Optical layer capacity and unit cost improvements are basic to the rapid growth of IP networks. However, the new rapid reconfiguration and restoration capabilities of the optical layer have been sparingly utilized by IP network operators. This is consistent with the economics: the widely deployed optical layer architecture based on a "discrete" optical crossconnect (DOXC - one not integrated into the WDM) incurs heavy interface costs. In addition, there are architectural and control issues which are roadblocks to IP exploitation of rapid optical layer agility. In the first part of the paper, we describe a next generation all-optical architecture based on OXCs integrated with the WDM ("IOXCs"), and one instantiation of this architecture using a class of reconfigurable degree-N optical add-drop multiplexer (OADM). A new shared mesh restoration mechanism based on hot standbys is designed to overcome slow convergence and transient behaviors that are typical in all-optical networks. A series of economic comparisons are made on both a 120-node hypothetical national network and a smaller express backbone network to demonstrate the cost effectiveness of the new IOXC-based restoration in comparison to the IP layer restoration after some optical layer failure that results in one or more IP link failures. In the IP over Optical architecture, the Optical Layer can provide its IP clients rapid and efficient restoration for IP link failures that are due to some optical layer failure; however its inability to protect against router and router interface failures erodes its attractiveness. In the second part of the paper, we propose a joint IP/Optical restoration mechanism to deal with this. It is suitable for IP offices with at least two backbone routers and an optical cross-connect. The OXC is used to re-terminate OC-48/OC-192 links from a failed backbone router to its mate. The entire interoffice portion of the re-terminated link is reused, thus minimizing the amount of additional inter-office capacity required to protect against router failures. The proposed scheme is also applicable to restoration for router interface failures as well as to cases with single backbone router office architecture.
The Internet has grown rapidly in the last several years. This is largely due to the simple, flexible, and robust connectionless nature of the Internet Protocol (IP). The Internet architecture has been successful up to this point, and the best effort service paradigm has been adequate. However, with increasing demands of supporting voice, video, mission critic data on IP, the best effort paradigm without differentiating traffic according to application requirements can not meet the market demands. In this paper, we summarize and compare two major models in IP Quality of Service (QoS): Integrated Services Model and Differentiated Services Model proposed in Internet Engineering Task Force (IETF), the main Internet standard committee. We also discuss other related areas in IETF, e.g., Multiprotocol Label Switching and Resource Reservation Protocol in terms of their impacts on supporting QoS in IP.
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