The growing availability of multiple network interfaces on mobile devices makes concurrent multipath transfer an appealing candidate to satisfy the ever increasing user demand for bandwidth. As of today, the only transport protocol supporting multihoming is the stream control transmission protocol (SCTP); yet, SCTP can only exploit at most one of the available paths at any given time. This paper introduces sender-based packet pair SCTP (SBPP-SCTP) and westwood SCTP (W-SCTP), which add concurrent multipath support to the original SCTP. The two protocols are implemented on Linux and their performance is assessed on an experimental testbed emulating different wireless-channel bandwidth and delay conditions.

Software routers are becoming an important alternative to proprietary and expensive network devices, because they exploit the economy of scale of the PC market and open-source software. When considering maximum performance in terms of throughput, PC-based routers suffer from limitations stemming from the single PC architecture, e.g., limited bus bandwidth, and high memory access latency. To overcome these limitations, in this paper we present a multistage architecture that combines a layer-2 load-balancer front-end and a layer-3 routing back-end, interconnected by standard Ethernet switches. Both the front-end and the back-end are implemented using standard PCs and open- source software. After describing the architecture, evaluation is performed on a lab test-bed, to show its scalability. While the proposed solution allows to increase performance of PC- based routers, it also allows to distribute packet manipulation functionalities, and to automatically recover from component failures.

This paper reports on the implementation of Time-Driven Priority (TDP) scheduling on a FreeBSD platform. This work is part of a TDP prototyping and demonstration project aimed at showing the implications of TDP deployment in packet-switched networks, especially benefits for real-time applications. This paper focuses on practical aspects related to the implementation of the technology on a Personal Computer (PC)-based router and presents the experimental results obtained on a testbed network. The basic building blocks of a TDP router are described and implementation choices are discussed. The relevant results achieved and here presented can be categorized into two types: qualitative results, including the successful integration of all needed blocks and the insight obtained on the complexity related to the implementation of a TDP router, and quantitative ones, including measures of achievable network utilization and of jitter experienced on a fully-loaded TDP network. The outcome demonstrates the effectiveness of the presented implementation while confirming TDP points of strength.

DAVID is a research project sponsored by the European Union aimed at the design of an optical packet-switched network for the transport of IP traffic. The DAVID network has a two-level hierarchical structure, with a backbone of optical packet routers interconnected in a mesh, and metropolitan areas served by sets of optical rings interconnected by passive memoryless devices called Hubs. The paper focuses on the metropolitan area network and its components: the nodes and the Huh. Access is regulated by a dynamic time-division multiple-access scheme allocating slots in sets of wavelengths that provide multichannel pipes among ring pairs. This paper proposes a new resource allocation scheme capable of transporting variable-size packets without segmentation into fixed-size data units. Resource sharing among nodes is granted by two scheduling algorithms running on different time scales: the first one is centralized at the Hub and provides coarse connectivity among ring pairs; the second one runs at nodes and provides finer node-to-node connectivity. The Hub scheduling algorithm is derived from well known algorithms in the literature; a novel heuristic scheduling algorithm running at nodes is proposed for datagram (not-guaranteed) traffic and its performance is studied by simulation.

The data and voice integration over dense wavelength-division-multiplexing (DAVID) project proposes a metro network architecture based on several wavelength-division-multiplexing (WDM) rings interconnected via a bufferless optical switch called Hub. The Hub provides a programmable interconnection among rings on the basis of the outcome of a scheduling algorithm. Nodes connected to rings groom traffic from Internet protocol routers and Ethernet switches and share ring resources. In this paper, we address the problem of designing efficient centralized scheduling algorithms for supporting multiclass traffic services in the DAVID metro network. Two traffic classes are considered: a best-effort class, and a high-priority class with bandwidth guarantees. We define the multiclass scheduling problem at the Hub considering two different node architectures: a simpler one that relies on a complete separation between transmission and reception resources (i.e., WDM channels) and a more complex one in which nodes fully share transmission and reception channels using an erasure stage to drop received packets, thereby allowing wavelength reuse. We propose both optimum and heuristic solutions, and evaluate their performance by simulation, showing that heuristic solutions exhibit a behavior very close to the optimum solution.

In small cell-based Internet protocol routers, multicast traffic is generally handled by appending to each cell a local multicast label (LML) containing a bitmap with as many bits as switch ports, so as to identify the ports to which a copy of the cell has to be transferred. This approach is not feasible for switches having 128 ports or more, because the LML length would rise above 16 bytes, thus representing an intolerable overhead, given the small size of cells (typically 64 bytes). We discuss both static and adaptive lossy compression algorithms to reduce the size of LMLs to be attached to multicast cells, at the price of the delivery of cells to a larger set of outputs than necessary, and we compare the compression algorithms performance in terms of switch bandwidth waste, using both analytical and simulation models.

We present the Distributed Frame-Definition Algorithm (DFDA), a novel scheduling policy for input-queued switches with virtual output queueing at the input line cards. The DFDA effectively supports the integration of traffic classes with diverse Quality-of-Service (QoS) requirements (as compelled by emerging QoS frameworks such as Differentiated Services), and scales well with the aggregate capacity of the switch because of the limited complexity of its distributed implementation. The input and output tine cards exchange a minimal amount of control information to define the periodic service schedule that regulates transit through the switch fabric. The composition of the service schedule dynamically adapts to the tight bandwidth requirements of real-time traffic and to the load fluctuations of best-effort traffic. We assess the performance of the DFDA through simulation, and compare it with the most popular scheduling algorithms for input-queued switches. Our experiments show that the DFDA generally sustains higher throughput than the schemes of the prior art.

We investigate techniques for the support of multicast traffic in IP routers that have a large number of switch fabric ports (from 128 to 1024) and internally operate on relatively small fixed-size data units (cells of 64 bytes each). In small packet switches, multicast traffic is typically handled by prepending a local multicast label (LML) to each cell. The LML consists of a bitmap with as many bits as switch ports. The bitmap identifies the set of ports to which copies of the cell must be transferred. The bitmap approach is no longer feasible in switches with 128 ports or more, where the LML length cannot be smaller than 16 bytes, an intolerable overhead when the internal cell payload is only 64 bytes. We devise several compression algorithms, both static and adaptive, to reduce the size of the LML's to be attached to multicast cells. The algorithms define compressed representations of the distribution sets of the multicast cells, trading the additional bandwidth needed to transfer redundant cell copies (i.e., copies directed to outputs that do not belong to the actual distribution sets) for the cell header overhead otherwise needed to deliver the cells only to the proper outputs. We use simulation experiments to compare the performance of the compression algorithms.

We consider all-optical TDM/WDM broadcast and select networks. We assume that each network node is equipped with one fixed transmitter and one tunable receiver; tuning times are assumed to be not negligible with respect to the slot time. We discuss efficient scheduling algorithms to assign TDM/WDM slots to multicast traffic in such networks. Given the problem complexity, heuristic algorithms based on the Tabu Search methodology are proposed, and their performance is assessed using randomly created request matrices based on two types of multicast traffic patterns: a video-conference, and a server distribution traffic pattern. The considered performance index is the frame length required to schedule a given traffic request matrix.