U
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U
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TO
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packet to the receiving host at time t1. At time t2 = t1 + L/R2, the router completes
transmission and the entire packet is received at the receiving host (again, no
propagation delay). Thus, the end-to-end delay is L/R1 + L/R2.
12. A circuit-switched network can guarantee a certain amount of end-to-end bandwidth
for the duration of a call. Most packet-switched networks today (including the Internet)
cannot make any end-to-end guarantees for bandwidth. FDM requires sophisticated
analog hardware to shift signal into appropriate frequency bands.
13. a) 2 users can be supported because each user requires half of the link bandwidth.
b) Since each user requires 1Mbps when transmitting, if two or fewer users transmit
simultaneously, a maximum of 2Mbps will be required. Since the available
TU
bandwidth of the shared link is 2Mbps, there will be no queuing delay before the
link. Whereas, if three users transmit simultaneously, the bandwidth required
will be 3Mbps which is more than the available bandwidth of the shared link. In
this case, there will be queuing delay before the link.
c) Probability that a given user is transmitting = 0.2
TO
d) Probability that all three users are transmitting simultaneously =
= (0.2)3 = 0.008. Since the queue grows when all the users are transmitting, the
fraction of time during which the queue grows (which is equal to the probability
that all three users are transmitting simultaneously) is 0.008.
R
14. If the two ISPs do not peer with each other, then when they send traffic to each other
they have to send the traffic through a provider ISP (intermediary), to which they have
to pay for carrying the traffic. By peering with each other directly, the two ISPs can
G
reduce their payments to their provider ISPs. An Internet Exchange Points (IXP)
(typically in a standalone building with its own switches) is a meeting point where
multiple ISPs can connect and/or peer together. An ISP earns its money by charging
U
each of the the ISPs that connect to the IXP a relatively small fee, which may depend
on the amount of traffic sent to or received from the IXP.
R
15. Google's private network connects together all its data centers, big and small. Traffic
between the Google data centers passes over its private network rather than over the
public Internet. Many of these data centers are located in, or close to, lower tier ISPs.
Therefore, when Google delivers content to a user, it often can bypass higher tier ISPs.
U
What motivates content providers to create these networks? First, the content provider
has more control over the user experience, since it has to use few intermediary ISPs.
Second, it can save money by sending less traffic into provider networks. Third, if ISPs
decide to charge more money to highly profitable content providers (in countries where
net neutrality doesn't apply), the content providers can avoid these extra payments.
16. The delay components are processing delays, transmission delays, propagation delays,
and queuing delays. All of these delays are fixed, except for the queuing delays, which
are variable.
oliuytrew
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U
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R
TO
TU
, U
R
U
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R
TO
TU
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R
U
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R
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, ikuytrew
packet to the receiving host at time t1. At time t2 = t1 + L/R2, the router completes
transmission and the entire packet is received at the receiving host (again, no
propagation delay). Thus, the end-to-end delay is L/R1 + L/R2.
12. A circuit-switched network can guarantee a certain amount of end-to-end bandwidth
for the duration of a call. Most packet-switched networks today (including the Internet)
cannot make any end-to-end guarantees for bandwidth. FDM requires sophisticated
analog hardware to shift signal into appropriate frequency bands.
13. a) 2 users can be supported because each user requires half of the link bandwidth.
b) Since each user requires 1Mbps when transmitting, if two or fewer users transmit
simultaneously, a maximum of 2Mbps will be required. Since the available
TU
bandwidth of the shared link is 2Mbps, there will be no queuing delay before the
link. Whereas, if three users transmit simultaneously, the bandwidth required
will be 3Mbps which is more than the available bandwidth of the shared link. In
this case, there will be queuing delay before the link.
c) Probability that a given user is transmitting = 0.2
TO
d) Probability that all three users are transmitting simultaneously =
= (0.2)3 = 0.008. Since the queue grows when all the users are transmitting, the
fraction of time during which the queue grows (which is equal to the probability
that all three users are transmitting simultaneously) is 0.008.
R
14. If the two ISPs do not peer with each other, then when they send traffic to each other
they have to send the traffic through a provider ISP (intermediary), to which they have
to pay for carrying the traffic. By peering with each other directly, the two ISPs can
G
reduce their payments to their provider ISPs. An Internet Exchange Points (IXP)
(typically in a standalone building with its own switches) is a meeting point where
multiple ISPs can connect and/or peer together. An ISP earns its money by charging
U
each of the the ISPs that connect to the IXP a relatively small fee, which may depend
on the amount of traffic sent to or received from the IXP.
R
15. Google's private network connects together all its data centers, big and small. Traffic
between the Google data centers passes over its private network rather than over the
public Internet. Many of these data centers are located in, or close to, lower tier ISPs.
Therefore, when Google delivers content to a user, it often can bypass higher tier ISPs.
U
What motivates content providers to create these networks? First, the content provider
has more control over the user experience, since it has to use few intermediary ISPs.
Second, it can save money by sending less traffic into provider networks. Third, if ISPs
decide to charge more money to highly profitable content providers (in countries where
net neutrality doesn't apply), the content providers can avoid these extra payments.
16. The delay components are processing delays, transmission delays, propagation delays,
and queuing delays. All of these delays are fixed, except for the queuing delays, which
are variable.
oliuytrew
