課程名稱︰高等計算機網路
課程性質︰系選修
課程教師︰逄愛君
開課學院：電資學院
開課系所︰資訊所
考試日期（年月日）︰2010/11/10
考試時限（分鐘）：180
是否需發放獎勵金：是
（如未明確表示，則不予發放）
1. Please elaborate on the relationship among SNR, BER and PHY. (5%)
2. Hidden Terminal: (15%)
A. What is "hidden terminal" problem? (5%)
B. How does 802.11 MAC solve the hidden terminal problem? (10%)
3. Please comment respectively on "Indirect Routing" and "Direct Routing" for
handling mobility over the Internet. (10%)
4. Multimedia Networking Application: (25%)
A. What are the chalenges for multimedia applications over the Internet?
(5%)
B. Please describe possible solutions to overcome the challenges. (10%)
C. Please describe how "adaptive playout delay" works for Internet
phone. (10%)
5. Consider the leaky bucket policer that polices the average rate and burst
size of a packet flow. We now want to police the peak rate, p as well.
Show how the output of this leaky bucket policer can be fed into a second
leaky bucket policer so that the two leaky buckets in series police the
average rate, peak rate, and burst size. Be sure to give bucket size and
token generation rate for the second policer. (10%)
6. Please compare the public-key and symmetric-key for network security. (5%)
7. Message Condifentiality, Message Integrity and Endpoint Authentication.
(20%)
A. Why do we need "message integrity" and "endpoint authentication" if we
already have "message confidentiality"? (5%)
B. What is "DIgital Signature"? Why do we have CA for "Digital Signature"?
(10%)
C. How to break the encryption fo 802.11 WEP? (5%)
8. Consider our authentication protocol ap4.0, in which Alice authenticates
herself to Bob, which we saw works well (i.e., we found no flaws in it).
Now suppose that while Alice is authenticating herself to Bob, Bob must
authenticate himself to Alice. Given a scenario by which Trudy, pretending
to be Alice, can now authenticate herself to Bob as Alice. (Hint: Consider
that the sequence of operations of ap4.0, one with Trudy initialing and one
with Bob initialing, can be arbitrarily interleaved. Pay particular
attention to the fact that both Bob and Alice will use a nonce, and that if
case is not taken, the same nonce can be used maliciously.) (10%)
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