Multicasting, the transmission of a packet to a group of hosts, is an important service for improving the efficiency and robustness of distributed systems and applications. Although multicast capability is available and widely used in local area networks, when those LANs are interconnected by store-and-forward routers, the multicast service is usually not offered across the resulting internetwork. To address this limitation, we specify extensions to two common internetwork routing algorithms-distance-vector routing and link-state routing-to support low-delay datagram multicasting beyond a single LAN. We also describe modifications to the single-spanning-tree routing algorithm commonly used by link-layer bridges, to reduce the costs of multicasting in large extended LANs. Finally, we discuss how the use of multicast scope control and hierarchical multicast routing allows the multicast service to scale up to large internetworks.

We design a reset subsystem that can be embedded in an arbitrary distributed system in order to allow the system processes to reset the system when necessary. Our design is layered, and comprises three main components: a leader election, a spanning tree construction, and a diffusing computation. Each of these components is self-stabilizing in the following sense. If the coordination between the up processes in the system is ever lost (due to failures or repairs of processes and channels) then each component eventually reaches a state where coordination is regained. This capability makes our reset subsystem very robust: it can tolerate fail-stop failures and repairs of processes and channels even when a reset is in progress. Categories and Subject Descriptors: C.2.4 [Computer Communication Systems]: Distributed Systems--distributed applications, network operating systems ; D.1.3 [Programming Techniques]: Concurrent Programming ; D.4.5 [Operating Systems]: Reliability--verification, fa...

Read it as an adjunct to the lectures on distributed systems, links, and switching. It gives a fairly complete description of a working highly-available switched network providing daily service to about 100 hosts. The techniques used to obtain high reliability and fault-tolerance are characteristic of many distributed systems, not just of networks. The paper also makes clear the essential role of software in modern networks.

this paper appeared in the 32nd Proceedings of the IEEE Foundations of Computer Science (FOCS) Conference, 1991.

We show how to use an interactive theorem prover, HOL, together with a model checker, SPIN, to prove key properties of distance vector routing protocols. We do three case studies: correctness of the RIP standard, a sharp realtime bound on RIP stability, and preservation of loop-freedom in AODV, a distance vector protocol for wireless networks. We develop verification techniques suited to routing protocols generally. These case studies show significant benefits from automated support in reduced verification workload and assistance in finding new insights and gaps for standard specifications.

Autonet is a switch-based local area network using 100 Mbit/s full-duplex point-to-point links. Crossbar switches are interconnected to other switches and to host controllers in an arbitrary pattern. Switch hardware uses the destination address in each packet to determine the proper outgoing link for the next step in the path from source to destination. Autonet automatically recalculates these forwarding paths in response to failures and additions of network components. This automatic reconfiguration allows the network to continue normal operation without need of human intervention. Reconfiguration occurs quickly enough that higher-level protocols are not disrupted. This paper describes the fault monitoring and topology acquisition mechanisms that are central to automatic reconfiguration in Autonet.

We consider challenges associated with application domains in which a large number of distributed, networked sensors must perform a sensing task repeatedly over time. We address issues such as resource constraints, utility associated with a sensing task, and achieving global objectives with only local information. We present a model for such applications, in which we define appropriate global objectives based on utility functions and specify a cost model for energy consumption. In the full version of this paper, we present algorithms and experimental results for this problem domain [2].

Baruch Awerbuch 12 , Boaz Patt-Shamir 2 , George Varghese 3 and Shlomi Dolev 45 1 Dept. of Computer Science, Johns Hopkins University 2 Lab. for Computer Science, MIT 3 Dept. of Computer Science, Washington University 4 Dept. of Computer Science, Texas A&M University 5 School of Computer Science, Carleton University Abstract. We describe a method for transforming asynchronous network protocols into protocols that can sustain any transient fault, i.e., become self-stabilizing. We combine the known notion of local checking with a new notion of internal reset, and prove that given any self-stabilizing internal reset protocol, any locally-checkable protocol can be made self-stabilizing. Our proof is constructive in the sense that we provide explicit code. The method applies to many practical network problems, including spanning tree construction, topology update, and virtual circuit setup. 1 Introduction A network protocol is called self-stabilizing (or stabilizing for sho...

As the number of hosts attached to a network increases beyond what can be connected by a single local area network (LAN), forwarding packets between hosts on different LANs becomes an issue. Two common solutions to the forwarding problem are IP routing and spanning tree bridging. IP routing scales well, but imposes the administrative burden of managing subnets and assigning addresses. Spanning tree bridging, in contrast, requires no administration, but often does not perform well in a large network, because too much traffic must detour toward the root of the spanning tree, wasting link bandwidth. This paper introduces a new architecture, called SmartBridge, that combines the good features of IP routing and spanning tree bridging. We have implemented the SmartBridge design for 10 Mb/s and 100 Mb/s Ethernet LANs, using standard PC hardware with off-the-shelf network interface cards and running our algorithms in software. Our 100 Mb/s system runs at full link bandwidth. 1.

Neighbor graphs can be utilized to obtain a 99 percent reduction in the authentication time of an IEEE 802.11 handoff (full EAP-TLS) by proactively distributing necessary key material one hop ahead of the mobile user.