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

互联网被一组迅速扩展和变化的应用程序所使用。网络需要不断发展，甚至需要提供特定于应用的处理。然而，当前的网络基础设施很难发展，而且不容易支持可定制化。主动网络[21、3、2]的目标是通过使网络基础设施可编程来促进这种演变和定制。增加可编程性的一种方法是允许将代码下载到路由器中，从而能够添加或修改服务。一种更激进的方法是允许数据包本身携带程序，这些程序将在网络的路由器上有选择地执行。在其他问题中，这两种方法增加了拒绝服务攻击的可能性，在拒绝服务攻击中，用户对网络资源提出过高的要求，以拒绝另一用户的访问。然而，它们也提供了新的方法来处理这类攻击和解决网络中分配资源的一般问题。拟议的研究集中在涉及可编程或活动分组的问题上。活动数据包以多种方式为拒绝服务攻击提供便利。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上的处理器周期和内存，而不仅仅是转发该分组所需的处理器周期和内存。第二，通常，在路由器上执行活动分组可能会导致从该路由器传输多于一个活动分组。这种行为很有用，因为它允许数据包在网络上散开，但它也有潜在的危险，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[9，8，23，22，24]的经验表明，拒绝服务是在此类系统可行之前必须克服的最大障碍。首先，研究人员建议设计分组编程语言，使某些类型的行为本质上是不可能的。例如，在PLAN[9]中，包程序被保证终止，因此永远不能使用无限数量的路由器周期。研究人员将探索在限制资源需求方面的行为和限制可表现性以及活动分组的灵活性之间的权衡。然而，并不是所有潜在的有害行为都可以通过这种方式消除。因此，在第二方面，研究人员将考虑明确说明分组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，并且当该界限用完时触发终止。拟议的研究将控制资源使用的隐式和显式机制与控制进入网络的流量的算法相结合，以降低拒绝服务的可能性。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，在第三方面，研究人员建议调查基于拥塞成本的机制以实现更有效的资源分配，以及如何通过活动数据包来促进这些机制。将使用三种方法来验证所提出的解决方案。首先，研究人员将利用数学建模来激发好处，并调查拟议解决方案的特点。其次，研究人员将利用实施主动网络的专业知识和过去的工作来演示构建什么是可行的，并探索每个解决方案将对最终应用施加的限制。最后，研究人员将使用网络模拟来研究在实验试验台上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.