SONET Transport Research Articles

Performance Evaluation of Transmission Algorithms for CSMA/ID WDM Ring Networks

As data traffic increase rapidly, IP over WDM (Wavelength Division Multiplexing) transport will replace conventional SONET transport in current metropolitan area networks. Such networks will require new MAC protocols to efficiently share network bandwidth among multiple network nodes. This research project describes and evaluates a novel Carrier Sense Multiple Access with Idle Detection (CSMA/ID) MAC protocols for IP over WDM ring networks. The paper focuses on the influence of performance for the packet scheduling algorithms included FIFO, OPF_CA and OPF_CF. An analytical model is developed to evaluate the performance of the protocol, with simulation results showing good network efficiency and will be an excellent candidate for next-generation metro networks.

HORNET: a packet-over-WDM multiple access metropolitan area ring network

Current metropolitan area networks (MANs) based on the SONET transport are not developing at the rate required to support the phenomenal increase in data traffic. To address the needs of future MANs, the Optical Communications Research Laboratory at Stanford University and Sprint Advanced Technology Laboratories are building HORNET (Hybrid Optoelectronic Ring NETwork). HORNET has a multiple access architecture, in which nodes access any WDM channel using a novel media access control protocol and fast tunable laser transmitters. HORNET transports data packets directly over the WDM ring, eliminating the SONET transport. This paper presents the HORNET architecture, the node design consisting of novel packet-over-WDM components, and the experimental testbed with results.

IP layer restoration and network planning based on virtual protection cycles

We describe a novel restoration strategy called virtual protection cycles (p-cycles, patents pending) for extremely fast restoration in IP networks. Originally conceived for use in WDM and Sonet transport networks, we outline the adaption of the p-cycle concept to an IP environment. In an IP router-based network, p-cycles are implemented with virtual circuits techniques (such as an MPLS label switched path, or other means) to form closed logical loops that protect a number of IP links, or a node. In the event of failure, packets which would normally have been lost are encapsulated with a p-cycle IP address and reenter the routing table, which diverts them onto a protection cycle. They travel by normal forwarding or label switching along the p-cycle until they reach a node where the continuing route cost to the original destination is lower than that at the p-cycle entry node. Diverted packets are deencapsulated (dropped from the p-cycle) at that node and follow a normal (existing) route from there to their destination. Conventional routing protocols such as OSPF remain in place and operate as they do today, to develop a longer term global update to routing tables. Diversionary flows on the p-cycle inherently cease when the global routing update takes effect in response to the failed link or node. The p-cycle thus provides an immediate real-time detour, preventing packet loss, until conventional global routing reconvergence occurs. The aim of the paper is to explain the basic p-cycle concept and its adaptation to both link and node restoration in the IP transport layer, and to outline certain initial results on the problem of optimized design of p-cycle based IP networks.

WDM metropolitan area network based on CSMA/CA packet switching

The bursty nature of traffic in metropolitan area networks results in underutilized and inefficient SONET networks. The hybrid optoelectronic ring network (HORNET) is a network being developed at the Optical Communications Research Laboratory at Stanford University to address the problems of SONET transport in metropolitan area networks (MAN's). HORNET performs packet switching using a fast-tunable wavelength transmitter, which hops to different wavelengths on a packet-by-packet basis. In this letter, we present simulation results which quantify the benefits of a wavelength tunable transmitter in a packet switched wavelength-division-multiplexed MAN. We show that a tunable transmitter is able to take advantage of imbalances in wavelength utilization, and provides a 45% improvement in packet latency characteristics. We also show that in order to maintain these benefits the tuning time of the transmitter cannot exceed 10% of the packet transmit time.

Broadband Gigabit Research and the LuckyNet Testbed

This paper describes the motivation, architecture, initial applications, and objectives for LuckyNet, an AT&T Bell Labs gigabit research network. Building upon the B-ISDN infrastructure of SONET transport and the ATM packet protocol, LuckyNet will provide a fertile testbed for investigating: broadband applications, network architectures, gigabit packet switches and LANs, high-throughput protocols and interfaces, and network services and operations (including addressing, routing, signaling, control and security).LuckyNet is a heterogeneous network that has as one of its major objectives the demonstration that diverse classes of user traffic (i.e., video, voice, data, and image), as well as control and management information can efficiently utilize a single ATM infrastructure. Another goal is to provide users with gigabit-per-second network access. Initial applications provide 155 Mbps access and include video conferencing, document retrievaL low-latency processor-sharing, and Ethernet interconnection. We expect that this will be followed by FDDI interconnection and multimedia conferencing, with the long-range goal of identifying and supporting gigabit-per-second applications. Extensions to other locations and interworking with NREN sites (e.g., AT&T Bell Labs XUNET II) are anticipated. The network already links the Holmdel and Crawford Hill Laboratories (via optical fiber) and the Crawford Hill and Murray Hill Laboratories (via microwave radio) at 2.5 Gbps.

Fiber network survivability

At the transport layer in interoffice and interexchange networks, shared protection rings (SPRINGS) interconnected at matched nodes can provide 100% restoration in milliseconds after cable cuts and central office failures. The author introduces the SPRING and explains how its capacity advantage over other ring configurations enables it to be the most economical solution in more applications. Transport restoration technologies-1+1 diversity, digital crossconnect systems, and SPRINGS-in interoffice and interexchange environments are compared. A representative network study is presented to justify the choice of SPRINGs and matched nodes for the target architecture. Recommendations on how to evolve today's asynchronous networks in preparation for a fully survivable SONET ring-based network are also provided. Generic ring planning guidelines and network examples are presented to demonstrate how today's networks can be evolved to provide end-to-end survivable SONET transport. An approach to ring-based network design that simplifies the planning process and minimizes network cost is provided.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>