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The unprecedented proliferation of packet-based services such as numerical television, video on demand, is pushing
Metropolitan Area Networks (MANs) providers to reconsider their network infrastructures. The existing circuit-based
networks are becoming inefficient and costly in supporting the new requirements in terms of quality of service and
bandwidth of sporadic packet-based traffic. To solve this problem, new MAN infrastructures are needed.
Many propositions of new network solutions were made during the last decade in order to respond to the
aforementioned issues, such as Next Generation SONET/SDH, Resilient Packet Ring (RPR). Among others, the optical
networking technology appears as a technology of choice for the next generation MANs. The main benefit of optical
technology can be resumed in the following terms: huge transmission capacity, high reliability, and high availability.
This paper is devoted to provide an overview of the MAN infrastructure, and particularly to its evolution towards optical
packet switching (OPS) networks, during the last decades. It also highlights performance issues in optical networking in
metro area in terms of optical packet format, medium access control (MAC) protocol and quality of service (QoS), as
well as traffic engineering issues.
We first begin with a brief state-of-the-art and perspective on optical networking in metropolitan area. Next, we
provide the necessary arguments for an answer to the problem of the choice of packet format (fixed format versus
variable format) to be adopted in future metropolitan optical packet switching networks. Comparison of different optical
packet formats at the electronic to optical (E/O) interface is carried out, followed by the analysis of the impact of optical
packet format choices on overall network performance. Then, we explore the performance issue at MAC layer and
discuss improvement mechanisms for MAC protocol. Here, fairness and bandwidth utilization issues are specifically
investigated. Finally, we discuss about how to guarantee QoS in optical packet switching OPS metro networks,
illustrated by a few mechanisms allowing the transport of TDM traffic over packet switching networks (e.g., Circuit
Emulation Service - CES).
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