Synchronous optical networking

Summary

Synchronous Optical Networking (SONET) and Synchronous Digital Hierarchy (SDH) are standardized protocols that transfer multiple digital bit streams synchronously over optical fiber using lasers or highly coherent light from light-emitting diodes (LEDs). At low transmission rates data can also be transferred via an electrical interface. The method was developed to replace the plesiochronous digital hierarchy (PDH) system for transporting large amounts of telephone calls and data traffic over the same fiber without the problems of synchronization. SONET and SDH, which are essentially the same, were originally designed to transport circuit mode communications (e.g., DS1, DS3) from a variety of different sources, but they were primarily designed to support real-time, uncompressed, circuit-switched voice encoded in PCM format. The primary difficulty in doing this prior to SONET/SDH was that the synchronization sources of these various circuits were different. This mea

Official source

https://en.wikipedia.org/wiki/Synchronous_optical_networking

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Optical burst switching (OBS) is able to operate under both asynchronous and synchronous burst departures. Although the asynchronous approach is generally assumed in OBS owing to its simplicity and low technical requirements, it has been shown that performance improvements, in terms of the overall burst loss probability, can be achieved under synchronous operation. Moreover, when effective contention resolution mechanisms are applied, such improvements are significant. Since perfect synchronization is not a viable solution, we propose a novel operation mode with relaxed technical requirements, the quasi-synchronous (QS) operation. In this paper, the performance of the QS operation mode is evaluated by an exact analytic expression, assuming a Poisson burst arrival process and a single-wavelength scenario. This mathematical analysis is completed with numerical results that validate its accuracy. Furthermore, we tackle the issue of not having well-aligned clock information between network nodes by proposing a novel re-synchronization mechanism for OBS networks. Finally, a performance study of the QS operation under different deflection routing techniques is presented. The results show that our novel QS approach achieves significant performance benefits with respect to the asynchronous operation while avoiding the architectural complexity of the synchronous scheme.

2011

The article analyzes the influence of the IP access interface on the packet loss probability and delay times in the optical packet switched network. The network and node model have been proposed, and the assembler and hold features have been included in the analysis. It has been shown that the increase of the maximum optical packet sizes, as well as holding feature as contention resolution mechanism, decrease the packet loss ratio, but introduce delays at the optical network access points. The modeling and analysis were. based on discrete event simulation assuming self-similar traffic sources.

Ieee Service Center, 445 Hoes Lane, Po Box 1331, Piscataway, Nj 08855-1331 Usa2004

The article analyzes the influence of the Internet Protocol (IP) access interface on the packet loss probability and delay times in the optical packet switched network. The network and node model have been proposed, and the structure of the IP access interface, including assembler and holder, have been included in the analysis. It has been shown that the increase of the maximum optical packet sizes, as well as use of the holding feature as contention resolution mechanism, decrease the packet loss probability, but introduce delays at the optical network access points. Modeling and analysis were based on the discrete event simulation assuming self-similar traffic sources. IP packet lengths were modeled using empirical data.

2006