Data Communications II, Autumn 2004
Problem set 6
(3.11.2004) On Wednesday 8-10 in room ???
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How is a V.90 standard modem functioning? How is it possible to achieve 56
kbps rates, though the theoretical maximum for telephone network is only 35
kbps? And why is it only 56 kbps (or even less) and not 64 kbp? What is the modem V.92 that is now used in PC:s?
Information about V.90 and V.92 modems can be found in the Web e.g.
http://www.v90.com/whatis.htm
http://www.multitech.com/PRODUCTS/Info/qnas/Modems/v90.asp
http://www.techonline.com/community/ed_resource/feature_article/20022
http://www.v92.com/about/
- Token bucket
- A token bucket scheme is used for
traffic shaping. A new token is put into the bucket every 5
microsecond and one token allows the sending of one packet. What is
the maximum sending rate, when the maximum size of the packet is
1000 bits?
- A computer on a 6-Mbps network is regulated by a token
bucket. The token bucket is filled at a rate of 1 Mbps. It is
initially filled to capacity with 8 megabits. How long can the
computer transmit at the full 6 Mbps?
- Token bucket + leaky bucket
New tokens are generated at
the rate of 1000 tokens per second and each token allows the sending
of a packet. The maximum size of the packet sent is 1000 bytes. The
capacity of the token bucket is 2000 tokens. The maximum data rate
of the line is 10 MBps (B = byte). Anyhow a peak sending rate of 5
MBps has been agreed. What kind of leaky bucket is needed between
the token bucket and the network so that the agreed maximum sending
rate is not exceeded and all the data from the application can be
sent and nothing is lost in a buffer overflow?
-
The network below uses RSVP protocol and multicast trees to transmit video
flows to the receivers. Hosts 1 and 2 function as senders and 3,4 and 5as receivers.
The host 3 request a 2 MBps channel from the sender 1 and a 1 MBps channel
from the sender 2 because it wants watch both Formula Racing and Football Game.
The host 4 requests a 2 MBps channel from the sender 1 and host 5
requests a 1 MBps channel from the sender 2. How do these requests move in
the network and how much channel capasity is reserved in the routers a, ...f?
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There are proposals for two different ways to add quality of service to
Internet. Explain the most important features of these proposals. In your
opinion which of these ways seems to be the better way to add quality of
service to Internet?
Is it really necessary to add any Quality of Service at all to Internet?
Wouldn't it be enough just to put enough capacity and bandwidh
into the lines?
-
Your opinions about this course.
-
What
subjects were, in your opinion, the most interesting and important ones?
What subjects were dull and unnecessary?
- How should the course be changed in the
future? What should be more and what less? What missing subjects should be included? What items could be
dropped from the course?
-
Fill the
teaching evalution form for this course
(http://ilmo.cs.helsinki.fi/kurssit/servlet/Valinta?kieli=en).