The spanning tree protocol is the component of the Ethernet architecture that establishes the network connectivity. Its plug-and-play property and ease of configuration have been some of the pillars of Ethernet's success. However, the new provider applications require improving the protocol capabilities such as response time, path optimality and path control. Optimal paths can be achieved if we deploy one tree rooted at each node. Nevertheless, this introduces the challenge of maintaining the path symmetry requirement of Ethernet networks. In this paper we propose RSTP-SP as an extension to RSTP that meets the performance objectives and keeps the bridging requirements. We evaluate RSTP-SP by means of a simulation analysis and we compare it to Shortest Path Bridging (SPB). Simulation results show that RSTP-SP outperforms SPB in terms of recovery time and outage experienced. In contrast, the message overhead introduced by RSTP-SP is higher than in the SPB case.

Hardware-timestamping is essential for achieving tight synchronization in networking applications. This mechanism is selectively used on few high-cost tailored systems. Actual muP-based implementations fail on deterministic timestamp retrieval and insertion inside the message. This problem degrades significantly the synchronization between network nodes. This paper describes the analysis, implementation, and evaluation of a HW-timestamping technique for minimal-latency timestamping at Gigabit Ethernet using a low-cost off-the-shelf FPGA board. The effectiveness of the method is validated through a point-to-point synchronization scheme achieving a best-case synchronization accuracy of 150 ns.

Network traces are a valuable source of information for modeling and analysis of network behavior and for the evaluation of network protocols. These crucial activities should be supported with reliable traffic traces. Reliable packet capturing facilities should be devoted to avoid losing packets and at the very last, report when packets have been lost with the highest accuracy possible. This paper describes a methodological approach to maximize the accuracy in the packet loss monitoring. The approach lies on the monitoring of appropriate statistical indicators directly from Ethernet hardware. These indicators become the enablers for the collection of metadata traces in parallel with the standard trace collections. The resulting meta-traces are proposed as a mechanism to monitor packet loss accuracy at the packet level as they provide the means to identify the exact location and amount of the packet loss in the collected traces files. We describe an evaluation use case of our approach with commodity hard- and software. The conclusion drawn from our experimental set up configuration is that it is possible to maximize the accuracy of the packet loss monitoring for reliable trace collections at affordable costs.

Collection of packet traces for future analysis is a very meticulous work that must guarantee accurate traces in order for these traces to be valuable for analysis. Current platforms do not provide a means to measure this accuracy. This paper describes a real-time monitoring method to measure the quality of a collected trace. The method takes a system architecture approach monitoring different points of the system to account for all potential drops of the packet journey. A set of metadata is stored in metatraces to be analyzed together with the trace after the capturing. The primary information is taken from standard Ethernet counters which are available in all commodity hardware and therefore performs very well without expensive specific hardware. The paper presents the evaluation of the real-time monitoring method concluding that the processing overhead does not produce significant performance degradation and that it improves packet loss detection up to orders of magnitude depending on different scenarios.

Cable plants were initially designed for one-way broadcast of analog television signals (from the head-end to the neighborhood). They are now being upgraded to provide an upstream path (from the home to the head-end). New challenges arise in using the upstream channel since the available bandwidth is low and the noise levels are high. Different variations of the reservation Aloha protocol have been proposed as the MAC protocol to efficiently share the scarce upstream capacity. The efficiency of the reservation protocol highly depends on the capacity assigned to the reservation channel. In this paper we present a control mechanism that dynamically adjusts the operating parameters to the current load on the system. The control mechanism does not require any framing structure and is built around a "sea of mini-slots". The performance under both static and highly dynamic loads is close to optimum. The station implementation remains particularly simple and the downstream control structure is also simple. Results are given here for fixed length data units (ATM cells) but the algorithm extends very simply to variable length MAC frames.

The cable TV plant is a broad bandwidth channel into the home and community that has been used primarily for the distribution of television. As the plant is upgraded, there is an opportunity to use it for the transport of high-speed digital signals. While the downstream channel is relatively easy to exploit, the topology and physical characteristics of the upstream channel present new challenges at both the physical and the media access layers. We present a media access protocol that efficiently transfers data on this channel. A primary goal of the design is to keep that portion of the protocol resident in the station as simple as possible. Thus, we use centralized control located in the cable head-end. A station wishing to transmit sends a request to the head-end using a contention channel. The head-end acknowledges the request and then schedules the request, informing the station, by means of a grant message, exactly when to transmit. The protocol performs efficiently under a wide range of conditions, and is robust in the presence of channel errors.

A revolution is occurring in the scope and range of information, communication and education services that will be made available to schools, libraries, town-halls, clinics and, most importantly, residences. These services will be provided initially, primarily over hybrid fiber-cable systems, either by telephone companies or cable companies. The old cable plant is being upgraded and used in totally new ways. The topology and physical characteristics of the upstream channel present new challenges for efficient channel access. We present a media access protocol that efficiently transfers data on this channel. A primary goal in the design was to keep the portion of the protocol resident in the station as simple as possible. Thus we use centralized control located in the cable head-end and minimize intelligence in the station. We refer to this protocol as centralized priority reservation or CPR. A station wishing to transmit sends a request to the head-end using a contention channel. The head-end acknowledges the request and then schedules the request, informing the station by means of a grant message when to transmit. The protocol performs well under heavy load. Performance is affected little by the number of stations, the speed of the system and the physical length of the system.