Visvesvaraya Technological University (VTU) 2007 B.E Computer Science on mobile communications - Question Paper

situation on highways?
9. Mobile transport layer
9.1 Compare the various kinds of transmission errors that can occur in wireless and
wired networks. What additional role does mobility play?
9.2 What is the reaction of standard TCP in case of packet loss? In what situation does
this reaction make sense and why is it quite often problematic in the case of wireless
networks and mobility?
9.3 Can the issues using TCP be solved by replacing TCP with UDP? Where could
this be useful and why is it quite often dangerous for network stability?
9.4 How and why does I-TCP isolate issues on the wireless link? elaborate the main
drawbacks of this solution?
9.5 Show the interaction of mobile IP with standard TCP. Draw the packet flow from a
fixed host to a mobile host via a foreign agent. Then a handover takes place. What
are the subsequent actions of mobile IP and how does TCP react?
9.6 Now show the needed steps during handover for a solution with a PEP. elaborate the
state and function of foreign agents, home agents, correspondent host, mobile host,
PEP and care-of address before, during, and after handover? What info has
to be transferred to which entity in order to maintain consistency for the TCP
connection?
9.7 elaborate the influences of encryption on the proposed schemes? Consider for
example IP security that can encrypt the payload, i.e., the TCP packet.
9.8 Name further optimisations of TCP regarding the protocol overhead which are
important especially for narrow band connections. Which issues may occur?
9.9 presume a fixed Internet connection with a round trip time of 20 ms and an fault rate
of 10-10. compute the upper bound on TCP’s bandwidth for a maximum segment size
of 1000 byte. Now 2 various wireless access networks are added. A WLAN with 2
ms additional one-way delay and an fault rate of 10-3, and a GPRS network with an
additional RTT of two s and an fault rate of 10-7. Redo the computation ignoring the fixed
network’s fault rate. Compare these outcomes with the ones derived from the second
formula (use RTO = five RTT). Why are a few outcomes not realistic?
9.10 Why does the link speed not appear in the formulas presented to estimate TCP’s
throughput? What is wrong if the estimated bandwidth is higher than the link speed?
10. Support for mobility
10.1 Why is strong consistency of file systems problematic in a wireless and mobile
environment? elaborate the alternatives?
10.2 How do conventional file systems react to disconnected systems? Try unplugging a
computer that has mounted a file system via a network.
10.3 What advantages has the statelessness of HTTP? In what situations is state useful
and how is it given today? Where is long-term state stored, where short-term?
10.4 Which properties of HTTP waste bandwidth? What is the additional issue using
HTTP/1.0 together with TCP? How does HTTP/1.1 improve the situation?
10.5 How does caching improve access time and decrease bandwidth requirements? What
are locations for a cache and their specific advantages?
10.6 elaborate issues of caches in real life? What kind of content can be cached, which
content causes problems? elaborate the additional issues with client mobility?
10.7 What discrepancies exist ranging from the possibilities of HTML and the realities of
wireless handheld devices? elaborate proposed solutions? What is the role of plug-ins
today and how do they influence the usability of web pages?
10.8 Name mechanisms to improve web access for handheld devices. What is their
common issue and what led finally to the development of WAP?
10.9 elaborate typical enhancements to the basic client/server architecture of the web?
Reconsider these enhancements for a mobile wireless user with web access over a
mobile phone network. elaborate efficient locations for the enhancements?
10.10 elaborate the primary goals of the WAP Forum efforts and how are they reflected in
the initial WAP protocol architecture?
10.11 What migration paths does WAP 1.x offer for Internet and telephony applications and
their protocols? Compare with WAP 2.0.
10.12 Is WDP a fixed protocol and why does WAP not describe a SAP which WDP can use?
10.13 Why does WAP describe its own security layer and does not rely on the security
given by the mobile phone network? What issues does the WAP security layer
cause? Think of end-to-end security.
10.14 Name the advantages and disadvantages of user acknowledgements in WTP. What
are typical applications for both cases?
10.15 Which WTP class reflects the typical web access best? How is unnecessary
overhead avoided when using WSP on top of this class for web browsing?
10.16 What issues of HTTP can WSP solve? Why are these solutions especially needed
in wireless mobile environments?
10.17 Why does WSP/B not put responses into the identical order as the requests? Think, for
example, of requests for various items on a web page.
10.18 What advantages does a connectionless session service offer compared to a simple
datagram service?
10.19 elaborate the enhancements of WAE to the classic client/server model of the web?
elaborate functions of this enhancement?
10.20 What is the fundamental difference of WML compared to HTML? Why can this
difference be important with respect to handheld devices? What is specified in
addition to save bandwidth?
10.21 Why has a scripting language been added to WML? How can this language help
saving bandwidth and reducing delay?
10.22 elaborate typical telephony events and how are they integrated into WAP? How can a
user access features of mobile phones via the web browser?
10.23 What is the role of a WTA server? elaborate the various ways of integrating WTA
servers into the WAP architecture?
10.24 What is the difference ranging from WAP service indication and service loading? What
applications could use these services? What is a push good for anyway?
10.25 Name key differences ranging from WAP 1.x and i-mode. What were issues in the
early WAP days and why was i-mode that successful in Japan?
10.26 Why is a common synchronisation framework useful? What issues remain?
10.27 elaborate major differences ranging from WAP 2.0 and WAP 1.x? What influenced the
WAP 2.0 development?
10.28 Compare the presented protocol stacks for WAP 2.0 and provide application examples.

Earning:   Approval pending.