This paper presents ModelNet, a scalable Internet emulation environment that enables researchers to deploy unmodified software prototypes in a configurable Internet-like environment and subject them to faults and varying network conditions. Edge nodes running user-specified OS and application software are configured to route their packets through a set of ModelNet core nodes, which cooperate to subject the traffic to the bandwidth, congestion constraints, latency, and loss profile of a target network topology. This paper describes and evaluates the ModelNet architecture and its implementation, including novel techniques to balance emulation accuracy against scalability. The current ModelNet prototype is able to accurately subject thousands of instances of a distrbuted application to Internet-like conditions with gigabits of bisection bandwidth. Experiments with several large-scale distributed services demonstrate the generality and effectiveness of the infrastructure.
New demands brought by the contirruing growth of the Internet will be met in part by more gective use of caching in the Web and other services. We have developed CRISP, a distributed Internet object cache targeted to the needs of the organizations that aggregate the end users of Internet services, particularly the commercial Internet Service Providers (ISPs) where much of the new growth occurs.A CRISP cache consists of a group of cooperating caching servers sharing a central directory of cached objects. This simple and obvious strategy is easily overlooked due to the well-known drawbacks of a centralized structure. However, we show that these drawbacks are easily overcome for well-configured CRISP caches.We outline the rationale behind the CRISP design, and report on early studies of CRISP caches in actual use and under synthetic load. While our experience with CRISP to date is at the scale of hundreds or thousands of clients, CRISP caches could be deployed to maximize capacity at any level of a regional or global cache hierarchy.
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