Optical Networks - _10_1 Cost Trade-Offs_ A Detailed Ring Network Exam_117

Optical Networks - _10_1 Cost Trade-Offs_ A Detailed Ring Network Exam_117

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10.1 Cost Trade-Offs: A Detailed Ring Network Example 577 wavelengths to be provided on each link, in Section 10.3. We discuss statistical dimensioning methods in Section 10.4. In Section 10.5, we examine a number of re- search results that have been obtained regarding the trade-offs between OXCs with and without wavelength conversion capability. (We will discuss a practical long-haul network design example in Section 13.2.6.) 10.1 Cost Trade-Offs: A Detailed Ring Network Example In this section, we will study the cost trade-offs in designing networks in different ways to meet the same traffic demand by varying the lightpath topology. We will consider the trade-offs between the cost of the higher-layer equipment and the optical layer equipment. We measure the higher-layer equipment cost by the number of IP router ports (or SONET line terminals). The number of IP router ports required is equal to twice the number of lightpaths that need to be established since each light- path connects a pair of IP router ports. An important component of the optical layer cost is the number of transponders required in the OLTs and OADMs. Since every lightpath requires a pair of transponders, we club the cost of the transponders with that of the higher-layer equipment. This also covers the case where the transponders are present within the higher-layer equipment (see Figure 7.2). We measure the re- mainder of the cost of the optical layer equipment by the number of wavelengths used on a link. Network topologies are usually designed to be 2-connected, that is, to have two node-wise disjoint routes between every pair of nodes in the network. While fiber mesh topologies that are arbitrary, but 2-connected, are more cost-efficient for large networks than fiber ring topologies, the latter have been widely deployed and are good for a network that does not have a wide geographic spread. For this reason we will consider fiber ring topologies in this section. There is a wide deployment of rings in part because a ring connecting N nodes has the minimum possible number of links (only N ) for a network that is 2-connected, and thus tends to have a low fiber deployment cost. We will consider a traffic matrix where t units of traffic are to be routed from one IP router to all other IP routers in the network. We denote the number of nodes in the network by N and assume the traffic is uniform; that is, t/(N 1 ) units of traffic are to be routed between every pair of IP routers. For normalization purposes, the capacity of a wavelength is assumed to be one unit. As in the three-node linear topology above, we divide the network design problem into two: the LTD and RWA problems. We will consider three different lightpath topologies, all of which are capable of meeting the traffic requirements. The general form of these topologies is shown in Figure 10.3.
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578 WDM Network Design A A A B B B C C C Hub D D D (a) (b) (c) Figure 10.3 Three different lightpath topologies that can be deployed over a fiber ring topology. (a) A point-to-point WDM ring where adjacent routers on the ring are
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This note was uploaded on 01/15/2011 for the course ECE 6543 taught by Professor Boussert during the Spring '09 term at Georgia Institute of Technology.

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Optical Networks - _10_1 Cost Trade-Offs_ A Detailed Ring Network Exam_117

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