Consider a user who needs to transmit 1 . 5 gigabytes of data to a server. The
Question:
user lives in a small town where only dialup access is available. A bus visits
the small town once a day from the closest city, located km away, and stops
in front of the users house. The bus has a Mbps WiFi connection. It can
collect data from users in rural areas and transfer them to the Internet through a
Gbps link once it gets back to the city. Suppose the average speed of the bus is
kmh What is the fastest way the user can transfer the data to the server?
P Suppose two hosts, A and B are separated by kilometers and are con
nected by a direct link of R Mbps Suppose the propagation speed over
the link is #
meterssec
a Calculate the bandwidthdelay product, R # dprop
b Consider sending a file of bits from Host A to Host B Suppose
the file is sent continuously as one large message. What is the maximum
number of bits that will be in the link at any given time?
c Provide an interpretation of the bandwidthdelay product.
d What is the width in meters of a bit in the link? Is it longer than a
football field?
e Derive a general expression for the width of a bit in terms of the propaga
tion speed s the transmission rate R and the length of the link m
P Consider problem P but now with a link of R Gbps
a Calculate the bandwidthdelay product, R dprop
b Consider sending a file of bits from Host A to Host B Suppose
the file is sent continuously as one big message. What is the maximum
number of bits that will be in the link at any given time?
c What is the width in meters of a bit in the link?
P Consider the scenario illustrated in Figure a Assume Rs
is Mbps
Rc
is Mbps and the server is continuously sending traffic to the client.
Also assume the router between the server and the client can buffer at most
fourmessages After how many messages sent by the server will packet loss
starts occurring at the router?
P Generalize the result obtained in Problem P for the case where the router
can buffer m messages.
P Suppose there is a Mbps microwave link between a geostationary satellite
and its base station on Earth. Every minute the satellite takes a digital photo and
sends it to the base station. Assume a propagation speed of #
meterssec
a What is the propagation delay of the link?
b What is the bandwidthdelay product, R # dprop?
c Let x denote the size of the photo. What is the minimum value of x for the
microwave link to be continuously transmitting?
Computer Architecture Fundamentals And Principles Of Computer Design
ISBN: 9781032097336
2nd Edition
Authors: Joseph D. Dumas II