CS 118 Spring 2011 : Homework 6Figure 1: Network with edge weightsFigure 2: Fragment of network.Problem 1In this problem we’ll explore the impact of NATs on P2P applications. Suppose a peer with username Alicediscovers through querying that a peer with username Bob has a file it wants to download. Also supposethat Bob and Alice are both behind a NAT. Is it possible to devise a technique that will allow Alice toestablish a TCP connection with Bob without application-specific NAT configuration? Why or why not?Problem 2If you have a network that looks like Figure 1 and you use the link weights shown, use Dijkstra’s shortest-path algorithm to compute the shortest path from F to all network nodes. Show how the algorithm worksby computing a table like Table 4.3 (4th:page 373, 5th: page 379) in your book.Problem 3Using the network in Figure 2, x has only 2 attached neighbors, w and y. w has a minimum-cost path todestination u (not shown) of 5, and y has a minimum-cost path to u of 6. The complete paths from w andy to u (and between w and y) are not shown. All link costs in the network have strictly positive integervalues.a. Find x’s distance vector for destinations w, y, and u.b. Find a case of link-cost change (if any) for either c(x, w) or c(x, y) such that x will inform its neighborsof a new minimum-cost path to u as a result of executing the distance vector algorithm.Problem 3 continued on next page. . . Page 1 of 2CS 118 Spring 2011 : Homework 6c. Find a case of link-cost change (if any) for either c(x, w) or c(x, y) such that x will not inform itsneighbors of a new minimum-cost path to u as a result of executing the distance vector algorithm.Page 2 of
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