2) (25 points) Consider downloading a file of size F bits…
2) (25 points) Consider downloading a file of size F bits from a server S to a client C. The server has an access link with transmission bit rate RS = 2R bit/s to the backbone of the Internet, while the client has access transmission bit rate RC = R. We model the backbone of the Internet with two links with transmission bit rates RB1 = 5R and RB2 = 10R that are interconnected with a router. Thus, there are total of two hosts (i.e., server, client), three routers (i.e., router between server access link and first backbone link, router between the two backbone links, and router between second backbone link and client access link), and four links in the considered network architecture and the file is transmitted from the server to the client as indicated by the direction of the arrows: Server => Access link RS = 2R bit/s => Backbone link RB1 = 5 R => Backbone link RB2 = 10 R => Access link RC = R => Client. The distances (lengths) of the access links of client and server are the same and are denoted by dA meters, the backbone links have length dB, dB > dA. Let s meters/second denote the propagation speed on the links. Assume that the routers interconnecting the links have unlimited buffer capacity and negligible nodal processing delay. There are no other traffic flows in the considered network. Drawing a labeled separate space-time diagram for each of the following parts a), b), and c) is required in order to receive credit. a) Suppose message switching is used, i.e., the entire file is treated as one large packet. How long does it take to download the file? b) Suppose the file is broken up into packets, each packet with P information bits (with F/P an integer), and packet switching is used. Header bits are negligible. How long does it take to download the file? c) Suppose circuit switching is used. The circuit that we set up across all the network links has a circuit transmission bit rate of R/2 bit/s. Assuming ts seconds set up time, how long does it take to download the file?