包以几种方式促进拒绝服务攻击。首先，与传统的数据传输分组不同，活动分组可能需要路由器处的处理器周期和存储器，而不仅仅是简单地转发分组所需的处理器周期和存储器。第二，通常，在路由器处执行活动分组可能导致从路由器发送多于一个活动分组。这种行为是有用的，因为它允许数据包在网络上散开，但它可能是危险的，因为它可能导致单个初始数据包使用的资源呈指数增长。基于主动分组的系统的经验[9，8，23，22，24]表明，拒绝服务是在这种系统可行之前必须克服的最大障碍。首先，研究人员建议设计包编程语言，使某些类型的行为本质上是不可能的。例如，在[9]中，包程序保证终止，因此永远不会使用无限数量的路由器周期。研究人员将探索在资源需求方面限制行为和限制可表达性以及活动数据包的灵活性之间的权衡。然而，并非所有潜在的有害行为都可以通过这种方式消除。因此，在第二个方面，研究人员将考虑明确说明数据包在网络中的资源使用的机制。例如，每个分组可以携带资源界限，该资源界限随着资源的使用而递减，并且当界限用完时触发终止。所提出的研究结合了隐式和显式机制来控制资源的使用，与算法来控制流量进入网络，以减少拒绝服务的可能性。更一般地，可以设想评估在拥塞资源上执行的活动分组的成本。因此，在第三个方面，研究人员建议研究基于拥塞成本的机制，以实现更有效的资源分配，以及如何通过主动数据包促进资源分配。首先，研究人员将利用数学建模来激励利益，并研究所提出的解决方案的特征。其次，研究人员将利用专业知识和过去在实施主动网络方面的工作来证明构建什么是可行的，并探索每个解决方案对最终应用的限制。最后，研究人员将使用网络模拟来研究实验测试平台无法实现的规模的系统。

The Internet is used by a rapidly expanding and changing set of applications. The need for the network to evolve and even to provide application specific processing is significant. However the current network infrastructure is hard to evolve and does not readily support customizability. The goal of Active Networking [21, 3, 2] is to facilitate this evolution and customization by making the network infrastructure programmable. One way of adding programability is to allow code to be down-loaded into the routers, thus enabling the addition or modification of services. A more radical approach is to allow the packets themselves to carry programs to be executed selectively on the network's routers. Among other issues, these two approaches increase the possibility of denial of service attacks whereby a user places excessive demands on network resources in order to deny access to another user. However, they also enable new approaches to handling such attacks and to addressing the general problem of allocating resources within the network.The proposed research focuses on issues involving programmable, or active, packets. Active packets facilitate denial of service attacks in several ways. First, unlike conventional data transport packets, an active packet may require processor cycles and memory at the routers beyond those needed to simply forward the packet. Second, in general, the execution of an active packet at a router may cause more than one active packet to be transmitted from the router. Such behavior is useful, since it allows a packet to fan out across the network, but it is potentially dangerous since it can lead to an exponential growth in the resources used by a single initial packet. Experience with active packet-based systems [9, 8, 23, 22, 24] suggests that denial of service is the single biggest obstacle which must be overcome before such systems are feasible.The proposed research tackles this problem along various fronts. First, the researchers propose to design packet programming languages that make some types of behavior intrinsically impossible. For example, in PLAN [9], packet programs are guaranteed to terminate and thus can never use an un-bounded number of router cycles. The researchers will explore tradeoffs between restricting behavior in terms of resource requirements and limiting the expressibility and thus the flexibility of active packets. However, not all potentially harmful behaviors can be eliminated in this manner. Thus, on a second front, the researchers will consider mechanisms that explicitly account for a packet's resource usage in the network. For example, each packet may carry a resource bound, which is decremented as resources are used, and which triggers termination when the bound is used up. The proposed research combines both implicit and explicit mechanisms for controlling resource usage, with algorithms to control the flow of traffic into the network to decrease the likelihood of denial of service. More generally, one can envisage assessing costs to active packets that execute on congested resources. Thus, on a third front, the researchers propose to investigate mechanisms based on congestion costs to achieve more efficient resource allocations and how they can be facilitated via active packets.Three methodologies will be used to validate proposed solutions. First, the researchers will draw on mathematical modeling to motivate the benefits and investigate the characteristics of the proposed solutions. Second, the researchers will leverage expertise and past work on implementing active networks to demonstrate what is feasible to build, and explore the constraints each solution will place on eventual applications. Finally, the researchers will use network simulation to investigate systems on a scale not achievable on the experimental testbeds.