Optical Networks - _Problems9_123

# Optical Networks - _Problems9_123 - Problems 619 As...

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Problems 619 As mentioned in Section 10.2.2, there are two common methods for computing disjoint paths. One method ﬁrst computes a shortest path and then a second path that avoids the ﬁrst. Since there may be multiple shortest paths, multiple candidate disjoint paths can be computed and the best chosen from among them. Algorithms that solve the k shortest paths problem [Yen71] can be used to generate multiple candidate paths. The other method to compute disjoint paths is to use an algorithm that solves the minimum disjoint path problem [Suu74, ST84]. A reference that discusses disjoint paths when SRLGs are considered is [Bha99]. The statistical blocking model for dimensioning is analyzed in [SS00, BK95, RS95, KA96, SAS96, YLES96, BH96]. The worst-case analysis of the maximum load model with online trafﬁc is con- sidered in [GK97]. Problems 10.1 In general, there are several valid design options even for a three-node network. Consider the designs shown in Figure 10.1(c), but now assume that the number of dropped lightpaths is six instead of ﬁve as discussed in the text. The advantage of this design is that it provides more ﬂexibility in handling surges in A–B and B–C trafﬁc. For example, this design not only can handle the trafﬁc requirement of 50 Gb/s between every pair of nodes, it can also handle a trafﬁc requirement of 60 Gb/s between nodes A–B and B–C, and 40 Gb/s between nodes A–C. This latter trafﬁc pattern cannot be handled if only ﬁve lightpaths/wavelengths are dropped. Consider the design of Figure 10.1(c), and assume that x wavelengths are dropped at node B and y wavelengths pass through. Determine the range of trafﬁc matrices that this design is capable of handling as a function of x and y . 10.2 Consider the network design approach using ﬁxed-wavelength routing in a four-node ring network with consecutive nodes A, B, C, and D. Suppose the trafﬁc requirements are as follows: ABCD A –3–3 B 3–23 C –2–2 D 332– (a) Do a careful routing of trafﬁc onto each wavelength so as to minimize the number of wavelengths needed.

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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 - _Problems9_123 - Problems 619 As...

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