This paper presents the design and evaluation of Pastry, a scalable, distributed object location and routing substrate for wide-area peer-to-peer ap- plications. Pastry performs application-level routing and object location in a po- tentially very large overlay network of nodes connected via the Internet. It can be used to support a variety of peer-to-peer applications, including global data storage, data sharing, group communication and naming. Each node in the Pastry network has a unique identifier (nodeId). When presented with a message and a key, a Pastry node efficiently routes the message to the node with a nodeId that is numerically closest to the key, among all currently live Pastry nodes. Each Pastry node keeps track of its immediate neighbors in the nodeId space, and notifies applications of new node arrivals, node failures and recoveries. Pastry takes into account network locality; it seeks to minimize the distance messages travel, according to a to scalar proximity metric like the number of IP routing hops. Pastry is completely decentralized, scalable, and self-organizing; it automatically adapts to the arrival, departure and failure of nodes. Experimental results obtained with a prototype implementation on an emulated network of up to 100,000 nodes confirm Pastry's scalability and efficiency, its ability to self-organize and adapt to node failures, and its good network locality properties.

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Pastry: Scalable, Decentralized Object Location, and Routing for Large-Scale Peer-to-Peer Systems

A case for end system multicast

In today’s chaotic network, data and services are mobile and replicated widely for availability, durability, and locality. Components within this infrastructure interact in rich and complex ways, greatly stressing traditional approaches to name service and routing. This paper explores an alternative to traditional approaches called Tapestry. Tapestry is an overlay location and routing infrastructure that provides location-independent routing of messages directly to the closest copy of an object or service using only point-to-point links and without centralized resources. The routing and directory information within this infrastructure is purely soft state and easily repaired. Tapestry is self-administering, faulttolerant, and resilient under load. This paper presents the architecture and algorithms of Tapestry and explores their advantages through a number of experiments.

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Tapestry: An Infrastructure for Fault-tolerant Wide-area Location and Routing

A Resilient Overlay Network (RON) is an architecture that allows distributed Internet applications to detect and recover from path outages and periods of degraded performance within several seconds, improving over today's wide-area routing protocols that take at least several minutes to recover. A RON is an application-layer overlay on top of the existing Internet routing substrate. The RON nodes monitor the functioning and quality of the Internet paths among themselves, and use this information to decide whether to route packets directly over the Internet or by way of other RON nodes, optimizing application-specific routing metrics.Results from two sets of measurements of a working RON deployed at sites scattered across the Internet demonstrate the benefits of our architecture. For instance, over a 64-hour sampling period in March 2001 across a twelve-node RON, there were 32 significant outages, each lasting over thirty minutes, over the 132 measured paths. RON's routing mechanism was able to detect, recover, and route around all of them, in less than twenty seconds on average, showing that its methods for fault detection and recovery work well at discovering alternate paths in the Internet. Furthermore, RON was able to improve the loss rate, latency, or throughput perceived by data transfers; for example, about 5% of the transfers doubled their TCP throughput and 5% of our transfers saw their loss probability reduced by 0.05. We found that forwarding packets via at most one intermediate RON node is sufficient to overcome faults and improve performance in most cases. These improvements, particularly in the area of fault detection and recovery, demonstrate the benefits of moving some of the control over routing into the hands of end-systems.

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Resilient overlay networks

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Overcast is an application-level multicasting system that can be incrementally deployed using today's Internet infrastructure. These properties stem from Overcast's implementation as an overlay network. An overlay network consists of a collection of nodes placed at strategic locations in an existing network fabric. These nodes implement a network abstraction on top of the network provided by the underlying substrate network.Overcast provides scalable and reliable single-source multicast using a simple protocol for building efficient data distribution trees that adapt to changing network conditions. To support fast joins, Overcast implements a new protocol for efficiently tracking the global status of a changing distribution tree.Results based on simulations confirm that Overcast provides its added functionality while performing competitively with IP Multicast. Simulations indicate that Overcast quickly builds bandwidth-efficient distribution trees that, compared to IP Multicast, provide 70%-100% of the total bandwidth possible, at a cost of somewhat less than twice the network load. In addition, Overcast adapts quickly to changes caused by the addition of new nodes or the failure of existing nodes without causing undue load on the multicast source.

Overcast: reliable multicasting with on overlay network

A network appliance is capable of remote booting and obtaining its configuration information from a source located far away. The network appliance can be shipped to a business location or office environment without requiring a local boot server in that location or environment and without requiring the presence of a person who is familiar with and highly skilled in configuring the appliance. The invention allows for booting and the obtaining of configuration information, and therefore allows for the functioning of the appliance, regardless of whether there is a local server in the local network environment, such as a DHCP server or a boot server, that has been set up and configured to provide to the appliance the booting and configuration information it requires. Self-organizing distributed appliances (SODAs) according to the invention augment the Internet by providing a self-organizing network that efficiently distributes big data items, i.e., data items that cannot be downloaded timely (on demand) over today's networks. One application of self-organizing distributed appliances is the distribution of high-quality video (a half-hour MPEG-1 movies is about one Gbyte). The SODA network alleviates network bottlenecks.

Methods and apparatus for remote configuration of an appliance on a network

A system and method of routing requests received from client computers. The client computer processor is redirected to a router for which the address is within the preferred coverage zone. If a router is not identified for which the address is within a preferred coverage zone, but a router other than the router that received the request is identified for which the address is within a regular coverage zone, the processor is redirected to the router for which the address is within the regular coverage zone. If a message is transmitted from a router behind a firewall to a router outside the firewall, and then a request for data is received from a processor behind the firewall, the processor is redirected to the address of the router. Routers register themselves dynamically into a hierarchy. In another alternative embodiment, a service request from a particular client computer is serviced immediately by the root router rather than redirected to another router. The root router then attempts to find the best source server for the client computer. The next service request from the client computer is dispatched directly by the root router to this best router.

Methods and apparatus for routing requests in a network

Content servers are directed to send messages to network nodes which are used to obtain IP addresses and to receive responses from the network nodes. The responses provide network service information. The content servers collect data based on the responses and feed the data to a routing server. Based on the data fed to the routing server, respective choices of content servers are selected and provided to the network nodes to respond to clients requesting content server addresses from the network nodes.

Content server selection for accessing content in a content distribution network

In one embodiment, a first network node in a subnet retrieves a network configuration from a second network node located outside the subnet. The first network node communicates with at least one other network node to collect information from inter-node communication packets containing network address information other than an address assignment to the first network node. The first network node determines an available network address based on the network address information contained in the collected inter-node communication packets. The first network node is assigned the available network address and locates a network address for at least one subnet router. The network node accesses the second network node located outside the subnet, using the located network address for the at least one subnet router, for an available network configuration from a list of network configurations. The first network node is assigned the available network configuration.

M. Frans Kaashoek

Papers

Overcast: reliable multicasting with on overlay network

Methods and apparatus for remote configuration of an appliance on a network

Methods and apparatus for routing requests in a network

Content server selection for accessing content in a content distribution network

Method and apparatus for automatic network address assignment