Spanning Tree Protocol

Ethernet switched networks do not scale appropriately due to limitations inherent to the spanning tree protocol. Ethernet architectures based on routing over a virtual topology in which turns are prohibited offer improved performance over spanning tree, although in some cases suffer from excessive computational complexity. Up/Down routing is a turn prohibition algorithm with low computational complexity. In this paper we

Many real-time applications, such as video conferencing, require the transmission of flows from a sender to multiple receivers subject to Quality of Service (QoS) delivery constraints (e.g. bounded delay). Traditional multicast routing algorithms used for solving the Sterner tree problem cannot be used in this scenario, because QoS constraints on links are not considered. Moreover, with QoS metrics consideration, the

Ethernet is widely used in Local Area Networks (LANs) due to its simplicity and cost effectiveness. Today, a great deal of effort is being devoted to extending Ethernet capabilities in order to elevate it from a LAN technology to a ubiquitous networking technology, suitable for deployment in Metropolitan Area Networks (MANs) and even in core, Wide Area Networks (WANs). Current standardized Ethernet networks are based on a spanning tree topology, using the Rapid Spanning Tree Protocol (RSTP) or Multiple Spanning Tree Protocol (MSTP). The spanning tree architecture is useful for avoiding forwarding loops, but may lead to low link utilization and long failure recovery time. In this paper we propose to shift from tree to Directed Acyclic Graph (DAG) topologies and offer a new bridged Ethernet architecture called Orient. Orient is based on assigning an orientation state to each port in the network in order to prevent loops. Thus, the Orient architecture enables a full utilization of all network links and ports, while maintaining simplicity of implementation and compliance with the standardized spanning tree protocols.

In mobile ad hoc networks (MANETs) mobile nodes do not have access to a fixed network infrastructure and they set up a communication network by themselves. MANETs require implementation of a wireless Medium Access Control (MAC) layer. Existing MAC algorithms that consider no mobility, solve the problem of eventually guaranteeing every node with a share of the communications bandwidth. In the context of MANETs, we ask: Is there an efficient MAC algorithm when mobility is considered? MANETs are subject to transient faults, from which self-stabilizing systems can recover. The self-stabilization design criteria, and related concepts of self-⋆, liberate the application designer from dealing with low-level complications, and provide an important level of abstraction. Whereas stabilization criteria are important for the development of autonomous systems, adaptation is imperative for coping with a variable environment. Adapting to a variable environment requires dealing with a wide range of practical issues, such as relocation of mobile nodes and changes to the motion patterns. This work proposes the design and proof of concept implementation of an adapted MAC algorithm named Chameleon-MAC, which is based on a self-stabilizing algorithm by Leone et al., and uses self-⋆ methods in order to further adapt its behavior according to the mobility characteristics of the environment. Moreover, we give an extensive treatment of the aspects and parameters that can bring the algorithm into the practical realm and we demonstrate documented behavior on real network studies (MICAz 2.4 GHz motes) as well as using simulation (TOSSIM [32]), showing improved overhead and fault-recovery periods than existing algorithms. We expect that these advantages, besides the contribution in the algorithmic front of research, can enable quicker adoption by practitioners and faster deployment.

Page 1. 50 IEEE TRANSACTIONS ON RELIABILITY, VOL. 42, NO. 1, 1993 MARCH A Modular-Network Architecture for Performance Enhancement in Extended Local Area Network V. Catania A. Puliafito L. Vita, Member IEEE University of Catania, Catania ...