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Connection-oriented Networks: SONET/SDH, ATM, MPLS and Optical Networks

Harry G. Perros

Chapter 11

Access Networks - all with Video Answers

Educators

Chapter Questions

00:23

Problem 1

You have to download a 20-MB file to your computer at home.
a) How long does it take to download it assuming that you are connected with a $56 \mathrm{~K}$ modem, that gives a throughput of $49 \mathrm{Kbps}$ ?
b) How long does it take to download the same file assuming that your computer is connected to an ADSL modem, which provides a throughput of 1 Mbps?

Ashley High
Ashley High
Numerade Educator

Problem 2

What is the difference between the fast path and the interleaved path in an ADSL modem?

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Problem 3

What is the advantage of using the network access server (NAS)?

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Problem 4

In L2TP, why are control messages transmitted over a reliable channel and not data messages?

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02:40

Problem 5

Consider the pointer_field in an MPEG packet used in DOCSIS. What is its value for the following cases?
a) The first DOCSIS MAC frame starts immediately after the pointer field.
b) The first $M$ bytes after the pointer_field contain the tail of a DOCSIS MAC frame. Then, there are $B$ stuff-bytes, after which a new DOCSIS MAC frame begins.
c) A new DOCSIS MAC frame begins immediately after the pointer_field, followed by $B$ stuff-bytes, followed by another DOCSIS MAC frame.

Maxime Rossetti
Maxime Rossetti
Numerade Educator

Problem 6

Explain the difference between FTTH and FTTB/C.

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Problem 7

Explain how ranging is used in an APON to place each ONU at the same virtual distance.

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Problem 8

In an APON, explain how the round robin algorithm can be modified so that grant permits are handed out only to those ONUs that have an ATM cell to transmit.

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